Deeply buried underground continuous wall joint part leakage active protection structure

Abstract

The active leakage protection structure of the joint part of the deep-buried underground continuous wall mainly comprises a grouting pipe pre-buried at the joint between adjacent underground continuous wall segments, the bottom end of the grouting pipe is blocked, and the upper end of the grouting pipe extends out of the top of the crown beam by a certain height above the upper end of the underground continuous wall segment; after the crown beam is constructed and reaches a certain strength, the cement slurry is injected through the upper end of the grouting pipe and penetrates to the joint of the underground continuous wall through the side wall of the grouting pipe. The active leakage protection structure of the joint part of the deep-buried underground continuous wall can effectively reduce the leakage risk of the joint part.

Description

Technical Field

[0001] This utility model relates to the field of underground engineering construction technology, and in particular to an active protection structure for leakage at the joint of a deep-buried diaphragm wall. It is applicable to deep-buried underground projects such as ultra-deep foundation pits, deep foundation pits of subway stations, and cross-river tunnels that use diaphragm walls as retaining structures. Background Technology

[0002] In the construction of deeply buried underground projects, diaphragm walls have become a commonly used form of retaining structure due to their advantages such as high rigidity, deep wall depth, and good waterproof performance. However, since diaphragm walls need to be constructed in sections, the joints between the sections become critical weak points for water leakage. Deeply buried underground projects are located in complex geological formations, often containing highly permeable strata and significantly affected by high water head pressure. Once water seepage occurs at the joints of the diaphragm wall, it will not only cause the water level outside the pit to drop, triggering soil consolidation and settlement, threatening the safety of surrounding buildings, roads, and underground pipelines; it will also cause soil loss outside the pit, further exacerbating environmental deformation and seriously affecting the construction safety and progress of the foundation pit project. Currently, common solutions to the problem of leakage at the joints of diaphragm walls include adding a water-stop curtain or installing a water-stop structure on the outside of the joint. However, these methods are difficult to completely eliminate leakage, significantly increase project costs, and involve complicated construction processes and extended construction periods, failing to meet the requirements of high efficiency, economy, and safety in engineering projects. Utility Model Content

[0003] The technical problem to be solved by this utility model is to provide an active protection structure for leakage at the joint of a deep-buried underground continuous wall. By setting an active protection structure in advance at the joint of the steel cage during the construction stage and carrying out targeted grouting reinforcement before the foundation pit is excavated, the risk of leakage at the joint is effectively reduced, ensuring safe construction of the project, reducing adverse impacts on the surrounding environment, reducing project costs, and improving construction efficiency.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows: The active protection structure for leakage at the joint of a deep-buried diaphragm wall includes a grouting pipe pre-embedded at the joint between adjacent diaphragm wall sections. The bottom end of the grouting pipe is sealed, and the upper end of the grouting pipe extends a certain height above the top of the capping beam at the upper end of the diaphragm wall section. After the capping beam is constructed and reaches a certain strength, cement grout is injected through the upper end of the grouting pipe and seeps into the joint of the diaphragm wall through the side wall of the grouting pipe. The grouting pipe is a spring-framed grouting pipe.

[0005] The lower end of the grouting pipe is lower than the lower end of the early-strength concrete cushion layer at the bottom of the main structure.

[0006] The upper end of the grouting pipe is equipped with a grouting nozzle, and the grouting pump injects high-pressure cement slurry through the grouting nozzle. When the grouting pump's grouting pressure exceeds the seepage pressure value of the grouting pipe, the cement grout inside the grouting pipe seeps out from the side wall of the grouting pipe.

[0007] The grouting pipes are installed at the outer edge of the reinforcing cage and arranged along its length before pouring.

[0008] The grouting pressure of the grouting pump meets the requirements of 0.2MPa - 0.5MPa.

[0009] Grouting nozzles are installed at the upper end of the grouting pipe.

[0010] This utility model provides an active protection structure for leakage at the joint of a deeply buried underground continuous wall, which has the following technical effects: 1) Proactive protection with significant results: Unlike traditional passive water-stopping measures, this utility model pre-installs spring grouting pipes during the construction phase and injects grout before the foundation pit excavation, achieving proactive protection against leakage at the joints of the diaphragm wall. By reinforcing vulnerable areas in advance, the probability of joint leakage during foundation pit excavation is significantly reduced, greatly improving the safety and reliability of the project.

[0011] 2) Reduced costs and increased efficiency: Unlike traditional methods, there is no need to install large-scale water-stop curtains, reducing the investment in construction equipment, materials, and manpower, effectively lowering project costs. At the same time, it simplifies construction processes, shortens the construction period, and improves the overall efficiency of the project.

[0012] 3) Strong adaptability and wide application: This protective structure and construction method are suitable for deep-buried underground continuous wall projects under various complex geological conditions. Whether it is sandy soil, cohesive soil or gravel strata, good protective effect can be achieved by reasonably adjusting the grouting parameters, which has wide applicability.

[0013] 4) Easy to inspect and maintain: The upper end of the spring grouting pipe extends above the top of the cap beam, facilitating subsequent inspection of the grouting effect. If leakage is still found at the joint, secondary grouting and other maintenance operations can be performed through the grouting pipe, which is convenient, quick, and ensures the waterproof performance of the diaphragm wall.

[0014] 5) Cement grouting should be carried out after the capping beam is constructed, rather than after the diaphragm wall has reached its strength. This is mainly because there is over-grouting at the top of the diaphragm wall, and the over-grouting part needs to be removed before the capping beam is constructed. Removal is often done mechanically, which causes disturbance. Therefore, on site, grouting should be completed in one go after the capping beam is constructed and before the foundation pit is excavated to ensure quality.

[0015] 6) By using spring-frame grouting pipes, the pipes have the characteristic of expanding the pipe wall gaps when under pressure and closing when not under pressure, thus preventing cement slurry from entering the pipes during the pouring of concrete for the ground wall.

[0016] 7) The lower end of the grouting pipe is lower than the subbase. This is mainly to ensure that the grouting pipe can completely cover the height range of the main structure above the subbase, so as to ensure that there is no leakage after grouting.

[0017] 8) By setting the grouting pressure to 0.2 MPa - 0.5 MPa, this pressure range can ensure that the grout is injected and seeps out from the side wall of the grouting pipe without damaging the structure of the grouting pipe. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a schematic diagram of the connection between the reinforcing cage and the grouting pipe in this utility model.

[0019] Figure 2 This is a partial top view of the present invention.

[0020] Figure 3 for Figure 2 A magnified view of a portion of the image.

[0021] Figure 4 This is a top view of the underground continuous wall section in this utility model.

[0022] Figure 5 This is a top view of the installation of this utility model.

[0023] Figure 6 This is a cross-sectional view of the installation of this utility model.

[0024] In the diagram: 1. Reinforcing cage; 2. Grouting pipe; 3. Diaphragm wall section; 4. Grouting nozzle; 5. Crown beam; 6. Early-strength concrete cushion layer; 7. Retaining wall; 8. Concrete support; 9. Main structure; 10. Steel pipe support; 11. Top beam; 12. Diaphragm wall joint. Detailed Implementation

[0025] like Figure 1-6 As shown, the active leakage protection structure at the joint of the deeply buried diaphragm wall includes a grouting pipe 2 pre-embedded at the joint (diaphragm wall joint 12) between adjacent diaphragm wall segments 3. The bottom end of the grouting pipe 2 is sealed, and the upper end of the grouting pipe 2 extends a certain height beyond the top of the capping beam 5 at the upper end of the diaphragm wall segment 3. A grouting nozzle 4 is installed at the upper end of the grouting pipe 2, and the grouting nozzle 4 is connected to the grouting equipment. Cement grout at a certain pressure is injected into the grouting pipe 2 through the grouting equipment.

[0026] The grouting pipe 2 is a disposable grouting pipe (spring skeleton grouting pipe) manufactured by Hebei Yunwo Rubber & Plastic Products Co., Ltd. During the construction of the reinforcing cage 1 of the diaphragm wall, a spring skeleton grouting pipe with an outer diameter of φ12mm and an inner diameter of φ8mm is placed along the depth direction inside the joint of the reinforcing cage as the grouting pipe. The lower end of this grouting pipe 2 extends to the bottom of the pit, ensuring comprehensive protection of the joint area from the pit bottom to the ground surface and extending into the pit bottom. (The pit bottom refers to the bottom of the foundation pit after excavation to the design elevation.) Figure 6 The foundation layer is the subbase, above which is the structure, and the bottom of the subbase is the bottom of the excavation pit. Grouting pipe 2 extends below the bottom of the subbase. This allows the grouting area to cover the entire excavation height. The upper end of grouting pipe 2 extends above the top of the capping beam 5 on the diaphragm wall and is equipped with grouting nozzles 4 for easy subsequent grouting operations. Under certain pressure, the pipe wall of grouting pipe 2 can expel grout, ensuring that the grout evenly seeps from the pipe wall during grouting and fills the cracks and gaps in the joints of the diaphragm wall.

[0027] A method for constructing a deep-buried diaphragm wall includes the following steps: (I) Selection and preparation of grouting pipes Based on the depth of the diaphragm wall, design requirements, and geological conditions. In this embodiment, the depth of the ground wall varies from 33 to 40 meters, which is approximately twice the depth of the foundation pit excavation. During the excavation process, for temporary support structures (such as foundation pit retaining walls), the leakage rate at a single point should be ≤0.1L / min, and concentrated leakage or water / sand inrush is not allowed; joints (such as joints between trench sections) are high-risk areas for leakage and must be strictly controlled to prevent through-leakage.

[0028] A spring-framed grouting pipe with an outer diameter of φ12mm and an inner diameter of φ8mm was selected as the grouting pipe. Its elasticity and compressive strength can meet the structural integrity requirements during the construction of the reinforcing cage and the pouring of concrete. A firmly secured and well-sealed grouting nozzle 4 is installed at the upper end of the grouting pipe 2, using a quick-connect fitting for easy connection with grouting equipment. The lower end of the grouting pipe 2 is sealed to prevent concrete from entering the grouting pipe 2 from the lower end during the pouring of the continuous wall concrete.

[0029] (II) Fabrication of reinforcing cage and installation of grouting pipe At the fabrication site of rebar cage 1, the rebar cage 1 is tied and welded strictly according to the design drawings. At the joint positions on the left and right sides of rebar cage 1, the grouting pipes 2 are tied to the main reinforcement bars using plastic cable ties according to the markings, with a tying point spacing of 2m / row, ensuring that the grouting pipes 2 are vertically fixed and avoiding bending or tilting. During the tying process, soft protective material is wrapped around the outside of the grouting pipes 2 to prevent damage from tool impacts during fabrication. For rebar cages fabricated and spliced ​​in sections, special sleeves or connectors are used to connect the grouting pipes at the section points to ensure a firm connection that does not affect the flow of grout, and the connection points are sealed to prevent grout leakage during concrete pouring. (III) Hoisting and lowering of the steel cage Select a crane of appropriate tonnage to lift the reinforcing cage 1. Before lifting, thoroughly inspect the crane's performance, hook, wire rope, and other equipment. Set the lifting points reasonably according to the weight, size, and center of gravity of the reinforcing cage to ensure balanced lifting and prevent deformation. When lowering the reinforcing cage 1, operate the crane slowly and steadily to avoid violent collisions with the trench wall. Assign a dedicated person to observe the lowering of the grouting pipe 2 at the trench opening. If any abnormalities such as displacement or damage are encountered, stop lowering immediately, adjust and repair before continuing. After the reinforcing cage 1 reaches the designed depth, precisely adjust and fix its position to ensure that the verticality and planar position meet the design requirements. Check the condition of the grouting pipe again to ensure it is undamaged and that its upper end protrudes above the top of the capping beam to the required height. (iv) Concrete pouring for diaphragm walls The diaphragm wall concrete pouring method is used. After the first diaphragm wall segment 3 is poured, and after it has initially set to a certain strength, and after the trench for the second diaphragm wall segment 3 is excavated, before lowering the reinforcing cage, the end (construction joint surface) of the first diaphragm wall segment 3 is brushed repeatedly to thoroughly remove mud, sludge, and laitance adhering to the concrete surface, ensuring good bonding between adjacent wall segments and forming an effective water-stop curtain. After completion, the reinforcing cage is hoisted into the trench for the second diaphragm wall segment 3, and pouring is repeated. After the second diaphragm wall segment 3 is poured and initially set to a certain strength, the trench for the third diaphragm wall is excavated, followed by brushing of the second diaphragm wall segment 3, hoisting of the reinforcing cage for the third diaphragm wall segment 3, and finally pouring of the third diaphragm wall segment 3. This process is repeated until all segments of the diaphragm wall are poured.

[0030] After the diaphragm wall is poured, a grouting pipe 2 is pre-embedded in the vertical direction at each joint of the diaphragm wall (near the diaphragm wall joint 12).

[0031] The specific pouring process for each section of the underground continuous wall is as follows: Before pouring, a sealing and compressive strength test is conducted on the duct to ensure that no grout leakage or deformation occurs during the pouring process. The duct diameter is generally 250mm, and the distance between the bottom of the duct and the bottom of the trench is controlled at approximately 1m. During the pouring process, a continuous supply of concrete is maintained, and the pouring speed is controlled to ensure that the concrete surface rises evenly. The concrete surface height is frequently measured, and the duct embedment depth is adjusted promptly based on the measurement results. The duct embedment depth is generally controlled between 2-4m to prevent quality problems such as broken piles or mud inclusions. The condition of the grouting pipe is closely monitored. If displacement or deformation occurs, corrective measures are taken promptly to ensure that the concrete pouring quality meets the design strength grade and impermeability requirements. (v) Construction of the cap beam After the diaphragm wall concrete reaches a certain strength, the capping beam 5 is constructed. Before construction, the top of the diaphragm wall is roughened to remove laitance and loose stones, exposing fresh concrete to enhance the bond between the capping beam 5 and the diaphragm wall. During the binding of the capping beam reinforcement, protective measures are taken, such as wrapping the upper end of the grouting pipe 2 with a wooden box or plastic sleeve to prevent the reinforcement from colliding and damaging the grouting pipe 2 and grouting nozzle 4. After the capping beam formwork is installed, the formwork dimensions, verticality, and flatness are checked to ensure they meet design requirements. Then, the capping beam concrete is poured and vibrated to ensure compaction, preventing quality defects such as honeycomb and pitting. After pouring, timely curing is carried out for no less than 7 days. (vi) Grouting construction Before excavation of the foundation pit, a dedicated grouting pump was used to grout grouting pipe 2. The pump pressure met the design requirement of 0.2-0.5 MPa to ensure that cement grout seeped from the side wall of grouting pipe 2. Before grouting, the grouting pump, grouting pipeline, and other equipment were thoroughly inspected and tested. The cement grout was prepared using ordinary Portland cement with a strength grade of not less than PO42.5, and the water-cement ratio was determined to be 1:1 based on the geological conditions and design requirements. The cement grout was stirred evenly for at least 30 seconds, and stirring was continued during the grouting process to prevent cement sedimentation. The grouting pump was quickly connected to the grouting nozzle 4 at the upper end of grouting pipe 2, ensuring a good seal. The grouting pump was started to inject cement grout, and the changes in grouting pressure and grouting volume were closely observed. When the grouting pressure reached the design value and the grouting volume no longer increased or increased slowly, the grouting of that pipe was completed, and grouting was stopped. Grouting was carried out sequentially on the grouting pipes corresponding to each joint of the ground wall to complete the active protection treatment for leakage at all joints. After grouting is completed, the grouting nozzle is sealed to prevent debris from entering.

[0032] Grouting principle: The bottom of grouting pipe 2 is sealed to ensure that concrete cannot enter grouting pipe 2 during the initial pouring of the diaphragm wall. When performing anti-seepage treatment at the joint of the diaphragm wall, sufficient grouting pressure is used. This grouting pressure exceeds the seepage pressure value of grouting pipe 2, allowing the cement slurry inside grouting pipe 2 to seep out from the side wall of grouting pipe 2. The cement slurry further penetrates to the joint of the diaphragm wall, especially in some areas where the joint is not completely compacted and still has pores, thus achieving joint protection treatment.

Claims

1. An active leakage protection structure for joints of deeply buried underground diaphragm walls, characterized in that: This includes a grouting pipe (2) pre-embedded at the joint between adjacent underground continuous wall sections (3), the bottom end of the grouting pipe (2) is sealed, and the upper end of the grouting pipe (2) extends a certain height above the top of the capping beam (5) at the upper end of the underground continuous wall section (3); after the capping beam (5) is constructed and reaches a certain strength, cement grout is injected through the upper end of the grouting pipe (2) and seeps through the side wall of the grouting pipe (2) to the joint (12) of the underground continuous wall.

2. The active leakage protection structure for the joint of a deep-buried underground continuous wall according to claim 1, characterized in that: The grouting pipe (2) is a spring-framed grouting pipe.

3. The active leakage protection structure for the joint of a deeply buried underground continuous wall according to claim 2, characterized in that: The lower end of the grouting pipe (2) is lower than the lower end of the early-strength concrete cushion layer (6) at the bottom of the main structure (9).

4. The active leakage protection structure for the joint of a deep-buried diaphragm wall according to claim 3, characterized in that: The upper end of the grouting pipe (2) is equipped with a grouting nozzle (4), and the grouting pump injects high-pressure cement slurry through the grouting nozzle (4).

5. The active leakage protection structure for the joint of a deep-buried diaphragm wall according to claim 4, characterized in that: The grouting pressure of the grouting pump exceeds the seepage pressure of the grouting pipe (2), and the cement slurry in the grouting pipe (2) seeps out from the side wall of the grouting pipe (2).

6. The active leakage protection structure for the joint of a deep-buried diaphragm wall according to claim 5, characterized in that: The grouting pipe (2) is installed at the outer edge of the steel cage and arranged along the length direction before pouring.

7. The active leakage protection structure for the joint of a deep-buried diaphragm wall according to claim 6, characterized in that: The grouting pressure of the grouting pump meets the requirements of 0.2MPa - 0.5MPa.

8. The active leakage protection structure for the joint of a deep-buried underground continuous wall according to claim 7, characterized in that: Grouting nozzle (4) is installed at the upper end of grouting pipe (2).

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