A method for arranging broken surrounding rock anchor cables

Abstract

The application discloses a broken surrounding rock anchor cable densification arrangement method and relates to the technical field of tunnel construction.The method comprises the following steps: constructing a three-dimensional digital twin model of surrounding rock; identifying and extracting a three-dimensional space interface and thickness distribution of a broken surrounding rock zone; determining deep surrounding rock fixed nodes on the periphery of the broken zone and shallow surrounding rock fixed nodes in the inner periphery of the broken zone in the digital twin model, and generating a fixed node position set according to a long-short alternating topology rule; mapping the fixed node position set to a tunnel excavation contour surface to generate a comprehensive construction parameter set; and performing work in the entity engineering according to the comprehensive construction parameter set, sequentially through the processes of hole exploration and injection combination, instantaneous resin locking, ladder servo tensioning and hole jumping multi-stage grouting, so as to realize broken surrounding rock anchor cable densification arrangement and the like. The application solves the problem of construction difficulty when passing through broken surrounding rock in the existing tunnel construction process by analyzing the state of the broken surrounding rock and combining the construction process for the broken surrounding rock.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction technology, and specifically to a method for densely arranging anchor cables in fractured surrounding rock. Background Technology

[0002] In tunnel engineering, when encountering highly fractured, water-rich, and rheologically strong large-deformation surrounding rock (such as phyllite softened into mud), conventional ordinary mortar anchor bolts combined with initial support often fail to provide sufficient radial resistance, easily leading to severe convergence, encroachment, or even complete collapse of the surrounding rock. Therefore, prestressed anchor cables are commonly used in engineering to transform passive reinforcement into active reinforcement. However, existing anchor cable construction methods have the following serious technical defects:

[0003] First, the single spatial support structure makes it highly susceptible to overall shear collapse. Existing technologies generally use anchor cables of equal length arranged at equal intervals across the entire cross section, resulting in all anchor cables having their deep anchoring ends on a cylindrical surface at approximately the same depth. In extremely fractured strata, in-situ stress can easily cut out a huge, uniform, continuous sliding surface along this depth boundary. Once instability occurs, the entire surrounding rock will undergo overall shear failure, carrying all anchor cables with it.

[0004] Secondly, when the density of prestressed anchor cables is high, the drilling process faces serious problems of difficult hole formation and easy grout leakage. The extremely fractured surrounding rock will collapse when drilling and is very easy to get stuck, resulting in a very low hole formation rate of conventional drilling methods. At the same time, due to the significant reduction in the spacing between anchor cables, the internal fractures of the strata are intertwined, and during the high-pressure grouting in the later stage, it is very easy for serious grout leakage to occur between adjacent holes, surface grouting, or grout loss with groundwater, which makes it impossible for the anchor cables to achieve full-length consolidation.

[0005] Third, the time window and the load application mechanism are mismatched, resulting in delayed support and easy crushing of soft rock. Traditional cement mortar anchoring requires several days to consolidate before tensioning, during which time the soft rock has undergone tens of centimeters of drastic rheological changes; and because the surrounding rock is extremely soft, the huge concentrated load during tensioning can easily press the anchor plate directly into (punching failure) the interior of the surrounding rock, resulting in instantaneous loss of prestress. Summary of the Invention

[0006] This invention provides a method for densely arranging anchor cables in fractured surrounding rock to solve the aforementioned problems that exist when tunneling through fractured surrounding rock during tunnel construction.

[0007] A method for densely arranging anchor cables in fractured surrounding rock includes the following steps:

[0008] Step 1: Collect on-site geological exploration and monitoring data to construct a three-dimensional digital twin model of the surrounding rock;

[0009] Step 2: Identify and extract the three-dimensional spatial interface and thickness distribution of the loosened and fractured zone of the surrounding rock;

[0010] Step 3: In the digital twin model, determine the fixed nodes of the deep surrounding rock outside the fracture zone and the fixed nodes of the shallow surrounding rock inside the fracture zone, and generate a set of fixed node locations according to the topological rule of alternating long and short nodes.

[0011] Step 4: Map the fixed node location set to the tunnel excavation outline to generate a borehole location set, an anchor cable size parameter set, a tensioning parameter set, and a grouting parameter set, and merge them to form a comprehensive construction parameter set;

[0012] Step 5: Based on the comprehensive construction parameter set, the operation is carried out in the actual project. The anchor cable is densely arranged in the fractured surrounding rock through a combination of exploratory injection and hole formation, instantaneous resin locking, stepped servo tensioning and multi-stage skip-hole grouting process.

[0013] Furthermore, the specific method for identifying the loosening and fracture zone of the surrounding rock is as follows: identify the depth of the plastic zone of the surrounding rock, define this depth as the three-dimensional spatial interface of the loosening and fracture zone of the surrounding rock, and extract the thickness limit value of the fracture zone of the current analysis section.

[0014] Furthermore, the steps of determining fixed nodes and generating a set of fixed node locations include:

[0015] The depth of the fixed node in the deep surrounding rock is defined as greater than the thickness limit of the fracture zone;

[0016] The depth of the shallow surrounding rock fixed node is defined as less than the thickness limit value of the fracture zone;

[0017] The deep surrounding rock fixing nodes and the shallow surrounding rock fixing nodes are arranged in a quincunx pattern in three-dimensional space at a 1:1 ratio to form a sawtooth discontinuous anchoring boundary that eliminates the continuous shear slip surface.

[0018] Furthermore, the longitudinal and circumferential spacing of the borehole location set is subject to the following boundary constraints and is solved: longitudinal spacing constraint: extract the steel arch spacing of the initial tunnel support in the digital twin model, set the longitudinal spacing of the borehole location set to be an integer multiple of the steel arch spacing, so that the anchor cable orifice pad and the steel arch form a nodal force coupling; circumferential spacing constraint: set the circumferential spacing of adjacent borehole locations, so that after the adjacent long and short anchor cables apply working loads below their orifice pads, the compressive stress diffusion cones generated in the rock mass of the surrounding rock interpenetrate and overlap in the shallow surrounding rock, forming a continuous three-dimensional compressive compaction arch.

[0019] Furthermore, the process of drilling based on the set of drilling locations includes: real-time monitoring of the torque and wind pressure parameters of the drilling equipment; if it is found that a strongly fractured, muddy, or collapsed stratum is encountered, making it impossible to drill a hole in one go, the drill rod is withdrawn, and the artificial hole wall is reshaped by injecting a fast-setting slurry into the original hole; after the artificial hole wall reaches the initial setting strength, in-situ secondary drilling is carried out until the hole depth set by the set of construction parameters is reached.

[0020] Furthermore, the installation of the anchor cable includes the following steps: the anchor cable, together with the quick-setting resin anchoring agent cartridge, is fed into the bottom of the borehole, the resin anchoring agent cartridge is crushed, and after the resin has cured within the set time window, the rigid locking of the anchoring end of the anchor cable to the surrounding rock of the fixed node is completed.

[0021] Furthermore, the installation of anchor cables also includes the following steps: grouting is carried out step by step according to the hole positions, from low hole positions to high hole positions, with intervals between holes. The grouting material is ultra-fast hardening dual-liquid inorganic grouting material, and a grout stop plug and a water-absorbing expansion grout stop strip are set outside the grouting hole for secondary sealing and fastening to prevent surface grouting and grout cross-linking between adjacent holes during high-density mesh high-pressure grouting.

[0022] Furthermore, the grouting operation is divided into three dynamic pressure control stages: the initial stage uses 0.5~1.0MPa to inject dual-liquid grout; the pressure stabilization and penetration stage raises the pressure to 1.5MPa and stabilizes it for a set time, forcing the dual-liquid grout to penetrate into the fractured surrounding rock mass fissures around the anchor cable; the splitting final pressure stage raises the pressure in stages to the designed final pressure of 2.0MPa. When the grouting pressure reaches 2.0MPa and the grout injection volume meets the single-pipe design grouting volume requirements, the pressure is maintained for no less than 20 minutes before the grouting is terminated.

[0023] Furthermore, the steps for anchoring the cable using the tension parameter set include: first, applying a tension force of 10% to 20% of the target working load for initial pre-tightening and straightening; then, dividing the target working load into at least three steps and applying them sequentially. Except for the highest step, each step must be stabilized for at least 5 minutes to release the transient stress of the surrounding rock; after reaching the highest step of the target working load, the pressure is stabilized for at least 15 minutes to forcibly absorb the creep deformation of the surrounding rock, and the anchor is locked after the stress gauge stabilizes.

[0024] Furthermore, the anchor cable includes an anchor cable rod body with a hollow grouting channel and outer steel strands, the core of which is a continuous rigid metal tube, and the outer layer of the rigid metal tube is provided with 8 prestressed steel wires; the step of crushing the medicated cartridge includes: connecting a driver to the tail end of the anchor cable, using the driver to output rotational torque, the rotational torque being transmitted to the bottom of the hole through the continuous rigid metal tube in the core, driving the end of the anchor cable to rotate continuously at a set speed, thereby fully crushing and mixing the resin anchoring agent cartridge.

[0025] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:

[0026] 1. An anchor cable layout scheme different from the traditional full-length equidistant arrangement is adopted. Using the constructed digital twin model, based on the state of the surrounding rock, deep surrounding rock is used for suspension and fixation, and shallow surrounding rock is used for shallow compaction. Long and short anchor cables are alternately and arranged in a quincunx pattern to construct a sawtooth discontinuous anchoring boundary in the rock mass. This completely cuts off the generation path of the uniform shear sliding surface. At the same time, the parameter calculation constrained by the circumferential spacing ensures that the compressive stress diffusion cones of adjacent long and short anchor cables intersect and overlap in the shallow layer. This rigidly reshapes the loose surrounding rock into a three-dimensional compressive continuous composite arch with high strength, avoiding the risk of instability of the surrounding rock.

[0027] 2. The generated set of fixed node positions is mapped to the tunnel excavation outline to generate a set of borehole positions. During construction, when a borehole collapse occurs, the artificial borehole wall is reshaped by injecting fast-setting grout into the original hole and re-drilling in situ, which solves the problem of difficult borehole formation in extremely fractured surrounding rock. In the grouting stage, a three-stage pressurization process of low to high pressure, intermittent skipping holes and ultra-fast hard double liquid grout is adopted. The physical sealing of the fast-setting grout injected into the first hole blocks the connecting fractures, avoiding the phenomenon of grout overflow and grout cross-contamination in adjacent holes caused by high-pressure grouting under high-density hole network, thus ensuring the consolidation quality of the entire length.

[0028] 3. The instantaneous resin locking process is adopted to achieve instantaneous rigid locking of the anchor cable end within a very short time window after excavation. Combined with the stepped servo tensioning process, it provides a buffer time for the fractured soft rock to reconsolidate. This not only absorbs the transient creep deformation of the soft rock and prevents the loss of prestress, but also achieves joint force coupling at the nodes by binding the longitudinal hole spacing with the steel arch frame row spacing, effectively avoiding the punching and shearing damage of the shallow soft rock by the high-strength prestress.

[0029] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.

[0030] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0031] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0032] Figure 1 This is a flowchart of the method for densely arranging anchor cables in fractured surrounding rock, as disclosed in an embodiment of the present invention. Detailed Implementation

[0033] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0034] In existing tunnel construction schemes, when traversing extremely fractured surrounding rock zones, especially phyllite slate, which is extremely thin-layered, severely wrinkled in some areas, and partially strongly altered, exhibiting a muddy texture, with well-developed steep-dipping joints and fissures, fractured rock mass, and interlayer mud inclusions, groundwater flows out linearly along drainage holes. The surrounding rock of the tunnel chamber is fragmented, with extremely poor integrity and stability, frequent small-scale collapses and rockfalls, and turbid groundwater flowing out linearly on both sides. These areas are water-rich zones, and during construction, they are prone to severe rheological changes and loosening pressure. Monitoring data from actual construction sites shows that the daily convergence can reach 35-36 mm. However, existing anchor cable construction methods, which use equal-length anchor cables with equal spacing across the entire cross-section, are prone to continuous sliding surfaces in extremely fractured surrounding rock zones due to their density and anchoring positions, leading to the risk of instability. Therefore, this invention proposes a scheme to determine the anchor cable density and location based on the actual state of the surrounding rock. This scheme is described in detail below:

[0035] Figure 1 A method for densely arranging anchor cables in fractured surrounding rock is shown, including the following steps:

[0036] Step 1: Collect on-site geological exploration and monitoring data to construct a three-dimensional digital twin model of the surrounding rock.

[0037] Step 2: Identify and extract the three-dimensional spatial interface and thickness distribution of the loosened and fractured zone of the surrounding rock.

[0038] The specific method for identifying the loosening and fracture zone of the surrounding rock is as follows: identify the depth of the plastic zone of the surrounding rock, define this depth as the three-dimensional spatial interface of the loosening and fracture zone of the surrounding rock, and extract the thickness limit value of the fracture zone of the current analysis section.

[0039] Step 3: In the digital twin model, determine the fixed nodes of the deep surrounding rock outside the fracture zone and the fixed nodes of the shallow surrounding rock inside the fracture zone, and generate a set of fixed node locations according to the topological rule of alternating long and short nodes.

[0040] The aforementioned set of fixed node locations is used to determine the installation positions of anchor cables of different lengths, starting from the tunnel excavation outline. By using anchor cables of different lengths, a high-density grid structure is formed, which will reshape the originally loose, muddy, and extremely fragmented rock mass into a whole structure with self-bearing capacity.

[0041] Among them, the anchor cables connected to the fixed nodes in the deep surrounding rock serve a suspension function, achieving deep anchoring. They are generally selected from stable surrounding rock, suspending unstable rock masses in fractured or loosened zones onto stable rock masses at a deeper level to prevent rockfalls and collapses. The anchor cables connected to the fixed nodes in the shallow surrounding rock serve a compression reinforcement and composite arch function. By applying prestress to the surface of the surrounding rock, crisscrossing compressive stress overlap zones are formed within the rock mass. This tightly compresses the loose rock fragments together, dramatically increasing friction and forming a continuous load-bearing composite arch of a certain thickness around the tunnel. The different lengths of the anchor cables also avoid the defect of forming a uniform shear slip surface at the anchorage end, improving the overall shear resistance.

[0042] The steps for determining fixed nodes and generating a set of fixed node locations include:

[0043] The depth of the fixed node in the deep surrounding rock is defined as greater than the thickness limit of the fracture zone;

[0044] The depth of the shallow surrounding rock fixed node is defined as less than the thickness limit value of the fracture zone;

[0045] The deep surrounding rock fixing nodes and the shallow surrounding rock fixing nodes are arranged in a quincunx pattern in three-dimensional space at a 1:1 ratio to form a sawtooth discontinuous anchoring boundary that eliminates the continuous shear slip surface.

[0046] The determination of the locations of fixed nodes in deep and shallow surrounding rock is explained in detail below.

[0047] Step 31, the process of determining the fixed nodes in the deep surrounding rock is as follows:

[0048] Step 311: Determine the initial boundary. In the digital twin model, take the thickness limit value L of the rupture zone in step 2 as the benchmark and extend it to a certain depth, such as 1.2L~1.5L, as a candidate fixed area.

[0049] Step 312: Apply virtual pull-out load by applying a virtual pull-out force F along the anchor cable axis on the three-dimensional mesh nodes within the candidate region.

[0050] Step 313: Monitor the displacement vector of the node under the action of F and the expansion of the plastic zone of the surrounding rock mass;

[0051] Step 314: If the displacement vector tends to be stable, its rate of change is less than the preset threshold, and the node does not induce new plastic dissipation energy, then the location is determined to be a stable area where no settlement displacement occurs, and its three-dimensional coordinates are recorded as a fixed node in the deep surrounding rock.

[0052] Step 315: If the displacement vector is unstable and its rate of change is greater than a preset threshold, then the location is determined to be in a disturbance zone or a weak interlayer. Continue to increase the radial depth for iterative calculation until the requirements of step 314 are met.

[0053] Step 32, the process of determining the fixed nodes in the shallow surrounding rock is as follows:

[0054] Step 321: Set candidate nodes inside the fracture zone, set initial shallow candidate nodes, and simulate the compressive stress field transmitted from the orifice plate to the rock mass after the tension force is applied. The stress field diffuses in a cone shape in the simulation model.

[0055] Step 322: Extract the overlapping area in space of the compressive stress diffusion cones generated between adjacent candidate nodes, and calculate the overlap ratio of the three-dimensional compression zone;

[0056] Step 323: Calculate the equivalent confining pressure in the overlapping area through simulation analysis, and determine whether the confining pressure is sufficient to reshape the originally loose rock mass into an integral structure with self-bearing capacity.

[0057] Step 324: If the stress field fails to achieve continuous coverage, adjust the radial depth of the shallow nodes or reduce the circumferential and longitudinal spacing of the anchor cables through the digital twin model; if the resulting compressive stress overlap zone can completely cover the fractured rock mass within the analysis section, then the current parameters are determined to be optimal.

[0058] Step 325: Locate the spatial position that meets the strength requirements of the composite arch, record its three-dimensional coordinates, and mark it as the shallow surrounding rock fixed node.

[0059] Step 4: Map the fixed node location set to the tunnel excavation outline to generate a borehole location set, an anchor cable size parameter set, a tensioning parameter set, and a grouting parameter set, and merge them to form a comprehensive construction parameter set.

[0060] The longitudinal and circumferential spacing of the borehole location set is subject to the following boundary constraints and is solved. The longitudinal spacing constraint is as follows: the spacing of the steel arch frame of the initial support of the tunnel is extracted from the digital twin model, and the longitudinal spacing of the borehole location set is set to be an integer multiple of the steel arch frame spacing, so that the anchor cable hole plate and the steel arch frame form a nodal force coupling. The circumferential spacing constraint is as follows: the circumferential spacing of adjacent borehole locations is set so that after the adjacent long and short anchor cables apply working loads below their hole plates, the compressive stress diffusion cones generated in the rock mass of the surrounding rock interpenetrate and overlap in the shallow surrounding rock, forming a continuous three-dimensional compressive compaction arch.

[0061] The anchor cable orifice plate and the steel arch frame form a nodal force coupling to adapt to the characteristics of extremely fractured rock masses, such as phyllite slate, where the rock surface is often relatively soft. When a large tension force, such as more than 150kN, is applied to the anchor cable, the anchor cable tray is prone to directly sinking into the rock mass or breaking the shallow shotcrete, resulting in loss of prestress. By forming a nodal force coupling with the steel arch frame, the steel arch frame can be used as an enlarged foundation to share the force and improve the overall stability.

[0062] Step 5: Based on the comprehensive construction parameter set, the operation is carried out in the actual project. The anchor cable is densely arranged in the fractured surrounding rock through a combination of exploratory injection and hole formation, instantaneous resin locking, stepped servo tensioning and multi-stage skip-hole grouting process.

[0063] Step 51, the exploration and injection combined hole-forming process includes:

[0064] Step 511: Monitor the torque and air pressure parameters of the drilling rig in real time;

[0065] Step 512: If it is identified that a strongly fractured, muddy, or collapsed formation is encountered, making it impossible to form a hole in one go, the drill pipe is removed, and the artificial hole wall is reshaped by injecting a rapidly solidifying slurry through the original hole.

[0066] Step 513: After the artificial borehole wall reaches its initial setting strength, perform in-situ secondary drilling until the borehole depth is reached as set by the construction parameter set.

[0067] Step 52, the instantaneous resin locking process includes the following steps:

[0068] Step 521: Send the anchor cable, along with the quick-setting resin anchoring agent cartridge, into the bottom of the borehole;

[0069] Step 522: Crush the resin anchoring agent roll;

[0070] Step 523: After the resin has cured within the set time window, the rigid locking between the anchoring end of the anchor cable and the surrounding rock of the fixed node is completed.

[0071] The anchor cable includes an anchor cable rod with a hollow grouting channel and outer steel strands. Its core is a continuous rigid metal tube, and the outer layer of the rigid metal tube is provided with 8 prestressed steel wires. The step of crushing the medicated cartridge includes: connecting a driver to the tail end of the anchor cable, using the driver to output rotational torque, and the rotational torque is transmitted to the bottom of the hole through the continuous rigid metal tube in the core, driving the end of the anchor cable to rotate continuously at a set speed, thereby fully crushing and mixing the resin anchoring agent cartridge.

[0072] After completing step 52, immediately proceed to step 53. The stepped servo tensioning process includes the following steps:

[0073] Step 531: First, apply a tension force of 10% to 20% of the target working load for initial pre-tightening and straightening;

[0074] Step 532: The target working load is then divided into at least three steps and applied sequentially. Except for the highest step, each step must be stabilized for at least 5 minutes to release the transient stress of the surrounding rock.

[0075] Step 533: After reaching the highest step target working load, maintain pressure stabilization for no less than 15 minutes to forcibly absorb the creep deformation of the surrounding rock, and then perform anchor cable locking after the stress dial stabilizes.

[0076] After completing step 53, immediately proceed to step 54. The skip-hole multi-stage grouting process includes the following steps: grouting is carried out step by step according to the hole position, from low hole position to high hole position, with skip-holes at intervals. The grouting material is an ultra-fast hardening dual-liquid inorganic grouting material, which generally sets in 30~120s. A grout stop plug and a water-absorbing expansion grout stop strip are set outside the grouting hole for secondary sealing and fastening to prevent surface grouting and grout cross-linking between adjacent holes during high-density mesh high-pressure grouting.

[0077] Specifically, the grouting operation is divided into three dynamic pressure control stages:

[0078] 1. In the initial stage, a two-component slurry is injected at a pressure of 0.5~1.0MPa.

[0079] 2. During the pressure stabilization and penetration stage, the pressure is increased to 1.5MPa and stabilized for a set time, forcing the dual-liquid grout to penetrate into the fractured rock mass around the anchor cable.

[0080] 3. During the final pressure stage of splitting, the pressure is gradually increased to the design final pressure of 2.0 MPa. When the grouting pressure reaches 2.0 MPa and the grouting volume meets the design grouting volume requirements for a single pipe, the grouting is stopped after maintaining the pressure for no less than 20 minutes.

[0081] Traditional cement mortar anchoring requires several days to reach the design strength for tensioning. However, in large-deformation phyllite, the tunnel may have already contracted and deformed by tens of centimeters or even collapsed within a few days. Therefore, in step 52 above, the characteristic of resin anchoring agent to solidify in a short time, generally 41 to 90 seconds, is used to rigidly lock the anchoring end of the anchor cable to the surrounding rock at the fixed node. At the same time, the tension force applied immediately in step 53 is executed to quickly curb the deformation of the surrounding rock. The surrounding rock is forcibly locked at the beginning of loosening to prevent further changes. The subsequent grouting, with the grout spreading along the extremely thin layered joints, bonds the anchor cable to the rock mass along its entire length, transforming the instantaneous main force into long-term rigid support.

[0082] During this process, due to the use of dense deployment and drilling in extremely fractured surrounding rock, the drill bit is prone to getting stuck and the hole to collapse under the scouring of groundwater. After the drill bit is pulled out, the hole closes instantly, making it impossible to insert the anchor cable. In response, this solution proposes the exploratory grouting combined with hole forming process in step 51. In addition, this process can also prevent the grout from entering the adjacent hole along the cracks when high-pressure grouting is performed on one hole in step 54, thereby improving the construction quality of the dense anchor bolts.

[0083] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process may be rearranged without departing from the scope of this disclosure. The appended method claims provide elements of various steps in an exemplary order and are not intended to limit the scope to the specific order or hierarchy described.

[0084] In the detailed description above, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features in a single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, with each claim representing a separate preferred embodiment of the invention.

[0085] Those skilled in the art will also understand that the various illustrative logic blocks, modules, circuits, and algorithm steps described in conjunction with the embodiments herein can be implemented as electronic hardware, computer software, or a combination thereof. To clearly illustrate the interchangeability between hardware and software, the various illustrative components, blocks, modules, circuits, and steps described above are generally described in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. Those skilled in the art can implement the described functionality in alternative ways for each specific application; however, such implementation decisions should not be construed as departing from the scope of this disclosure.

[0086] The steps of the methods or algorithms described in conjunction with the embodiments herein can be directly embodied in hardware, software modules executed by a processor, or a combination thereof. The software modules can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium well known in the art. An exemplary storage medium is connected to the processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and storage medium can reside in an ASIC. The ASIC can reside in a user terminal. Alternatively, the processor and storage medium can exist as discrete components in the user terminal.

[0087] For software implementation, the techniques described in this application can be implemented using modules (e.g., procedures, functions, etc.) that perform the functions described in this application. This software code can be stored in memory units and executed by a processor. The memory units can be implemented within the processor or outside the processor; in the latter case, they are communicatively coupled to the processor via various means, as is well known in the art.

[0088] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments, but those skilled in the art will recognize that the various embodiments can be further combined and arranged. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims. Furthermore, the term "comprising" as used in the specification or claims is interpreted in a manner similar to the term "including," as interpreted when used as a conjunction in the claims. Additionally, the use of any term "or" in the specification of the claims is intended to mean "non-exclusive or."

Claims

1. A method for densely arranging anchor cables in fractured surrounding rock, characterized in that, Includes the following steps: Collect on-site geological exploration and monitoring data to construct a three-dimensional digital twin model of the surrounding rock; Identify and extract the three-dimensional spatial interface and thickness distribution of the loosened fracture zone in the surrounding rock; In the digital twin model, the fixed nodes of the deep surrounding rock outside the fracture zone and the fixed nodes of the shallow surrounding rock inside the fracture zone are determined, and the set of fixed node locations is generated according to the topological rule of alternating long and short nodes. The fixed node location set is mapped to the tunnel excavation outline to generate a borehole location set, an anchor cable size parameter set, a tensioning parameter set, and a grouting parameter set, which are then merged to form a comprehensive construction parameter set. Based on the comprehensive set of construction parameters, the operation is carried out in the actual project. The process involves a combination of exploratory injection and hole formation, instantaneous resin locking, stepped servo tensioning, and multi-stage grouting with skip-holes to achieve a denser arrangement of anchor cables in the fractured surrounding rock.

2. The method as described in claim 1, characterized in that, The specific method for identifying the loosening and fracture zone of the surrounding rock is as follows: identify the depth of the plastic zone of the surrounding rock, define this depth as the three-dimensional spatial interface of the loosening and fracture zone of the surrounding rock, and extract the thickness limit value of the fracture zone of the current analysis section.

3. The method as described in claim 2, characterized in that, The steps for determining fixed nodes and generating a set of fixed node locations include: The depth of the fixed node in the deep surrounding rock is defined as greater than the thickness limit of the fracture zone; The depth of the shallow surrounding rock fixed node is defined as less than the thickness limit value of the fracture zone; The deep surrounding rock fixing nodes and the shallow surrounding rock fixing nodes are arranged in a quincunx pattern in three-dimensional space at a 1:1 ratio to form a sawtooth discontinuous anchoring boundary that eliminates the continuous shear slip surface.

4. The method as described in claim 1, characterized in that, The longitudinal and circumferential spacing of the borehole location set is subject to the following boundary constraints and is solved. The longitudinal spacing constraint is as follows: the spacing of the steel arch frame of the initial support of the tunnel is extracted from the digital twin model, and the longitudinal spacing of the borehole location set is set to be an integer multiple of the steel arch frame spacing, so that the anchor cable hole plate and the steel arch frame form a nodal force coupling. The circumferential spacing constraint is as follows: the circumferential spacing of adjacent borehole locations is set so that after the adjacent long and short anchor cables apply working loads below their hole plates, the compressive stress diffusion cones generated in the rock mass of the surrounding rock interpenetrate and overlap in the shallow surrounding rock, forming a continuous three-dimensional compressive compaction arch.

5. The method as described in claim 1, characterized in that, The exploration-injection combined drilling process includes: real-time monitoring of the torque and air pressure parameters of the drilling equipment; if it is found that the formation is strongly fractured, muddy, or collapsed, making it impossible to drill a hole in one go, the drill rod is withdrawn, and the artificial hole wall is reshaped by injecting fast-setting slurry into the original hole; after the artificial hole wall reaches the initial setting strength, in-situ secondary drilling is carried out until the hole depth set by the construction parameter set is reached.

6. The method as described in claim 5, characterized in that, The instantaneous resin locking process includes the following steps: the anchor cable and the rapid resin anchoring agent cartridge are fed into the bottom of the borehole, the resin anchoring agent cartridge is crushed, and after the resin has cured within the set time window, the rigid locking between the anchoring end of the anchor cable and the surrounding rock of the fixed node is completed.

7. The method as described in claim 6, characterized in that, The anchor cable includes an anchor cable rod with a hollow grouting channel and outer steel strands. Its core is a continuous rigid metal tube, and the outer layer of the rigid metal tube is provided with 8 prestressed steel wires. The step of crushing the medicated cartridge includes: connecting a driver to the tail end of the anchor cable, using the driver to output rotational torque, and the rotational torque is transmitted to the bottom of the hole through the continuous rigid metal tube in the core, driving the end of the anchor cable to rotate continuously at a set speed, thereby fully crushing and mixing the resin anchoring agent cartridge.

8. The method as described in claim 6, characterized in that, The stepped servo tensioning process includes the following steps: First, apply a tension force of 10% to 20% of the target working load for initial pre-tightening and straightening; then, divide the target working load into at least three stepped levels and apply them sequentially. Except for the highest level, each step level must be stabilized for at least 5 minutes to release the transient stress of the surrounding rock; after reaching the highest step target working load, stabilize the pressure for at least 15 minutes to forcibly absorb the creep deformation of the surrounding rock, and lock the anchor cable after the stress dial stabilizes.

9. The method as described in claim 6, characterized in that, The skip-hole multi-stage grouting process includes the following steps: grouting is carried out step by step according to the hole position, from low hole position to high hole position, with skip-holes at intervals. The grouting material is ultra-fast hardening dual-liquid inorganic grouting material. A grout stop plug and a water-absorbing expansion grout stop strip are set on the outside of the grouting hole for secondary sealing and fastening to prevent surface grouting and grout cross-linking between adjacent holes during high-density mesh high-pressure grouting.

10. The method as described in claim 9, characterized in that, The grouting operation is divided into three dynamic pressure control stages: the initial stage uses 0.5~1.0MPa to inject dual-liquid grout; the pressure stabilization and penetration stage raises the pressure to 1.5MPa and stabilizes it for a set time, forcing the dual-liquid grout to penetrate into the fractured rock mass around the anchor cable; the splitting and final pressure stage raises the pressure in stages to the design final pressure of 2.0MPa. When the grouting pressure reaches 2.0MPa and the grouting volume meets the design grouting volume requirements of a single pipe, the pressure is maintained for no less than 20 minutes before the grouting is ended.

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