CN112502732B

CN112502732B - Construction method of shield tunnel in water-rich sand layer

Info

Publication number: CN112502732B
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: 2023-04-25
Anticipated expiration: 2040-11-30
Also published as: CN112502732A

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 a subsurface tunnel with a tunnel body positioned in the water-rich sand layer, the constructed tunnel comprises a downward-penetrating tunnel section and three non-downward-penetrating tunnel sections, the downward-penetrating tunnel section is isolated and reinforced, the shield construction is carried out without precipitation, and the shield construction is carried out after precipitation of the non-downward-penetrating tunnel section. The shield tunnel is divided into a downward-penetrating tunnel section and a non-downward-penetrating tunnel section according to whether the downward-penetrating overpass is in use, and the non-downward-penetrating tunnel section is subjected to dewatering and then is directly constructed; the underpass tunnel section is firstly isolated and reinforced to form a slurry concretion body, so that the shield machine is tunneled in the slurry concretion body, and soil disturbance and stratum pressure caused by the tunnelling of the shield machine during construction are resisted through the slurry concretion body; and the two sides of the slurry consolidation body are respectively provided with the partition walls, so that the stratum pressure can be completely blocked, and the safety and zero settlement of the overpass on the upper side of the underpass tunnel section are ensured.

Description

Construction method of shield tunnel in water-rich sand layer

Technical Field

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

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 foundations of the existing buildings or viaducts, and the problems of protecting and reinforcing the foundations of the existing buildings and the viaducts are brought. Especially when constructing the tunnel in the rich water sand layer that rich water is strong, the structure is loose, the bonding ability is poor, tunnel shield constructs the machine tunnelling in the tunnel and carries out the district to the strong influence area of building and overpass, rich water sand layer's compressibility is extremely big, from poor stability, bearing capacity is not high, very easily induce the disaster accidents such as shield tunnel collapse such as sand collapse in the shield constructs the machine tunnelling process, seriously threat tunnel excavation safety, and the soil body disturbance that causes in the shield constructs the machine tunnelling process produces pressure to the stratum around, and the pressure is conducted all around, conduction speed is fast and conduction scope is wide, when shield constructs the machine cutterhead rotatory cutting, easily destroy the relative stable or balanced state of stratum, cause shield to construct machine and plant first and to the lateral effort of existing overpass pile foundation, endanger shield and the safety of existing overpass.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a construction method of a water-rich sand layer shield tunnel, which has reasonable design, simple construction and good use effect, and the shield tunnel is divided into a downward tunnel section and a non-downward tunnel section according to whether a downward overpass passes through, and the non-downward tunnel section is directly constructed after dewatering; before the construction of the underpass tunnel section, firstly, a slurry consolidation body is formed by isolating and reinforcing stratum, so that the shield machine is used for 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 through the slurry consolidation body; and isolation piles are respectively arranged at two sides of the slurry consolidation body, so that the stratum pressure can be completely blocked, and the safety and zero settlement of the overpass at the upper side of the underpass tunnel section are ensured.

In order to solve the technical problems, the invention adopts the following technical scheme: a construction method of a shield tunnel of a water-rich sand layer is characterized by comprising the following steps: the constructed tunnel is a double-hole tunnel and is an undercut tunnel with a tunnel body positioned in the water-rich sand layer, and two tunnel holes of the constructed tunnel are shield tunnels; the construction tunnel comprises a down-going viaduct tunnel section and a non-down-going viaduct tunnel section connected with the down-going viaduct tunnel section, wherein one tunnel hole of the down-going viaduct tunnel section is penetrated by an existing viaduct and is a down-going tunnel section, and two tunnel holes of the non-down-going 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 down-going viaduct tunnel section and the two tunnel holes of the non-down-going viaduct tunnel section are both non-down-going tunnel sections, and the construction methods of the two tunnel holes are the same;

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

The isolation and reinforcement structure comprises two isolation walls respectively arranged at the left side and the right side of the underpass tunnel section and a slurry consolidation body formed after grouting and reinforcement are carried out on a stratum to be reinforced between the two isolation walls by adopting sleeve valve pipes, 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 isolation wall is provided with a crown beam, each isolation wall is fixedly connected with the crown beam arranged on the isolation wall into a whole, and the two crown beams are fixedly connected with each other into a whole through a plurality of cross beams from back to front; the crown beams and the cross beams are cast-in-situ reinforced concrete beams, and the slurry concretes, the two isolation walls and each crown beam are distributed along the longitudinal extending direction of the underpass tunnel section;

each isolation wall comprises a plurality of isolation piles which are vertically distributed, and each isolation pile is a reinforced concrete filling pile; the isolation piles in each isolation wall are distributed from back to front along the longitudinal extending direction of the down-penetrating tunnel section, the front adjacent isolation piles and the rear adjacent isolation piles in each isolation wall are fixedly connected into a whole through grouting reinforcement bodies, and the grouting reinforcement bodies are reinforcement structures formed by grouting reinforcement of stratum between the front adjacent isolation piles and the rear adjacent isolation piles through sleeve valve pipes;

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 positioned, and then shield construction is carried out on the non-underpass tunnel section.

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

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

step A1, measuring and paying off: according to a pre-designed tunnel central line of the underpass tunnel section, measuring and paying off are carried out on the underpass tunnel section, and measuring and paying off are respectively carried out on the two isolation walls;

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

when any one of the isolation walls is constructed, a plurality of isolation piles in the isolation wall are respectively constructed, and a sleeve valve pipe is adopted to respectively perform grouting reinforcement on stratum between two adjacent isolation piles before and after construction in the isolation wall, so as to obtain a grouting reinforcement body for construction molding, and after all the isolation piles and all the grouting reinforcement bodies in the isolation wall are constructed, the construction molding isolation wall is obtained;

And A3, crown beam construction: c, respectively constructing a crown beam on the two isolation walls formed in the step A2;

step A4, grouting and reinforcing the stratum to be isolated and reinforced: grouting reinforcement is carried out on the stratum to be isolated and reinforced between the two isolation walls by adopting sleeve valve pipes, a slurry consolidation body formed by construction is obtained, and the slurry consolidation body is firmly connected between the two isolation walls formed by construction in the step A2;

and A5, construction of a cross beam: and C, constructing a plurality of cross beams above the slurry consolidated body formed in the step A4, and enabling each cross beam to be fixedly connected between two crown beams.

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

the constructed communication channel is a subsurface tunnel which is connected between two shield tunnels and is positioned in the water-rich sand layer, and the constructed communication channel is divided into a tunnel portal section and a front tunnel section positioned at the front side of the tunnel portal section;

when constructing the constructed communication channel, the method comprises the following steps:

Step B1, erecting a temporary support structure of the duct piece: respectively erecting a group of duct piece temporary supporting structures in the two shield tunnels, and respectively enabling the two groups of duct piece temporary supporting structures to be positioned at the front side and the rear side of a constructed communication channel;

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

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

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

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

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

And B3, precipitation construction: dewatering the stratum where the constructed communication channel is located, and lowering the underground water level to the position below the excavation outline of the constructed communication channel;

step B4, segment cutting and dismantling: cutting and dismantling a shield segment ring at the hole entering position of the constructed connecting channel in the shield tunnel to obtain a portal of the constructed connecting channel;

step B5, excavating a channel hole section and performing primary support construction: b4, excavating the opening section of the constructed communication channel from back to front through the portal in the step; in the process of excavation, primary support is synchronously carried out from back to front;

and B6, excavating a front tunnel section and performing primary support construction: excavating the front tunnel section of the constructed communication channel from back to front; and in the excavation process, synchronously carrying out primary support on the front tunnel section formed by excavating from back to front.

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

B5, excavating the hole section from back to front, wherein the hole section is communicated with the vertical transportation channel;

and B6, excavating the front tunnel section from back to front by utilizing a vertical transportation channel and performing primary support on the front tunnel section from back to front by utilizing the vertical transportation channel when the front tunnel section is excavated and the primary support is performed in the step B6.

The construction method of the water-rich sand layer shield tunnel is characterized by comprising the following steps of: in the step B21, when grouting reinforcement is carried out on stratum at the end part of the channel, a group of advance small guide pipes are respectively arranged on stratum at the front end and the rear end of the constructed communication channel through two shield tunnels, and the two groups of advance small guide pipes are symmetrically arranged; grouting and reinforcing stratum at the front end and the rear end of the constructed communication channel respectively through two groups of the advance small guide pipes;

each group of the leading small guide pipes comprises a plurality of leading small guide pipes which are uniformly distributed on the same plane, and the leading small guide pipes in each group of the leading small guide pipes are distributed from left to right along the width direction of the constructed communication channel and are distributed in parallel; each small advance conduit is arranged along the longitudinal extending direction of the constructed communication channel, one end of each small advance conduit is a stratum driving end driven into the stratum, and the other end of each small advance conduit is a grouting end; each of the leading small conduits is gradually inclined upward from the grouting end toward the formation driving end.

The construction method of the water-rich sand layer shield tunnel is characterized by comprising the following steps of: after the integral grouting reinforcement of the passage stratum in the step B22 is completed, the stratum at the front end and the back end of the constructed communication passage is required to be respectively subjected to supplementary grouting reinforcement through the advance small guide pipes arranged in the step B21, so that a stratum grouting reinforcement structure at the end part of the passage is obtained, and the stratum grouting reinforcement structure at the end part of the passage is fastened and connected with the sleeve valve pipe grouting reinforcement structure in the step B22 into a whole;

and when the supplementary grouting reinforcement is actually carried out, the two groups of the advanced small guide pipes are used for respectively carrying out supplementary grouting reinforcement on stratum at the front end and the rear end of the constructed communication channel.

The construction method of the water-rich sand layer shield tunnel is characterized by comprising the following steps of: and B21, arranging an advance small guide pipe which is a grouting pipe driven into the stratum through a pipe piece lifting hole on a shield pipe piece ring in the shield tunnel.

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

Each of the channel-reinforcing sleeve pipes in one sleeve pipe grouting structure crosses at least one of the channel-reinforcing sleeve pipes in the other sleeve pipe grouting structure.

The construction method of the water-rich sand layer shield tunnel is characterized by comprising the following steps of: the stratum to be reinforced is divided into a heavy overlaying and reinforcing area, an outer grouting weak area positioned at the outer side of the overlaying and reinforcing area and two end grouting weak areas positioned at the front side and the rear side of the overlaying and reinforcing area respectively, and the overlaying and reinforcing area is an area where 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 reinforcing area, and the advance small guide pipe arranged in the step B21 is positioned in the end grouting weak area; the two end grouting weak areas are all advanced small conduit grouting reinforcing areas which are reinforced by adopting advanced small conduits, and the overlapping reinforcing areas and the two end grouting weak areas form a core reinforcing area;

and the stratum where the constructed connecting channel body is positioned 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 manpower and material resources.

2. The shield of the underpass tunnel section is firstly isolated and reinforced before the shield of the underpass tunnel section is underpass, the bridge pile foundations of the underpass tunnel section and the overpass are isolated and stopped by arranging an isolating and reinforcing structure on the water-rich sand layer, the bridge pile foundations of the overpass bridge caused by the precipitation of the underpass tunnel section by using the precipitation well on the water-rich sand layer are prevented from sedimentation, and the safety is good.

3. When the isolation reinforcement is actually carried out, the shield machine is driven to construct a tunneling section in the slurry consolidation body through arranging the slurry consolidation body, wherein the slurry consolidation body is a mixture of slurry injected into the sleeve valve pipe and surrounding soil, and is not a pure cement slurry pile formed by grouting pure cement slurry, the strength of the slurry consolidation body is smaller than that of the pure cement slurry, and the tunneling of the shield machine is not influenced when the tunneling section is driven; meanwhile, the strength of the slurry concretion body is far greater than that of the surrounding soil body, the slurry concretion body can resist more stratum pressure than the soil body, and soil disturbance and stratum pressure caused by shield tunneling in the process of tunneling the underpass tunnel section are eliminated. Meanwhile, the two sides of the slurry consolidation body are respectively provided with the partition walls to resist soil disturbance and formation pressure which cannot be eliminated by the slurry consolidation body, so that safety and zero settlement of the overpass at the upper side of the underpass tunnel section are ensured. The isolation piles are small-diameter reinforced concrete filling piles, the pile bodies of the small-diameter reinforced concrete filling piles are more sensitive to deformation of the stratum, and when the stratum is deformed slightly, the small-diameter pile bodies and the stratum can be stretched, pressed, sheared, twisted and bent simultaneously, so that the material performance of the reinforced concrete filling piles is exerted more easily.

4. The adopted isolation and reinforcement construction method has wide application range, is suitable for the isolation and reinforcement construction process of the shield tunnel underpass viaduct, and can be suitable for the isolation and reinforcement construction in the stratum below various buildings.

5. The adopted construction method of the connecting channel has the advantages of simple steps, reasonable design, simple construction and low input cost.

6. The advanced small conduit grouting reinforcement method for the end stratum adopted by the formation pre-reinforcement of the communication channel has the advantages of simple construction, easy control of grouting process and good reinforcement effect, the advanced small conduit adopted by the formation grouting reinforcement of the end stratum is simple and convenient to lay and has good reinforcement effect, before the formation of the communication channel is wholly reinforced, a stable grouting stop ring is formed, the formation of the end part of the communication channel can be effectively reinforced, and simultaneously, the grouting reinforcement of the formation of the end part and the grouting reinforcement of the sleeve valve tube are mutually complemented, so that the final reinforcement effect of the formation of the communication channel can be effectively enhanced; moreover, the shield tunnel can be effectively reinforced from the outside through end stratum grouting reinforcement, and the reinforcement quality and the connection effect of the joint of the shield tunnel and the connecting channel can be ensured; in addition, through tip stratum slip casting reinforcement can be with connection passageway stratum reinforced structure and both ends shield tunnel fastening connection as an organic whole, further ensure shield tunnel and connection passageway's whole reinforcement effect to can be with shield tunnel's whole stability. According to the invention, the stratum reinforcing structures at the end parts of the channels are arranged to symmetrically reinforce stratum at the front and rear ends of the constructed connecting channel, and two symmetrical slurry stopping rings are formed by the stratum reinforcing structures at the end parts of the two channels, so that slurry backflow in the whole grouting reinforcing grouting process of the channel stratum can be prevented, underground water flows at the front and rear ends of the constructed connecting channel can be effectively cut off, the structural stability of the joint between the constructed connecting channel and two shield tunnels is ensured, and the construction safety is ensured.

7. The sleeve valve pipe grouting reinforcement structure adopted by the stratum pre-reinforcement of the communication channel is simple and convenient to construct, the grouting process is easy to control, the reinforcement effect is good, the sleeve valve pipe grouting reinforcement structure formed by construction integrally and effectively reinforces the stratum where the communication channel is constructed, the radial grouting reinforcement mode can fulfill the aim of reinforcing the stratum where the communication channel is constructed in a full range, and the integral reinforcement effect is very good; the arrangement space of the advanced small guide pipes in the stratum at the two ends of the constructed communication channel is smaller, so that grouting density and grouting reinforcement effect in the stratum at the two ends of the constructed communication channel can be effectively ensured; while the leading small guide pipes in the middle part of the constructed communication channel are arranged at larger intervals, the leading small guide pipes on the front side and the rear side in the middle part of the constructed communication channel are mutually intersected, so that the grouting density and grouting reinforcement effect in the stratum can be ensured.

8. When the stratum of the connecting channel is pre-reinforced, grouting reinforcement of the small advance guide pipe at the end part of the connecting channel is combined with integral reinforcement of the sleeve valve pipe of the stratum of the connecting channel, construction is simple and convenient, reinforcement quality is convenient to control, after grouting reinforcement is completed, the reinforced stratum and the shield segment in the constructed shield tunnel are fixedly connected into a whole, the structure stability of the shield tunnel can be effectively improved while the stratum reinforcement effect of the area where the connecting channel is located is further improved, and the earth surface subsidence of the shield tunnel can be effectively limited or even avoided. The communication channel pre-reinforcement stratum in the water-rich sand layer area is divided into a plurality of reinforcement areas, and stratum pre-reinforcement construction is carried out on different reinforcement areas by adopting different reinforcement methods, so that the communication channel pre-reinforcement stratum is simply, conveniently, quickly and reliably reinforced, a foundation is laid for excavation of a subsequent communication channel, collapse risk during excavation of the communication channel is reduced, and construction safety is guaranteed.

9. The temporary support structure of the duct piece is reasonable in design, convenient to assemble and disassemble, good in reinforcing effect, small in occupied space and capable of meeting the requirement of track laying operation construction. The temporary support structure of the duct piece in the hole is combined with the stratum reinforcing structure at the end part of the passage outside the shield tunnel, and the inner side and the outer side of the joint part of the shield tunnel and the constructed connecting passage are provided with effective reinforcing supports, so that the duct piece deformation, cracking and damage caused by the prestress concentration caused by the duct piece opening at the door can be effectively prevented, the reinforcing support structure is reinforced outside the duct piece, and the inner side and the outer side reinforcing support structures are combined together, so that the reinforcing effect of the shield duct piece at the door of the connecting tunnel is better, and the construction is safer. When the prior connecting channel is constructed, the duct piece support adopts a door type support frame, and reserved personnel, small machines or shield storage battery cars pass through door openings, so that the follow-up track laying engineering construction can not be met.

10. The 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 connection channel, and can avoid risks brought by the construction process of the connection channel to track laying and rail car running in the shield tunnel, and the vertical transportation channel is formed at the position of 2m of a hole formed in the connection channel for carrying out earthwork outward and material hoisting.

11. The pre-reinforcing method for the stratum of the connecting channel is reasonable in design, simple and convenient to construct and good in reinforcing effect, the advanced region to be reinforced of the stratum of the connecting channel of the water-rich sand layer is divided, and the corresponding grouting reinforcing method is adopted to effectively reinforce, so that the reinforced stratum and the shield segment of the constructed shield tunnel are fixedly connected into a whole, the reinforcing effect of the stratum of the constructed connecting channel is further improved, meanwhile, the structural stability of the shield tunnel can be effectively improved, the earth surface subsidence of the shield tunnel can be effectively limited or even avoided, a foundation is laid for excavating the connecting channel, the collapse risk of the connecting channel is reduced, and the construction safety is guaranteed. And erect the interim bearing structure of section of jurisdiction in shield tunnel and contact passageway junction earlier before stratum is strengthened in advance, effectively consolidate shield tunnel and contact passageway junction stratum in step when the stratum is strengthened in advance, ensure shield tunnel and contact passageway junction's steadiness to effectively reduce and avoid even rich water sand layer shield interval contact passageway to advance the cave construction risk.

12. The stratum of the communication channel is pre-reinforced and then subjected to precipitation construction, the stratum is further reinforced through precipitation, and the post-precipitation construction cannot cause any adverse effect on the stability of the constructed shield tunnel due to good stratum pre-reinforcement effect.

13. The construction method of the connecting channel has the advantages of simple steps, reasonable design, simple and convenient construction, safe and reliable construction process, the temporary support structure of the duct piece is firstly erected at the joint of the shield tunnel and the connecting channel before the stratum is pre-reinforced, then the stratum pre-reinforcement is carried out by combining the grouting reinforcement of the stratum advance small guide pipe at the end part of the channel with the integral grouting reinforcement of the stratum sleeve valve pipe where the channel is positioned, the earthwork outward transportation and the material hoisting are carried out by constructing the vertical transportation channel after the stratum is pre-reinforced, the construction process of the connecting channel between the shield sections of the water-rich sand layer can be simply completed, and the construction process is safe and reliable. The invention adopts grouting reinforcement in the tunnel and the circular ring-shaped pipe piece support, thereby ensuring the safety of the formed tunnel pipe piece in the process of breaking the tunnel door and meeting the normal running of the track laying operation; meanwhile, in the excavation process, the construction task is safely and rapidly completed by adding temporary grid arches and vertical transportation measures. And moreover, the construction process of the connecting channel can not influence the subsequent construction process of the shield tunnel, the construction progress can not be influenced, the construction period can be effectively ensured, and any adverse effect can not be caused on the stability of the constructed shield tunnel structure.

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 underpass or not, and the non-underpass tunnel section is subjected to dewatering and then is directly constructed; before the construction of the underpass tunnel section, firstly, a slurry consolidation body is formed by isolating and reinforcing stratum, so that the shield machine is used for 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 through the slurry consolidation body; and isolation piles are respectively arranged at two sides of the slurry consolidation body, so that the stratum pressure can be completely blocked, and the safety and zero settlement of the overpass at the upper side of the underpass tunnel section are ensured.

The technical scheme of the invention is further described in detail through the drawings and the embodiments.

Drawings

FIG. 1 is a block diagram of a construction method of the present invention.

Fig. 2 is a construction state diagram of the present invention when the communication channel is pre-reinforced in the stratum.

FIG. 3 is a schematic diagram of the layout positions of the advance small guide pipe and the sleeve valve pipe on the cross section of the shield tunnel when the stratum of the communication channel is pre-reinforced.

FIG. 4 is a schematic view of the layout of the upper sleeve valve tube, the advance small conduit and the portal in the cross section of the communication channel of the present invention.

Fig. 5 is a schematic view showing a supporting state of the temporary supporting structure for duct pieces according to the present invention.

Fig. 6 is a schematic view of the construction state of the communication channel according to the present invention.

Fig. 7 is a block flow diagram of a method of constructing a contact channel in accordance with the present invention.

FIG. 8 is a schematic elevational view of an insulation reinforcement structure according to the present invention.

FIG. 9 is a schematic plan layout view of bridge pile foundation, spacer piles, side sleeve valve tubes and middle sleeve valve tubes according to the present invention.

FIG. 10 is a schematic diagram of the cross-sectional layout position of a grouting pipe on the opening section of the communication channel according to the present invention.

Reference numerals illustrate:

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

4-sleeve valve tube for channel reinforcement; 5-stratum to be reinforced; 6-overlapping the reinforced areas;

7-end grouting weak areas; 8-leading small catheter; 9-an outside grouting weak area;

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

13-supporting seats; 14-screw jack; 15-grouting pipe;

16-steel arches; 17-vertical transport channels; 18-steel casing;

19-a tunnel primary support structure; 20-secondary lining of the tunnel;

21-bridge pile foundation; 22-partition walls; 23-slurry consolidation;

24-crown beam; 25-a cross beam; 26-isolation piles;

27-a side sleeve valve tube; 29-middle sleeve valve tube.

Detailed Description

The construction method of the shield tunnel of the water-rich sand layer is shown in fig. 1, wherein the constructed tunnel is a double-hole tunnel and is a subsurface 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 down-going viaduct tunnel section and a non-down-going viaduct tunnel section connected with the down-going viaduct tunnel section, wherein one tunnel hole of the down-going viaduct tunnel section is penetrated by an existing viaduct and is a down-going tunnel section, and two tunnel holes of the non-down-going viaduct tunnel section are communicated through a communication channel 2, as shown in fig. 2 in detail;

referring to fig. 8 and 9, the isolation and reinforcement structure includes two isolation walls 22 respectively arranged on the left and right sides of the underpass tunnel section and a slurry consolidation body 23 formed by grouting and reinforcement of the stratum to be reinforced between the two isolation walls 22 by using sleeve valve pipes, the underpass tunnel section is located in the slurry consolidation body 23, and the slurry consolidation body 23 is fixedly connected with the two isolation walls 22 into a whole; a crown beam 24 is arranged on each isolation wall 22, each isolation wall 22 is fixedly connected with the crown beam 24 arranged on the isolation wall into a whole, and the two crown beams 24 are fixedly connected with each other 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-situ reinforced concrete beams, and the slurry concretes 23, the two partition walls 22 and each crown beam 24 are distributed along the longitudinal extending direction of the underpass tunnel section;

each isolation wall 22 comprises a plurality of isolation piles 26 which are vertically distributed, and the isolation piles 26 are reinforced concrete filling piles; the plurality of isolation piles 26 in each isolation wall 22 are distributed from back to front along the longitudinal extending direction of the underpass tunnel section, the front and rear adjacent isolation piles 26 in each isolation wall 22 are connected into a whole through grouting reinforcement bodies in a fastening manner, and the grouting reinforcement bodies are reinforcement structures formed by grouting reinforcement of strata between the front and rear adjacent isolation piles 26 by sleeve valve pipes;

In this embodiment, before precipitation is performed on the stratum of the construction area where the non-underpass tunnel section is located, the sleeve valve pipe is adopted to pre-reinforce the stratum of the construction area where the non-underpass tunnel section is located, 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 pipe, and the grouting holes are vertically distributed and are distributed in a quincuncial shape.

When the stratum in the construction area where the non-underpass tunnel section is located is subjected to precipitation in actual construction, precipitation is carried out through two rows of precipitation wells respectively arranged at the left side and the right side of the stratum in the construction area where the non-underpass tunnel section is located.

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

step A1, measuring and paying off: measuring and paying off the underpass tunnel section according to a pre-designed tunnel center line of the underpass tunnel section, and measuring and paying off the two partition walls 22 respectively;

and A2, construction of a partition wall: respectively constructing two isolation walls 22, wherein the construction methods of the two isolation walls 22 are the same;

When any one of the isolation walls 22 is constructed, firstly, respectively constructing a plurality of isolation piles 26 in the isolation wall 22, respectively grouting and reinforcing stratum between two adjacent isolation piles 26 before and after construction in the isolation wall 22 by adopting sleeve valve pipes to obtain grouting reinforcement bodies formed by construction, and after all the isolation piles 26 and all the grouting reinforcement bodies in the isolation wall 22 are constructed, obtaining the isolation wall 22 formed by construction;

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

step A4, grouting and reinforcing the stratum to be isolated and reinforced: grouting reinforcement is carried out on the stratum to be isolated and reinforced between the two isolation walls 22 by adopting sleeve valve pipes, a slurry consolidation body 23 formed by construction is obtained, and the slurry consolidation body 23 is fastened and connected between the two isolation walls 22 formed by construction in the step A2;

and A5, construction of a cross beam: and (3) constructing a plurality of beams 25 above the slurry consolidated body 23 formed in the construction step A4, and enabling each beam 25 to be fixedly connected between two crown beams 24.

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

In this embodiment, two of the partition walls 22 are disposed in parallel. The shape of each of the partition walls 22 is the same as the shape of the crown beam 24 provided thereon, and the longitudinal length of each of the partition walls 22 is the same as the longitudinal length of 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 fixedly connected with the lower surface of the crown beam 24 disposed on each isolation wall 22, the upper surfaces of the crown beam 24 and the plurality of cross beams 25 are flush with the ground at the location, and the upper surface of the stratum to be isolated and reinforced is located below the crown beam 24.

In this embodiment, a plurality of cross beams 25 are all horizontally arranged, and a plurality of cross beams are fastened and connected into 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 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 downward tunnel section are caused during shield tunneling, pressure generated by stratum around the downward tunnel section is generated, and the soil disturbance and water loss caused during shield tunneling can cause disturbance and settlement on bridge pile foundations 21 of viaducts, so that before the downward tunnel section is constructed, the shield tunneling machine is tunneled into the downward tunnel section through the slurry concretion body 23, the slurry concretion body 23 is arranged to enable the shield tunneling machine to tunnel into the downward tunnel section through the slurry concretion body 23, the cross section area of the slurry concretion body 23 is larger than that of the downward tunnel section, the slurry concretion body 23 can effectively resist the soil disturbance and stratum pressure caused during shield tunneling, and the disturbance on the bridge pile foundations 21 caused by the soil disturbance and irregular diffusion of stratum pressure to the periphery caused during shield tunneling is avoided; meanwhile, the slurry consolidation body 23 isolates the underpass tunnel section from the bridge pile foundation 21, and the shield machine is used for 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; by arranging the partition walls 22 on the left side and the right side of the slurry consolidation body 23 respectively, soil disturbance and formation pressure which cannot be eliminated by the slurry consolidation body 23 are resisted, and safety and zero settlement of the overpass on the upper side of the underpass tunnel section are ensured; the integrity of the two isolation walls 22 is enhanced by arranging the crown beams 24 on the tops of the two isolation walls 22 respectively, and the crown beams 24 are fastened and connected into a whole through the plurality of cross beams, so that the integrity and the position accuracy of the whole isolation reinforcing structure are enhanced, the reinforcing effect is good, and the position of the isolation walls 22 is prevented from being deviated due to soil disturbance and formation pressure caused by tunneling of a shield tunneling machine.

In this embodiment, the grouting liquid in the middle sleeve valve tube 29 is 42.5 grade ordinary silicate cement grouting liquid, the slurry concretion 23 is a mixture of the grouting liquid in the middle sleeve valve tube 29 and the soil around the laying position of the middle sleeve valve tube 29, and is not a pure cement grouting pile formed by grouting pure cement grouting liquid, the strength of the slurry concretion 23 is smaller than that of the pure cement grouting liquid, but is larger than that of the soil around itself, and the strength of the slurry concretion 23 is smaller than that of the pure cement grouting liquid, so that the slurry concretion 23 cannot influence the tunneling of the shield machine during the construction of the underpass tunnel section, and the strength of the slurry concretion 23 is far larger than that of the soil around itself, so that the slurry concretion 23 can resist more stratum pressure than the soil.

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

In this embodiment, the slurry consolidation 23 is formed by incomplete grouting of all the middle sleeve valve pipes 29, the upper surface of the slurry consolidation 23 is higher than the vault of the downward tunnel section and the clear distance between the two is not less than 2m, the bottom of the slurry consolidation 23 is positioned below the downward tunnel section and the clear distance between the two is not less than 1.5m, the construction speed is improved by incomplete grouting of the middle sleeve valve pipes 29, and the cost is saved.

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

when the clear distance between the underpass tunnel section and the two bridge pile foundations 21 is not smaller 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 underpass 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 clear distance between the underpass tunnel section and the bridge pile foundation 21 refers to the minimum clear distance between the underpass tunnel section and the bridge pile foundation 21 in the horizontal direction.

In the embodiment, d1=6m, in the actual construction process, the value of d1 can be correspondingly adjusted according to specific requirements, 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 reinforced, the larger the value of d 1.

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

the front end face of the stratum to be isolated and reinforced is positioned in front of the viaduct, and the rear end face of the stratum to be isolated and reinforced 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 smaller 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 smaller than d2; wherein d2 is a preset clear distance threshold value between the front end surface and the rear end surface of the stratum to be isolated and reinforced and the bridge pile foundation 21, and the value range of d2 is 15 m-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 clear 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 clear 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 the embodiment, d2=16m, and in the actual construction process, the value of d2 can be correspondingly adjusted according to specific needs; when the value of d2 is adjusted, the larger the water content of the stratum to be isolated and reinforced is, the larger the value of d2 is; conversely, the smaller the water content of the stratum to be isolated and reinforced, the smaller the value of d 1.

In this embodiment, the underpass tunnel section is an arc tunnel section, the two isolation walls 22 are respectively an inner isolation wall and an outer isolation wall located at the inner side and the outer side of the underpass tunnel section, the longitudinal length of the outer isolation wall is greater than that of the inner isolation wall, the front end faces of the two isolation walls 22 and the front end face of the slurry consolidation body 23 are both located on the same tunnel cross section of the underpass tunnel section, the rear end faces of the two isolation walls 22 and the rear end face of the slurry consolidation body 23 are both located on the same tunnel cross section of the underpass tunnel section, so that the shield tunneling machine is convenient to construct in the slurry consolidation body 23 to form the constructed underpass tunnel section.

In this embodiment, through setting up wait to keep apart the length of strengthening stratum is greater than the length of bridge pile foundation 21, be close to around the bridge pile foundation 21 the stratum of one side of tunneling section under is protected, further will tunneling section under is kept apart with bridge pile foundation 21, avoids tunneling section under when constructing in the stratum far away from bridge pile foundation 21, the tiny soil body disturbance and the stratum pressure that cause when the shield constructs the machine tunnelling cause the influence to bridge pile foundation 21, ensures the stability of overpass.

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

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

In this embodiment, the number of the isolation piles 26 included in the two isolation walls 22 is the same, all isolation piles 26 in the two isolation walls 22 are distributed from back to front in multiple rows, each row of isolation piles 26 includes two isolation piles 26 respectively located at the left and right sides of the stratum to be isolated and reinforced, two isolation piles 26 in each row of isolation piles 26 are located on a tunnel cross section of the underpass tunnel section, each beam 25 is located between two isolation piles 26 in each row of isolation piles 26, so that a beam 25 is constructed between two isolation piles 26 in each row of isolation piles 26, and the reinforcement 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 plurality of cross beams 25 are all located on the same plane, so as to form a frame structure on a plane, and stability is good.

In this embodiment, the cross section of the pile body of the isolation pile 26 is circular, and the diameter of the pile body of the isolation pile 26 is 0.58 m-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 isolation piles 26 in front and back in each isolation wall 22 is 0.6 m-0.65 m;

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

In this embodiment, the distance between two adjacent spacer piles 26 in front and rear in each of the spacer walls 22 refers to the distance between the central axes of two adjacent spacer piles 26 in front and rear.

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

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

all the middle sleeve valve pipes 29 arranged in the to-be-isolated reinforced stratum are arranged in a plurality of rows from back to front, each row of the middle sleeve valve pipes 29 comprises middle sleeve valve pipes 29 arranged on the same tunnel cross section from left to right, and the middle sleeve valve pipes 29 in the front and back adjacent two rows of the middle sleeve valve pipes 29 are arranged in an staggered manner;

N side sleeve valve tubes 27 are uniformly distributed between two adjacent isolation piles 26 in front and back in each isolation wall 22, wherein n is a positive integer and is more than or equal to 1; all side sleeve valves 27 in each of the partition walls 22 are laid back-to-front along the longitudinal extension of the underpass tunnel segments.

In this embodiment, n=7.

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

In this embodiment, when the clear distance between the underpass tunnel section 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 near the underpass tunnel section and a far side bridge pile foundation far away from the underpass tunnel section, the underpass tunnel section is divided into a first underpass tunnel section with the clear distance smaller than d1 between the near side bridge pile foundations and a second underpass tunnel section with the clear distance larger than d1 between the near side bridge pile foundations, the number of the second underpass tunnel sections is two, and the two second underpass tunnel sections are respectively located at two sides of the first underpass tunnel section; when the shield tunneling machine is tunneling the first underpass tunnel segment, the shield tunneling machine is used for disturbing soil body on the periphery side of the bridge pile foundation 21 and increasing formation pressure, so that the distance between the front adjacent isolation piles 26 and the rear adjacent isolation piles 26 on two sides in the first underpass tunnel is 0.6-0.65 m, 1 side sleeve valve pipe 27 is arranged between the front adjacent isolation piles 26 and the rear adjacent isolation piles 26, slurry is injected into the side sleeve valve pipe 27 until the slurry injected into the side sleeve valve pipe 27 is diffused to be connected with the front adjacent isolation piles 26 and the rear adjacent isolation piles 26 to form a grouting reinforcement body, and the grouting reinforcement body is fixedly connected with the front adjacent isolation piles 26 into a whole to strengthen the strength of the isolation wall 22 on two sides of the first underpass tunnel; when the shield tunneling machine is tunneling the second underpass tunnel segment, the shield tunneling machine has small disturbance and formation pressure to the soil body on the periphery of the bridge pile foundation 21, so that the distance between the front and rear adjacent isolation piles 26 on two sides in the second underpass tunnel is 1 m-1.05 m, 2 side sleeve valve pipes 27 are arranged between the front and rear adjacent isolation piles 26, and slurry is respectively injected into the 2 side sleeve valve pipes 27 until the slurry injected into the 2 side sleeve valve pipes 27 is diffused to be connected with the front and rear adjacent isolation piles 26 to form the grouting reinforcement body, and the grouting reinforcement body is fixedly connected with the front and rear adjacent isolation piles 26 into a whole, so that 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 side sleeve valve pipe 27 is faster than that of the isolation piles 26, and the construction efficiency can be effectively improved by arranging the grouting reinforcement body between the front and rear adjacent isolation piles 26 to connect the adjacent two isolation piles 26.

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

In this embodiment, all the middle sleeve valve tubes 29 in the slurry consolidated body 23 are arranged in a quincuncial shape and are uniformly arranged, 42.5-level 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 soil surrounding the arrangement positions of the middle sleeve valve tubes 29, two adjacent middle sleeve valve tubes 29 are fastened and connected into a whole after the slurry in two adjacent middle sleeve valve tubes 29 are mixed with the soil surrounding the middle sleeve valve tubes, and grouting is performed on all the middle sleeve valve tubes 29, so that the slurry in all the middle sleeve valve tubes 29 is mixed with the soil surrounding the middle sleeve valve tubes to form the slurry consolidated body 23, and the formed slurry consolidated body 23 has good uniformity, so that the influence on tunneling of a shield tunneling machine is avoided.

The isolation and reinforcement method for the overpass under the water-rich sand layer shield tunnel shown in fig. 10, with reference to fig. 8 and 9, comprises the following steps:

In this embodiment, when the measurement and paying-off are performed on the down-going tunnel section in step A1, the measurement and paying-off are performed on the tunnel centerline of the down-going tunnel section according to the pre-designed tunnel centerline of the down-going tunnel section; in the step A1, when the two partition walls 22 are measured, according to the measurement paying-off result of the central line of the tunnel of the underpass tunnel section, the central lines of the walls of the two partition walls 22 are measured and paying-off.

In this embodiment, during actual construction, firstly, the isolation pile 26 is constructed, the grouting reinforcement is constructed after the concrete poured into the isolation pile 26 is final-set, the crown beam 24 is constructed after the slurry of the grouting reinforcement is final-set, the slurry reinforcement 23 is constructed after the concrete poured into the crown beam 24 is final-set, the multi-channel cross beam 25 is constructed between the two crown beams 24 after the slurry in the slurry reinforcement 23 is final-set, and the construction of the isolation reinforcement structure is completed after the cross beam 25 is final-set.

In this embodiment, in the step A2, when any one of the partition walls 22 is constructed, a plurality of the partition piles 26 in the partition wall 22 are constructed from the front side and the rear side to the middle portion; in the construction process of the isolation piles 26, grouting and reinforcing are respectively carried out on stratum between the front and rear adjacent isolation piles 26 from the front side and the rear side to the middle by adopting sleeve valve pipes;

In the step A3, when any crown beam 24 is constructed, the crown beam 24 is constructed from the front side and the rear side to the middle;

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

all the middle sleeve valve pipes 29 arranged in the to-be-isolated reinforced stratum are arranged in a plurality of rows from back to front, each row of the middle sleeve valve pipes 29 comprises middle sleeve valve pipes 29 arranged on the same tunnel cross section from left to right, and the middle sleeve valve pipes 29 in the front and back adjacent two rows of the middle sleeve valve pipes 29 are arranged in a staggered manner;

in the step A4, grouting reinforcement is carried out on the stratum to be isolated and reinforced, grouting reinforcement is carried out from the left side and the right side to the middle part symmetrically for a plurality of times, grouting is carried out from the front side and the rear side to the middle part symmetrically for a plurality of 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 reinforced, grouting reinforcement is performed from the left side and the right side to the middle portion symmetrically for multiple times, grouting is performed from the front side and the rear side to the middle portion symmetrically for multiple times, a quadrilateral grouting area is formed during 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 the middle sleeve valve pipes 29 on the front side and the rear side, grouting is performed on the middle sleeve valve pipes 29 in the formed first quadrilateral area, blocking is performed on grouting liquid in the first quadrilateral area during grouting of the middle sleeve valve pipes 29 in the first quadrilateral area, and the situation that the slurry diffusion range during grouting of the middle sleeve valve pipes 29 in the first quadrilateral area exceeds a preset slurry diffusion range is avoided, so that 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 tunnel section is constructed, after the construction of both tunnel holes of the non-underpass viaduct tunnel section is completed, the construction of the communication channel 2 is performed;

the constructed connecting channel 2 is a undercut tunnel which is connected between 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 opening section and a front tunnel section positioned at the front side of the tunnel opening section;

As shown in fig. 7, when constructing the constructed communication channel 2, the method includes the steps of:

step B1, erecting a temporary support structure of the duct piece: a group of segment temporary supporting structures are respectively erected in the two shield tunnels 1, and the two groups of segment temporary supporting structures are respectively positioned at the front side and the rear side of the constructed connecting channel 2, as shown in fig. 5 in detail;

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

step B2, stratum pre-reinforcement: referring to fig. 2, 3 and 4, the stratum where the communication channel 2 is constructed is pre-reinforced, and the process is as follows:

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

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

And B3, precipitation construction: dewatering the stratum where the constructed communication channel 2 is located, and lowering the underground water level to the position below the excavation outline of the constructed communication channel 2;

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

step B5, excavating a channel hole section and performing primary support construction: b4, excavating the opening section of the constructed communication channel 2 from back to front through the tunnel portal 3; in the process of excavation, primary support is synchronously carried out from back to front;

and B6, excavating a front tunnel section and performing primary support construction: excavating the front tunnel section of the constructed connecting channel 2 from back to front; and in the excavation process, synchronously carrying out primary support on the front tunnel section formed by excavating from back to front.

In this embodiment, after the whole grouting reinforcement of the tunnel stratum in the step B22 is completed, the front and rear end strata of the constructed connecting tunnel 2 need to be respectively supplemented and grouting reinforced by the advance small guide pipe 8 arranged in the step B21, so as to obtain a tunnel end stratum grouting reinforcement structure, and the tunnel end stratum grouting reinforcement structure and the sleeve valve pipe grouting reinforcement structure in the step B22 are fastened and connected into a whole.

In this embodiment, when the precipitation construction is performed in step B3, precipitation is performed by using two rows of precipitation wells respectively arranged on the left and right sides of the constructed communication channel 2.

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

In the embodiment, after the formation pre-reinforcement in the step B2 is completed and before the precipitation construction in the step B3 is performed, a vertical transportation channel 17 is constructed at the rear end of the front tunnel section 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 hole section is excavated from back to front, the hole section is communicated with the vertical transportation channel 17;

in the step B6, the front tunnel section is excavated from the rear to the front by using the vertical transport channel 17, and the front tunnel section is initially supported from the rear to the front by using the vertical transport channel 17.

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

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

When the vertical transportation channel 17 is actually constructed, the designed elevation of the portal 3 at the rear end of the constructed communication channel 2 is obliquely upwards to the designed vault range of the constructed communication channel 2, the ending position of the gradual excavation transition section (namely the portal transition section or the portal transition section) is determined, the vertical transportation channel 17 which is downwards communicated to the inside of the constructed communication channel 2 from the ground is constructed at the corresponding position on the ground by adopting a rotary drilling pore-forming method, then the steel protection cylinder 18 is lowered in the vertical transportation channel 17, the bottom of the steel protection cylinder 18 extends below the initial supporting and erecting position of the vault of the constructed communication channel, the top of the steel protection cylinder 18 is higher than the ground, a gap exists between the steel protection cylinder 18 and the vertical transportation channel 17, the gap between the steel protection cylinder 18 and the vertical transportation channel 17 is tightly backfilled by adopting concrete, and then the steel protection cylinder 18 is fixed on the ground.

It should be noted that, since the transition section of the gradual excavation is required to be excavated reversely in the latter stage, the vertical transportation channel 17 cannot be disposed therein, and the earthwork excavated in order to satisfy the constructed connecting channel 2 can be transported out in time, so that the vertical transportation channel 17 is disposed at the position where the transition section of the gradual excavation ends. The vertical transportation channel 17 is constructed before the constructed communication channel 2 is excavated by earth and stone, so that the stability of the constructed communication channel 2 can be effectively ensured, and the possibility of collapse is reduced; the vertical conveying channel 17 is used for carrying out outward transport on the earthwork stones excavated by the constructed connecting channel 2, is also used for hoisting underground required materials, does not need to carry out the excavated earthwork stones through the shield tunnel 1, and effectively accelerates the 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 pile casing 18 extends into 300-400 m below the arch crown primary support erection position of the constructed communication channel 2, the top of the steel pile casing 18 is 500-600 mm above the ground, and the wall thickness of the steel pile casing 18 is 10-15 mm.

The outer diameter of the steel pile casing 18 is 1 m-1.3 m, the outer diameter of the steel pile casing 18 is smaller than the aperture of the vertical transportation channel 17, the steel pile casing 18 is convenient to install and concrete is convenient to reinforce, and C15 concrete is used for concrete for filling gaps between the steel pile casing 18 and the vertical transportation channel 17. 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 out of the ground by 500mm, and the bottom end of the steel casing is 300mm below the tunnel primary support structure of the front tunnel section.

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

Each group of segment temporary support structures comprises 2N segment temporary support structures for temporarily supporting shield segment rings in the tunnel segment to be reinforced one by one, the structures of the 2N segment temporary support structures in each group of segment temporary support structures are the same and are distributed from back to front along the longitudinal extension direction of the distributed shield tunnel 1, each segment temporary support structure is supported in one shield segment ring, and each segment temporary support 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;

each group of duct piece temporary supporting structures is divided into two duct piece temporary supporting groups which are respectively positioned at two sides of the tunnel junction area, and each duct piece temporary supporting group comprises N duct piece temporary supporting structures.

In this embodiment, each segment temporary supporting structure is supported at the middle part of the inner side of one shield segment ring. Thus, the spacing between two adjacent segment temporary support structures in each segment temporary support group is the same as the spacing 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 supporting structure for carrying out full-section support on the shield segment ring.

In this embodiment, as shown in fig. 5, the annular supporting structure includes a plurality of circular arc-shaped supporting frames arranged on the same vertical surface along the circumferential direction, and a force application mechanism for applying prestress is disposed between two adjacent circular arc-shaped supporting frames, and a plurality of force application mechanisms in the annular 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 circular arc-shaped steel brackets 12 distributed along the circumferential direction, and two adjacent circular arc-shaped steel brackets 12 in each circular arc-shaped support frame are connected in a hinged manner; a support 13 is arranged between each arc-shaped steel bracket 12 and the supported shield segment ring.

For the convenience of connection, two adjacent arc-shaped steel brackets 12 in each arc-shaped supporting frame are connected through a hinging seat 11. And a telescopic connecting piece 10 is connected between two adjacent circular arc-shaped supporting frames in the circular ring-shaped supporting 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-steel, so that the processing effect is good and the supporting effect is better.

To ensure the supporting force, in this embodiment, each of the force applying mechanisms includes a plurality of screw jacks 14. In actual construction, the number of screw jacks 14 included in each of the force applying mechanisms may be adjusted accordingly, as desired.

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

In the actual construction process, the temporary support structure of the duct piece is combined with the stratum reinforcing structure at the end part of the channel outside the shield tunnel 1, and effective reinforcing supports are formed at the inner side and the outer side of the joint of the shield tunnel 1 and the constructed connecting channel 2, so that the duct piece deformation, cracking and damage caused by prestress concentration due to duct piece opening at the portal can be effectively prevented, the reinforcing support structure is reinforced at the outer part of the duct piece, and the reinforcing support structures at the inner side and the outer side are combined together, so that the reinforcing effect of the shield duct piece at the portal of the connecting tunnel is better, and the construction is safer.

In this embodiment, a distance between two adjacent duct piece temporary support structures in front and back in each duct piece temporary support group is 1.5m, and 8 rings of duct piece temporary support structures are arranged in each shield tunnel 1.

In order to further ensure the reinforcing effect, a plurality of segment temporary supporting structures in each segment temporary supporting structure are all fastened and connected into a whole through a plurality of longitudinal connecting pieces distributed along the circumferential direction, and each segment temporary supporting structure is distributed along the longitudinal extending direction of the shield tunnel 1. In this embodiment, the longitudinal connecting piece is longitudinal connection shaped steel, the longitudinal connecting piece with the arc shaped steel support 12 fastening connection of section of jurisdiction temporary support structure just is connected 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-steel, and the circumferential distance between every two adjacent longitudinal connecting pieces is 2m.

During actual construction, when the pipe piece temporary supporting structures are used for reinforcing, after a plurality of pipe piece temporary supporting structures in each group of pipe piece temporary supporting structures are erected and all pipe piece temporary supporting structures are fastened and connected into a whole through the longitudinal connecting pieces, a screw jack 14 is used for applying prestress, and the pressure of each jack is preset to be 100kN.

In this embodiment, in the 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 from front to back, and the front tunnel section is formed by excavating from back to front; b5, when the tunnel entrance section is subjected to tunnel entering construction, excavating the tunnel entrance section for the first time from back to front, and obtaining an excavation-shaped tunnel entrance transition section; the cross section of the tunnel portal transition section is smaller than that of the front tunnel section, and the cross section of the tunnel portal transition section is gradually increased from back to front;

referring to fig. 6 and 10, in the process of excavating the hole section from back to front in step B5, a plurality of rows of grouting pipes 15 are pre-buried in the arch part of the hole transition section from back to front synchronously, a plurality of rows of grouting pipes 15 are arranged from back to front, each row of grouting pipes 15 comprises a plurality of grouting pipes 15 arranged along the excavation contour line of the arch part of the hole transition section, and a plurality of grouting pipes 15 in each row of grouting pipes 15 are arranged on the same cross section of the constructed communication channel 2; each grouting pipe 15 is gradually inclined upwards from back to front;

And B5, when the primary support is carried out from back to front, carrying out primary support on the opening transition section formed by digging from back to front, and obtaining a temporary primary support structure of the opening transition section.

In actual construction, the cross-sectional structures and the dimensions of the tunnel portal section and the front tunnel section are the same as those of the pre-designed constructed connecting passage 2. The length of the grouting pipe 15 is 2 m-3 m.

In this embodiment, the temporary primary support structure includes a plurality of steel arches 16 supporting the opening section from back to front and an anchor net spraying support structure supporting the opening section.

In order to improve the reinforcement effect and simplify the construction, the grouting pipe 15 is a small advance conduit for grouting reinforcement of the arch stratum of the tunnel portal section.

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

In this embodiment, after the front tunnel segment is excavated in step B6, the shield segment ring located at the front side of the constructed connection channel 2 is cut and removed, so as to obtain the front tunnel portal of the constructed connection channel 2.

In the step B6, after the front tunnel section is excavated, advanced support is carried out on the arch stratum of the tunnel portal transition section through a plurality of rows of grouting pipes 15; then, breaking the temporary primary support structure in the opening transition section from front to back;

In the process of breaking the temporary primary support structure from front to back, carrying out secondary excavation on the hole section from front to back to obtain the excavation-shaped hole section; and in the process of carrying out secondary excavation on the hole section from front to back, carrying out primary support on the hole section formed by excavation synchronously from back to front.

In the embodiment, in the process of carrying out secondary excavation on the opening section from front to back, an advanced small guide pipe is adopted to carry out advanced support on the arch wall of the opening section.

And B4, when the duct piece is cut and removed, cutting and removing the shield duct piece ring positioned at the rear side of the constructed connecting channel 2 to obtain a portal 3 at the rear end of the constructed connecting channel 2, wherein the structure and the size of the portal 3 are the same as those of the cross section of the pre-designed constructed connecting channel 2. Thus, the portal 3 at the rear end of the constructed connecting passage 2 is cut and removed twice before and after.

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

In this embodiment, the length of the hole section is 2m, and the length of the hole section can be adjusted accordingly according to specific needs.

Before the actual construction of the tunnel portal section, firstly carrying out predicted quantity line drawing on the tunnel portal 3 to be dismantled, then cutting the duct piece at the tunnel portal 3 and starting to excavate the earth and stone for the constructed connecting channel 2. In this embodiment, the earth and stone side excavation of the constructed communication channel 2 adopts a step-up and step-down method, which is favorable for the stability of the excavation surface, is suitable for water-rich sand areas, and ensures the construction safety.

In this embodiment, when the tunnel portal section is excavated, the slope is firstly excavated from the design elevation of the tunnel portal 3 to the design vault of the constructed communication channel 2, and the temporary primary support of the gradual excavation transition section (i.e. the tunnel portal section) is formed by timely performing the primary support, meanwhile, the grouting pipe 15 of the transition section is pre-buried, the external angle of the grouting pipe 15 pre-buried in the tunnel 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 external angle of the grouting pipe 15 is larger than the slope angle of the slope of the gradual excavation transition section, the temporary primary support of the gradual excavation transition section is broken from the opposite direction of the excavation after the primary support of the constructed communication channel 2 is penetrated, the gradual excavation transition section is excavated to the design requirement, and the permanent primary support structure is implemented.

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

In this embodiment, the constructed communication channel 2 is located below the groundwater 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 ground subsidence of the area where the two shield tunnels 1 are positioned and the like in the precipitation construction process, the stratum of the construction area where the constructed connecting channel 2 is positioned is not subjected to precipitation before the stratum is subjected to grouting reinforcement by adopting the method.

The grouting reinforcement is carried out by adopting the method, the construction is simple and convenient, the reinforcement quality is convenient to control, after the grouting reinforcement is finished, the reinforced stratum and the shield segment in the constructed shield tunnel 1 are fixedly connected into a whole, the stratum reinforcement effect of the area where the constructed communication channel 2 is positioned is further improved, the structural stability of the shield tunnel 1 can be effectively improved, and the earth surface subsidence of the shield tunnel 1 can be effectively limited or even avoided.

According to the method, the pre-reinforced stratum of the connecting channel 2 in the water-rich sand layer area is divided into a plurality of reinforced areas, and stratum pre-reinforcement construction is carried out on different reinforced areas by adopting different reinforcement methods, so that stable reinforcement of the pre-reinforced stratum of the connecting channel 2 is realized, a foundation is laid for excavation of the subsequent connecting channel 2, collapse risk during excavation of the connecting channel 2 is reduced, and construction safety is guaranteed.

In this embodiment, the constructed communication channel 2 is arranged horizontally, and the grouting end of the advance small pipe 8 is positioned below the vault of the constructed communication channel 2.

And the two shield tunnels 1 are connected with the constructed connecting passage 2, and the areas are provided with the portal 3 of the constructed connecting passage 2.

After grouting reinforcement in the step B21 is completed, the stratum at the front end and the back end of the constructed connecting channel 2 is symmetrically reinforced through two symmetrically arranged stratum reinforcing structures at the end of the channel, and meanwhile, two symmetrical grouting stopping rings are formed by the two stratum reinforcing structures at the end of the channel, so that slurry backflow in the whole grouting reinforcement grouting process of the channel stratum in the step B22 can be prevented, underground water flows at the front end and the back end of the constructed connecting channel 2 can be effectively intercepted, the structural stability of the joint between the constructed connecting channel 2 and the two shield tunnels 1 is ensured, and construction safety is ensured.

It should be noted that, passageway tip stratum reinforced structure wraps up the stratum of connection passageway 2 gradual change excavation changeover portion, and the stratum that is located gradual change excavation changeover portion top when preventing gradual change excavation changeover portion back dig consolidates inadequately, guarantees the safety of follow-up connection passageway 2 excavation at any moment.

In this embodiment, referring to fig. 1, fig. 2 and fig. 3, when grouting and reinforcing the stratum at the end of the tunnel in step B21, a group of advance small ducts 8 are firstly formed in the stratum at the front end and the rear end of the constructed connecting tunnel 2 through two shield tunnels 1, and the two groups of advance small ducts 8 are symmetrically arranged; grouting and reinforcing stratum at the front end and the rear end of the constructed communication channel 2 respectively through two groups of small advance guide pipes 8;

each group of the advance small guide pipes 8 comprises a plurality of advance small guide pipes 8 which are uniformly distributed on the same plane, and the plurality of the advance small guide pipes 8 in each group of the advance small guide pipes 8 are distributed from left to right along the width direction of the constructed communication channel 2 and are distributed in parallel; each small leading guide pipe 8 is arranged along the longitudinal extending direction of the constructed communication channel 2, one end of each small leading guide pipe 8 is a stratum driving end driven into the stratum, and the other end of each small leading guide pipe is a grouting end; each of the small advance guide pipes 8 is gradually inclined upward from the grouting end to the stratum driving end;

And B23, performing supplementary grouting reinforcement on stratum at the front end and the rear end of the constructed communication channel 2 through two groups of the advance small guide pipes 8 respectively.

In actual construction, the two groups of the advance small guide pipes 8 are arranged simply and conveniently, and the construction is convenient.

The stratum driving end of the advance small guide pipe 8 is positioned above the vault of the constructed communication channel 2, and the vertical distance between the stratum driving end and the vault is 0.5 m-2 m.

In this embodiment, the vertical distance between the ground driving end of the leading small pipe 8 and the dome of the constructed communication passage 2 is 1.5m. 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 driving end of the advance small guide pipe 8 and the vault of the constructed communication channel 2 can be correspondingly adjusted according to specific requirements.

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

In this embodiment, the constructed communication channel 2 is laid horizontally.

When the tunnel reinforcement sleeve valve pipe 4 is reinforced by the tunnel reinforcement sleeve valve pipe 4 which is arranged by the opposite side portal 3, the grouting effect of the stratum driving end is poor due to the longer length of the tunnel reinforcement sleeve valve pipe 4, and the two factors act together to ensure that the unset slurry is easily flushed away by water flow when the tunnel end stratum is reinforced by grouting of the tunnel reinforcement sleeve valve pipe 4, so the grouting effect of the tunnel reinforcement sleeve valve pipe 4 is very poor; furthermore, because the position is positioned at the top of the tunnel portal 3 and is close to the outer side wall of the segment of the shield tunnel 1, collapse risks exist at the position where the connecting channel is excavated, the reinforcing effect of the stratum can be guaranteed only by the extra grouting of the advanced small guide pipe 8, and the excavation safety of the subsequent connecting channel is guaranteed.

After grouting reinforcement of the stratum at the end part of the channel is completed in the step B21, the two stratum reinforcement structures at the end part of the channel are constructed, and have the following beneficial effects: the first structure can effectively enhance the reinforcing effect of the grouting reinforcement of the subsequent sleeve valve pipe, and the two stratum reinforcing structures at the end parts of the channel can be used as grouting stopping structures for grouting reinforcement of the sleeve valve pipe in the step B22, so that leakage is prevented, the grouting density and the grouting pressure of grouting of the sleeve valve pipe are effectively improved, and the grouting reinforcement strength of the sleeve valve pipe 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, the shield segments at the joint between the two side shield tunnels 1 and the constructed connecting channel 2 are effectively reinforced, so that the construction quality of the joint between the constructed connecting channel 2 and the two side shield tunnels 1 can be effectively improved; fourthly, groundwater above the joint between the shield tunnel 1 and the constructed connecting channel 2 can be effectively intercepted, so that the construction quality of the joint between the shield tunnels 1 and the constructed connecting channel 2 on two sides 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; fifth, two stratum reinforcing structures at the end parts of the channel and sleeve valve pipe grouting reinforcing structures can be fastened and connected into a whole to form an integral reinforcing structure which is fastened and connected between two shield tunnels 1, so that the integrity and stability of the shield tunnels 1 at the two sides and the constructed connecting channel 2 can be effectively enhanced, and the long-term use effect is ensured; sixth, as the stratum at the two ends of the constructed connecting channel 2 is a reinforced weak area for grouting reinforcement of the subsequent sleeve valve pipe, the defect of grouting reinforcement of the subsequent sleeve valve pipe can be effectively overcome through grouting reinforcement of the stratum at the end part of the channel.

After the grouting reinforcement of the sleeve valve pipe in the step B22 is completed, the sleeve valve pipe grouting reinforcement structure integrally and effectively reinforces the stratum where the constructed communication 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 communication channel 2 is located in a full range can be met, and the integral reinforcement effect is very good; the arrangement space of the advance small guide pipes 8 in the stratum at the two ends of the constructed communication channel 2 is smaller, so that grouting density and grouting reinforcement effect in the stratum at the two ends of the constructed communication channel 2 can be effectively ensured; while the leading small guide pipes 8 in the middle part of the constructed communication channel 2 are arranged at larger intervals, the leading small guide pipes 8 on the front side and the rear side of the middle part of the constructed communication channel 2 are mutually intersected, so that the grouting density and grouting reinforcement effect in the stratum can be ensured as well.

And (3) 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.

In order to control the process simply and conveniently, when grouting reinforcement is carried out on the stratum at the end part of the channel in the step B21, stopping grouting when grouting pressures of all the leading small pipes 8 in the two groups of leading small pipes 8 reach P1, and completing 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 leading small pipes 8 in the two groups of leading 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 0.5MPa to 0.6MPa.

In this example, p1=0.75 MPa and p2=0.55 MPa. In actual construction, the values of P1 and P2 can be correspondingly adjusted according to specific requirements.

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

the number of the advance small pipes 8 included in each group of the advance small pipes 8 is 2M, wherein M is a positive integer and M is more than or equal to 3; the number of the leading small pipes 8 positioned at the left and right sides of the central line of the tunnel of the constructed communication channel 2 in each group is M;

in step B21 and step B23, grouting is performed symmetrically from the middle to the left and right sides, respectively, when grouting is performed through any group of the advance small pipes 8.

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

In this embodiment, m=4. And d=16m.

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

In practical construction, all the advance small pipes 8 in each group of the advance small pipes 8 have the same size and the same layout height. The included angles between the plurality of the leading small pipes 8 in each group of the leading small pipes 8 and the horizontal plane are the same, and the grouting ends of all the leading small pipes 8 in each group of the leading small pipes 8 are positioned on the same horizontal plane.

In this embodiment, the included angle between the small advancing pipe 8 and the horizontal plane (i.e., the external inserting angle of the small advancing pipe 8) is 15 ° to 30 °.

In this embodiment, the advance small conduit 8 laid in the step B21 is a grouting pipe driven into the stratum through a pipe piece lifting hole on a shield pipe piece ring in the shield tunnel 1.

It should be noted that, the advanced small conduit 8 is arranged through the pipe piece lifting hole, so that 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 stability of the tunnel structure are ensured.

In this embodiment, before grouting reinforcement of the sleeve valve pipe in the step B22, the front and rear sleeve valve pipe grouting structures are constructed through the two shield tunnels 1, and the two sleeve valve pipe grouting structures are symmetrically arranged and are 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 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 pipes 4 in one sleeve pipe grouting structure crosses at least one of the channel-reinforcing sleeve pipes 4 in the other sleeve pipe grouting structure.

In this embodiment, the value of L is 3. Thus, the formation 5 to be reinforced is a formation within 3 meters outside the excavated contour 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 to be reinforced 5 is divided into a overlapping reinforcing region 6, an outer grouting weak region 9 located at the outer side of the overlapping reinforcing region 6, and two end grouting weak regions 7 located at the front and rear sides of the overlapping reinforcing region 6, where the overlapping reinforcing region 6 is a region where grouting regions of 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 reinforcing area 6, and the advance small guide pipe 8 arranged in the step B21 is positioned in the end grouting weak areas 7; the two end grouting weak areas 7 are all advanced small guide pipe grouting reinforcing areas reinforced by adopting an advanced small guide pipe 8, and the overlapping reinforcing areas 6 and the two end grouting weak areas 7 form a core reinforcing area;

The stratum where the constructed connecting channel 2 is located in the core reinforcing area.

In actual construction, all the leading small ducts 8 in each group of the leading small ducts 8 are located in the same end grouting weak area 7.

It should be noted that, the outer grouting weak area 9 and the end grouting weak area 7 are non-overlapping areas of grouting areas of the two sleeve valve pipe grouting structures, and because the end grouting weak area 7 is more prone to collapse, the reinforcing effect of the non-overlapping areas of grouting areas of the two sleeve valve pipe grouting structures can meet the formation reinforcing requirement of the outer grouting weak area 9 but cannot meet the formation reinforcing requirement of the end grouting weak area 7, and therefore the end grouting weak area 7 needs to be additionally subjected to grouting reinforcing construction by the advance small guide pipe 8.

The outside grouting weak area 9 does not carry out grouting reinforcement additionally when stratum is pre-reinforced, construction period is saved, the outside grouting weak area 9 can be reinforced again through the advance small guide pipes which are arranged on the vault of the channel in a beating mode and are parallel to each other when the communication channel 2 is initially supported, and stability of the communication channel is guaranteed.

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

Each sleeve valve pipe grouting structure comprises a plurality of groups of upper sleeve valve pipes for reinforcing a 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, wherein the plurality of groups of upper sleeve valve pipes and the plurality of groups of lower sleeve valve pipes are all distributed from inside to outside; each group of upper sleeve valve pipes comprises a plurality of sleeve valve pipes 4 for channel reinforcement, which are distributed along the excavation outline of the upper hole body, and the external insertion angles of the sleeve valve pipes 4 for channel reinforcement of a plurality of groups of upper sleeve valve pipes are gradually increased from inside to outside; each group of lower sleeve valve pipes comprises a plurality of sleeve valve pipes 4 for channel reinforcement, which are 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 a plurality of groups of the lower sleeve valve pipes are gradually increased from inside to outside;

in the process of grouting reinforcement of the sleeve valve pipe in the step B22, grouting reinforcement is carried out from outside to inside when grouting reinforcement of the sleeve valve pipe is carried out through any sleeve valve pipe grouting structure.

Wherein, 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 4 for reinforcing the passage is not more than 30 °.

In this embodiment, the two areas where the shield tunnel 1 is connected to the constructed connecting channel 2 are tunnel connection areas, and the shield segment rings of the tunnel connection areas in the two shield tunnels 1 are provided with a plurality of sleeve valve tube mounting holes for the channel reinforcement sleeve valve tubes 4 to be punched.

And the tunnel connection areas in the two shield tunnels 1 are provided with a portal 3 of the constructed communication channel 2, the opening area of the portal 3 on the shield segment in the shield tunnel 1 is a portal opening area, and the sleeve valve tube mounting hole is positioned in the portal opening area.

In order to ensure the integrity of the segment of the shield tunnel 1 except the region where the portal is opened, the sleeve valve tube 4 for reinforcing the tunnel when the connecting channel 2 is pre-reinforced in the stratum can only be arranged in the stratum by the region where the portal is opened, and the maximum elevation angle of the sleeve valve tube 4 for reinforcing the tunnel is limited by the limit, so that the sleeve valve tube 4 for reinforcing the tunnel cannot go deep into the joint region between the shield tunnel 1 and the connecting channel 2, thereby the grouting of the sleeve valve tube 4 for reinforcing the tunnel cannot completely cover the preset stratum 5 to be reinforced by the connecting channel 2, and the weak region 7 for grouting at the end part appears.

In this embodiment, the external insertion angle of the sleeve 4 for reinforcing the outermost channel above the tunnel portal 3 is in the range of 25 ° to 30 °.

When the constructed communication channel 2 is actually excavated, the construction is performed from the rear to the front along the longitudinal extending 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, and the portal opening area positioned in the shield tunnel 1 at the rear side of the constructed connecting channel 2 is rectangular and has the same structure and size as the portal 3. The width of the cavity door 3 positioned at the rear side of the constructed communication channel 2 is smaller than the excavation width of the constructed communication channel 2, and the height of the cavity door 3 is smaller than the excavation height of the constructed communication channel 2. At the same time, the roof of the portal 3 at the rear side of the constructed communication channel 2 is lower than the dome of the constructed communication channel 2. The grouting end of the leading small conduit 8 is positioned above the tunnel portal 3, and the grouting end of the leading small conduit 8 is positioned below the vault of the constructed communication channel 2.

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

In the step B22, a conventional sleeve grouting reinforcement method is used for sleeve grouting. The length of the constructed connecting channel 2 is 10 m-20 m. In the embodiment, the buried depth of the constructed communication channel 2 is 11.55m, the length is 15.80m, the section size is 3.80m multiplied by 4.57m, the mixed filling soil, the silt and the middle sand are distributed from top to bottom, the stable water level buried depth of the underground water is between 10.30m and 11.80m, and the cavity of the constructed communication channel 2 is positioned in the water-rich middle sand layer.

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

In this embodiment, the small advance pipe 8 is a steel pipe with a diameter Φ50mm and a length of 2 m. The grout injected into the small advance pipe 8 is the same as the grout injected into the sleeve valve tube 4 for reinforcing the passage.

In summary, when grouting is performed in the step B21, when grouting is performed in the step B22 and when supplementary grouting is actually performed, grouting is performed in a hole (namely, in a tunnel hole of the shield tunnel 1), grouting is simple and convenient, grouting reinforcement is not needed from outside the hole (namely, the ground), construction cost can be reduced, construction period is saved, the problems that the ground is greatly influenced, construction difficulty is high, input cost is high, construction period cannot be effectively ensured and the like in the existing jet grouting pile reinforcement process can be effectively avoided, and the stratum where the constructed communication channel 2 is located can be effectively reinforced while the stratum where the two shield tunnels 1 are connected with the constructed communication channel 2 is simultaneously reinforced; meanwhile, the shield tunnel 1 can be effectively reinforced, and particularly the shield segment ring at the joint between the two shield tunnels 1 and the constructed connecting channel 2 can be effectively reinforced. In addition, the advance small guide pipe 8 is inserted into the stratum through the pipe piece lifting hole, and the sleeve valve pipe 4 for channel reinforcement is inserted into the stratum through the tunnel portal opening area, so that the advance small guide pipe 8 and the sleeve valve pipe 4 for channel reinforcement are arranged so as not to 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 stability of the tunnel structure are ensured.

In the embodiment, the excavation of the constructed connecting channel 2 adopts a step-up and step-down method, and the construction of the primary support and the secondary lining adopts a conventional construction scheme.

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

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

The foregoing description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and any simple modification, variation and equivalent structural changes made to the above embodiment according to the technical substance of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A construction method of a shield tunnel of a water-rich sand layer is characterized by comprising the following steps: the constructed tunnel is a double-hole tunnel and is an undercut 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 construction tunnel comprises a down-going viaduct tunnel section and a non-down-going viaduct tunnel section connected with the down-going viaduct tunnel section, wherein one tunnel hole of the down-going viaduct tunnel section is penetrated by an existing viaduct and is a down-going tunnel section, and two tunnel holes of the non-down-going viaduct tunnel section are communicated through a communication channel (2);

The isolation and reinforcement structure comprises two isolation walls (22) which are respectively arranged at the left side and the right side of the underpass tunnel section, and a slurry consolidation body (23) which is formed after grouting and reinforcement are carried out on a stratum to be reinforced and positioned between the two isolation walls (22) by adopting sleeve valve pipes, the underpass tunnel section is positioned in the slurry consolidation body (23), and the slurry consolidation body (23) and the two isolation walls (22) are fixedly connected into a whole; a crown beam (24) is arranged on each isolation wall (22), each isolation wall (22) is fixedly connected with the crown beam (24) arranged on the isolation wall into a whole, and the two crown beams (24) are fixedly connected with each other 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-situ reinforced concrete beams, and the slurry concretes (23), the two isolation walls (22) and each crown beam (24) are distributed along the longitudinal extending direction of the underpass tunnel section;

each isolation wall (22) comprises a plurality of isolation piles (26) which are vertically distributed, and each isolation pile (26) is a reinforced concrete filling pile; the isolation piles (26) in each isolation wall (22) are distributed from back to front along the longitudinal extending direction of the underpass tunnel section, the front and rear adjacent isolation piles (26) in each isolation wall (22) are all fastened and connected into a whole through grouting reinforcement bodies, and the grouting reinforcement bodies are reinforcement structures formed by grouting reinforcement of stratum between the front and rear adjacent isolation piles (26) through sleeve valve pipes;

When the non-underpass tunnel section is constructed, firstly, dewatering is carried out on stratum of a construction area where the non-underpass tunnel section is positioned, and then shield construction is carried out on the non-underpass tunnel section;

when the non-underpass viaduct tunnel section is constructed, constructing a communication channel (2) after the construction of two tunnel holes of the non-underpass viaduct tunnel section is completed;

the constructed connecting channel (2) is a subsurface tunnel which is connected between 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 opening section and a front tunnel section positioned at the front side of the tunnel opening section;

when constructing the constructed connecting channel (2), the method comprises the following steps:

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

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

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

Step B21, grouting and reinforcing stratum at the end part of the channel: carrying out advanced small-conduit grouting reinforcement on stratum at the front end and the rear end of a constructed connecting channel (2) through two shield tunnels (1), and forming a channel end stratum reinforcement structure at the outer sides of the two shield tunnels (1);

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

and B3, precipitation construction: dewatering the stratum where the constructed connecting channel (2) is located, and lowering the underground water level to the position below the excavation outline of the constructed connecting channel (2);

step B4, segment cutting and dismantling: cutting and dismantling shield segment rings at the hole entering position of the constructed connecting channel (2) in the shield tunnel (1) to obtain a portal (3) of the constructed connecting channel (2);

Step B5, excavating a channel hole section and performing primary support construction: b4, excavating the opening section of the constructed communication channel (2) from back to front through the opening (3) in the step; in the process of excavation, primary support is synchronously carried out from back to front;

and B6, excavating a front tunnel section and performing primary support construction: excavating the front tunnel section of the constructed connecting channel (2) from back to front; in the excavation process, synchronously carrying out primary support on the front tunnel section formed by excavating from back to front;

in the step B21, when grouting and reinforcing are carried out on stratum at the end part of the channel, a group of advance small guide pipes (8) are respectively arranged on stratum at the front end and the rear end of the constructed connecting channel (2) through two shield tunnels (1), and the two groups of advance small guide pipes (8) are symmetrically arranged; grouting and reinforcing stratum at the front end and the rear end of the constructed connecting channel (2) respectively through two groups of small advance guide pipes (8);

each group of the advance small guide pipes (8) comprises a plurality of advance small guide pipes (8) which are uniformly distributed on the same plane, and the plurality of the advance small guide pipes (8) in each group of the advance small guide pipes (8) are distributed from left to right along the width direction of the constructed communication channel (2) and are distributed in parallel; each small leading conduit (8) is arranged along the longitudinal extending direction of the constructed connecting channel (2), one end of each small leading conduit (8) is a stratum driving end driven into the stratum, and the other end of each small leading conduit is a grouting end; each leading small guide pipe (8) gradually inclines upwards from the grouting end to the stratum driving end;

After the whole grouting reinforcement of the passage stratum in the step B22 is finished, the strata at the front end and the rear end of the constructed connecting passage (2) are respectively subjected to supplementary grouting reinforcement through the advance small guide pipes (8) arranged in the step B21 to obtain a stratum grouting reinforcement structure at the end part of the passage, and the stratum grouting reinforcement structure at the end part of the passage and the sleeve valve pipe grouting reinforcement structure in the step B22 are fastened and connected into a whole;

when the supplementary grouting reinforcement is actually carried out, the two groups of leading small guide pipes (8) are used for respectively carrying out supplementary grouting reinforcement on stratum at the front end and the rear end of the constructed connecting channel (2);

before sleeve valve pipe grouting reinforcement is carried out in the step B22, the front sleeve valve pipe grouting structure and the rear sleeve valve pipe grouting structure are respectively constructed through the two shield tunnels (1), and the two sleeve valve pipe grouting structures are symmetrically distributed and are 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 sleeve valve pipes (4) for channel reinforcement in each sleeve valve pipe grouting structure are distributed radially; 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 channel-reinforcing sleeve (4) in one sleeve grouting structure crosses at least one channel-reinforcing sleeve (4) in the other sleeve grouting structure;

the stratum to be reinforced (5) is divided into a heavy overlaying and reinforcing area (6), an outer grouting weak area (9) positioned at the outer side of the overlaying and reinforcing area (6) and two end grouting weak areas (7) positioned at the front side and the rear side of the overlaying and reinforcing area (6), wherein the overlaying and reinforcing area (6) is an area where grouting areas of 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 reinforcing area (6), and the advance small guide pipe (8) arranged in the step B21 is positioned in the end grouting weak areas (7); the two end grouting weak areas (7) are all advanced small conduit grouting reinforcing areas reinforced by adopting advanced small conduits (8), and the overlapping reinforcing areas (6) and the two end grouting weak areas (7) form a core reinforcing area;

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

2. The construction method of the water-rich sand layer shield tunnel according to claim 1, wherein the construction method comprises the following steps: before precipitation is carried out on stratum of a construction area where the non-underpass tunnel section is located, a sleeve valve pipe is adopted to pre-reinforce stratum of the construction area where the non-underpass tunnel section is located, a plurality of grouting holes for grouting the sleeve valve pipe are formed in stratum of the construction area where the non-underpass tunnel section is located, and the grouting holes are vertically distributed and are distributed in a quincunx shape.

3. The construction method of the water-rich sand layer shield tunnel according to claim 1 or 2, wherein the construction method comprises the following steps: when isolating and reinforcing the stratum of the construction area where the underpass tunnel section is located, the method comprises the following steps:

step A1, measuring and paying off: according to a pre-designed tunnel central line of the underpass tunnel section, measuring and paying off are carried out on the underpass tunnel section, and measuring and paying off are respectively carried out on the two isolation walls (22);

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

when any one of the isolation walls (22) is constructed, firstly, respectively constructing a plurality of isolation piles (26) in the isolation wall (22), respectively grouting and reinforcing stratum between two adjacent isolation piles (26) before and after construction in the isolation wall (22) by adopting sleeve valve pipes to obtain grouting reinforcement bodies for construction molding, and after all the isolation piles (26) and all the grouting reinforcement bodies in the isolation wall (22) are constructed, obtaining the construction molding isolation wall (22);

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

Step A4, grouting and reinforcing the stratum to be isolated and reinforced: grouting reinforcement is carried out on a stratum to be isolated and reinforced between the two isolation walls (22) by adopting sleeve valve pipes, a slurry consolidation body (23) formed by construction is obtained, and the slurry consolidation body (23) is fixedly connected between the two isolation walls (22) formed by construction in the step A2;

and A5, construction of a cross beam: and (3) constructing a plurality of beams (25) above the slurry consolidated body (23) formed in the construction step A4, and enabling each beam (25) to be fixedly connected between two crown beams (24).

4. The construction method of the water-rich sand layer shield tunnel according to claim 1, wherein the construction method comprises the following steps: after the formation pre-reinforcement in the step B2 is completed and before the precipitation construction in the step B3 is carried out, constructing a vertical transportation channel (17) at the rear end of the front tunnel section from the ground from top to bottom, wherein the vertical transportation channel (17) is communicated with the inside of the constructed communication channel (2);

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

and B6, excavating the front tunnel section from back to front by using a vertical conveying channel (17) and performing primary support on the front tunnel section from back to front by using the vertical conveying channel (17) when the front tunnel section is excavated and the primary support is performed.

5. The construction method of the water-rich sand layer shield tunnel according to claim 1, wherein the construction method comprises the following steps: and B21, arranging an advance small guide pipe (8) which is a grouting pipe driven into the stratum through a pipe piece lifting hole on a shield pipe piece ring in the shield tunnel (1).