CN114908798A

CN114908798A - Subway protection construction method for excavating above existing subway section

Info

Publication number: CN114908798A
Application number: CN202210509138.9A
Authority: CN
Inventors: 伍永胜; 李红波; 农兴中; 钟颜开; 李豪; 张畅; 刘应山; 陈玉清
Original assignee: Guangzhou Metro Design and Research Institute Co Ltd
Current assignee: Guangzhou Metro Design and Research Institute Co Ltd
Priority date: 2022-05-11
Filing date: 2022-05-11
Publication date: 2022-08-16

Abstract

The invention belongs to the technical field of subway construction, and provides a subway protection construction method for excavating above an existing subway interval, which mainly comprises the following steps: s1, arranging a foundation pit space to be excavated at the ground where the subway tunnel is buried, and performing stirring pile foundation construction between the top of the subway tunnel and the foundation pit space to be excavated to form a first stirring pile; s2, constructing stirring pile foundations on two sides of the subway tunnel to form second stirring piles; s3, connecting the first stirring pile and the second stirring pile, and wrapping the periphery of the subway tunnel with a waterproof layer to form a protective shell; s4, performing local reinforcement treatment on a gap between the subway tunnel and the stirring pile; s5, arranging a water pressure adjusting device on the ground; s6, performing foundation pit excavation construction, and adjusting the water pressure in the protective shell through the water pressure adjusting device, the invention can control the peripheral water pressure of the foundation pit excavation construction above the subway, thereby realizing the inhibition of subway deformation and reducing the construction risk.

Description

Subway protection construction method for excavating above existing subway section

Technical Field

The invention belongs to the technical field of subway construction, and particularly relates to a subway protection construction method for excavating above an existing subway section.

Background

At present, along with the continuous development of cities, the real estate development close to subways is more and more, but due to the continuous reduction of the area of the exploitable land, more and more projects are closer to the subways, but the projects which are just above the subways and are close to the subways at the bottom of a pit are rare in China, and how to protect the existing subway projects becomes a key problem facing the current time.

As a plurality of subways are positioned in a soft soil layer, if the upper part of the interval is excavated, the subway is inevitably affected adversely.

In the current subway protection scheme, grouting in a tunnel interval and grouting of sleeve valve pipes are the better solution at present.

The grouting scheme in the interval tunnel is relatively controllable, and the reinforcing effect is good. However, because the subway is in operation, the window time of each construction is very short, the requirement on the construction is high, and certain risk is caused to the operation safety.

Ground grouting such as sleeve valve pipes is also a better solution, can be grouted on the ground, has little influence on subway operation, but has unstable grouting range, grouting area, grouting effect and the like and poor controllability due to the need of drilling longer holes for grouting.

Even if the existing subway is grouted and reinforced, the problem of subway deformation in the excavation process is unavoidable. In the excavation process, the strong changes of water pressure and soil pressure around the tunnel are inevitably brought, and the changes result in larger ellipse change of the subway or floating of the subway.

And because the uncertainty that construction quality brought can lead to the foundation ditch inevitable that implements to leak, can lead to the subway peripheral soil body to be hollowed when discharge is great, present implementation scheme all lacks effective control means to leaking that foundation ditch defect leads to.

The prior art is limited on a grouting reinforced soil layer, but the quality of the pure reinforced soil layer is difficult to control, and the pressure caused by grouting per se can influence the subway to a certain extent. The grouting in the interval has the defects that the construction window time is short, the construction has large influence on the operation, and the grouting of the sleeve valve pipe has the main defects of weaker controllability and uncontrollable reinforcing range and reinforcing effect. Because enough safe distance needs to be kept between the subway and the cement soil mixing piles, the cement soil mixing piles can not effectively intercept water, and thus, no case for large-scale adoption exists in the subway at present. Because the construction is impossible to be perfect, the phenomenon of foundation pit water leakage can be inevitably generated, the problem does not exist for the common foundation pit, but the subway deformation and the risk are possibly generated for the foundation pit above the subway. The existing technology cannot well control the water pressure around the subway, so that the deformation of the subway is difficult to control. Traditional foundation ditch seals the foundation ditch bottom completely, does not let rivers pass through, has caused water pressure to be static water pressure objectively, and the hole has how deeply, and water pressure is big enough, leads to traditional foundation ditch way also can not dig too deeply on the subway. Because the water pressure is not well controlled, the excavation depth is limited above the subway, and even the construction method for excavating above the tunnel rarely occurs in China.

Disclosure of Invention

In order to overcome the above disadvantages of the prior art, an object of the present invention is to provide a method for protecting a subway which excavates above an existing subway section, so as to control the peripheral water pressure for excavation of a foundation pit above the subway, thereby suppressing deformation of the subway and reducing the construction risk.

The technical scheme adopted by the invention for solving the technical problems is as follows:

a subway protection construction method for excavating above an existing subway section comprises the following steps:

s1, arranging a foundation pit space to be excavated at the ground where the subway tunnel is buried, and carrying out stirring pile foundation construction between the top of the subway tunnel and the foundation pit space to be excavated to form a first stirring pile;

s2, performing stirring pile foundation construction on two sides of the subway tunnel to form a second stirring pile, wherein the depth of the second stirring pile is as deep as a watertight layer below the subway tunnel;

s3, connecting the first stirring pile and the second stirring pile, and wrapping the periphery of the subway tunnel with the impervious layer to form a protective shell;

s4, performing local reinforcement treatment on a gap between the subway tunnel and the stirring pile;

s5, arranging a water pressure adjusting device on the ground, wherein the water pressure adjusting device is communicated with the protective shell;

and S6, performing foundation pit excavation construction at the position of the foundation pit space to be excavated, and adjusting the water pressure in the protective shell through a water pressure adjusting device.

Preferably, in step S1, the first mixing piles are horizontally arranged along the extension direction of the subway tunnel.

Preferably, in steps S1 and S2, the mixing pile foundation construction includes the steps of:

s11, carrying out process experiment piles according to geological actual conditions and mechanical equipment conditions, and determining various actually adopted technical parameters, pile forming processes and construction steps, including water-cement ratio of slurry, sinking or lifting speed, pressure-feeding capacity of a slurry pump and grouting amount of pile length per meter so as to guide next cement-soil stirring;

s12, in the grouting stage, ensuring the grouting uniformity of the whole pile, if the grouting pipeline is blocked, immediately stopping the pump to clear the blockage, immediately lifting or sinking the stirring drilling tool for 1.0m after the treatment is finished, then grouting, and resuming the normal stirring after 10-20 seconds;

s13, the construction interval time of adjacent piles cannot exceed 24 hours: if the time is out due to reasons, the step speed must be slowed down in the lapping construction to ensure the lapping quality; if the lap joint cannot be carried out or the lap joint is poor due to too long time, the cold joint is recorded on a case and is confirmed by a supervision and design unit, and technical measures such as stirring piles or jet grouting piles are carried out at the lap joint;

s14, when the ground ditch or underground pipeline is touched and can not be constructed according to the design trend, negotiating with the design unit, the owner and the proctorial to determine the new trend.

Preferably, in step s11, the test piles of the process experimental pile are not less than 3 groups, and the construction adopts double-spraying and double-stirring.

Preferably, in step S2, a third mixing pile is formed by performing a partial mixing pile foundation deepening construction at a bottom position of the first mixing pile, and the third mixing pile is located between the two second mixing piles.

Preferably, in step S4, the position of the local reinforcing treatment includes a gap between the third stirring pile and the second stirring pile, and a gap between the second stirring pile and the waterproof layer.

Preferably, in step S4, the local reinforcement processing is grouting reinforcement processing.

Preferably, in step S5, the water pressure adjusting device includes a water flow limiting device and a pressure stabilizing adjusting well;

the water flow limiting device comprises a water pump, a pressure gauge, an adjustable flow valve and a water delivery pipeline, the pressure stabilizing adjusting well penetrates through a foundation pit digging space arranged on the ground, one end of the pressure stabilizing adjusting well is connected with the water flow limiting device, and the other end of the pressure stabilizing adjusting well extends into the protective shell.

Preferably, one end of the water pipeline is connected with one end of the pressure-stabilizing adjusting well, the other end of the water pipeline is connected with the output end of the water pump, the pressure gauge and the adjustable flow valve are arranged on the water pipeline, and a plugging plate is arranged at the joint of the water pipeline and the pressure-stabilizing adjusting well.

Preferably, the steady voltage well stretches into one end in the protective housing is established to stretch into the end, stretch into the end including stretching into the pipe the peripheral outside from inside that stretches into the pipe wraps up in proper order has filter screen and filter material the pipe wall that stretches into the pipe is equipped with a plurality of through-holes the bottom that stretches into the pipe is equipped with and is used for fixing the steel sheet spare that filter screen and filter were strained.

Compared with the prior art, the invention has the beneficial effects that:

to the subway tunnel setting formation surrounding type's that buries underground in this scheme protection casing, can adjust the peripheral pressure of subway tunnel through water pressure adjusting device, when guaranteeing to carry out foundation ditch excavation construction in the subway tunnel top, the peripheral hydraulic stability of subway tunnel to promote the security of foundation ditch excavation construction, reduce the possibility that the subway warp when excavating the construction, promote the degree of depth of foundation ditch excavation construction through the peripheral pressure of adjustment subway tunnel simultaneously, promote subway top land utilization. And because be provided with the protection casing around subway tunnel, can effectively protect subway tunnel.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a relative position relationship diagram of a subway tunnel and a space of a foundation pit to be excavated in the invention.

Fig. 2 is a relative position relationship diagram of the subway tunnel and the protective shell in the invention.

Fig. 3 is a schematic view of the position of the local reinforcement treatment in the present invention.

Fig. 4 is a schematic view of an embodiment of the present invention using a long row of piles.

Fig. 5 is a schematic structural view of the water pressure regulating apparatus of the present invention.

FIG. 6 is a flow chart of the present invention.

Wherein:

the method comprises the following steps of 1-subway tunnel, 2-planned excavation of foundation pit space, 3-first stirring pile, 4-second stirring pile, 5-impervious layer, 6-third stirring pile, 7-grouting reinforcement soil body, 8-pressure stabilizing adjusting well, 9-water pump, 10-pressure gauge, 11-adjustable flow valve, 12-water pipeline, 13-extension pipe, 14-filter screen, 15-filter material, 16-through hole, 17-steel plate piece and 18-outward discharge stirring pile.

Detailed Description

In order that the above objects, features and advantages of the present invention can be more clearly understood, a detailed description of the present invention will be made with reference to the accompanying drawings and detailed description. In addition, the embodiments and features of the embodiments of the present application may be combined with each other without conflict. In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention, and the described embodiments are merely a subset of the embodiments of the present invention, rather than a complete embodiment. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

Example 1

As shown in fig. 1 to 6, the present embodiment provides a subway protection method for excavating above an existing subway section, including the following steps:

s1, arranging a foundation pit space 2 to be excavated at the ground where the subway tunnel 1 is buried, and performing mixing pile foundation construction between the top of the subway tunnel 1 and the foundation pit space 2 to be excavated to form a first mixing pile 3;

s2, performing mixing pile foundation construction on two sides of the subway tunnel 1 to form a second mixing pile 4, wherein the depth of the second mixing pile 4 is as deep as a watertight layer 5 below the subway tunnel 1;

specifically, the construction of the mixing pile foundation in the above S1 and S2 includes the following steps:

the construction of the pile-forming process adopts a triaxial mixing pile, and the process parameters are as follows:

pile diameter of the mixing pile: 850mm, lap joint between piles: 250mm, initial setting time: 45min, pile forming verticality error: less than or equal to 1 percent, and the recommended value of the cement mixing amount is as follows: 15-20%, and the recommended water-cement ratio value: 0.6-0.8, (finally determining the cement mixing amount and the water cement ratio according to the test pile result), and the pile diameter deviation: less than or equal to 50mm, and the suggested value of sinking speed: 0.38-0.75 m/min, recommended lifting speed value: not more than 0.5m/min, repeatedly stirring and increasing the suggested value of speed: 0.8-1.0 m/min;

specifically, at least 3 groups of test piles are adopted in the process experiment pile, and double-spraying and double-stirring are adopted in construction;

s12, in the grouting stage, in order to prevent the grouting phenomenon, the grouting pipeline cannot be blocked, the grouting of the whole pile is ensured to be uniform, the sandwich layer is prevented from being generated, if the grouting pipeline is blocked, the pump is immediately stopped for clearing the blockage, after the treatment is finished, the stirring drilling tool is immediately lifted or sunk for 1.0m for grouting, and after 10-20 seconds, the normal stirring is resumed so as to prevent the pile from being broken;

s13, the construction interval time of adjacent piles cannot exceed 24 hours: if the time is out due to reasons, the step speed must be slowed down in the lapping construction to ensure the lapping quality; if the lap joint cannot be carried out or the lap joint is poor due to too long time, the cold joint is recorded on a case, and after the cold joint is confirmed by a supervision and design unit, technical measures such as stirring piles or jet grouting piles are carried out at a lap joint, so that the construction quality of the stirring piles is ensured;

The first mixing pile 3 and the second mixing pile 4 have the same structure.

S3, connecting the first mixing pile 3 and the second mixing pile 4, and wrapping the periphery of the subway tunnel 1 with the impervious layer 5 to form a protective shell, wherein the protective shell is used for reinforcing the soil structure strength of the ground and has a water-proof characteristic, so that the subway tunnel 1 can be protected on one hand, and an impervious structure is formed on the other hand;

s4, performing local reinforcement treatment on a gap between the subway tunnel 1 and the stirring pile;

and S6, performing foundation pit excavation construction at the position of the foundation pit space 2 to be excavated, and adjusting the water pressure in the protective shell through a water pressure adjusting device.

The subway protection construction method adopted by the scheme enables safe excavation above the subway to be possible, the first stirring pile 3 arranged below the excavation-planned foundation pit space 2 is arranged at the ground position where the subway tunnel 1 is buried, the second stirring pile 4 and the protective shell formed by the impervious layer 5 can effectively protect the subway tunnel 1, the pressure at the periphery of the subway tunnel 1 can be adjusted through the water pressure adjusting device, the stability of the water pressure at the periphery of the subway tunnel 1 is ensured when foundation pit excavation construction is carried out above the subway tunnel 1, the safety of the foundation pit excavation construction is improved, the possibility of deformation of the subway during the excavation construction is reduced, meanwhile, the depth of the foundation pit excavation construction is improved through adjusting the pressure at the periphery of the subway tunnel 1, and the utilization rate of the ground above the subway is improved.

The gap between the subway tunnel 1 and the stirring pile is locally reinforced, so that the underground water is further prevented from flowing into the protective shell, the communication of the underground water in the protective shell and outside the protective shell is reduced, the resistance is increased to the soil body on the ground, a certain reverse filtering measure is formed, the flow speed of flowing water caused by the difference of the pressure of the water inside and outside the protective shell is reduced, the water pressure is stabilized, and the structure is stabilized.

Specifically, in step S1, the first mixing piles 3 are horizontally arranged along the extending direction of the subway tunnel 1.

Specifically, in step S2, a third mixing pile 6 is formed by performing a partial mixing pile foundation deepening construction at the bottom position of the first mixing pile 3, and the third mixing pile 6 is located between the two second mixing piles 4. The third mixing pile 6 is arranged to further strengthen the structure of the protective casing.

Specifically, in step S4, the positions of the local reinforcement treatment include a gap between the third mixing pile 6 and the second mixing pile 4, and a gap between the second mixing pile 4 and the impermeable layer 5.

Specifically, in step S4, the local reinforcement treatment is a grouting reinforcement treatment and forms a grouting-reinforced soil body 7.

Specifically, in step S5, the water pressure adjusting device includes a water flow limiting device and a pressure stabilizing adjusting well 8;

the water flow limiting device comprises a water pump 9, a pressure gauge 10, an adjustable flow valve 11 and a water delivery pipeline 12, the pressure stabilizing adjusting well 8 penetrates through a foundation pit digging space arranged on the ground, one end of the pressure stabilizing adjusting well 8 is connected with the water flow limiting device, and the other end of the pressure stabilizing adjusting well 8 extends into the protective shell.

Specifically, one end of the water pipe 12 is connected with one end of the pressure-stabilizing regulation well 8, the other end of the water pipe 12 is connected with the output end of the water pump 9, the pressure gauge 10 and the adjustable flow valve 11 are arranged on the water pipe 12, and a plugging plate is arranged at the joint of the water pipe 12 and the pressure-stabilizing regulation well 8.

Specifically, the steady voltage well stretches into one end in the protective housing is established to stretch into the end, stretch into the end including stretching into pipe 13 the periphery that stretches into pipe 13 has wrapped up filter screen 14 and filter material 15 outside from inside in proper order the pipe wall that stretches into pipe 13 is equipped with a plurality of through-holes 16 the bottom that stretches into pipe 13 is equipped with and is used for fixing the steel sheet spare 17 that filter screen 14 and filter were strained.

The working principle of the water pressure adjusting device is as follows:

can draw water and moisturizing through water pump 9, have the valve of hydromanometer and control flow, the water flow can be adjusted to the valve, and if water pressure is higher, water pump 9 starts to draw water, if water pressure crosses lowly, water pump 9 carries out the moisturizing, maintains the relatively stable pressure in the protective housing.

Specifically, the method comprises the following steps: through the well internal pressure of adjusting steady voltage regulation well 8, reduce the internal pressure of protection casing, avoid protection casing top pressure too big to lead to the foundation ditch bottom to be burst by water pressure, can increase the foundation ditch degree of depth like this, can not produce the foundation ditch bottom and gush suddenly, increaseed land use rate. Through adjusting 8 well internal pressure of steady voltage regulation well, avoid traditional precipitation mode directly to reduce tunnel pressure to lower degree, the pressure in protection tunnel can not change too greatly, owing to controlled the inside and outside pressure differential of protection casing, reduce because the displacement that the foundation ditch excavation leads to, owing to controlled the inside and outside pressure differential of protection casing, it is too big to reduce because the foundation ditch drainage, the rivers velocity of flow that leak at the bottom of the foundation ditch etc. lead to, further protection the safety of subway. When emergency conditions such as foundation pit water leakage and water level rapid change occur, the pressure around the subway can be maintained through the pressure stabilizing well, and enough time is reserved for rush repair.

As shown in fig. 4, under the condition that the field allows, the grouting can be replaced by two rows of piles with longer distance, such as the outer row of stirring piles 18, so as to realize local reinforcement treatment, and the flow velocity of flowing water flow caused by the difference of the internal and external water pressure of the protective shell is reduced by prolonging the inflow path of water, so that a better reverse filtering effect can be achieved.

In conclusion, the subway protection construction method for excavating above the existing subway section is provided by the scheme, so that the peripheral water pressure for performing foundation pit excavation construction above the subway is controlled, the deformation of the subway is restrained, and the construction risk is reduced.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, so that any modification, equivalent change and modification made to the above embodiment according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.

Claims

1. A subway protection construction method for excavating above an existing subway section is characterized by comprising the following steps:

s1, arranging a foundation pit space to be excavated at the ground where the subway tunnel is buried, and performing stirring pile foundation construction between the top of the subway tunnel and the foundation pit space to be excavated to form a first stirring pile;

s2, performing stirring pile foundation construction on two sides of the subway tunnel to form a second stirring pile, wherein the depth of the second stirring pile is as deep as a water-impermeable layer below the subway tunnel;

2. A method for protecting a subway as claimed in claim 1, wherein said first mixing piles are horizontally arranged along an extending direction of said subway tunnel in step S1.

3. A subway protection method as claimed in claim 1, wherein the construction of the mixing pile foundation in steps S1 and S2 includes the steps of:

4. A subway protection construction method as claimed in claim 3, wherein in step s11, test piles of process experimental piles are not less than 3 groups, and construction is performed by using double-spraying and double-stirring.

5. A method for protecting a subway excavated above an existing subway section according to claim 1, wherein a third mixing pile is formed by performing a partial mixing pile foundation deepening construction at a bottom position of the first mixing pile, and the third mixing pile is located between the two second mixing piles in step S2.

6. A subway protection method as claimed in claim 5, wherein said local reinforcement processing position includes a gap between said third stirring pile and said second stirring pile and a gap between said second stirring pile and said watertight layer in step S4.

7. A subway protection method as claimed in claim 1, wherein said local reinforcement processing is a grouting reinforcement processing in step S4.

8. A subway protection method as claimed in claim 1, wherein said water pressure adjusting means includes a water flow limiting means and a pressure stabilizing adjusting well at step S5;

9. A subway protection construction method for excavating above an existing subway section as claimed in claim 8, wherein one end of said water pipe is connected to one end of said pressure stabilizing regulation well, the other end of said water pipe is connected to an output end of said water pump, said pressure gauge and said adjustable flow valve are provided in said water pipe, and a plugging plate is provided at the junction of said water pipe and said pressure stabilizing regulation well.

10. A subway protection construction method for excavating above an existing subway section as claimed in claim 8, wherein one end of said pressure stabilizing well extending into said protective casing is an extending end, said extending end includes an extending pipe, a filter screen and a filter material are sequentially wrapped around said extending pipe from inside to outside, a plurality of through holes are provided on the pipe wall of said extending pipe, and a steel plate member for fixing said filter screen and said filter material is provided on the bottom of said extending pipe.