CN110645005A

CN110645005A - High-water-rich round gravel stratum earth pressure balance shield rapid tunneling construction method

Info

Publication number: CN110645005A
Application number: CN201911045578.8A
Authority: CN
Inventors: 徐赞; 陈先智; 杨小龙; 曲东魁; 孙权; 房有亮; 苏廷; 戴斌; 徐正帅; 向中华; 蒋学林; 杨伟伟
Original assignee: China Railway Development Investment Group Co Ltd
Current assignee: China Railway Development Investment Group Co Ltd
Priority date: 2019-10-30
Filing date: 2019-10-30
Publication date: 2020-01-03

Abstract

The invention discloses a high water-rich round gravel stratum earth pressure balance shield fast tunneling construction method, which comprises an existing tunnel, an upper tunnel and a lower tunnel which penetrate the existing tunnel from bottom to top, wherein the tunneling construction of the lower tunnel is firstly carried out, then the deep hole grouting treatment in the upper half hole of the lower tunnel is carried out, then the tunneling construction of the upper tunnel is carried out, and finally the deep hole grouting treatment in the upper half hole and the lower half hole of the upper tunnel is carried out. According to the invention, through reasonably designing the construction sequence of the upper and lower overlapped tunnels and the lower tunnel penetrating the existing tunnel, the tunnel of the upper and lower overlapped tunnels and the lower tunnel penetrating the existing subway line is subjected to rapid and efficient tunneling construction, and meanwhile, the tunneling construction settlement is effectively controlled within 6.5mm, so that the existing tunnel of the high water-rich pebble stratum is not influenced by the tunneling construction of the soil pressure balance shield of the lower tunnel.

Description

High-water-rich round gravel stratum earth pressure balance shield rapid tunneling construction method

Technical Field

The invention belongs to the technical field of tunnel construction, and particularly relates to a rapid tunneling construction method for a soil pressure balance shield of a high-water-rich round gravel stratum.

Background

With the development of underground space, shield technology has been widely applied in the engineering fields of subways, tunnels, municipal pipelines and the like. In various constructions in China, the types of shield machines are more and more, wherein the earth pressure balance type shield machines have excellent performance in subway construction such as Shanghai, Nanjing, Guangzhou and the like. A space formed by a cutter cutting space surface of the earth pressure balance type shield machine and a pressure-bearing partition plate behind the cutter cutting space surface is a soil bin, residue soil cut by the cutter in a rotating mode enters the soil bin through an opening in the cutter, the thrust of the jack is transmitted to the residue soil in the soil bin through the pressure-bearing partition plate, and the pressure of the residue soil acts on the excavation surface to offset the underground water pressure and the earth pressure at the excavation surface, so that balance is formed, and the stability of the excavation surface is kept. The spiral conveyer extends into the soil bin from the opening of the pressure-bearing partition plate to discharge soil, and the excavation propelling speed of the shield tunneling machine and the soil discharge amount of the spiral conveyer in unit time or the rotating speed of the spiral conveyer can influence the pressure of the soil bin.

In some areas, the tunnel mainly passes through a high-water-rich round gravel stratum, the stratum has high water content and large permeability coefficient, shield tunneling greatly disturbs the stratum, and a spiral conveyor is easy to have the phenomena of gushing and the like, so that the stability of the tunnel excavation surface is endangered; especially, more and more urban subway lines need to be penetrated through the existing subway lines, and the left and right holes of some newly-built subway lines need to be penetrated through the existing subway lines in an up-and-down overlapping mode, which puts higher requirements on shield tunneling construction, how to complete tunneling construction quickly and stably, and reducing stratum deformation caused in the construction process is a big difficulty in the field.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a rapid tunneling construction method for a soil pressure balance shield in a high water-rich round gravel stratum, which is used for performing rapid and efficient tunneling construction on a tunnel which is overlapped up and down and penetrates through the existing subway line and controlling the tunneling construction settlement within 6.5 mm.

The technical purpose of the invention is realized by the following technical scheme: a method for quickly driving a soil pressure balance shield in a high-water-rich gravel stratum comprises the steps of firstly driving a lower tunnel, then performing deep hole grouting treatment in the upper half hole of the lower tunnel, then performing driving construction of the upper tunnel, and finally performing deep hole grouting treatment in the upper half hole and the lower half hole of the upper tunnel.

According to the invention, the construction sequence of the upper and lower overlapped tunnels for passing through the existing tunnel downwards is reasonably designed, deep hole grouting treatment in the upper half tunnel is firstly carried out after the tunneling construction of the lower tunnel, the soil body on the upper part of the lower tunnel is reinforced, the stability of the upper tunnel construction is effectively ensured, the deep hole grouting treatment in the upper half tunnel and the lower half tunnel is carried out after the tunneling of the upper tunnel is finished, the tunneling construction settlement is effectively controlled within 6.5mm while the tunneling construction of the upper and lower overlapped tunnels for passing through the existing subway line downwards is carried out, and the existing tunnel in the high water-rich gravel stratum is not influenced by the tunneling construction of the soil pressure balance shield of the lower tunnel.

And the deep hole grouting treatment in the holes of the lower tunnel and the upper tunnel comprises inserting grouting pipes, injecting grout and plugging grouting holes. The grouting pipe is used for grouting deep holes in the hole, so that disturbance of grouting on the soil body can be reduced.

The slurry adopts cement-water glass double slurry and adopts static pressure grouting. And disturbance is reduced while grouting reinforcement is ensured.

And D, adopting a phi 48 steel pipe as a grouting pipe for grouting treatment of the deep holes in the holes, adopting smashing, flattening, laminating and sharpening treatment on the front end of the steel pipe, and opening a plurality of grout outlet holes on the pipe wall of the steel pipe except for 500mm from the grouting head end, wherein the diameter d of each grout outlet hole is 6mm, and the distance L between every two adjacent grout outlet holes along the axial direction of the steel pipe is 200 mm. The grouting pipe has simple structure, easy production and convenient use.

The grouting pipes of each grouting section of the lower tunnel comprise four first grouting pipes and three second grouting pipes, and the second grouting pipes are shorter than the first grouting pipes; the included angles between the four first grouting pipes and the horizontal plane are respectively 22.5 degrees, 45 degrees, 135 degrees and 157.5 degrees, and the included angles between the three second grouting pipes and the horizontal plane are respectively 67.5 degrees, 90 degrees and 112.5 degrees. And effectively reinforcing the soil body of the upper half part of the lower tunnel.

The grouting pipes of each grouting section of the upper tunnel comprise four third grouting pipes and three fourth grouting pipes which are positioned at the lower half part of the upper tunnel, and four fifth grouting pipes and three sixth grouting pipes which are positioned at the upper half part of the upper tunnel; the fourth grouting pipe and the second grouting pipe are equal in length, the third grouting pipe and the fifth grouting pipe are equal in length to the first grouting pipe, and the length of the sixth grouting pipe is between the length of the fifth grouting pipe and the length of the fourth grouting pipe; the included angles between the four third grouting pipes and the fifth grouting pipes and the horizontal plane are respectively 22.5 degrees, 45 degrees, 135 degrees and 157.5 degrees, and the included angles between the three fourth grouting pipes and the sixth grouting pipes and the horizontal plane are respectively 67.5 degrees, 90 degrees and 112.5 degrees. And effectively reinforcing the soil between the upper tunnel and the lower tunnel and the soil between the upper tunnel and the existing tunnel.

When the upper tunnel and the lower tunnel are subjected to tunneling construction, the method further comprises the following four stages:

the first stage is a test tunneling stage, and a construction parameter test of downward penetrating the existing tunnel is carried out on a ring pipe piece from 200 rings to 101 rings before downward penetrating the existing tunnel;

step two, a test parameter verification tunneling stage, and construction parameter optimization and correction are carried out from the front 100 ring pipe pieces to the front 1 ring pipe piece which penetrate through the existing tunnel;

step three, the construction is carried out in the tunneling stage of the existing tunnel construction according to the optimized and corrected construction parameters in the step two;

and fourthly, monitoring the displacement of the tunnel in the observation stage after the tunnel passes through.

The experimental tunneling stage and the experimental parameter verification tunneling stage are set in this way, and the reliability of the tunneling parameters can be ensured.

And injecting the gram mud effect into the first stage, the second stage and the third stage through radial holes of the shield shell, wherein injection points of the gram mud effect are at 1 o 'clock and 11 o' clock positions. The construction method of mud restraining effect is adopted, so that the gap between the excavation diameter and the shield body can be filled in time, and the control of settlement is facilitated.

In the construction of the first stage, the second stage and the third stage, synchronous grouting is carried out when the duct piece is separated from the shield tail, and each five-ring duct piece is sealed once by using cement-water glass double-slurry. Is favorable for controlling sedimentation and preventing water.

Has the advantages that: according to the invention, through reasonably designing the construction method of the upper and lower overlapped tunnels for passing through the existing tunnel, the tunneling construction settlement is effectively controlled within 6.5mm while the upper and lower overlapped and lower passed existing tunnels are rapidly and efficiently tunneled, so that the existing tunnel in the high water-rich pebble stratum is not influenced by the tunneling construction of the soil pressure balance shield of the lower tunnel.

Drawings

In order to more clearly illustrate the detailed description of the invention or the technical solutions in the prior art, the drawings that are needed in the detailed description of the invention or the prior art will be briefly described below. Throughout the drawings, like elements or portions are generally identified by like reference numerals. In the drawings, elements or portions are not necessarily drawn to scale.

FIG. 1 is a schematic structural view of a steel pipe.

FIG. 2 is a schematic layout of grouting pipes for deep hole grouting treatment in a hole.

Reference numerals: steel pipe 1, grout outlet 1a, lower tunnel 2, upper tunnel 3.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and therefore are only examples, and the protection scope of the present invention is not limited thereby.

It is to be noted that, unless otherwise specified, technical or scientific terms used herein shall have the ordinary meaning as understood by those skilled in the art to which the invention pertains.

The embodiment provides a high water-rich round gravel stratum earth pressure balance shield fast tunneling construction method, which comprises a high water-rich round gravel stratum earth pressure balance shield fast tunneling construction method, and comprises the steps of performing lower tunnel tunneling construction, performing deep hole grouting treatment in the upper half of a lower tunnel, performing upper tunnel tunneling construction, and performing deep hole grouting treatment in the upper half of the upper tunnel and the lower half of the upper tunnel.

And the deep hole grouting treatment in the holes of the lower tunnel and the upper tunnel comprises inserting grouting pipes, injecting grout and plugging grouting holes. The slurry adopts cement-water glass double slurry and adopts static pressure grouting. As shown in fig. 1, the steel pipe 1 with a diameter of 48 is used as a grouting pipe for the deep hole grouting treatment in the hole, the front end of the steel pipe 1 is subjected to smashing, flattening, attaching and sharpening treatment, a plurality of grout outlet holes 1a are formed in the pipe wall of the steel pipe except for the 500mm thick grouting head end, the diameter d of each grout outlet hole 1a is 6mm, and the distance L between every two adjacent grout outlet holes 1a along the axial direction of the steel pipe 1 is 200 mm.

As shown in fig. 2, the grouting pipes of each grouting section of the lower tunnel 2 include four first grouting pipes and three second grouting pipes, and the second grouting pipes are shorter than the first grouting pipes; the included angles between the four first grouting pipes and the horizontal plane are respectively 22.5 degrees, 45 degrees, 135 degrees and 157.5 degrees, and the included angles between the three second grouting pipes and the horizontal plane are respectively 67.5 degrees, 90 degrees and 112.5 degrees. The grouting pipes of each grouting section of the upper tunnel 3 comprise four third grouting pipes and three fourth grouting pipes which are positioned at the lower half part of the upper tunnel, and four fifth grouting pipes and three sixth grouting pipes which are positioned at the upper half part of the upper tunnel; the fourth grouting pipe is equal to the second grouting pipe in length, and the length of the fourth grouting pipe is 1.5 m; the third grouting pipe and the fifth grouting pipe are equal to the first grouting pipe in length, and the length of each grouting pipe is 3.5 m; the length of the sixth grouting pipe is between the length of the fifth grouting pipe and the length of the fourth grouting pipe, and the length of the sixth grouting pipe is 3 m. The included angles between the four third grouting pipes and the fifth grouting pipes and the horizontal plane are respectively 22.5 degrees, 45 degrees, 135 degrees and 157.5 degrees, and the included angles between the three fourth grouting pipes and the sixth grouting pipes and the horizontal plane are respectively 67.5 degrees, 90 degrees and 112.5 degrees.

and step one, in the test tunneling stage, performing a construction parameter test of penetrating the existing tunnel from the front 200 rings to the front 101 ring pipe pieces of the existing tunnel.

And step two, testing parameters verify the tunneling stage, and optimizing and correcting construction parameters from the front 100 ring pipe pieces to the front 1 ring pipe piece penetrating the existing tunnel.

And step three, the construction is carried out according to the optimized and corrected construction parameters of the step two in the tunneling stage of the existing tunnel construction.

And injecting the gram mud effect into the first stage, the second stage and the third stage through radial holes of the shield shell, wherein injection points of the gram mud effect are at 1 o 'clock and 11 o' clock positions. In the construction of the first stage, the second stage and the third stage, synchronous grouting is carried out when the duct piece is separated from the shield tail, and each five-ring duct piece is sealed once by using cement-water glass double-slurry. And in the construction of the first stage, the second stage and the third stage, secondary grouting is carried out after synchronous grouting is finished.

Taking the example that the Kunming city track traffic number 4 line is crossed with the Kunming subway number 2 line under the condition that the YDK9+ 885-YDK 9+915 mileage left-right line is overlapped:

overview of engineering

No. 4 line right side tunnel is located the left side line below, and No. 2 lines are worn successively down to No. 4 line right side line and left side line. No. 4 line left side tunnel top is apart from the biggest 3.877m at the bottom of the No. 2 line right side tunnel, apart from the minimum 3.516m at the bottom of the No. 2 line left side tunnel, and the vertical distance between the line two is 1.8m about No. 4 line. The buried depth of the left line tunnel is 21.5m, and the buried depth of the right line tunnel is 29.5 m. The stratum from the No. 2 line tunnel bottom to the No. 4 line tunnel top is mainly slightly dense gravel and medium dense round gravel, and is locally filled with plastic powdery clay and slightly dense silt, the left line is mainly positioned in the medium dense round gravel stratum, the right line is complex in geology, the stratum penetrating through the stratum is mainly a medium dense and slightly dense gravel layer, and the local part is filled with plastic powdery clay and slightly dense silt. The terrains of the interval sites are gentle, the stratums mainly comprise a fourth system holonove and an upper renewal system lake-flushing stratum, the thickness of the stratums exceeds 50m, the aquifers are distributed in a multi-layer belt shape, mainly comprise sandy soil and a round gravel soil layer and are mainly submerged, the aquifers at the lower part have pressure bearing performance slightly, the underground water is rich and shallow, and the underground water is mainly supplied by water flowing along the river and seeps and drains in the direction of the yunnan pond. Second, design of tunnel structure

The tunnel in the region is constructed by a shield method, and the tunnel is of a structure with two single-line circular sections. The tunnel adopts general ring type segment lining, tunnel internal diameter 5500mm, segment width 1200mm, thickness 350mm, the segment adopts 6 piecemeals, one of them is little to seal the top piece, two piece adjacent blocks and three piece standard blocks, the piece section of jurisdiction central angle of block of capping is 21.5, 3 piece (being A1, A2, A3 respectively) central angles of standard block section of jurisdiction are 67.5, each piece about the adjacent block section of jurisdiction, the central angle is 68, longitudinal joint is 16 departments, arrange according to angle such as 22.5.

No. 2 left and right tunnel under shield tunnel all adopt strenghthened type section of jurisdiction (section of jurisdiction arrangement of reinforcement steel content improves to 215kg/m3) and bolt (8.8 level bolt) to improve section of jurisdiction intensity and deformability. Establish 12 single bolt between the hoop section of jurisdiction, vertically establish 16 bolts, section of jurisdiction center department establishes a hole for hoist, double as secondary grouting hole, and the grouting hole is add to partial stratum section of jurisdiction, and except that the block of capping, every section of jurisdiction is add 2 grouting holes and is carried out the in-hole slip casting and consolidate the construction. The longitudinal seam of the duct piece ring adopts an ethylene propylene diene monomer sealing strip for water stop, and the gap between the duct piece and the surrounding soil body is synchronously filled with composite mortar.

Third, main equipment configuration

Two shield constructions are configured according to the overall construction organization arrangement region, the selected shield construction machine mainly aims at major and difficult projects such as settlement control, gushing and the like, and the cutter arrangement of a cutter head of the shield construction machine, a muck improvement system and other related systems are optimized so as to ensure that the shield construction safety in the process of mechanically crossing a risk source is met in the propelling process.

Comparison table for requirements and adaptability of heavy and difficult engineering points on shield machine

The selected shield machine is a composite earth pressure balance shield machine, and the main parameters of the two shield machines are as follows:

construction parameter table of left and right line shield machine

Fourthly, construction planning

According to the arrangement of the whole construction period of the standard section and the actual preparation condition of passing through the No. 2 line, the following general scheme is adopted for ensuring that the shield can pass through the No. 2 line quickly, smoothly and safely:

1. according to the principle that the shield stack falls down and passes through the No. 2 line in the process of descending, the construction sequence is that the right line tunnel (descending line) is constructed first, and then the left line tunnel (ascending line) is constructed.

2. Strictly according to the design scheme, the tunnel that the shield tunnel passes No. 2 line construction mileage section down all adopts the strenghthened type section of jurisdiction of reserving the injected hole, and after the construction of right side line tunnel was accomplished, in time adopted the injected hole of reserving on the section of jurisdiction to carry out deep hole slip casting to the section of folding intermediate layer soil body and consolidate the processing, left side line shield was worn No. 2 line construction again.

3. A domestic advanced mud-restraining effect construction method is adopted to determine the tunneling construction parameter test sections (1011 st to 1111 th rings (YDK9+649.215 st to YDK9+769.215) of the lower line No. 2 and (ZDK9+633.615 st to ZDK9+753.615) of the left line No. 2, and the tunneling parameters of the lower line No. 2 are analyzed and researched, so that the tunneling parameters of the lower line No. 2 are reasonably worked out.

4. Before the line No. 2 is worn down, complete maintenance is carried out on supporting equipment behind the shield machine, material reserves such as field site duct pieces, waterproof materials and duct piece bolts are made, works such as commercial mortar and slag discharge are coordinated well, one-time comprehensive technical background of the cross and training are carried out on field construction personnel, and the line No. 2 is worn down at the uniform speed and the safety of the shield is ensured.

5. Strictly obeying a deformation early warning management system, and making a downward-penetrating No. 2 wire automatic monitoring and measuring system in advance; during construction, the No. 2 line is subjected to 24-hour full-automatic online monitoring on deformation, stress and the like, once data are abnormal, the system triggers a corresponding alarm mechanism, and the first time is notified in the forms of short messages, faxes, broadcasts and the like. The accumulated construction of the line 4 is not more than 6.5mm, and 4.5m is used as an alarm value for control.

6. In the process of downward penetration, related emergency material preparation needs to be made in advance, and if monitoring conditions (monitoring values or monitoring rates) are abnormal, deep hole tracking grouting in a hole is reasonably performed. If the control value exceeds the early warning value by 4.5mm, the permission of the No. 2 line operation unit is obtained, and related hole internal reinforcement is carried out in the No. 2 line hole so as to ensure the construction safety of the operation line.

7. And the right line 1027 ring (mileage ZDK9+663.652) and the left line 1018 ring (mileage ZDK9+656.452) are used as shield machine stopping and maintenance points, the shield equipment is thoroughly maintained once, active opening is performed to check shield cutters, and if the abrasion exceeds a loss value, the cutters are replaced.

8. After the construction of the shield left line is completed, deep hole detection is carried out in the tunnel from the left line, the detection positions are the top (an interlayer between the top and the existing subway No. 2 line) and the bottom (an interlayer between the right line and the No. 4 line), the soil body around the existing line is guaranteed to be compact and controllable after the shield passes through, if the hole range is detected, the deep hole supplement grouting measure in the hole is immediately organized, the operation safety of the later subway No. 2 line and the No. 4 line is guaranteed, and the disturbance to 2 subway lines when the shield with the No. 5 line passes through is reduced.

Generally, the shield under-passing No. 2 line construction is divided into a test stage tunneling section (100 rings, a mud-restraining auxiliary power method and a construction parameter determining process), a test section parameter verification tunneling section (100 rings, a mud-restraining auxiliary power method and a construction parameter optimizing and correcting process), a forward-passing No. 2 line construction stage and a post-passing observation stage (measures are reasonably taken mainly according to monitoring conditions to avoid the excessive accumulated settlement).

Fifth, experimental excavation stage research scheme

5.1 Shield tunneling parameter research scheme

In the propulsion test section, the relation between soil pressure, propulsion speed, soil output, grouting amount and grouting pressure setting and ground settlement is mainly analyzed, the change law of the shield propulsion soil body settlement in the section is mastered, the soil body property is searched, so that the construction parameters passing through the building are correctly set, corresponding measures are taken to reduce the soil body settlement, and the safety of the ground surface and structures is ensured.

The engineering adopts an earth pressure balance type shield tunneling machine, which utilizes the earth pressure in a pressure bin to balance the earth mass of an excavation surface, thereby achieving the aim of supporting the excavation surface right ahead of a shield, the setting of the balance pressure is the key of the earth pressure balance type shield construction, the maintenance and adjustment of the set pressure value is an important link in the process of pushing the shield, the setting of the balance pressure value contains the mutual relation of thrust, propulsion speed and earth output, and plays a leading role in controlling the shield construction axis and the stratum deformation, so that the shield tunneling construction needs to be matched with the analysis of monitoring information according to different earth qualities, earth thickness and ground buildings according to different earth qualities, the setting of the balance pressure value is timely adjusted, the shield attitude in the propulsion is required to be kept relatively stable, the deviation correction amount is not too large each time, the disturbance to the earth mass is reduced, good conditions are created for assembling segments, and good conditions are created according to the thrust force simultaneously, Monitoring data of the propelling speed, the soil output and the formation deformation, and adjusting the grouting amount in time, so that the axial line and the formation deformation are controlled within an allowable range.

Under the condition of ensuring the flow plasticity and impermeability of the muck, the research on the shield tunneling parameters mainly controls the pressure and thrust of the shield soil bin, and minimizes the disturbance to the stratum while maintaining the stability of the excavation surface.

5.1.1, calculating the control ranges of theoretical soil bin pressure and thrust in the test section

1) Theory of correlation

(1) Shield tunnel overburden pressure calculation

Selecting a calculation theory: according to the Japanese standard, loose soil pressure is mostly adopted in sandy soil when the thickness of covering soil is more than 1-2 times of the outer diameter of a tunnel; in cohesive soil, loose soil pressure is mostly adopted if hard clay is used and the thickness of the covering soil is greater than 1-2 times of the outer diameter of the tunnel, and the weight of the full covering soil is usually considered as the soil pressure if soft clay is used. The calculation principle of the overburden pressure of the stratum tunnel is provided by referring to the actual measurement result of the related literature and combining the Japanese standard suggestion, and the table is specifically shown.

Calculation principle of overlying soil pressure of tunnel

Remarking: h is the tunnel earthing thickness (m), H is the arch forming height (m) of the sand foundation, D is the tunnel outer diameter (m), and N is the standard penetration number (impact/30 cm).

(2) Soil bin pressure calculation

The shield soil bin pressure during actual construction is between the lateral active water and soil pressure and the static water and soil pressure and is as close to the lateral static water and soil pressure as possible. The active soil pressure is generally calculated by adopting a Rankine soil pressure theory in shield construction, and water and soil calculation is selected for gravel and round gravel strata with good water permeability.

The lateral active soil pressure coefficient calculation formula is as follows:

the lateral static soil pressure coefficient calculation formula is as follows:

(3) shield total thrust calculation

The resistance suffered by the shield tunneling mainly comprises the following six items: the friction between the shield shell and the surrounding stratum, the front propulsion resistance when the shield machine propels, the friction between the duct piece and the shield tail, the penetration resistance of the shield machine cutting ring, the steering resistance and the traction resistance of the rear matching device.

In the formula: f is total thrust; f₁The frictional resistance between the shield shell and the surrounding stratum; f₂The front propulsion resistance is the front propulsion resistance of the shield machine during propulsion.

In the actual engineering, the influence of the latter four items is smaller, so that the influence of the front propulsion resistance and the peripheral friction resistance of the shield shell during the propulsion of the shield tunneling machine is only considered when the total thrust is calculated, and F is calculated₁、F₂After the sum, the sum is divided by 90% to obtain a theoretical calculation value of the thrust. Generally, the following are provided:

in the formula: d is the diameter of the shield; l is the shield shell length; p is a radical of_eIs the pressure of overlying soil (kN/m)²)；μ_msIt is generally preferable that the coefficient of friction between the earth formation and the earth crust

ρ_gThe weight of the shield tunneling machine is severe; q. q.s_e1The upper horizontal soil pressure; q. q.s_w1Upper water pressure; q. q.s_e2The lower horizontal soil pressure; q. q.s_w2The lower water pressure.

(4) Shield torque calculation

The torque suffered by the shield tunneling mainly comprises the following seven items: the friction force between the front of the cutter head and the soil body, the friction force between the periphery of the cutter head and the soil body, the stratum resistance torque when the cutter head cuts the stratum, the friction force torque on the back of the cutter head, the resistance torque of a stirring rod of the cutter head, the sealing friction torque of the cutter head and the bearing friction torque.

In the formula: t is total torque; t is₁The frictional resistance between the front face of the cutter head and the soil body is shown; t is₂The frictional resistance between the periphery of the cutter head and the soil body is shown; t is₃And the resistance torque of the stratum when the cutter head cuts the stratum.

In practical engineering, the influence of the latter five items is small, and T is generally calculated₁、T₂、T₃The sum is taken as the theoretical calculation of the total torque. Generally, the following are provided:

T₁＝πD³(μP₁+c)(1-η)/12

T₂＝πD²b(μP₂+c)/2

T₃＝D²q_uV/(8N)

in the formula: mu is the friction coefficient between the soil body and the cutter head; eta is the cutter head opening rate; b is the extension length of the cutter head; q. q.s_uThe uniaxial compressive strength of the formation; p₁The average soil pressure acting on the front surface of the cutter head; p₂Is the average soil pressure acting on the side surface of the cutter head.

(5) Test section tunneling parameter control range calculation

The test section belongs to a single slope section, only two section tunneling parameters of large mileage and small mileage are calculated in the single slope section, and finally obtained tunneling parameters are as follows:

and performing a comparison test on the shield tunneling parameter speed of the test section, performing comparison tests of 30mm/min, 35mm/min and 45mm/min on a primary plan, and selecting the optimal matching parameters.

5.1.2 optimized value of test section soil bin pressure

(1) Collecting shield tunneling parameters and earth surface settlement data of a previous tunneling section of the interval, and determining a proper stratum constitutive model and relevant parameters through inverse analysis.

(2) Establishing a three-dimensional finite element numerical analysis model of a test section, respectively calculating the ground surface deformation conditions caused by double-line construction under the action of 0.9 time, 1.0 time and 1.1 time of theoretical static soil pressure, establishing a typical section soil pressure and deformation model through numerical fitting, and optimally taking values of the soil bin pressure through ground surface deformation data.

5.1.3 method for adjusting abnormal tunneling parameters and abnormal surface deformation

In the tunneling process of the test section, if the conditions that the torque of a cutter head is too large, the tunneling speed is too slow and the ground surface is greatly raised or settled are met, the following methods are adopted to solve the problems:

(1) excessive cutter torque

The shield test section is planned to adopt the full soil pressure mode for tunneling, and the rotating speed of the cutter head is set to be a constant value. If the cutter torque is larger than the torque before the test section, then:

firstly, checking the state of the muck, if the flow plasticity of the muck is poor, indicating that the improvement effect of the muck is poor, and immediately adjusting improvement parameters according to the indoor test result and then continuously observing;

secondly, if the muck state is normal, the injection amount of the muck modifier in front of the cutter head is possibly low, the effect of reducing the friction force of the soil and the cutter head is weak each time, the foam injection amount of each pipeline in front of the cutter head is increased, and the foam flow setting value of each pipeline is increased by 100L/min each time;

thirdly, if the state of the muck is normal, the effective stress of the soil is possibly larger due to overlarge pressure of the soil bin, the energy required by the cutter head for cutting the soil body is increased, the soil discharging amount can be increased by increasing the rotating speed of the screw machine, the pressure of the soil bin is reduced, and the reduction ratio of the pressure of the soil bin is adjusted according to the reduction ratio of 0.1 actual supporting force to theoretical supporting force (P/P0) each time.

If the tunneling speed is high, the torque is increased probably due to the fact that the penetration degree of the cutter head is high, and if the situation occurs in the test, the problem is solved by adopting a mode of reducing the thrust, and the thrust is reduced by 1000kN each time.

(2) The tunneling speed is too slow

The shield tunneling parameter control mainly controls the shield soil cabin pressure and the thrust, the soil cabin pressure can be basically maintained stably through the regulation of soil inlet and outlet, and when the conditions of overlarge thrust and low thrust speed occur in tunneling, the method comprises the following steps:

secondly, if the state of the soil residue is normal, the pressure of the soil bin is possibly caused by overlarge pressure, the pressure of the soil bin can be reduced by increasing the rotation speed of the screw machine and increasing the soil discharge amount under the condition of properly maintaining the thrust, and the pressure reduction ratio of the soil bin is adjusted according to the ratio (P/P0) of the actual supporting force to the theoretical supporting force reduced by 0.1 each time.

(3) Large settlement or uplift when cutter head passes through monitoring section

And (3) finding that the settlement above the cutter head is abnormal according to the test section surface settlement monitoring data:

if the large subsidence occurs, adjusting by increasing the ratio of actual supporting force to theoretical supporting force (P/P0), wherein the adjustment ratio is 0.1 each time, the adjustment method is to increase the thrust and/or reduce the soil output, if the soil output is difficult to control because the state of the soil is over-dilute, the injection amount of the modifier is properly reduced according to the indoor test so as to control the slump of the soil in a reasonable range;

secondly, if the large bulge occurs, the adjustment should be carried out by reducing the ratio of the actual supporting force to the theoretical supporting force (P/P0), wherein the adjustment ratio is 0.1 each time, and the adjustment method is to reduce the thrust and/or increase the soil output.

5.2 Backward grouting research scheme

And a metro No. 2 line is penetrated in the interval, the control of stratum sedimentation is very strict, and the stratum is a water-rich round gravel stratum which is easy to be disturbed to form stratum deformation. In order to obtain the synchronous grouting of the duct piece of the lower penetrating section and the secondary supplementary grouting parameters of the duct piece of the lower penetrating section, the technical scheme of the grouting of the test section is researched, the grouting comprises the synchronous grouting of a shield and the secondary grouting of the duct piece, and the research contents comprise grouting slurry materials, proportion, grouting equipment and the like.

Overview of Shield Backward grouting

(1) Slurry performance requirement of wall postgrouting

For the purpose of the back-grouting, the grouting must fill the tail gap quickly and reliably, for which reason the back-grouting properties must meet the following requirements:

the shield tail gap filling method has the advantages that filling performance is good, and the shield tail gap filling method does not flow to other fields except the shield tail gap and does not leak into a digging surface and a surrounding rock soil body.

② the slurry has good fluidity and less segregation.

Thirdly, the slurry should have the characteristic of not being diluted by underground water.

And fourthly, the material separation is less, so that the material can be pressed and conveyed for a long distance.

After the backfill grouting filling, the early strength is expected to be uniform, and the value is equivalent to the strength of the undisturbed soil.

Sixthly, the volume shrinkage and the permeability coefficient of the slurry after hardening are small.

No environmental pollution and low cost.

The most important of the above requirements is the characteristics of filling property, fluidity and no loss to the region outside the shield tail, and the satisfaction of the characteristics is the key to realize the aim of the grouting after the wall is built.

(2) Materials and kinds of grouting after the wall

Considering that the diffusivity and the grouting pressure of the grout are larger, the backfill grouting material adopted in the interval is comprehensively considered to be single-liquid hard grout, the grout has the properties of short setting time, quick setting and high strength, particularly high early strength, and the double-liquid grout is adopted for filling under special conditions such as the condition of monitoring abnormal settlement. The cement, bentonite, fly ash, sand and water are included, and the distribution ratio and technical indexes of each part are shown as the following table:

existing grout proportion and technical parameters (material dosage per cubic meter kg)

Cement	Bentonite clay	Fly ash	Sand	Water (W)	Density of
						200	80	300	800	420	1880kg/m3

The design requirement is as follows: the slurry is recommended to be a hardenable slurry which is short in setting time, quick in setting and high in strength, particularly early strength, the initial setting time is 3-4 hours (the transportation distance is 1.5 hours, the initial setting is designed to be 1-2 hours), and the final effective strength of the grouting body reaches 2 MPa.

The field application effect shows that the grouting effect is ideal, and the problems of stratum settlement and pipe piece floating can be effectively controlled.

Most of the area crossed by the Kunming subway No. 4 line is a water-rich round gravel stratum, so that the underground water level is high and the stratum permeability is strong. The grouting slurry is required to have good workability, filling performance, early strength and the like, and also to have higher requirements on the water retention of the slurry. Therefore, single-liquid quick-hardening slurry with optimized mixing ratio is adopted in the region, and double-liquid slurry filling is adopted in special conditions such as monitoring abnormal sedimentation.

(3) Index of slurry performance

The requirements on the performance indexes of the quick-hardening slurry are as follows:

gel time: the initial setting time 1h is 2h, and the gelation time is adjusted by adding a coagulant and changing the mixture ratio through a field test according to the formation condition and the tunneling speed. For the highly permeable stratum and the section needing grouting to provide higher early strength, the proportion can be further adjusted and the early strength agent can be added through field tests, so that the gelling time is further shortened;

B. strength of the consolidated body: 1d is not less than 0.2MPa, and 28 days is not less than 2.0 MPa;

C. the calculus rate of serous fluid: more than 95 percent, namely the consolidation shrinkage is less than 5 percent;

D. slurry stability: the decantation rate (the ratio of the volume of floating water to the total volume after standing and precipitating) is less than 5 percent;

E. slurry fluidity: greater than 180 mm;

F. slurry consistency: between 9 and 12 cm.

5.2.2, grouting amount and grouting pressure

(1) Shield synchronous grouting amount and grouting pressure

Grouting pressure

The grouting pressure is slightly greater than the static water-soil pressure of the stratum position, and meanwhile, slurry is prevented from entering a soil bin of the shield tunneling machine. The initial grouting pressure is determined according to the theoretical static water-soil pressure, and is continuously optimized in the actual tunneling process. If the grouting pressure is too high, the ground is raised, the pipe piece is deformed, and the slurry is easy to leak. If the grouting pressure is too low, the slurry filling rate cannot catch up with the void formation rate, which in turn causes ground subsidence. Generally speaking, the grouting pressure is 1.1-1.2 times of static water-soil pressure, and the maximum pressure is not more than 5 bar.

Because multiple points are grouted simultaneously on the circumference of the shield tail, the grouting pressure of each point is different and keeps proper pressure difference to achieve the best effect in consideration of the difference of water and soil pressure and the requirement of preventing the duct piece from sinking and floating greatly.

② grouting amount

According to the excavation diameter of the cutter head and the outer diameter of the segment, the grouting amount of the segment in a ring can be calculated according to the following formula.

Q-one-ring grouting amount (m 3);

l-ring width (m);

d-excavation diameter (m);

d is the outside diameter (m) of the pipe piece;

k-expansion coefficient is 1.5-2.

The required slurry amount Q for each loop can be calculated according to the above empirical formula.

Grouting time and tunneling speed

The grouting time is controlled according to the grout with different setting time and the tunneling speed in different stratums. The method realizes the synchronous tunneling and grouting without grouting and tunneling, and determines the grouting time by controlling the double standards of synchronous grouting pressure and grouting quantity.

And stopping grouting after the grouting amount and the grouting pressure reach set values, otherwise, still needing to be supplemented.

The synchronous grouting speed is matched with the tunneling speed, and the average grouting speed is determined according to the ring grouting amount completed within the time of completing one-ring tunneling by the shield.

Checking grouting end standard and grouting effect

The method adopts a double-index control standard of grouting pressure and grouting quantity, namely when the grouting pressure reaches a set value and the grouting quantity reaches more than 85% of a designed value, the quality requirement can be considered to be met.

The grouting effect inspection mainly adopts an analytical method, namely, comprehensive evaluation is carried out by combining the measurement results of the quantities of the duct pieces, the earth surface and surrounding buildings according to a pressure-grouting quantity-time curve. If necessary, the arch part can be inspected by adopting an ultrasonic detection method through spectral analysis, and the parts which do not meet the requirements are subjected to supplementary grouting.

Grouting equipment

The synchronous grouting equipment comprises a grouting pump, a grouting distribution system, a grouting pipe orifice positioned at the tail part of the shield, a hose and the like. The grouting distribution system ensures that the flow distribution of each grouting outlet is uniform, the opening and closing of the grouting outlets can be flexibly adjusted according to construction detection information, and each grouting pipeline is easy to check and clear.

(2) Shield secondary grouting amount and grouting pressure

The secondary grouting is that firstly, a segment hoisting hole is dug manually, and then a grouting pipe is inserted for grouting. The back lining is filled by injecting cement grout (same as synchronous grouting) first, and then the grouting hole (the position of the opening) is sealed by injecting glass double-liquid grout.

Grouting pressure

The grouting pressure of the secondary grouting cement paste is determined according to the depth of the stratum, and is less than 0.5MPa in principle, and the flow rate of the cement paste is as follows: 10-15L/Min, so that the slurry can uniformly seep along the outer wall of the pipe piece, the soil body cannot be split, a bulk reinforcing area is formed, and the grouting effect is influenced.

② grouting amount

And (4) injecting secondary grouting according to the monitoring condition, and dragging out the shield to perform injection once every 3 rings. A range of hoops are formed to limit deformation and settlement of the tunnel. The grouting hole position is a central hole of the supporting block and the connecting block, and grouting is performed on the next ring if the long section meets the sealing of the grouting hole of the adjacent connecting block. The grouting amount of each 3 rings is about 2m3 generally, and is adjusted according to the actual tunnel settlement monitoring condition to ensure that the tunnel line shape is within the specification requirement range.

Grouting equipment

And (3) using a special slurry pump for secondary grouting, chiseling a protective layer on the outer side of the segment hoisting hole before grouting, and installing a special grouting joint. The required equipment is as shown in the table:

device quantity statistics

Device	Number of
		Hydraulic grouting machine	1 table
Mortar deliveryPump and method of operating the same	1 table
		Pulp storage barrel	2 are provided with
Grouting pipe	A plurality of

5.2.3 slip casting field real-time dynamic adjustment scheme

1) And (3) making a detailed grouting construction process flow and a grouting quality control program, strictly implementing grouting, inspection, recording and analysis according to requirements, making a P (grouting pressure) -Q (grouting amount) -t (time) curve in time, analyzing the relation between the grouting speed and the tunneling speed, evaluating the grouting effect, and feeding back to guide the next grouting.

2) And according to the monitoring results of the lining deformation of the duct pieces in the tunnel and the deformation of the ground and surrounding buildings, information feedback is carried out in time, grouting parameters and a construction process are corrected, and the found condition is solved in time.

3) The maintenance and the maintenance of grouting equipment are well done, grouting materials are supplied, grouting pipelines and equipment are cleaned at regular time, and grouting operation is guaranteed to be carried out smoothly, continuously and uninterruptedly.

4) Before each ring of tunneling, the working state of the grouting system is confirmed to be normal, the slurry reserve is enough, and once the grouting system breaks down in the tunneling process, the tunneling process is immediately stopped for inspection and repair.

5) When slurry leakage occurs at the shield tail, the grouting pressure is instantly reduced, and meanwhile, the injection of the shield tail sealing grease is enhanced. If the problem is not solved, stopping grouting and sealing by increasing the injection amount and injection pressure of the shield tail sealing grease. And after treatment, synchronous grouting and tunneling are carried out.

5.3 deformation monitoring and predictive control research scheme

(1) And (3) tracking and collecting the third-party monitoring data of stratum deformation caused by shield tunneling in the test section, and performing supplementary testing, wherein the monitoring data comprises surface subsidence, stratum displacement, underground water level change, shield tunneling data and patrol records during tunneling.

Instrument monitoring project

The field instrument monitoring content is shown in the following table:

monitoring content

② inspection of the content

The contents of the field patrol are shown in the following table:

inspection tour content

(3) Stratum parameter inversion pre-analysis based on test section actual measurement data

Collecting shield tunneling parameters and monitoring data in the early stage of Kunming subway, determining a rock-soil constitutive model and stratum physical and mechanical parameters suitable for pre-analysis of stratum, establishing a Plaxis or ABAQUS software to establish a shield test section numerical analysis model, and pre-analyzing a stratum deformation distribution rule caused by shield tunneling.

Carrying out investigation and analysis of a geological survey report and documents, determining a stratum parameter inversion analysis method based on monitoring data and a numerical model, and investigating reasonable value range and a simulation method of parameters such as stratum loss rate, stratum consolidation effect and the like of Kunming high water-rich pebble stratum shield tunneling stratum deformation.

Sixthly, controlling tunneling parameters of the existing tunnel construction

6.1 shield under-penetration No. 2 line tunneling parameter setting

The specific parameter setting value of the shield under-penetration No. 2 line is set according to the shield burial depth, the shield tail gap, the soil layer condition of the position where the shield is located and the left and right line test sections, the construction tunneling parameters need to be dynamically adjusted, optimized and adjusted according to the monitoring and measuring conditions, and the tunneling parameter setting of the shield under-penetration No. 2 line is preliminarily formulated as follows:

6.2 slag discharge control

The management of the soil output is the basic of shield tunneling, and the most direct and effective means for controlling the stratum loss rate is guaranteed. The control of the soil output is mainly based on the control of the volume of the residue soil and assisted by the weight rechecking. In shield construction, a muck sample discharged in tunneling is analyzed, the geological condition is judged, and the soil output is determined according to the geological condition.

According to the result analysis of the test section, timely checking whether the corresponding ground is abnormal every day in the shield advancing process; when the soil output exceeds the standard, the inspection frequency needs to be increased and a specially-assigned person needs to monitor. The important aspect of soil quantity management is strictly ensuring the soil filling state and the muck workability in the soil bin.

The soil output is also an important factor affecting the ground settlement, as is the soil pressure value.

Theoretical soil output (full square):

V＝(π/4)*D²*L

＝(π/4)x6.44²*2

equal to right line 39.07m³Ring/left line 39.55m³Ring (C)

The loose coefficient of the soil body is 1.05-1.1, and the actual soil output is controlled at (the right line is 41 m)³～43m³Left line 41.5m³～43.5m³) To maintain a certain soil pressure and thus to control the amount of settlement within a minimum range.

The construction process strictly grabs muck management, timely analyzes muck data, strictly controls the stratum loss rate, and adopts two indexes of 'quality' and 'volume' to control the unearthing rate, so that the stratum loss rate is within 0.5 percent. In order to obtain scientific and reasonable shield tunneling parameters, the most reliable data information is obtained by means of data analysis and mathematical statistics in a lower-crossing No. 2 line anterior shield test section.

6.3 Shield Curve construction

As the No. 2 segment passing below the shield tunnel is constructed by curve segments with the radius of 600m, the change of the shield posture greatly affects the surrounding during the propelling, in order to reduce the adverse effects caused by the over-excavation and the excessive deviation correction of the shield in the construction of the curve segments, the shield tunneling speed is properly reduced, the deviation correction is timely carried out, the frequent and less correction is realized, and the synchronous grouting quantity of the shield tail and the secondary grouting quantity in the tunnel are timely increased.

When the deviation of the axis is required to be corrected, the measure of adjusting the combination of the shield jacks is adopted to correct the deviation: and at the opposite deviation direction, the working pressure of the jacks in the area is reduced, so that the stroke difference of the jacks in the two areas is caused, and the effect of correcting deviation is achieved. For correcting the snake-shaped movement of the shield machine, long-distance slow correction is taken as a principle, and the primary correction amount is not more than 5 mm.

When the shield is in deviation correction, the longitudinal slope is controlled within +/-1 percent, and the plane deviation is controlled within 15 mm. When the shield is found to deviate from the axis, sudden correction is avoided, smoothness is kept, and the measurement work of correction is enhanced. If the front stratum changes, the propulsion deviation correcting speed is preferably slowed down, but the front soil pressure is properly adjusted to ensure the mobility and water stopping performance of the soil body, so that the excavation surface is kept stable and balanced.

6.4 Propulsion speed

The constant and stable advancing speed is ensured during downward penetration, the advancing direction of the shield is strictly controlled, the advancing construction is carried out at the speed of 40mm/min (selected by combining with the speed parameter of a test section), the deviation correction is reduced, and particularly, the deviation correction is carried out according to a large amount of values. In the process of advancing the downward-penetrating building, the advancing direction of the shield machine is measured every 60cm, deviation rectification is reduced as much as possible, and the uniform-speed advancing is kept during downward penetration of the shield machine, so that the shield machine is guaranteed to stably and underground penetrate the building.

6.5 cutter head speed

The shield adopted at this time is an earth pressure balance shield machine, and the cutter head is stepless and adjustable. In order to give full play to the performance of the cutter head and reduce the disturbance of the rotation of the cutter head to the soil body, the cutter head rotates at a low speed in the crossing process in the construction process of crossing the No. 2 line. And observing data such as the button moment of the cutter head, the shield rotation angle and the like.

6.6 segment Assembly and Shield Tail gap control

1. Segment splicing quality control

(1) The quality requirement of segment assembly is as follows: the allowable height difference of adjacent pipe pieces is less than or equal to 5mm, the circular seam is opened by less than 1mm, the longitudinal seam is opened by less than 2mm, the clearance of the ring surface of adjacent rings is less than or equal to 6mm, the clearance between adjacent blocks of the longitudinal seam is less than or equal to 1mm, and the diameter allowable deviation after lining ring formation (when just coming out of the shield tail) is as follows: 2 thousandth D (D is the vertical outer diameter of the tunnel). The ovality of the lining ring is less than or equal to 20mm, and the rotation angle of the horizontal shaft of the tunnel is less than or equal to 0.6 degrees.

(2) The allowable deviation (up, down, left and right) of the actual axis and the designed axis of the tunnel is respectively 50mm, the fold angle of the axis is not more than 0.4 percent, when the shield axis exceeds the allowable deviation of the design, the shield axis is summarized in time, shutdown and rectification are carried out seriously, the next improvement measure is provided, and the overproof phenomenon is avoided again.

(3) The allowable deviation of the pipe sheet assembly in the construction and the inspection method meet the regulations of the following table.

Segment assembly allowable deviation table

Note: d refers to the outer diameter of the tunnel, and the unit is mm.

When the shield is shut down to assemble the segments, the shield machine can retreat due to the shrinkage of the jack, so that the pressure balance of the soil bin is damaged, and the local stratum instability is caused. The jack that once withdraws in the section of jurisdiction assembly process should be as few as possible, satisfy the section of jurisdiction assemble can. In the segment assembling process, field technicians need to strengthen the monitoring of the pressure of the soil bin, and the soil pressure is built in time after the assembling is completed.

6.7 improvement of dregs

According to the geological condition of the lower-crossing No. 2 line, the shield mainly passes through a high-water-rich round gravel stratum, the shield tunneling greatly disturbs the stratum, the phenomenon of gushing and the like easily occurs on a screw conveyor, the stability of the tunnel excavation surface is endangered, and particularly, the lower-crossing train north station tunnel and the subway No. 2 line have higher shield tunneling risk. Therefore, in order to ensure that the double-line tunnel shield which is overlapped up and down on the high water-rich round gravel stratum is tunneled smoothly, the technical requirements on shield muck improvement and tunneling parameter control are high.

The final purpose of improving the slag soil is that the soil body has better flow plasticity, proper consistency, lower water permeability and smaller frictional resistance, and the slag is convenient to discharge by a screw conveyor. The residue soil improvement mainly adopts the combination of three modifying agents of foam, bentonite and polymer, the bentonite slurry adopts sodium bentonite (CMC is added according to the slurry quality), the polymer solution adopts PAM solution, the foam is mainly used for preventing a cutter disc from caking mud cakes and protecting cutters in a cohesive soil layer, and the bentonite and the polymer are mainly used for a spiral conveyor and a soil bin to ensure the workability of the soil body.

The muck test materials are all carried out by adopting a shield to pass through a No. 2 line stratum field sampling soil layer.

The method for improving the muck comprises the following steps:

1. foam modifier selection test

The content of the mineral components in the viscosity of the gravel stratum is low, the risk of mud cake formation is low, the foaming agent is a non-dispersive shield foaming agent, the test mainly tests whether the foam generated by the foaming agent can meet the requirements of shield tunneling, and the performance of the foam is mainly measured by two indexes of half-life period and foaming multiplying power. According to construction experience, the half-life period of the foam is more than 5 minutes, and the foaming ratio is within the range of 10-20, so that the high-quality foam meeting the construction requirements of the earth pressure balance shield can be obtained; the foaming equipment used in the foaming test is assembled to simulate a shield foaming system.

The concentration of the foaming agent in the test is the recommended value (3%) provided by a manufacturer, and the foaming pressure is 3bar (the value of the common foaming pressure in shield construction). The test results are shown in the table, and the table shows that the foaming agent provided by construction units has good performance and meets the shield tunneling requirement.

Results of testing foam agent Properties

Blowing agent manufacturer	Type of blowing agent	Concentration of	Pressure of foaming	Foaming ratio	Half life
						Kandatt	Non-dispersed type	33％	3bar	20	6 minutes and 55 seconds

2. Slurry formulation selection

6 expansion tanks (32 m3 are arranged on site (because the right and left lines are successively tunneled, 3 expansion tanks are used by a single shield machine), and the expanded bentonite is pumped into a bentonite box in the shield machine by a middle plate and then pumped to the front of a cutter head by a slurry pump in the shield machine. According to the requirement that the maximum expansion time is not more than 24 hours and the previous construction experience and literature investigation, the control index of the slurry is determined to be that the funnel viscosity is more than 40s, the density of the slurry needs to reach 1.06-1.23 g/cm3, and the colloid rate reaches more than 96%.

The test bentonite slurry adopts sodium bentonite purchased from Wenshan, and is subjected to martensite viscosity, colloid rate and sand content test mainly after the slurry is stirred, and the test results are shown in the following table:

results of slurry consistency test

3. Polymer solution formulation

The polymer solution is prepared by PAM, the concentration of the solution is 5 per mill, the density of the solution is 1.01g/cm3, and the Markov viscosity of the polymer is 48 s.

4. Muck flow plasticity test

After the parameters of the modifier are determined, the improvement test of the muck can be carried out, and the purpose that the muck has better impermeability, better fluidity and certain plasticity (flow plasticity) is ensured is achieved; however, the improved muck has long penetration test time, large preparation workload and large requirement on the tested muck, and an original soil sample taken on site is limited, so that the muck is subjected to a fluidity test firstly, and then the muck meeting the fluidity test is subjected to the penetration test; because the slump test is the most common method for rapidly measuring and evaluating the flow plasticity of the muck at present, the slump test is firstly adopted to evaluate the flow plasticity state of the muck in the research. In the test, after the slurry is added, PAM and foam are added to adjust the flow plasticity of the residue soil.

5. Testing of the impermeability of the residue

After the slump test determines the improvement parameters for enabling the muck to have good flow plasticity, a seepage test can be developed to further screen reasonable improvement parameters; according to literature research and construction experience summary, the permeability coefficient of the slag soil needs to be controlled to be below 1 x 10 < -5 > m/s when shield construction is normally carried out, a large-scale permeameter customized by a research group is adopted in an impermeability test, the diameter of the permeameter is 30cm, the height of the permeameter is 70cm (the sample preparation height is 60cm), pressure measuring holes are arranged above and below a sample to calculate real-time pressure difference, the permeameter can measure the sample with d85 being less than or equal to 6cm, the maximum water head height can be adjusted to 5bar, the section round gravel stratum d85 is between 2cm and 5cm, and the water pressure is between 1bar and 2.5bar, so the permeameter can be used for research of the stratum permeability test.

For the penetration test result, according to engineering experience, the residue soil should maintain the penetration coefficient at 10-5m/s, and the test conditions all meet the requirements.

Operating conditions and results of seepage test

6. Muck improvement scheme and parameters

Based on the above test results, the improved parameter scheme in the table is drawn up.

On-site muck improvement scheme

The tunneling set value of each improvement parameter:

the diameter of the right line shield is 6.44m, the shield tunneling speed is set as a display value v (unit is mm/min) of a control panel, zeta is a loose coefficient of soil, a value is 1.2, and the soil tunneling amount during shield tunneling per minute is as follows:

v earth-a shield-v.1.2-39.08V (l)

(1) Set values for polymer PAM solution and bentonite slurry:

the bentonite slurry is injected into 3 pipelines in total, 2 pipelines on the cutter head and foam are injected in a common pipe, one pipeline in the soil cabin is injected independently, and the bentonite slurry mainly aims at ensuring the impermeability and the fluidity of the residue soil in the soil cabin, so the setting proportion is drawn up according to that the injection amount of the bentonite in the cutter head is 30 percent of the total injection amount, and the injection amount of the bentonite in the soil cabin is 70 percent of the total injection amount.

Improved parameter setting values of shield slurry and PAM solution

(2) Foam set value:

the foam is totally divided into 6 pipelines, and according to foam performance test, total foaming pressure should be set to 3.5-4 bar, and the pressure gauge table display value of each pipeline foaming gun is greater than 3bar when guaranteeing to foam. According to the distribution of each pipeline, the central pipeline (No. 1-2 pipelines) accounts for 50 percent, and the rest pipelines (No. 3-6 pipelines) account for 50 percent of the distribution. The specific set value calculation method is shown in the table.

Shield foam improvement parameter setting value

(3) Recommended value of using amount of muck modifier in each ring of shield tunneling

And according to the improved parameter setting value, calculating the use amount of each ring pipe piece in shield tunneling according to a table.

Recommended value of using amount of muck modifier for each ring pipe of shield tunneling

7. Related art

According to the test result and engineering experience, the improvement of the slag soil in the interval is proposed as follows:

1) because the consistency of the slurry is larger, the range of a stirrer in the slurry bulking tank is required to cover the whole bulking tank, otherwise, the slurry in a region with weaker stirring influence is easy to agglomerate, uniform mixing cannot be realized, and the risk of pipe blockage is caused;

2) for slurry added with 1% of CMC in the ratio of 1:4, the CMC is uniformly mixed with bentonite before stirring and then poured into a swelling tank, otherwise the CMC is easy to agglomerate and lose efficacy, the slurry added with the CMC is used in a short period after swelling for 24 hours, and the slurry consistency is reduced due to chemical reaction after long-term storage;

6.8 synchronous grouting and secondary grouting

Shield constructs the blade disc excavation diameter right side line 6440mm left side line 6480mm of machine, and the section of jurisdiction external diameter is 6200mm, and shield constructs the machine and impels forward after the section of jurisdiction is located the installation at the shield tail, forms the building clearance of right side line 14cm (left side line 18cm) between section of jurisdiction and the soil layer, adopts thick liquid material to fill this annular clearance fast, its aim at: the subsidence of the stratum is prevented and reduced, and the environmental safety is ensured; the formation pressure is ensured to act on the duct pieces radially and uniformly, the displacement and deformation of the duct pieces are limited, and the stability of the structure is improved; the waterproof layer is used as a first waterproof layer of the tunnel to strengthen the waterproof property of the tunnel.

1. Grouting mode

And when the propeller is propelled, the slurry is injected in time by adopting a shield tail synchronous grouting mode. When the shield machine is propelled, filling slurry is injected into an annular building space between the duct piece and the ground layer through a built-in grouting pipe arranged in the shield tail. Each pipe is provided with a high pressure gauge and a valve, the pipes are respectively connected with a mortar pump arranged on a 1# trailer of the shield tunneling machine through hoses, and the mortar pump can be controlled manually or automatically.

And after synchronous grouting is finished, secondary reinforcing grouting is carried out by utilizing the segment hoisting holes and the reserved grouting holes according to monitoring data or special sections.

2. Grouting equipment

The grout is mixed by a grout mixing station of a high concrete building company, is pumped into a grout transport vehicle by a shield well ground pump and then is conveyed into a grout storage tank on a trailer for use, and synchronous grouting is carried out by adopting shield machine synchronous grouting equipment. The secondary grouting adopts a set of independent grouting equipment and is installed on a shield machine trolley at present.

3. Setting of pulp parameters

(1) Grouting pressure: p ═ γ h/980+ (0.12 to 0.13)

In the formula: p slurry outlet pressure (MPa), h tunnel upper casing thickness (m), average unit weight of gamma-casing (KN/m3)

The grouting pressure can be 0.1-0.2 MPa higher than the static water-soil pressure, and slurry is prevented from entering a soil bin of the shield machine and being continuously adjusted in actual tunneling. Because the slurry is simultaneously injected from several points on the circumference of the shield tail, the pressure of each hole at the upper part is slightly less than that of each hole at the lower part by 0.05-0.10 MPa. According to the geological condition and the condition of the thickness of the earth covering of the tunnel, the synchronous grouting pressure can not be larger than the bearing pressure of the pipe piece and the shield tail seal by 0.5MPa generally.

(2) Amount of grouting

In the propelling process of the shield machine, besides soil on the section of the tunnel body, soil loss in other aspects such as over excavation, deviation correction, snake movement and the like also exists. These soil losses are compensated for by simultaneous grouting. The synchronous grouting amount per ring is calculated as follows:

Q＝K×π×(D²-d²)×L/4；

the theoretical grouting amount is calculated as 3.34m on the left line³2.85m on the right³And taking the grouting rate to be 150-200%. The right line of the grouting is 4.3-5.7 m³The left line is 5.0-6.6 m³。

In the tunneling process, the grouting amount is adjusted and dynamically managed according to different geological conditions and surface subsidence monitoring conditions. The principle of controlling the surface subsidence is generally satisfied. When the shield passes through the building, the grouting amount of each ring is more than 180% of the building gap, and the grouting pressure is gradually increased to meet the requirement that the grouting amount is an upper limit value.

(3) Grouting speed: the grouting speed and the advancing speed are kept synchronous, namely grouting is carried out while the shield tunneling machine advances.

4. Grouting material and mixing ratio selection

Before formal construction, different trial preparation and performance measurement comparison are carried out on the slurry mixing ratio, a formula meeting the use requirement is optimized, and the slurry is put into use formally after an experiment. Meanwhile, the ground surface settlement monitoring condition after the propulsion is checked according to the mix proportion of the slurry in the trial propulsion construction process, and is correspondingly optimized and adjusted. The following is the initial mix ratio of the slurry.

(1) The proposed synchronous grouting slurry ratio is shown in the following table:

drawing up the ratio of synchronous grouting slurry (kg/m3)

Cement	Sand	Fly ash	Bentonite clay	Water (W)
					200	800	300	80	420

The weight of the slurry mixing material is correspondingly adjusted according to the actual situation of the site due to the influence of the change of the water content, the consistency of the uniformly mixed slurry is 10-12 cm, the admixture is added to ensure that the setting time is shorter, the setting speed is fast, the strength, particularly the early strength, of the hardenable slurry is higher, and the initial setting time is 2-4 hours (the transportation distance is 1.5 hours, and the initial setting is designed to be 1-2 hours).

The grouting material is commercial mortar mixed by a slurry mixing station of Huisen concrete company and is transported into a ground slurry storage tank for later use by a commercial concrete tank truck (fixed and specially used for transporting mortar).

Synchronous grouting slurry performance index

Coagulation time	One day compressive strength	Compressive strength of seven days	Twenty eight days compressive strength
				< 2 hours	＞0.5Mpa	＞0.8MPa	＞2MPa

(2) Secondary grouting slurry proportion

The secondary grouting is to select grouting materials and a grout ratio according to the stratum condition, and generally adopts quick-setting type double-grout pressure grouting, namely adopting a cement (PO42.5) -water glass (Baume degree 40 ℃) mixed solution. The grouting pressure is 3.0 bar-5.0 bar, and the grouting amount of each grouting hole is determined according to the actual monitoring condition of surface subsidence. The main mixture ratio is shown in the following table:

secondary grouting slurry proportion

Performance index of secondary grouting slurry

Coagulation time	One day compressive strength	Compressive strength of seven days	Twenty eight days compressive strength
				< 1 hour	＞1Mpa	＞1.5MPa	＞2MPa

5. Synchronous grouting construction

(1) Construction preparation: preparing a grouting material; checking whether the stirrer and the grouting pump are normal or not to ensure that the stirrer and the grouting pump can work normally; checking the grouting pipeline to ensure the pipeline to be smooth; the pressure display system is checked to ensure it is error free.

(2) Stirring the slurry: cement, fly ash, bentonite and the like cannot be agglomerated, and the sand adopts fine sand with the fineness modulus of 0.6-1.2, and cannot have foreign matters with large particle size; the raw material metering error is controlled within the range of the specification requirement; the materials of all the components are put in a reasonable order (water, cement and sand are carried out in sequence); stirring uniformly for about 2min without agglomeration; the slurry is required to be subjected to consistency, water content, fluidity, workability, water separation and anti-liquefaction index tests, and can be used after the tests are qualified.

(3) Transportation and storage of the slurry: the thick liquid transports to the on-the-spot storage tank of carrying with pipeline in the homemade after mixing, transports the storage tank to the working face through the section of jurisdiction flatbed, later with the thick liquid pump go into the storage tank on the shield constructs the quick-witted trailer and stir immediately. The material storage tank is provided with a horizontal stirring shaft to prevent the slurry from standing for a long time during transportation to cause initial setting; if the slurry is precipitated and separated, carrying out secondary stirring; the slurry storage facilities are cleaned frequently.

(4) The construction steps are as follows: connecting a grouting pipeline and a pressure sensor; inputting the mixed slurry into a slurry storage tank of the shield machine by a transport vehicle, and starting a stirrer to stir the slurry; grouting and propelling are carried out synchronously, the grouting speed is adapted to the propelling speed, and four pumps are needed for grouting at the same time under no special condition; the grouting fullness degree is controlled by grouting pressure and grouting amount; during the process of installing duct pieces or mucking, a part of mortar is reserved and is pumped intermittently to keep a pipeline smooth.

(5) Quality control and effect check: and (3) performing a detailed slurry mixing ratio test before grouting, selecting a proper grouting material and a proper slurry mixing ratio, and ensuring that physical and mechanical indexes such as the selected slurry mixing ratio, strength, durability and the like meet design construction requirements. And the maintenance of grouting equipment and the supply of grouting materials are well done, and the smooth, continuous and uninterrupted grouting operation is ensured. The mud jacking amount of each ring ensures that the surface settlement is controlled within a limited difference. The grouting effect inspection mainly adopts an analytical method, namely, comprehensive analysis and judgment are carried out according to a curve of p (grouting pressure) -Q (grouting amount) -t (time) by combining deformation measurement results of the lining, the ground surface and surrounding buildings.

6. Secondary grouting

Before the shield penetrates the No. 2 line, grouting and reinforcing the stratum within a certain range around the tunnel from the inside of the tunnel according to the field condition and geological data, and performing secondary grouting by adopting a quick-setting early-strength double-liquid grouting material, wherein grouting pressure control is mainly used.

The secondary grouting adopts cement-water glass double grout with the thickness of 1m³The slurry ratio is: cement (PO 42.5): water: water glass solution (40 baume) 1:1: 1;

separating from 4 rings of the shield tail, carrying out secondary grouting every 3 rings, encrypting important sections, determining the grouting amount according to the automatic monitoring and measuring condition of the No. 2 line, and timely replenishing grouting by using a low-pressure, small-amount and multiple grouting mode.

The grouting parameters including the arrangement of grouting holes, the slurry proportion, the grouting pressure, the grouting sequence, the grouting time, the grouting amount and the like are determined by the test effect and are optimized according to the monitoring feedback information in the grouting construction process.

In order to ensure that the accumulated settlement on the ground and the deformation condition of a building are effectively controlled, the unit sets a whole set of SYB hydraulic double-liquid grouting pump and a grouting material platform on a frame No. 1 of the shield machine and moves forward along with the shield machine.

Use of seven-effect and five-effect construction method

1. Brief description of the working method

Because the diameter of the cutter head is 6440mm (right line phi 6480) on the left line, the diameter of the shield body is phi 6410mm, a 30mm gap exists between the cutting soil body of the cutter head and the shield body, in order to avoid settlement of the soil body above the tunnel structure due to the gap in the process of downwards passing through a No. 2 line tunnel, a clay effect (the clay slurry and the water glass series mixture are mixed to immediately generate plastic state change, the mixture ratio is matched according to a test section) is injected through radial holes of the shield shell during the downwards passing process, a gap between the excavation diameter and the shield body is timely filled, the injection rate is 120-130%, the soil body is prevented from settling above the shield body, and the settlement is controlled within an allowable range. The upper tunnel (left line) middle shield is provided with 8 grouting holes, the lower tunnel (right line) middle shield is provided with 7 grouting holes, and 4 holes are selected on the upper half of the tunnel at this time for injection test.

Preliminarily determining that the injection material is a high-concentration muddy water material and a plastic-phase modifier (namely water glass) which are delivered to a designated position to be mixed into a high-viscosity plastic gel, and after the mixture is mixed, the reaction is completed within 4s-20s, and the diffusion radius is 1m-1.5 m.

The mixed fluid plastomer is not easy to be diluted by water, and the viscosity of the fluid plastomer does not change along with time.

2. Construction parameters for restraining mud effect

The construction parameters of the mud effect are adjusted by combining the initial values of manufacturers with the parameters of the test section, and the selection parameters during downward penetration are determined. The selection mode of the parameters is that the shield is normally tunneled 30 rings before entering a general test section, and monitoring data of the section is collected. And (3) carrying out a middle shield 'g mud effect' test on the 2 nd ring, wherein the parameters to be used are 182.7 kg/ring on the right line and 181.6 kg/ring on the left line, comparing the monitoring data of the front 30 rings after the completion of the propelling, carrying out analytical research, and determining the proportioning parameter of the g mud effect material when the subway passes through the No. 2 line. 3. Application range of soil-effect-restraining construction method

The entry into a risk source is started ten times in advance, and the mud restraining effect is synchronously injected from the radial hole at the shield position in the shield machine, so that the gap between the shield body and the soil body caused by the cutter head overexcavation in the shield construction process is timely filled, and the effect of isolating the tunneling pressure of the front soil bin and the synchronous grouting pressure of the shield tail is achieved. The injection point of the clayey effect is injected at 4 points on the middle upper part.

4. Shield machine parameters

Interval right line

Type of shield machine	Earth pressure balance shield machine	Shield machine body length	8358mm
				Diameter of excavation	6440mm	Diameter of middle shield	6400mm
Diameter of shield tail	6400mm	Radial hole location	12 dots (vault)
				Radial bore cutter head distance	2.8	Radial hole size	50A
Place platform truck serial number	6 # trolley	The equipment is long from the injection point	75m

Left line of interval

Type of shield machine	Earth pressure balance shield machine	Shield machine body length	9620
				Diameter of excavation	6480	Diameter of middle shield	6440
Diameter of shield tail	6430	Radial hole location	12 dots (vault)
				Radial bore cutter head distance	5.3	Radial hole size	50A
Place platform truck serial number		The equipment is long from the injection point

5. Down-through and down-through subway No. 2 line risk source related parameter data

6. Calculation of working amount of soil-restraining effect

7. Points of construction attention

In order to ensure the mud-restraining effect, the construction gap is effectively and timely filled in the shield construction propulsion process, the key time is won for the synchronous grouting and soil body reinforcing grouting behind the follow-up segment, and the construction parameters are as shown in the following table:

grouting treatment for deep holes in eight or eight holes

8.1 in-hole grouting protocol and scope

According to the special design concept of the protection of the lower-crossing No. 2 line, when the subway No. 2 line is crossed, the tunneling construction of the right line of the lower tunnel of the No. 4 line is firstly carried out, and then the tunneling construction of the left line of the upper tunnel of the No. 4 line is carried out. The clear distance between the lower tunnel and the No. 2 line is 11.516-11.837 m, the distance is large, and the initial judgment on the No. 2 line is small. Repeated grouting reinforcement is carried out in the tunnel hole at this stage, and the grouting pipe with the length combined is arranged to reinforce the stratum below the tunnel and the tunnel with the number 2 line on the number 4 line.

According to the design requirement, the total scheme of in-tunnel deep hole grouting is that after a No. 2 line is downwards penetrated on a right-line descending line (before a left-line tunnel is downwards penetrated), deep hole grouting treatment is carried out on the upper half part of the right-line in-tunnel (the overlapping part of the reinforcement depth and the No. 4 line left line is 1.5m, and the rest is 3.5m), after the No. 2 line is completely penetrated on the right-line tunnel, soil bodies between the upper subway No. 2 line (the reinforcement depth is 3.5m) and the lower No. 4 line right line are reinforced in the left-line tunnel (the overlapping part of the reinforcement depth and the No. 4 line right line is 1.5m, and the rest is 3.5m), and the final reinforcement effect is to increase the compactness of the soil bodies of the upper tunnel and the lower tunnel in the later operation process, the disturbance of the upper tunnel and the lower.

The deep hole slip casting is handled and is mainly utilized current section of jurisdiction slip casting hole, adopts the steel floral tube of preparation to carry out the slip casting to the soil body behind the section of jurisdiction wall and consolidate, and reinforcement scope left side line tunnel is below the tunnel middle part, and right side line tunnel middle part is above, and it is 3m to form slip casting circle thickness. The type of the grouting slurry adopts a cement water glass double-liquid slurry.

Construction process flow

Construction preparation → installation of a water stop valve → opening → insertion of a steel flower pipe (a grouting head containing a one-way valve) → cement grout injection → cutting off the part of the tempered pipe with the exposed segment, and plugging the grouting hole.

Construction method and quality control

1) And (5) manufacturing the steel perforated pipe. The steel flower pipe is processed by a phi 48 steel pipe, and the length of a single steel flower pipe is determined according to the reinforcing range. The pipe wall sets up plum blossom shape grout outlet, and interval 200mm, diameter 6mm consider section of jurisdiction structure thickness 350mm and synchronous slip casting thickness, do not set up grout outlet near the 500mm within range of floral tube slip casting head end, and the slip casting pipe front end is taken and is pounded flat laminating, is ground the point and handle.

2) Duct piece punching

The segment of the lower-penetrating No. 2 segment is an enhanced segment additionally provided with grouting holes, and the grouting holes (including segment hoisting holes and 16 grouting holes) are utilized to punch grouting pipes, so that deep hole grouting reinforcement is performed on soil bodies in a certain range around the tunnel.

The concrete method for drilling the right steel perforated pipe is that the length of a grouting pipe cannot exceed 1.5m (the steel perforated pipe cannot influence left tunneling, and the distance is only 1.8m), the initial pressure of grouting is controlled to be 0.5-0.6 bar, and the grouting pipe is increased step by step (0.1 bar/time) by combining automatic monitoring data of a tunnel of a subway No. 2 line, so that the grouting reinforcement is ensured, and meanwhile, no disturbance is carried out on the tunnel structure of the subway No. 2. The grouting adopts double-fluid static pressure grouting. 3m (grouting initial pressure 0.3-0.4 bar, gradually increased) at the upper part of the grouting pipe of the left tunnel, 3.5m at two sides (grouting initial pressure 0.3-0.4 bar at two sides of the upper part, grouting initial pressure 0.4-0.5 bar at two sides of the lower part, gradually increased), and 1.5m at the lower part (grouting initial pressure 0.4-0.5 bar, gradually increased).

3) Grouting parameters:

the grouting pressure is determined by a test section

Slurry diffusion radius: 1.5m

The grouting speed is less than or equal to 30L/min

Slurry injection amount: calculated according to the formula Q ═ R2Ln α β, where:

r-slurry diffusion radius (m);

l-slip casting pipe length (m);

n-stratum porosity (33-49% of sand powder and 41-52.4% of clay powder);

the alpha-formation filling factor is generally 0.8;

the consumption coefficient of the beta-slurry is generally 1.1-1.2.

The shield is worn No. 2 tunnel under, and the tunnel top main stratum is 2-11 circle gravel layer, and the main foundation that uses grouting pressure to control goes on, and in the work progress, the combination subway No. 2 tunnel automation monitoring data is carried out step by step (0.1 bar/time) increase with the initial pressure that the design was given, does not carry out the disturbance to subway No. 2 tunnel structure when guaranteeing that the slip casting is consolidated. (ii) a

4) Grouting pressure control: consider section of jurisdiction intensity for C50, for avoiding grouting pressure to lead to the fact the section of jurisdiction damaged, the fracture phenomenon, stop slip casting when grouting pressure reachs the control value, close the slip casting ball valve.

5) And (6) sealing the holes. Before hole sealing, the ball valve is opened in a trial mode, if slurry is solidified and water leakage does not occur, the ball valve is dismantled, the steel perforated pipe exposed outside the pipe piece is cut off, and quick-drying cement is adopted to seal holes in time.

Nine-line and right-line tunnel forming protection measure

9.1 duct piece supporting trolley protection measure

When a subway No. 2 line is penetrated downwards, a right line (offline) is constructed firstly, and the distance between a left line tunnel and the right line tunnel is only 1.8m, so that before the left line tunnel is tunneled, a temporary supporting trolley needs to be arranged in the right line to temporarily support and reinforce the left line tunnel, so that the left line tunneling process is ensured, the stress of the right line tunnel structure is safe, the temporary supporting trolley is in synchronous movement with the left line tunnel shield tunneling, the construction safety of the right line tunnel is ensured, the trolley machining length is 12m (2 m in front of a cutter head, 10m behind the cutter head and 12m in total), and the trolley keeps consistent movement with a left line shield tunneling machine. And a tunnel from the interval overlapping section DK9+400 to the train north station adopts a trolley support frame to protect the right line.

Synchronously following the upper tunnel shield tunneling machine by using a walkable profile steel support trolley, and ensuring that the shield tunneling machine is supported within a certain distance from the front and the rear; meanwhile, in order not to influence the normal construction of the tunnel below, the trolley is made into a portal frame shape, so that the slag and duct piece transportation operation is convenient.

1) The whole supporting trolley consists of 3 sections of trolleys, each section of trolley is 3m long, and the trolleys are connected in series through the pushing oil cylinders.

2) The frame interval of the trolley is 1.5m and the width of the pipe piece is the same, each section has 5 supporting wheel groups, and each wheel group is composed of 2 polyurethane rubber steel core wheels.

3) The supporting wheel sets provide supporting force by utilizing the hydraulic oil cylinder, and the maximum supporting force which can be borne by each wheel set is 25 t.

4) The whole trolley walks by adopting hydraulic oil cylinders for pushing, the whole trolley comprises 6 pushing oil cylinders, and the maximum pushing force of each oil cylinder is 25 t.

5) Each trolley (3m) weighs about 12 tons, and the whole trolley weighs about 36 tons.

6) A trolley walking step:

firstly, the 1# trolley is pushed forwards by utilizing a pushing oil cylinder between the 1# trolley and the 2# trolley (the 2# trolley and the 3# trolley are used as reaction trolleys at the moment);

then, the 2# trolley is pushed forwards by the combined action of the pushing oil cylinders of the 1# trolley and the 2# trolley and the 3# trolley (the 1# trolley and the 3# trolley are used as reaction trolleys at the moment);

finally, the 3# trolley is pulled forwards by utilizing a pushing oil cylinder between the 2# trolley and the 3# trolley (the 1# trolley and the 2# trolley are used as reaction trolleys at the moment);

during pushing, in order to prevent the reaction trolley from moving, wood wedges can be plugged between the travelling wheels and the tracks of the reaction trolley as required.

7) Other accessories of the trolley:

hydraulic station-1

Top pushing oil cylinder-8

Support polyurethane steel wheel-90

Supporting oil cylinder-45

Walking steel wheel-24 pieces

9.2, construction Process notes

1. The left line shield machine operation room and the mobile trolley are required to be mutually connected at any time, if the shield machine or the supporting trolley breaks down, the corresponding supporting trolley or the left line shield machine is required to stop advancing until the back can recover the tunneling and the advancing after mutual confirmation of fault elimination.

2. Under the thrust of external force, the trolley can move forwards along the longitudinal direction without unloading force. The supporting points need to avoid the longitudinal seam position and the hand hole position, the minimum rigidity of the steel support is estimated in advance according to the maximum internal force possibly borne by the support and the allowable value of the uneven deformation of the tunnel during the design of the trolley, and the support has a pressure adjusting function.

3. The left-line shield tunneling machine needs to stably, continuously and quickly tunnel in the process of tunneling the stacked tunnel, the posture of the shield tunneling machine is strictly controlled, the phenomenon that the shield tunneling machine is mounted at the head cannot occur, and if the deviation needs to be corrected, the deviation correction amount cannot be overlarge.

9.3 segment Reinforcement

The left and right tunnels passing through the lower section of the shield tunnel are both provided with reinforced duct pieces (the steel content of the duct piece reinforcement is increased to 215kg/m3) and bolts (8.8-grade bolts) so as to improve the strength and the deformability of the duct pieces.

It should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention, and they should be construed as being included in the following claims and description.

Claims

1. A high water-rich round gravel stratum earth pressure balance shield fast tunneling construction method comprises an existing tunnel and an upper tunnel and a lower tunnel which penetrate the existing tunnel, and is characterized in that the upper tunnel and the lower tunnel are arranged in the existing tunnel; firstly, performing lower tunnel tunneling construction, then performing deep hole grouting treatment in the upper half of the lower tunnel, then performing upper tunnel tunneling construction, and finally performing deep hole grouting treatment in the upper half and the lower half of the upper tunnel.

2. The soil pressure balance shield rapid tunneling construction method for the water-rich round gravel stratum according to claim 1, which is characterized in that: and the deep hole grouting treatment in the holes of the lower tunnel and the upper tunnel comprises inserting grouting pipes, injecting grout and plugging grouting holes.

3. The soil pressure balance shield rapid tunneling construction method for the water-rich round gravel stratum according to claim 2, which is characterized in that: the slurry adopts cement-water glass double slurry and adopts static pressure grouting.

4. The soil pressure balance shield rapid tunneling construction method for the water-rich round gravel stratum according to claim 3, which is characterized in that: and D, adopting a phi 48 steel pipe as a grouting pipe for grouting treatment of the deep holes in the holes, adopting smashing, flattening, laminating and sharpening treatment on the front end of the steel pipe, and opening a plurality of grout outlet holes on the pipe wall of the steel pipe except for 500mm from the grouting head end, wherein the diameter d of each grout outlet hole is 6mm, and the distance L between every two adjacent grout outlet holes along the axial direction of the steel pipe is 200 mm.

5. The soil pressure balance shield rapid tunneling construction method for the water-rich round gravel stratum according to claim 4, which is characterized in that: the grouting pipes of each grouting section of the lower tunnel comprise four first grouting pipes and three second grouting pipes, and the second grouting pipes are shorter than the first grouting pipes; the included angles between the four first grouting pipes and the horizontal plane are respectively 22.5 degrees, 45 degrees, 135 degrees and 157.5 degrees, and the included angles between the three second grouting pipes and the horizontal plane are respectively 67.5 degrees, 90 degrees and 112.5 degrees.

6. The soil pressure balance shield rapid tunneling construction method for the water-rich round gravel stratum according to claim 5, which is characterized in that: the grouting pipes of each grouting section of the upper tunnel comprise four third grouting pipes and three fourth grouting pipes which are positioned at the lower half part of the upper tunnel, and four fifth grouting pipes and three sixth grouting pipes which are positioned at the upper half part of the upper tunnel; the fourth grouting pipe and the second grouting pipe are equal in length, the third grouting pipe and the fifth grouting pipe are equal in length to the first grouting pipe, and the length of the sixth grouting pipe is between the length of the fifth grouting pipe and the length of the fourth grouting pipe; the included angles between the four third grouting pipes and the fifth grouting pipes and the horizontal plane are respectively 22.5 degrees, 45 degrees, 135 degrees and 157.5 degrees, and the included angles between the three fourth grouting pipes and the sixth grouting pipes and the horizontal plane are respectively 67.5 degrees, 90 degrees and 112.5 degrees.

7. The earth pressure balance shield rapid tunneling construction method for the water-rich round gravel stratum according to any one of claims 1 to 6, which is characterized in that: when the upper tunnel and the lower tunnel are subjected to tunneling construction, the method further comprises the following four stages:

8. The earth pressure balance shield rapid tunneling construction method for the water-rich round gravel stratum according to claim 7, which is characterized in that: and injecting the gram mud effect into the first stage, the second stage and the third stage through radial holes of the shield shell, wherein injection points of the gram mud effect are at 1 o 'clock and 11 o' clock positions.

9. The earth pressure balance shield rapid tunneling construction method for the water-rich round gravel stratum according to claim 8, which is characterized in that: in the construction of the first stage, the second stage and the third stage, synchronous grouting is carried out when the duct piece is separated from the shield tail, and each five-ring duct piece is sealed once by using cement-water glass double-slurry.