Integrated graded rigidity-adjustable reducing anchor cable system and method

Abstract

The invention discloses an integrated graded rigidity-adjustable variable-diameter anchor cable system and method, and belongs to the technical field of mine and underground engineering supporting, and the system is characterized in that a hollow anchor cable rod body sequentially comprises a first equal-diameter section, a variable-diameter section, a second equal-diameter section and an exposed tensioning section from left to right; the diameter of the variable-diameter section is gradually reduced from the large-diameter end to the small-diameter end in a continuous manner, and the large-diameter end and the small-diameter end of the variable-diameter section are coaxially connected with the first equal-diameter section and the second equal-diameter section respectively; a slurry outlet I is formed in the side surface of the right part of the reducing section; the stop-grouting plug sleeves the left end of the second equal-diameter section; the tray is arranged outside the exposed tensioning section in a sliding and sleeving manner; the lock is arranged outside the exposed tensioning section in a sleeving mode and located on the right side of the tray; and the resin anchoring agent is adhered to the outer side of the first equal-diameter section. The method comprises the following steps: drilling and anchoring; anchor cable installation and initial pre-tightening; surrounding rock deformation monitoring and rigidity demand decision making; controllable grouting based on rigidity adaptation is carried out; and stable supporting based on graded rigidity. The corresponding supporting rigidity can be adjusted in a graded mode according to the surrounding rock deformation stage.

Description

Technical Field

[0001] This invention belongs to the field of support technology for mines and underground engineering, and specifically relates to an integrated variable diameter anchor cable system and method with adjustable stiffness in stages. Background Technology

[0002] As the depth of mineral resource mining continues to increase, the "three highs and one disturbance" environment (high ground stress, high osmotic pressure, high temperature, and intense mining disturbance) in tunnel engineering becomes increasingly severe, especially in deep soft rock tunnels, which exhibit significant large deformation, strong rheology, and difficult support characteristics. Under such complex geological conditions, traditional rigid support systems often fail prematurely due to their inability to adapt to the drastic early deformation of the surrounding rock; while simple flexible support cannot provide sufficient restraint after the surrounding rock deformation stabilizes, and cannot effectively prevent the continuous loosening of the surrounding rock.

[0003] Therefore, an ideal support element should possess intelligent characteristics of "flexibility followed by rigidity" or "adjustable stiffness." Specifically, during the intense deformation phase after tunnel excavation, it can release the energy accumulated in the surrounding rock by appropriately "yielding pressure," avoiding damage due to overload. Once the surrounding rock deformation enters a decay and stabilization phase, the support element can transform into a high-rigidity state, providing strong long-term support for the tunnel, thus achieving adaptive support throughout the entire life cycle of the tunnel. Developing such adjustable intelligent support technology has become a key research direction for the safe and efficient support of deep tunnels.

[0004] Currently, there are two main technical approaches to achieving anchor bolt / cable stiffness adjustment or pressure relief functions. One approach involves connecting a mechanical pressure relief device, such as a constant resistance device or pressure relief tube, at the tail of the bolt. This technology relies on structural sliding friction or component plastic deformation to dissipate energy; however, its pressure relief threshold and stroke are usually fixed at the factory and cannot be adjusted based on actual roadway deformation after installation. Furthermore, the external structure increases weak points in the connection, raising concerns about long-term reliability. The other approach is full-length bonded anchor bolts, whose stiffness is permanently fixed after grouting and offers no adjustability. Although some studies have attempted to adjust support stiffness by changing the properties of the grouting material or using segmented grouting, these methods generally suffer from complex processes, discontinuous adjustments, or irreversibility.

[0005] Overall, existing technologies either rely on complex and expensive mechanical moving parts or lack stiffness adjustment capabilities altogether, making it difficult to meet the differentiated and precise requirements for support stiffness during the dynamic evolution of surrounding rock in roadways while ensuring economy and reliability. Therefore, there is a current lack of a simple, reliable solution with a clear adjustment strategy and cost-effectiveness. To overcome these shortcomings, there is an urgent need for a system and method that is simple in structure, easy to construct, cost-controllable, and has a clear adjustment strategy to achieve effective control of support stiffness. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides an integrated, graded, adjustable stiffness variable-diameter anchor cable system and method. This method, with its simple structure and high reliability, enables the anchor cable support stiffness to be adjusted in stages according to the deformation of the surrounding rock, achieving an intelligent transition from active pressure relief to strong support. This provides an innovative and practical solution for complex and challenging roadways. The system is simple in structure, low in manufacturing cost, and convenient in adjustment. The support stiffness can be actively adjusted later according to the actual roadway conditions, significantly improving the adaptability, reliability, and economy of the support system.

[0007] To achieve the above objectives, the present invention provides an integrated graded adjustable stiffness variable diameter anchor cable system, including a hollow anchor cable rod, a grout stop plug, a tray, a lock and a resin anchoring agent, wherein a grouting channel is provided at the axis of the hollow anchor cable rod. The hollow anchor rod consists of, from left to right, a first equal-diameter section, a variable-diameter section, a second equal-diameter section, and an exposed tensioning section. The first and second equal-diameter sections have the same diameter, and their diameters are [missing information]. The diameter of the large diameter end of the variable diameter section and equal; The diameter of the variable diameter section gradually decreases from the large diameter end to the small diameter end in a continuous and uniform manner, and its large diameter end is coaxially connected to the first equal diameter section, and its small diameter end is coaxially connected to the second equal diameter section; at the same time, a grout outlet communicating with the grouting channel is opened on the right side of the variable diameter section. The grout stopper is fitted onto the left end of the second equal-diameter section; The tray slides onto the outside of the exposed tensioning section; The lock is threadedly fitted onto the outside of the exposed tensioning section and is located on the right side of the tray; The resin anchoring agent is bonded to the outer side of the first equal diameter segment.

[0008] In this invention, the grout outlet is positioned on the right side of the variable diameter section. This allows the injected grout to smoothly enter the annular gap between the variable diameter section and the borehole from the right end of the variable diameter section. Simultaneously, the grout preferentially diffuses inward from the right end of the variable diameter section, effectively preventing grout waste and interference with the resin anchoring section, thus providing a reliable process guarantee for achieving graded stiffness control. The grout stopper is fitted onto the left end of the second equal-diameter section, confining the grout within the smaller diameter end of the variable diameter section during grouting, effectively preventing grout leakage towards the borehole opening. Furthermore, the tapered geometry of the variable diameter section establishes a definite mathematical relationship between the grouting length and volume, providing sufficient flow space for the grout while ensuring the load-bearing strength of the rod itself. Furthermore, based on the synergistic effect of the installation position of the grout plug and the geometry of the variable diameter section, the position of the grout diffusion front can be precisely controlled through quantitative control of grout volume, stabilization of grout pressure, or control of grouting time. This allows for on-demand switching between three modes—low stiffness yielding, medium stiffness balance, and high stiffness strong support—by controlling the grouting length. It enables precise graded adjustment of support stiffness, perfectly matching the stiffness requirements of the surrounding rock throughout the entire process from severe deformation to stable convergence. This structural design provides an ideal execution platform for subsequently introducing real-time monitoring data, dynamically determining stiffness levels, and automatically executing grouting control, providing reliable technical support for intelligent adaptive support systems. This invention achieves stiffness adjustment through the integrated design of the variable diameter rod and adjustment mechanism, eliminating complex external mechanical components and requiring no additional moving parts. By adjusting the effective working length or stress state of the variable diameter section, the overall mechanical stiffness of the anchor cable system can be directly and gradedly changed.

[0009] This system features a simple structure, low manufacturing cost, and convenient adjustment. It can change the support stiffness not only by altering the locking position of the locks on the exposed tensioning section but also by adjusting the grouting length in the outer area of ​​the variable diameter section. It can provide corresponding levels of support stiffness based on the deformation of the surrounding rock in the roadway, allowing for proactive adjustment of the support stiffness according to the actual roadway conditions. This enables the locks to provide the required preload in the initial stage, and after reaching the set monitoring cycle, the support stiffness can be proactively adjusted according to the actual roadway conditions. This significantly improves the adaptability, reliability, and economy of the support system, providing an innovative variable stiffness support solution for complex and difficult roadways.

[0010] Furthermore, in order to provide sufficient flow space for the grouting slurry while avoiding insufficient local load-bearing capacity of the rod due to an excessively small diameter, the diameter of the small diameter end of the variable diameter section is... The range of values ​​is 70% to 90%, and not less than 14 mm.

[0011] Furthermore, in order to ensure that the stress in the variable diameter section transitions smoothly along the axial direction under the action of tensile load, so that the strength of the rod material can be fully utilized, the diameter variation law of the variable diameter section is as shown in formula (a). (a); In the formula, The variable diameter section in axial position The diameter at that point; This represents the rate of change in diameter. The axial coordinate is taken as the origin from the large diameter end of the variable diameter section.

[0012] Furthermore, in order to ensure the structural reliability and long-term stability during the graded stiffness adjustment process, the stress strength of the variable diameter section satisfies formula (b). (b); In the formula, To estimate the maximum axial tensile force; To estimate the maximum bending moment; The yield strength of the rod material; To consider the overall safety factor, .

[0013] Furthermore, in order to effectively prevent grout from leaking towards the orifice during the grouting process, the grout stop plug is made of water-swellable rubber or a highly elastic compression sealing material.

[0014] As a preferred embodiment, the distance between the slurry outlet and the small diameter end of the variable diameter section is in the range of 10~30 mm.

[0015] This invention also provides an integrated, graded, adjustable stiffness variable diameter anchor cable support method, employing an integrated, graded, adjustable stiffness variable diameter anchor cable system, comprising the following steps: S1: Construction drilling and initial anchoring; the construction diameter in the surrounding rock of the roadway is... The borehole is drilled, and resin anchoring agent and hollow anchor rod are installed at the depth of the borehole, with the exposed tension section of the hollow anchor rod exposed on the outside of the borehole opening; the resin anchoring agent is cured by stirring, and the first equal diameter section is anchored in the stable rock layer. S2: Anchor cable installation and initial pre-tensioning; The tray and lock are sequentially installed on the outside of the exposed tensioning section, and the set initial pre-tensioning force is applied to the hollow anchor cable rod using tensioning equipment; S3: Surrounding rock deformation monitoring and stiffness requirement decision-making; The roadway roof subsidence rate is monitored according to the set monitoring cycle. and compare it with a preset critical speed threshold. and The process of comparing and deciding to determine the target stiffness level of the current required anchor cable system is as follows: when At that time, it was determined that the surrounding rock was in a period of severe deformation, and a low-stiffness pressure relief mode was adopted, with the grouting length determined to be... ; when When the surrounding rock is determined to be in the deformation decay period, the decision is to adopt the medium stiffness equilibrium mode; when When the deformation tends to stabilize, it is determined that the surrounding rock has entered a stable period, and a high-rigidity strong support mode is adopted. S4: Controllable grouting based on stiffness adaptation; grouting operation is carried out by connecting the grouting equipment to the grouting channel at the end of the exposed tension section; during the grouting process, a quantitative control method for the grout volume is adopted to control the volume of injected grout. Precisely control the position reached by the axial diffusion front of the grout in the variable diameter section area, as the basis for calculating the grouting length. ; When using the low-stiffness pressure relief mode, determine the grouting length. ,and Not exceeding 40% of the total length of the variable diameter section; When in medium stiffness balance mode, determine the grouting length. ,and It accounts for 60% to 80% of the total length of the variable diameter section; When using a high-rigidity, high-strength support mode, determine the grouting length. ,and It equals the total length of the variable diameter section; S5: Stabilized support based on graded stiffness; after the grout solidifies, a length of [length missing] is formed within the variable diameter section. Stiffness value The grouting adhesive, based on the cured resin anchoring agent and the grouting adhesive, together form a support system with a support stiffness of K.

[0016] Furthermore, in order to ensure that the stiffness level decision can adaptively match different geological conditions and mining stages, and to effectively ensure the accuracy and timeliness of graded support, in S3, the critical velocity threshold is obtained according to formulas (c) and (d), respectively. and ; (c); (d); In the formula, This is a coefficient based on engineering experience. The uniaxial compressive strength of the surrounding rock; The deformation modulus of the surrounding rock; The equivalent radius of the tunnel; The total length of the hollow anchor rod; This is a comprehensive engineering experience coefficient; This is the energy correction factor; This represents the current accumulated roof subsidence. This refers to the maximum cumulative settlement of the roof slab allowed by the design.

[0017] Furthermore, in order to achieve precise control over the position of the slurry diffusion front within the variable diameter section, and to provide quantifiable and repeatable operational basis for the reliable implementation of the graded stiffness, in S4, the position is determined according to formula (e). ; (e); In the formula, For length The average diameter of the variable diameter section within the range.

[0018] Furthermore, in order to ensure that different stiffness levels can be accurately preset and reliably executed by setting the grouting length, in S5, the stiffness value K(S) is obtained according to formula (f). x ); (f); In the formula, The variable diameter section in axial position Bond shear stress at the interface between the slurry and the rod; It represents the elastic modulus of the slurry-bound stone.

[0019] This invention provides an integrated, graded, adjustable stiffness variable-diameter anchor cable method, aiming to create an innovative variable stiffness support solution for complex and difficult roadways, significantly improving the adaptability, reliability, and economy of the support system. First, the first equal-diameter section of the anchor cable is anchored to stable rock strata deep within the borehole using a resin anchoring agent, providing a reliable anchoring foundation for the entire anchor cable system. Unlike traditional full-length anchoring, only the first equal-diameter section is anchored, preserving the free deformation capacity of the variable-diameter and second equal-diameter sections, reserving structural space for subsequent graded stiffness adjustments. Simultaneously, the resin anchoring agent's rapid curing characteristic allows the anchor cable to provide basic anchoring force immediately after construction, ensuring roadway safety during construction and providing a reliable foundation for subsequent graded stiffness loading. Second, through the installation of trays and locking devices, combined with the application of initial preload using tensioning equipment, the anchor cable system possesses a certain degree of active support capability from the initial stage of service, providing an initial working state for subsequent graded stiffness adjustments. The application of the initial preload allows the anchor cable to function in the early stages of surrounding rock deformation, effectively suppressing unnecessary early deformation. Next, the monitoring cycle for the roadway roof subsidence velocity is set and compared with a preset critical velocity threshold, enabling precise identification of the current deformation stage of the surrounding rock. Based on the identification results, three target stiffness levels are determined: low stiffness yielding, medium stiffness balance, and high stiffness strong support, ensuring that the stiffness selection of the anchor cable system precisely matches the deformation stage of the surrounding rock. This decision-making mechanism transforms traditional experience-based support design into a data-driven quantitative decision-making method, solving the common problems of "insufficient strength in the early stage, uncontrolled yielding in the middle stage, and excessive residual deformation in the later stage." Subsequently, a quantitative grouting volume control method is adopted, achieving precise control of the grout diffusion front position within the diameter-changing section by accurately controlling the grouting volume. Based on the determined target stiffness level, the corresponding grouting length is determined. , , This allows for the application of different grouting methods, corresponding to low-stiffness pressure relief, medium-stiffness balance, and high-stiffness strong support modes. This quantitative grouting control transforms stiffness grading from theoretical design into precise on-site operation, ensuring reliable grading results. Finally, the grout binder formed after solidification, in synergy with the resin anchoring agent, constitutes an adjustable anchor cable system. This process represents a fundamental shift in the anchor cable system from a single fixed stiffness to graded adjustable stiffness, enabling the anchor cable support to adapt to the stiffness requirements of the surrounding rock throughout the entire process from severe deformation to stable convergence, significantly improving the control effect and support economy of the roadway surrounding rock.

[0020] This invention transforms the stiffness adjustment function from relying on complex external mechanical components to achieving it through the variable diameter structure design of the anchor cable itself. By changing the locking position of the locking device on the exposed tension section, or by adjusting the effective force-bearing length of the variable diameter section, the overall axial stiffness of the anchor cable system can be changed in stages. During operation, after the anchor cable end anchoring and initial installation are completed, the deformation stage can be determined based on real-time deformation monitoring data of the surrounding rock in the roadway. This allows for the determination of the required support stiffness level and the execution of corresponding adjustment operations. By precisely controlling the effective working state of the variable diameter section, various support modes such as low stiffness yielding, medium stiffness balance, and high stiffness strong support can be flexibly achieved. Compared with existing technologies, this invention has the following advantages: 1) This invention eliminates external complex mechanical moving parts and achieves graded stiffness adjustment through the variable diameter structure design of the anchor rod itself. The system structure is highly integrated and has no external movable connection points, which significantly improves the long-term working reliability and overall durability of the support system.

[0021] 2) The support stiffness of the anchor cable can be continuously and precisely controlled by adjusting the effective bearing state of the variable diameter section. This allows engineers to flexibly match the yielding or strong support mode according to the real-time deformation stage of the surrounding rock, greatly enhancing the active adaptability and intelligent response level of the support.

[0022] 3) The core of this technology is a simple structural component called a variable diameter rod. It does not rely on special components or complex operating processes. While achieving adjustable stiffness, it effectively controls manufacturing costs and construction complexity, and has good engineering economy and feasibility for large-scale promotion.

[0023] 4) The whole method has a clear principle and a well-defined adjustment mechanism, and is highly compatible with conventional anchor cable installation technology, providing on-site engineers with an easy-to-understand and easy-to-implement variable stiffness support solution.

[0024] This method transforms the graded adjustment of support stiffness into precise control of the mechanical behavior of the variable diameter section of the rod, enabling engineers to dynamically decide and implement the most suitable support stiffness scheme based on the surrounding rock deformation monitored at set intervals. In a simple and highly reliable manner, the stiffness of the anchor cable support can be adjusted in a corresponding graded manner according to the stage of surrounding rock deformation, realizing an intelligent transformation from active pressure relief to strong support. This provides an innovative and practical solution for complex and difficult roadways, truly achieving the goal of intelligent support that is either flexible first and then rigid or with adjustable stiffness. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of the variable diameter anchor cable system in this invention (in the unadjusted state after installation). Figure 2This is a schematic diagram of the grout filling state under the low stiffness pressure relief mode of the present invention (corresponding to the grouting length S1). Figure 3 This is a schematic diagram of the grout filling state under the medium stiffness balance mode of the present invention (corresponding to the grouting length S2). Figure 4 This is a schematic diagram of the grout filling state under the high-rigidity strong support mode of the present invention (corresponding to the grouting length S3). Figure 5 This is a schematic diagram of the auxiliary grouting pipeline in this invention; Figure 6 This is a flowchart of the support method in this invention.

[0026] In the diagram: 1. Grout outlet one, 2. Grouting adhesive, 3. Lock, 4. Tray, 5. Drill hole, 6. Resin anchoring agent, 7. Grout stop plug, 8. Hollow anchor rod, 9. Exposed tensioning section, 10. Second equal diameter section, 11. First equal diameter section, 12. Variable diameter section, 13. Grout outlet two, 14. Discharge hole. Detailed Implementation

[0027] The invention will now be further described with reference to the accompanying drawings.

[0028] Existing roadway anchor cable support technology struggles to achieve dynamic and adjustable matching in terms of support stiffness to adapt to the deformation characteristics of the surrounding rock at different engineering stages. While mechanical pressure relief devices provide fixed pressure relief, their stiffness and stroke cannot be adjusted after installation based on actual roadway deformation, and the external structure increases the risk of failure. Full-length bonded anchor cables have their stiffness permanently fixed after installation, lacking any adaptability. Although attempts have been made to indirectly influence support performance by changing the structure or process, these generally suffer from discontinuous adjustment, reliance on complex moving parts, or high costs. Therefore, such as... Figures 1 to 5 As shown, the present invention provides an integrated graded adjustable stiffness variable diameter anchor cable system, including a hollow anchor cable rod 8, a grout stop plug 7, a tray 4, a locking device 3 and a resin anchoring agent 6, wherein a grouting channel is provided at the axis of the hollow anchor cable rod 8. The hollow anchor rod 8 consists of, from left to right, a first equal-diameter section 11, a variable-diameter section 12, a second equal-diameter section 10, and an exposed tensioning section 9. The diameters of the first and second equal-diameter sections are equal, and the diameter is [missing information]. The diameter of the large diameter end of the variable diameter section and equal; The diameter of the variable diameter section 12 gradually decreases from the large diameter end to the small diameter end in a continuous and uniform manner, and its large diameter end is coaxially connected to the first equal diameter section 11, and its small diameter end is coaxially connected to the second equal diameter section 10; at the same time, a grout outlet 1 is provided on the right side of the variable diameter section 12, which is connected to the grouting channel. The grout stopper 7 is fitted onto the left end of the second equal diameter section 10; The tray 4 is slidably fitted onto the outside of the exposed tensioning section 9; The lock 3 is threadedly fitted onto the outside of the exposed tensioning section 9 and is located on the right side of the tray 4; The resin anchoring agent 6 is bonded to the outside of the first equal diameter segment 11. The resin anchoring agent 6 can partially cover the length direction of the first equal diameter segment 11 or completely cover the length direction of the first equal diameter segment 11.

[0029] In this invention, the grout outlet is positioned on the right side of the variable diameter section. This allows the injected grout to smoothly enter the annular gap between the variable diameter section and the borehole from the right end of the variable diameter section. Simultaneously, the grout preferentially diffuses inward from the right end of the variable diameter section, effectively preventing grout waste and interference with the resin anchoring section, thus providing a reliable process guarantee for achieving graded stiffness control. The grout stopper is fitted onto the left end of the second equal-diameter section, confining the grout within the smaller diameter end of the variable diameter section during grouting, effectively preventing grout leakage towards the borehole opening. Furthermore, the tapered geometry of the variable diameter section establishes a definite mathematical relationship between the grouting length and volume, providing sufficient flow space for the grout while ensuring the load-bearing strength of the rod itself. Furthermore, based on the synergistic effect of the installation position of the grout plug and the geometry of the variable diameter section, the position of the grout diffusion front can be precisely controlled through quantitative control of grout volume, stabilization of grout pressure, or control of grouting time. This allows for on-demand switching between three modes—low stiffness yielding, medium stiffness balance, and high stiffness strong support—by controlling the grouting length. It enables precise graded adjustment of support stiffness, perfectly matching the stiffness requirements of the surrounding rock throughout the entire process from severe deformation to stable convergence. This structural design provides an ideal execution platform for subsequently introducing real-time monitoring data, dynamically determining stiffness levels, and automatically executing grouting control, providing reliable technical support for intelligent adaptive support systems. This invention achieves stiffness adjustment through the integrated design of the variable diameter rod and adjustment mechanism, eliminating complex external mechanical components and requiring no additional moving parts. By adjusting the effective working length or stress state of the variable diameter section, the overall mechanical stiffness of the anchor cable system can be directly and gradedly changed.

[0030] This system features a simple structure, low manufacturing cost, and convenient adjustment. It can change the support stiffness not only by altering the locking position of the locks on the exposed tensioning section but also by adjusting the grouting length in the outer area of ​​the variable diameter section. It can provide corresponding levels of support stiffness based on the deformation of the surrounding rock in the roadway, allowing for proactive adjustment of the support stiffness according to the actual roadway conditions. This enables the locks to provide the required preload in the initial stage, and after reaching the set monitoring cycle, the support stiffness can be proactively adjusted according to the actual roadway conditions. This significantly improves the adaptability, reliability, and economy of the support system, providing an innovative variable stiffness support solution for complex and difficult roadways.

[0031] To provide sufficient flow space for the grouting slurry while avoiding insufficient local load-bearing capacity of the rod due to an excessively small diameter, the diameter of the small diameter end of the variable diameter section 12 is... The range of values ​​is The diameter is 70% to 90%, and not less than 14 mm. Preferably, the diameter of the first equal diameter segment 11 and the second equal diameter segment 10 is... The diameter is 17.8 mm, 20 mm, or 22 mm; the length of the variable diameter section 12 is 800 mm to 1500 mm.

[0032] In order to ensure that the stress in the variable diameter section can transition smoothly along the axial direction under the action of tensile load, and to make full use of the strength of the rod material, the diameter variation law of the variable diameter section 12 is as shown in formula (a). (a); In the formula, For the variable diameter section 12 in the axial position The diameter at that point; This represents the rate of change in diameter. The axial coordinates are taken as the origin from the large diameter end of the variable diameter section 12.

[0033] In order to ensure the structural reliability and long-term stability during the graded stiffness adjustment process, the stress strength of the variable diameter section 12 satisfies formula (b); thereby, the safety of the hollow anchor rod 8 under the combined tension and bending stress conditions is ensured. (b); In the formula, To estimate the maximum axial tensile force; To estimate the maximum bending moment; The yield strength of the rod material; To consider the overall safety factor, .

[0034] As a preferred embodiment, the grout stopper 7 is made of water-swellable rubber or a highly elastic compression sealing material. It is compressed during installation and is used to confine the grout within the variable diameter section during the grouting process. By reliably sealing the annular gap between the variable diameter section and the second diameter section, it prevents the grout from leaking towards the orifice.

[0035] As a preferred embodiment, the distance between the slurry outlet 1 and the small diameter end of the variable diameter section 12 is 10~30 mm, which ensures that the slurry diffuses from the beginning of the variable diameter section.

[0036] As a preferred option, the left side of the variable diameter section 12 is also provided with a grout outlet 2 13, which can support the online upgrading of support performance. After the initial grouting to form a low-stiffness foundation, if subsequent monitoring cycles indicate that the support stiffness needs to be increased, the grout outlet 2 13 can be used for subsequent supplementary grouting operations to increase the effective grouting bonding length in the area where the variable diameter section is located, thereby achieving a progressive enhancement of support stiffness from low to medium and even high levels. When both grout outlet 1 and grout outlet 13 are provided, an auxiliary grouting pipeline with one end closed and the other end open is used. The auxiliary grouting pipeline has a discharge hole 14 on one side of the closed end. When grouting is first performed using grout outlet 1, the auxiliary grouting pipeline is inserted into the grouting channel from the exposed end of the tensioning section 9, with the discharge hole 14 aligned with grout outlet 1. The auxiliary grouting pipeline is removed after the grouting operation is completed and the grout has solidified, ensuring that the grouting channel is not blocked by the solidified grout, allowing subsequent grouting operations to be performed using grout outlet 13. More preferably, a sealing piston can also be provided at the closed end of the auxiliary grouting pipeline to seal with the grouting channel, ensuring the reliability of the grouting operation.

[0037] like Figure 6 As shown, the present invention also provides an integrated graded adjustable stiffness variable diameter anchor cable support method, which employs an integrated graded adjustable stiffness variable diameter anchor cable system and includes the following steps: S1: Construction drilling and initial anchoring; the construction diameter in the surrounding rock of the roadway is... A borehole 5 is drilled, and a resin anchoring agent 6 and a hollow anchor cable rod 8 are installed at its depth, with the exposed tension section 9 of the hollow anchor cable rod 8 exposed on the outside of the borehole opening. The resin anchoring agent 6 is cured by stirring, and the first equal-diameter section 11 is anchored in the stable rock strata. It is 30-32mm; S2: Anchor cable installation and initial pre-tightening; The tray 4 and the lock 3 are sequentially installed on the outside of the exposed tensioning section 9, and the set initial pre-tightening force is applied to the hollow anchor cable rod 8 using the tensioning equipment; S3: Surrounding rock deformation monitoring and stiffness requirement decision-making; The roadway roof subsidence rate is monitored according to the set monitoring cycle. and compare it with a preset critical speed threshold. and The process of comparing and deciding to determine the target stiffness level of the current required anchor cable system is as follows: when At that time, it was determined that the surrounding rock was in a period of severe deformation, and a low-stiffness pressure relief mode was adopted, with the grouting length determined to be... ; when When the surrounding rock is determined to be in the deformation decay period, the decision is to adopt the medium stiffness equilibrium mode; when When the deformation tends to stabilize, it is determined that the surrounding rock has entered a stable period, and a high-rigidity strong support mode is adopted. S4: Controllable grouting based on stiffness adaptation; determining the planned grouting length required to achieve the target stiffness level; connecting the grouting equipment to the grouting channel at the end of the exposed tensioning section 9 for grouting operation; during the grouting process, a quantitative control method for grout volume is adopted to control the volume of injected grout. The precise control of the grout's axial diffusion front position in region 12 of the variable diameter section is used to calculate the grouting length. As an alternative, the grouting pressure stabilization method or the grouting time control method can also be used to achieve precise control of the grout diffusion front position. When using the low-stiffness pressure relief mode, determine the grouting length. ,and Not exceeding 40% of the total length of the variable diameter section 12; When in medium stiffness balance mode, determine the grouting length. ,and It accounts for 60% to 80% of the total length of the variable diameter section 12; When using a high-rigidity, high-strength support mode, determine the grouting length. ,and It equals the total length of the variable diameter section 12; S5: Stabilized support based on graded stiffness; after the grout solidifies, a length of [length missing] is formed within the variable diameter section 12. Stiffness value The grouting adhesive 2, together with the cured resin anchoring agent 6, forms a support system with a support stiffness of K.

[0038] To ensure that stiffness level decisions can adaptively match different geological conditions and mining stages, and to effectively ensure the accuracy and timeliness of graded support, in S3, the critical velocity threshold is obtained according to formulas (c) and (d), respectively. and ; (c); (d); In the formula, This is a coefficient based on engineering experience. The uniaxial compressive strength of the surrounding rock; The deformation modulus of the surrounding rock; The equivalent radius of the tunnel; The total length of the hollow anchor rod is 8. This is a comprehensive engineering experience coefficient used to reflect the creep characteristics of the surrounding rock, the coupling effect between the support system and the surrounding rock, and the energy release law on the critical velocity threshold. The impact; This is the energy correction factor; This represents the current accumulated roof subsidence. This refers to the maximum cumulative settlement of the roof slab allowed by the design. The threshold representing the drastic deformation of the surrounding rock from a stable or slow deformation state; This represents the threshold from severe deformation to near-stability. It is a critical velocity threshold used to distinguish between the deformation decay period (medium stiffness steady mode) and the stable period (high stiffness strong support mode). Its determination requires comprehensive consideration of the creep characteristics of the surrounding rock, the coupling effect between the support system and the surrounding rock, and the energy release law.

[0039] In order to achieve precise control over the position of the slurry diffusion front within the variable diameter section, and to provide quantifiable and repeatable operational basis for the reliable implementation of graded stiffness, in S4, the position is determined according to formula (e). ; (e); In the formula, For length The average diameter of the variable diameter section 12 within the range.

[0040] As a preferred option, in S5, the stiffness value K(S) is obtained according to formula (f). x ); (f); In the formula, For the variable diameter section 12 in the axial position Bond shear stress at the interface between the slurry and the rod; It represents the elastic modulus of the slurry-bound stone.

[0041] This invention provides an integrated, graded, adjustable stiffness variable-diameter anchor cable method, aiming to create an innovative variable stiffness support solution for complex and difficult roadways, significantly improving the adaptability, reliability, and economy of the support system. First, the first equal-diameter section of the anchor cable is anchored to stable rock strata deep within the borehole using a resin anchoring agent, providing a reliable anchoring foundation for the entire anchor cable system. Unlike traditional full-length anchoring, only the first equal-diameter section is anchored, preserving the free deformation capacity of the variable-diameter and second equal-diameter sections, reserving structural space for subsequent graded stiffness adjustments. Simultaneously, the resin anchoring agent's rapid curing characteristic allows the anchor cable to provide basic anchoring force immediately after construction, ensuring roadway safety during construction and providing a reliable foundation for subsequent graded stiffness loading. Second, through the installation of trays and locking devices, combined with the application of initial preload using tensioning equipment, the anchor cable system possesses a certain degree of active support capability from the initial stage of service, providing an initial working state for subsequent graded stiffness adjustments. The application of the initial preload allows the anchor cable to function in the early stages of surrounding rock deformation, effectively suppressing unnecessary early deformation. Next, the monitoring cycle for the roadway roof subsidence velocity is set and compared with a preset critical velocity threshold, enabling precise identification of the current deformation stage of the surrounding rock. Based on the identification results, three target stiffness levels are determined: low stiffness yielding, medium stiffness balance, and high stiffness strong support, ensuring that the stiffness selection of the anchor cable system precisely matches the deformation stage of the surrounding rock. This decision-making mechanism transforms traditional experience-based support design into a data-driven quantitative decision-making method, solving the common problems of "insufficient strength in the early stage, uncontrolled yielding in the middle stage, and excessive residual deformation in the later stage." Subsequently, a quantitative grouting volume control method is adopted, achieving precise control of the grout diffusion front position within the diameter-changing section by accurately controlling the grouting volume. Based on the determined target stiffness level, the corresponding grouting length is determined. , , This allows for the application of different grouting methods, corresponding to low-stiffness pressure relief, medium-stiffness balance, and high-stiffness strong support modes. This quantitative grouting control transforms stiffness grading from theoretical design into precise on-site operation, ensuring reliable grading results. Finally, the grout binder formed after solidification, in synergy with the resin anchoring agent, constitutes an adjustable anchor cable system. This process represents a fundamental shift in the anchor cable system from a single fixed stiffness to graded adjustable stiffness, enabling the anchor cable support to adapt to the stiffness requirements of the surrounding rock throughout the entire process from severe deformation to stable convergence, significantly improving the control effect and support economy of the roadway surrounding rock.

[0042] This invention transforms the stiffness adjustment function from relying on complex external mechanical components to achieving it through the variable diameter structure design of the anchor cable itself. By changing the locking position of the locking device on the exposed tension section, or by adjusting the effective force-bearing length of the variable diameter section, the overall axial stiffness of the anchor cable system can be changed in stages. During operation, after the anchor cable end anchoring and initial installation are completed, the deformation stage can be determined based on real-time deformation monitoring data of the surrounding rock in the roadway. This allows for the determination of the required support stiffness level and the execution of corresponding adjustment operations. By precisely controlling the effective working state of the variable diameter section, various support modes such as low stiffness yielding, medium stiffness balance, and high stiffness strong support can be flexibly achieved. Compared with existing technologies, this invention has the following advantages: 1) This invention eliminates external complex mechanical moving parts and achieves graded stiffness adjustment through the variable diameter structure design of the anchor rod itself. The system structure is highly integrated and has no external movable connection points, which significantly improves the long-term working reliability and overall durability of the support system.

[0043] 2) The support stiffness of the anchor cable can be continuously and precisely controlled by adjusting the effective bearing state of the variable diameter section. This allows engineers to flexibly match the yielding or strong support mode according to the real-time deformation stage of the surrounding rock, greatly enhancing the active adaptability and intelligent response level of the support.

[0044] 3) The core of this technology is a simple structural component called a variable diameter rod. It does not rely on special components or complex operating processes. While achieving adjustable stiffness, it effectively controls manufacturing costs and construction complexity, and has good engineering economy and feasibility for large-scale promotion.

[0045] 4) The whole method has a clear principle and a well-defined adjustment mechanism, and is highly compatible with conventional anchor cable installation technology, providing on-site engineers with an easy-to-understand and easy-to-implement variable stiffness support solution.

[0046] This method transforms the graded adjustment of support stiffness into precise control of the mechanical behavior of the variable diameter section of the rod, enabling engineers to dynamically decide and implement the most suitable support stiffness scheme based on the surrounding rock deformation monitored at set intervals. In a simple and highly reliable manner, the stiffness of the anchor cable support can be adjusted in a corresponding graded manner according to the stage of surrounding rock deformation, realizing an intelligent transformation from active pressure relief to strong support. This provides an innovative and practical solution for complex and difficult roadways, truly achieving the goal of intelligent support that is either flexible first and then rigid or with adjustable stiffness.

Claims

1. An integrated, graded, adjustable stiffness variable diameter anchor system, comprising a hollow anchor rod (8), a grout stopper (7), a tray (4), a locking device (3), and a resin anchoring agent (6), wherein a grouting channel is provided at the axis of the hollow anchor rod (8), characterized in that... ； The hollow anchor rod (8) consists of, from left to right, a first equal-diameter section (11), a variable-diameter section (12), a second equal-diameter section (10), and an exposed tensioning section (9). The first equal-diameter section (11) and the second equal-diameter section (10) have the same diameter, and their diameters are equal. The diameter of the large diameter end of the variable diameter section (12) and equal; The diameter of the variable diameter section (12) gradually decreases from the large diameter end to the small diameter end in a continuous and uniform manner, and its large diameter end is coaxially connected to the first equal diameter section (11), and its small diameter end is coaxially connected to the second equal diameter section (10); at the same time, a grout outlet (1) communicating with the grouting channel is provided on the side of the right part of the variable diameter section (12). The grout stopper (7) is fitted onto the left end of the second equal diameter section (10); The tray (4) is slidably fitted onto the outside of the exposed tensioning section (9); The lock (3) is threadedly fitted onto the outside of the exposed tensioning section (9) and located on the right side of the tray (4); The resin anchoring agent (6) is bonded to the outside of the first equal diameter segment (11).

2. The integrated graded adjustable stiffness variable diameter anchor cable system according to claim 1, characterized in that, The diameter of the smaller diameter end of the variable diameter section (12) The range of values ​​is 70% to 90%, and not less than 14 mm.

3. The integrated graded adjustable stiffness variable diameter anchor cable system according to claim 1 or 2, characterized in that, The diameter variation law of the variable diameter section (12) is shown in formula (a); （a）； In the formula, For the variable diameter section (12) in the axial position The diameter at that point; This represents the rate of change in diameter. The axial coordinate is taken as the origin of the large diameter end of the variable diameter section (12).

4. The integrated graded adjustable stiffness variable diameter anchor cable system according to claim 3, characterized in that, The stress strength of the variable diameter section (12) satisfies formula (b). （b）； In the formula, To estimate the maximum axial tensile force; To estimate the maximum bending moment; The yield strength of the rod material; To consider the overall safety factor, .

5. The integrated graded adjustable stiffness variable diameter anchor cable system according to claim 3, characterized in that, The grout stopper (7) is made of water-swellable rubber or highly elastic compression sealing material.

6. The integrated graded adjustable stiffness variable diameter anchor cable system according to claim 4, characterized in that, The distance between the slurry outlet (1) and the small diameter end of the variable diameter section (12) is 10~30 mm.

7. A method for integrated graded adjustable stiffness variable diameter anchor cable support, employing the integrated graded adjustable stiffness variable diameter anchor cable system described in claim 4, characterized in that, Includes the following steps: S1: Construction drilling and initial anchoring; the construction diameter in the surrounding rock of the roadway is... The borehole (5) is drilled, and resin anchoring agent (6) and hollow anchor rod (8) are installed at the depth of the borehole (5), and the exposed tension section (9) of the hollow anchor rod (8) is exposed on the outside of the borehole (5); the resin anchoring agent (6) is cured by stirring, and the first equal diameter section (11) is anchored in the stable rock layer. S2: Anchor installation and initial pre-tightening; The tray (4) and lock (3) are sequentially installed on the outside of the exposed tension section (9), and the set initial pre-tightening force is applied to the hollow anchor rod (8) using the tensioning equipment; S3: Surrounding rock deformation monitoring and stiffness requirement decision-making; The roadway roof subsidence rate is monitored according to the set monitoring cycle. and compare it with a preset critical speed threshold. and The process of comparing and deciding to determine the target stiffness level of the current required anchor cable system is as follows: when At that time, it was determined that the surrounding rock was in a period of severe deformation, and a low-stiffness pressure relief mode was adopted, with the grouting length determined to be... ; when When the surrounding rock is determined to be in the deformation decay period, the decision is to adopt the medium stiffness equilibrium mode; when When the deformation tends to stabilize, it is determined that the surrounding rock has entered a stable period, and a high-rigidity strong support mode is adopted. S4: Controllable grouting based on stiffness adaptation; Connect the grouting equipment to the grouting channel at the end of the exposed tensioning section (9) and carry out grouting operations; During the grouting process, a quantitative control method for grouting volume is adopted, which controls the volume of injected grout. The position of the axial diffusion front of the grout in the variable diameter section (12) is precisely controlled to calculate the grouting length. ; When using the low-stiffness pressure relief mode, determine the grouting length. ,and Not greater than 40% of the total length of the variable diameter section (12); When in medium stiffness balance mode, determine the grouting length. ,and It accounts for 60% to 80% of the total length of the variable diameter section (12); When using a high-rigidity, high-strength support mode, determine the grouting length. ,and It is equal to the total length of the variable diameter section (12); S5: Stabilized support based on graded stiffness; after the grout solidifies, a length of [length missing] is formed in the variable diameter section (12). Stiffness value The grouting adhesive (2) and the cured resin anchor (6) together form a support system with a support stiffness of K.

8. The integrated graded adjustable stiffness variable diameter anchor cable support method according to claim 7, characterized in that, In S3, the critical velocity threshold is obtained according to formulas (c) and (d) respectively. and ; （c）； （d）； In the formula, This is a coefficient based on engineering experience. The uniaxial compressive strength of the surrounding rock; The deformation modulus of the surrounding rock; The equivalent radius of the tunnel; The total length of the hollow anchor rod (8); This is a comprehensive engineering experience coefficient; This is the energy correction factor; This represents the current accumulated roof subsidence. This refers to the maximum cumulative settlement of the roof slab allowed by the design.

9. The integrated graded adjustable stiffness variable diameter anchor cable support method according to claim 7, characterized in that, In S4, it is determined according to formula (e). ; （e）； In the formula, For length The average diameter of the variable diameter section (12) within the range.

10. The integrated graded adjustable stiffness variable diameter anchor cable support method according to claim 7, characterized in that, In S5, the stiffness value K(S) is obtained according to formula (f). x ); （f）； In the formula, For the variable diameter section (12) in the axial position Bond shear stress at the interface between the slurry and the rod; It represents the elastic modulus of the slurry-bound stone.

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