Prestressed anchor cable rapid installation and grouting method suitable for strongly weathered and fragmented rock mass

Abstract

The application discloses a prestressed anchor cable rapid installation and grouting method suitable for strong weathered and fragmented rock mass, and belongs to the technical field of anchoring construction of geotechnical engineering. In view of the problem that the anchoring quality is poor due to the hole collapse during drilling and grouting leakage in the strong weathered and fragmented rock mass, the method comprises the following steps: drilling by using an eccentric following pipe drilling tool combination, and taking the casing as a temporary wall after drilling to the designed hole depth; passing the prestressed anchor cable through the casing, and filling the pressure into the grouting pipe to make the grouting plug form a closed grouting interval, and pressure grouting is carried out in the interval, and when the pressure reaches the set value and the flow rate drops to below the preset threshold value, the grouting is stopped and the pressure is maintained for a predetermined time; after the hole returns to the grouting, the casing is withdrawn upward by a predetermined length, and the grouting is repeated. The prestressed anchor cable rapid installation and high-quality grouting in the strong weathered and fragmented rock mass are realized by combining the following pipe wall protection, sectional pressure grouting and synchronous pipe withdrawal, and the prestressed anchor cable rapid installation and high-quality grouting can be widely applied to the high slope prestressed anchor cable construction in the fields of water conservancy and hydropower, traffic, mine and the like.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering anchoring construction technology. More specifically, this invention relates to a method for rapid installation and grouting of prestressed anchor cables suitable for strongly weathered and fractured rock masses. Background Technology

[0002] In the field of prestressed anchor cable construction, especially for anchoring projects in strongly weathered and fractured rock masses, conventional construction methods typically include drilling, hole cleaning, anchor cable installation, full-hole grouting, and tensioning and locking. These methods can meet engineering requirements when applied to intact or relatively intact rock masses.

[0003] However, the following problems and drawbacks exist when constructing prestressed anchor cables in highly weathered and fractured rock masses. First, highly weathered rock masses have well-developed joints and fissures, resulting in poor self-stabilization. After drilling, the borehole wall is prone to collapse and rockfall, leading to changes in borehole diameter or blockage, making it difficult to install the anchor cable to the designed depth, and sometimes requiring secondary drilling or re-drilling. Second, due to the developed fissures, grout easily flows away along the fissures during grouting, making it impossible to establish effective grouting pressure within the borehole. This results in incomplete grouting, insufficient bond strength between the anchor section and the borehole wall rock mass, ultimately affecting the anchoring force and long-term durability of the anchor cable. Even with conventional segmented grouting methods, the upper grouted section may still be disturbed due to borehole collapse when the grouting pipe is withdrawn after grouting, causing defects in the grouting body.

[0004] To address the aforementioned problems, engineering practice has attempted measures such as increasing grouting pressure, adding accelerators, or increasing the grout volume, but with limited effectiveness. Increasing grouting pressure often leads to more severe grout loss along fractures and may even trigger rock mass splitting; while adding accelerators can accelerate grout setting, the problem of grout loss before initial setting remains unresolved; increasing the grout volume results in material waste and cannot guarantee grouting quality. These attempts have failed to fundamentally solve the coupled problem of borehole collapse and grout loss in highly weathered and fractured rock masses. Therefore, a prestressed anchor cable construction method that can effectively cope with the special geological conditions of highly weathered and fractured rock masses is needed. Summary of the Invention

[0005] One object of the present invention is to solve at least the above-mentioned problems and to provide at least the advantages that will be described later.

[0006] Another objective of this invention is to provide a rapid installation and grouting method for prestressed anchor cables suitable for strongly weathered fractured rock masses, which solves the problems of poor anchoring quality caused by easy collapse of the borehole wall after drilling and easy loss of grout during the grouting process in existing prestressed anchor cable construction methods in strongly weathered fractured rock masses.

[0007] To achieve these objectives and other advantages according to the present invention, a method for rapid installation and grouting of prestressed anchor cables suitable for strongly weathered and fractured rock masses is provided, comprising the following steps:

[0008] S1. Drilling with casing: Drilling is carried out using an eccentric casing drilling tool combination. During the drilling process, the casing is advanced synchronously. After drilling to the designed hole depth, the casing is left in the hole as a temporary protective wall. The bottom end of the casing is located at the bottom of the hole, and the top end is exposed at the hole opening.

[0009] S2. Anchor cable insertion and pressure-bearing component installation: The prestressed anchor cable with a pressure-bearing grouting component is inserted into the casing insertion hole. A grouting pipe is pre-embedded on the prestressed anchor cable, and the outlet of the grouting pipe is located at the far end of the pressure-bearing grouting component. The pressure-bearing grouting component includes at least one expandable capsule-type grouting plug.

[0010] S3. Segmented Pressure Controllable Grouting: S3a. Pressure medium is injected into the capsule-shaped grout stop plug through the grouting pipe, causing it to expand and tightly fit against the borehole wall or casing, forming a closed grouting zone; S3b. Pressure grouting is performed within the grouting zone, and the grouting pressure and flow rate are monitored in real time during the grouting process; S3c. When the grouting pressure reaches a first set value and the grouting flow rate drops below a preset threshold, grouting is stopped and pressure is maintained for a first predetermined time until grout returns to the borehole or the pressure maintenance time ends; The first set value and the first predetermined time are preset according to geological conditions and design requirements;

[0011] S4. Segmented Removal and Repeated Grouting of the Casing: S4a. After the grout returns to the borehole or after the first predetermined time has elapsed, the casing is pulled out upwards for a first predetermined length to expose a new rock mass segment; S4b. Repeat step S3 to perform pressure grouting on the exposed new rock mass segment; S4c. Repeat steps S4a and S4b until the grouting of the entire anchoring section is completed, and finally the casing is completely removed from the borehole.

[0012] S5. Tensioning and Anchoring: After the grout strength reaches the design requirements, the anchor cables are tensioned and locked, and finally the anchors are sealed.

[0013] Preferably, in step S1, the diameter of the eccentric drill bit in the eccentric casing assembly is smaller than the inner diameter of the casing, and high-pressure air or foam is injected into the bottom of the hole through the drill rod during drilling to cool the drill bit and carry away rock cuttings.

[0014] Preferably, in step S2, the pressure-bearing grout-stopping assembly further includes a check valve located at the distal end of the capsule-type grout-stopping plug, the check valve being connected to the outlet of the grouting pipe; the steel strands of the prestressed anchor cable are wrapped with a peelable sheath, the peelable sheath rupturing when the grouting pressure reaches a second set value, the second set value being greater than the first set value in step S3c.

[0015] Preferably, in step S3, the grout used for pressure grouting is a modified cement-based grout with added early strength agent and micro-expansion agent, and its initial setting time is controlled between 1 hour and 2 hours.

[0016] Preferably, in step S3, the pressure grouting adopts a dynamic pressure control mode, and the grouting pressure is adjusted in real time according to the grout pressure feedback signal returned from the far end of the capsule-type grout stop plug, so that the grouting pressure is always kept within the range of 0.9 times to 1.1 times the first set value until the grouting is completed.

[0017] Preferably, before step S1, the method further includes step S0, which involves intelligent pre-matching and dynamic optimization of construction parameters: determining the rock mass integrity coefficient, joint development degree, and permeability coefficient based on the geological survey report; and calculating and outputting the first set value, preset threshold, first predetermined length, and initial setting time control range of the grout in step S3 for subsequent steps S3 and S4 through a pre-constructed geological condition-construction parameter correlation model, as the initial execution parameters for subsequent steps S3 and S4.

[0018] During the construction processes in steps S3 and S4, the actual grouting pressure, flow rate change curves, and grouting volume data are collected and compared with the predicted curves of the geological conditions-construction parameter association model. When the deviation between the actual curve and the predicted curve exceeds a preset deviation threshold, the model correction program is triggered. The geological conditions-construction parameter association model is incrementally learned and updated based on the actual construction data, and the updated parameters are rewritten into the construction control system for subsequent anchor cable hole construction.

[0019] Preferably, the segmented pressure controllable grouting in step S3 further includes the following intelligent adaptation step:

[0020] S3d. During the grouting process, the grouting pressure P and grouting flow rate Q are monitored in real time, and the time-varying curves of PQ are plotted.

[0021] S3e. Based on the characteristic parameters of the PQ time-varying curve, determine the fracture development type of the rock mass in the current grouting section in real time; the fracture development type includes at least severe grout leakage type, microfracture permeability type, and dense type;

[0022] S3f. Based on the identified fracture development type, dynamically adjust the grouting control parameters of the current grouting section; where:

[0023] If the problem is identified as severe grout leakage, the grouting system is controlled to execute a first grouting strategy, which includes reducing the target grouting pressure setting value, and / or increasing the grout viscosity, and / or injecting a quick-setting material.

[0024] If the grouting system is determined to be of the microcrack permeable type, the grouting system is controlled to execute a second grouting strategy, which includes increasing the target grouting pressure setpoint and / or extending the pressure holding time.

[0025] If the grouting system is determined to be dense, the grouting system is controlled to execute a third grouting strategy, which includes switching to an intermittent grouting mode after the grouting pressure reaches the basic set value.

[0026] S3g. Repeat steps S3d to S3f until the grouting stop condition for the current section is met, and record the final grouting parameters and judgment results for that section as a quality file.

[0027] Preferably, after step S5, step S6, intelligent assessment of anchoring quality and parameter self-optimization, is also included:

[0028] After completing the grouting construction of all anchor cable holes, at least some of the anchor cable holes are subjected to non-destructive testing to obtain anchorage quality indicators, which include at least the grouting fullness and the abnormal wave velocity index of the anchorage section.

[0029] Collect the final grouting parameters and crack discrimination results recorded in step S3g during the construction of each anchor cable hole, and construct a sample dataset together with the anchoring quality index;

[0030] Based on the sample dataset, an anchorage quality prediction model was trained, and a mapping relationship between construction parameters, crack type and anchorage quality was established.

[0031] The anchoring quality prediction model is embedded into the geological condition-construction parameter correlation model to optimize the initial construction parameter settings for subsequent projects.

[0032] Preferably, after step S6, step S7, digital twin and virtual pre-simulation of the construction process, is also included:

[0033] During construction, based on geological survey data, real-time collected drilling parameters, grouting parameters, and fracture discrimination results recorded in step S3g, a digital twin model of the current anchor cable hole is constructed. The digital twin model includes the three-dimensional structure of the rock mass, the borehole trajectory, the grouting diffusion range, and the anchoring section morphology.

[0034] The digital twin model is compared with the design model in real time to identify construction deviations and generate visual early warning information; the construction deviations include at least one of drilling deviation, grouting beyond the range, and insufficient filling;

[0035] After the current anchor hole construction is completed, the digital twin model is inverted and calibrated based on the actual construction data of the hole and the obtained anchoring quality indicators to make it consistent with the final state of the physical anchor hole.

[0036] The calibrated digital twin model is used as a virtual test platform. The proposed construction parameters for subsequent anchor holes are input to conduct virtual grouting simulation and predict the grouting diffusion range and anchoring quality under different construction parameter conditions.

[0037] The construction parameters for subsequent anchor holes are optimized based on the results of the virtual simulation, and the optimized parameters are automatically written into the construction control system to guide the actual construction of subsequent anchor holes.

[0038] The digital twin models of each anchor cable hole are linked together in the construction sequence to form a digital archive of the entire slope protection project's construction process, which can be used for long-term quality traceability and health monitoring.

[0039] The present invention has at least the following beneficial effects:

[0040] First, by drilling with casing and leaving the casing inside the hole as a temporary protective wall, the problem of easy collapse of the hole wall after drilling in strongly weathered and fractured rock masses was solved, providing a stable channel for the smooth insertion of anchor cables and subsequent grouting operations.

[0041] Secondly, a capsule-type grout stopper is used to form a closed grouting zone. Combined with pressure-controlled grouting and flow monitoring, grouting is stopped and pressure is maintained when the grouting pressure reaches the set value and the flow rate drops to the threshold. This effectively prevents the grout from flowing along the cracks and improves the grouting fullness and the bonding quality between the anchoring section and the borehole wall rock mass.

[0042] Third, by using a cyclical operation of segmented casing withdrawal and repeated grouting, progressive grouting from the bottom of the hole to the opening was achieved, ensuring that each grouting segment was completed under wall protection conditions, avoiding disturbance to the grouting segment due to hole collapse, and ensuring the consistency of grouting quality throughout the entire hole.

[0043] Fourth, by combining pressure grouting with synchronous casing withdrawal, the grouting operation and casing withdrawal are carried out in tandem, shortening the construction cycle of a single hole and realizing the rapid installation and efficient grouting of prestressed anchor cables in strongly weathered and fractured rock masses.

[0044] Fifth, through intelligent parameter matching, real-time crack type identification, anchorage quality assessment, and digital twin virtual simulation, construction parameters can be dynamically optimized based on geological conditions and real-time feedback, realizing closed-loop quality control from single-hole construction to the overall project, and improving the reliability and long-term stability of the anchorage project.

[0045] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Detailed Implementation

[0046] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0047] This invention discloses a method for rapid installation and grouting of prestressed anchor cables suitable for strongly weathered fractured rock masses, comprising the following steps:

[0048] S1. Drilling with casing: Drilling is carried out using an eccentric casing drilling tool combination. During the drilling process, the casing is advanced synchronously. After drilling to the designed hole depth, the casing is left in the hole as a temporary protective wall. The bottom end of the casing is located at the bottom of the hole, and the top end is exposed at the hole opening.

[0049] S2. Anchor cable insertion and pressure-bearing component installation: The prestressed anchor cable with a pressure-bearing grouting component is inserted into the casing insertion hole. A grouting pipe is pre-embedded on the prestressed anchor cable, and the outlet of the grouting pipe is located at the far end of the pressure-bearing grouting component. The pressure-bearing grouting component includes at least one expandable capsule-type grouting plug.

[0050] S3. Segmented Pressure Controllable Grouting: S3a. Pressure medium is injected into the capsule-shaped grout stop plug through the grouting pipe, causing it to expand and tightly fit against the borehole wall or casing, forming a closed grouting zone; S3b. Pressure grouting is performed within the grouting zone, and the grouting pressure and flow rate are monitored in real time during the grouting process; S3c. When the grouting pressure reaches a first set value and the grouting flow rate drops below a preset threshold, grouting is stopped and pressure is maintained for a first predetermined time until grout returns to the borehole or the pressure maintenance time ends; The first set value and the first predetermined time are preset according to geological conditions and design requirements;

[0051] S4. Segmented Removal and Repeated Grouting of the Casing: S4a. After the grout returns to the borehole or after the first predetermined time has elapsed, the casing is pulled out upwards for a first predetermined length to expose a new rock mass segment; S4b. Repeat step S3 to perform pressure grouting on the exposed new rock mass segment; S4c. Repeat steps S4a and S4b until the grouting of the entire anchoring section is completed, and finally the casing is completely removed from the borehole.

[0052] S5. Tensioning and Anchoring: After the grout strength reaches the design requirements, the anchor cables are tensioned and locked, and finally the anchors are sealed.

[0053] In the above technical solution, a method for rapid installation and grouting of prestressed anchor cables suitable for strongly weathered and fractured rock masses is described in the following specific implementation.

[0054] The drilling operation begins with casing drilling. A medium- or high-pressure open-pit down-the-hole hammer drill rig, equipped with an eccentric casing drilling tool assembly, can be used. This assembly includes a retractable eccentric drill bit, an impactor, a casing shoe, and several casings. The casings can be seamless steel pipes with a diameter of 146mm or 168mm, with single-section lengths typically 1.0m, 2.0m, or 3.0m, and a wall thickness of not less than 6mm. After the drill rig is in place and the hole position and inclination are adjusted, drilling begins. During drilling, the casings advance synchronously with the casing shoe, always remaining near the bottom of the hole to prevent collapse. Simultaneously, high-pressure air or foam can be injected into the bottom of the hole through the center hole of the drill pipe as a cuttings removal medium. The air pressure can be controlled between 0.6MPa and 1.2MPa to cool the drill bit and blow cuttings out of the hole. Once the designed hole depth is reached, impact and advancement are stopped. At this point, the bottom of the casing is stable on the bedrock at the bottom of the hole, and the top of the casing protrudes about 200mm to 300mm from the hole opening for easy subsequent operations. The eccentric drill string is reversed to retract the eccentric drill bit, and the drill rod is pulled out, leaving the casing inside the hole as temporary wall protection.

[0055] Next, the anchor cable is inserted and the pressure-bearing assembly is installed. Prestressed anchor cables are fabricated on the ground, and the anchor cable body can consist of 3 to 7 high-strength, low-relaxation steel strands with a diameter of 15.2 mm or 17.8 mm. A pressure-bearing grout-stopping assembly is pre-installed at the beginning of the anchoring section of the anchor cable. This assembly includes an expandable capsule-type grout-stopping plug and a check valve. The capsule-type grout-stopping plug can be made of rubber or a high-molecular elastic material, and its expanded outer diameter is slightly larger than the inner diameter of the casing. The check valve is installed at the distal end of the capsule-type grout-stopping plug and connected to the outlet of a grouting pipe pre-embedded in the anchor cable body. This grouting pipe is generally made of polyethylene or polyamide flexible tubing capable of withstanding a certain pressure, with an inner diameter of 20 mm to 25 mm, extending to near the borehole opening. A peelable plastic sheath can be wrapped around the surface of the steel strands to isolate the steel strands from the grout during the initial grouting stage. The fabricated anchor cable, along with the grouting pipe and grout-stopping assembly, is slowly pushed to the bottom of the borehole by manual labor or a small winch through the temporary protective casing. During the pushing process, avoid twisting or scraping the casing wall of the anchor cable to ensure accurate positioning of the grout-stopping component. At this time, the capsule-type grout-stopping plug remains in contact with the inner wall of the casing but does not expand, and the anchor cable remains stationary.

[0056] Then, segmented pressure-controlled grouting is performed. The grouting equipment can be a dual-liquid grouting pump or a frequency-controlled grouting pump, equipped with a pressure sensor and an automatic flow recorder. The pressure sensor is installed on the grouting pipe at the borehole opening to collect real-time pressure signals. First, a pressurized medium, such as clean water or compressed air, is injected into the capsule-type grout stopper through a dedicated pressurization pipeline, bringing the pressure to 0.8 MPa to 1.2 MPa. After the capsule expands, it adheres tightly to the inner wall of the casing due to friction, forming a closed grouting zone. Next, the grouting pump is started, and modified cement-based grout is injected into this closed zone through the grouting pipe. This grout can be a mixture of ordinary Portland cement with added early-strength agents such as triethanolamine and micro-expansion agents such as UEA expansion agents. Its water-cement ratio can be controlled between 0.4 and 0.5, and the initial setting time is designed to be 1 to 2 hours. During grouting, the pressure signal collected by the pressure sensor is transmitted to the PLC controller. The PLC controller uses a PID algorithm to control the motor speed of the variable frequency grouting pump, thereby dynamically adjusting the grouting pressure to keep it within 0.9 to 1.1 times the first set value. When the grouting pressure reaches the first set value, for example, 1.5 MPa to 2.5 MPa, and the grouting flow rate drops below a preset threshold, for example, below 5 L / min, grouting stops and is maintained for a first predetermined time, for example, 5 to 10 minutes. During the pressure maintenance process, the grout return at the borehole opening is observed. If thick grout returns from the borehole opening or the pressure maintenance time ends, this section of grouting is complete. If the grouting pressure reaches the second set value, for example, 3.0 MPa to 4.0 MPa, which is higher than the first set value, the peelable sheath outside the steel strand will rupture under this pressure, and the grout will enter the casing and directly contact the steel strand. Before the sheath ruptures, the grout only fills the annular space between the borehole wall and the casing and does not contact the steel strand.

[0057] After the first stage of grouting and pressure holding is completed, the stage of segmented withdrawal and repeated grouting of the casing begins. To ensure reliable movement of the capsule-type grout stopper during casing lifting and maintain the stationary position of the anchor cable, the following structural fit can be adopted: the capsule-type grout stopper is fitted onto the outside of the anchor cable through a sliding sleeve. A low-friction coating is applied between the inner wall of the sliding sleeve and the anchor cable, forming a sliding fit; the outer wall of the sliding sleeve is fixedly connected to the capsule-type grout stopper. Limiting rings are provided at both ends of the sliding sleeve to limit the maximum displacement of the capsule relative to the anchor cable. In terms of mechanical design, the capsule-type grout stopper is made of nitrile rubber, with a static friction coefficient between it and the inner wall of the casing of not less than 0.5 under pressure; the friction coefficient between the sliding sleeve and the anchor cable, after low-friction coating treatment, is not higher than 0.1. With the above material and structural configuration, when the capsule expansion pressure is 0.8MPa to 1.2MPa, the static friction between the capsule and the inner wall of the sleeve is significantly greater than the friction between the sliding sleeve and the anchor cable, and the safety factor is not less than 1.5.

[0058] Based on this, during the casing removal operation, the capsule is kept in an inflated state. The casing is then lifted upwards at a uniform speed using a casing puller or drilling rig's lifting device, with the lifting speed controlled between 0.2 m / min and 0.5 m / min. The capsule-type grout stopper, relying on its friction with the inner wall of the casing, drives the sliding sleeve to slide synchronously upwards along the anchor cable body, keeping the anchor cable body stationary, thus exposing a new section of rock mass to be grouted. After lifting, a new section of rock mass to be grouted is exposed at the bottom of the borehole. At this point, the capsule-type grout stopper remains inflated in its new position, continuing to form a closed grouting zone. Then, the pressure grouting process in step S3 above is completely repeated to grout this newly exposed rock mass. This cycle continues, grouting a section after each casing section is pulled out, until the entire anchoring section is grouted. The grouting parameters for each section can be fine-tuned according to geological conditions, but the overall control logic remains the same. Finally, the casing is completely removed from the borehole.

[0059] Finally, tensioning and anchor sealing are performed. After grouting of the entire anchorage section is completed and the grout strength meets design requirements (e.g., the compressive strength of the grout sample reaches 25 MPa or higher, or 80% of the design strength), anchor cable tensioning is carried out. Anchor plates, anchorages, and jacks are installed at the borehole opening. Tensioning can be performed using either overall staged tensioning or single-strand symmetrical tensioning, with the final tension force locked at the design tonnage. After tensioning and locking, excess length of steel strand is cut off using an abrasive cutter, leaving approximately 50mm to 100mm outside the anchorage. Finally, the anchor head is sealed and protected with fine aggregate concrete or high-strength cement mortar, completing the entire construction process.

[0060] This technical solution utilizes casing drilling with a casing layer as a temporary protective wall to create a stable channel in highly weathered and fractured rock masses, preventing borehole collapse from affecting subsequent procedures. Employing capsule-type grout stoppers that can be withdrawn in sections along with the casing enables segmented high-pressure grouting of the anchoring section from bottom to top. Precise control of grouting pressure and volume facilitates effective grout diffusion within the fractures. Real-time monitoring and dynamic adjustment of pressure and flow rate during grouting adapts to the uneven distribution of fractures in the rock mass. A peelable sheath around the steel strand isolates the grout in the initial stage of grouting, ensuring free elongation of the steel strand during tensioning. The capsule-type grout stopper's design, relying on friction to lift with the casing, simplifies the process of repeated grouting. Overall, this method helps improve the quality controllability of anchor cable construction in highly weathered and fractured rock masses.

[0061] In another technical solution, in step S1, the diameter of the eccentric drill bit in the eccentric casing assembly is smaller than the inner diameter of the casing, and high-pressure air or foam is injected into the bottom of the hole through the drill rod during drilling to cool the drill bit and carry away rock cuttings.

[0062] In the above technical solution, an eccentric casing drilling tool assembly is used in the casing drilling operation in step S1. This assembly includes a retractable eccentric drill bit, an impactor, a casing shoe, and several casings. The maximum rotation diameter of the eccentric drill bit is slightly larger than the outer diameter of the casing to ensure smooth casing follow-up, but its diameter is smaller than the inner diameter of the casing, typically 10mm to 20mm smaller. For example, when the inner diameter of the casing is 130mm, the diameter of the eccentric drill bit can be selected as 115mm to 120mm. This diameter difference forms an annular gap between the drill bit and the inner wall of the casing, which is beneficial for the passage of the cuttings removal medium. During drilling, the drilling rig drives the eccentric drill bit to rotate and impact and break the rock through the drill rod, and the casing follows synchronously under the action of the casing shoe. At the same time, high-pressure air or foam is continuously injected into the bottom of the hole through the center hole of the drill rod as a cuttings removal medium. The pressure of the high-pressure air can be controlled between 0.6MPa and 1.2MPa, and the cuttings removal rate can be adjusted according to the hole diameter and the drilling speed. High-pressure air is ejected from the bottom of the drill pipe, carrying broken rock cuttings that flow upwards along the annular gap between the drill pipe and the casing, eventually exiting the hole. This process not only promptly removes rock cuttings from the bottom of the hole to prevent repeated breaking, but also effectively cools the drill bit, preventing it from overheating and wearing down in hard rock. Once the designed hole depth is reached, impact and advance are stopped, the eccentric drill string is reversed to retract the eccentric drill bit, and then the drill pipe is pulled out, leaving the casing inside the hole as temporary wall protection.

[0063] In this technical solution, step S1 achieves efficient cooling and cuttings removal during casing drilling by using an eccentric drill bit with a diameter smaller than the inner diameter of the casing, combined with high-pressure air or foam for cuttings removal. The annular gap between the eccentric drill bit and the inner wall of the casing provides a smooth return channel for rock cuttings. High-pressure air or foam cools the drill bit while rapidly carrying the rock cuttings out of the hole, preventing cuttings from accumulating and jamming the drill bit, thus improving drilling efficiency. This design enables casing drilling to be successfully implemented in highly weathered and fractured rock masses, creating favorable in-hole conditions for subsequent anchor cable placement and grouting.

[0064] In another technical solution, in step S2, the pressure-bearing grout-stopping assembly further includes a check valve located at the distal end of the capsule-type grout-stopping plug, the check valve being connected to the outlet of the grouting pipe; the steel strands of the prestressed anchor cable are wrapped with a peelable sheath, the peelable sheath rupturing when the grouting pressure reaches a second set value, the second set value being greater than the first set value in step S3c.

[0065] In the above technical solution, during the anchor cable insertion and pressure-bearing component installation in step S2, the pressure-bearing grout-stopping component includes an expandable capsule-type grout-stopping plug and a check valve installed at the distal end of the capsule-type grout-stopping plug. This check valve can be a spring-loaded check valve or a ball-type check valve, and its body material can be stainless steel or brass, with a pressure resistance greater than the design maximum grouting pressure, for example, not less than 5.0 MPa. The inlet end of the check valve is connected to the outlet end of the grouting pipe, with the outlet end facing the bottom of the hole. The function of the check valve is to allow grout to flow from the grouting pipe into the hole, but to prevent grout from flowing back into the grouting pipe when the pressure decreases. During anchor cable fabrication, the check valve is fixed to the end of the grouting pipe by threads or clamps and is tied together with the capsule-type grout-stopping plug to the designed position on the anchor cable body. Simultaneously, each steel strand of the prestressed anchor cable is wrapped with a peelable plastic sheath. The peelable sheath can be made of polyethylene or polypropylene, with a thickness of approximately 0.5mm to 1.0mm. A lubricating layer is applied between its inner wall and the steel strand to facilitate subsequent peeling. The peelable sheath covers the entire length of the steel strand. Depending on design requirements, the sheath's coverage area can be divided into two sections: the section corresponding to the anchorage length has a pre-set burst pressure of a second predetermined value, used to break and bond during high-pressure grouting; the section corresponding to the free length has a burst pressure set higher than the second predetermined value, or remains intact throughout the grouting process to ensure the steel strand can freely elongate during tensioning. The fabricated anchor cable, along with the grouting pipe, check valve, capsule-type grout stop plug, and the steel strand wrapped with the peelable sheath, is slowly pushed through the temporary protective sleeve to the bottom of the hole, ensuring accurate positioning of each component. The burst pressure of the sheath, i.e., the second set value, is determined in advance through material selection and thickness design. For example, it can be set to 3.0MPa to 4.0MPa, which is higher than the first set value of grouting pressure maintenance in step S3c, such as 1.5MPa to 2.5MPa. The fabricated anchor cable, together with the grouting pipe, check valve, capsule-type grout stop plug, and steel strand wrapped with a peelable sheath, is slowly pushed through the temporary protective sleeve to the bottom of the hole, ensuring that the position of each component is accurate.

[0066] In the segmented pressure-controlled grouting process of step S3, the capsule-type grout stop plug is first expanded and sealed in the grouting zone through the pressurization pipeline. Then, the grouting pump is started and grout is injected through the grouting pipe. After the grout reaches the bottom of the hole through the grouting pipe, it pushes open the check valve and enters the sealed grouting zone, beginning to fill the annular space between the hole wall and the casing, as well as the fissures in the surrounding rock mass. The check valve remains open throughout the grouting process. Once the grouting pump stops working or the grouting pressure decreases, the check valve immediately closes to prevent the grout from flowing back into the hole. The grouting pressure is monitored and dynamically adjusted in real time. When the grouting pressure reaches the first set value and the grouting flow rate drops below the preset threshold, grouting is stopped and pressure is maintained for a first predetermined time. If the grouting pressure continues to rise and reaches the second set value, the peelable sheath outside the steel strand will rupture under this pressure. After the sheath ruptures, the grout can enter the casing and directly contact the surface of the steel strand. After the grout hardens, an adhesive force is formed between the steel strand and the grout. Before the sheath breaks, the grout is isolated in the annular space between the casing and the borehole wall, and does not come into contact with the steel strands. Therefore, the steel strands remain free before tensioning.

[0067] In this technical solution, the check valve effectively prevents the grout from flowing back into the grouting pipe during grouting intervals or pressure fluctuations, ensuring the stability of grouting pressure and grout distribution, and avoiding incomplete grouting or pipe blockage caused by grout backflow. The design of a peelable sheath covering the steel strand, combined with two-stage pressure control, achieves functional zoning of the grouting process. In the initial stage of grouting, the grout only fills the surrounding rock fissures and annular voids. After the surrounding rock grouting is completed and the pressure increases, the sheath ruptures, and the grout then bonds with the steel strand to form anchoring force. This design avoids the grout prematurely encasing the steel strand during grouting, ensuring that the tensioned section of the steel strand can freely elongate during tensioning, and also making the bond between the anchored section of the steel strand and the grout more reliable.

[0068] In another technical solution, in step S3, the grout used for pressure grouting is a modified cement-based grout with added early strength agent and micro-expansion agent, and its initial setting time is controlled between 1 hour and 2 hours.

[0069] In the above technical solution, during the segmented pressure controllable grouting process in step S3, the grout used is a modified cement-based grout. This grout can be made from ordinary Portland cement with a strength grade not lower than 42.5 as the basic cementitious material. An accelerator and a micro-expansion agent are added to the cement in proportion. The accelerator can be one or more combinations of triethanolamine, sodium sulfate, or calcium formate, and its dosage can be controlled to be 0.02% to 0.05% of the cement weight for triethanolamine, or 1% to 2% for sodium sulfate. The micro-expansion agent can be UEA expansion agent, CSA expansion agent, or magnesium oxide expansion agent, and its dosage can be controlled to be 8% to 12% of the cement weight. The water-cement ratio of the grout can be controlled between 0.4 and 0.5. During preparation, first add the calculated weight of water to the mixer, then add the cement, accelerator, and micro-expansion agent, and mix thoroughly for 3 to 5 minutes until the grout is uniform and free of lumps. By adjusting the type and dosage of the early-strength agent and the water-cement ratio, the initial setting time of the grout can be controlled within the range of 1 to 2 hours. The initial setting time can be measured using a Vicat apparatus to ensure that it meets the design requirements. The prepared grout is injected into the borehole through the grouting pipe using a grouting pump. During the grouting process, the grout has good fluidity and can fill rock fissures and annular voids. After grouting is completed, the grout initially sets and begins to develop strength within the predetermined time. At the same time, the micro-expansion agent undergoes moderate expansion during the hydration reaction, compensating for the shrinkage during the grout hardening process.

[0070] This technical solution employs modified cement-based grout with added early-strength agents and micro-expansion agents, controlling the initial setting time to 1 to 2 hours. This facilitates rapid installation of anchor cables in strongly weathered and fractured rock masses. The addition of the early-strength agent allows the grout to quickly reach the necessary early strength after grouting, shortening the waiting time for subsequent tensioning operations. The addition of the micro-expansion agent causes the grout to expand slightly during hardening, better filling rock fissures and annular voids left after casing removal, improving the adhesion and density between the grout and the rock mass and steel strands. Controlling the initial setting time to 1 to 2 hours ensures sufficient operating time for the grout during grouting while avoiding grout loss or delayed strength development due to slow setting.

[0071] In another technical solution, in step S3, the pressure grouting adopts a dynamic pressure control mode. Based on the grout pressure feedback signal returned from the far end of the capsule-type grout stop plug, the grouting pressure is adjusted in real time so that the grouting pressure is always kept within the range of 0.9 to 1.1 times the first set value until the grouting is completed.

[0072] In the above technical solution, during the segmented pressure controllable grouting process in step S3, the grouting system operates in a dynamic pressure control mode. To achieve this mode, a miniature pressure sensor can be pre-embedded at the distal end of the capsule-type grout stop plug, near the bottom of the hole, or a pressure measuring pipeline can be led out from the pressure detection interface attached to the check valve at the grouting pipe outlet to obtain the grout pressure feedback signal at that location. This pressure sensor can be a resistance strain gauge or piezoresistive pressure sensor, with a range of 0MPa to 5MPa and an accuracy of not less than 0.5%. The pressure sensor is connected to the ground-based PLC controller via a signal cable or wireless transmission module. The grouting pump is a variable frequency speed-controlled screw pump or piston pump, with its motor driven by a frequency converter. The control signal input terminal of the frequency converter is connected to the analog output terminal of the PLC controller. After grouting begins, the capsule-type grout stop plug first expands to seal the grouting section. Then, the grouting pump is started for grouting. The PLC controller collects the pressure signal returned by the pressure sensor at the distal end of the capsule-type grout stop plug in real time and compares this real-time pressure value with the preset target pressure value, i.e., the first set value, for example, 1.5MPa to 2.5MPa. The PLC controller runs a PID control algorithm internally, calculates the output control quantity based on the pressure deviation value, and changes the motor speed of the grouting pump by adjusting the frequency of the frequency converter, thereby dynamically adjusting the grouting pressure and flow rate. The control objective is to maintain the grout pressure at the distal end of the capsule-type grout stop plug within 0.9 to 1.1 times the first set value. For example, if the first set value is 2.0MPa, the distal pressure should be maintained between 1.8MPa and 2.2MPa during the grouting process. When the grouting flow rate drops below a preset threshold, for example, below 5L / min, and the distal pressure stabilizes within the target range, the grouting section is considered to be compacted, and grouting can be stopped and the pressure holding stage can begin. This dynamic pressure control mode continues to operate throughout the grouting process until the grouting section is completed.

[0073] In this technical solution, precise control of the grouting pressure is achieved by employing a dynamic pressure regulation mode and using the grout pressure at the distal end of the capsule-type grout stopper as a feedback signal. Directly measuring the pressure at the end of the grouting section provides a more accurate reflection of the pressure state experienced by the grout as it diffuses through the fissures, avoiding control deviations caused by friction loss and local resistance when relying solely on orifice pressure as a reference. Maintaining the distal pressure within 0.9 to 1.1 times the first set value ensures sufficient pressure to drive the grout to fill the rock fissures while preventing excessive pressure from causing rock splitting or grout loss. This dynamic regulation method adapts to the resistance changes caused by the gradual filling of fissures during grouting, making the grouting process more stable and controllable.

[0074] In another technical solution, before step S1, there is also step S0, which involves intelligent pre-matching and dynamic optimization of construction parameters: determining the rock mass integrity coefficient, joint development degree, and permeability coefficient based on the geological survey report; and calculating and outputting the first set value, preset threshold, first predetermined length, and initial setting time control range of the grout in step S3 for subsequent steps S3 and S4 through a pre-constructed geological condition-construction parameter association model, as the initial execution parameters for subsequent steps S3 and S4.

[0075] During the construction processes in steps S3 and S4, the actual grouting pressure, flow rate change curves, and grouting volume data are collected and compared with the predicted curves of the geological conditions-construction parameter association model. When the deviation between the actual curve and the predicted curve exceeds a preset deviation threshold, the model correction program is triggered. The geological conditions-construction parameter association model is incrementally learned and updated based on the actual construction data, and the updated parameters are rewritten into the construction control system for subsequent anchor cable hole construction.

[0076] In the above technical solution, before drilling in step S1, intelligent pre-matching and dynamic optimization of construction parameters are first performed in step S0. Geological survey reports of the construction area are collected, and key geological parameters such as rock mass integrity coefficient, joint development degree, and permeability coefficient are extracted. The rock mass integrity coefficient can be obtained through acoustic testing or core recovery rate calculation, and its value range is typically 0 to 1, with values ​​closer to 1 indicating a more intact rock mass. The joint development degree can be determined through geological sketching and structural surface statistics, and can be quantified as the number of joints per unit volume of rock mass or the joint spacing. The permeability coefficient can be determined through on-site pressure water tests or pumping tests, with units of cm / s. These geological parameters are used as input data for subsequent model calculations.

[0077] A pre-constructed geological condition-construction parameter correlation model is used. This model can be built using a backpropagation (BP) neural network based on historical engineering data. The historical engineering data includes the three geological parameters mentioned above for completed anchor holes, as well as the corresponding successful construction parameters, including the first set value, preset threshold, first predetermined length, and grout initial setting time. The input layer of the BP neural network has 3 nodes, corresponding to the rock mass integrity coefficient, joint development degree, and permeability coefficient, respectively. The output layer has 4 nodes, corresponding to the first set value, preset threshold, first predetermined length, and grout initial setting time, respectively. Two hidden layers can be set, with 8 and 6 nodes respectively. The Levenberg-Marquardt algorithm is used for network training, with a training objective of a root mean square error less than 0.05. After training, the model internally stores the nonlinear mapping relationship between geological parameters and construction parameters. For new anchor holes, the measured geological parameters are input into a trained BP neural network. After forward calculation, the model automatically outputs the first set values ​​for subsequent steps S3 and S4, such as 1.5MPa to 2.5MPa, a preset threshold such as 5L / min, a first predetermined length such as 1.0m to 2.0m, and the control range for the initial setting time of the grout in step S3, such as 1 hour to 2 hours. These parameters are automatically written into the PLC controller or industrial computer in the construction control system as the initial execution parameters for subsequent construction.

[0078] During the construction processes in steps S3 and S4, the construction control system collects real-time data on actual grouting pressure, grouting flow rate, and casing extraction length at a sampling frequency of once per second, using pressure sensors and flow meters installed at the grouting pump outlet and displacement sensors installed on the casing extraction device. Based on this data, the system automatically plots curves showing the actual grouting pressure and flow rate changes over time and calculates the cumulative grouting volume for each segment. Simultaneously, the system uses a geological condition construction parameter association model based on the geological parameters of the current anchor hole to generate a predicted theoretical grouting pressure-flow rate curve and a theoretical cumulative grouting volume for that hole location. The deviation between the actual curve and the predicted curve is judged by setting a deviation threshold, which can be set as a pressure deviation exceeding 0.3 MPa, a flow rate deviation exceeding 2 L / min, or a cumulative grouting volume deviation exceeding 10%. When the deviation between the actual curve and the predicted curve exceeds the preset deviation threshold three times consecutively, the system automatically triggers a model correction program.

[0079] The correction program combines the actual geological parameters of the current anchor hole with data collected during construction, such as actual grouting pressure, flow rate, grouting volume, and casing pull-out length, into a new training sample. The system maintains a fixed-capacity sample database, for example, storing construction data for the most recent 200 anchor holes. When a new sample is generated, the sample database is updated according to the first-in, first-out principle, meaning that the oldest sample is deleted while the new sample is added. Then, based on the updated sample database, the system retrains the geological condition construction parameter association model using the same BP neural network structure and training algorithm as the initial model. Retraining can be performed automatically during construction breaks, such as every night or after every 5 anchor holes are completed. After training, the updated model parameters replace the original model, and the construction parameters for subsequent anchor holes are recalculated. The calculated optimized parameters are automatically written into the construction control system to guide the actual construction of subsequent anchor holes. This offline retraining method avoids the model instability problems that may arise from online incremental learning, while ensuring that the model can be continuously optimized with the accumulation of new data.

[0080] In this technical solution, adaptive matching between construction parameters and geological conditions is achieved through intelligent pre-matching of geological parameters before construction and dynamic optimization during construction. A BP neural network is used to establish a nonlinear mapping relationship between geological parameters and construction parameters, providing a scientific basis for initial parameter settings. During construction, real-time data acquisition and model prediction comparison enable timely detection of discrepancies between geological conditions and the survey report. Regular offline retraining updates the model, ensuring continuous optimization by absorbing new experience while avoiding uncertainties introduced to the control system by complex online learning algorithms. This closed-loop optimization mechanism allows construction parameters to gradually approach optimal values ​​as the project progresses, improving the consistency and adaptability of anchor cable construction quality.

[0081] In another technical solution, the segmented pressure controllable grouting in step S3 further includes the following intelligent adaptation step:

[0082] S3d. During the grouting process, the grouting pressure P and grouting flow rate Q are monitored in real time, and the time-varying curves of PQ are plotted.

[0083] S3e. Based on the characteristic parameters of the PQ time-varying curve, determine the fracture development type of the rock mass in the current grouting section in real time; the fracture development type includes at least severe grout leakage type, microfracture permeability type, and dense type;

[0084] S3f. Based on the identified fracture development type, dynamically adjust the grouting control parameters of the current grouting section; where:

[0085] If the problem is identified as severe grout leakage, the grouting system is controlled to execute a first grouting strategy, which includes reducing the target grouting pressure setting value, and / or increasing the grout viscosity, and / or injecting a quick-setting material.

[0086] If the grouting system is determined to be of the microcrack permeable type, the grouting system is controlled to execute a second grouting strategy, which includes increasing the target grouting pressure setpoint and / or extending the pressure holding time.

[0087] If the grouting system is determined to be dense, the grouting system is controlled to execute a third grouting strategy, which includes switching to an intermittent grouting mode after the grouting pressure reaches the basic set value.

[0088] S3g. Repeat steps S3d to S3f until the grouting stop condition for the current section is met, and record the final grouting parameters and judgment results for that section as a quality file.

[0089] In the above technical solution, the segmented pressure-controllable grouting process in step S3 further includes the following intelligent adaptation steps. The grouting system is equipped with a high-precision pressure sensor and an electromagnetic flow meter, which are installed on the grouting pipeline near the outlet of the grouting pump to collect grouting pressure P and grouting flow rate Q data in real time. The sensor signals are transmitted to the on-site industrial control computer or programmable logic controller at a sampling frequency of no less than 10 times per second. The control system has a built-in data recording and analysis module, which can dynamically plot the PQ time-varying curve on the display screen based on the real-time collected pressure and flow rate data, with time as the horizontal axis and pressure and flow rate as the vertical axes.

[0090] During grouting, the control system continuously analyzes the morphological characteristics of the PQ time-varying curve and identifies the fracture development type of the rock mass in the current grouting section in real time according to preset discrimination rules. The discrimination rules can be set based on statistical analysis results of a large amount of historical grouting data. For example, if the pressure remains at a low level (e.g., below 0.5 MPa) after grouting starts and does not rise significantly for a long time, while the flow rate remains high (e.g., exceeding 30 L / min), it can be identified as a severe leakage type, indicating that the rock mass in this section has wide fractures or interconnected channels. When the grouting pressure rises slowly at a relatively stable rate (e.g., 0.1 MPa to 0.3 MPa per minute), and the flow rate decreases steadily with the pressure increase, and the curve does not fluctuate significantly, it can be identified as a micro-fracture permeability type, indicating that this section is dominated by small fractures. When the grouting pressure rises rapidly in a short period (e.g., exceeding 0.5 MPa per minute), while the flow rate drops rapidly to a low level (e.g., below 10 L / min), and the pressure fluctuation is small, it can be identified as a dense type, indicating that the rock mass in this section is relatively intact or the fractures have been rapidly filled.

[0091] Based on the identified crack development type, the control system automatically invokes a preset grouting strategy and dynamically adjusts the control parameters of the current grouting section. If the crack is identified as a severe leakage type, the control system executes the first grouting strategy. Specific measures include lowering the target grouting pressure setting from the conventional 2.0 MPa to 1.2 MPa to 1.5 MPa to reduce grouting intensity and minimize grout loss. Simultaneously, rapid-setting materials such as water glass are added to the grout through an auxiliary injection device next to the grouting pump to shorten the grout gel time to 30 to 60 seconds. Alternatively, if necessary, grouting can be paused and a cement-water glass dual-liquid grout injected for rapid sealing. If the crack is identified as a micro-crack infiltration type, the control system executes the second grouting strategy. Specific measures include raising the target grouting pressure setting from the conventional 2.0 MPa to 2.5 MPa to 3.0 MPa to drive the grout into the fine cracks with higher pressure. Simultaneously, the pressure holding time after grouting is extended from the conventional 5 minutes to 10 to 15 minutes to ensure the cracks are fully filled. If the grouting is determined to be dense, the control system executes the third grouting strategy. Specific measures include automatically switching to intermittent grouting mode after the grouting pressure reaches the basic set value, such as 2.0 MPa. That is, grouting for 2 minutes and stopping for 1 minute, and repeating this cycle 3 to 5 times. The repeated rise and fall of pressure promotes further compaction of the grout in the tiny gaps.

[0092] During each grouting stage, the above steps are repeated: continuous monitoring, real-time assessment, and dynamic adjustment, until the grouting stop conditions for that section are met, such as reaching the target pressure under the current strategy and the flow rate being lower than a preset threshold. After the grouting for that section is completed, the control system automatically stores the final grouting parameters recorded during this grouting process, including the actual pressure reached, total grouting volume, pressure holding time, and crack assessment results, in the database as part of the quality archive for the anchor cable hole, for subsequent quality traceability and analysis.

[0093] This technical solution achieves adaptive grouting control under different geological conditions by introducing real-time crack type identification based on PQ time-varying curves and dynamic adjustment of grouting strategies during the grouting process. For severely leaking sections, pressure reduction is used to achieve rapid setting and sealing, reducing ineffective grout loss. For micro-crack sections, pressure increase and extended holding time are used to ensure effective filling of small cracks. For dense sections, intermittent grouting promotes further compaction of the grout. This intelligent adaptive method makes the grouting process more refined, helps improve the consistency of construction quality in each grouting section, and creates a traceable digital construction record.

[0094] In another technical solution, after step S5, step S6, intelligent assessment of anchoring quality and parameter self-optimization, is also included:

[0095] After completing the grouting construction of all cable anchor holes, non-destructive testing is carried out on at least some of the cable anchor holes to obtain the anchoring quality indexes, and the anchoring quality indexes at least include the grouting fullness and the wave velocity anomaly index of the anchoring section;

[0096] Collect the final grouting parameters and fracture discrimination results recorded in step S3g during the construction of each cable anchor hole, and jointly construct a sample data set with the anchoring quality indexes;

[0097] Based on the sample data set, train an anchoring quality prediction model to establish the mapping relationship among construction parameters, fracture types and anchoring quality;

[0098] Embed the anchoring quality prediction model into the geological condition-construction parameter association model to optimize the setting of the initial construction parameters for subsequent projects.

[0099] In the above technical solution, after completing the tensioning and sealing of all cable anchor holes, that is, step S5, step S6 of intelligent evaluation of anchoring quality and parameter self-optimization is further carried out. First, non-destructive testing is carried out on at least some of the cable anchor holes to obtain the anchoring quality indexes. The non-destructive testing can be carried out by the acoustic wave reflection method or the impact elastic wave method. During the testing, sensors are installed at the exposed end of the cable anchor, and signals are excited by a small hammer or a vibrator, and the reflected wave signals are collected and analyzed. The anchoring quality indexes at least include the grouting fullness and the wave velocity anomaly index of the anchoring section. The grouting fullness can be calculated through the energy attenuation and phase change characteristics of the reflected wave, and is expressed as a percentage. For example, more than 90% is qualified. The wave velocity anomaly index of the anchoring section can be calculated by comparing the measured wave velocity with the theoretical wave velocity of the intact rock mass to reflect the compactness of the rock mass around the anchoring section.

[0100] Collect the final grouting parameters and fracture discrimination results recorded in step S3g during the construction of each cable anchor hole. The final grouting parameters include the actual grouting pressure, total grouting volume, pressure holding time, etc. of each section. The fracture discrimination results include the fracture types discriminated during the grouting process of each section, that is, the severe slurry leakage type, the micro-fracture penetration type or the compact type and their proportions. These construction process data and the non-destructive testing results of the corresponding cable anchor holes, that is, the grouting fullness and the wave velocity anomaly index, are jointly constructed into a sample data set. Each cable anchor hole constitutes a sample. The sample features include the statistical values of the grouting parameters of each section and the statistical values of the fracture types, and the sample labels include the grouting fullness and the wave velocity anomaly index.

[0101] Based on this sample dataset, an anchorage quality prediction model is trained. The prediction model can be established using multiple linear regression, or machine learning algorithms such as BP neural networks or support vector machines. Taking a BP neural network as an example, the number of nodes in the input layer is determined by the number of selected features, for example, it can be set to 10, representing the average grouting pressure, total grouting volume, proportion of severely leaking sections, proportion of micro-cracked sections, and proportion of dense sections, respectively. The number of nodes in the output layer is set to 2, corresponding to grouting fullness and wave velocity anomaly index, respectively. The hidden layer can be set to one, and the number of nodes can be determined based on empirical formulas, for example, set to 6 to 8. The network training uses a stochastic gradient descent algorithm, with the training objective being that the root mean square error between the predicted value and the actual detected value is less than 0.1. After training, the model establishes a nonlinear mapping relationship between construction parameters, crack types, and the final anchorage quality.

[0102] The trained anchorage quality prediction model is embedded into the geological condition construction parameter association model. Specifically, a quality prediction verification step is added to the output of the geological condition construction parameter association model. After the association model outputs a set of initial construction parameters based on geological parameters, these parameters, along with the predicted fracture type distribution, are input into the anchorage quality prediction model to calculate the expected anchorage quality indicators under these parameters. If the predicted grouting fullness is lower than a preset threshold (e.g., below 90%) or the wave velocity anomaly index exceeds the allowable range, the construction parameters output by the association model are automatically adjusted (e.g., appropriately increasing the grouting pressure or extending the pressure holding time), and the quality prediction is repeated until the predicted anchorage quality meets the requirements. Finally, the optimized construction parameters that meet the quality requirements are used as the initial execution parameters for the anchor cable hole.

[0103] In this technical solution, by introducing non-destructive testing and quality prediction model training after construction, the data-driven accumulation of construction experience is achieved. The anchoring quality prediction model establishes a quantitative relationship between construction process parameters and the final anchoring effect, providing a clear target for parameter optimization in subsequent projects. Embedding the quality prediction model into the geological condition construction parameter correlation model forms a closed-loop optimization mechanism from geological parameter input to construction parameter output and then to quality prediction verification. This enables virtual evaluation and pre-optimization of the proposed parameters before construction, helping to improve the first-pass yield of subsequent anchor cable hole construction quality.

[0104] In another technical solution, after step S6, step S7, digital twin and virtual pre-simulation of the construction process, is also included:

[0105] During construction, based on geological survey data, real-time collected drilling parameters, grouting parameters, and fracture discrimination results recorded in step S3g, a digital twin model of the current anchor cable hole is constructed. The digital twin model includes the three-dimensional structure of the rock mass, the borehole trajectory, the grouting diffusion range, and the anchoring section morphology.

[0106] The digital twin model is compared with the design model in real time to identify construction deviations and generate visual early warning information; the construction deviations include at least one of drilling deviation, grouting beyond the range, and insufficient filling;

[0107] After the current anchor hole construction is completed, the digital twin model is inverted and calibrated based on the actual construction data of the hole and the obtained anchoring quality indicators to make it consistent with the final state of the physical anchor hole.

[0108] The calibrated digital twin model is used as a virtual test platform. The proposed construction parameters for subsequent anchor holes are input to conduct virtual grouting simulation and predict the grouting diffusion range and anchoring quality under different construction parameter conditions.

[0109] The construction parameters for subsequent anchor holes are optimized based on the results of the virtual simulation, and the optimized parameters are automatically written into the construction control system to guide the actual construction of subsequent anchor holes.

[0110] The digital twin models of each anchor cable hole are linked together in the construction sequence to form a digital archive of the entire slope protection project's construction process, which can be used for long-term quality traceability and health monitoring.

[0111] In the above technical solution, during construction, step S7, digital twin and virtual pre-simulation of the construction process, is further carried out. First, the basic framework of the digital twin model is constructed. This model can be built based on a Building Information Modeling (BIM) platform or a 3D Geographic Information System (GIS) platform; for example, it can be further developed using general platforms such as Autodesk InfraWorks or Bentley OpenRoads. Before construction begins, geological survey data of the construction area, including rock strata interfaces, fracture zones, and groundwater distribution, is imported into the platform to form an initial 3D geological model. Simultaneously, the anchor cable design model, including borehole coordinates, inclination angle, anchorage length, and free section length, is imported into the platform to form a design baseline model.

[0112] During the casing drilling process in step S1, sensors on the drilling rig collect drilling parameters in real time, including drilling speed, impact pressure, and rotational torque. This data is uploaded to the digital twin platform in real time via a wireless transmission module. Based on changes in drilling parameters and geological survey data, the platform dynamically corrects the three-dimensional structure of the rock mass surrounding the borehole trajectory. For example, when the drilling speed suddenly increases, it indicates a possible encounter with a fractured zone, which is marked with different colors in the model. During the segmented grouting processes in steps S3 and S4, the grouting system uploads in real time the grouting pressure, grouting flow rate, cumulative grouting volume, and the fracture type identified in step S3g. Based on this data, the digital twin platform uses numerical simulation methods for grout diffusion to dynamically simulate and visualize the diffusion range of the grout in the current rock mass and the final anchoring section morphology. Grout diffusion simulation can be performed using finite element software such as COMSOL Multiphysics or FLAC3D as solvers embedded in the platform. In the simulation, the slurry is set as a Bingham fluid, with its yield stress set to 5 Pa to 15 Pa and its plastic viscosity set to 0.02 Pa·s to 0.05 Pa·s. Parameters such as the rock mass's permeability coefficient and fracture aperture are initially input using the average values ​​provided in the geological survey report; for example, the permeability coefficient can be taken as 1 × 10⁻⁶. -5 cm / s to 1×10 -3 The flow rate is cm / s, and the fracture aperture can be taken as 0.1 mm to 0.5 mm. The simulated boundary conditions are dynamically updated according to the grouting pressure and grouting flow rate. The pressure distribution and filling range of the grout in the fracture network are calculated, and the grout diffuser is displayed in the three-dimensional model using semi-transparent color blocks.

[0113] The platform compares the dynamically constructed digital twin model with the design model in real time. It automatically calculates the deviation between the actual drilling trajectory and the designed borehole position. When the deviation exceeds the allowable range (e.g., a horizontal deviation exceeding 5cm or an inclination deviation exceeding 2 degrees), the platform highlights the deviation location in the model and generates a visual warning message, which is then pushed to on-site management personnel. Simultaneously, the platform compares the actual grout diffusion range with the designed anchorage section range. If it finds that the grout diffusion exceeds the design range, potentially causing waste, or that insufficient diffusion results in filling voids, it also generates a warning message.

[0114] After completing all construction work on the current anchor cable hole, the digital twin model is inverted and calibrated based on the actual construction data of the hole, including the actual drilling trajectory, actual grouting parameters for each section, actual grouting volume, and the anchoring quality indicators of the hole obtained through non-destructive testing in subsequent step S6, including grout fullness and wave velocity anomaly index. The inversion calibration uses a particle swarm optimization algorithm. First, the objective function is defined as the root mean square error (RMSE) between the simulated and measured grout fullness distributions. The parameters of the particle swarm algorithm can be set as follows: population size of 30 particles, 80 iterations, inertia weight decreasing linearly from 0.9 to 0.4, and learning factors c1 and c2 both set to 2.0. The parameters to be optimized include the permeability coefficient and fracture aperture of the rock mass, and their search range can be set to 0.5 to 2 times the values ​​provided in the geological survey report. During the algorithm operation, each particle represents a set of parameters to be optimized. The grout diffusion simulation program is called to calculate the fullness distribution under this set of parameters, and the RMSE with the measured values ​​is calculated. When the RMSE is less than 0.05 or the optimal value shows no significant improvement after 15 consecutive iterations, the iteration is stopped, and the optimal parameter combination is output. The simulation is then rerun using this set of parameters to ensure that the final state of the digital twin model and the solid anchor cable hole are highly consistent.

[0115] The calibrated digital twin model is used as a virtual experimental platform for pre-optimization of construction parameters for subsequent anchor cable holes. Before constructing subsequent anchor cable holes, the proposed construction parameters, including grouting pressure, grouting time, and grout mix ratio for each section, are input into the calibrated digital twin model. Based on the geological data of the current hole location and the rock mass parameters obtained from the previous hole calibration, the model performs virtual grouting simulations to predict the grout diffusion range, anchorage section morphology, and expected anchorage quality under different construction parameter conditions. To obtain the optimal parameters within a reasonable timeframe, a two-stage optimization strategy can be adopted. The first stage employs orthogonal experimental design, selecting three levels for each construction parameter. For example, the grouting pressure can be selected at 1.5 MPa, 2.0 MPa, and 2.5 MPa levels, and the grouting time at 5 min, 8 min, and 11 min levels. An L9 orthogonal array is constructed for nine virtual simulations, and range analysis is used to screen out the key parameters that significantly affect grout fullness. The second stage refines the selected key parameters using a grid search method. For example, the grouting pressure is searched in 0.1 MPa increments within the range of 1.8 MPa to 2.2 MPa, while other parameters are fixed at their optimal levels. For each parameter combination, a virtual simulation is run to calculate the expected grouting fullness and total grouting volume. With a grouting fullness of no less than 90% as a constraint and the minimum total grouting volume as the optimization objective, the optimal combination of construction parameters is selected. These optimized parameters are automatically written into the PLC or industrial computer of the construction control system to guide the subsequent actual construction of the anchor cable holes.

[0116] Digital twin models of all anchor holes within the construction area are linked together in chronological order of construction completion to form a digital archive of the entire slope protection project's construction process. This digital archive includes a geological model, drilling trajectory, grouting process simulation, actual construction records, quality inspection results, and the final state model after inversion calibration for each anchor hole. This digital archive can be stored on a cloud server or a local database for use in project acceptance, long-term quality traceability, and post-construction health monitoring. During the project's operation phase, data can be monitored in real time using sensors embedded in the anchor cables and compared with the digital twin model to promptly detect changes in anchoring force or structural damage.

[0117] This technical solution utilizes a digital twin model of the construction process with real-time comparison and early warning to promptly detect and visualize construction deviations such as borehole deviation and grouting anomalies. Finite element method (FEM) software is embedded in the platform for grout diffusion simulation, providing a scientific basis for the dynamic visualization of the grouting process. Through inversion calibration of completed anchor cable holes, particle swarm optimization is employed to optimize rock mass parameters, continuously bringing the digital twin model closer to the actual physical state and improving the model's predictive accuracy. Two-stage virtual pre-simulation using the calibrated model allows for the evaluation of different parameters' effects at a reasonable computational cost before actual construction, enabling pre-optimization of construction parameters. Connecting the digital twin models of each hole forms a complete digital archive, providing a comprehensive and traceable record for the project and laying a data foundation for subsequent health monitoring and maintenance management.

[0118] <Example 1>

[0119] A slope treatment project involves a slope with a height of approximately 35 meters. The rock mass is strongly weathered granite, characterized by fractures, well-developed joints and fissures, and core samples that are mostly fragmented or sandy, classifying it as a typical strongly weathered and fractured rock mass. This slope requires prestressed anchor cable reinforcement. The designed anchor cable length is 18 meters, with an 8-meter anchored section and a 10-meter free section. The designed anchor cable tension is 800 kN.

[0120] Before construction, the borehole locations were determined by surveying and setting out on the slope, and a drilling platform was erected. A medium-pressure open-pit down-the-hole hammer drill was selected, equipped with a 146mm diameter eccentric casing drill bit. The casing was made of seamless steel pipe with an outer diameter of 146mm and a wall thickness of 6mm, with each section being 2.0m long. After the drill rig was in place, the drill rod inclination angle was adjusted, and drilling began. Compressed air was used for cuttings removal during drilling, with the air pressure controlled at approximately 0.8MPa. After drilling to the designed depth of 18m, the casing was left inside the borehole, with the top of the casing protruding approximately 250mm above the borehole opening. After withdrawing the eccentric drill bit, a small amount of rock cuttings was observed returning from the borehole opening, indicating good cuttings removal.

[0121] Prestressed anchor cables are fabricated on the ground. The anchor cable body consists of four 1860-grade steel strands with a diameter of 15.2 mm, cut according to design requirements. A pressure-bearing grout-stopping assembly is installed at the beginning of the anchoring section of the anchor cable. This assembly includes a capsule-type grout-stopping plug and a check valve. The capsule-type grout-stopping plug is made of rubber, approximately 300 mm in length, and its outer diameter can reach 140 mm after expansion. The check valve is installed at the distal end of the capsule-type grout-stopping plug and connected to the outlet of a grouting pipe pre-embedded in the anchor cable body. The grouting pipe is a polyethylene hose with an inner diameter of 20 mm. The surface of the steel strand is wrapped with a peelable polyethylene sheath approximately 0.8 mm thick, covering the entire length of the steel strand. The sheath within approximately 8 m of the anchoring section has a rupture pressure set to a second set value; the sheath within approximately 10 m of the free section has a rupture pressure set higher than the second set value to ensure its integrity during grouting and tensioning. The fabricated anchor cable, along with the grouting pipe and grout-stopping components, was manually pushed through the casing to the bottom of the hole, with no obvious obstruction during the pushing process.

[0122] The grouting equipment uses a variable frequency speed-controlled grouting pump equipped with a pressure sensor and a flow meter. The pressure sensor is installed on the grouting pipe at the borehole opening. The grout is a modified cement-based grout, using 42.5 grade ordinary Portland cement with a water-cement ratio of 0.45. 0.03% triethanolamine by weight of the cement is added as an early-strength agent, and 10% UEA expansion agent by weight of the cement is added. The initial setting time of the grout, measured on-site, is approximately 1.5 hours.

[0123] First, clean water is injected into the capsule-type grout stopper through a dedicated pressurization pipeline. The pressure is stopped when it reaches 1.0 MPa, allowing the capsule to expand and fit tightly against the inner wall of the casing. The grouting pump is then started to begin grouting. The first setpoint, i.e., the target grouting pressure, is set to 2.0 MPa, and the preset flow rate threshold is 5 L / min. During grouting, the PLC controller collects pressure signals in real time and uses a PID algorithm to control the frequency converter to adjust the grouting pump motor speed, maintaining the bottom hole pressure within the range of 1.8 MPa to 2.2 MPa. After approximately 8 minutes of grouting, the pressure reaches 2.0 MPa, and the flow rate drops to approximately 4 L / min. At this point, grouting is stopped and pressure is maintained for 8 minutes. During the pressure maintenance period, a small amount of thick grout is observed returning from the borehole opening, indicating that this section of grouting is basically compacted. The grouting pressure reaches a maximum of 2.3 MPa during the pressure maintenance process, under which the peelable sheath outside the steel strand ruptures.

[0124] After the pressure holding period, the top of the casing was clamped using the drilling rig's lifting device and pulled upwards approximately 1.5m. The capsule-type grout stopper, relying on friction with the inner wall of the casing, was pulled up along with the casing, while the anchor cable remained stationary. The capsule was then re-pressurized at the new position to expand and seal, and the second stage of grouting was then performed. The grouting parameters were the same as the first stage. This cycle was repeated, with grouting performed for each stage of casing withdrawal, for a total of 6 stages of grouting, completing the grouting of the entire 8m anchoring section. Finally, the casing was completely withdrawn from the borehole. During the construction process, the grouting pressure and flow rate of each stage were controlled within the set range, with a cumulative grouting volume of approximately 320L.

[0125] Seven days after grouting was completed, the grout strength reached 28.5 MPa in tests conducted on test blocks cured under the same conditions, meeting the design requirements. Anchor cable tensioning was then carried out using an overall staged tensioning method, with the final tension force locked at 800 kN. After the exposed steel strands of the anchor were cut off, approximately 80 mm was retained, and the anchor head was sealed and protected with fine aggregate concrete.

[0126] In this embodiment, the casing drilling process proceeded smoothly without any hole collapse or drill bit jamming, and the casing wall protection effect was good. During the segmented grouting process, the capsule-type grout stop plugs provided reliable sealing, and the grouting pressure and volume in each segment were within the expected range, with no significant grout loss. After the anchor cable was tensioned and locked, testing showed that the grout fullness of the anchoring section basically met the requirements, and the overall construction quality of the anchor cable met the design requirements.

[0127] <Example 2>

[0128] This slope treatment project has the same general overview as Example 1. The slope height is approximately 35m, and the rock mass is strongly weathered granite with fractured rock and well-developed joints and fissures. The anchor cable design length is 18m, with an 8m anchorage section and a 10m free section, and a design tensile force of 800kN. This example, based on Example 1, further employs the aforementioned intelligent construction method for the entire construction and control process.

[0129] Before construction, a geological survey report for the area was collected, revealing a rock mass integrity coefficient of 0.32, a joint development level of 15 joints per cubic meter, and a permeability coefficient of 5 × 10⁻⁶. -4 cm / s. The above three geological parameters are input into a pre-constructed geological condition construction parameter association model. This model uses a BP neural network with 3 nodes in the input layer, 8 and 6 nodes in the two hidden layers respectively, and 4 nodes in the output layer. After the model runs, it automatically outputs the initial construction parameters: the first set value grouting pressure is 2.2 MPa, the preset flow rate threshold is 5 L / min, the first predetermined length of casing single pull-out length is 1.5 m, and the grout initial setting time control range is 1.5 hours. These parameters are automatically written into the construction control system.

[0130] After the drilling rig is in place, casing drilling begins, following the same process as in Example 1. Once the designed hole depth of 18m is reached, the casing is left inside the hole, and the drilling tools are removed. Anchor cable fabrication and placement are the same as in Example 1.

[0131] The grouting equipment uses a variable frequency speed-regulating grouting pump, equipped with a pressure sensor and an electromagnetic flow meter, with a sampling frequency set to 10 times per second. The grout is a modified cement-based grout with a water-cement ratio of 0.45, and contains 0.03% triethanolamine and 10% UEA expansion agent. The measured initial setting time is approximately 1.5 hours.

[0132] First, the capsule-type grout stopper is pressurized to 1.0 MPa to expand and seal it. The grouting pump is started to begin the first stage of grouting, with a target pressure set at 2.2 MPa. During the grouting process, the control system collects pressure and flow rate data in real time and dynamically plots the PQ time-varying curve. About 2 minutes after the start of grouting, the pressure fluctuates between 0.4 MPa and 0.6 MPa, and the flow rate remains between 25 L / min and 30 L / min without a significant upward trend. Based on the preset discrimination rules, the control system determines that the current section is a severe grout leakage type. The system automatically executes the first grouting strategy, lowering the target pressure to 1.4 MPa, and simultaneously adding water glass to the grout through the auxiliary injection device to shorten the grout gel time to about 40 seconds. After adjustment, grouting continues for about 5 minutes, with the pressure gradually rising to 1.4 MPa and the flow rate decreasing to about 4 L / min. Grouting is then stopped and pressure is maintained for 8 minutes. During the pressure maintenance period, a small amount of thick grout returns from the wellhead.

[0133] After the pressure holding period, the casing was pulled upwards by 1.5m. The capsule was then repressurized and sealed as the casing was lifted, and the second stage of grouting began. After the start of this stage of grouting, the pressure rose steadily at a rate of approximately 0.2MPa / min, while the flow rate decreased synchronously. The control system determined this to be a micro-fracture permeation type and implemented the second grouting strategy, increasing the target pressure to 2.6MPa and extending the pressure holding time to 12 minutes. Approximately 7 minutes into the grouting process, the pressure reached 2.6MPa, and the flow rate dropped to 3.5L / min. Grouting was then stopped and pressure held for 12 minutes. When the pressure rose to around 2.5MPa, the peelable sheath within the anchoring section ruptured, allowing grout to enter the sheath and directly contact the steel strands.

[0134] During subsequent grouting stages, the control system executed corresponding strategies based on the real-time PQ curve characteristics. A total of six grouting stages were performed throughout the borehole, with a cumulative grouting volume of approximately 340L. After each stage of grouting was completed, the control system automatically recorded the final grouting parameters and fracture identification results for each stage. This included: the first stage was identified as a severe leakage type (actual grouting pressure 1.4MPa, grouting volume 65L); the second stage was identified as a micro-fracture permeability type (actual grouting pressure 2.6MPa, grouting volume 58L); and two of the third to sixth stages were identified as micro-fracture types, and two as dense types. All records were stored in the database as the borehole's quality archive.

[0135] Seven days after grouting was completed, the anchor cables were tensioned to a locked tonnage of 800 kN. After tensioning, non-destructive testing was performed on the anchor cables, using the acoustic reflection method to obtain anchorage quality indicators. The test results showed that the grouting fullness of the anchorage section was 92%, and the wave velocity anomaly index of the anchorage section was 0.15, indicating good anchorage quality.

[0136] The actual geological parameters of the borehole, the grouting parameters of each section during construction, the fracture identification results, and the non-destructive testing results were combined into a new sample and added to the sample database. The sample database maintained by the system stores construction data for the most recent 200 anchor cable boreholes. That same night, the system automatically retrained the anchorage quality prediction model based on the updated sample database. The trained model had a prediction error of 7.2% on the reserved test set.

[0137] Simultaneously, a digital twin model was constructed based on the actual construction data of the borehole. Geological exploration data, borehole trajectory, grouting pressure and volume at each stage, fracture identification results, and non-destructive testing results were imported into the digital twin platform. A particle swarm optimization algorithm was used to invert and calibrate the rock mass permeability coefficient and fracture aperture. The algorithm parameters were set as follows: population size 30, 80 iterations, inertia weight decreasing from 0.9 to 0.4, learning factors c1 and c2 both set to 2.0, and the permeability coefficient search range 2.5 × 10⁻⁻⁻⁶. 4 cm / s to 1.0 × 10 -3 The speed was cm / s, and the crack aperture search range was 0.2 mm to 1.0 mm. After 62 iterations, the root mean square error of the objective function value decreased to 0.042, which was less than the convergence criterion of 0.05, and the iteration was stopped. The grouting fullness distribution simulated by the calibrated digital twin model was basically consistent with the measured results.

[0138] Before constructing the next adjacent anchor hole, the proposed construction parameters are input into the calibrated digital twin model for virtual pre-simulation. A two-stage optimization strategy is employed. In the first stage, orthogonal experiments are conducted with three grouting pressure levels (1.8 MPa, 2.2 MPa, and 2.6 MPa) and three grouting times (6 min, 8 min, and 10 min), constructing an L9 orthogonal array for nine virtual pre-simulations. Range analysis shows that grouting pressure has the most significant impact on grout fullness. In the second stage, a grid search is performed with grouting pressures ranging from 2.0 MPa to 2.4 MPa in 0.1 MPa increments, while the grouting time is fixed at 8 min. The pre-simulation results show that when the grouting pressure is 2.3 MPa, the predicted grout fullness is 91.5%, and the total grouting volume is approximately 325 L, meeting the constraint of a fullness of not less than 90% and with a relatively small grouting volume. These optimized parameters are automatically written into the construction control system to guide the actual construction of the next anchor hole.

[0139] After all anchor cable holes are constructed, the digital twin models of all holes are linked together in the construction sequence to form a complete digital archive of the slope support project. This archive includes the geological model, drilling trajectory, grouting process simulation, actual construction records, quality inspection results, and the final state model after inversion calibration for each hole, and is stored on a cloud server for later quality traceability and health monitoring.

[0140] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for rapid installation and grouting of prestressed anchor cables in strongly weathered and fractured rock masses, characterized in that, Includes the following steps: S1. Drilling with casing: Drilling is carried out using an eccentric casing drilling tool combination. During the drilling process, the casing is advanced synchronously. After drilling to the designed hole depth, the casing is left in the hole as a temporary protective wall. The bottom end of the casing is located at the bottom of the hole, and the top end is exposed at the hole opening. S2. Anchor cable insertion and pressure-bearing component installation: The prestressed anchor cable with a pressure-bearing grouting component is inserted into the casing insertion hole. A grouting pipe is pre-embedded on the prestressed anchor cable, and the outlet of the grouting pipe is located at the far end of the pressure-bearing grouting component. The pressure-bearing grouting component includes at least one expandable capsule-type grouting plug. S3. Segmented Pressure Controllable Grouting: S3a. Pressure medium is injected into the capsule-shaped grout stop plug through the grouting pipe, causing it to expand and tightly fit against the borehole wall or casing, forming a closed grouting zone; S3b. Pressure grouting is performed within the grouting zone, and the grouting pressure and flow rate are monitored in real time during the grouting process; S3c. When the grouting pressure reaches a first set value and the grouting flow rate drops below a preset threshold, grouting is stopped and pressure is maintained for a first predetermined time until grout returns to the borehole or the pressure maintenance time ends; The first set value and the first predetermined time are preset according to geological conditions and design requirements; S4. Segmented Removal and Repeated Grouting of the Casing: S4a. After the grout returns to the borehole or after the first predetermined time has elapsed, the casing is pulled out upwards for a first predetermined length to expose a new rock mass segment; S4b. Repeat step S3 to perform pressure grouting on the exposed new rock mass segment; S4c. Repeat steps S4a and S4b until the grouting of the entire anchoring section is completed, and finally the casing is completely removed from the borehole. S5. Tensioning and Anchoring: After the grout strength reaches the design requirements, the anchor cables are tensioned and locked, and finally the anchors are sealed.

2. The method for rapid installation and grouting of prestressed anchor cables suitable for strongly weathered fractured rock masses as described in claim 1, characterized in that, In step S1, the diameter of the eccentric drill bit in the eccentric casing assembly is smaller than the inner diameter of the casing, and high-pressure air or foam is injected into the bottom of the hole through the drill rod during drilling to cool the drill bit and carry away rock cuttings.

3. The method for rapid installation and grouting of prestressed anchor cables suitable for strongly weathered fractured rock masses as described in claim 1, characterized in that, In step S2, the pressure-bearing grout-stopping assembly further includes a check valve located at the distal end of the capsule-type grout-stopping plug, and the check valve is connected to the outlet of the grouting pipe; the steel strands of the prestressed anchor cable are wrapped with a peelable sheath, which ruptures when the grouting pressure reaches a second set value, and the second set value is greater than the first set value in step S3c.

4. The method for rapid installation and grouting of prestressed anchor cables suitable for strongly weathered fractured rock masses as described in claim 3, characterized in that, In step S3, the grout used for pressure grouting is a modified cement-based grout with added early strength agent and micro-expansion agent, and its initial setting time is controlled between 1 hour and 2 hours.

5. The method for rapid installation and grouting of prestressed anchor cables suitable for strongly weathered fractured rock masses as described in claim 3, characterized in that, In step S3, the pressure grouting adopts a dynamic pressure control mode. Based on the grout pressure feedback signal returned from the far end of the capsule-type grout stop plug, the grouting pressure is adjusted in real time to keep the grouting pressure within the range of 0.9 to 1.1 times the first set value until the grouting is completed.

6. The method for rapid installation and grouting of prestressed anchor cables suitable for strongly weathered fractured rock masses as described in claim 1, characterized in that, Before step S1, the process also includes step S0, which involves intelligent pre-matching and dynamic optimization of construction parameters: determining the rock mass integrity coefficient, joint development degree, and permeability coefficient based on the geological survey report; and calculating and outputting the first set value, preset threshold, first predetermined length, and initial setting time control range of the grout in step S3 for subsequent steps S3 and S4 through a pre-constructed geological condition-construction parameter correlation model, as the initial execution parameters for subsequent steps S3 and S4. During the construction processes in steps S3 and S4, the actual grouting pressure, flow rate change curves, and grouting volume data are collected and compared with the predicted curves of the geological conditions-construction parameter association model. When the deviation between the actual curve and the predicted curve exceeds a preset deviation threshold, the model correction program is triggered. The geological conditions-construction parameter association model is incrementally learned and updated based on the actual construction data, and the updated parameters are rewritten into the construction control system for subsequent anchor cable hole construction.

7. The method for rapid installation and grouting of prestressed anchor cables suitable for strongly weathered fractured rock masses as described in claim 1, characterized in that, The segmented pressure controllable grouting described in step S3 also includes the following intelligent adaptation steps: S3d. During the grouting process, the grouting pressure P and grouting flow rate Q are monitored in real time, and the time-varying curves of PQ are plotted. S3e. Based on the characteristic parameters of the PQ time-varying curve, determine the fracture development type of the rock mass in the current grouting section in real time; the fracture development type includes at least severe grout leakage type, microfracture permeability type, and dense type; S3f. Based on the identified fracture development type, dynamically adjust the grouting control parameters of the current grouting section; where: If the problem is identified as severe grout leakage, the grouting system is controlled to execute a first grouting strategy, which includes reducing the target grouting pressure setting value, and / or increasing the grout viscosity, and / or injecting a quick-setting material. If the grouting system is determined to be of the microcrack permeable type, the grouting system is controlled to execute a second grouting strategy, which includes increasing the target grouting pressure setpoint and / or extending the pressure holding time. If the grouting system is determined to be dense, the grouting system is controlled to execute a third grouting strategy, which includes switching to an intermittent grouting mode after the grouting pressure reaches the basic set value. S3g. Repeat steps S3d to S3f until the grouting stop condition for the current section is met, and record the final grouting parameters and judgment results for that section as a quality file.

8. The method for rapid installation and grouting of prestressed anchor cables suitable for strongly weathered fractured rock masses as described in claim 7, characterized in that, Following step S5, step S6, intelligent assessment of anchorage quality and parameter self-optimization, is also included: After completing the grouting construction of all anchor cable holes, at least some of the anchor cable holes are subjected to non-destructive testing to obtain anchorage quality indicators, which include at least the grouting fullness and the abnormal wave velocity index of the anchorage section. Collect the final grouting parameters and crack discrimination results recorded in step S3g during the construction of each anchor cable hole, and construct a sample dataset together with the anchoring quality index; Based on the sample dataset, an anchorage quality prediction model was trained, and a mapping relationship between construction parameters, crack type and anchorage quality was established. The anchoring quality prediction model is embedded into the geological condition-construction parameter correlation model to optimize the initial construction parameter settings for subsequent projects.

9. The method for rapid installation and grouting of prestressed anchor cables suitable for strongly weathered fractured rock masses as described in claim 8, characterized in that, Following step S6, the process also includes step S7: digital twin and virtual rehearsal of the construction process. During construction, based on geological survey data, real-time collected drilling parameters, grouting parameters, and fracture discrimination results recorded in step S3g, a digital twin model of the current anchor cable hole is constructed. The digital twin model includes the three-dimensional structure of the rock mass, the borehole trajectory, the grouting diffusion range, and the anchoring section morphology. The digital twin model is compared with the design model in real time to identify construction deviations and generate visual early warning information; the construction deviations include at least one of drilling deviation, grouting beyond the range, and insufficient filling; After the current anchor hole construction is completed, the digital twin model is inverted and calibrated based on the actual construction data of the hole and the obtained anchoring quality indicators to make it consistent with the final state of the physical anchor hole. The calibrated digital twin model is used as a virtual test platform. The proposed construction parameters for subsequent anchor holes are input to conduct virtual grouting simulation and predict the grouting diffusion range and anchoring quality under different construction parameter conditions. The construction parameters for subsequent anchor holes are optimized based on the results of the virtual simulation, and the optimized parameters are automatically written into the construction control system to guide the actual construction of subsequent anchor holes. The digital twin models of each anchor cable hole are linked together in the construction sequence to form a digital archive of the entire slope protection project's construction process, which can be used for long-term quality traceability and health monitoring.