Anchoring body grouting construction method capable of improving compactness and bearing capacity

Abstract

The invention provides an anchoring body grouting construction method capable of improving compactness and bearing capacity, relates to the technical field of underground infrastructure construction, and aims to overcome the defects that in-hole cleanliness is poor, a pipeline is prone to being blocked, and an anchoring body is insufficient in compactness and low in bearing capacity in a traditional normal-pressure grouting process. Comprising the steps that after hole site calibration drilling and hole cleaning are conducted, a prestress assembly with a primary grouting pipe and a secondary grouting pipe is put in; cement paste is injected through a primary grouting pipe, compressed air of 0.5-10 MPa is introduced, and normal-pressure grouting is completed; and before initial setting of the cement paste after primary grouting, grout is injected through a secondary grouting pipe at the pressure of 3-5 MPa, and a convex structure is formed. The grouting pipe is provided with a one-way anti-blocking structure, so that the insertion depth of the one-time grouting pipe is larger. The interface cleanliness is improved through gas-driven cleaning, splitting permeation is achieved through secondary high-pressure grouting, internal defects are eliminated, the contact area is increased through an outwards-protruding structure, the ultimate uplift bearing capacity of the anchor cable is improved, the anchor cable adapts to complex geology, construction continuity is guaranteed, efficiency is improved, and the anchor cable is suitable for high-grade anti-floating and supporting engineering.

Description

Technical Field

[0001] This invention relates to the technical field of underground infrastructure construction, and in particular to an anchor grouting construction method that can improve density and load-bearing capacity. Background Technology

[0002] In underground infrastructure construction, anchor grouting is the core process of anchoring engineering, and its construction quality directly affects the pull-out bearing capacity of anchor cables and the stability of the project. Currently, the industry widely uses the traditional single atmospheric pressure grouting process. The typical implementation of this process is as follows: after drilling, a regular grouting pipe is directly inserted, and cement grout is injected into the hole at an atmospheric pressure of ≤1MPa until the grout overflows from the hole opening, at which point the construction is considered complete.

[0003] However, existing technologies and related products have the following significant drawbacks: (1) Poor cleanliness inside the hole: During normal pressure grouting, the sediment generated by drilling is easily retained at the bottom of the hole, and the grout is easily attached to the hole wall. The grout cannot form an effective flush, resulting in impurities at the interface between the grout and the hole wall and the anchor cable, and the bonding force is significantly reduced. (2) High risk of pipeline blockage: Ordinary grouting pipes only have basic grouting function and no special anti-blocking design. After drilling, mud and sand in the hole are easily injected back into the grout outlet and the inside of the pipeline, causing grouting interruption and even local grout shortage in the anchor body. (3) Insufficient density of anchor body: Under normal pressure, the fluidity and diffusion capacity of grout are limited, making it difficult to fill the tiny voids in the hole and the cracks in the rock and soil. Defects such as honeycomb and voids are easily formed inside the anchor body, resulting in low overall density. (4) The bearing capacity cannot meet the high requirements: The anchor body formed by single grouting is uniformly cylindrical, with limited contact area with the surrounding rock and soil, and poor bonding force, resulting in low ultimate pull-out bearing capacity of the anchor cable, which cannot meet the needs of anti-buoyancy and support engineering under complex geological conditions.

[0004] Therefore, there is an urgent need for a grouting construction method that can solve the above-mentioned defects and improve the density and bearing capacity of the anchor body.

[0005] In view of this, the inventor has specifically designed an anchor grouting construction method that can improve the density and bearing capacity, and this invention is thus derived. Summary of the Invention

[0006] This invention addresses the shortcomings of existing traditional single atmospheric pressure grouting processes, and aims to solve the core problems of anchoring engineering, with the following objectives: Main objective: By innovating the grouting mode, significantly improve the bonding force and overall density between the anchor body and the surrounding soil and rock, achieve a doubling of the ultimate pull-out bearing capacity of the anchor cable, and meet the quality requirements of high-grade anti-buoyancy and support engineering. Secondary objective: To solve the problem of easy blockage in grouting pipelines, ensure the continuity and stability of construction, and reduce the incidence of construction failures and rework costs; The secondary objective is to optimize construction parameters and processes, enhance the adaptability of the technology to different geological conditions, simplify operational procedures, and improve construction efficiency.

[0007] To solve the above problems, the technical solution of the present invention is as follows: A method for grouting anchor bodies that can improve density and bearing capacity includes the following steps: S1. Mark the anchor hole position, drill the anchor cable drilling machine to the design depth, and clean the hole; S2. After the hole is cleaned, the prestressed assembly with primary grouting pipe and secondary grouting pipe is lowered into the anchor hole. S3. Inject cement grout into the anchor hole through the primary grouting pipe, and introduce compressed air into the anchor hole through the primary grouting pipe or independent air supply pipe to generate disturbance until the grout overflows steadily at the hole opening, and then stop the primary atmospheric pressure grouting. S4. After the first normal pressure grouting is completed, grout is injected into the anchor hole at a pressure of 3-5 MPa through the secondary grouting pipe, so that the grout can penetrate into the cracks of the surrounding rock and soil, forming an irregular outward convex structure to increase the contact area with the surrounding rock and soil. After 3-5 minutes, the secondary high pressure grouting is stopped.

[0008] Furthermore, the primary grouting pipe is provided with a plurality of primary grout outlet holes along its length extension direction; Alternatively, the independent gas filling pipe may have several gas filling holes along its length.

[0009] Furthermore, the opening of the primary grouting pipe extending into the anchor hole and the primary grout outlet are both equipped with a one-way anti-blocking structure; Alternatively, when using an independent gas filling pipe, both the opening extending into the anchor hole and the gas filling hole are equipped with a one-way anti-clogging structure.

[0010] Furthermore, the secondary grouting pipe is provided with a plurality of secondary grout outlet holes along its length extension direction, the opening of the secondary grouting pipe extending into the anchor hole is sealed, and the secondary grouting pipe is provided with a one-way anti-blocking structure.

[0011] Furthermore, in step S3, the pressure range of the compressed air is 0.5-10 MPa.

[0012] Furthermore, the prestressed component is one of a recyclable anchor cable, an anti-buoyancy anchor bolt, and an anti-buoyancy anchor cable.

[0013] Furthermore, the prestressed component is a recyclable anchor cable, and the timing of the secondary high-pressure grouting is before the initial setting of the cement slurry in the primary normal-pressure grouting; Alternatively, the prestressed component may be an anti-buoyancy anchor bolt or an anti-buoyancy anchor cable, and the timing of the secondary high-pressure grouting may be after the initial setting of the cement grout from the primary normal-pressure grouting.

[0014] Furthermore, the prestressed component is an anti-buoyancy anchor rod or an anti-buoyancy anchor cable, and the timing of the secondary high-pressure grouting is within 6-12 hours after the completion of the primary normal-pressure grouting.

[0015] Furthermore, the grout used in the secondary high-pressure grouting is a mixture of cementitious materials, sand, and admixtures. The cementitious materials are cement or a mixture of cement and active admixtures, and the admixtures are at least one of water-reducing agents, early-strength agents, and defoamers.

[0016] Furthermore, when compressed air is introduced through the primary grouting pipe, the compressed air is connected to the primary grouting pipe via a one-way valve.

[0017] The beneficial effects of this invention are as follows: This invention removes impurities from the hole through the air-driven cleaning function of primary atmospheric pressure grouting, and fills the surrounding tiny voids and rock and soil fissures through the splitting and penetration function of secondary high pressure grouting, thereby forming an irregular convex structure that increases the contact area with the surrounding rock and soil, eliminates honeycomb and void defects, and greatly improves the overall density of the anchor body.

[0018] Meanwhile, the convex structure increases the contact area between the anchor body and the soil and rock, and the improved interface cleanliness enhances the bonding force. The ultimate pull-out bearing capacity of the prestressed components can be further improved compared with the existing technology, thereby meeting the requirements of high-level projects.

[0019] In addition, the one-way anti-blocking structure of the grouting pipe prevents the backflow of mud and sand into the anchor hole, effectively reducing the pipeline blockage failure rate and minimizing construction interruptions and rework costs.

[0020] In particular, this invention, through segmented collaborative processes and adjustable air pressure and high pressure parameters, can be adapted to different geological conditions (such as sandy soil and rock-soil strata with well-developed fissures), simplifying the operation process and greatly improving construction efficiency. Attached Figure Description

[0021] The accompanying drawings, which are provided to further illustrate the invention and constitute a part of this invention, are illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention.

[0022] in: Figure 1 This is a schematic diagram of the overall process of the present invention; Figure 2 This is a schematic diagram of the cross-sectional structure of the molded anchor body of the present invention; Figure 3This is a schematic diagram of the cross-sectional structure of the anchor hole state changes during the implementation of the present invention; Figure 4 This is a block diagram illustrating the implementation principle of gas filling in this invention; Figure 5 This is one of the partial and three-dimensional structural schematic diagrams of the prestressed component in Embodiment 2 of the present invention; Figure 6 This is a second partial and three-dimensional structural schematic diagram of the prestressed component in Embodiment 2 of the present invention; Figure 7 This is a partial structural diagram highlighting the secondary slurry outlet in this invention; Figure 8 This is a partial structural diagram of the anchor cable fixing head in Embodiment 2 of the present invention; Figure 9 This is a cross-sectional view of the anchor cable fixing head in Embodiment 2 of the present invention; Figure 10 This is a cross-sectional view and exploded structural diagram of the anchor cable fixing head in Embodiment 2 of the present invention.

[0023] Label Explanation: 100. Anchor cable body; 110. Anchor cable protective tube; 200. Bearing body; 300. Anchor cable fixing head; 310. Spring; 320. Wedge; 400. Primary grouting pipe; 500. Secondary grouting pipe; 600. Secondary grout outlet hole; 700. One-way anti-blocking structure; 800. Rock and soil mass; 810. Anchor hole; 900. Preliminary anchor body; 910. Outward protrusion structure. Detailed Implementation

[0024] To make the technical problems, solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention. Example 1

[0025] Please see Figures 1 to 10 This is a preferred embodiment of the present invention, which is a method for constructing anchor grouting that can improve density and bearing capacity, comprising the following steps: Step 1: Hole Formation A spiral drilling rig was used to form a hole with a diameter of 150 mm and a depth of 8 m. After anchoring the anchor hole at position 810, the spiral drilling rig was drilled along the designed point and diameter to the designed depth, and then the hole was cleaned. Step 2: Lowering the prestressed components After the hole is cleaned, the prestressed assembly with primary grouting pipe 400 and secondary grouting pipe 500 is lowered into the anchor hole 810. The prestressed component is one of a recyclable anchor cable, an anti-buoyancy anchor bolt, or an anti-buoyancy anchor cable. In this embodiment, a recyclable anchor cable is used as an example.

[0026] Step 3: One-time atmospheric pressure grouting A primary grouting pipe 400 with a diameter of 30mm is used. Several primary grout outlet holes with a diameter of 6mm are opened sequentially along the axial direction above the bottom end of the pipe. At the same time, the bottom opening serves as the main grout outlet position. Electrical tape is wrapped around the primary grout outlet holes (covering the top and bottom of the hole position) and the grout outlet area of ​​the bottom opening twice to form a one-way anti-clogging structure 700. The one-way anti-clogging structure 700 can automatically open under pressure to prevent mud and sand from entering and clogging. Connect the tee fitting to the primary grouting pipe 400, and then connect the grouting equipment (grouting machine or other grouting equipment) to one of the ports. Connect the remaining port of the tee fitting to the air compressor via a check valve.

[0027] Cement grout is injected into anchor hole 810 through grouting pipe 400, while compressed air at 4MPa is introduced into the pipe to create disturbance until the grout overflows steadily from the opening of anchor hole 810, at which point the atmospheric pressure grouting is stopped. In addition, if a separate independent air-filling pipe is used, several air-filling holes (not shown in the figure) are opened in the length extension direction of the independent air-filling pipe to cooperate with the primary grout outlet of the primary grouting pipe for air-filling and mixing, to mix and disturb the injected cement slurry, to fully eliminate the floating slurry and impurities attached to the anchor hole, to avoid the formation of defects such as honeycomb and voids in the anchor hole, and to improve its density. No restrictions are imposed here.

[0028] Step 4: Secondary high-pressure grouting Using a special high-pressure grouting pipe with a diameter of 30mm and a pressure resistance of 15Mpa, several secondary grout outlet holes 600 with a diameter of 6mm are evenly opened from the bottom along the axial direction. The grout outlet area of ​​the secondary grout outlet hole 600 is wrapped with electrical tape twice (covering the top and bottom of the hole). At the same time, the bottom is sealed to maintain the grout outlet pressure of the primary grout outlet hole. In this embodiment, the prestressed component is a recyclable anchor cable. Therefore, before the initial setting of the cement grout in the first normal pressure grouting (i.e., within 1-2 hours after grouting is completed, which can be extended to 3 hours in southern environments), a second high-pressure grouting is initiated. A mixture of cement and sand is injected into the anchor hole 810 through the secondary grouting pipe 500 at a pressure of 3-5 MPa. This causes the grout to split and penetrate into the fissures of the surrounding rock and soil 800, forming an irregular outward convex structure to increase the contact area with the surrounding rock and soil. After 3-5 minutes, the second high-pressure grouting is stopped, thereby avoiding damage to the rod and ensuring the compactness of the grouting.

[0029] In addition, if the prestressed components use anti-buoyancy anchors or anti-buoyancy anchor cables, the timing of the secondary high-pressure grouting should be modified accordingly to be within 6-12 hours after the initial setting of the cement in the first normal pressure grouting, i.e. after the completion of the cement grouting in the first normal pressure grouting. This will enhance the friction between the anchor body and the soil and improve the pull-out resistance through split grouting.

[0030] In addition, the grout in the secondary high-pressure grouting is a mixture of cementitious materials, sand and admixtures. The cementitious materials are cement or a mixture of cement and active admixtures, and the admixtures are at least one of water-reducing agents, early-strength agents and defoamers.

[0031] In this embodiment, the slurry is specifically composed of: 45%-100% cementitious material, 0-55% sand, and 0.2-0.5% admixture. The admixture mainly includes water-reducing agent, early strength agent, and defoamer. The cementitious material can be cement or a mixture of cement and active admixture.

[0032] The grouting material is pre-mixed evenly, packaged in bags or ton bags, and used directly on-site by adding water according to the specified ratio. It features high strength, early strength, micro-expansion, good fluidity, and high filling degree.

[0033] Compared to commonly used ordinary grouting materials, special grouting materials develop strength faster, greatly shortening the time to reach the predetermined strength and reducing the construction period. They also have high strength, good fluidity, high filling degree, stronger interlocking with the soil, and greater friction, enabling the anchor cable system to provide greater anchoring force. Example 2

[0034] Please see Figure 1-10 This embodiment relates to a prestressed component for an anchor grouting construction method that can improve density and bearing capacity. The prestressed component is a recyclable anchor cable.

[0035] The recyclable anchor cable in this embodiment includes an anchor cable body 100, a bearing body 200, an anchor cable fixing head 300, an anchor cable protective tube 110, a primary grouting pipe 400, and a secondary grouting pipe 500, as detailed below: After passing through the bearing body 200, the anchor cable body 100 can be detachably fixed to the anchor cable fixing head 300. The anchor cable protective tube 110 is sleeved on the outside of the anchor cable body 100 to maintain the sealing of the anchor cable in the anchor hole 810. The ends of the primary grouting pipe 400 and the secondary grouting pipe 500 are both located on the bearing body 200.

[0036] Furthermore, the insertion depth of the primary grouting pipe 400 in the anchor hole 810 is greater than that of the secondary grouting pipe 500. In this embodiment, the primary grouting pipe 400 extends below the bottom of the support body 200 and does not exceed the depth of the anchor cable fixing head 300, while the secondary grouting pipe 500 is snapped and fixed on the support body 200, and its bottom does not exceed the position of the bottom plate of the support body 200.

[0037] Furthermore, the secondary grout outlet 600 of the secondary grouting pipe 500 is located within the area of ​​the bearing 200, that is, within 50 cm or 1 meter before and after the bearing, with a spacing of 50-70 mm. This compensates for the insufficient fullness that may exist in the primary grouting, enhances the contact area and bond strength between the anchor body and the soil, improves the pull-out resistance, and can form a corresponding irregular outward convex structure at the strongest position of its connection structure (i.e., the position of the bearing body). This structure is used to enhance the contact area with the surrounding rock and soil, thereby enhancing its ultimate pull-out resistance.

[0038] Specifically, the secondary grout outlet 600 of the secondary grouting pipe 500 is located 20±2cm above its bottom end, and multiple sets are provided along its axial direction. Each set of primary grout outlet 600 is evenly distributed along the axial direction of its pipe wall (one is arranged within a 90° rotation range).

[0039] In this embodiment, the anchor cable fixing head 300 is a fixing head structure specifically for recyclable anchor cables. Its internal structure and principle are existing technologies. Internally, a spring 310, in conjunction with a clamping plate 320, engages the steel strand to secure the anchor cable body 100. This allows the tension to be transmitted through the anchor cable fixing head 300 to the bearing body 200, and further to the anchor body formed around the bearing body 200. Furthermore, after overcoming the elasticity of the spring 310 and causing the clamping plate 320 to detach from the anchor cable body 100, the anchor cable fixing head 300 and the anchor cable protective tube 110 are completely sealed, enabling the entire anchor cable body 100 to be extracted for recycling of the steel strand. The recycling method for recyclable anchor cables is existing technology in this field and will not be elaborated upon here.

[0040] The beneficial effects of this invention are as follows: This invention removes impurities from the borehole through the air-driven cleaning function of primary atmospheric pressure grouting, and fills tiny voids and 800mm cracks in the rock and soil through the splitting and penetration function of secondary high pressure grouting, eliminating honeycomb and void defects and greatly improving the overall density of the anchor body.

[0041] Meanwhile, the convex structure 910 increases the contact area between the anchor body and the soil 800, and the improved interface cleanliness enhances the bonding force. The ultimate pull-out bearing capacity of the prestressed component can be further improved compared with the existing technology, meeting the requirements of high-level projects.

[0042] In addition, the anti-clogging structure 700 of the grouting pipe 400 prevents the backflow of mud and sand into the anchor hole 810, which greatly reduces the failure rate of pipeline blockage and reduces construction interruption and rework costs.

[0043] In particular, this invention, through segmented collaborative processes and adjustable air pressure and high pressure parameters, can be adapted to different geological conditions (such as sandy soil and rock-soil strata with 800-degree fissures), simplifying the operation process and greatly improving construction efficiency.

[0044] In addition, the conventional process requires an 8-10 meter anchorage section, while the improved process only requires 6-8 meters to achieve the same pull-out resistance, and the pull-out resistance is 20%-50% higher than that of the traditional process.

[0045] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A method for grouting anchor bodies that can improve density and bearing capacity, characterized in that, Includes the following steps: S1. Mark the anchor hole position, drill the anchor cable drilling machine to the design depth, and clean the hole; S2. After the hole is cleaned, the prestressed assembly with primary grouting pipe and secondary grouting pipe is lowered into the anchor hole. S3. Inject cement grout into the anchor hole through the primary grouting pipe, and introduce compressed air into the anchor hole through the primary grouting pipe or independent air supply pipe to generate disturbance until the grout overflows steadily at the hole opening, and then stop the primary atmospheric pressure grouting. S4. After the first normal pressure grouting is completed, grout is injected into the anchor hole at a pressure of 3-5 MPa through the secondary grouting pipe, so that the grout can penetrate into the cracks of the surrounding rock and soil, forming an irregular outward convex structure to increase the contact area with the surrounding rock and soil. After 3-5 minutes, the secondary high pressure grouting is stopped.

2. The anchor grouting construction method for improving density and bearing capacity according to claim 1, characterized in that, The primary grouting pipe is provided with a number of primary grout outlet holes along its length extension direction; Alternatively, the independent gas filling pipe may have several gas filling holes along its length.

3. The anchor grouting construction method for improving density and bearing capacity according to claim 2, characterized in that, The opening of the primary grouting pipe into the anchor hole and the primary grout outlet are both equipped with a one-way anti-blocking structure. Alternatively, when using an independent gas filling pipe, both the opening extending into the anchor hole and the gas filling hole are equipped with a one-way anti-clogging structure.

4. The anchor grouting construction method for improving density and bearing capacity according to claim 1, characterized in that, The secondary grouting pipe is provided with a number of secondary grout outlet holes along its length extension direction. The opening of the secondary grouting pipe extending into the anchor hole is sealed and the secondary grouting pipe is provided with a one-way anti-blocking structure.

5. The anchor grouting construction method for improving density and bearing capacity according to claim 1, characterized in that, In step S3, the pressure range of the compressed air is 0.5-10 MPa.

6. The anchor grouting construction method for improving density and bearing capacity according to claim 1, characterized in that, The prestressed component is one of the following: recyclable anchor cable, anti-buoyancy anchor bolt, and anti-buoyancy anchor cable.

7. The anchor grouting construction method for improving density and bearing capacity according to claim 6, characterized in that, The prestressed component is a recyclable anchor cable, and the timing of the secondary high-pressure grouting is before the initial setting of the cement slurry in the primary normal-pressure grouting. Alternatively, the prestressed component may be an anti-buoyancy anchor bolt or an anti-buoyancy anchor cable, and the timing of the secondary high-pressure grouting may be after the initial setting of the cement grout from the primary normal-pressure grouting.

8. The anchor grouting construction method for improving density and bearing capacity according to claim 7, characterized in that, The prestressed component is an anti-buoyancy anchor rod or an anti-buoyancy anchor cable, and the timing of the secondary high-pressure grouting is within 6-12 hours after the completion of the primary normal pressure grouting cement grouting.

9. The anchor grouting construction method for improving density and bearing capacity according to claim 1, characterized in that, The grout used in the secondary high-pressure grouting is a mixture of cementitious materials, sand, and admixtures. The cementitious materials are cement or a mixture of cement and active admixtures, and the admixtures are at least one of water-reducing agents, early-strength agents, and defoamers.

10. The anchor grouting construction method for improving density and bearing capacity according to claim 1, characterized in that, When compressed air is introduced through the primary grouting pipe, the compressed air is connected to the primary grouting pipe through a one-way valve.

Images