CN112502732A

CN112502732A - Construction method of shield tunnel of water-rich sand layer

Info

Publication number: CN112502732A
Application number: CN202011375254.3A
Authority: CN
Inventors: 谢江胜; 任少强; 樊小林; 杨星智; 王存宝
Original assignee: China Railway 20th Bureau Group Corp
Current assignee: China Railway 20th Bureau Group Corp
Priority date: 2020-11-30
Filing date: 2020-11-30
Publication date: 2021-03-16
Anticipated expiration: 2040-11-30
Also published as: CN112502732B

Abstract

The invention discloses a construction method of a shield tunnel of a water-rich sand layer, wherein the constructed tunnel is a double-hole tunnel and is an undercut tunnel with a tunnel body positioned in the water-rich sand layer, the constructed tunnel comprises a lower-penetrating tunnel section and three non-lower-penetrating tunnel sections, the lower-penetrating tunnel section penetrates through an existing viaduct, shield construction is carried out after isolation and reinforcement of the lower-penetrating tunnel section, precipitation is not needed, and shield construction is carried out after precipitation of the non-lower-penetrating tunnel sections. The shield tunnel is divided into the underpass tunnel section and the non-underpass tunnel section according to whether the underpass viaduct is constructed or not, and the non-underpass tunnel section is directly constructed after precipitation; the lower tunnel section is isolated and reinforced to form a slurry consolidation body, so that the shield machine can tunnel in the slurry consolidation body for construction, and soil disturbance and stratum pressure caused by tunneling of the shield machine during construction are resisted through the slurry consolidation body; and the two sides of the slurry consolidation body are respectively provided with the separation walls, so that the formation pressure can be completely blocked, and the safety and zero settlement of the viaduct on the upper side of the underpass tunnel section are ensured.

Description

Construction method of shield tunnel of water-rich sand layer

Technical Field

The invention belongs to the technical field of shield tunnel construction, and particularly relates to a shield tunnel construction method for a water-rich sand layer.

Background

With the large-scale construction of urban rail transit in China, the utilization rate of urban underground space is gradually increased, urban subways inevitably pass through the existing buildings or viaduct foundations, and the problems of protection and reinforcement of the existing buildings and viaduct foundations are certainly brought. Particularly, when a tunnel is constructed in a water-rich sand layer with strong water-rich property, loose structure and poor bonding capability, a tunnel construction area during tunneling of a tunnel shield machine belongs to a strong influence area for buildings and viaducts, the water-rich sand layer has extremely high compressibility, poor self-stability and low bearing capacity, so that disastrous accidents such as collapse and collapse of the sand collapse of the shield tunnel are easily induced in the tunneling process of the shield machine, the tunnel excavation safety is seriously threatened, soil disturbance caused in the tunneling process of the shield machine generates pressure on surrounding strata, the pressure is conducted to the periphery, the conduction speed is high, the conduction range is wide, the original relative stable or balanced state of the strata is easily damaged when a cutter head of the shield machine rotates and cuts, the transverse acting force on pile foundations of the existing viaduct is too large, and the safety of the shield machine and the existing viaducts is endangered.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a shield tunnel construction method for a water-rich sand layer aiming at the defects in the prior art, which has the advantages of reasonable design, simple and convenient construction and good use effect, wherein the shield tunnel is divided into a downward-passing tunnel section and a non-downward-passing tunnel section according to whether a downward-passing viaduct is used or not, and the non-downward-passing tunnel section is directly constructed after precipitation; before the construction of the underpass tunnel section, a slurry consolidation body is formed by isolating and reinforcing the stratum so that the shield machine performs tunneling construction on the slurry consolidation body, and soil disturbance and stratum pressure caused by tunneling of the shield machine during the construction of the underpass tunnel section are resisted by the slurry consolidation body; and the two sides of the slurry consolidation body are respectively provided with the isolation piles, so that the formation pressure can be completely blocked, and the safety and zero settlement of the viaduct on the upper side of the underpass tunnel section are ensured.

In order to solve the technical problems, the invention adopts the technical scheme that: a shield tunnel construction method for a water-rich sand layer is characterized by comprising the following steps: the constructed tunnel is a double-hole tunnel and is an underground excavation tunnel with a tunnel body positioned in the water-rich sand layer, and two tunnel holes of the constructed tunnel are both shield tunnels; the constructed tunnel comprises a lower-passing viaduct tunnel section and a non-lower-passing viaduct tunnel section connected with the lower-passing viaduct tunnel section, wherein one tunnel hole of the lower-passing viaduct tunnel section passes through an existing viaduct and is a lower-passing tunnel section, and two tunnel holes of the non-lower-passing viaduct tunnel section are communicated through a communication channel;

when the constructed tunnel is constructed, respectively constructing two tunnel holes of the underpass viaduct tunnel section and two tunnel holes of the non-underpass viaduct tunnel section; the other tunnel hole of the underpass viaduct section and the two tunnel holes of the non-underpass viaduct section are non-underpass tunnel sections, and the construction methods of the other tunnel hole of the underpass viaduct section and the two tunnel holes of the non-underpass viaduct section are the same;

when the underpass tunnel section is constructed, firstly, isolating and reinforcing the stratum of a construction area where the underpass tunnel section is located, and obtaining an isolation and reinforcement structure; after the construction of the isolation and reinforcement structure is completed, performing shield construction on the underpass tunnel section;

the isolation and reinforcement structure comprises two isolation walls which are respectively arranged at the left side and the right side of the underpass tunnel section and a slurry consolidation body which is formed by adopting sleeve valve pipes to carry out grouting reinforcement on a stratum to be reinforced and positioned between the two isolation walls, the underpass tunnel section is positioned in the slurry consolidation body, and the slurry consolidation body is fixedly connected with the two isolation walls into a whole; each partition wall is provided with a crown beam, each partition wall is fixedly connected with the crown beam arranged on the partition wall into a whole, and the two crown beams are fixedly connected into a whole through a plurality of cross beams from back to front; the top beam and the cross beam are both cast-in-place reinforced concrete beams, and the slurry consolidation body, the two partition walls and each top beam are all arranged along the longitudinal extension direction of the underpass tunnel section;

each isolation wall comprises a plurality of isolation piles which are vertically arranged, and each isolation pile is a reinforced concrete cast-in-place pile; the plurality of isolation piles in each isolation wall are arranged from back to front along the longitudinal extension direction of the underpass tunnel section, the front and rear adjacent isolation piles in each isolation wall are fixedly connected into a whole through grouting reinforcement bodies, and each grouting reinforcement body is a reinforcement structure formed by adopting sleeve valve pipes to perform grouting reinforcement on the stratum between the front and rear adjacent isolation piles;

when the non-underpass tunnel section is constructed, precipitation is carried out on the stratum of the construction area where the non-underpass tunnel section is located, and then shield construction is carried out on the non-underpass tunnel section.

The shield tunnel construction method for the water-rich sand layer is characterized by comprising the following steps: before the stratum of the construction area where the non-underpass tunnel section is located is subjected to precipitation, the stratum of the construction area where the non-underpass tunnel section is located is pre-reinforced by the sleeve valve pipes, a plurality of grouting holes for grouting the sleeve valve pipes are formed in the stratum of the construction area where the non-underpass tunnel section is located, and the plurality of grouting holes are vertically arranged and arranged in a quincunx shape.

The shield tunnel construction method for the water-rich sand layer is characterized by comprising the following steps: when the stratum of the construction area where the underpass tunnel section is located is isolated and reinforced, the method comprises the following steps:

step A1, measuring and setting out: according to a tunnel central line of the lower tunnel section which is designed in advance, measuring and paying off are carried out on the lower tunnel section, and measuring and paying off are carried out on the two partition walls respectively;

step A2, constructing the partition wall: respectively constructing the two partition walls, wherein the construction methods of the two partition walls are the same;

when any one partition wall is constructed, constructing a plurality of partition piles in the partition wall respectively, grouting and reinforcing stratums between front and rear adjacent partition piles which are constructed in the partition wall by sleeve valve pipes respectively to obtain a grouting reinforcement body which is formed by construction, and obtaining the partition wall which is formed by construction after all the partition piles and all the grouting reinforcement bodies in the partition wall are constructed;

step A3, crown beam construction: constructing a crown beam on each of the two partition walls constructed and formed in the step A2;

step A4, grouting and reinforcing the stratum to be isolated and reinforced: grouting and reinforcing the stratum to be isolated and reinforced between the two isolation walls by using sleeve valve pipes to obtain a slurry solidification body formed by construction, and tightly connecting the slurry solidification body between the two isolation walls formed by construction in the step A2;

step A5, beam construction: and B, constructing a plurality of beams above the slurry solidification body constructed and formed in the step A4, and enabling each beam to be tightly connected between two crown beams.

The shield tunnel construction method for the water-rich sand layer is characterized by comprising the following steps: when the non-underpassing viaduct tunnel section is constructed, after the two tunnel holes of the non-underpassing viaduct tunnel section are constructed, constructing a connecting channel;

the constructed connecting channel is an underground excavation tunnel which is connected between the two shield tunnels and the tunnel body of the underground excavation tunnel is positioned in the water-rich sand layer, and the constructed connecting channel is divided into a tunnel mouth section and a front side tunnel section which is positioned on the front side of the tunnel mouth section;

when the constructed connection channel is constructed, the method comprises the following steps:

step B1, erecting a temporary support structure of the duct piece: respectively erecting a group of segment temporary support structures in the two shield tunnels, and respectively positioning the two groups of segment temporary support structures at the front side and the rear side of the constructed connection channel;

the segment temporary supporting structure is erected on the inner side of a shield segment ring in the shield tunnel;

step B2, pre-reinforcing the stratum: pre-reinforcing the stratum where the constructed connecting channel is located, wherein the process is as follows:

step B21, grouting and reinforcing the stratum at the end part of the channel: respectively carrying out advanced small conduit grouting reinforcement on the stratums at the front end and the rear end of the constructed connection channel through the two shield tunnels, and forming a channel end stratum reinforcing structure on the outer sides of the two shield tunnels;

step B22, grouting and reinforcing the whole channel stratum: sleeve valve pipe grouting reinforcement is respectively carried out on the whole stratum where the constructed connection channel is located through the two shield tunnels to obtain a sleeve valve pipe grouting reinforcement structure;

the two passage end stratum reinforcing structures constructed in the step B21 are grouting stopping structures used for grouting reinforcement of sleeve valve pipes in the step, and the sleeve valve pipe grouting reinforcing structures and the two passage end stratum reinforcing structures are fixedly connected into a whole;

step B3, precipitation construction: lowering the water level of the stratum where the constructed connection channel is located to be below the excavation contour line of the constructed connection channel;

step B4, cutting and removing the pipe piece: cutting and dismantling a shield pipe sheet ring at the position where the constructed connection channel enters the tunnel in the shield tunnel to obtain a tunnel portal of the constructed connection channel;

step B5, channel opening section excavation and primary support construction: excavating the hole section of the constructed communication channel from back to front through the hole door in the step B4; in the excavation process, primary support is synchronously carried out from back to front;

step B6, excavation of the front side tunnel section and primary support construction: excavating the front side tunnel section of the constructed connection channel from back to front; and in the excavation process, the front side tunnel section formed by excavation is synchronously supported from back to front.

The shield tunnel construction method for the water-rich sand layer is characterized by comprising the following steps: after the formation pre-reinforcement in the step B2 is completed and before precipitation construction is carried out in the step B3, a vertical transportation channel is constructed at the rear end of the front side tunnel section from the ground from top to bottom, and the vertical transportation channel is communicated with the interior of the constructed connection channel;

b5, after excavating the opening section from back to front, the opening section is communicated with the vertical transportation channel;

when the front side tunnel section is excavated and preliminary bracing construction is carried out in the step B6, the front side tunnel section is excavated from back to front by using the vertical transportation channel, and the front side tunnel section is preliminary braced from back to front by using the vertical transportation channel.

The shield tunnel construction method for the water-rich sand layer is characterized by comprising the following steps: when grouting and reinforcing the stratum at the end part of the channel in the step B21, respectively drilling a group of advanced small guide pipes to the stratums at the front end and the rear end of the constructed connection channel through the two shield tunnels, wherein the two groups of advanced small guide pipes are symmetrically distributed; grouting and reinforcing the stratums at the front end and the rear end of the constructed connection channel through the two groups of small advanced guide pipes respectively;

each group of the small advanced ducts comprises a plurality of small advanced ducts which are uniformly distributed on the same plane, and the small advanced ducts in each group of the small advanced ducts are distributed from left to right along the width direction of the constructed connecting channel and are all distributed in parallel; each small advanced guide pipe is arranged along the longitudinal extension direction of the constructed connecting channel, one end of each small advanced guide pipe is a stratum driving end which is driven into the stratum, and the other end of each small advanced guide pipe is a grouting end; each small leading guide pipe is gradually inclined upwards from the grouting end to the stratum driving end.

The shield tunnel construction method for the water-rich sand layer is characterized by comprising the following steps: after the whole grouting reinforcement of the channel stratum in the step B22 is completed, supplementary grouting reinforcement is carried out on the stratum at the front end and the rear end of the constructed connection channel through the small advanced guide pipes arranged in the step B21 to obtain a grouting reinforcement structure of the stratum at the end part of the channel, and the grouting reinforcement structure of the stratum at the end part of the channel and the grouting reinforcement structure of the sleeve valve pipe in the step B22 are fixedly connected into a whole;

and when the supplementary grouting reinforcement is actually carried out, the supplementary grouting reinforcement is respectively carried out on the strata at the front end and the rear end of the constructed connection channel through the two groups of small advanced guide pipes.

The shield tunnel construction method for the water-rich sand layer is characterized by comprising the following steps: the leading small guide pipe arranged in the step B21 is a grouting pipe which is driven into the stratum through a pipe piece hoisting hole on a shield pipe piece ring in the shield tunnel.

The shield tunnel construction method for the water-rich sand layer is characterized by comprising the following steps: before sleeve valve pipe grouting reinforcement in the step B22, constructing a front sleeve valve pipe grouting structure and a rear sleeve valve pipe grouting structure respectively through two shield tunnels, wherein the two sleeve valve pipe grouting structures are symmetrically arranged and are both grouting reinforcement structures for integrally reinforcing a stratum to be reinforced; each sleeve valve pipe grouting structure comprises a plurality of sleeve valve pipes for channel reinforcement, which are driven into a to-be-reinforced stratum from the same shield tunnel, and the plurality of sleeve valve pipes for channel reinforcement in each sleeve valve pipe grouting structure are radially distributed; the stratum to be reinforced is a stratum within the range of L meters outside the excavation contour line of the constructed connecting channel, wherein the value range of L is 2.5-3.5;

each sleeve valve pipe for channel reinforcement in one sleeve valve pipe grouting structure is crossed with at least one sleeve valve pipe for channel reinforcement in the other sleeve valve pipe grouting structure.

The shield tunnel construction method for the water-rich sand layer is characterized by comprising the following steps: the stratum to be reinforced is divided into an overlapping reinforced area, an outer side grouting weak area positioned outside the overlapping reinforced area and two end part grouting weak areas respectively positioned on the front side and the rear side of the overlapping reinforced area, wherein the overlapping reinforced area is an area where the grouting areas of the two sleeve valve pipe grouting structures are overlapped;

the two end grouting weak areas are respectively positioned above the front end and the rear end of the overlapped reinforced area, and the small advanced guide pipe arranged in the step B21 is positioned in the end grouting weak area; the two end grouting weak areas are advanced small guide pipe grouting reinforcement areas reinforced by advanced small guide pipes, and the overlapping reinforcement area and the two end grouting weak areas form a core reinforcement area;

the stratum where the constructed connecting channel body is located in the core reinforcing area.

Compared with the prior art, the invention has the following advantages:

1. the method has the advantages of simple steps, simple and convenient construction, high construction efficiency and less input of manpower and material resources.

2. The reinforcement is kept apart earlier before the tunnel segment shield of wearing down, keeps apart the stagnant water to the bridge pile foundation of wearing tunnel segment and overpass down through setting up at rich water sand bed and keep apart reinforced structure, avoids using the precipitation well to carry out precipitation to the tunnel segment of wearing down at rich water sand bed and leads to the bridge pile foundation of overpass to take place to subside, and the security is good.

3. When isolation and reinforcement are actually carried out, the shield machine is driven to carry out driving construction on the slurry solidification body to form a downward-penetrating tunnel section by arranging the slurry solidification body, the slurry solidification body is a mixture of slurry injected into the sleeve valve pipe and peripheral soil bodies and is not a pure cement slurry liquid pile formed by pure cement slurry liquid injection, the strength of the slurry solidification body is smaller than that of pure cement slurry, and driving of the shield machine cannot be influenced when the downward-penetrating tunnel section is constructed; meanwhile, the strength of the mud consolidation body is far greater than that of the surrounding soil body, and the mud consolidation body can resist more stratum pressure than the soil body, so that the soil body disturbance and the stratum pressure caused by the tunneling of a shield tunneling machine during the construction of a tunnel section is eliminated. Meanwhile, the two sides of the slurry consolidation body are respectively provided with the isolation walls to resist soil disturbance and formation pressure which cannot be eliminated by the slurry consolidation body, and the safety and zero settlement of the viaduct on the upper side of the underpass tunnel section are ensured. The adopted isolation piles are small-diameter reinforced concrete cast-in-place piles, pile bodies of the small-diameter reinforced concrete cast-in-place piles are more sensitive to the deformation of the stratum, and when the stratum generates smaller deformation, the small-diameter pile bodies can simultaneously resist tension, compression, shearing, torsion and bending with the stratum, so that the material performance of the reinforced concrete cast-in-place piles is easier to exert.

4. The isolation and reinforcement construction method has wide application range, is not only suitable for the isolation and reinforcement construction process of the shield tunnel passing through the viaduct, but also suitable for the isolation and reinforcement construction in the stratum below various buildings.

5. The adopted construction method of the communication channel has the advantages of simple steps, reasonable design, simple and convenient construction and lower input cost.

6. The method for reinforcing the end stratum by using the advanced small conduit grouting for the pre-reinforcing of the connection channel stratum is simple and convenient to construct, the grouting process is easy to control, the reinforcing effect is good, the advanced small conduit grouting for reinforcing the end stratum is simple and convenient to arrange and good in reinforcing effect, a grout stop ring with a stable structure is formed before the connection channel stratum is integrally reinforced, the end stratum of the connection channel can be effectively reinforced, and meanwhile, the end stratum grouting reinforcement and the sleeve valve pipe grouting reinforcement complement each other, so that the final reinforcing effect of the connection channel stratum can be effectively enhanced; moreover, the shield tunnel can be effectively reinforced from the outer side through end stratum grouting reinforcement, and the reinforcement quality and the connection effect of the joint of the shield tunnel and the connection channel can be ensured; in addition, the connection channel stratum reinforcing structure and the shield tunnels at two ends can be firmly connected into a whole through end stratum grouting reinforcement, so that the overall reinforcing effect of the shield tunnel and the connection channel is further ensured, and the overall stability of the shield tunnel can be improved. According to the invention, the stratum reinforcing structures at the end parts of the channels are arranged to symmetrically reinforce the stratums at the front end and the rear end of the constructed connection channel, and the stratum reinforcing structures at the end parts of the two channels form two symmetrical grout stopping rings, so that the backflow of grout in the whole grouting, reinforcing and grouting process of the stratum of the channel can be prevented, the underground water flow to the front end and the rear end of the constructed connection channel can be effectively cut off, the structural stability of the joint between the constructed connection channel and the two shield tunnels is ensured, and the construction safety is ensured.

7. The sleeve valve pipe grouting reinforcement structure adopted for pre-reinforcing the stratum of the contact channel is simple and convenient to construct, the grouting process is easy to control, and the reinforcement effect is good, the sleeve valve pipe grouting reinforcement structure formed by construction integrally and effectively reinforces the stratum where the constructed contact channel is located, the purpose of reinforcing the stratum where the constructed contact channel is located in the whole range can be met by adopting a radial grouting reinforcement mode, and the integral reinforcement effect is very good; the arrangement distance of the advanced small pipes in the stratums at the two ends of the constructed connecting channel is smaller, so that the grouting density and the grouting reinforcement effect in the stratums at the two ends of the constructed connecting channel can be effectively ensured; although the arrangement distance of the advanced small pipes in the stratum in the middle of the constructed connecting channel is larger, the advanced small pipes on the front side and the rear side in the stratum in the middle of the constructed connecting channel are crossed, so that the grouting density and the grouting reinforcement effect in the stratum can be ensured.

8. When the contact passage stratum is consolidated in advance, consolidate the advanced little pipe slip casting of contact passage tip and combine together with contact passage stratum sleeve valve pipe monolithic reinforcement, the construction is simple and convenient and consolidate the quality and be convenient for control, the back is consolidated in the slip casting, stratum after consolidating is as an organic whole with the shield structure section of jurisdiction fixed connection who has been under construction in accomplishing the shield tunnel, when further improving the regional stratum consolidation effect of contact passage place of being under construction, can effectively improve the structure steadiness of shield tunnel, and can effectively restrict or even avoid the earth's surface of shield tunnel to subside. The pre-reinforcing stratum of the contact channel in the water-rich sand layer area is divided into a plurality of reinforcing areas, and different reinforcing methods are adopted for carrying out stratum pre-reinforcing construction on different reinforcing areas, so that the pre-reinforcing stratum of the contact channel is simply, quickly and reliably reinforced, a foundation is laid for the subsequent excavation of the contact channel, the collapse risk during the excavation of the contact channel is reduced, and the construction safety is ensured.

9. The adopted temporary duct piece supporting structure is reasonable in design, convenient to disassemble and assemble and good in reinforcing effect, occupies small space and can meet the construction requirement of track laying operation. The interim bearing structure of section of jurisdiction in the hole combines together with the passageway tip stratum reinforced structure in the shield tunnel outside, form effectual reinforcement support in the shield tunnel with the inside and outside both sides of the contact passageway linking department of being under construction, can prevent effectively that the prestressing force that portal department's section of jurisdiction trompil caused from concentrating and the section of jurisdiction deformation fracture that leads to is damaged, strengthen the bearing structure in section of jurisdiction outside simultaneously, inside and outside both sides are consolidated the bearing structure and are combined together, make the reinforcement effect of contact tunnel portal department shield section of jurisdiction better, it is safer to construct. When the current contact passageway construction that carries on, the section of jurisdiction supports and adopts door type support frame, reserves personnel, small-size machines or shield structure storage battery car and passes through the door opening, can't satisfy follow-up track laying engineering construction.

10. The adopted vertical transportation channel is simple in structure, reasonable in design, simple and convenient to construct and good in using effect, can accelerate the construction process of the contact channel, can avoid risks caused by the construction process of the contact channel in the shield tunnel in the process of laying the track and running the rail car, and is excavated into the hole 2m of the contact channel to be applied as the vertical transportation channel for earth external transportation and material hoisting.

11. The contact channel stratum pre-reinforcement method is reasonable in design, simple and convenient to construct and good in reinforcement effect, the advanced to-be-reinforced area of the contact channel stratum of the water-rich sand layer is divided, the grouting reinforcement method of the corresponding type is adopted for effective reinforcement, the reinforced stratum and the shield segment of the constructed shield tunnel are fixedly connected into a whole, the structural stability of the shield tunnel can be effectively improved while the reinforcement effect of the constructed contact channel stratum is further improved, the ground surface settlement of the shield tunnel can be effectively limited and even avoided, a foundation is laid for the contact channel excavation, the contact channel collapse risk is reduced, and the construction safety is guaranteed. And, before the stratum is consolidated in advance, erect section of jurisdiction temporary support structure in shield tunnel and contact passageway junction earlier, effectively consolidate in step shield tunnel and contact passageway junction stratum when the stratum is consolidated in advance, ensure the steadiness of shield tunnel and contact passageway junction to effectively reduce or even avoid the regional contact passageway of rich water sand layer shield to advance the hole construction risk.

12. The precipitation construction is carried out after the contact channel stratum is pre-consolidated, the stratum is further consolidated through precipitation, and because the stratum is pre-consolidated effectively, the later precipitation construction can not cause any adverse effect on the stability of the constructed shield tunnel.

13. The method for constructing the connection channel is simple in steps, reasonable in design, simple and convenient to construct and safe and reliable in construction process, a segment temporary supporting structure is erected at the joint of the shield tunnel and the connection channel before stratum pre-reinforcement, then stratum advance small guide pipe grouting reinforcement at the end part of the channel is combined with integral grouting reinforcement of a stratum sleeve valve pipe where the channel is located to perform stratum pre-reinforcement, after the stratum pre-reinforcement, a vertical transportation channel is constructed to carry out earth side transportation and material hoisting, the construction process of the connection channel between the water-rich sand layer shield sections can be simply and conveniently completed, and the construction process is safe and reliable. The tunnel segment is reinforced by grouting in the tunnel and supported by the annular segment, so that the safety of the formed tunnel segment in the tunnel portal breaking process is ensured, and the normal operation of track laying operation can be met; meanwhile, the construction task is completed safely and quickly by adding a temporary grid arch and vertical transportation measures in the excavation process. In addition, the connection channel construction process does not influence the subsequent construction process of the shield tunnel, the construction progress is not influenced, the construction period can be effectively guaranteed, and any adverse effect on the stability of the constructed shield tunnel structure is avoided.

In conclusion, the shield tunnel is divided into the underpass tunnel section and the non-underpass tunnel section according to whether the underpass viaduct is constructed conveniently and effectively, and the non-underpass tunnel section is directly constructed after precipitation; before the construction of the underpass tunnel section, a slurry consolidation body is formed by isolating and reinforcing the stratum so that the shield machine performs tunneling construction on the slurry consolidation body, and soil disturbance and stratum pressure caused by tunneling of the shield machine during the construction of the underpass tunnel section are resisted by the slurry consolidation body; and the two sides of the slurry consolidation body are respectively provided with the isolation piles, so that the formation pressure can be completely blocked, and the safety and zero settlement of the viaduct on the upper side of the underpass tunnel section are ensured.

The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.

Drawings

FIG. 1 is a flow chart of the construction method of the present invention.

FIG. 2 is a construction state diagram of the present invention for pre-consolidating the connection passage.

Fig. 3 is a schematic diagram of the arrangement positions of the advanced small guide pipes and the sleeve valve pipes on the cross section of the shield tunnel when the connection channel is pre-consolidated with the stratum.

FIG. 4 is a schematic diagram of the layout of the sleeve valve tube, the advanced ductule and the portal in the cross section of the communication channel according to the present invention.

Fig. 5 is a schematic view of a supporting state of the temporary segment support structure according to the present invention.

Fig. 6 is a schematic view of the construction state of the communication passage of the present invention.

FIG. 7 is a flow chart of a construction method of the communication channel of the present invention.

Fig. 8 is a schematic elevation view of the isolation and reinforcement structure of the present invention.

Fig. 9 is a schematic plan layout position diagram of the bridge pile foundation, the isolation pile, the side sleeve valve pipe and the middle sleeve valve pipe.

FIG. 10 is a schematic diagram showing the arrangement position of the cross section of the grouting pipe on the section of the connection passage hole of the present invention.

Description of reference numerals:

1-shield tunnel; 2-a communication channel; 3-a portal;

4-sleeve valve pipe for channel reinforcement; 5-the stratum to be consolidated; 6-overlapping the reinforced area;

7-grouting weak areas at the ends; 8-advanced small catheter; 9-grouting weak areas at the outer sides;

10-a telescopic connection; 11-a hinged seat; 12-arc shaped steel support

13-a support; 14-a screw jack; 15-grouting pipe;

16-steel arch centering; 17-vertical transport channels; 18-a steel casing;

19-primary tunnel supporting structure; 20-secondary lining of the tunnel;

21-bridge pile foundation; 22-a partition wall; 23-a slurry solidification body;

24-a crown beam; 25-a cross beam; 26-an isolation pile;

27-lateral sleeve valve tube; 29-middle sleeve valve tube.

Detailed Description

As shown in fig. 1, in the method for constructing a shield tunnel in a water-rich sand layer, the constructed tunnel is a double-hole tunnel and is an undercut tunnel with a hole body located in the water-rich sand layer, and two tunnel holes of the constructed tunnel are both a shield tunnel 1; the constructed tunnel comprises a lower viaduct tunnel section and a non-lower viaduct tunnel section connected with the lower viaduct tunnel section, wherein one tunnel hole of the lower viaduct tunnel section is provided with a lower viaduct and is a lower viaduct section, and two tunnel holes of the non-lower viaduct tunnel section are communicated through a communication channel 2, which is shown in detail in figure 2;

with reference to fig. 8 and 9, the isolation and reinforcement structure includes two separation walls 22 respectively disposed at the left and right sides of the underpass tunnel segment and a slurry solidification body 23 formed by using sleeve valve pipes to perform grouting reinforcement on the stratum to be reinforced between the two separation walls 22, the underpass tunnel segment is located in the slurry solidification body 23, and the slurry solidification body 23 is fastened and connected with the two separation walls 22 into a whole; each partition wall 22 is provided with a crown beam 24, each partition wall 22 is fastened and connected with the crown beam 24 arranged on the partition wall into a whole, and the two crown beams 24 are fastened and connected into a whole through a plurality of cross beams 25 from back to front; the crown beams 24 and the cross beams 25 are cast-in-place reinforced concrete beams, and the slurry consolidation body 23, the two partition walls 22 and each crown beam 24 are all arranged along the longitudinal extension direction of the underpass tunnel section;

each partition wall 22 comprises a plurality of partition piles 26 which are vertically arranged, and each partition pile 26 is a reinforced concrete cast-in-place pile; the plurality of the isolation piles 26 in each isolation wall 22 are arranged from back to front along the longitudinal extension direction of the underpass tunnel section, the front and rear adjacent isolation piles 26 in each isolation wall 22 are fixedly connected into a whole through grouting reinforcement bodies, and the grouting reinforcement bodies are reinforcement structures formed by adopting sleeve valve pipes to perform grouting reinforcement on the stratum between the front and rear adjacent isolation piles 26;

In this embodiment, before the stratum of the construction area where the non-underpass tunnel section is located is subjected to precipitation, the stratum of the construction area where the non-underpass tunnel section is located is pre-reinforced by the sleeve valve pipes, the stratum of the construction area where the non-underpass tunnel section is located is provided with a plurality of grouting holes for grouting the sleeve valve pipes, and the plurality of grouting holes are vertically arranged and arranged in a quincunx shape.

During actual construction, when the stratum of the construction area where the non-underpass tunnel section is located is subjected to precipitation, precipitation is carried out through two rows of precipitation wells which are respectively arranged on the left side and the right side of the stratum of the construction area where the non-underpass tunnel section is located.

As shown in fig. 1, when isolating and reinforcing the stratum of the construction area where the underpass tunnel segment is located, the method comprises the following steps:

step A1, measuring and setting out: according to the tunnel center line of the lower tunnel section which is designed in advance, measuring and paying off are carried out on the lower tunnel section, and measuring and paying off are respectively carried out on the two partition walls 22;

step A2, constructing the partition wall: the two partition walls 22 are constructed respectively, and the construction methods of the two partition walls 22 are the same;

when any one of the partition walls 22 is constructed, firstly, constructing a plurality of the partition piles 26 in the partition wall 22 respectively, and grouting and reinforcing the stratum between the front and rear adjacent partition piles 26 which are constructed in the partition wall 22 by using sleeve valve pipes respectively to obtain the grouting and reinforcing bodies which are formed by construction, and obtaining the partition wall 22 which is formed by construction after all the partition piles 26 and all the grouting and reinforcing bodies in the partition wall 22 are constructed;

step A3, crown beam construction: constructing a crown beam 24 on each of the two partition walls 22 constructed and formed in the step A2;

step A4, grouting and reinforcing the stratum to be isolated and reinforced: grouting and reinforcing the stratum to be isolated and reinforced between the two isolation walls 22 by using sleeve valve pipes to obtain a slurry solidification body 23 formed by construction, and firmly connecting the slurry solidification body 23 between the two isolation walls 22 formed by construction in the step A2;

step A5, beam construction: and constructing a plurality of beams 25 above the slurry solidified body 23 constructed and formed in the step A4, and enabling each beam 25 to be tightly connected between two crown beams 24.

In this embodiment, the stratum to be isolated and consolidated is a stratum of a construction area where the underpass tunnel section is located, and the viaduct is an existing viaduct; wherein, the existing viaduct refers to a constructed viaduct.

In this embodiment, two of the partition walls 22 are arranged in parallel. Each of the partition walls 22 has the same shape as the crown beam 24 provided thereon, and each of the partition walls 22 has the same longitudinal length as the crown beam 24 provided thereon.

In this embodiment, the upper surfaces of the plurality of isolation piles 26 in each isolation wall 22 are fastened and connected to the lower surface of the crown beam 24 disposed on each isolation wall 22, the upper surfaces of the two crown beams 24 and the plurality of cross beams 25 are flush with the ground at the positions where the two crown beams 24 and the plurality of cross beams 25 are located, and the upper surface of the stratum to be isolated and reinforced is located below the crown beam 24.

In this embodiment, the plurality of beams 25 are all horizontally arranged, and the plurality of beams are fastened and connected as a whole.

In this embodiment, the underpass tunnel section is horizontally arranged, the two crown beams 24 are horizontally arranged, and the reinforcement cage in each cross beam 25 is fastened and connected with the reinforcement cage in the two crown beams 24 into a whole.

During actual construction, soil disturbance and water loss in soil around the underpass tunnel segment can be caused during tunneling of the shield tunneling machine, and the pressure generated to the stratum around the underpass tunnel section, the soil disturbance and the water loss caused by the tunneling of the shield machine can cause the disturbance and the settlement to the bridge pile foundation 21 of the viaduct, therefore, before the underpass tunnel section is constructed, the slurry consolidation body 23 is arranged to lead the shield machine to tunnel in the slurry consolidation body 23 to form the underpass tunnel section, the slurry solidification body 23 is arranged to enable the shield tunneling machine to perform tunneling construction on the slurry solidification body 23 to form the underpass tunnel section, the cross sectional area of the slurry solidification body 23 is larger than that of the underpass tunnel section, the slurry solidification body 23 can effectively resist soil disturbance and formation pressure caused by tunneling of the shield tunneling machine, and the disturbance of the bridge pile foundation 21 caused by the soil disturbance and irregular diffusion of the formation pressure to the periphery caused by tunneling of the shield tunneling machine is avoided; meanwhile, the slurry consolidation body 23 isolates the underpass tunnel section from the bridge pile foundation 21, and the shield machine performs shield construction in the slurry consolidation body 23, so that water and soil loss caused by shield construction of the shield machine in a water-rich sand layer is avoided, and the bridge pile foundation 21 is ensured not to be settled; the isolation walls 22 are respectively arranged on the left side and the right side of the slurry solidification body 23, so that soil disturbance and formation pressure which cannot be eliminated by the slurry solidification body 23 are resisted, and safety and zero settlement of the viaduct on the upper side of the underpass tunnel section are ensured; the integrity of the two partition walls 22 is enhanced by arranging the crown beams 24 at the tops of the two partition walls 22 respectively, and the two crown beams 24 are connected into a whole in a fastening manner through the plurality of cross beams, so that the integrity and the position accuracy of the whole isolation and reinforcement structure are enhanced, the reinforcement effect is good, and the deviation of the position of the partition wall 22 caused by soil disturbance and formation pressure during the tunneling of the shield tunneling machine is avoided.

In this embodiment, the grout injected into the middle sleeve valve pipe 29 is 42.5-grade ordinary portland cement grout, the mud consolidation body 23 is a mixture of the grout injected into the middle sleeve valve pipe 29 and the soil around the arrangement position of the middle sleeve valve pipe 29, and is not a pure cement mud liquid pile formed by pure cement mud liquid grouting, the strength of the mud consolidation body 23 is less than that of the pure cement grout, but is greater than that of the soil around the mud consolidation body, and because the strength of the mud consolidation body 23 is less than that of the pure cement grout, the mud consolidation body 23 does not affect the driving of the shield machine during the construction of the underpass tunnel section, and because the strength of the mud consolidation body 23 is greater than that of the soil around the mud consolidation body, the mud consolidation body 23 can withstand more formation pressure than the soil.

In this embodiment, the cross section of the to-be-isolated and reinforced stratum is rectangular and is arranged along the longitudinal extension direction of the underpass tunnel section, the upper surface of the to-be-isolated and reinforced stratum is higher than the vault of the underpass tunnel section, the clear distance h1 between the two is not less than 2m, the bottom surface of the to-be-isolated and reinforced stratum is located below the underpass tunnel section, the clear distance h2 between the two is not less than 1.5m, the bottom surface of the to-be-isolated and reinforced stratum is located above the bottom surface of the partition wall 22, and the vertical distance between the two is 2m to 3 m.

In this embodiment, incomplete grouting is adopted for all the middle sleeve valve pipes 29 to form the slurry solidification body 23, the upper surface of the slurry solidification body 23 is higher than the vault of the underpass tunnel section, the clear distance between the two is not less than 2m, the bottom of the slurry solidification body 23 is located below the underpass tunnel section, the clear distance between the two is not less than 1.5m, the construction speed is improved by adopting incomplete grouting for the middle sleeve valve pipes 29, and the cost is saved.

In this embodiment, the stratum to be isolated and consolidated is located between two bridge pile foundations 21 of the viaduct, and the two bridge pile foundations 21 are located on the left side and the right side of the stratum to be isolated and consolidated respectively;

when the clear distance between the underpass tunnel section and the two bridge pile foundations 21 is not less than d1, the value range of h1 is 2 m-2.2 m, and the value range of h2 is 2 m-2.2 m; wherein d1 is a preset determination threshold value of the clear distance between the underpass tunnel section and the bridge pile foundation 21, and the value range of d1 is 5 m-7 m;

when the clear distance between the lower tunnel section and any one of the bridge pile foundations 21 is smaller than d1, the value range of h1 is 3 m-3.2 m, and the value range of h2 is 2 m-2.2 m.

In this embodiment, the net distance between the underpass tunnel section and the bridge pile foundation 21 refers to the minimum net distance between the underpass tunnel section and the bridge pile foundation 21 in the horizontal direction.

In this embodiment, d1 is 6m, in the actual construction process, the value of d1 can be adjusted correspondingly according to specific needs, and when the value of d1 is adjusted, the larger the water content of the stratum to be isolated and reinforced is, the smaller the value of d1 is; conversely, the smaller the water content of the stratum to be isolated and consolidated is, the larger the value of d1 is.

In this embodiment, the front end surface of the stratum to be isolated and reinforced and the front end surfaces of the two isolation walls 22 are both located on the same tunnel cross section of the underpass tunnel section, and the rear end surface of the stratum to be isolated and reinforced and the rear end surfaces of the two isolation walls 22 are both located on the same tunnel cross section of the underpass tunnel section;

the front end surface of the stratum to be isolated and consolidated is positioned in front of the viaduct, and the rear end surface of the stratum to be isolated and consolidated is positioned behind the viaduct; the clear distance between the front end face of the stratum to be isolated and reinforced and the two bridge pile foundations 21 is not less than d2, and the clear distance between the rear end face of the stratum to be isolated and reinforced and the two bridge pile foundations 21 is not less than d 2; the d2 is a preset clear distance threshold between the front and rear end faces of the stratum to be isolated and reinforced and the bridge pile foundation 21, and the value range of the d2 is 15-18 m.

In this embodiment, the clear distance between the front end surface of the stratum to be isolated and reinforced and the two bridge pile foundations 21 refers to the minimum clear distance between the front end surface of the stratum to be isolated and reinforced and the bridge pile foundations 21 in the horizontal direction; the net distance between the rear end face of the stratum to be isolated and reinforced and the two bridge pile foundations 21 refers to the minimum net distance between the rear end face of the stratum to be isolated and reinforced and the bridge pile foundations 21 in the horizontal direction.

In this embodiment, d2 is 16m, and in an actual construction process, the value of d2 may be adjusted accordingly according to specific needs; when the value of d2 is adjusted, the larger the water content of the stratum to be isolated and consolidated is, the larger the value of d2 is; conversely, the smaller the water content of the stratum to be isolated and consolidated is, the smaller the value of d1 is.

In this embodiment, the underpass tunnel segment is an arc tunnel segment, the two partition walls 22 are respectively an inner partition wall and an outer partition wall which are located on the inner side and the outer side of the underpass tunnel segment, the longitudinal length of the outer partition wall is greater than that of the inner partition wall, the front end surfaces of the two partition walls 22 and the front end surface of the slurry solidification body 23 are both located on the same tunnel cross section of the underpass tunnel segment, and the rear end surfaces of the two partition walls 22 and the rear end surface of the slurry solidification body 23 are both located on the same tunnel cross section of the underpass tunnel segment, so that the shield tunneling machine can be conveniently constructed in the slurry solidification body 23 to form the constructed underpass tunnel segment.

In this embodiment, through setting up the length of treating to keep apart the reinforcement stratum is greater than the length of bridge pile foundation 21, is close to around the bridge pile foundation 21 the stratum of one side of tunnel section is worn down to protect, and is further will tunnel section is worn down and bridge pile foundation 21 is kept apart, avoids under wear the tunnel section when being under construction in the stratum apart from the far away department of bridge pile foundation 21, the influence is caused to bridge pile foundation 21 to small soil body disturbance and formation pressure that causes during the shield constructs the machine tunnelling, ensures the stability of overpass.

In this embodiment, the two partition walls 22 are vertically arranged, the vertical heights of the two partition walls 22 are the same, and the pile lengths of all the partition piles 26 in the two partition walls 22 are the same as the vertical height of the partition wall 22; the upper surface of the stratum to be isolated and consolidated is located below the upper surface of the isolation wall 22.

In this embodiment, each of the cross beams 25 is located on a cross section of one of the underpass tunnel sections, and the two crown beams 24 and the plurality of cross beams 25 are located on the same plane; the distance between the underpass tunnel segment and the two partition walls 22 is the same.

In this embodiment, the number of the isolation piles 26 included in the two isolation walls 22 is the same, all the isolation piles 26 in the two isolation walls 22 are arranged in multiple rows from back to front, each row of the isolation piles 26 includes two isolation piles 26 respectively located on the left and right sides of the stratum to be isolated and reinforced, two isolation piles 26 in each row of the isolation piles 26 are located on one tunnel cross section of the underpass tunnel section, each cross beam 25 is located between two isolation piles 26 in each row of the isolation piles 26, so that the cross beam 25 is conveniently constructed between two isolation piles 26 in each row of the isolation piles 26, and the reinforcing effect is good.

In this embodiment, the length of the crown beam 24 is equal to the length of the partition wall 22, the width of the crown beam 24 is equal to the width of the partition wall 22, and the cross section of the crown beam 24 is rectangular.

In this embodiment, the two crown beams 24 and the cross beams 25 are all located on the same plane, so that a frame structure on one plane is formed, and stability is good.

In this embodiment, the cross section of the shaft of the isolation pile 26 is circular, and the diameter of the shaft of the isolation pile 26 is 0.58m to 0.62 m;

when the clear distance between the underpass tunnel section and any one of the bridge pile foundations 21 is smaller than d1, the distance between two adjacent front and back separation piles 26 in each separation wall 22 is 0.6-0.65 m;

when the clear distance between the underpass tunnel section and the two bridge pile foundations 21 is not less than d1, the distance between the two adjacent front and back separation piles 26 in each separation wall 22 is 1 m-1.05 m.

In this embodiment, the distance between two adjacent front and back isolation piles 26 in each isolation wall 22 refers to the distance between the central axes of two adjacent front and back isolation piles 26.

In this embodiment, the cross section of the tunnel of the underpass tunnel section is circular, the diameter of the tunnel is 5.8 m-6.2 m, and the width of the stratum to be isolated and reinforced is 6.3 m-6.7 m.

In this embodiment, the length of the isolation pile 26 is 19m to 20m, the diameter of the body of the isolation pile 26 is 0.58m to 0.62m, the isolation pile 26 is a small-diameter reinforced concrete cast-in-place pile, the small-diameter isolation pile 26 is more sensitive to the deformation of the stratum, when the soil disturbance and the stratum pressure caused by the tunneling of the shield tunneling machine are small, the isolation pile 26 can simultaneously resist tension, compression, shear, torsion and bending with the stratum, and the material performance of the isolation pile 26 can be better exerted.

In the embodiment, N rows of middle sleeve valve pipes 29 are distributed in the reinforced stratum from left to right, wherein N is an odd number and is more than or equal to 3; a row of middle sleeve valve tubes 29 is distributed in the middle of the stratum to be reinforced, each row of middle sleeve valve tubes 29 comprises a plurality of middle sleeve valve tubes 29 along the longitudinal extension direction of the underpass tunnel section, the middle sleeve valve tubes 29 in each row of middle sleeve valve tubes 29 are uniformly distributed, each middle sleeve valve tube 29 is vertically distributed, and the bottom of each middle sleeve valve tube 29 is flush with the bottom surface of the stratum to be reinforced;

all the middle sleeve valve tubes 29 distributed in the stratum to be isolated and reinforced are distributed in multiple rows from back to front, each row of the middle sleeve valve tubes 29 comprises the middle sleeve valve tubes 29 distributed on the cross section of the same tunnel from left to right, and the middle sleeve valve tubes 29 in the front and back adjacent two rows of the middle sleeve valve tubes 29 are distributed in a staggered mode;

n side sleeve valve pipes 27 are uniformly distributed between two adjacent front and back isolation piles 26 in each isolation wall 22, wherein n is a positive integer and is more than or equal to 1; all the side sleeve valve tubes 27 in each partition wall 22 are arranged from the rear to the front in the longitudinal extension direction of the underpass tunnel section.

In this embodiment, N is 7.

In the present embodiment, n is 1 or 2; the value of n is correspondingly adjusted according to the distance between the front and rear adjacent two of the separation piles 26 in each of the separation walls 22, and the larger the distance between the front and rear adjacent two of the separation piles 26 in each of the separation walls 22 is, the larger the value of n is; when the distance between two adjacent front and back isolation piles 26 in the isolation wall 22 is 0.6-0.65 m, n is 1; when the distance between two adjacent front and back isolation piles 26 in the isolation wall 22 is 1m to 1.05m, n is 2.

In this embodiment, when the clear distance between the underpass tunnel segment and any one of the bridge pile foundations 21 is smaller than d1, the two bridge pile foundations 21 are respectively a near-side bridge pile foundation close to the underpass tunnel segment and a far-side bridge pile foundation far from the underpass tunnel segment, the underpass tunnel segment is divided into a first underpass tunnel segment with a clear distance between the underpass tunnel segment and the near-side bridge pile foundation smaller than d1 and a second underpass tunnel segment with a clear distance between the underpass tunnel segment and the near-side bridge pile foundation larger than d1, the number of the second underpass tunnel segments is two, and the two second underpass tunnel segments are respectively located on two sides of the first underpass tunnel segment; when the shield tunneling machine tunnels the first lower tunnel section, the shield tunneling machine disturbs the soil body on the peripheral side of the bridge pile foundation 21 and has a large formation pressure, so that the distance between the front and rear adjacent two isolation piles 26 on two sides in the first lower tunnel is set to be 0.6-0.65 m, 1 lateral sleeve valve pipe 27 is arranged between the front and rear adjacent isolation piles 26, grout is injected into the lateral sleeve valve pipe 27 until the grout injected into the lateral sleeve valve pipe 27 is diffused to be connected with the front and rear adjacent two isolation piles 26 to form the grouting reinforcement body, and the grouting reinforcement body is fixedly connected with the front and rear adjacent two isolation piles 26 into a whole to strengthen the strength of the isolation walls 22 on two sides of the first lower tunnel; when the shield tunneling machine tunnels the second underpass tunnel segment, the shield tunneling machine disturbs soil on the peripheral side of the bridge pile foundation 21 and has low formation pressure, so that the distance between two adjacent front and rear isolation piles 26 on two sides in the second underpass tunnel is set to be 1 m-1.05 m, 2 lateral sleeve valve pipes 27 are arranged between the two adjacent front and rear isolation piles 26, and grout is respectively injected into the 2 lateral sleeve valve pipes 27 until the grout injected into the 2 lateral sleeve valve pipes 27 is diffused to be connected with the two adjacent front and rear isolation piles 26 to form the grouting reinforcement body, the grouting reinforcement body is fixedly connected with the two adjacent front and rear isolation piles 26 into a whole, and the strength of the isolation wall 22 far away from the bridge pile foundation 21 is properly reduced; the construction speed of the grouting reinforcement body formed by grouting through the lateral sleeve valve pipe 27 is higher than that of the isolation piles 26, and the grouting reinforcement body is arranged between the front and rear adjacent isolation piles 26 to connect the two adjacent isolation piles 26, so that the construction efficiency can be effectively improved.

In this embodiment, the distance between two adjacent rows of middle sleeve valve tubes 29 in the reinforced stratum is 0.9 to 1.1m, and the distance between two adjacent front and back middle sleeve valve tubes 29 in each row of middle sleeve valve tubes 29 is 0.9 to 1.1 m.

In this embodiment, all the middle sleeve valve tubes 29 in the slurry solidification body 23 are arranged in a quincunx shape and are uniformly arranged, 42.5-grade ordinary portland cement slurry is injected into the middle sleeve valve tubes 29, the slurry injected into the middle sleeve valve tubes 29 is mixed with the soil mass around the arrangement position of the middle sleeve valve tubes 29, the slurry in two adjacent middle sleeve valve tubes 29 is mixed with the soil mass around the arrangement position of the middle sleeve valve tubes 29, and then the two adjacent middle sleeve valve tubes 29 are tightly connected into a whole, and all the middle sleeve valve tubes 29 are injected to mix the slurry in all the middle sleeve valve tubes 29 with the soil mass around to form the slurry solidification body 23, and the formed slurry solidification body 23 has good uniformity, thereby avoiding affecting the tunneling of the shield machine.

As shown in fig. 10, the method for reinforcing and isolating a shield tunnel with a water-rich sand layer for passing through a viaduct bridge includes the following steps in conjunction with fig. 8 and 9:

In this embodiment, when the measurement paying-off is performed on the downward-passing tunnel segment in the step a1, the measurement paying-off is performed on the tunnel center line of the downward-passing tunnel segment according to the pre-designed tunnel center line of the downward-passing tunnel segment; when the two partition walls 22 are measured in the step a1, the wall center lines of the two partition walls 22 are measured and paid off according to the measurement paying off result of the tunnel center line of the tunnel section passing through the lower tunnel.

In this embodiment, during actual construction, the isolation pile 26 is first constructed, the grouting reinforcement is performed after the concrete poured into the isolation pile 26 is finally set, the crown beam 24 is constructed after the grout of the grouting reinforcement is finally set, the grout of the crown beam 24 is constructed after the concrete is finally set, the grout solidification body 23 is constructed between the two crown beams 24 after the grout in the grout solidification body 23 is finally set, and the isolation reinforcement structure is constructed after the crossbeam 25 is finally set.

In this embodiment, when any one of the partition walls 22 is constructed in step a2, the plurality of partition piles 26 in the partition wall 22 are constructed from the front side to the rear side to the middle part; in the process of constructing the plurality of isolation piles 26, grouting and reinforcing the stratum between two adjacent front and rear isolation piles 26 from the front side and the rear side to the middle part by sleeve valve pipes;

when any one of the crown beams 24 is constructed in the step A3, the crown beam 24 is constructed from the front side and the rear side to the middle part;

in the step A4, N rows of middle sleeve valve pipes 29 are arranged from left to right in the consolidated stratum, wherein N is an odd number and is more than or equal to 3; a row of middle sleeve valve tubes 29 is distributed in the middle of the stratum to be reinforced, each row of middle sleeve valve tubes 29 comprises a plurality of middle sleeve valve tubes 29 along the longitudinal extension direction of the underpass tunnel section, the middle sleeve valve tubes 29 in each row of middle sleeve valve tubes 29 are uniformly distributed, each middle sleeve valve tube 29 is vertically distributed, and the bottom of each middle sleeve valve tube 29 is flush with the bottom surface of the stratum to be reinforced;

all the middle sleeve valve tubes 29 distributed in the stratum to be isolated and reinforced are distributed in multiple rows from back to front, each row of the middle sleeve valve tubes 29 comprises middle sleeve valve tubes 29 distributed on the cross section of the same tunnel from left to right, and the middle sleeve valve tubes 29 in the front and back adjacent two rows of the middle sleeve valve tubes 29 are distributed in a staggered mode;

when grouting reinforcement is carried out on the stratum to be isolated and reinforced in the step A4, grouting reinforcement is carried out symmetrically from the left side and the right side to the middle part for multiple times, grouting is carried out symmetrically from the front side and the rear side to the middle part for multiple times, and a quadrilateral grouting area is formed during each grouting reinforcement;

in this embodiment, when grouting reinforcement is performed on a stratum to be isolated and reinforced, grouting reinforcement is performed symmetrically from the left side and the right side to the middle part for multiple times, and grouting is performed symmetrically from the front side and the rear side to the middle part for multiple times, a quadrilateral grouting area is formed in each grouting reinforcement, a first quadrilateral grouting area is formed by grouting two rows of middle sleeve valve pipes 29 on the left side and the right side and middle sleeve valve pipes 29 on the front side and the rear side, and then grouting is performed on the middle sleeve valve pipes 29 in the formed first quadrilateral area, so that the grouting area is blocked by the first quadrilateral area when grouting is performed on the middle sleeve valve pipes 29 in the first quadrilateral area, and the situation that the grout diffusion range in the grouting of the middle sleeve valve pipes 29 in the first quadrilateral area exceeds the preset grout diffusion range is avoided, and the stability of the grouting reinforcement area formed by grouting of the middle sleeve valve pipes 29 is poor.

In this embodiment, when the non-underpass viaduct section is constructed, after the two tunnel holes of the non-underpass viaduct section are both constructed, the communication channel 2 is constructed;

the constructed connecting channel 2 is an underground excavation tunnel which is connected between the two shield tunnels 1 and the tunnel body of which is positioned in the water-rich sand layer, and the constructed connecting channel 2 is divided into a tunnel mouth section and a front side tunnel section which is positioned at the front side of the tunnel mouth section;

as shown in fig. 7, the construction of the connection passage 2 includes the following steps:

step B1, erecting a temporary support structure of the duct piece: a group of segment temporary support structures are respectively erected in the two shield tunnels 1, and the two groups of segment temporary support structures are respectively positioned at the front side and the rear side of the constructed connecting channel 2, which is detailed in figure 5;

the segment temporary supporting structure is erected on the inner side of a shield segment ring in the shield tunnel 1;

step B2, pre-reinforcing the stratum: with reference to fig. 2, 3 and 4, the formation where the constructed communication channel 2 is located is pre-consolidated, and the process is as follows:

step B21, grouting and reinforcing the stratum at the end part of the channel: respectively carrying out advanced small conduit grouting reinforcement on the stratums at the front end and the rear end of the constructed connection channel 2 through the two shield tunnels 1, and forming a channel end stratum reinforcement structure on the outer sides of the two shield tunnels 1;

step B22, grouting and reinforcing the whole channel stratum: sleeve valve pipe grouting reinforcement is respectively carried out on the whole stratum where the constructed communication channel 2 is located through the two shield tunnels 1, and a sleeve valve pipe grouting reinforcement structure is obtained;

step B3, precipitation construction: lowering the water level of the stratum where the constructed connecting channel 2 is located to be below the excavation contour line of the constructed connecting channel 2;

step B4, cutting and removing the pipe piece: cutting and dismantling a shield pipe sheet ring at the hole entering position of the constructed connecting channel 2 in the shield tunnel 1 to obtain a tunnel portal 3 of the constructed connecting channel 2;

step B5, channel opening section excavation and primary support construction: excavating the opening section of the constructed communication channel 2 from back to front through the hole door 3 in the step B4; in the excavation process, primary support is synchronously carried out from back to front;

step B6, excavation of the front side tunnel section and primary support construction: excavating the front side tunnel section of the constructed connecting channel 2 from back to front; and in the excavation process, the front side tunnel section formed by excavation is synchronously supported from back to front.

In this embodiment, after the whole grouting reinforcement of the channel stratum in step B22 is completed, supplementary grouting reinforcement of the strata at the front and rear ends of the constructed connecting channel 2 is performed through the small advancing pipes 8 arranged in step B21, so as to obtain a grouting reinforcement structure of the stratum at the end of the channel, and the grouting reinforcement structure of the stratum at the end of the channel and the grouting reinforcement structure of the sleeve valve pipe in step B22 are fastened and connected into a whole.

In this embodiment, in the precipitation construction in step B3, two rows of precipitation wells respectively disposed on the left and right sides of the constructed communication channel 2 are used to perform precipitation.

And B3, when the precipitation construction is carried out, the construction is carried out according to a conventional precipitation construction method, and the stratum is further reinforced through precipitation.

In this embodiment, after the formation pre-consolidation in step B2 is completed and before precipitation construction in step B3 is performed, a vertical transportation channel 17 is constructed at the rear end of the front side tunnel segment from the ground from top to bottom, and the vertical transportation channel 17 is communicated with the interior of the constructed communication channel 2;

in the step B5, after the opening section is excavated from back to front, the opening section is communicated with the vertical transportation channel 17;

when the excavation and preliminary bracing construction of the front side tunnel segment are performed in the step B6, the front side tunnel segment is excavated from back to front by using the vertical transportation channel 17, and the front side tunnel segment is preliminary braced from back to front by using the vertical transportation channel 17.

In this embodiment, the vertical transportation channel 17 is vertically arranged;

when the vertical transportation channel 17 is constructed, firstly, drilling is carried out from top to bottom by adopting drilling equipment, and a steel casing 18 is arranged in the formed drilled hole; the upper end of the steel casing 18 extends out of the ground and is fixedly supported on the ground, and the bottom end of the steel casing 18 is located below the vault of the front side tunnel section.

When the vertical transportation channel 17 is actually constructed, firstly, the designed elevation of a tunnel portal 3 at the rear end of the constructed connection channel 2 is inclined upwards to the designed arch crown range of the constructed connection channel 2, the position where a gradual-change excavation transition section (namely a tunnel portal transition section or a tunnel portal transition section) is finished is determined, the vertical transportation channel 17 which is directly communicated to the constructed connection channel 2 from the ground downwards is constructed at the corresponding position on the ground by adopting a rotary drilling hole forming method, then a steel casing 18 is placed in the vertical transportation channel 17, the bottom of the steel casing 18 extends to the position below the arch crown primary support erection position of the constructed connection channel, the top of the steel casing 18 is higher than the ground, a gap exists between the steel casing 18 and the vertical transportation channel 17, the gap between the steel casing 18 and the vertical transportation channel 17 is backfilled by adopting concrete, and then the steel casing 18 is fixed on the ground.

It should be noted that, because the gradual change excavation changeover portion later stage still need to draw the excavation backward, consequently perpendicular transport corridor 17 can not set up here, and the earthwork stone of excavating in order to satisfy the contact passageway 2 of being under construction simultaneously can outward transport in time, therefore perpendicular transport corridor 17 sets up the position that the gradual change excavation changeover portion ended. The vertical transportation channel 17 is constructed before the earth and stone excavation is carried out on the constructed connection channel 2, so that the stability of the constructed connection channel 2 can be effectively ensured, and the collapse possibility is reduced; perpendicular transport corridor 17 is used for carrying out outward transportation to the cubic metre of earth that is excavated of the contact passageway 2 of being under construction, also is used for the hoist and mount of required material in the underground, need not to transport the cubic metre of earth who excavates out through shield tunnel 1, has effectively accelerated construction speed. In this embodiment, the top of the steel casing 18 is fixed by using i-steel.

During actual construction, the aperture of the vertical transportation channel 17 is 1.2-1.5 m, the bottom of the steel casing 18 extends to a position 300-400 m below the primary support erection position of the vault of the construction connection channel 2, the top of the steel casing 18 is 500-600 mm higher than the ground, and the wall thickness of the steel casing 18 is 10-15 mm.

The outer diameter of the steel casing 18 is 1 m-1.3 m, the outer diameter of the steel casing 18 is smaller than the aperture of the vertical transportation channel 17, so that the steel casing 18 can be conveniently installed and the concrete can be conveniently reinforced, and the concrete for filling the gap between the steel casing 18 and the vertical transportation channel 17 is C15 concrete. In this embodiment, the diameter of the steel casing 18 is phi 1m, the wall thickness of the steel casing is 10mm, the upper end of the steel casing 18 extends 500mm out of the ground, and the bottom end of the steel casing is 300mm below the primary tunnel supporting structure of the front side tunnel segment.

In this embodiment, the areas where the two shield tunnels 1 are connected with the constructed connecting channel 2 are both tunnel connection areas, the tunnel segment where the tunnel connection area is located in each shield tunnel 1 is a tunnel segment to be reinforced, and the two sets of temporary segment support structures are respectively arranged in the tunnel segments to be reinforced of the two shield tunnels 1;

each group of the segment temporary supporting structures comprises 2N segment temporary supporting structures for temporarily supporting the shield segment rings in the tunnel segment to be reinforced one by one, the 2N segment temporary supporting structures in each group of the segment temporary supporting structures are identical in structure and are arranged from back to front along the longitudinal extension direction of the arranged shield tunnel 1, each segment temporary supporting structure is supported in one shield segment ring, and each segment temporary supporting structure is positioned on one tunnel cross section of the shield tunnel 1; wherein N is a positive integer and N is more than or equal to 2;

every group the interim bearing structure of section of jurisdiction divide into two and is located respectively the interim supporting set of section of jurisdiction of tunnel linking region both sides, every the interim supporting set of section of jurisdiction all includes N interim bearing structure of section of jurisdiction.

In this embodiment, each segment temporary support structure is supported in the middle of the inner side of one shield segment ring. Therefore, the distance between two adjacent segment temporary support structures in each segment temporary support group is the same as the distance between two adjacent shield segment rings in the shield tunnel 1.

In order to ensure the supporting effect, the segment temporary supporting structure is a circular ring-shaped supporting structure for supporting the full section of the shield segment ring.

As shown in fig. 5, in this embodiment, the circular ring-shaped supporting structure includes a plurality of circular arc-shaped supporting frames arranged on the same vertical plane along the circumferential direction, a force applying mechanism for applying a pre-stress is arranged between two adjacent circular arc-shaped supporting frames, and the plurality of force applying mechanisms in the circular ring-shaped supporting structure are arranged along the circumferential direction; the force application mechanism is a screw jack 14, each circular arc-shaped support frame is formed by splicing a plurality of arc-shaped steel supports 12 distributed along the circumferential direction, and every two adjacent arc-shaped steel supports 12 in each circular arc-shaped support frame are connected in a hinged mode; and a support 13 is arranged between each arc-shaped steel bracket 12 and the supported shield pipe sheet ring.

For the convenience of connection, every two adjacent arc shaped steel supports 12 in the circular arc shaped support frame are connected through a hinged seat 11. And one telescopic connecting piece 10 is connected between two adjacent circular arc-shaped support frames in the circular ring-shaped support structure, and the telescopic connecting piece 10 is an arc-shaped connecting piece. In this embodiment, the arc-shaped steel bracket 12 is formed by bending i-shaped steel, and has a good processing effect and a better supporting effect.

To ensure the supporting strength, each of the force applying mechanisms includes a plurality of screw jacks 14 in this embodiment. During actual construction, the number of the screw jacks 14 included in each force application mechanism can be adjusted accordingly according to specific needs.

In this embodiment, N is 4. Therefore, four ring shield segments on the front side and the rear side of the portal 3 of the constructed connection channel 2 are respectively and temporarily supported in each shield tunnel 1, and the segment temporary supporting structure adopts a ring-shaped supporting structure, so that the track laying operation and the passing of a rail car can be met, and the influence caused by cross construction is avoided.

In the actual work progress, the interim bearing structure of section of jurisdiction that adopts combines together with the passageway tip stratum reinforced structure in the shield tunnel 1 outside, form effectual reinforcement support in shield tunnel 1 and the inside and outside both sides of the contact passageway 2 linking department of being under construction, can prevent effectively that the prestressing force that portal department's section of jurisdiction trompil caused from concentrating and the section of jurisdiction deformation fracture that leads to is damaged, strengthen reinforcing and supporting structure in the section of jurisdiction outside simultaneously, inside and outside both sides reinforcing and supporting structure combines together, make the reinforcing effect of contact tunnel portal department shield section of jurisdiction better, it is safer to construct.

In this embodiment, every adjacent two around in the interim supporting group of section of jurisdiction interval between the interim bearing structure of section of jurisdiction is 1.5m, every all be provided with 8 rings in the shield tunnel 1 interim bearing structure of section of jurisdiction.

In order to further ensure the reinforcing effect, a plurality of the temporary segment supporting structures in each group of temporary segment supporting structures are all fastened and connected into a whole through a plurality of longitudinal connecting pieces arranged along the circumferential direction, and each temporary segment supporting structure is arranged along the longitudinal extension direction of the shield tunnel 1. In this embodiment, the longitudinal connecting piece is longitudinal connection shaped steel, the longitudinal connecting piece with section of jurisdiction temporary support structure's arc shaped steel support 12 fastening connection just connects through connecting bolt between the two, and the design dismouting is simple and convenient. For simple and reliable connection, the longitudinal connecting pieces are straight I-shaped steel, and the circumferential distance between every two adjacent longitudinal connecting pieces is 2 m.

During actual construction, through when the interim bearing structure of section of jurisdiction consolidates, treat every group a plurality of in the interim bearing structure of section of jurisdiction all erects to accomplish and all interim bearing structure of section of jurisdiction all passes through after longitudinal connectors fastening connection is as an organic whole, adopt screw jack 14 application prestressing force, the pressure of every jack sets up to 100kN in advance.

In this embodiment, in step B4, the portal 3 is located at the rear side of the constructed connection channel 2, the constructed connection channel 2 is divided into the portal section and a front tunnel section located at the front side of the portal section, the portal section is excavated twice before and after the portal section, and the front tunnel section is formed by excavating once from back to front; b5, when the tunnel entrance section is constructed in the step B, the entrance section is excavated for the first time from back to front, and an excavation-molded entrance transition section is obtained; the cross section of the hole transition section is smaller than that of the front side tunnel section, and the cross section of the hole transition section is gradually increased from back to front;

with reference to fig. 6 and 10, in the excavation process of the portal section from back to front in step B5, synchronously pre-burying multiple rows of grouting pipes 15 in the arch part of the portal transition section from back to front, wherein the multiple rows of grouting pipes 15 are arranged from back to front, each row of grouting pipes 15 comprises multiple grouting pipes 15 arranged along the arch part excavation contour line of the portal transition section, and the multiple grouting pipes 15 in each row of grouting pipes 15 are arranged on the same cross section of the construction communication channel 2; each grouting pipe 15 is inclined upward gradually from back to front;

and B5, when primary support is carried out from back to front, the excavated hole transition section is primarily supported from back to front, and a temporary primary support structure of the hole transition section is obtained.

During actual construction, the cross section structures and the sizes of the opening section and the front side tunnel section are the same as those of the pre-designed constructed communication channel 2. The length of the grouting pipe 15 is 2 m-3 m.

In this embodiment, the temporary primary supporting structure includes a plurality of steel arches 16 for supporting the portal section from back to front, and a bolting-shotcrete supporting structure for supporting the portal section.

In order to improve the reinforcing effect and simplify the construction, the grouting pipe 15 is a small advanced pipe for grouting and reinforcing the arch part stratum of the cave mouth section.

In this embodiment, the structure and the size of the hole door 3 are the same as the cross-sectional structure and the size of the rear end of the hole section.

In this embodiment, in step B6, after the excavation of the front tunnel segment is completed, the shield segment ring located at the front side of the constructed connection channel 2 is cut and removed, and the front tunnel portal of the constructed connection channel 2 is obtained.

In the step B6, after the excavation of the front side tunnel segment is completed, advance support is performed on the arch part stratum of the tunnel portal transition segment through the multiple rows of grouting pipes 15; then, breaking the temporary primary supporting structure in the hole transition section from front to back;

in the process of breaking the temporary primary supporting structure from front to back, performing secondary excavation on the tunnel portal section from front to back to obtain the tunnel portal section formed by excavation; and in the process of carrying out secondary excavation on the opening section from front to back, synchronously carrying out primary support on the opening section formed by excavation from back to front.

In this embodiment, during the secondary excavation of the tunnel portal section from front to back, the advanced small guide pipe is used to advance support the arch wall of the tunnel portal section.

And B4, when the segment is cut and removed, cutting and removing the shield segment ring at the rear side of the constructed connecting channel 2 to obtain the tunnel portal 3 at the rear end of the constructed connecting channel 2, wherein the structure and the size of the tunnel portal 3 are the same as the pre-designed cross section structure and the pre-designed size of the constructed connecting channel 2. Therefore, the portal 3 at the rear end of the constructed communication channel 2 is cut and dismantled twice in front and at the rear.

During actual construction, the length of the opening section is 1.5-3.5 m.

In this embodiment, the length of the opening section is 2m, and the length of the opening section can be correspondingly adjusted according to specific requirements.

Before actually constructing the opening section, firstly carrying out pre-measurement line drawing on the portal 3 to be dismantled, then cutting the segment at the portal 3 and starting to carry out earth and stone excavation on the constructed connection channel 2. In the embodiment, the earth and stone excavation of the constructed connecting channel 2 adopts an up-down step method, which is favorable for the stability of the excavation surface, is suitable for water-rich sand layer areas and ensures the construction safety.

In this embodiment, when the tunnel portal section is excavated, the tunnel portal 3 is obliquely upward to the designed vault of the constructed communication channel 2 from the designed elevation to perform slope excavation, and primary support is timely implemented to form temporary primary support of the gradual excavation transition section (i.e., the tunnel portal section), and the grouting pipe 15 of the transition section is embedded, wherein the angle of the external inserted angle of the embedded grouting pipe 15 needs to ensure that the grouting small pipe does not penetrate through the top slope of the gradual excavation transition section and invades into the tunnel, so the angle of the external inserted angle of the grouting pipe 15 should be larger than the slope angle of the gradual excavation transition section slope, the temporary primary support of the gradual excavation transition section is broken from the opposite direction of excavation after the primary support of the constructed communication channel 2 is penetrated, and the excavation transition section is excavated to the design requirement and is implemented as a permanent primary support structure.

Wherein, the water-rich sand layer refers to a sand layer below the underground water level.

In this embodiment, the constructed communication passage 2 is located below the ground water level.

Because the constructed connecting channel 2 is connected between the two constructed shield tunnels 1, in order to avoid adverse effects on the structural stability of the two shield tunnels 1, the surface subsidence of the area where the connecting channel 2 is located and the like in the precipitation construction process, the method does not carry out precipitation on the stratum of the construction area where the connecting channel 2 is located before carrying out grouting reinforcement on the stratum.

The method is adopted for grouting reinforcement, the construction is simple and convenient, the reinforcement quality is convenient to control, after grouting reinforcement is completed, the reinforced stratum and the shield segments in the constructed shield tunnel 1 are fixedly connected into a whole, the stratum reinforcement effect of the area where the constructed connecting channel 2 is located can be further improved, meanwhile, the structural stability of the shield tunnel 1 can be effectively improved, and the ground surface settlement of the shield tunnel 1 can be effectively limited and even avoided.

According to the invention, the pre-consolidated stratum of the contact channel 2 in the water-rich sand layer area is divided into a plurality of consolidated areas, and different consolidation methods are adopted for carrying out stratum pre-consolidation construction on different consolidated areas, so that the stable consolidation of the pre-consolidated stratum of the contact channel 2 is realized, a foundation is laid for the subsequent excavation of the contact channel 2, the collapse risk during the excavation of the contact channel 2 is reduced, and the construction safety is ensured.

In this embodiment, the constructed connecting channel 2 is horizontally arranged, and the grouting end of the advanced small conduit 8 is located below the vault of the constructed connecting channel 2.

And the areas where the two shield tunnels 1 are connected with the constructed connection channel 2 are provided with the tunnel doors 3 of the constructed connection channel 2.

And after the grouting reinforcement in the step B21 is finished, symmetrically reinforcing the stratums at the front end and the rear end of the constructed connection channel 2 through two symmetrically arranged channel end stratum reinforcing structures, and simultaneously forming two symmetrical grout stopping rings by the two channel end stratum reinforcing structures, so that the grout backflow in the whole grouting reinforcement grouting process of the channel stratum in the step B22 can be prevented, meanwhile, underground water flows at the front end and the rear end of the constructed connection channel 2 can be effectively cut off, the structural stability of the joint between the constructed connection channel 2 and the two shield tunnels 1 is ensured, and the construction safety is ensured.

It should be noted that the stratum reinforcing structure at the end of the channel wraps the stratum of the gradual-change excavation transition section of the connection channel 2, so that the stratum above the gradual-change excavation transition section is prevented from being reinforced improperly when the gradual-change excavation transition section is dug back, and the safety of subsequent excavation of the connection channel 2 is ensured at any time.

In this embodiment, with reference to fig. 1, fig. 2 and fig. 3, when grouting and reinforcing the stratum at the end of the channel in step B21, a set of advanced small ducts 8 is firstly arranged through the two shield tunnels 1 to the stratum at the front end and the rear end of the constructed connection channel 2, and the two sets of advanced small ducts 8 are symmetrically arranged; then, the stratum at the front end and the rear end of the constructed connecting channel 2 are respectively subjected to grouting reinforcement through the two groups of small advanced guide pipes 8;

each group of the small advanced ducts 8 comprises a plurality of small advanced ducts 8 which are uniformly distributed on the same plane, and the plurality of small advanced ducts 8 in each group of the small advanced ducts 8 are distributed from left to right along the width direction of the constructed communication channel 2 and are all distributed in parallel; each small advanced guide pipe 8 is arranged along the longitudinal extension direction of the constructed connecting channel 2, one end of each small advanced guide pipe 8 is a stratum driving end driven into the stratum, and the other end of each small advanced guide pipe 8 is a grouting end; each small lead pipe 8 is gradually inclined upwards from the grouting end to the stratum driving end;

and B23, when the supplementary grouting reinforcement is carried out, the supplementary grouting reinforcement is respectively carried out on the strata at the front end and the rear end of the constructed connecting channel 2 through the two groups of the small advancing guide pipes 8.

During actual construction, the two groups of small advanced guide pipes 8 are convenient to erect and convenient to construct.

The stratum entrance end of the leading small conduit 8 is positioned above the arch top of the constructed connecting channel 2, and the vertical distance between the stratum entrance end and the arch top is 0.5-2 m.

In this embodiment, the vertical distance between the stratum entrance end of the leading small conduit 8 and the vault of the constructed communication channel 2 is 1.5 m. Therefore, the advance small guide pipe 8 is adopted to carry out grouting reinforcement within the range of 1.5m outside the two ends of the constructed connecting channel 2.

In the actual construction process, the vertical distance between the stratum entrance end of the advanced small conduit 8 and the vault of the constructed communication channel 2 can be correspondingly adjusted according to specific requirements.

From the above, the formation strengthening structure at the end of the passage in step B21 is a small lead grouting support structure. Therefore, in the step B21, grouting is carried out according to a conventional advanced small conduit grouting method, actual construction is simple and convenient, and the grouting reinforcement effect is good.

In this embodiment, the constructed communication passage 2 is horizontally arranged.

It should be noted that, because the stratum at the end of the passage near the side wall of the segment of the shield tunnel 1 often has a water passage, and when the passage reinforcing sleeve valve pipe 4 punched from the side tunnel portal 3 is used for reinforcing the stratum, the grouting effect at the end of the stratum is not good because the length of the sleeve valve pipe 4 for reinforcing the passage is long, and the two factors act together, the unset grout is easily washed away by the water when the stratum at the end of the passage is reinforced by the sleeve valve pipe 4 for reinforcing the passage, so the grouting effect of the sleeve valve pipe 4 for reinforcing the passage at the position is very poor; more because this department is located portal 3 tops and is close to 1 section of jurisdiction lateral wall of shield tunnel, often there is the risk of collapsing when the contact passageway excavation, consequently this department needs 8 extra slip casting of little pipe in advance to guarantee the reinforcing effect on stratum, guarantees follow-up contact passageway's excavation safety.

After grouting and reinforcing the stratum at the end part of the channel in the step B21, the two constructed stratum reinforcing structures at the end part of the channel have the following beneficial effects: firstly, the reinforcing effect of subsequent sleeve valve pipe grouting reinforcement can be effectively enhanced, and the two passage end stratum reinforcing structures can be used as grout stopping structures for grouting reinforcement of the sleeve valve pipes in the step B22 to prevent grout leakage, so that the grouting density and grouting pressure of sleeve valve pipe grouting are effectively improved, and the grouting reinforcing strength of the sleeve valve pipes is enhanced; secondly, the shield tunnels 1 on the two sides can be effectively protected, and any adverse effect on the shield tunnels 1 on the two sides in the subsequent construction process is prevented; thirdly, effectively reinforcing shield segments at the joints between the shield tunnels 1 on the two sides and the constructed connecting channel 2, and effectively improving the construction quality of the joints between the constructed connecting channel 2 and the shield tunnels 1 on the two sides; fourthly, the underground water above the joint between the shield tunnel 1 and the constructed connecting channel 2 can be effectively intercepted, the construction quality of the joint between the shield tunnels 1 on the two sides and the constructed connecting channel 2 is further ensured, the construction difficulty and the construction risk are reduced, the construction period is effectively saved, and the grouting reinforcement effect of the subsequent sleeve valve pipe can be further enhanced; meanwhile, the subsequent precipitation effect can be effectively improved; fifthly, the two passage end stratum reinforcing structures and the sleeve valve pipe grouting reinforcing structure can be tightly connected into a whole to form an integral reinforcing structure tightly connected between the two shield tunnels 1, so that the integrity and the stability of the shield tunnels 1 on the two sides and the constructed connecting passage 2 can be effectively enhanced, and the long-term use effect is ensured; sixthly, because the stratum at the two ends of the constructed connecting channel 2 is a reinforcing weak area for the subsequent sleeve valve pipe grouting reinforcement, the defect of the subsequent sleeve valve pipe grouting reinforcement can be effectively overcome through the grouting reinforcement of the stratum at the end part of the channel.

B22, after grouting reinforcement of the sleeve valve pipe is completed, the sleeve valve pipe grouting reinforcement structure integrally and effectively reinforces the stratum where the constructed connection channel 2 is located, the sleeve valve pipe grouting reinforcement structure adopts a radial grouting reinforcement mode, the purpose of reinforcing the stratum where the constructed connection channel 2 is located in the whole range can be met, and the integral reinforcement effect is very good; the arrangement distance of the advanced small pipes 8 in the stratums at the two ends of the constructed connecting channel 2 is smaller, so that the grouting density and the grouting reinforcement effect in the stratums at the two ends of the constructed connecting channel 2 can be effectively ensured; although the arrangement distance of the small advanced pipes 8 in the middle stratum of the constructed connecting channel 2 is larger, the small advanced pipes 8 on the front side and the rear side in the middle stratum of the constructed connecting channel 2 are crossed with each other, so that the grouting density and grouting reinforcement effect in the stratum can be ensured.

After the supplementary grouting reinforcement is actually carried out, the grouting reinforcement effect of the stratum at the end part of the channel in the step B21 is further enhanced, and the overall reinforcement effect of the stratum where the constructed connecting channel 2 is located can be further enhanced.

For simplicity and convenience in control, when grouting reinforcement is carried out on the stratum at the end part of the channel in the step B21, stopping grouting when the grouting pressure of all the small advanced guide pipes 8 in the two groups of small advanced guide pipes 8 reaches P1, and completing the grouting reinforcement process of the stratum at the end part of the channel; wherein P1 is a preset grouting pressure value, and the value range of P1 is 0.7 MPa-0.8 MPa;

when the supplementary grouting reinforcement is actually carried out, stopping grouting when the grouting pressure of all the advanced small pipes 8 in the two groups of advanced small pipes 8 reaches P2, and completing the supplementary grouting reinforcement process; wherein P2 is a preset supplementary grouting pressure value and the value range of P2 is 0.5 MPa-0.6 MPa.

In this example, P1 is 0.75MPa, and P2 is 0.55 MPa. During actual construction, the values of P1 and P2 can be adjusted correspondingly according to specific requirements.

In this embodiment, the areas where the two shield tunnels 1 are connected with the constructed connecting channel 2 are both tunnel connection areas, and each group of the small advanced ducts 8 is uniformly distributed outside one of the tunnel connection areas; the distance D between two small advanced guide pipes 8 positioned at the leftmost side and the rightmost side in each group of small advanced guide pipes 8 is larger than the excavation width of the constructed communication channel 2;

the number of the advanced small catheters 8 in each group of the advanced small catheters 8 is 2M, wherein M is a positive integer and is more than or equal to 3; the number of the advanced small guide pipes 8 positioned at the left side and the right side of the central line of the tunnel of the constructed connecting channel 2 in each group of the advanced small guide pipes 8 is M;

when grouting is performed through any one group of the small advancing pipes 8 in the step B21 and the step B23, the grouting is performed symmetrically towards the left side and the right side from the middle part.

Wherein D is 6 m-12 m larger than the excavation width of the constructed connecting channel 2.

In this embodiment, M is 4. And D ═ 16 m.

During actual construction, the values of M and D can be correspondingly adjusted according to specific requirements.

During actual construction, all the advanced small catheters 8 in each group of the advanced small catheters 8 have the same size and the same laying height. The included angles between the advanced small conduits 8 in each group of advanced small conduits 8 and the horizontal plane are the same, and the grouting ends of all the advanced small conduits 8 in each group of advanced small conduits 8 are located on the same horizontal plane.

In this embodiment, the included angle between the advanced small duct 8 and the horizontal plane (i.e. the insertion angle of the advanced small duct 8) is 15 ° to 30 °.

In this embodiment, the small lead pipe 8 arranged in step B21 is a grouting pipe that is driven into the ground through a segment lifting hole on a shield segment ring in the shield tunnel 1.

It should be noted that, the advanced small guide pipe 8 is arranged through the segment hoisting hole, so that the integrity of the segment ring is ensured to a great extent, the solid quality of the shield tunnel 1 is ensured, and the safety and the stability of the tunnel structure are ensured.

In this embodiment, before sleeve valve pipe grouting reinforcement in step B22, two sleeve valve pipe grouting structures, namely, a front sleeve valve pipe grouting structure and a rear sleeve valve pipe grouting structure, are respectively constructed through the two shield tunnels 1, wherein the two sleeve valve pipe grouting structures are symmetrically arranged and are both grouting reinforcement structures for integrally reinforcing the stratum 5 to be reinforced; each sleeve valve pipe grouting structure comprises a plurality of sleeve valve pipes 4 for channel reinforcement, which are driven into a stratum 5 to be reinforced from the same shield tunnel 1, and the plurality of sleeve valve pipes 4 for channel reinforcement in each sleeve valve pipe grouting structure are radially distributed; the stratum 5 to be reinforced is a stratum within the range of L meters outside the excavation contour line of the constructed connecting channel 2, wherein the value range of L is 2.5-3.5;

each of the channel reinforcing sleeve valve tubes 4 in one sleeve valve tube grouting structure intersects with at least one of the channel reinforcing sleeve valve tubes 4 in the other sleeve valve tube grouting structure.

In this embodiment, L takes a value of 3. The formation 5 to be consolidated is thus a formation within 3 meters outside the excavation outline of the constructed connecting channel 2.

During actual construction, the value of L can be correspondingly adjusted according to specific requirements.

In this embodiment, the stratum 5 to be consolidated is divided into an overlapping consolidation area 6, an outer side grouting weak area 9 located outside the overlapping consolidation area 6, and two end grouting weak areas 7 located on the front side and the rear side of the overlapping consolidation area 6, where the overlapping consolidation area 6 is an area where the grouting areas of the two sleeve valve pipe grouting structures overlap;

the two end grouting weak areas 7 are respectively positioned above the front end and the rear end of the overlapped reinforced area 6, and the small advanced guide pipe 8 arranged in the step B21 is positioned in the end grouting weak area 7; the two end grouting weak areas 7 are advanced small guide pipe grouting reinforcement areas reinforced by advanced small guide pipes 8, and the overlapping reinforcement area 6 and the two end grouting weak areas 7 form a core reinforcement area;

the stratum where the constructed communication channel 2 is located in the core consolidation area.

During actual construction, all the leading small pipes 8 in each group of leading small pipes 8 are positioned in the same end grouting weak area 7.

It should be noted that the outer side grouting weak area 9 and the end grouting weak area 7 are areas where grouting areas of the two sleeve valve pipe grouting structures are not overlapped, and the end grouting weak area 7 is more likely to collapse, so that the reinforcing effect of the area where the grouting areas of the two sleeve valve pipe grouting structures are not overlapped can meet the requirement of the outer side grouting weak area 9 for ground layer reinforcement but cannot meet the requirement of the end grouting weak area 7 for ground layer reinforcement, and therefore the end grouting weak area 7 needs to be additionally subjected to grouting reinforcement construction by the advanced small guide pipe 8.

The outer side grouting weak area 9 is not additionally subjected to grouting reinforcement when the stratum is pre-reinforced, so that the construction period is saved, the outer side grouting weak area 9 can be subjected to secondary reinforcement through small advanced pipes which are arranged at the arch tops of the channels and are parallel to each other when the communication channel 2 is primarily supported, and the stability of the communication channel is ensured.

In this embodiment, the tunnel cave of the constructed communication passage 2 is divided into a lower cave body and an upper cave body located above the lower cave body;

each sleeve valve pipe grouting structure comprises a plurality of groups of upper sleeve valve pipes for reinforcing the stratum 5 to be reinforced in the area where the upper hole body is located and a plurality of groups of lower sleeve valve pipes for reinforcing the stratum 5 to be reinforced in the area where the lower hole body is located, and the plurality of groups of upper sleeve valve pipes and the plurality of groups of lower sleeve valve pipes are distributed from inside to outside; each group of upper sleeve valve pipes comprises a plurality of sleeve valve pipes 4 for channel reinforcement distributed along the excavation contour line of the upper hole body, and the external insertion angles of the sleeve valve pipes 4 for channel reinforcement of the plurality of groups of upper sleeve valve pipes are gradually increased from inside to outside; each group of the lower sleeve valve pipes comprises a plurality of sleeve valve pipes 4 for channel reinforcement distributed along the excavation contour line of the lower hole body, and the external insertion angles of the sleeve valve pipes 4 for channel reinforcement of the plurality of groups of the lower sleeve valve pipes are gradually increased from inside to outside;

and B22, grouting and reinforcing from outside to inside when grouting and reinforcing the sleeve valve pipe through any sleeve valve pipe grouting structure in the sleeve valve pipe grouting and reinforcing process.

The external insertion angle of the sleeve valve pipe 4 for channel reinforcement refers to the included angle between the sleeve valve pipe 4 for channel reinforcement and the central axis of the constructed communication channel 2. The external insertion angle of the sleeve valve tube 4 for channel reinforcement is not more than 30 degrees.

In this embodiment, the areas where the two shield tunnels 1 are connected with the constructed connection channel 2 are both tunnel connection areas, and a plurality of sleeve valve pipe installation holes for installing the sleeve valve pipes 4 for channel reinforcement are formed in the shield pipe sheet rings of the tunnel connection areas in the two shield tunnels 1.

The tunnel connection areas in the two shield tunnels 1 are provided with tunnel portals 3 of the construction connection channels 2, the opening areas of the tunnel portals 3 on the shield segments in the shield tunnels 1 are tunnel portal opening areas, and the sleeve valve pipe mounting holes are located in the tunnel portal opening areas.

It should be noted that, in order to ensure the integrity of the segments of the shield tunnel 1 except for the portal opening area, the sleeve valve pipe 4 for channel reinforcement when the stratum of the contact channel 2 is pre-reinforced can only be drilled into the stratum from the portal opening area, and the maximum elevation angle drilled by the sleeve valve pipe 4 for channel reinforcement is limited by this, so that the sleeve valve pipe 4 for channel reinforcement cannot go deep into the connection area between the shield tunnel 1 and the contact channel 2, thereby causing the grouting of the sleeve valve pipe 4 for channel reinforcement to not completely cover the preset contact channel 2 to be reinforced with the stratum 5, and further causing the end grouting weak area 7.

In this embodiment, the outermost layer passage reinforcing sleeve valve tube 4 located above the hole gate 3 has an outward insertion angle in a range of 25 ° to 30 °.

When actually excavating the constructed connecting channel 2, construction is carried out from back to front along the longitudinal extension direction. In order to ensure the structural stability of the joint between the constructed connecting channel 2 and the shield tunnel 1 and reduce the construction risk, the portal 3 positioned at the rear side of the constructed connecting channel 2 is rectangular, the portal opening area positioned in the shield tunnel 1 at the rear side of the constructed connecting channel 2 is rectangular, and the structure and the size of the portal opening area are the same as those of the portal 3. The width of the portal 3 positioned at the rear side of the constructed connecting channel 2 is less than the excavation width of the constructed connecting channel 2, and the height of the portal 3 is less than the excavation height of the constructed connecting channel 2. Meanwhile, the top of the tunnel door 3 positioned at the rear side of the construction connection channel 2 is lower than the vault of the construction connection channel 2. The grouting end of the leading small guide pipe 8 is positioned above the tunnel door 3, and the grouting end of the leading small guide pipe 8 is positioned below the vault of the constructed communication channel 2.

In this embodiment, a plurality of the advanced small ducts 8 in each group of the advanced small ducts 8 are uniformly distributed, the distance between two adjacent advanced small ducts 8 is the same as the distance between two adjacent shield segment rings in the shield tunnel 1, and the grouting end of each advanced small duct 8 is supported on one shield segment ring.

And B22, when sleeve valve pipe grouting is performed, a conventional sleeve valve pipe grouting reinforcement method is adopted. The length of the constructed connecting channel 2 is 10 m-20 m. In the embodiment, the buried depth of the constructed connection channel 2 is 11.55m, the length is 15.80m, the section size is 3.80m multiplied by 4.57m, miscellaneous fill, silt and medium sand are distributed from top to bottom, the buried depth of the stable water level of the underground water is between 10.30m and 11.80m, and the body of the constructed connection channel 2 is positioned on a sand layer in rich water.

In this embodiment, the adopted sleeve valve tube 4 for channel reinforcement is a PVC tube with a diameter of phi 48mm, the interval is 300mm × 300mm, the grouting liquid is cement-water glass double-liquid slurry, the volume ratio of cement to water glass is 1: 1, the concentration of water glass is 35Be, the water-cement ratio of cement is 1: 1, normal diffusion of the slurry is ensured, and grouting in a mode of gradually increasing pressure is adopted. And B22, when sleeve valve pipe grouting is carried out in the step B, the reinforcing range is 3m outside the tunnel contour of the constructed communication channel 2.

In this embodiment, the advanced small guide pipe 8 is a steel pipe with a diameter of phi 50mm and a length of 2 m. The grout injected into the small lead pipe 8 is the same as the grout injected into the channel-reinforcing sleeve valve tube 4.

In conclusion, when grouting is performed in the step B21, grouting is performed in the step B22, and supplementary grouting is actually performed, grouting is performed in a hole (namely in a tunnel hole of the shield tunnel 1), so that grouting is simple and convenient, grouting reinforcement is not required to be performed from the outside of the hole (namely the ground), construction cost can be reduced, construction period can be saved, the problems that the ground is greatly influenced, construction difficulty is high, investment cost is high, the construction period cannot be effectively guaranteed and the like in the conventional jet grouting pile reinforcement process can be effectively avoided, and the stratum at the joint between the two shield tunnels 1 and the constructed communication channel 2 can be effectively reinforced while the stratum at the joint of the shield tunnel 1 and the constructed communication channel 2 is reinforced; meanwhile, the two shield tunnels 1 can be effectively reinforced, and specifically, the shield segment ring at the joint between the shield tunnels 1 and the constructed connecting channel 2 is effectively reinforced. In addition, the advanced small guide pipe 8 is inserted into the stratum through a pipe piece hoisting hole, and the sleeve valve pipe 4 for channel reinforcement is inserted into the stratum through the portal opening area, so that the construction of the advanced small guide pipe 8 and the sleeve valve pipe 4 for channel reinforcement does not cause any damage to the shield pipe piece ring of the shield tunnel 1, the integrity of the pipe piece ring is ensured to a great extent, the entity quality of the shield tunnel 1 is ensured, and the safety and the stability of the tunnel structure are ensured.

In the embodiment, the upper and lower step method is adopted for excavating the constructed connecting channel 2, and the conventional construction scheme is adopted for primary support and later-stage secondary lining construction.

In this embodiment, a waterproof layer is arranged between the tunnel primary support structure 19 of the constructed communication channel 2 and the tunnel secondary lining 20.

In the actual construction process, after the construction of the tunnel primary support structure 19 of the constructed connection channel 2 is completed, firstly, grouting is carried out on the back of the tunnel primary support from back to front, and then, waterproof layer construction is carried out from back to front; in addition, in the waterproof layer construction process from back to front, the tunnel secondary lining 20 of the constructed connection channel 2 is constructed from back to front; and in the construction process of the tunnel secondary lining 20 of the constructed connecting channel 2 from back to front, grouting the back of the tunnel secondary lining 20 from back to front.

In the actual construction process, after the shield construction of the underpass tunnel section and the three non-underpass sections is completed and the construction of the constructed connecting channel 2 is completed, the construction process of the constructed tunnel is completed.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A shield tunnel construction method for a water-rich sand layer is characterized by comprising the following steps: the constructed tunnel is a double-hole tunnel and is an underground excavation tunnel with a tunnel body positioned in the water-rich sand layer, and two tunnel holes of the constructed tunnel are both shield tunnels (1); the constructed tunnel comprises a lower-passing viaduct tunnel section and a non-lower-passing viaduct tunnel section connected with the lower-passing viaduct tunnel section, wherein one tunnel hole of the lower-passing viaduct tunnel section passes through an existing viaduct and is a lower-passing tunnel section, and two tunnel holes of the non-lower-passing viaduct tunnel section are communicated through a communication channel (2);

the isolation and reinforcement structure comprises two isolation walls (22) which are respectively arranged on the left side and the right side of the underpass tunnel section and a slurry solidification body (23) which is formed by adopting sleeve valve pipes to carry out grouting reinforcement on a stratum to be reinforced and positioned between the two isolation walls (22), the underpass tunnel section is positioned in the slurry solidification body (23), and the slurry solidification body (23) is fixedly connected with the two isolation walls (22) into a whole; each partition wall (22) is provided with a crown beam (24), each partition wall (22) is fixedly connected with the crown beam (24) arranged on the partition wall into a whole, and the two crown beams (24) are fixedly connected into a whole through a plurality of transverse beams (25) from back to front; the crown beams (24) and the cross beams (25) are cast-in-place reinforced concrete beams, and the slurry consolidation body (23), the two partition walls (22) and each crown beam (24) are arranged along the longitudinal extension direction of the underpass tunnel section;

each partition wall (22) comprises a plurality of partition piles (26) which are vertically arranged, and the partition piles (26) are reinforced concrete cast-in-place piles; the plurality of the isolation piles (26) in each isolation wall (22) are arranged from back to front along the longitudinal extension direction of the underpass tunnel section, the front and back adjacent isolation piles (26) in each isolation wall (22) are fixedly connected into a whole through a grouting reinforcement body, and the grouting reinforcement body is a reinforcement structure formed by grouting and reinforcing the stratum between the front and back adjacent isolation piles (26) through sleeve valve pipes;

2. The shield tunnel construction method for the water-rich sand layer according to claim 1, characterized in that: before the stratum of the construction area where the non-underpass tunnel section is located is subjected to precipitation, the stratum of the construction area where the non-underpass tunnel section is located is pre-reinforced by the sleeve valve pipes, a plurality of grouting holes for grouting the sleeve valve pipes are formed in the stratum of the construction area where the non-underpass tunnel section is located, and the plurality of grouting holes are vertically arranged and arranged in a quincunx shape.

3. The shield tunnel construction method for the water-rich sand layer according to claim 1 or 2, characterized in that: when the stratum of the construction area where the underpass tunnel section is located is isolated and reinforced, the method comprises the following steps:

step A1, measuring and setting out: according to a tunnel central line of the lower tunnel section which is designed in advance, measuring and paying off are carried out on the lower tunnel section, and measuring and paying off are respectively carried out on the two partition walls (22);

step A2, constructing the partition wall: the two partition walls (22) are constructed respectively, and the construction methods of the two partition walls (22) are the same;

when any one of the partition walls (22) is constructed, firstly, respectively constructing a plurality of the partition piles (26) in the partition wall (22), respectively grouting and reinforcing the stratum between the front and rear adjacent partition piles (26) which are constructed in the partition wall (22) by using sleeve valve pipes to obtain a grouting reinforcement body formed by construction, and obtaining the partition wall (22) formed by construction after all the partition piles (26) and all the grouting reinforcement bodies in the partition wall (22) are constructed;

step A3, crown beam construction: respectively constructing a crown beam (24) on the two partition walls (22) constructed and formed in the step A2;

step A4, grouting and reinforcing the stratum to be isolated and reinforced: grouting and reinforcing the stratum to be isolated and reinforced between the two isolation walls (22) by using sleeve valve pipes to obtain a slurry solidification body (23) formed by construction, and firmly connecting the slurry solidification body (23) between the two isolation walls (22) formed by construction in the step A2;

step A5, beam construction: and B, constructing a plurality of beams (25) above the slurry consolidation body (23) constructed and formed in the step A4, and enabling each beam (25) to be tightly connected between two crown beams (24).

4. The shield tunnel construction method for the water-rich sand layer according to claim 1 or 2, characterized in that: when the non-underpass viaduct section is constructed, after the construction of the two tunnel holes of the non-underpass viaduct section is finished, constructing the communication channel (2);

the constructed connecting channel (2) is an underground excavation tunnel which is connected between the two shield tunnels (1) and the tunnel body of which is positioned in the water-rich sand layer, and the constructed connecting channel (2) is divided into a tunnel mouth section and a front side tunnel section positioned on the front side of the tunnel mouth section;

when the constructed connection channel (2) is constructed, the method comprises the following steps:

step B1, erecting a temporary support structure of the duct piece: respectively erecting a group of segment temporary support structures in the two shield tunnels (1), and respectively positioning the two groups of segment temporary support structures at the front side and the rear side of the constructed connection channel (2);

the segment temporary supporting structure is erected on the inner side of a shield segment ring in the shield tunnel (1);

step B2, pre-reinforcing the stratum: pre-reinforcing the stratum where the constructed connecting channel (2) is located, wherein the process is as follows:

step B21, grouting and reinforcing the stratum at the end part of the channel: advance small conduit grouting reinforcement is respectively carried out on the stratums at the front end and the rear end of the constructed connection passage (2) through the two shield tunnels (1), and a passage end stratum reinforcement structure is formed on the outer sides of the two shield tunnels (1);

step B22, grouting and reinforcing the whole channel stratum: sleeve valve pipe grouting reinforcement is respectively carried out on the whole stratum where the constructed connection channel (2) is located through the two shield tunnels (1) to obtain a sleeve valve pipe grouting reinforcement structure;

step B3, precipitation construction: the stratum where the constructed connection channel (2) is located is subjected to precipitation, and the underground water level is reduced to be below the excavation contour line of the constructed connection channel (2);

step B4, cutting and removing the pipe piece: cutting and dismantling a shield pipe sheet ring at the hole entering position of the constructed connection channel (2) in the shield tunnel (1) to obtain a tunnel door (3) of the constructed connection channel (2);

step B5, channel opening section excavation and primary support construction: excavating the hole section of the constructed communication channel (2) from back to front through the hole door (3) in the step B4; in the excavation process, primary support is synchronously carried out from back to front;

step B6, excavation of the front side tunnel section and primary support construction: excavating the front side tunnel section of the constructed connecting channel (2) from back to front; and in the excavation process, the front side tunnel section formed by excavation is synchronously supported from back to front.

5. The shield tunnel construction method for the water-rich sand layer according to claim 4, characterized in that: after the formation pre-reinforcement in the step B2 is completed and before precipitation construction is carried out in the step B3, a vertical transportation channel (17) is constructed at the rear end of the front side tunnel section from the ground from top to bottom, and the vertical transportation channel (17) is communicated with the interior of the constructed connection channel (2);

b5, after excavating the opening section from back to front, the opening section is communicated with the vertical transportation channel (17);

and B6, when the front side tunnel section is excavated and preliminary bracing construction is carried out, excavating the front side tunnel section from back to front by using the vertical transportation channel (17), and preliminary bracing the front side tunnel section from back to front by using the vertical transportation channel (17).

6. The shield tunnel construction method for the water-rich sand layer according to claim 4, characterized in that: when grouting and reinforcing the stratum at the end part of the channel in the step B21, firstly, respectively drilling a group of small advanced guide pipes (8) on the stratum at the front end and the rear end of the constructed connection channel (2) through the two shield tunnels (1), wherein the two groups of small advanced guide pipes (8) are symmetrically distributed; then, the strata at the front end and the rear end of the constructed connecting channel (2) are respectively grouted and reinforced through two groups of small advanced guide pipes (8);

each group of the small advanced ducts (8) comprises a plurality of small advanced ducts (8) which are uniformly distributed on the same plane, and the small advanced ducts (8) in each group of the small advanced ducts (8) are distributed from left to right along the width direction of the construction connecting channel (2) and are all distributed in parallel; each small advanced guide pipe (8) is arranged along the longitudinal extension direction of the constructed connecting channel (2), one end of each small advanced guide pipe (8) is a stratum driving end which is driven into the stratum, and the other end of each small advanced guide pipe is a grouting end; each small leading guide pipe (8) is gradually inclined upwards from the grouting end to the stratum driving end.

7. The shield tunnel construction method for the water-rich sand layer according to claim 6, characterized in that: after the whole grouting reinforcement of the channel stratum in the step B22 is completed, supplementary grouting reinforcement is carried out on the stratum at the front end and the rear end of the constructed connecting channel (2) through the small advanced guide pipes (8) arranged in the step B21 to obtain a grouting reinforcement structure of the stratum at the end part of the channel, and the grouting reinforcement structure of the stratum at the end part of the channel and the grouting reinforcement structure of the sleeve valve pipe in the step B22 are fixedly connected into a whole;

and when supplementary grouting reinforcement is actually carried out, supplementary grouting reinforcement is respectively carried out on the strata at the front end and the rear end of the constructed connecting channel (2) through the two groups of small advancing pipes (8).

8. The shield tunnel construction method for the water-rich sand layer according to claim 4, characterized in that: the leading small guide pipe (8) arranged in the step B21 is a grouting pipe which is driven into the stratum through a segment hoisting hole on a shield segment ring in the shield tunnel (1).

9. The shield tunnel construction method for the water-rich sand layer according to claim 4, characterized in that: before sleeve valve pipe grouting reinforcement in the step B22, constructing a front sleeve valve pipe grouting structure and a rear sleeve valve pipe grouting structure respectively through the two shield tunnels (1), wherein the two sleeve valve pipe grouting structures are symmetrically arranged and are both grouting reinforcement structures for integrally reinforcing a stratum (5) to be reinforced; each sleeve valve pipe grouting structure comprises a plurality of sleeve valve pipes (4) for channel reinforcement, which are driven into a stratum (5) to be reinforced from the same shield tunnel (1), and the plurality of sleeve valve pipes (4) for channel reinforcement in each sleeve valve pipe grouting structure are radially distributed; the stratum (5) to be consolidated is a stratum within the range of L meters outside the excavation contour line of the constructed connecting channel (2), wherein the value range of L is 2.5-3.5;

each channel reinforcing sleeve valve pipe (4) in one sleeve valve pipe grouting structure is crossed with at least one channel reinforcing sleeve valve pipe (4) in the other sleeve valve pipe grouting structure.

10. The shield tunnel construction method for the water-rich sand layer according to claim 9, characterized in that: the stratum (5) to be reinforced is divided into an overlapping reinforced area (6), an outer side grouting weak area (9) positioned outside the overlapping reinforced area (6) and two end grouting weak areas (7) respectively positioned on the front side and the rear side of the overlapping reinforced area (6), and the overlapping reinforced area (6) is an area where the grouting areas of the two sleeve valve pipe grouting structures are overlapped;

the two end grouting weak areas (7) are respectively positioned above the front end and the rear end of the overlapped reinforced area (6), and the small advanced guide pipe (8) arranged in the step B21 is positioned in the end grouting weak area (7); the two end grouting weak areas (7) are advanced small guide pipe grouting reinforcement areas reinforced by advanced small guide pipes (8), and the overlapping reinforcement area (6) and the two end grouting weak areas (7) form a core reinforcement area;

the stratum where the constructed communication channel (2) is located in the core reinforcing area.