Pressure relief and self-repairing anchor rod device and anchoring method based on porous brittle structure

Abstract

The application provides a pressure relief and self-repairing anchor rod device based on a porous brittle structure and an anchoring method, and belongs to the technical field of coal mine roadway anchor rod supporting. The brittle sacrificial sleeve is made of a material with low strength, porosity and permeability and cementation of grout, and is connected with the hollow grouting anchor rod body through limited bonding force. The method comprises the following steps: after drilling, the anchor agent is loaded, the anchor rod device is inserted and rotated to mix and complete the end anchoring; the annular space is filled and the brittle sacrificial sleeve is wrapped through the hollow rod body grouting, the tray nut is installed and pre-tightened; the sleeve serves as a force transmission medium under normal load; the sleeve can be controlled to break to form a flexible area to relieve pressure and protect the rod body under overload; after breaking, the grout seeps into the cracks to cement the broken pieces, and the anchoring interface is reconstructed to realize functional self-repairing. The application can realize the instantaneousness, controllability of pressure relief behavior and the recoverability of anchoring function.

Description

Technical Field

[0001] This invention belongs to the field of coal mine roadway anchor support technology, specifically relating to a pressure relief and self-healing anchor device and anchoring method based on a porous brittle structure. Background Technology

[0002] With the continuous increase in the depth and intensity of mineral resource mining, the problems of high ground stress, strong mining disturbance, and large deformation of surrounding rock faced by tunnel engineering are becoming increasingly severe. Especially in soft rock strata, geologically fractured zones, or areas affected by intense mining, the surrounding rock of tunnels not only exhibits significant time-varying creep characteristics, but is also more prone to accumulating a large amount of elastic strain energy in deep high-stress environments. Moreover, this energy is at risk of being suddenly released in the form of dynamic disasters such as rock bursts and rock bursts.

[0003] While traditional rock bolt support systems can provide a certain static resistance to constrain surrounding rock deformation, their stiffness characteristics mean that the bolts are prone to brittle fracture due to excessive instantaneous stress when subjected to sudden impact loads, leading to the overall failure of the support system. Therefore, how to endow the support system with intelligent and controllable pressure relief capabilities, enabling it to actively and rapidly transfer and dissipate energy when faced with sudden high stress or impact loads, thereby effectively protecting the main anchoring structure from damage, has become a core technical challenge urgently needing to be overcome in the field of surrounding rock safety control in deep roadways.

[0004] Currently, the technical approaches for energy regulation and stress relief in roadway surrounding rock mainly fall into two categories. The first is pre-stress relief methods, such as advanced drilling and blasting loosening. These methods involve proactive intervention during the construction phase and cannot respond in real-time to the dynamically evolving load conditions during the roadway's service life. The second involves integrating energy-relieving elements within the support components, such as various extendable anchors and pressure-relieving pipes. While these technologies can adapt to surrounding rock displacement and release some energy to a certain extent through structural slippage or plastic deformation, they still have the following significant shortcomings: First, pressure relief behavior is mostly a passive response mechanism, and its activation threshold and energy-relieving process are difficult to precisely match with the actual stress state of the surrounding rock. Second, the pressure relief mechanism generally relies on the permanent plastic deformation or frictional slippage of the components themselves. Once triggered, it is often accompanied by irreversible loss of support stiffness and preload, even leading to complete failure of the anchoring function, resulting in immediate collapse and failing to meet the basic requirements for long-term roadway stability. Furthermore, existing technologies generally lack the ability to self-repair after pressure relief, and their mechanical behavior is irreversible. The aforementioned defects make it difficult for existing pressure relief support technologies to achieve a substantial balance between instantaneous safe pressure relief and long-term effective anchoring.

[0005] To overcome the aforementioned key technological bottlenecks, it is urgent to develop a pressure relief and self-healing anchor bolt device and method based on a porous brittle structure, so as to achieve the organic unity of the instantaneity and controllability of pressure relief behavior and the recoverability of anchoring function, and provide a brand-new technical solution for the prevention and control of dynamic disasters in deep roadways. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a pressure relief and self-healing anchor bolt device and anchoring method based on a porous brittle structure. This device achieves an organic unity of the instantaneity and controllability of pressure relief behavior with the recoverability of anchoring function. It provides a novel support equipment solution with simple structure, reliable performance, and self-healing capability for rock mass control in deep tunnels, high-stress soft rock, and areas prone to rockbursts. This method fundamentally changes the inherent irreversible defects of traditional pressure relief support functions, endowing the anchoring system with self-repair and functional regeneration capabilities after experiencing extreme loads, and providing reliable technical assurance for maintaining long-term stability of deep tunnels throughout their entire life cycle.

[0007] To achieve the above objectives, the present invention provides a pressure relief and self-healing anchor bolt device based on a porous brittle structure, the anchor bolt device comprising a hollow grouting anchor bolt body, a tray, a fastening nut, and a brittle sacrificial sleeve; The hollow grouting anchor rod body includes an exposed section and an embedded section; the tray and fastening nut are sequentially installed on the exposed section of the hollow grouting anchor rod body. The brittle sacrificial sleeve is fitted onto a predetermined specific position on the embedded section of the hollow grouting anchor rod. The brittle sacrificial sleeve is made of a low-strength, porous material that can be penetrated and cemented by grout, and is connected to the hollow grouting anchor rod through a limited adhesive force. The uniaxial compressive strength of the brittle sacrificial sleeve is configured to be 20% to 50% of the yield strength of the hollow grouting anchor rod. The porous structure of the brittle sacrificial sleeve and its limited bonding with the hollow grouting anchor rod together constitute a stress sensing and control interface. The stress sensing and control interface is configured to: serve as a force transmission medium to maintain support stiffness under normal load conditions; release energy through the controllable fracture of the brittle sacrificial sleeve itself under overload conditions; and achieve penetration bonding and functional repair of the fractured area under the action of grouting slurry.

[0008] As a preferred embodiment, the brittle sacrificial sleeve is made of porous low-grade cement-based material or controllable fracture composite material, with an internal directional or random interconnected pore structure and a porosity controlled between 15% and 30%. The interconnected pore structure is configured as follows: firstly, as a preset weakening path to guide the brittle sacrificial sleeve to undergo controllable fracture along the pores or grain boundaries under overload; secondly, as a transport channel for subsequent grout penetration and bonding to support self-healing function.

[0009] As a preferred embodiment, the brittle sacrificial sleeve is made of industrial-grade porous cement-based composite material, the components of which include low-grade cement, aggregate, toughening fibers and pore-forming agent; the porous structure of the brittle sacrificial sleeve has been prefabricated before installation.

[0010] Furthermore, in order to precisely deploy the active stress relief and repair function to the most needed locations, specific preset locations are determined based on the boundaries of high stress concentration zones or plastic zones in the roadway, as determined by numerical simulation or field measurements. As shown in formula (1); (1); In the formula, A coefficient related to lithology and support density; The deformation modulus of the surrounding rock; The borehole diameter; It represents the uniaxial compressive strength of the surrounding rock.

[0011] The stress-relieving and self-healing anchor bolt device based on a porous brittle structure provided by this invention mainly consists of a hollow grouting anchor bolt body, a brittle sacrificial sleeve fitted into a specific section of the bolt body, a tray, and a fastening nut. The brittle sacrificial sleeve is made of a low-strength, porous material that can be penetrated and cemented by grout. It is connected to the bolt body through limited adhesive force, forming a core stress-sensing and control interface. Compared to the brittle fracture failure of traditional anchor bolts due to excessive stiffness under impact loads, this device precisely configures the uniaxial compressive strength of the sleeve to 20% to 50% of the bolt body's yield strength, maintaining the initial support stiffness required by the composite anchor body during normal load-bearing stages, thus ensuring effective constraint on surrounding rock deformation. This device deeply couples the porous structure of the brittle sacrificial sleeve with the flow characteristics of the grouting slurry. The pre-designed interconnected pore structure inside the sleeve acts as a weakening path to guide the orderly propagation of cracks before fragmentation, ensuring the controllability and predictability of the fragmentation behavior. After fragmentation, the inherent porous structure of the sleeve and the resulting crack network provide secondary penetration channels for the grouting slurry. The slurry penetrates and cements the fragments under capillary action, rebuilding the anchoring interface primarily based on mechanical interlocking, achieving self-repair of the support function. This mechanism ensures that the anchored section after pressure relief is not permanently failed, but can autonomously rebuild a composite anchor body with significant residual strength. This effectively overcomes the fundamental defect in existing technologies where pressure relief and anchoring functions are mutually exclusive, achieving the goal of long-term support without collapse after pressure relief. Furthermore, the structural design of this device fully considers the convenience and economy of engineering implementation. The brittle sacrificial sleeve is made of common engineering materials such as cement-based materials. Its structural design and construction technology are highly compatible with existing anchor bolt systems, requiring no changes to the mainstream operation process or the addition of complex external mechanisms. While ensuring conventional static load anchoring performance, it embeds intelligent pressure relief capabilities into the support system. The entire device does not introduce complex mechanical components or electronic sensing elements. Its stress sensing, controlled fragmentation, and self-healing functions are passively achieved through the intrinsic properties of the materials and the structural design, exhibiting extremely high reliability, durability, and environmental adaptability.

[0012] This device can achieve an organic unity of instantaneous and controllable decompression behavior and recoverable anchoring function. It has good engineering adaptability and feasibility for promotion, and provides a new support equipment solution with simple structure, reliable performance and self-healing capability for surrounding rock control in deep tunnels, high-stress soft rock and areas prone to rockbursts.

[0013] This invention also provides a pressure relief and self-healing anchoring method based on a porous brittle structure, employing a pressure relief and self-healing anchor bolt device based on a porous brittle structure, comprising the following steps: S1: Drilling operation; Drilling at the predetermined support location in the surrounding rock of the tunnel; S2: Install anchoring agent; install anchoring agent into the bottom of the borehole; S3: Install the anchor bolt device; insert the anchor bolt device into the borehole. During installation, the anchoring agent is stirred by rotating and pushing the hollow grouting anchor bolt body to complete the end anchoring of the hollow grouting anchor bolt body. S4: Grouting; Grouting is performed along the entire length of the hollow grouting anchor rod through the inner hole channel, so that the grout fills the annular space between the hollow grouting anchor rod and the borehole wall, and wraps the brittle sacrificial sleeve. S5: Install the tray and tighten the nut; after the grout reaches the predetermined strength, install the tray and tighten the nut in sequence at the exposed end of the hollow grouting anchor rod, and apply pre-tightening force; S6: Normal load bearing and stress perception; In the normal load bearing stage, a composite anchor body with initial design stiffness is formed by the brittle sacrificial sleeve wrapped by grout, the grout and the hollow grouting anchor rod. The brittle sacrificial sleeve serves as a uniform stress transmission medium. S7: Brittle fracture and active stress relief; When the stress of the hollow grouting anchor rod increases sharply due to large deformation of the surrounding rock or impact load, and the high circumferential tensile stress is transferred to the brittle sacrificial sleeve through the bonding interface, the brittle sacrificial sleeve, due to its low material strength and high brittleness, will preferentially generate and expand cracks in the internal pores or defect tips, and then undergo macroscopic fracture; This macroscopic fracture process actively cuts off the rigid stress transmission path between the hollow grouting anchor rod and the external grout in the section covered by the brittle sacrificial sleeve in a short time, forming an instantaneous mechanical flexibility zone, allowing the hollow grouting anchor rod to generate limited plastic tension or micro-slippage with the grout, so as to release overload stress waves and deformation energy; S8: Grout penetration and functional self-repair; The crack network and inherent pores generated after the brittle sacrificial sleeve fractures are connected with the grout that has not yet fully solidified or is flowing due to subsequent surrounding rock compaction, becoming the preferred channel for secondary grout penetration; The grout penetrates into the cracks under capillary action or slight pressure, re-cementing the fragments and forming a new bonding interface between the hollow grouting anchor rod surface and the fragments, mainly based on mechanical interlocking, thereby rebuilding a composite anchor body with residual strength and realizing partial or most of the restoration of the support function.

[0014] As a preferred approach, in S7, the critical stress at which the brittle sacrificial sleeve undergoes controlled fracture is obtained according to formula (2). and ensure ; (2); In the formula, The shape factor is related to the sleeve structure and manufacturing process; The tensile strength of the sleeve base material; For the sleeve wall thickness; denoted as the average radius of the sleeve; p is the porosity of the sleeve; m is the porosity influence index. The yield strength of the rod. This refers to the bonding strength of the resin anchoring agent.

[0015] As a preferred method, in S7, the total energy dissipation during the brittle sacrificial sleeve fragmentation process is obtained according to formula (3). ; (3); In the formula, The fracture toughness of the sleeve material; This represents the total area of ​​newly formed cracks; To match the slip velocity The relevant coefficient of kinetic friction, For displacement with fragmentation Changing interface normal stress; The circumference of the rod is The characteristic slip is denoted as .

[0016] As a preferred method, in S8, the long-term residual strength of the composite anchor solid formed after self-healing is obtained according to formula (4). ; (4); In the formula, It contributes to the chemical bonding strength of slurry hydration products between fragments. The percentage of cracks effectively filled by grout; Contributes to the strength of the mechanical interlocking between the fragments and the rod; This is a permanent porosity that cannot be restored.

[0017] As a preferred method, in S8, the completion time of the slurry self-healing process is obtained according to formula (5). ; (5); In the formula, The viscosity of the slurry; Characteristic penetration depth; The surface tension of the slurry; The contact angle between the slurry and the sleeve material; The average crack width; This refers to the solidification time of the slurry.

[0018] This invention provides a pressure relief and self-healing anchoring method based on porous brittle structures. It organically integrates drilling, anchoring agent loading, anchor bolt installation, initial grouting, tray fastening, and subsequent service stages of normal load-bearing, brittle fracture, and grout self-healing into a unified continuous process. This achieves systematic control over the entire process from construction and installation to functional evolution. Moreover, the entire process does not require any external signal triggering or manual intervention and is completed autonomously entirely by relying on the synergistic effect of material constitutive relations and structural design.

[0019] Compared to traditional anchor bolt construction methods that only focus on the formation of anchoring force during the installation phase, this method explicitly installs a brittle sacrificial sleeve along with the hollow grouting anchor bolt body. Full-length grouting ensures the sleeve is fully encapsulated, thus pre-constructing the stress sensing and control interface during the construction phase. This interface, as an embedded stress sensing and response unit, can achieve precise triggering based on a preset strength threshold. When the surrounding rock of the tunnel undergoes large deformation or impact loads during subsequent service, the sleeve requires no external signal excitation; it can initiate the fracture and pressure relief procedure solely based on its own material constitutive relationship and stress state. This achieves fully passive intelligent protection integrating sensing, decision-making, and execution, greatly improving the timeliness and reliability of the support system under extreme conditions.

[0020] The core advantage of the brittle fragmentation and active stress relief mechanism achieved by this method lies in the ordered and controllable nature of the fragmentation behavior. Because the brittle sacrificial sleeve has a pre-designed directional or random interconnected pore structure, under overload stress, cracks preferentially initiate and propagate along pre-designed weakening paths such as pores or grain boundaries. This controllable fragmentation behavior can instantly sever local rigid force transmission paths, forming a temporary flexible zone, thereby effectively releasing abrupt loads and deformation energy from the surrounding rock and protecting the rod from brittle fracture. This method cleverly utilizes the principles of material fracture mechanics and structural weak surface design, transforming the passive failure of traditional anchor bolts under impact loads into an active and ordered energy release process.

[0021] The most significant innovation of this method lies in the grout penetration and self-repair process it achieves. Existing pressure-relief anchors or devices often permanently lose their support function once triggered, while this method fully utilizes the flow and cementation characteristics of the grout after the sleeve breaks apart. The fracture network formed after the sleeve breaks provides a natural secondary penetration channel for the grout. Driven by capillary force or surrounding rock compaction, the grout can spontaneously penetrate into the fracture space, re-cementing the fragmented blocks into a whole. This process allows the support system to recover significant residual strength after pressure relief, and the repaired composite anchor body forms a new bonding interface, primarily based on mechanical interlocking, between the surface of the hollow grout anchor and the fragments.

[0022] This method is simple to implement and has low implementation costs. It fundamentally changes the inherent defect of the irreversible function of traditional pressure relief support, and endows the anchoring system with the ability to self-repair and regenerate after experiencing extreme loads, providing a reliable technical guarantee for the long-term stability of deep roadways throughout their entire life cycle. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the anchor bolt device in the normal load-bearing state in this invention; Figure 2 This is a schematic diagram of the anchor bolt device in the broken and depressurized state in this invention; Figure 3 This is a schematic diagram of the anchor bolt device in the self-healing anchoring state in this invention; Figure 4 This is a schematic diagram of the brittle sacrificial sleeve under normal load-bearing conditions in this invention; Figure 5 This is a schematic diagram of the brittle sacrificial sleeve in the fractured and depressurized state in this invention; Figure 6 This is a schematic diagram of the brittle sacrificial sleeve in a self-healing anchoring state in this invention; Figure 7 This is a flowchart of the anchoring method in this invention.

[0024] In the diagram: 1. Hollow grouting anchor rod body, 2. Brittle sacrificial sleeve, 3. Tray, 4. Fastening nut, 5. Grout, 6. Grout outlet, 7. Anchoring agent. Detailed Implementation

[0025] The present invention will be further described below.

[0026] like Figures 1 to 7 As shown, the present invention provides a pressure relief and self-healing anchor bolt device based on a porous brittle structure. The anchor bolt device includes a hollow grouting anchor bolt body 1, a tray 3, a fastening nut 4, and a brittle sacrificial sleeve 2. The hollow grouting anchor rod body 1 includes an exposed section and an embedded section; the tray 3 and the fastening nut 4 are sequentially installed on the exposed section of the hollow grouting anchor rod body 1. The brittle sacrificial sleeve 2 is sleeved on a predetermined specific position on the embedded section of the hollow grouting anchor rod 1. The brittle sacrificial sleeve 2 is made of a low-strength, porous material that can be penetrated and cemented by grout, and is connected to the hollow grouting anchor rod 1 by a limited adhesive force. The uniaxial compressive strength of the brittle sacrificial sleeve 2 is configured to be 20% to 50% of the yield strength of the hollow grouting anchor rod 1. The porous structure of the brittle sacrificial sleeve 2 and the limited bonding between it and the hollow grouting anchor rod 1 together constitute a stress sensing and control interface. The stress sensing and control interface is configured to: serve as a force transmission medium to maintain support stiffness under normal load conditions; release energy through the controllable fracture of the brittle sacrificial sleeve 2 itself under overload conditions; and achieve penetration bonding and functional repair of the fractured area under the action of grouting slurry.

[0027] As a preferred embodiment, the brittle sacrificial sleeve 2 is made of porous low-grade cement-based material or controllable fracture composite material, with an internal directional or random interconnected pore structure and a porosity controlled between 15% and 30%. The interconnected pore structure is configured as follows: firstly, as a preset weakening path to guide the brittle sacrificial sleeve 2 to undergo controllable fracture along the pores or grain boundaries under overload; secondly, as a transmission channel for subsequent grout penetration and bonding to support self-healing function.

[0028] In this technical solution, the brittle sacrificial sleeve is made of porous low-grade cement-based material or controllable fracture composite material, with an internal directional or random interconnected pore structure and a porosity precisely controlled between 15% and 30%. This design endows the sleeve with multiple synergistic functions throughout the entire life cycle of the anchor bolt. First, the interconnected pore structure has a limited impact on the macroscopic strength of the sleeve during the normal load-bearing stage, ensuring that it maintains the initial stiffness of the support system as a uniform force transmission medium. Under overload conditions, the pore network, as a pre-set weakening path, can guide cracks to preferentially initiate and propagate along the pore walls or grain boundaries, causing the sleeve to undergo controllable fracture behavior rather than random bursting. This ensures the determinism, localization, and instantaneity of the stress shearing process, effectively avoiding the risk of uncontrollable damage to the anchoring system. Secondly, after the sleeve fractures, the interconnected pore system and newly formed cracks together form a three-dimensional, continuous permeability network. This provides an efficient transmission channel for the secondary infiltration of grout into the fractured area under capillary action or surrounding rock compaction, ensuring that the grout can fully fill the cracks and re-cement the fractured blocks into a whole. This allows for the reconstruction of an anchoring interface with significant residual strength in the decompression zone, achieving self-repair of the support function. By limiting the porosity to an optimized range of 15% to 30%, this design achieves the best balance between the normal load-bearing stiffness of the sleeve, overload fracture sensitivity, and self-repairing permeability efficiency after fracture. This allows a single material structure to orderly complete the functional sequence of stable force transmission, sensitive triggering, and efficient repair, significantly improving the reliability and self-healing ability of the anchoring system in the face of dynamic disasters in deep roadways.

[0029] As a preferred option, the brittle sacrificial sleeve 2 is made of industrial-grade porous cement-based composite material, the components of which include low-grade cement, aggregate, toughening fiber and pore-forming agent. This allows the preparation process to be based on existing materials and process systems, and has extremely high engineering and commercial feasibility. The porous structure of the brittle sacrificial sleeve 2 has been prefabricated before installation.

[0030] In this technical solution, the brittle sacrificial sleeve is made of industrial-grade porous cement-based composite material, whose components include low-grade cement, aggregate, toughening fiber and pore-forming agent, and the porous structure has been prefabricated before installation. This technical solution has the following advantages: First, the selected materials are all readily available industrial raw materials, with low cost and mature preparation processes, ensuring the economy and feasibility of the device in large-scale production. Second, the prefabrication process pre-forms directional or random interconnected pore structures, avoiding the influence of human factors on porosity and distribution uniformity during on-site construction, ensuring the consistency and controllability of the sleeve's mechanical properties and fracture behavior. Third, the introduction of toughening fibers effectively improves the brittle fracture characteristics of cement-based materials, making the sleeve's fracture process under overload more orderly and stable, avoiding secondary impacts on the anchoring system from sudden brittle disintegration. Finally, the prefabricated porous structure provides the sleeve with stable weakening paths and penetration channels, making the sequence of load-bearing, fracture, and self-repair functions entirely determined by the intrinsic properties of the material and the pre-designed structure, without relying on complex mechanical or electronic components, significantly improving the system's overall passive reliability. Overall, this design, while meeting functional requirements, achieves a high degree of synergy in material selection, manufacturing processes, and performance control, possessing excellent engineering adaptability and commercialization prospects.

[0031] In order to accurately deploy the active stress relief and repair function to the most needed locations, specific preset locations are determined based on the boundaries of high stress concentration zones or plastic zones in the roadway, as determined by numerical simulation or field measurements. As shown in formula (1); (1); In the formula, The coefficients related to lithology and support density (0.3~1.0); The deformation modulus of the surrounding rock; The borehole diameter; This represents the uniaxial compressive strength of the surrounding rock. This design aims to precisely deploy the active decompression-repair function at the locations where it is most needed.

[0032] The stress-relieving and self-healing anchor bolt device based on a porous brittle structure provided by this invention mainly consists of a hollow grouting anchor bolt body, a brittle sacrificial sleeve fitted into a specific section of the bolt body, a tray, and a fastening nut. The brittle sacrificial sleeve is made of a low-strength, porous material that can be penetrated and cemented by grout. It is connected to the bolt body through limited adhesive force, forming a core stress-sensing and control interface. Compared to the brittle fracture failure of traditional anchor bolts due to excessive stiffness under impact loads, this device precisely configures the uniaxial compressive strength of the sleeve to 20% to 50% of the bolt body's yield strength, maintaining the initial support stiffness required by the composite anchor body during normal load-bearing stages, thus ensuring effective constraint on surrounding rock deformation. The working principle of this device is a fully passive intelligent cycle of load bearing, pressure relief, and repair: Under normal loads, the sleeve acts as a uniform force transmission medium; when large deformation of the surrounding rock or impact loads cause a sudden increase in stress in the rod, the sleeve, due to its low material strength and high brittleness, undergoes controlled fracture, instantly cutting off the local rigid stress transmission path and forming a mechanically flexible zone, thereby releasing overload stress and deformation energy and protecting the rod from brittle fracture. This fracture process is completed within milliseconds, fundamentally realizing a leap from passive resistance to active pressure relief protection mechanism. More importantly, this device deeply couples the porous structure of the brittle sacrificial sleeve with the flow characteristics of the grouting slurry. The pre-designed interconnected pore structure inside the sleeve acts as a weakening path to guide the orderly propagation of cracks before fracture, ensuring the controllability and predictability of the fracture behavior. After fragmentation, the inherent porous structure of the sleeve and the resulting crack network provide secondary penetration channels for the grout. The grout penetrates and cements the fragments under capillary action, rebuilding the anchoring interface primarily based on mechanical interlocking, thus achieving self-repair of the support function. This mechanism ensures that the anchored section after pressure relief is not permanently failed, but can autonomously rebuild a composite anchor body with significant residual strength. This effectively overcomes the fundamental defect in existing technologies where pressure relief and anchoring functions are mutually exclusive, achieving the goal of long-term support without collapse under pressure relief. Furthermore, the structural design of this device fully considers the convenience and economy of engineering implementation. The brittle sacrificial sleeve uses common engineering materials such as cement-based materials. Its structural design and construction technology are highly compatible with existing anchor systems, requiring no changes to the mainstream operating procedures or the addition of complex external mechanisms. While ensuring conventional static load anchoring performance, it embeds intelligent pressure relief capabilities into the support system. The entire device does not incorporate complex mechanical components or electronic sensing elements. Its stress sensing, controllable fracture, and self-repair functions are passively achieved through the intrinsic properties of materials and structural design, resulting in extremely high reliability, durability, and environmental adaptability.

[0033] This device can achieve an organic unity of instantaneous and controllable decompression behavior and recoverable anchoring function. It has good engineering adaptability and feasibility for promotion, and provides a new support equipment solution with simple structure, reliable performance and self-healing capability for surrounding rock control in deep tunnels, high-stress soft rock and areas prone to rockbursts.

[0034] This invention also provides a pressure relief and self-healing anchoring method based on a porous brittle structure, employing a pressure relief and self-healing anchor bolt device based on a porous brittle structure, comprising the following steps: S1: Drilling operation; Drilling at the predetermined support location in the surrounding rock of the tunnel; S2: Insert anchoring agent; Insert anchoring agent 7 into the bottom of the borehole. Preferably, anchoring agent 7 is resin anchoring agent or cement anchoring agent, and ensure that the resin anchoring agent or cement anchoring agent does not cover the grout outlet 6 of the hollow grouting anchor rod body 1. S3: Install the anchor bolt device; insert the anchor bolt device into the borehole. During installation, the anchoring agent 7 is stirred by rotating and pushing the hollow grouting anchor bolt body 1 to complete the end anchoring of the anchoring section of the hollow grouting anchor bolt body 1. S4: Grouting; Grouting is performed along the entire length of the hollow grouting anchor rod 1 through the inner hole channel, so that the grout 5 fills the annular space between the hollow grouting anchor rod 1 and the borehole wall, and wraps the brittle sacrificial sleeve 2. S5: Install the tray and fasten the nut; after the grout reaches the predetermined strength, install the tray 3 and fasten the nut 4 in sequence at the exposed end of the hollow grouting anchor rod 1, and apply pre-tightening force. The fasten nut 4 serves to apply pre-tightening force and lock and fix the anchor rod. S6: Normal load bearing and stress perception (first stage); In the normal load bearing stage, the brittle sacrificial sleeve 2 wrapped by the grout 5, the grout 5 and the hollow grouting anchor rod 1 are used to form a composite anchor body with initial design stiffness, wherein the brittle sacrificial sleeve 2 serves as a uniform stress transmission medium. S7: Brittle Fracture and Active Pressure Relief (Second Stage); When the stress of the hollow grouting anchor rod 1 increases sharply due to large deformation of the surrounding rock or impact load, and the high circumferential tensile stress is transferred to the brittle sacrificial sleeve 2 through the bonding interface, the brittle sacrificial sleeve 2, due to its low material strength and high brittleness, will preferentially generate and expand cracks in the internal pores or defect tips, and then undergo macroscopic fracture; This macroscopic fracture process actively cuts off the rigid stress transmission path between the hollow grouting anchor rod 1 and the external grout 5 in the section covered by the brittle sacrificial sleeve 2 within a short time (millisecond time), forming an instantaneous mechanical flexibility zone, allowing the hollow grouting anchor rod 1 to generate limited plastic tension or to undergo micro-slippage with the grout 5, so as to release overload stress waves and deformation energy, thereby effectively protecting the rod from overload breakage; S8: Grout Infiltration and Functional Self-Repair (Third Stage); The crack network and inherent pores generated after the brittle sacrificial sleeve 2 fractures are connected with the grout that has not yet fully solidified or is flowing due to subsequent surrounding rock compaction, becoming the preferred channel for secondary grout infiltration; the grout seeps into the cracks under capillary action or slight pressure, re-cementing the fragments, and forming a new bonding interface mainly based on mechanical interlocking between the surface of the hollow grouting anchor rod 1 and the fragments, thereby rebuilding a composite anchor body with residual strength after pressure relief, realizing partial or most of the restoration of the support function, so as to effectively maintain the long-term stability of the roadway.

[0035] In S8, the self-healing function of the grout mainly relies on the natural solidification process of the grout after the initial grouting. Specifically, in the initial full-length grouting immediately after the installation of the anchor bolt device, the grout still has a certain fluidity and permeability in the early stage of solidification (such as during the period from initial setting to final setting). When the brittle sacrificial sleeve 2 fractures due to a sudden change in the surrounding rock load within this time window, the grout that has not yet fully solidified can naturally seep into the cracks and pores of the sleeve under the action of capillary force, chemical shrinkage, or minor surrounding rock compaction, and then continue to solidify to achieve cemented repair. As a supplementary implementation of this method, when the brittle sacrificial sleeve fractures only after the initial grouting has completed its final setting, a low-pressure, small-dose secondary compensation grouting can be performed using the inner hole channel of the hollow grouting anchor bolt to activate the repair function.

[0036] As a preferred option, the critical stress at which the brittle sacrificial sleeve 2 undergoes controlled fracture is... This is the key to its sensing and triggering functions. The threshold is precisely designed through the combination of its material mechanical properties and geometric dimensions. The following process must be met to ensure the orderliness and reliability of its behavior. Specifically, in S7, the critical stress at which the brittle sacrificial sleeve 2 undergoes controllable fracture is obtained according to formula (2). and ensure ; (2); In the formula, The shape factor (0.5~1.2) is related to the sleeve structure and process. The tensile strength of the sleeve base material; For the sleeve wall thickness; denoted as the average radius of the sleeve; p is the porosity of the sleeve; m is the porosity influence index (approximately 1.5~2.5). The yield strength of the rod. This refers to the bonding strength of the resin anchoring agent.

[0037] In this technical solution, the critical stress of the brittle sacrificial sleeve is... The quantitative model and its dual constraints, by unifying material strength, geometric dimensions, porosity, and process factors into a multi-parameter coupled expression, achieve precise presetting and flexible adjustment of the sleeve trigger threshold; constraints From the design source, an orderly functional sequence is ensured that the sleeve breaks before the rod yields and without damaging the anchoring interface; The study reveals the nonlinear regulation of porosity on macroscopic strength, balancing normal load-bearing stiffness with overload triggering sensitivity. This model provides an efficient and reliable quantitative basis for the standardized parameter design of sleeves and their adaptation to various engineering scenarios.

[0038] As a preferred option, total energy dissipation It is a key indicator for measuring its impact resistance and stress relief performance, and can be decomposed into material fracture energy. and initial frictional slip energy after fragmentation Through optimal material and structural design and maximization This achieves efficient absorption of impact energy; in S7, the total energy dissipation during the fracture process of the brittle sacrificial sleeve 2 is obtained according to formula (3). ; (3); In the formula, The fracture toughness of the sleeve material; This represents the total area of ​​newly formed cracks; To match the slip velocity The relevant coefficient of kinetic friction, For displacement with fragmentation Changing interface normal stress; The circumference of the rod is The characteristic slip is denoted as .

[0039] In this technical solution, the total energy dissipation during the brittle sacrificial sleeve fragmentation process is... The computational model decomposes the total energy dissipation into material fracture energy. Frictional slip energy after fragmentation This study, comprising two parts, comprehensively quantifies the energy absorption mechanism of the sleeve from crack initiation and propagation to fragment slip friction. The model reveals that, in addition to the intrinsic fracture toughness of the material, interfacial friction slip of the fragments under confining pressure after sleeve fragmentation is also a significant source of energy dissipation. This provides a theoretical basis for improving friction energy dissipation efficiency by optimizing the sleeve's pore structure and fragment gradation. Using this quantitative evaluation tool, the impact relief performance of the sleeve under different material formulations and structural parameters can be predicted, compared, and optimized to ensure that it can fully absorb and dissipate overload energy during dynamic disasters, effectively protecting the rod from fracture.

[0040] As a preferred option, the long-term residual strength of the composite anchor body formed after self-healing is... This is the ultimate indicator for evaluating repair efficacy and long-term safety. By optimizing the slurry properties and the initial pore structure of the sleeve, it is possible to... Reaching initial strength 30%~60%. In S8, the long-term residual strength of the composite anchor solid formed after self-repair is obtained according to formula (4). ; (4); In the formula, It contributes to the chemical bonding strength of slurry hydration products between fragments. The percentage of cracks effectively filled by grout; The strength contribution of the mechanical interlocking between the fragments and the rod is related to the surface roughness of the rod and the gradation of the fragments. This is a permanent porosity that cannot be restored.

[0041] In this technical solution, the long-term residual strength of the self-healing composite anchor body is... The predictive model decomposes the residual anchoring force after repair into four independent and quantifiable factors: the contribution of grout chemical bonding, crack filling efficiency, fragment mechanical interlocking contribution, and permanent porosity loss. This comprehensively characterizes the contribution weights of each key stage in the self-healing process to the final recovery of support performance. The model reveals an engineering path to improve self-healing efficiency: optimizing grout rheology and permeability to increase the crack filling percentage. The mechanical interlocking effect is enhanced by adjusting the gradation of sleeve fragments and the surface roughness of the rod. And by improving the adhesion between slurry hydration products and the matrix to enhance the contribution of chemical bonding. This quantitative assessment tool provides clear theoretical guidance and evaluation standards for grout ratio optimization, sleeve pore structure design, and construction process improvement, ensuring that the anchoring system can reliably recover to the residual support strength required for long-term stability after depressurization.

[0042] As a preferred option, the completion time of the slurry self-healing process It is an important engineering parameter, which depends on the grout rheology, crack width, seepage driving force, and ambient temperature. It must be ensured during the design process. Much shorter than the secondary stabilization time required for the roadway; specifically, in S8, the completion time of the slurry self-healing process is obtained according to formula (5). ; (5); In the formula, The viscosity of the slurry; Characteristic penetration depth; The surface tension of the slurry; The contact angle between the slurry and the sleeve material; The average crack width; This refers to the solidification time of the slurry.

[0043] In this technical solution, the slurry self-healing completion time The estimation model quantifies the kinetic characteristics of the repair process into a synergistic function of multiple factors, including slurry viscosity, surface tension, wettability, crack width, and setting time, revealing the influence of each parameter on repair efficiency. This model provides a quantitative design basis for optimizing slurry formulation to shorten the repair cycle and matching the secondary stabilization time window of the surrounding rock in the roadway, ensuring that the self-healing function can be reliably completed within the allowable time range of the project.

[0044] This method realizes a fully passive intelligent cycle mechanism for load bearing, pressure relief, and repair. This mechanism consists of three consecutive and automatically triggered stages, which do not require any external signal excitation or human intervention. It is completed autonomously entirely by the synergistic effect of material constitutive relations and structural design.

[0045] At the material design level, the brittle sacrificial sleeve incorporates a design concept that decouples micro / nano-scale defect control from macroscopic mechanical properties. By precisely controlling the type, particle size distribution, and dosage of the pore-forming agent, a multi-level interconnected pore system ranging from micrometers to millimeters is pre-established within the sleeve matrix. This pore system has limited impact on the macroscopic load-bearing strength of the sleeve under normal static load conditions, ensuring that it can serve as a uniform stress transfer medium during normal service, maintaining the initial stiffness required by the composite anchor. However, when the surrounding rock stress increases sharply and exceeds a preset threshold, the aforementioned multi-level pores become a pre-defined weakening path for preferential crack initiation and directional propagation, guiding the sleeve to undergo orderly and controllable fragmentation behavior, rather than random bursting. Thus, a controllable correlation and precise triggering from the material's microstructural characteristics to the system's macroscopic pressure relief function is achieved.

[0046] To facilitate a deeper understanding of the core innovative mechanism of this invention, the coupling system of the brittle sacrificial sleeve and the grouting slurry can be likened to a functional sequence generator embedded in the anchoring system, conceptually equivalent to an electromechanical system with switching and memory functions. The controllable fragmentation behavior of the brittle sacrificial sleeve under overload stress is analogous to the fuse blowing in a circuit, cutting off the rigid stress transmission path within milliseconds and providing instantaneous circuit protection for the anchor rod. The subsequent process of the grout penetrating the fracture network and completing secondary cementation and solidification, driven by capillary action or surrounding rock compaction, is analogous to the circuit's self-repair mechanism, reconnecting the force transmission path through the material's own flow and cementation properties, achieving limited restoration of the support function. This electromechanical analogy reveals the core principle of this invention: simplifying the complex support dynamics and energy regulation problems of deep tunnels into a fully passive state machine model uniquely determined by the material constitutive relationship and the pre-set structure. This allows the anchoring system to reliably switch between three states: stable bearing, active pressure relief, and autonomous repair, without relying on any electronic sensors or external control commands.

[0047] This invention provides a pressure relief and self-healing anchoring method based on porous brittle structures. It organically integrates drilling, anchoring agent loading, anchor bolt installation, initial grouting, tray fastening, and subsequent service stages of normal load-bearing, brittle fracture, and grout self-healing into a unified continuous process. This achieves systematic control over the entire process from construction and installation to functional evolution. Moreover, the entire process does not require any external signal triggering or manual intervention and is completed autonomously entirely by relying on the synergistic effect of material constitutive relations and structural design.

[0048] Compared to traditional anchor bolt construction methods that only focus on the formation of anchoring force during the installation phase, this method explicitly installs a brittle sacrificial sleeve along with the hollow grouting anchor bolt body. Full-length grouting ensures the sleeve is fully encapsulated, thus pre-constructing the stress sensing and control interface during the construction phase. This interface, as an embedded stress sensing and response unit, can achieve precise triggering based on a preset strength threshold. When the surrounding rock of the tunnel undergoes large deformation or impact loads during subsequent service, the sleeve requires no external signal excitation; it can initiate the fracture and pressure relief procedure solely based on its own material constitutive relationship and stress state. This achieves fully passive intelligent protection integrating sensing, decision-making, and execution, greatly improving the timeliness and reliability of the support system under extreme conditions.

[0049] The core advantage of the brittle fragmentation and active stress relief mechanism achieved by this method lies in the ordered and controllable nature of the fragmentation behavior. Because the brittle sacrificial sleeve has a pre-designed directional or random interconnected pore structure, under overload stress, cracks preferentially initiate and propagate along pre-designed weakening paths such as pores or grain boundaries. This controllable fragmentation behavior can instantly sever local rigid force transmission paths, forming a temporary flexible zone, thereby effectively releasing abrupt loads and deformation energy from the surrounding rock and protecting the rod from brittle fracture. This method cleverly utilizes the principles of material fracture mechanics and structural weak surface design, transforming the passive failure of traditional anchor bolts under impact loads into an active and ordered energy release process.

[0050] The most significant innovation of this method lies in the grout penetration and self-repair process it achieves. Existing pressure-relief anchors or devices often permanently lose their support function once triggered, while this method fully utilizes the flow and cementation characteristics of the grout after the sleeve breaks apart. The fracture network formed after the sleeve breaks provides a natural secondary penetration channel for the grout. Driven by capillary force or surrounding rock compaction, the grout can spontaneously penetrate into the fracture space, re-cementing the fragmented blocks into a whole. This process allows the support system to recover significant residual strength after pressure relief, and the repaired composite anchor body forms a new bonding interface, primarily based on mechanical interlocking, between the surface of the hollow grout anchor and the fragments.

[0051] This method is simple to implement and has low implementation costs. It fundamentally changes the inherent defect of the irreversible function of traditional pressure relief support, and endows the anchoring system with the ability to self-repair and regenerate after experiencing extreme loads, providing a reliable technical guarantee for the long-term stability of deep roadways throughout their entire life cycle.

Claims

1. A pressure-relieving and self-healing anchor bolt device based on a porous brittle structure, the anchor bolt device comprising a hollow grouting anchor bolt body (1), a tray (3), and a fastening nut (4), wherein the hollow grouting anchor bolt body (1) comprises an exposed section and an embedded section, and the tray (3) and the fastening nut (4) are sequentially installed on the exposed section of the hollow grouting anchor bolt body (1); characterized in that, It also includes brittle sacrificial sleeves (2); The brittle sacrificial sleeve (2) is fitted onto a predetermined specific position on the embedded section of the hollow grouting anchor rod (1). The brittle sacrificial sleeve (2) is made of a low-strength, porous material that can be penetrated and cemented by grout, and is connected to the hollow grouting anchor rod (1) by a limited adhesive force. The uniaxial compressive strength of the brittle sacrificial sleeve (2) is configured to be 20% to 50% of the yield strength of the hollow grouting anchor rod (1), and the porous structure of the brittle sacrificial sleeve (2) and the limited bonding between it and the hollow grouting anchor rod (1) together constitute a stress sensing and control interface. The stress sensing and control interface is configured to: serve as a force transmission medium to maintain support stiffness under normal load conditions; release energy through the controllable fracture of the brittle sacrificial sleeve (2) itself under overload conditions; and achieve penetration bonding and functional repair of the fractured area under the action of grouting slurry.

2. The pressure relief and self-healing anchor bolt device based on a porous brittle structure according to claim 1, characterized in that, The brittle sacrificial sleeve (2) is made of porous low-grade cement-based material or controllable fracture composite material, and has an internal directional or random interconnected pore structure with a porosity controlled between 15% and 30%. The interconnected pore structure is configured as follows: firstly, as a preset weakening path to guide the brittle sacrificial sleeve (2) to undergo controllable fracture along the pores or grain boundaries under overload; secondly, as a transmission channel for subsequent grout penetration and bonding to support self-healing function.

3. The pressure relief and self-healing anchor bolt device based on a porous brittle structure according to claim 1, characterized in that, The brittle sacrificial sleeve (2) is made of industrial-grade porous cement-based composite material, the components of which include low-grade cement, aggregate, toughening fiber and pore-forming agent; the porous structure of the brittle sacrificial sleeve (2) has been prefabricated before installation.

4. The pressure relief and self-healing anchor bolt device based on a porous brittle structure according to claim 1, characterized in that, Based on numerical simulations or field measurements, specific locations are determined by setting up predetermined positions at the boundaries of high-stress concentration zones or plastic zones in the roadway. As shown in formula (1); （1）； In the formula, A coefficient related to lithology and support density; The deformation modulus of the surrounding rock; The borehole diameter; It represents the uniaxial compressive strength of the surrounding rock.

5. A method for pressure relief and self-healing anchoring based on a porous brittle structure, employing a pressure relief and self-healing anchor device based on a porous brittle structure as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1: Drilling holes at the predetermined support location in the surrounding rock of the tunnel; S2: Insert anchoring agent into the bottom of the borehole (7); S3: Insert the anchor bolt device into the borehole. During installation, the anchoring agent (7) is stirred by rotating and pushing the hollow grouting anchor bolt body (1) to complete the end anchoring of the hollow grouting anchor bolt body (1). S4: Grouting is carried out along the entire length of the hollow grouting anchor rod (1) through the inner hole channel, so that the grout (5) fills the annular space between the hollow grouting anchor rod (1) and the borehole wall, and wraps the brittle sacrificial sleeve (2). S5: After the grout reaches the predetermined strength, install the tray (3) and fastening nut (4) in sequence at the exposed end of the hollow grouting anchor rod (1), and apply pre-tightening force; S6: During the normal bearing stage, the brittle sacrificial sleeve (2) wrapped by the grout (5), the grout (5) and the hollow grouting anchor rod (1) are used to form a composite anchor body with initial design stiffness, wherein the brittle sacrificial sleeve (2) serves as a uniform stress transmission medium. S7: When the stress of the hollow grouting anchor rod (1) increases sharply due to large deformation of the surrounding rock or impact load, and the high circumferential tensile stress is transferred to the brittle sacrificial sleeve (2) through the bonding interface, the brittle sacrificial sleeve (2) has low material strength and high brittleness, and cracks are preferentially generated and extended at the internal pores or defect tips, which then lead to macroscopic fragmentation. This macroscopic fragmentation process cuts off the rigid stress transmission path between the hollow grouting anchor rod (1) and the external grout (5) in the section covered by the brittle sacrificial sleeve (2) in a short time, forming an instantaneous mechanical flexibility zone, allowing the hollow grouting anchor rod (1) to generate limited plastic tension or to undergo micro-slip between it and the grout (5) in order to release overload stress waves and deformation energy. S8: The crack network and inherent pores generated after the brittle sacrificial sleeve (2) is broken are connected with the grout that has not yet fully solidified or is flowing due to subsequent compaction of the surrounding rock, becoming the preferred channel for secondary infiltration of the grout; the grout seeps into the crack under capillary action or small pressure, re-cements the fragments, and forms a new bonding interface between the surface of the hollow grouting anchor rod (1) and the fragments, mainly based on mechanical interlocking, thereby rebuilding a composite anchor body with residual strength and realizing partial or most of the restoration of the support function.

6. The method for stress relief and self-healing anchoring based on a porous brittle structure according to claim 5, characterized in that, In S7, the critical stress at which the brittle sacrificial sleeve (2) undergoes controlled fracture is obtained according to formula (2). and ensure ; （2）； In the formula, The shape factor is related to the sleeve structure and manufacturing process; The tensile strength of the sleeve base material; For the sleeve wall thickness; denoted as the average radius of the sleeve; p is the porosity of the sleeve; m is the porosity influence index. The yield strength of the rod. This refers to the bonding strength of the resin anchoring agent.

7. The method for stress relief and self-healing anchoring based on a porous brittle structure according to claim 6, characterized in that, In S7, the total energy dissipation during the fragmentation process of the brittle sacrificial sleeve (2) is obtained according to formula (3). ; （3）； In the formula, The fracture toughness of the sleeve material; This represents the total area of ​​newly formed cracks; To match the slip velocity The relevant coefficient of kinetic friction, For displacement with fragmentation Changing interface normal stress; The circumference of the rod is The characteristic slip is denoted as .

8. The method for stress relief and self-healing anchoring based on a porous brittle structure according to claim 7, characterized in that, In S8, the long-term residual strength of the composite anchor solid formed after self-healing is obtained according to formula (4). ; （4）； In the formula, It contributes to the chemical bonding strength of slurry hydration products between fragments. The percentage of cracks effectively filled by grout; Contributes to the strength of the mechanical interlocking between the fragments and the rod; This is a permanent porosity that cannot be restored.

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