A method for back grouting of a diaphragm wall trench bottom

Abstract

This invention relates to the technical field of grouting construction methods, specifically a method for grouting the bottom of a diaphragm wall trench, comprising the following steps: S1: excavating a trench on the natural ground; S2: lowering a reinforcing cage into the trench; S3: fabricating grouting pipes, ensuring their length exceeds the height of the reinforcing cage. The grouting pipes are composed of several grouting pipe units spliced ​​together with joints, maintaining a sealed contact between the grouting pipe units and the joints. During installation, all joints are tightened, and the lowering process is stable. By establishing a clear correspondence between the number of grouting pipes and the trench length, uniform grouting reinforcement is ensured for the toe areas of walls of different sizes. Simultaneously, the use of grouting pipe joints with specific threaded structures and sealing processes, along with specified binding and fixing methods to the main reinforcing bars of the reinforcing cage, enhances the integrity and sealing of the grouting pipes in complex construction environments, effectively preventing pipe detachment, breakage, and grout leakage, thus guaranteeing the final usability of the grouting channel.

Description

Technical Field

[0001] This invention relates to the technical field of grouting construction methods, and in particular to a post-grouting construction method for the bottom of a diaphragm wall trench. Background Technology

[0002] Diaphragm walls, as core components for deep foundation pit support and underground structural load-bearing, are widely used in construction, municipal engineering, and other fields. In special scenarios such as areas covered by trestle bridges, the bottom of the diaphragm wall trench is prone to insufficient bearing capacity due to complex geological conditions, insufficient soil compaction, or voids in the concrete pouring process. This can lead to settlement and deformation of the diaphragm wall, affecting the stability and safety of the overall engineering structure.

[0003] While post-grouting is used in existing diaphragm wall trench bottom reinforcement technologies, it has the following drawbacks: The layout of grouting pipes lacks a unified standard and has poor adaptability to changes in trench length; Poor sealing of grouting pipe connections can easily lead to detachment, breakage, or grout leakage. The grouting parameters are vague, a standardized control system has not been formed, and the grouting termination condition is singular. It is difficult to take into account both the grouting volume and the structural deformation risk, and problems such as incomplete grouting or excessive diaphragm wall heave are likely to occur. In addition, the lack of targeted safeguards during construction, as well as insufficient control over grout quality and equipment inspection, further affect the grouting reinforcement effect. Therefore, a standardized, precise, safe, and reliable grouting construction method for the bottom of the diaphragm wall trench is needed. Summary of the Invention

[0004] The main objective of this invention is to provide a method for post-grouting construction of diaphragm wall trenches, in order to solve the problems raised in related technologies.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for post-grouting construction of a diaphragm wall trench bottom is provided, comprising the following steps: S1: Excavate trenches on natural ground; S2: Lower the steel cage into the trench; S3: Process and manufacture grouting pipes to make their length greater than the height of the reinforcing cage. The grouting pipe is composed of several grouting pipe units spliced ​​together by joints. There is a sealed contact between the grouting pipe units and the joints. When placing the grouting pipe, ensure that all joints are tightened and that the hoisting process is stable. S4: Place multiple grouting pipes vertically into the trench and tie them to the main reinforcement bars of the steel cage. Select the appropriate number of grouting pipes according to the length of the trench. S5: Pour concrete onto the steel cage, and the concrete solidifies to form a wall; S6: One day after the concrete for the wall is poured, the grouting pipe is split and unblocked. S7: Grouting is performed on the wall toe under the wall through the grouting pipe. Grouting is stopped after the grouting of the wall toe meets the design conditions. Before grouting, the grouting pump, pipeline and pressure gauge are thoroughly inspected. During the grouting process, the grouting volume, pressure and time data of each pipe are recorded in detail to achieve precise control.

[0006] Furthermore, in step S4, when the length of the trench is greater than 5.5m, three grouting pipes are installed; when the length of the trench is not greater than 5.5m, two grouting pipes are installed.

[0007] Furthermore, in step S4, the bottom of the grouting pipe is 20cm to 50cm lower than the bottom of the reinforcing cage.

[0008] Further, in step S7, cement grout is used to grout the wall toe, and the water-cement ratio of the cement grout is 0.5~0.6.

[0009] Furthermore, when preparing the cement slurry, the mixing time shall not be less than 3 minutes, and after mixing, lumps and impurities shall be removed with a sieve.

[0010] Furthermore, the grouting operation at the wall toe is carried out after the concrete strength of the wall reaches 70%, and at a distance of not less than 8 to 10 meters from the grouting operation point of the wall. The same amount of grouting is carried out sequentially on each grouting pipe of the same wall.

[0011] Furthermore, the design conditions in S7 are as follows: the grouting volume of a single grouting pipe reaches 2 tons; the grouting volume reaches 80% of the design value, and the grouting pressure continues for 3 minutes to exceed 2MPa; the vertical bulge of the wall caused by grouting reaches 10mm.

[0012] Furthermore, both ends of the joint are fixedly provided with convex rings, the outer surface of the convex rings is machined with external threads, and the inner walls of both ends of the grouting pipe unit are machined with internal threads. The convex rings and the grouting pipe unit are threadedly connected and sealed to each other.

[0013] Furthermore, the joint is a seamless steel pipe with a diameter of 25 mm and a wall thickness of 3.2 mm.

[0014] Furthermore, the length of the convex ring is half the length of the joint. When splicing the grouting pipe unit, after sealing the outer ring with raw rubber tape, it is screwed into the grouting pipe unit.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. By establishing a clear correspondence between the number of grouting pipes and the length of the trench section, it was ensured that the toe area of ​​walls of different sizes could be uniformly covered with grouting reinforcement, improving the adaptability of the grouting pipes as the trench length varied. Simultaneously, the use of grouting pipe joints with specific threaded structures and sealing processes, along with the specified binding and fixing methods to the main reinforcement bars of the steel cage, enhanced the integrity and sealing of the grouting pipes in complex construction environments, effectively preventing pipe detachment, breakage, and grout leakage, and ensuring the ultimate usability of the grouting channel.

[0016] 2. This invention pre-treats the grouting channel through a "water-splitting and plug-opening" step, ensuring smooth grouting. It clearly defines key grouting parameters and initiation conditions, and proposes a composite termination condition that includes multiple indicators such as grouting volume, grouting pressure, and wall bulging value. This allows the grouting process to respond in real-time to pressure changes and structural deformation while ensuring sufficient grouting volume, automatically avoiding the risk of excessive wall bulging due to excessive grouting pressure. Thus, a dynamic balance is achieved between "sufficient grouting" and "structural safety," ensuring stable reinforcement effects without damage to the main structure. Simultaneously, a comprehensive inspection of the grouting pump, pipelines, pressure gauges, and other equipment systems is conducted before grouting; during the grouting process, detailed data such as grouting volume, pressure, and time for each pipe are recorded to achieve precise control. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the state of the diaphragm wall before pouring. Figure 2 This is a sectional view of the diaphragm wall after casting according to the present invention; Figure 3 This is a schematic diagram of the connector structure of the present invention.

[0018] Figure label: 1. Natural ground level; 2. Wall toe; 3. Trench; 4. Reinforcing cage; 5. Grouting pipe; 51. Grouting pipe unit; 52. Joint; 53. Convex ring; 6. Completed wall. Detailed Implementation

[0019] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0020] This embodiment provides a method for post-grouting construction of a diaphragm wall trench. The diaphragm wall is designed to be 800mm thick, and the trench sections are 5m and 6m long. The method includes the following steps: First, on the natural ground level 1, a trench 3 is excavated according to the design drawings to form a diaphragm wall, such as... Figure 1 and 2 As shown.

[0021] After trench 3 is excavated, cleaned, and inspected, the pre-tied steel cage 4 is lowered into trench 3. The dimensions of the steel cage 4 are matched with those of trench 3 to provide it with the main bending and shear resistance.

[0022] The preparation and installation steps of the grouting system are as follows: Grouting pipes 5 are fabricated on the ground. The grouting pipe 5 consists of multiple grouting pipe units 51 joined to the required length using dedicated connectors 52. In this embodiment, the connector 52 is a seamless steel pipe, preferably with an outer diameter of 25mm and a wall thickness of 3.2mm. Protruding rings 53 are fixed at both ends of the connector 52. The outer surface of the protruding rings 53 is machined with external threads, while the inner walls of both ends of the grouting pipe units 51 are machined with matching internal threads. The length of the protruding rings 53 is designed to be half the total length of the connector 52. During splicing, first, tightly wrap raw rubber tape around the outer ring of the protruding rings 53's threads to provide a seal, ensuring the connector does not bend or twist. Then, screw the connector 52 into the ends of the two grouting pipe units 51. This structure ensures connection strength, and the raw rubber tape effectively prevents grout leakage from the thread gaps.

[0023] The total length of the grouting pipe 5 needs to be calculated to ensure that its bottom extends 20cm to 50cm beyond the bottom of the reinforcing cage 4, so that the subsequent grouting device can penetrate deep into the wall toe area. When the length of the trench 3 is greater than 5.5m, three grouting pipes 5 are installed; when the length of the trench 3 is not greater than 5.5m, two grouting pipes 5 are installed, improving the adaptability of the grouting pipes 5 to changes in trench length. In this embodiment, two grouting pipes 5 are installed for a trench section of 5m in length; and three grouting pipes 5 are installed for a trench section of 6m in length. The grouting pipes 5 are arranged along the vertical main reinforcement of the reinforcing cage 4 and are securely tied to them in sections with tie wire. In particular, at each joint 52, an additional tie wire is required to fix it to the adjacent main reinforcement of the reinforcing cage to prevent the joint 52 from loosening or rotating during hoisting and concrete pouring. This enhances the integrity and sealing of the grouting pipes 5 in complex construction environments, effectively preventing pipe detachment, breakage, and grout leakage, and ensuring the final usability of the grouting channel.

[0024] After the grouting pipe 5 is installed, the concrete pouring process is carried out. Concrete is poured into the trench 3 through the guide pipe, wrapping the reinforcing cage 4 and filling the trench space. After the concrete solidifies, a solid wall 6 is formed. The area below the bottom of the wall 6 is the space of the toe 2 that needs to be reinforced.

[0025] Approximately one day after the concrete pouring of wall 6 is completed (the exact time depends on the temperature and initial setting of the concrete, and must be adjusted to ensure that the quality of the concrete in adjacent sections is not affected), the "water-breaking and unblocking" process is performed. This step involves injecting high-pressure clean water into the grouting pipe 5 from the top using a high-pressure grouting device. The high-pressure water flow impacts and clears the grouting device at the bottom of the grouting pipe 5, which is blocked by concrete grout. In this embodiment, a one-way valve grouting device, specifically a ZKSY100-150 dual-liquid grouting machine, is used and inserted to the bottom of the wall.

[0026] Formal wall toe grouting can only begin when the concrete strength of the wall reaches more than 70% of its design strength. The grouting point should be selected at least 8 to 10 meters away from the concrete pouring point to minimize interference. Before grouting, a trial grouting should be conducted to optimize and determine parameters such as grouting pressure and flow rate.

[0027] Formal grouting uses cement grout, with a water-cement ratio strictly controlled between 0.5 and 0.6. When mixing the grout, the stirring time should be no less than 3 minutes to ensure uniformity. The mixed cement grout must be filtered through a sieve to remove any possible lumps and impurities. During grouting, equal amounts of grout are sequentially injected into each grouting pipe 5 of the same diaphragm wall.

[0028] The termination of the grouting process is controlled by a set of composite conditions. Grouting of the grouting pipe 5 will be stopped if any of the following conditions are met: the grouting volume of a single grouting pipe 5 reaches 2 tons; the grouting volume reaches 80% of the design value and the grouting pressure exceeds 2MPa for 3 minutes; or the vertical bulge of the wall 6 caused by grouting reaches 10mm through monitoring. This set of composite conditions for terminating the grouting process forms a standardized control system, which enables the grouting process to respond in real time to pressure changes and structural deformation while ensuring sufficient grouting volume. The condition of stopping grouting when the grouting volume of a single grouting pipe 5 reaches 2 tons ensures the grouting volume of wall toe 2; the condition of stopping grouting when the grouting volume reaches 80% of the design value and the grouting pressure exceeds 2MPa for 3 minutes ensures the compactness of the grouting in wall toe 2; the condition of stopping grouting when the vertical bulge of the wall 6 caused by grouting reaches 10mm avoids the risk of structural deformation and excessive wall bulge due to excessive grouting pressure. Thus, a dynamic balance is achieved between "sufficient grouting" and "structural safety", ensuring stable reinforcement effect and no damage to the main structure.

[0029] Under normal operating conditions, the termination grouting pressure should be controlled between 0.6 MPa and 0.8 MPa, and should not exceed 2 MPa. The grouting area mainly covers the area approximately 0.5 m below the bottom of the underground wall.

[0030] Before and during the entire construction process, the following safeguards must be strictly implemented: when placing the grouting pipe, ensure that all joints are tightened and that the placement process is stable; before grouting, conduct a comprehensive inspection of the grouting pump, pipelines, pressure gauges, and other equipment systems; when mixing the grout, strictly weigh it according to the mixing ratio; during the grouting process, record in detail the grouting volume, pressure, time, and other data for each pipe to achieve precise control.

[0031] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for post-grouting construction of a diaphragm wall trench, characterized in that, Includes the following steps: S1: Excavate trenches (3) on the natural ground (1) to form diaphragm wall trenches; S2: Hang the steel cage (4) into the trench (3); S3: Process and manufacture grouting pipe (5) so that its length is greater than the height of the steel cage (4). The grouting pipe (5) is made up of several grouting pipe units (51) spliced ​​together by joints (52). The grouting pipe units (51) and joints (52) are in sealed contact. When placing the grouting pipe (5), ensure that all joints (52) are tightened and the hoisting process is stable. S4: Place multiple grouting pipes (5) vertically into the trench (3) and tie them to the main reinforcement of the steel cage (4); select the appropriate number of grouting pipes (5) according to the length of the trench (3); S5: Pour concrete onto the steel cage (4), and the concrete solidifies to form a wall (6). S6: One day after the concrete pouring of the wall (6) is completed, the grouting pipe (5) is subjected to water splitting and plugging treatment. S7: Grouting is performed on the wall toe (2) under the wall (6) through the grouting pipe (5); grouting is stopped after the grouting of the wall toe (2) meets the design conditions. Before grouting, the grouting pump, pipeline and pressure gauge are fully inspected. During the grouting process, the grouting volume, pressure and time data of each pipe are recorded in detail to achieve precise control.

2. The method for post-grouting construction of the diaphragm wall trench bottom according to claim 1, characterized in that, In step S4, when the length of the trench (3) is greater than 5.5m, three grouting pipes (5) are installed; when the length of the trench (3) is not greater than 5.5m, two grouting pipes (5) are installed.

3. The method for post-grouting construction of the diaphragm wall trench bottom according to claim 1, characterized in that, In step S4, the bottom of the grouting pipe (5) is 20cm to 50cm lower than the bottom of the reinforcing cage (4).

4. The method for post-grouting construction of the diaphragm wall trench bottom according to claim 1, characterized in that, In step S7, cement grout is used to grout the wall toe (2), and the water-cement ratio of the cement grout is 0.5~0.

6.

5. The method for post-grouting construction of the diaphragm wall trench bottom according to claim 4, characterized in that, When preparing the cement slurry, the mixing time shall not be less than 3 minutes. After mixing, use a sieve to remove lumps and impurities.

6. The method for post-grouting construction of the diaphragm wall trench bottom according to claim 1, characterized in that, The grouting operation of the wall toe (2) is carried out after the concrete strength of the wall (6) reaches 70%, and at a distance of not less than 8~10m from the grouting operation point of the wall (6). The same amount of grouting is carried out sequentially on each grouting pipe (5) of the same wall.

7. The method for post-grouting construction of the diaphragm wall trench bottom according to claim 1, characterized in that, The design conditions in S7 are: the grouting volume of a single grouting pipe (5) reaches 2 tons; the grouting volume reaches 80% of the design value, and the grouting pressure lasts for 3 minutes and exceeds 2MPa; the vertical bulge of the wall (6) caused by grouting reaches 10mm.

8. The method for post-grouting construction of the diaphragm wall trench bottom according to claim 1, characterized in that, Both ends of the connector (52) are fixed with convex rings (53), the outer surface of the convex rings (53) is machined with external threads, and the inner walls of both ends of the grouting pipe unit (51) are machined with internal threads. The convex rings (53) and the grouting pipe unit (51) are threadedly connected and sealed to each other.

9. The method for post-grouting construction of the diaphragm wall trench bottom according to claim 8, characterized in that, The joint (52) is a seamless steel pipe with a diameter of 25 mm and a wall thickness of 3.2 mm.

10. The method for post-grouting construction of the diaphragm wall trench bottom according to claim 8, characterized in that, The length of the convex ring (53) is half the length of the joint (52). When splicing the grouting pipe unit (51), after sealing the outer ring of the convex ring (53) with raw rubber tape, it is screwed into the grouting pipe unit (51).

Images