CN112359819A

CN112359819A - Wall structure construction method for increasing depth of old diaphragm wall

Info

Publication number: CN112359819A
Application number: CN202011236117.1A
Authority: CN
Inventors: 童立元; 杨涛; 李丹; 潘皇宋; 车鸿博
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2020-11-09
Filing date: 2020-11-09
Publication date: 2021-02-12
Anticipated expiration: 2040-11-09
Also published as: CN112359819B

Abstract

The invention discloses a wall structure construction method for increasing the depth of an old diaphragm wall, which comprises the steps of installing a guide pipe near the bottom of an old wall of a foundation pit and pouring the guide wall, drilling and excavating by a drilling machine through the guide pipe, guiding in steel pipes with holes of corresponding lengths according to a certain interval, and finally injecting grout into the steel pipes to fill and fill grout in the steel pipes and gaps between the steel pipes and surrounding soil bodies, so that a wall structure with certain strength is formed. The guide wall, the interior of the wall structure pit and the part below the bottom of the wall structure pit form a simply supported beam structure, and the deformation of the surrounding soil body caused by excavation of the foundation pit can be effectively reduced. Meanwhile, the newly-built wall structure and the existing diaphragm wall form a closed water stop structure, so that the influence of the pumping and dewatering of the foundation pit on surrounding structures and the structure of the foundation pit can be greatly reduced.

Description

Wall structure construction method for increasing depth of old diaphragm wall

Technical Field

The invention belongs to the technical field of civil engineering construction, and particularly relates to a wall structure construction method for increasing the depth of an old diaphragm wall.

Background

With the rapid development of urban underground space, a plurality of new and old underground structures with different depth levels and different construction periods but close construction positions appear. The construction of proximity engineering often can produce great influence to having engineering safety operation, for example when the foundation ditch diaphragm wall is under construction to municipal tunnel one side, the disturbance and the uninstallation effect of soil body can change the soil body stress state around and cause the displacement of soil body to cause the condition such as settlement, fracture, the change of leaking and the structure internal stress in tunnel, cause the influence to subway tunnel's safety operation. In order to reduce the influence of new construction on the existing underground structure as much as possible and achieve the purposes of saving resources, shortening construction period and the like, more and more new underground constructions can utilize the existing underground supporting structure. The newly-built proximity foundation pit engineering utilizes the old underground diaphragm wall of the existing underground engineering (such as municipal traffic tunnels, underground comprehensive pipe galleries and the like) as a typical working condition.

In above-mentioned operating mode, the old diaphragm wall degree of depth is not enough can bring very big safety risk for the foundation ditch construction. For example, when a deep and large foundation pit is excavated in an area containing a confined aquifer, the old diaphragm wall cannot completely block the aquifer, and thus construction disasters such as foundation pit inrush and the like occur. Meanwhile, the risk of overlarge deformation of the diaphragm wall in the excavation process can be increased due to the fact that the insertion ratio of the diaphragm wall is insufficient. Therefore, the wall structure construction method for increasing the depth of the old diaphragm wall has important practical significance.

Disclosure of Invention

In order to solve the problems, the invention discloses a wall structure construction method for increasing the depth of an old diaphragm wall, when a foundation pit is excavated to a proper depth, a guide wall is constructed at the old diaphragm wall according to the design requirements of the foundation pit diaphragm wall, a steel pipe is drilled and grouting is completed to form a wall structure of the old diaphragm wall, so that the effect of cutting off a target aquifer to reduce the risk of sudden gushing at the bottom of the pit and increase the insertion ratio to reduce the horizontal displacement of the diaphragm wall is achieved, and the construction safety of the foundation pit excavation is ensured.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a wall structure construction method for increasing the depth of an old diaphragm wall comprises the following steps:

(1) determining the lap joint position of the old diaphragm wall and the newly-built wall structure by combining the conditions of the engineering hydrological geologic body and the actual construction scheme;

(2) leveling a construction area of a newly-built wall structure, and prefabricating a lap joint body consisting of a drill hole guide pipe, section steel, a template and a reinforcing mesh;

(3) pouring the lap joint to form a guide wall;

(4) performing spiral drilling and pipe following drilling to finish embedding of the steel pipe;

(5) and grouting the embedded steel pipe through the grouting pipe to complete the construction of the newly-built wall structure.

Preferably, in the step (1), a finite element numerical simulation analysis calculation method is adopted, a horizontal displacement deformation control standard of the foundation pit enclosure wall is taken as a limiting condition, and a foundation pit excavation depth range which may cause the horizontal displacement deformation of the old diaphragm wall to be overlarge is determined, so that the lap joint position of the old diaphragm wall and the newly-built wall structure is determined.

Preferably, in the step (2), the foundation pit is excavated in blocks, a newly-built wall structure construction area is excavated by firstly putting slopes, then soil bodies at the pre-embedded positions of the guide walls are excavated, then a 15 cm-thick concrete cushion is laid to seal the excavation surface, and construction equipment is erected in the newly-built wall structure construction area.

Preferably, in the step (2), the drill guide pipe is a steel pipe with the length of 2m and the wall thickness of 5 mm. The support profile steel and the steel template are welded to form an overlap joint base of the guide pipe, the distance between the guide pipes is 50cm, and a reinforcing mesh is welded outside the guide steel pipe to strengthen the fixation of the guide steel pipe. According to the excavation width of the foundation pit, the large robber body can be prefabricated in a segmented mode, hoisted in a segmented mode and finally spliced.

Preferably, in the step (3), the old diaphragm wall is chiseled at a fixed point, so that the steel bars in the old wall are welded with the lap joint body, the old wall body in the range of the guide wall is chiseled, and the contact with the guide wall is increased. When transferring the prefabricated overlap joint body, the outer inserted angle that makes the stand pipe through angular surveying is 1 ~ 2, thereby welds through splice bar and the inside reinforcing bar body of old wall and carries out the template fixed. And (3) plugging two ends of the guide pipe, then pouring C20 concrete, wherein the thickness of the guide wall body is at least 80cm, and drilling construction can be carried out after the strength of the wall body reaches 80%.

Preferably, in step (4), the steel pipe is used

Seamless steel flower tube, wall thickness 8 mm. The pipe wall is provided with grouting holes according to a quincunx shape, the aperture is 5mm, the hole spacing is 50cm, and the grouting holes are not arranged within the range of 2m at the tail part of the steel pipe. In the drilling process, the drilling angle is monitored and corrected in real time by combining an angle signal transmitted by a positioning sensor arranged in the guide drill bit, so that the steel pipe is drilled according to the designed angle. And when the designed depth is drilled, withdrawing the positioning sensor, laying a steel reinforcement cage in the steel pipe, and then performing grouting construction.

Preferably, in the step (5), the grouting pressure is controlled to be 0.6-1 MPa, and when the grouting amount is reached, the grouting pressure is stabilized for 3-5 min, and then the valve is closed to stop grouting. The grouting slurry adopts cement-water glass double-liquid slurry, the cement adopts 425 common portland cement, the concentration of the water glass is 35 baume degrees, the modulus is 2.4-3.4, the water cement ratio of the cement slurry is 1: 1, the volume ratio of cement paste to water glass is 1: 0.5. the grouting amount of a single steel pipe can be determined according to the following formula:

Q＝πr²×L+πR²×L×η×α×β

in the formula: taking 0.5m for R-radius of steel pipe, L-length of steel pipe and R-diffusion radius of slurry; eta-formation porosity; the alpha-slurry filling rate is generally 0.9; the beta-slurry loss factor is typically 1.15.

The invention has the beneficial effects that:

the wall structure construction method for increasing the depth of the old diaphragm wall, disclosed by the invention, forms a simply supported beam stress structure, namely one end of the support is positioned at the lap joint of a newly-built wall and the old diaphragm wall, and the other end of the support is positioned in the unearthed soil body, so that the horizontal displacement of the diaphragm wall caused by excavation of a foundation pit can be effectively reduced, and meanwhile, the risk brought by precipitation of the foundation pit can be reduced by cutting off a target aquifer. In addition, by utilizing the old underground diaphragm wall, the construction cost is reduced, and the influence on the existing underground engineering of the approach is effectively reduced, so that the safe operation of the underground engineering is ensured.

Drawings

FIG. 1 is a top view of the deployment orientation of the present invention;

FIG. 2 is a cross-sectional view of the deployment orientation of the present invention;

FIG. 3 is a schematic view of the internal lap joint of the guide wall and the steel pipe with holes in the newly built wall structure;

FIG. 4 is a structural view of the steel pipe with holes of the present invention;

FIG. 5 is a schematic view of the steel reinforcement cage arranged in the steel tube with holes of the present invention.

List of reference numerals:

1. a slope is set up and an excavation area (a construction area of a newly-built wall structure) is set; 2. excavating the foundation pit in blocks-excavating parts; 3. newly building a diaphragm wall; 4. old diaphragm wall; 5. a slope surface; 6. a steel form; 7. supporting the section steel; 8. drilling a guide pipe; 9. a guide wall; 10. newly building a steel pipe with holes in the wall structure; 11. newly building a wall structure; 12. a reinforcing mesh; 13. grouting holes; 14, a turnbuckle; 15. a grouting valve; 16. plugging a steel plate; 17. a grouting pipe; 18. and (4) a reinforcement cage.

Detailed Description

The present invention will be further illustrated with reference to the accompanying drawings and specific embodiments, which are to be understood as merely illustrative of the invention and not as limiting the scope of the invention.

Example (b): as shown in fig. 1, a method for constructing a wall structure to increase the depth of an old diaphragm wall, the structure includes: a foundation pit slope setting excavation area (a newly-built wall structure construction area) 1; excavating an un-excavated area 2 in a foundation pit block mode; newly building a diaphragm wall 3 in the foundation pit; approaching an old underground diaphragm wall 4 of the existing underground engineering; slope is set down and a slope surface 5 is excavated; a steel molding plate 6; section steel 7 for supporting the guide tube; a drill guide tube 8; a guide wall 9; newly building a steel pipe 10 with holes in the wall structure; newly building a wall structure 11; a reinforcing mesh 12 for fixing the guide pipe; grouting holes 13 on the steel pipes with holes; a turnbuckle 14; a grouting valve 15; a plugging steel plate 16 of the steel pipe with holes; a grouting pipe 17; a reinforcement cage 18 is arranged in the steel pipe with holes.

A wall structure construction method for increasing the depth of an old diaphragm wall specifically comprises the following steps:

(1) and (3) simulating a real construction working condition by adopting a finite element numerical simulation analysis calculation method, and determining a foundation pit excavation depth range which can cause the horizontal displacement deformation of the old diaphragm wall to exceed a control standard by taking the horizontal displacement deformation control standard of the foundation pit enclosure wall as a limiting condition, so as to determine the lap joint position of the old diaphragm wall 4 and the newly-built wall 3 structure.

(2) The soil above the top surface of the guide wall 9 is excavated in blocks, and a newly constructed wall structure construction area (as indicated by 1 in fig. 1) is excavated by slope excavation. After the area is initially leveled, soil bodies at the pre-embedded positions of the guide walls are excavated, the length of each guide wall body 9 (namely the lap joint length of the old diaphragm wall and the newly-built wall body) is at least 2m, and the thickness of each guide wall body is at least 80 cm. And (5) laying a 15cm rear concrete cushion layer to seal all excavation surfaces, and then erecting construction equipment in a newly-built wall structure construction area 1.

(3) And (3) when the construction area 1 of the newly-built wall structure is dug up, prefabricating the lap joint body of the drill hole guide pipe 8, the section steel 7, the formwork 6 and the reinforcing mesh 12 (as shown in figure 2). The drill guide pipe 8 is a steel pipe with the length of 2m and the wall thickness of 5mm, and the inner diameter of the drill guide pipe is larger than the outer diameter of the steel pipe with holes 10 (grouting steel pipe) within 10 mm. The support section steel 7 and the steel template 6 are welded to form an overlap joint base of the

guide pipe

8, and 3 channels of section steel are suggested to be welded. The distance between the guide pipes 8 is 50cm, and a reinforcing mesh is welded outside the guide steel pipes to strengthen the fixation of the guide steel pipes. According to the excavation width of the foundation pit, the lap joint body can be prefabricated in a segmented mode.

(4) Before the lapping body is hoisted, the old diaphragm wall 4 is chiseled at a fixed point, so that the internal steel bars of the old wall can be welded with the lapping body, and the old wall body in the range of the guide wall is chiseled to increase the contact with the guide wall 9. When transferring the prefabricated overlap joint body, make the outer inserted angle of stand pipe be 1 ~ 2 through the angle measurement operation to it is fixed to carry out the template through splice bar and the inside reinforcing bar body of old wall welding. And then, two ends of the guide pipe are blocked, and C20 concrete is poured to form the guide wall (as shown in figure 3), and drilling construction can be carried out after the strength of the wall reaches 80%.

(5) And (3) performing spiral drilling and pipe following drilling, and monitoring and correcting the drilling angle in real time by combining an angle signal transmitted by a positioning sensor arranged in the guide drill bit in the drilling process so that the steel pipe drills according to the designed angle (the steel pipe 10 is inserted into the guide pipe 8). When the design depth is reached, the position sensor is withdrawn and the reinforcement cage 18 is deployed into the interior of the steel pipe 10. Wherein, the steel pipe adopts phi 219 seamless steel floral tube, the wall thickness is 8 mm. The pipe wall is provided with grouting holes according to a quincunx shape, the aperture is 5mm, the hole spacing is 50cm, and the grouting holes 13 are not arranged within the range of 2m at the tail part of the steel pipe.

(6) And (5) plugging the tail of the steel pipe and starting grouting. And controlling the grouting pressure to be 0.6-1 MPa preferably, and when the grouting amount is reached, stabilizing the grouting pressure for 3-5 min and closing the valve 15 to stop grouting. The grouting slurry is recommended to be cement-water glass double-liquid slurry, the cement is 425 ordinary portland cement, the water glass concentration is 35 baume degrees, the modulus is 2.4-3.4, and the water cement ratio of the cement slurry is 1: 1, the volume ratio of cement paste to water glass is 1: 0.5. the grouting amount of a single steel pipe can be determined according to the following formula:

Q＝πr²×L+πR²×L×η×α×β

The wall structure similar to the stress characteristic of a simply supported beam can be formed by grouting through the large-diameter grouting pipe, namely the support at one end is positioned at the lap joint of a newly-built wall and an old diaphragm wall, and the support at the other end is positioned in the unearthed soil body, so that the horizontal displacement of the diaphragm wall caused by excavation of a foundation pit can be effectively reduced, and meanwhile, the risk caused by precipitation of the foundation pit can be reduced by cutting off a target aquifer. In addition, by utilizing the old underground diaphragm wall, the construction cost is reduced, the influence on the existing adjacent underground engineering is greatly reduced, and the safe operation of the existing adjacent underground engineering is ensured.

All the components not specified in the present embodiment can be realized by the prior art.

The technical means disclosed in the invention scheme are not limited to the technical means disclosed in the above embodiments, but also include the technical scheme formed by any combination of the above technical features.

Claims

1. A wall structure construction method for increasing the depth of an old diaphragm wall is characterized by comprising the following steps:

(1) combining the conditions of the engineering hydrological geologic body and the actual construction scheme, adopting a finite element numerical simulation analysis calculation method, and taking the horizontal displacement deformation control standard of the foundation pit enclosure wall as a limiting condition, and determining the excavation depth range of the foundation pit which can cause the horizontal displacement deformation of the old diaphragm wall to be overlarge, so as to determine the lap joint position of the old diaphragm wall and the newly-built wall structure;

(3) embedding the prefabricated lap joint body, and pouring concrete into the lap joint body to form a guide wall;

(4) performing spiral drilling and pipe following drilling by using a drilling machine to finish embedding the steel pipe with the hole;

(5) and grouting the embedded steel pipe with the hole through the grouting pipe to complete the construction of the newly-built wall structure, and continuously performing subsequent foundation pit excavation.

2. The method for constructing a wall structure to increase the depth of an old diaphragm wall as claimed in claim 1, wherein the excavation depth range of the foundation pit, which may cause excessive horizontal displacement and deformation of the old diaphragm wall in the step (1), is as follows: the maximum excavation depth is the bottom position of the old diaphragm wall, and the minimum excavation depth is the corresponding excavation depth when the maximum horizontal displacement of the old diaphragm wall obtained through finite element calculation reaches the warning value of the displacement control standard of the foundation pit diaphragm wall.

3. The method for constructing a wall structure to increase the depth of an old diaphragm wall according to claim 1, wherein in the step (2), the drill guide pipes are steel pipes with a length of 2m and a wall thickness of 5mm, the section steel is welded with the formwork to form a lap joint base of the guide steel pipes, the interval between the guide pipes is 50cm, and a reinforcing mesh is welded outside the guide steel pipes to reinforce the fixation of the guide steel pipes, and the lap joint body is prefabricated in sections according to the excavation width of the foundation pit.

4. The method for constructing a wall structure by increasing the depth of an old diaphragm wall according to claim 1, wherein in the step (3), the old diaphragm wall is chiseled at a fixed point, so that the internal steel bars of the old wall are exposed for subsequent lapping, when the prefabricated lapping body is placed downwards, the external insertion angle of the guide steel pipe is 1-2 degrees through angle measurement, after the placement is finished, the template is welded and fixed through the connecting bars and the internal steel bars of the old wall, then C20 concrete is poured, the thickness of the guide wall is at least 80cm, and the drilling construction is carried out after the strength of the wall reaches 80%.

5. The wall structure construction method for increasing the depth of the old diaphragm wall according to claim 1, wherein in the step (4), the steel pipe with holes is a phi 219 seamless steel perforated pipe, the wall thickness is 8mm, grouting holes are arranged on the pipe wall according to a quincunx pattern, the hole diameter is 5mm, the hole spacing is 50cm, no grouting hole is arranged in the range of 2m at the tail part of the steel pipe, in the drilling process, the drilling angle is monitored and corrected in real time by combining an angle signal transmitted by a positioning sensor arranged in a guide drill bit, so that the steel pipe is drilled according to the design angle, when the steel pipe is drilled to the design depth, the positioning sensor is withdrawn, a steel reinforcement cage is arranged in the steel pipe, and grouting construction is carried out immediately.

6. The method for constructing a wall structure for increasing the depth of an old diaphragm wall according to claim 1, wherein in the step (5), the grouting pressure is controlled to be 0.6-1 MPa; the grouting slurry adopts cement-water glass double-liquid slurry, the cement adopts 425 common portland cement, the concentration of the water glass is 35 baume degrees, the modulus is 2.4-3.4, the water cement ratio of the cement slurry is 1: 1, the volume ratio of cement paste to water glass is 1: 0.5; the grouting amount of a single steel pipe is determined according to the following formula:

Q＝πr²×L+πR²×L×η×α×β