Double-pipe grouting device and grouting method suitable for hard rock stratum

Abstract

The invention relates to the technical field of geotechnical engineering grouting reinforcement, in particular to a double-pipe grouting device and method suitable for a hard rock stratum. The double-pipe grouting device comprises two grouting single pipes which are arranged in parallel at a certain interval, each grouting single pipe is at least divided into an upper solid pipe section and a lower grouting section in the axial direction of the grouting single pipe, and a plurality of grout outlet holes are formed in the pipe wall of each grouting section. The wrapping type fixing piece is arranged in a transition area between the solid pipe sections and the grouting sections of the two grouting single pipes, the two grouting single pipes are bound and fixed into a whole in the transition area, and the boundary dimension of the wrapping type fixing piece is matched with the inner diameter of a preformed grouting hole; wherein the outer side of the grouting section is provided with a double-layer sealing layer which can be broken under the grouting pressure. The grouting diffusion radius in the hard rock stratum is effectively enlarged, the slurry return rate and the double-slurry pipe blocking rate are remarkably reduced, and therefore the engineering requirements of geological reinforcement, deep hole and targeted grouting are met.

Description

Technical Field

[0001] This invention relates to the field of grouting reinforcement technology in geotechnical engineering, and more specifically, to a dual-pipe grouting device and grouting method suitable for hard rock formations. Background Technology

[0002] In geotechnical engineering, grouting is a key method for reinforcing strata and improving their strength and stability. However, existing technologies have significant drawbacks when applied to hard rock strata (such as granite): Limitations of sleeve valve grouting technology: Sleeve valve grouting is primarily designed for soft soil strata, relying on the closure of rubber sleeve valves for segmented grouting. However, in hard rock strata, due to the dense rock and low porosity, the grout cannot diffuse effectively, resulting in a small actual reinforcement area. More importantly, the rubber components of the sleeve valve are extremely prone to wear and breakage under the friction of the hard borehole wall and the high-pressure grouting environment, leading to poor equipment durability, high failure rate, and seriously affecting the continuity of construction and the grouting effect.

[0003] Disadvantages of traditional steel pipe grouting process: Steel pipe grouting is often used to adapt to the strength of hard rock. However, the traditional single steel pipe grouting method has several prominent pain points: (1) Severe backflow and grouting: The annular gap between the single pipe and the grouting hole wall is difficult to seal effectively. Under grouting pressure, the grout is very easy to flow back upward along this gap, resulting in material waste and incomplete filling of the intended reinforcement area; (2) High risk of pipe blockage due to dual-liquid grout: When cement-water glass dual-liquid grout is used, the two grouts are very easy to come into contact prematurely and undergo gel reaction in the single pipe, resulting in pipe blockage, frequent pipe cleaning, and low construction efficiency; (3) Poor targeting: It is difficult to accurately control the release of grout at a specific depth and range, which cannot meet the precise reinforcement needs of specific weak structural surfaces or fracture zones in hard rock strata.

[0004] Therefore, there is an urgent need for a device and method that can adapt to the high strength characteristics of hard rock formations, effectively prevent grout return and avoid pipe blockage, and achieve efficient and targeted grouting. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a simple, efficient, and reliable dual-pipe grouting device and grouting method suitable for hard rock formations. It aims to effectively expand the grouting diffusion radius in hard rock formations, significantly reduce the grout return rate and the dual-liquid grout blockage rate, thereby meeting the engineering requirements of geological reinforcement, deep hole, and targeted grouting.

[0006] Therefore, the object of the present invention is to provide a dual-pipe grouting device suitable for hard rock formations, comprising: Two parallel grouting pipes are arranged at a certain distance from each other. Each grouting pipe is divided into an upper solid pipe section and a lower grouting section along its axial direction. The pipe wall of the grouting section is provided with multiple grout outlet holes. A wrap-around fastener is installed in the transition area between the solid pipe section and the grouting section of two grouting single pipes, binding and fixing the two grouting single pipes into a whole in the transition area, and the outer dimensions of the wrap-around fastener are adapted to the inner diameter of the pre-formed grouting hole. The outer side of the grouting section is provided with a double-layer sealing layer that can be broken under grouting pressure.

[0007] Furthermore, the wrap-around fastener is a cylindrical structure formed by winding a flexible sealing material, and its outer diameter is equal to the inner diameter of the grouting hole.

[0008] Furthermore, the sealing layer includes an inner sealing element covering the opening of each grout outlet and an outer sealing element wrapping around the entire periphery of the grouting section.

[0009] Furthermore, the flexible sealing material is a short-fiber needle-punched nonwoven geotextile; and / or, the inner sealing element is a block of electrical tape; the outer sealing element is PVC transparent tape; and / or, the grouting single pipe is a steel pipe with a galvanized outer surface.

[0010] Furthermore, the top of the solid pipe section of the grouting single pipe is provided with a grouting interface with a valve, and the bottom of the grouting section is welded with a sealing base plate.

[0011] Furthermore, the space above the wrap-around fixing member, which is enclosed by the outer walls of the two grouting single pipes and the wall of the grouting hole, is filled with solidified two-liquid grout, forming an orifice seal.

[0012] The present invention also discloses a grouting method using the above-mentioned dual-pipe grouting device, comprising the following steps: S1. Drill vertical grouting holes in the ground; S2. Grout outlet holes are opened in the grouting section, and a double-layer sealing structure is set on the outside of the grout outlet holes; S3. Install wrap-around fasteners in the transition pipe area between the solid pipe section and the grouting section to fix the spacing between the two grouting pipes; S4. Lower the dual-pipe grouting device into the grouting hole to position the grouting section of the grouting pipe to the target grouting stratum. S5. In the space above the wrap-around fastener and between the grouting single pipe and the grouting hole wall, inject fast-setting grout to form a hole seal; S6. Through the top of the solid pipe section of the two grouting pipes, two grouting pumps are used to simultaneously inject different grouting components into the two grouting single pipes. After the two grouting components are sprayed out through the grouting section of their respective grouting pipes, they mix and solidify in the rock strata outside the grouting hole. S7. Within 30 minutes after grouting is completed, remove the grouting joint and inject quick-hardening cement into the grouting pipe; after the injection is completed, seal the top of the grouting pipe. S8. Seven days after the grouting is completed, core samples are drilled in the reinforced area to determine the grouting quality.

[0013] Furthermore, in S3, the outer surface of the wrap-around fastener is coated with cement slurry.

[0014] Furthermore, in step S5, the fast-setting grout is a two-component grout composed of cement grout and water glass solution; The volume ratio of cement slurry to water glass solution is 1:(0.6-1.0), and its initial setting time is 3-5 minutes; and / or, the water-cement ratio of cement slurry is 1:(1.0-1.5); and / or, the concentration of water glass solution is 30-40Be′.

[0015] Furthermore, in S7, the sealing depth of rapid-hardening cement is 0.5m below ground level; and / or, rapid-hardening cement must meet the requirements of initial setting time ≤ 1 hour and compressive strength ≥ 30MPa.

[0016] The advantages and positive effects of this invention are: This invention provides a steel-pipe dual-pipe grouting device and method for hard rock formations. By separately transporting cement slurry and water glass through dual pipes, the blockage problem caused by pre-mixing of slurry in traditional single pipes is fundamentally avoided, and the blockage rate is greatly reduced. The optimized grouting pipe opening design and dual-pipe synchronous grouting process enable the diffusion radius of slurry in hard rock to reach 0.8–1.2m, achieving wider and more uniform formation reinforcement.

[0017] In addition, the dual sealing structure of the wrap-around fastener and the double-liquid grout sealing of the grouting hole actively builds a high-strength sealing body at the hole before grouting, controlling the grout return rate from more than 40% in the traditional process to less than 10%, which greatly reduces grout waste.

[0018] Furthermore, the array of grout outlet holes on the grouting section allows the grout to be uniformly ejected from multiple points around the pipe. Combined with the greater grouting flow and pressure brought by dual-pipe grouting, the penetration and diffusion radius of the grout in dense hard rock is significantly increased, achieving uniform and targeted reinforcement of strata at specific depths.

[0019] Furthermore, all components are made from commonly used engineering materials, making them easy to process and inexpensive. The double-layer rubber seal of the grouting section ensures both sealing during pipe laying and smooth opening during grouting, resulting in high reliability. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the grouting process of the dual-pipe grouting device according to an embodiment of the present invention.

[0021] Explanation of reference numerals in the attached figures: 1. Grouting pipe; 2. Grouting hole; 3. Grout outlet hole; 4. Wrap-type fastener; 5. Annular gap; 6. Reinforced area. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below; obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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.

[0023] Please see Figure 1 The present invention discloses a dual-pipe grouting device suitable for hard rock formations, comprising two parallel grouting pipes 1, each grouting pipe 1 being divided into an upper solid pipe section and a lower grouting section.

[0024] The top of the solid pipe section is connected to the ground grouting equipment, forming a complete and sealed pipeline for pumping grout from the ground to the target stratum. Its structural strength and sealing performance ensure that the high-pressure grout does not leak or clog during transportation. The solid pipe section, through its non-perforated structure, ensures that the grout is released only within the pre-designated grouting section. This enables precise depth control and targeted grouting, preventing grout from spreading in non-target strata and ensuring that the grouting effect is concentrated on the hard rock section requiring reinforcement.

[0025] The grouting section pipe wall is uniformly provided with an array of grout outlet holes 3 corresponding to the pre-grouting stratum. A double-layer sealing structure is provided on the outside of the grout outlet holes 3: the inner sealing structure only partially seals the opening of each grout outlet hole 3 to prevent impurities from entering the pipe; the outer sealing structure is provided on the entire grouting section to seal the entire grouting section before grouting and to rupture under grouting pressure to allow grout to spray out. This double-layer sealing structure can maintain good sealing performance during storage, transportation, and pipe laying, and can also be controlled to rupture under grouting pressure, ensuring smooth grout spraying.

[0026] The solid sections of the two grouting pipes 1 are parallel to each other and maintain a fixed distance. In the transition pipe area between the solid pipe section and the grouting section, a wrapping fastener 4 is provided on its outer side, so that the two grouting pipes 1 are bound and fixed as a whole; the wrapping fastener 4 is preferably a cylindrical structure formed by winding short fiber needle-punched nonwoven geotextile, and its diameter is adapted to the diameter of the geological grouting hole 2 to be inserted, so that the grouting pipe 1 can fit tightly in the grouting hole 2. The annular gap 5 above the wrapping fastener 4 is formed by the outer walls of the two grouting pipes 1, the hole wall of the grouting hole 2 and the top surface of the wrapping fastener 4, and the annular space is composed of pre-filled and solidified two-liquid grout.

[0027] In this invention, the wrap-around fastener 4 plays a crucial role: 1) Creating conditions for annular space sealing: Two galvanized steel pipes are placed parallel to each other with a gap in the transition area. After being wrapped with geotextile, they form a continuous annular space with the borehole wall. The pipes are wrapped and fixed at the transition point between the perforated pipe and the solid pipe, creating a structurally stable area that provides a target cavity for the injection of the sealing grout and prevents the grout from flowing into non-target areas. 2) Establishing the upper sealing reference surface: The wrap-around fastener 4 fits tightly against the inner wall of the grouting hole 2, which can be regarded as a physical barrier. In subsequent steps, a fast-setting dual-liquid grout is injected into the annular gap 5 above it. The wrap-around fastener 4 serves as the bottom support and boundary of the sealing grout, ensuring that the grout is stably filled and solidified in the preset orifice section, forming a reliable sealing plug at the orifice. 3) Key structural foundation for preventing grout return: During high-pressure grouting, the grout will escape upwards along the annular gap 5 between the steel pipe and the hole wall. The outer wall of the wrap-around fastener 4 fits against the inner wall of the grouting hole 2, which increases the resistance to grout escape and also clarifies the range and location of subsequent double-liquid grout sealing at the hole, making the sealing more accurate and effective.

[0028] 4) Maintaining the spacing and parallelism of the two pipes: When two grouting pipes 1 are lowered into the grouting hole 2, they may move closer together or twist due to gravity, hole wall friction, or hole curvature. A wrapping fastener 4 is installed at the junction of the grouting section and the solid pipe section to wrap and fix the two grouting pipes 1 into a whole, ensuring that the two pipes maintain a preset 20mm spacing and stable relative position at the entrance of the grouting area. This prevents the two pipes from colliding or misaligning during lowering, which is crucial for the uniform mixing of the two-component grout outside the hole.

[0029] In some specific embodiments, the grouting pipe 1 is a galvanized steel pipe with a sealing base plate welded to its bottom end. Further, the distance between the two galvanized steel pipes is 10-30mm, preferably 20mm. Further, the outer diameter of the galvanized steel pipe is 32mm, and the overall outer diameter of the wrapped fastener 4 after binding is 110mm.

[0030] The grouting method of the present invention includes the following steps: S1. Drill grouting hole 2 using a drilling rig; Furthermore, in S1, an XY-1 or XY-2 geological drilling rig with a rated torque of not less than 1200 N·m is selected and equipped with a diamond drill bit with a diameter of 110 mm. This combination is designed specifically for hard rock formations and can ensure that the grouting hole 2 has a round cross-section and smooth hole wall.

[0031] Furthermore, in S1, the depth of grouting hole 2 is strictly controlled to be consistent with the depth of the pre-reinforced stratum, with an allowable error of only ±5cm; at the same time, the verticality deviation of grouting hole 2 is required to be no more than 2%, and an inclinometer is used for real-time monitoring and correction during construction, thereby effectively avoiding problems such as subsequent steel pipe lowering jamming and geotextile wrapping section damage caused by hole inclination.

[0032] Furthermore, in step S1, immediately after the grouting hole 2 is completed, a high-pressure air with a pressure of not less than 0.6 MPa is used to blow and clean the inside of the hole, thoroughly removing residual rock powder and debris to ensure the hole wall is clean. This step provides the necessary conditions for the smooth lowering of the grouting pipe 1 and the reliable formation of the hole opening sealing structure (dual-liquid grout sealing).

[0033] S2. Pre-treatment of grouting pipe 1: Specifically, grout outlet 3 is opened in the grouting section, and a double-layer sealing structure is set on the outside of grout outlet 3. Furthermore, in S2, the grout outlet holes 3 are spaced 50cm apart along the axial direction and number 3 along the circumference, with an included angle of 120° between the holes and a hole diameter of 10mm. This hole arrangement is conducive to the uniform injection of grout from the pipe, improving its diffusion efficiency and coverage uniformity in hard rock.

[0034] Furthermore, in S2, the inner sealing structure only partially seals each of the three grout outlets. Specifically, it uses a block of electrical tape to partially seal each outlet, with a tape thickness of 0.15mm and a temperature resistance of not less than 80℃. The outer sealing structure uses a double-layer wrapping of transparent PVC tape to seal the entire grouting section before grouting and to rupture under grouting pressure to allow the grout to spray out. The tape thickness is 0.1mm, with a tensile strength ≥15MPa, and the overlap during wrapping is not less than 50%. This structural design effectively maintains the seal during transportation and pipe laying, and ensures smooth grout spraying when the grouting pressure reaches the set threshold.

[0035] Furthermore, in S2, a DN32 valved grouting interface is welded to the top of the grouting pipe 1 to form a standardized connection port. This design enables quick and reliable docking with the ground grouting pump or other auxiliary equipment, such as the drill pipe connector used for deployment, thereby improving construction efficiency and continuity.

[0036] S3. A wrap-around fixing component 4 is installed in the transition pipe area between the solid pipe section and the grouting section to fix the spacing between the double grouting pipes 1. Furthermore, in S3, the pre-treated grouting pipes 1 are arranged in parallel (with the center-to-center spacing controlled at 20mm ± 1mm) to ensure that the two-component grout is effectively mixed and diffused at a predetermined position outside the hole. Furthermore, in S3, in the transition pipe area of ​​about 50cm between the grouting section and the solid pipe section, 200g / m² short fiber needle-punched nonwoven geotextile is used to tightly wrap and fix the two pipes in one piece. The overall outer diameter of the wrapped fixing part 4 is 110mm, which matches the diameter of the grouting hole 2. This not only allows for smooth lowering but also creates a uniform annular gap 5 for subsequent hole sealing.

[0037] Furthermore, in S3, to further improve the reliability and durability of the seal, a thin layer of cement slurry with a water-cement ratio of 1:1 can be applied to the outer surface of the wrapped fastener 4. This treatment enhances the bonding strength between the geotextile and the subsequently injected dual-liquid sealing slurry, forming a more robust orifice seal and effectively preventing the slurry from flowing back up along the pipe-hole gap during high-pressure grouting.

[0038] S4. The grouting pipe 1 is lowered into the grouting hole 2; Furthermore, in S4, the top of the solid pipe section is connected using a geological drill rod and slowly lowered to the grouting hole 2, with the lowering speed controlled at approximately (0.5±0.1) m / min. This low-speed control aims to minimize the impact, jamming, and frictional damage to the geotextile wrapping section and sealing layer caused by free fall due to gravity or excessive speed.

[0039] Furthermore, in S4, during the lowering process, the lowering depth of the device is monitored in real time using tools such as measuring ropes to ensure that the grouting section accurately reaches and completely covers the predetermined grouting stratum, thus achieving precise positioning of targeted grouting.

[0040] Furthermore, in S4, after being lowered to the designed depth, the top of the grouting pipe 1 is immediately temporarily fixed at the opening of the grouting hole 2 to prevent it from floating or shifting.

[0041] S5. Two grouting holes are sealed with double-liquid grout. Furthermore, in S5, the sealing process is achieved through the following steps: 1) In the annular gap 5 between the outer side of the two grouting pipes 1 and the wall of the grouting hole 2, a sealing operation is carried out on the section about 30cm above the geotextile fixing section. This position makes full use of the lower wrapping fixing part 4 as the support reference, defining the effective range of the sealing section. 2) The grout used for sealing is a specially formulated two-component grout, which is prepared by mixing cement grout and water glass solution at a volume ratio of 1:(0.6-1.0), preferably 1:0.8. This ratio design ensures that the initial setting time of the mixed grout is strictly controlled within 3 to 5 minutes, enabling it to quickly solidify and form a dense, impermeable annular seal. Furthermore, the cement slurry uses P.O42.5 cement with a water-cement ratio of 1:1.2; the water glass solution concentration is 35Be′ and the modulus is 2.8. The core function of the rapidly formed seal is to physically seal the channel between the inner wall of the grouting pipe 1 and the grouting hole 2, thereby effectively preventing the mixture of cement grout and water glass or a single component from returning along the gap during the subsequent high-pressure grouting stage. This ensures that the grouting pressure is fully used to drive the grout to diffuse into the surrounding rock fissures, greatly improving grouting efficiency and material utilization.

[0042] S6, Dual-pipe synchronous grouting; Furthermore, in S6, the grouting process is achieved through the following steps: two SYB-60 / 50 type grouting pumps with a rated pressure of not less than 5MPa are used, which are connected to two grouting pipes 1 respectively, and cement slurry and water glass are injected into the pipes simultaneously; during the grouting process, the injection flow rate of the two pumps is monitored and adjusted in real time to ensure that the flow rate difference does not exceed 10%, so as to ensure that the two slurries can achieve uniform and sufficient mixing reaction in the predetermined area outside the pipe hole; Grouting pressure is set in stages according to the differences in strata lithology: 1.5–2 MPa for moderately weathered granite and 2–3 MPa for slightly weathered granite. The total grouting volume is theoretically calculated based on the strata conditions using the formula Q=πR²Hnβ, where R is the design diffusion radius, H is the grouting section height, n is the stratum porosity, and β is the filling coefficient, ranging from 1.2 to 1.5, to ensure that the grout injection volume meets the reinforcement requirements.

[0043] Intelligent grouting process control is implemented during construction: if the grouting flow rate is detected to be below 5L / min for 5 consecutive minutes, the system will automatically increase the grouting pressure by 0.2MPa; this process is repeated until the designed total grouting volume is reached or the grouting pressure stabilizes at the set value; this dynamic control mechanism can effectively cope with the differences in rock strata fissures, ensure that the grout overcomes resistance, fully fills the rock pores, and achieves saturated grouting.

[0044] S7, Grouting pipe 1 plugged Within 30 minutes after grouting is completed, remove the grouting joint and inject quick-setting cement into grouting pipe 1 to a sealing depth of 0.5m below ground level. The quick-setting cement must have an initial setting time of ≤1 hour and a compressive strength of ≥30MPa. After grouting, weld a 3mm thick steel plate to seal the top of grouting pipe 1 to form a permanent seal and prevent rainwater or debris from entering.

[0045] S8. Grouting effect detection Seven days after grouting is completed, core samples with a diameter of 100 mm are drilled in reinforced zone 6. There are no less than three test points in each reinforced zone 6. Reinforced zone 6 refers to the range of soil and rock mass formed by this grouting process, which is effectively filled and cemented by the grout. The core samples should be dense in appearance, without obvious cracks or voids. After laboratory pressure test, their compressive strength should not be less than 3 MPa, and the measured grout diffusion radius should reach 0.8–1.2 m before the grouting quality can be judged as qualified.

[0046] Through the above-mentioned standardized process, this invention achieves refined and controllable grouting construction in hard rock formations, significantly improving grouting efficiency, sealing reliability, and reinforcement uniformity.

[0047] The embodiments given above are preferred examples for implementing the present invention, and the present invention is not limited to the above embodiments. Any non-essential additions or substitutions made by those skilled in the art based on the technical features of the present invention are within the protection scope of the present invention.

Claims

1. A dual-pipe grouting device suitable for hard rock formations, characterized in that, include: Two parallel grouting pipes are arranged at a certain distance from each other. Each grouting pipe is divided into an upper solid pipe section and a lower grouting section along its axial direction. The pipe wall of the grouting section is provided with multiple grout outlet holes. A wrap-around fastener is installed in the transition area between the solid pipe section and the grouting section of two grouting single pipes, binding and fixing the two grouting single pipes into a whole in the transition area, and the outer dimensions of the wrap-around fastener are adapted to the inner diameter of the pre-formed grouting hole. The outer side of the grouting section is provided with a double-layer sealing layer that can be broken under grouting pressure.

2. The dual-pipe grouting device according to claim 1, characterized in that, The wrap-around fastener is a cylindrical structure formed by winding a flexible sealing material, and its outer diameter is equal to the inner diameter of the grouting hole.

3. The dual-pipe grouting device according to claim 2, characterized in that, The sealing layer includes an inner sealing element covering the opening of each grout outlet and an outer sealing element wrapping around the entire periphery of the grouting section.

4. The dual-pipe grouting device according to claim 3, characterized in that: The flexible sealing material is a short-fiber needle-punched nonwoven geotextile; and / or, the inner sealing element is a block-shaped electrical tape; the outer sealing element is PVC transparent tape; and / or, the grouting single pipe is a steel pipe with a galvanized outer surface.

5. The dual-pipe grouting device according to claim 1, characterized in that, The top of the solid pipe section of the grouting single pipe is equipped with a grouting interface with a valve, and the bottom of the grouting section is welded with a sealing base plate.

6. The dual-pipe grouting device according to claim 1, characterized in that, The space above the wrap-around fastener, enclosed by the outer walls of the two grouting single pipes and the grouting hole wall, is filled with solidified two-liquid grout, forming an orifice seal.

7. A grouting method using the dual-tube grouting device as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Drill vertical grouting holes in the ground; S2. Grout outlet holes are opened in the grouting section, and a double-layer sealing structure is set on the outside of the grout outlet holes; S3. Install wrap-around fasteners in the transition pipe area between the solid pipe section and the grouting section to fix the spacing between the two grouting pipes; S4. Lower the dual-pipe grouting device into the grouting hole to position the grouting section of the grouting pipe to the target grouting stratum. S5. In the space above the wrap-around fastener and between the grouting single pipe and the grouting hole wall, inject fast-setting grout to form a hole seal; S6. Through the top of the solid pipe section of the two grouting pipes, two grouting pumps are used to simultaneously inject different grouting components into the two grouting single pipes. After the two grouting components are sprayed out through the grouting section of their respective grouting pipes, they mix and solidify in the rock strata outside the grouting hole. S7. Within 30 minutes after grouting is completed, remove the grouting joint and inject quick-hardening cement into the grouting pipe; after the injection is completed, seal the top of the grouting pipe. S8. Seven days after the grouting is completed, core samples are drilled in the reinforced area to determine the grouting quality.

8. The method according to claim 7, characterized in that, In S3, the outer surface of the wrap-around fastener is coated with cement slurry.

9. The method according to claim 7, characterized in that, In step S5, the fast-setting grout is a two-component grout made by mixing cement grout and water glass solution; The volume ratio of cement slurry to water glass solution is 1:(0.6-1.0), and its initial setting time is 3-5 minutes; and / or, the water-cement ratio of cement slurry is 1:(1.0-1.5); and / or, the concentration of water glass solution is 30-40Be′.

10. The method according to claim 7, characterized in that, In S7, the sealing depth of rapid-hardening cement is 0.5m below ground level; and / or, rapid-hardening cement must meet the requirements of initial setting time ≤ 1 hour and compressive strength ≥ 30MPa.

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