Inclined precise grouting reinforcement method for pile bottom of plain pile of secant pile of foundation pit

Abstract

The invention relates to the technical field of building deep foundation pits, in particular to a foundation pit secant pile plain pile bottom inclined precise grouting reinforcement method which comprises the following steps that S1, reference lines are drawn on the positions, correspondingly perpendicular to all plain piles, of a foundation pit bottom working face; s2, marking five detection points at equal intervals at positions, which are 4m to 5m away from the pixel piles, on the reference line; and S3, a drill rod of the drilling machine is used for obliquely drilling along the first detection point close to the corresponding plain pile. According to the foundation pit secant pile plain pile bottom inclined precise grouting reinforcement method, through the mode of drawing the reference line, arranging five equally-spaced detection points at the interval of 4-5 m and inclined drilling sounding, one-by-one checking of the depth of all plain pile bottoms is achieved, the omission risk of traditional sampling detection is avoided, and it is ensured that no unqualified plain piles are neglected and no qualified plain piles are mistakenly reinforced. Sleeve valve pipe grouting is carried out along a drilling path formed through accurate detection only for a plain pile with insufficient depth or poor water stop.

Description

Technical Field

[0001] This invention relates to the field of deep foundation pit technology, and more specifically, to a method for precise grouting reinforcement of the bottom of interlocking plain piles in foundation pits. Background Technology

[0002] In deep foundation pit engineering, interlocking piles are often used as an integrated support and water-stop curtain system. They form a retaining structure by interlocking plain piles (ultra-slow-setting plain concrete piles) and reinforced concrete piles (reinforced concrete piles). The reinforced piles primarily bear the load, while the plain piles fill the gaps and provide water-stopping functionality. The plain piles are typically designed to be shorter than the reinforced piles. However, in actual construction, some plain piles fail to meet design requirements for length or achieve adequate water-stopping performance, easily leading to foundation pit seepage and affecting project safety.

[0003] Existing technologies address this problem by employing a comprehensive reinforcement scheme along the perimeter of the foundation pit. This involves installing multiple rows of sleeve valves on the inner side of the pit and applying a high-pressure jet grouting curtain on the outer side, with the reinforcement depth covering the pit bottom to the design depth. This type of scheme involves construction along the entire area under the worst-case scenario, resulting in drawbacks such as long construction periods, high costs, and poor economic efficiency. Furthermore, external reinforcement requires ample construction space, limiting its applicability. Summary of the Invention

[0004] The purpose of this invention is to provide a method for precise grouting reinforcement of the bottom of interlocking plain piles in foundation pits, in order to solve the problems mentioned in the background art, such as the construction length of some plain piles not meeting the design requirements or the water-stopping effect not meeting the standards, which easily leads to water seepage in the foundation pit and affects the safety of the project.

[0005] To achieve the above objectives, this invention provides a method for precise grouting reinforcement of the bottom of interlocking plain piles in foundation pits, comprising the following steps: S1. Mark reference lines at the bottom working surface of the foundation pit, perpendicular to the position of each solid pile; S2. Mark 5 detection points at equal intervals at a distance of 4m~5m from the plain stake on the reference line; S3. Use the drill rod of the drilling rig to drill obliquely along the first detection point close to the corresponding plain pile until the drill rod extends to the corresponding position on the outer wall of the plain pile; judge whether the driving depth of the plain pile is qualified by whether the end of the drill rod touches the plain pile. S4. For plain piles that are determined to require reinforcement, the sleeve valve pipe grouting process is used to reinforce the grouting points along the drilling path of the corresponding drill rod. The spacing between grouting holes is 300mm, and the length of the grouting section is not shorter than the diameter of the plain pile. S5. Repeat steps S1 to S4 to detect and reinforce all the piles in the foundation pit in turn until the reinforcement of all the piles is completed.

[0006] This setup achieves integrated operation of plain pile bottom depth detection and reinforcement through a complete process of "marking reference lines - setting up detection points - oblique drilling for judgment - sleeve valve grouting - pile-by-pile reinforcement". Compared with existing full-area reinforcement solutions, it only targets plain piles with insufficient depth, significantly reducing ineffective work and greatly improving construction efficiency; the oblique drilling method can accurately reach the corresponding position on the outer wall of the plain pile, providing a precise guiding path for grouting, ensuring that the reinforcement effect directly acts on the weak point of water stoppage, effectively solving the problem of foundation pit seepage caused by insufficient water stoppage of plain piles.

[0007] As a preferred embodiment of the present invention, in step S3, if the end of the drill rod of the first detection point touches the plain pile, the process is switched to the next detection point and the above-mentioned oblique drilling operation is repeated until the end of the drill rod of a certain detection point does not touch the plain pile at the corresponding position on the outer wall of the plain pile. It is then determined that the driving depth of the plain pile is insufficient and reinforcement is required. At this time, the position of the end of the drill rod that does not touch the plain pile is defined as the grouting point. If the ends of the drill rods of all 5 detection points touch the plain pile, it is then determined that the driving depth of the plain pile is qualified and no reinforcement is required.

[0008] This setup clearly defines the logic for determining the depth of drill pipe contact. Through standardized rules of "contact point change, no contact with grouting point, and full contact for qualification," it achieves accurate identification of the driving depth of plain piles. This completely avoids the limitation of traditional sampling inspections, which cannot cover all plain piles. It ensures a comprehensive inspection of all plain piles one by one, preventing the waste of resources caused by the wrong reinforcement of qualified plain piles and eliminating the safety risk of missing unqualified plain piles, further improving the accuracy and economy of the technical solution.

[0009] As a preferred embodiment of the present invention, in step S2, the five detection points are evenly distributed at equal intervals along the reference line.

[0010] This setup involves five detection points evenly distributed along the reference line at equal intervals. This ensures comprehensive coverage of the detection area corresponding to the solid pile without blind spots, preventing some areas from being missed due to uneven distribution of detection points. It provides comprehensive data support for subsequent depth determination, guarantees the reliability of the solid pile depth detection results, and lays the foundation for precise reinforcement.

[0011] As a preferred embodiment of the present invention, in step S3, the drilling direction of the drill rod is always towards the outer wall of the corresponding plain pile.

[0012] This setting ensures that the drilling direction of the drill rod is always towards the outer wall of the corresponding plain pile, which can accurately lock the target area for detection and grouting, avoid the drilling path from deviating from the plain pile, ensure that the drill rod can accurately extend to the corresponding position on the outer wall of the plain pile, improve the accuracy of detection results and the targeting of grouting operations, and avoid reinforcement failure due to path deviation.

[0013] As a preferred embodiment of the present invention, in step S3, the drill rod is kept at an angle throughout the drilling process until it extends to the design position on the outer wall of the plain pile.

[0014] This setting ensures that the drill rod remains at an angle throughout the drilling process, extending to the corresponding designed position on the outer wall of the plain pile. This guarantees the stability and accuracy of the drilling path, avoids deviations in the detection position due to changes in the drill rod's posture, and ensures accurate acquisition of the plain pile depth data. This provides a precise path guarantee for subsequent grouting reinforcement and ensures the effectiveness of the technical solution.

[0015] As a preferred embodiment of the present invention, in step S4, the grouting pressure and grouting material parameters of the sleeve valve pipe grouting process are determined according to the geological conditions of the foundation pit and the water-stopping requirements.

[0016] This setting allows for flexible determination of grouting pressure and grouting material parameters based on the geological conditions of the foundation pit and the requirements for water sealing. This enables the technical solution to be adapted to foundation pit scenarios with different soil layer distributions and soil permeability, as well as different levels of water sealing requirements. This enhances the versatility and applicability of the technology, ensuring that ideal reinforcement and water sealing effects can be achieved under various working conditions.

[0017] As a preferred embodiment of the present invention, in step S4, the length of the grouting section is not less than 1.2 times the diameter of the plain pile.

[0018] This setting requires the grouting section length to be no less than 1.2 times the diameter of the plain pile. Compared with the design of "no less than the diameter of the plain pile", this further expands the reinforcement coverage area, which can more fully cover the weak area at the bottom of the plain pile, ensure the bonding strength between the grouting reinforcement body and the plain pile, improve the stability and water-stopping sealing of the reinforced structure, and avoid the reinforcement effect not meeting expectations due to insufficient grouting section length.

[0019] As a preferred embodiment of the present invention, in step S5, the detection and reinforcement of all plain piles are carried out sequentially from one end of the foundation pit to the other.

[0020] This setup involves detecting and reinforcing all the plain piles in a sequence from one end of the foundation pit to the other, making the construction process orderly and controllable, reducing interference and safety hazards caused by cross-operations, facilitating construction organization and quality control, improving overall construction efficiency, ensuring that the reinforcement work is carried out in a standardized and efficient manner, and guaranteeing project progress and construction safety.

[0021] As a preferred embodiment of the present invention, it further includes a reinforcement structure for the method of inclined precision grouting reinforcement of the bottom of interlocking piles in foundation pits. The reinforcement structure includes plain piles, intermediate piles, inclined grouting holes, and sleeve valve pipes. The plain piles and intermediate piles are arranged in an interlocking manner to form a foundation pit retaining structure. The plain piles are located between two adjacent intermediate piles. The inclined grouting holes are opened on the side wall of the plain piles and extend obliquely into the interior of the plain piles. One end of the sleeve valve pipe is set in the inclined grouting hole, and the other end extends to the bottom of the foundation pit.

[0022] This design features an interlocking arrangement of plain and solid piles, forming a stable foundation for the excavation and providing a reliable structural support for grouting reinforcement. Inclined grouting holes are located on the sidewalls of the plain piles and extend obliquely inwards, allowing for precise targeting of weak areas at the pile bottom. Sleeve valves enable directional delivery and controllable diffusion of the grouting material, ensuring a tight bond between the grouting material and the plain pile, significantly improving water-stopping performance and structural stability. The structural design and reinforcement method are highly compatible, guaranteeing the feasibility of the technical solution.

[0023] As a preferred embodiment of the present invention, the spacing between adjacent inclined grouting holes is 300mm, the angle between the inclined grouting hole and the working surface at the bottom of the foundation pit is 30°-60°, and the diameter of the inclined grouting hole is 80mm-120mm.

[0024] This design, with a 300mm spacing between adjacent inclined grouting holes, ensures uniform and seamless grouting coverage. The 30°-60° included angle and 80mm-120mm hole diameter design adapt to different pile sizes and geological conditions, ensuring that the grouting material fully diffuses and covers the weak areas of the pile. This avoids uneven reinforcement or grouting failure due to improper parameters, ensuring stable and reliable reinforcement results.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. In the method of precise grouting reinforcement of the bottom of interlocking piles in the foundation pit, the bottom depth of all piles is checked one by one by "marking reference lines + setting up 5 equally spaced detection points at 4m~5m intervals + oblique drilling and probing". This avoids the risk of omission in traditional sampling and testing, and ensures that no unqualified piles are ignored and no unqualified piles are mistakenly reinforced.

[0026] 2. In this method of precise grouting reinforcement of the bottom of interlocking piles in foundation pits, only plain piles with insufficient depth or poor water stop are targeted. Sleeve valve grouting is carried out along the drilling path formed by precise detection. The spacing between grouting holes is 300mm and the length of the grouting section is adapted to the pile diameter, which greatly reduces the amount of ineffective reinforcement work. Compared with the existing full-area reinforcement scheme, it significantly shortens the construction period and reduces the investment cost, with outstanding economic advantages.

[0027] 3. In this method of precise grouting reinforcement of the bottom of interlocking plain piles in foundation pits, the reinforcement work is carried out on the working surface at the bottom of the foundation pit, without the need to occupy additional construction space outside the pit. This solves the problem of high site requirements for existing external reinforcement and is suitable for complex site conditions. Moreover, the operation process is clear and simple, and the work efficiency is high.

[0028] 4. In the method of precise grouting reinforcement of the bottom of the interlocking pile in the foundation pit, the sleeve valve pipe grouting process can make the grouting material accurately diffuse and closely fit with the pile, effectively make up for the insufficient length of the pile or the water-stopping defect, strengthen the seepage prevention performance of the foundation pit retaining structure, completely solve the problem of water seepage in the foundation pit, and ensure construction safety. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a top view of the structure of the present invention; Figure 3 This is a schematic diagram illustrating the construction and use of this invention; Figure 4 For the present invention Figure 3 A magnified view of a portion of the image; The meanings of the labels in the diagram are as follows: 1. Plain pile; 2. Mixed pile; 3. Inclined grouting hole; 4. Sleeve valve pipe. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] This invention provides a method for precise grouting reinforcement of the bottom of interlocking plain piles in foundation pits, such as... Figures 1-4 As shown, it includes the following steps: S1. Mark reference lines at the bottom working surface of the foundation pit, perpendicular to the position of each solid pile; S2. Mark 5 detection points at equal intervals at a distance of 4m~5m from the plain stake on the reference line; S3. Use the drill rod of the drilling rig to drill obliquely along the first detection point close to the corresponding plain pile until the drill rod extends to the corresponding position on the outer wall of the plain pile; judge whether the driving depth of the plain pile is qualified by whether the end of the drill rod touches the plain pile. S4. For plain piles that are determined to require reinforcement, the sleeve valve pipe grouting process is used to reinforce the grouting points along the drilling path of the corresponding drill rod. The spacing between grouting holes is 300mm, and the length of the grouting section is not shorter than the diameter of the plain pile. S5. Repeat steps S1 to S4 to detect and reinforce all the piles in the foundation pit in turn until the reinforcement of all the piles is completed.

[0032] By establishing reference lines, setting up five detection points, performing oblique drilling for assessment, precise grouting with sleeve valves, and reinforcing each pile individually, an integrated operation of pile bottom depth detection and reinforcement is achieved. Compared to existing full-area reinforcement solutions, this method targets only piles with insufficient depth, significantly reducing ineffective work and improving construction efficiency. The oblique drilling method can accurately reach the corresponding position on the outer wall of the pile, providing a precise path for subsequent grouting, ensuring targeted reinforcement, and effectively solving the problem of foundation pit seepage caused by insufficient water sealing of piles.

[0033] Specifically, in step S3, if the end of the drill rod of the first detection point touches the plain pile, the process switches to the next detection point and repeats the above-mentioned oblique drilling operation until the end of the drill rod of a certain detection point does not touch the plain pile at the corresponding position on the outer wall of the plain pile. It is determined that the driving depth of the plain pile is insufficient and needs to be reinforced. At this time, the position of the end of the drill rod that does not touch the plain pile is defined as the grouting point. If the ends of the drill rods of all 5 detection points touch the plain pile, it is determined that the driving depth of the plain pile is qualified and no reinforcement is required.

[0034] A clear logic for determining drill rod contact was established. By using the rule of "contact point change, no contact with grouting point, full contact for acceptance," the system accurately identifies whether the driving depth of the plain pile meets the standard. This avoids the risk of omissions in sampling inspections, enabling a comprehensive, one-by-one check of all plain piles. This ensures that no unqualified piles are mistakenly reinforced and no unqualified piles are missed, guaranteeing reinforcement quality while avoiding resource waste and further improving the accuracy and economy of the technical solution.

[0035] Furthermore, in step S2, the five detection points are evenly distributed at equal intervals along the reference line. In step S3, the drilling direction of the drill rod is always towards the outer wall of the corresponding plain pile. In step S3, the drill rod maintains an oblique posture throughout the drilling process until it extends to the corresponding designed position on the outer wall of the plain pile. In step S4, the grouting pressure and grouting material parameters of the sleeve valve grouting process are determined according to the geological conditions of the foundation pit and the water-stopping requirements. In step S4, the length of the grouting section is not less than 1.2 times the diameter of the plain pile. In step S5, the detection and reinforcement operations of all plain piles are carried out sequentially from one end of the foundation pit to the other.

[0036] Five detection points are evenly distributed to ensure comprehensive detection coverage of the corresponding area of ​​the plain pile and avoid detection blind spots; the drill rod is always pointed towards the outer wall of the plain pile and maintains an oblique posture to ensure that the drilling path accurately points to the target position, improving the accuracy of detection and grouting; grouting parameters are determined as needed to adapt to different geological conditions and water-stopping requirements, enhancing the applicability of the technology; the length of the grouting section is not less than 1.2 times the diameter of the plain pile to ensure reinforcement strength and water-stopping effect; piles are operated sequentially to make the construction process orderly and controllable, reduce cross interference, and improve construction efficiency and safety.

[0037] Furthermore, the system also includes a reinforcement structure for the method of precise grouting at the bottom of interlocking plain piles in foundation pits. The reinforcement structure includes plain piles 1, intermediate piles 2, inclined grouting holes 3, and sleeve valve pipes 4. Plain piles 1 and intermediate piles 2 are interlocked at intervals to form the foundation pit retaining structure, with the plain piles 1 located between two adjacent intermediate piles 2. The inclined grouting holes 3 are opened on the sidewall of the plain piles 1 and extend obliquely into the interior of the plain piles 1. One end of the sleeve valve pipe 4 is located inside the inclined grouting hole 3, and the other end extends to the bottom of the foundation pit. The spacing between adjacent inclined grouting holes 3 is 300mm, the angle between the inclined grouting hole 3 and the working surface at the bottom of the foundation pit is 30°-60°, and the diameter of the inclined grouting hole 3 is 80mm-120mm.

[0038] Plain piles 1 and interlocking piles 2 form a stable foundation for the foundation pit, providing a reliable structural support for grouting reinforcement. Inclined grouting holes 3 are opened on the side wall of plain piles 1 and extend obliquely into the interior. With a design of 300mm spacing, 30°-60° included angle, and 80mm-120mm hole diameter, the grouting range accurately covers the weak area at the bottom of plain piles 1. One end of the sleeve valve pipe 4 is placed in the inclined grouting hole 3 and the other end extends to the bottom of the foundation pit, realizing the precise delivery and controllable diffusion of grouting material. This allows the grouting reinforced body to be tightly bonded to plain piles 1, significantly improving the water-stopping and reinforcement effects. The structural design adapts to the method requirements, ensuring the feasibility of the technical solution.

[0039] In this invention, the construction process of inclined precision grouting reinforcement of the bottom of the interlocking plain pile in the foundation pit is as follows: I. Construction Preparation Stage Site clearing: Clear debris and loose soil from the working face at the bottom of the foundation pit, level the construction area, and ensure that the drilling rig working face is firm and flat, without any obstacles that may affect construction; at the same time, check the appearance of the foundation pit retaining structure (plain piles and solid piles), and record the distribution location and design parameters (pile diameter, design pile length, etc.) of the plain piles.

[0040] Equipment and material preparation: Equip drilling rigs, drill rods, sleeve valve pipes (suitable for 80mm-120mm hole diameters), grouting pumps, and other equipment, and verify the performance of the equipment to ensure normal operation; prepare grouting materials (cement grout or cement-water glass double-liquid grout, etc.), and determine grouting pressure, material ratio, and other parameters according to the geological conditions of the foundation pit and the water-stopping requirements.

[0041] Preparation for surveying and setting out: Prepare surveying tools such as total station and measuring tape, check the plain stake location drawings, and ensure the accurate positioning of subsequent reference lines and detection points.

[0042] II. Detection and Positioning Phase Draw reference lines (corresponding to step S1): Based on the pile distribution drawings, use a total station to accurately draw straight reference lines at the positions perpendicular to each pile on the working surface at the bottom of the foundation pit. The reference lines must be perpendicular to the pile axis and serve as the benchmark for the layout of detection points.

[0043] Marking detection points (corresponding to step S2 and preferred scheme): Measure the area 4m to 5m away from the plain stake on the reference line, and mark 5 detection points at equal intervals using tools such as a measuring tape. The spacing between adjacent detection points should be evenly distributed to ensure that there are no blind spots in the detection coverage area corresponding to the plain stake.

[0044] III. Oblique Exploration Drilling Stage Drilling rig setup and drilling (corresponding to step S3 and preferred solution): Fix the drilling rig next to the detection point, adjust the drilling rig angle so that the drilling direction of the drill rod is always facing the outer wall of the corresponding plain pile, and maintain an oblique posture throughout the process. Start the drilling rig and drill obliquely along the first detection point closest to the plain pile until the drill rod extends to the corresponding design position on the outer wall of the plain pile.

[0045] Depth determination and grouting point determination (corresponding to the preferred scheme of step S3): During the drilling process, observe the feedback from the end of the drill rod. If it touches the solid pile, stop drilling immediately and move the drilling machine to the next detection point to repeat the above-mentioned inclined drilling operation. If the end of the drill rod does not touch the solid pile after drilling at a certain detection point, it is determined that the driving depth of the solid pile is insufficient. Record the position of the end of the drill rod as the grouting point and the corresponding drilling hole as the grouting hole. If the end of the drill rod of all 5 detection points touches the solid pile, it is determined that the depth of the solid pile is qualified and no reinforcement is required. After marking, move on to the next solid pile for detection.

[0046] IV. Precision Grouting Reinforcement Stage Sleeve valve pipe installation (preferred solution for the corresponding reinforcement structure): For the plain pile that needs to be reinforced, insert one end of the sleeve valve pipe into the grouting hole, ensuring that the end of the sleeve valve pipe is aligned with the grouting point, and extend the other end to the working surface at the bottom of the foundation pit to fix the sleeve valve pipe and prevent it from shifting during the grouting process.

[0047] Grouting construction (corresponding to step S4 and preferred scheme): Start the grouting pump and use the sleeve valve grouting process to grout along the drilling path. The spacing between grouting holes is strictly controlled at 300mm, and the length of the grouting section is not less than 1.2 times the diameter of the plain pile. During the grouting process, the pressure parameters are monitored in real time and dynamically adjusted according to the geological conditions to ensure that the grouting material is evenly diffused and closely adheres to the plain pile.

[0048] Grouting complete: After the grouting reaches the preset pressure and grouting volume, stop grouting, seal the sleeve valve port, and wait for the grouting material to solidify and form a solidified body.

[0049] V. Overall Promotion and Acceptance Phase Pile-by-pile construction (corresponding to the preferred scheme of step S5): Repeat the above-mentioned detection and positioning, inclined drilling, and grouting reinforcement steps in the order from one end of the foundation pit to the other, and process all plain piles in the foundation pit in sequence to avoid cross-operation interference and ensure orderly construction process.

[0050] Quality Inspection: After all the plain piles are reinforced, the strength of the grouting reinforcement and the water-stopping effect are checked through sampling inspection and seepage observation to ensure that there is no potential for seepage in the foundation pit and that the reinforcement quality meets the standards.

[0051] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for precise grouting reinforcement of the bottom of interlocking plain piles in foundation pits, characterized in that: Includes the following steps: S1. Mark reference lines at the bottom working surface of the foundation pit, perpendicular to the position of each solid pile; S2. Mark 5 detection points at equal intervals at a distance of 4m~5m from the plain stake on the reference line; S3. Use the drill rod of the drilling rig to drill obliquely along the first detection point close to the corresponding plain pile until the drill rod extends to the corresponding position on the outer wall of the plain pile; judge whether the driving depth of the plain pile is qualified by whether the end of the drill rod touches the plain pile. S4. For plain piles that are determined to require reinforcement, the sleeve valve pipe grouting process is used to reinforce the grouting points along the drilling path of the corresponding drill rod. The spacing between grouting holes is 300mm, and the length of the grouting section is not shorter than the diameter of the plain pile. S5. Repeat steps S1 to S4 to detect and reinforce all the piles in the foundation pit in turn until the reinforcement of all the piles is completed.

2. The method for precise grouting reinforcement of the bottom of interlocking plain piles in foundation pits according to claim 1, characterized in that: In step S3, if the end of the drill rod of the first detection point touches the plain pile, the process is switched to the next detection point and the above-mentioned oblique drilling operation is repeated until the end of the drill rod of a certain detection point does not touch the plain pile at the corresponding position on the outer wall of the plain pile. It is determined that the driving depth of the plain pile is insufficient and reinforcement is required. At this time, the position of the end of the drill rod that does not touch the plain pile is defined as the grouting point. If the ends of the drill rods of all 5 detection points touch the plain pile, it is determined that the driving depth of the plain pile is qualified and no reinforcement is required.

3. The method for precise grouting reinforcement of the bottom of interlocking plain piles in foundation pits according to claim 1, characterized in that: In step S2, the five detection points are evenly distributed at equal intervals along the reference line.

4. The method for precise grouting reinforcement of the bottom of interlocking plain piles in foundation pits according to claim 1, characterized in that: In step S3, the drilling direction of the drill rod is always towards the outer wall of the corresponding plain pile.

5. The method for precise grouting reinforcement of the bottom of interlocking plain piles in foundation pits according to claim 1, characterized in that: In step S3, the drill rod remains in an oblique position throughout the drilling process until it extends to the corresponding design position on the outer wall of the plain pile.

6. The method for precise grouting reinforcement of the bottom of interlocking plain piles in foundation pits according to claim 1, characterized in that: In step S4, the grouting pressure and grouting material parameters of the sleeve valve grouting process are determined based on the geological conditions of the foundation pit and the water-stopping requirements.

7. The method for precise grouting reinforcement of the bottom of interlocking plain piles in foundation pits according to claim 1, characterized in that: In step S4, the length of the grouting section shall not be less than 1.2 times the diameter of the plain pile.

8. The method for precise grouting reinforcement of the bottom of interlocking plain piles in foundation pits according to claim 1, characterized in that: In step S5, the detection and reinforcement of all plain piles are carried out sequentially from one end of the foundation pit to the other.

9. The method for precise grouting reinforcement of the bottom of interlocking plain piles in foundation pits according to claim 1, characterized in that: It also includes a reinforcement structure for the method of slanted precision grouting reinforcement of the bottom of the interlocking piles in the foundation pit. The reinforcement structure includes a plain pile (1), a mortise pile (2), an slanted grouting hole (3), and a sleeve valve pipe (4). The plain pile (1) and the mortise pile (2) are interlocked at intervals to form a foundation pit retaining structure. The plain pile (1) is located between two adjacent mortise piles (2). The slanted grouting hole (3) is opened on the side wall of the plain pile (1) and extends slantedly into the interior of the plain pile (1). One end of the sleeve valve pipe (4) is set in the slanted grouting hole (3), and the other end extends to the bottom of the foundation pit.

10. The method for precise grouting reinforcement of the bottom of interlocking plain piles in foundation pits according to claim 9, characterized in that: The spacing between adjacent inclined grouting holes (3) is 300mm, the angle between the inclined grouting hole (3) and the working surface at the bottom of the foundation pit is 30°-60°, and the diameter of the inclined grouting hole (3) is 80mm-120mm.

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