A method for controlling floor heave in a roadway by continuous floor weakening and stress diversion

Abstract

This invention discloses a method for controlling floor heave in roadways through continuous floor weakening and stress bias, belonging to the field of coal mining technology. The method includes: accurately locating the key bearing layer where the principal stress of the floor is concentrated as the target weakening layer through multi-field coupling analysis of self-weight stress, tectonic stress, and mining-induced stress; designing cutting parameters based on fracture mechanics and blast wave principles, and arranging multiple rows of continuous cutting boreholes along the roadway direction; using directional shaped charge blasting to form a continuous weakening structure with a penetrating fracture zone; using the weakened structure as a stress regulation interface to guide the principal stress to transfer to the deeper parts of the floor, forming a low-stress protection zone in the shallow part; and dynamically optimizing the cutting parameters through continuous monitoring of floor displacement, stress, and heave rate to construct a closed-loop control system for the entire process. This invention changes the traditional passive support approach, fundamentally solving the problem of repeated deformation of floor heave in deep, high-stress roadways, and is applicable to floor stability control throughout the entire roadway excavation and mining cycle.

Description

Technical Field

[0001] This invention belongs to the field of coal mining technology, specifically relating to a method for controlling roadway floor heave through continuous floor weakening and stress bias. Background Technology

[0002] With the increasing depth of coal mining, the surrounding rock of roadways is subjected to a complex stress environment of high stress, strong disturbance, and repeated loading and unloading under the superimposed effects of repeated mining of multiple coal seams and the disturbance of working face mining. Especially in roadways with long service life and frequent mining impacts, such as those in the uphill and downhill sections of the mining area and the uphill section of the return airway, the floor surrounding rock is prone to compression, flexure, and shear slip deformation under high-level principal stress, ultimately inducing strong floor heave. Existing roadway floor heave control technologies mainly focus on strengthening support, repeated floor pulling, or local reinforcement. These methods often only work on the surface or shallow surrounding rock of the floor and fail to fundamentally change the stress transmission path of the deep rock mass of the floor. Under the condition of repeated disturbance of multiple coal seams, the floor surrounding rock will continue to be subjected to high-level principal stress. Stress compression leads to the continuous expansion of the plastic zone of the floor, resulting in repeated floor heave and a vicious cycle of floor pulling, re-heave, and re-repair, leading to high maintenance costs and significant safety risks. In recent years, existing floor control technologies for roadway floor heave under high stress and strong disturbance conditions have mainly adopted methods such as floor treatment, floor reinforcement, or local blasting to weaken the floor. These methods aim to suppress floor deformation by improving the local bearing capacity of the floor or weakening the strength of the shallow surrounding rock. However, these methods are mostly passive reinforcement or local treatment, and it is difficult to effectively change the principal stress transmission path of the deep rock mass of the floor. Under the repeated mining and strong disturbance of multiple coal seams, the principal stress of the floor continues to concentrate on the roadway floor, causing the plastic zone of the floor to expand continuously, and the floor heave problem to occur repeatedly, resulting in limited long-term control effects.

[0003] Patent CN121111370A discloses a method for controlling floor heave in gob-side retention tunnels based on stress isolation and diversion through blasting weakening of the floor slab. Step S1: Obtain the dynamic evolution characteristics of the principal stress of the floor slab throughout the entire cycle under typical geological conditions, and derive the dynamic evolution law of the triaxial principal stress state of the floor slab; Step S2: Construct a mechanical model of the floor slab horizontal beam under the action of triaxial principal stress, and obtain the driving mechanism and degree of influence of the triaxial principal stress state on the deformation and failure of the floor slab at different layers in the gob-side retention tunnel; Step S3: Based on the influence law of the triaxial principal stress state on the amount of floor heave, analyze the influence law of floor slab weakening on the amount of floor heave in the gob-side retention tunnel, and obtain the mechanism of action of floor slab weakening on the control of floor heave in the gob-side retention tunnel; Step S4: Based on the mechanism of action of floor slab weakening on the control of floor heave in the gob-side retention tunnel, perform deep blasting weakening or shallow grouting reinforcement on the surrounding rock, significantly reducing the heavy workload brought about by the traditional repair and treatment of floor heave in gob-side retention tunnels. The aforementioned method uses localized shaped charge blasting to construct weakened zones, but it lacks a clear standard for controlling fracture penetration. This leads to discontinuous sections within the weakened zones, resulting in stress flow around the fracture. Therefore, those skilled in the art urgently need to address these technical issues. Summary of the Invention

[0004] To solve the above-mentioned technical problems, this invention determines the borehole spacing through fracture mechanics calculations, ensuring that the weakened zone is fully continuous, forming a complete stress barrier interface, and completely avoiding secondary stress concentration.

[0005] This invention discloses a method for controlling roadway floor heave through continuous weakening and stress bias of the floor slab, comprising the following steps:

[0006] S1: Identification of stress environment of floor plate and determination of target weakening layer: Based on the roadway burial depth, ground stress test results and mining influence conditions, analyze the principal stress distribution characteristics of the roadway floor plate under the disturbance of tunneling and mining, and determine the key bearing layer in the floor plate that bears the high level of principal stress concentration, as the target layer for floor plate cutting and weakening.

[0007] S2: Design of bottom cutting weakening parameters: Based on the burial depth, lithology and stress state of the target weakening layer, determine the depth range, bottom cutting length, cutting spacing and continuous arrangement of the bottom cutting weakening structure so that the bottom cutting weakening structure can cover the main stress transmission path of the bottom plate.

[0008] S3: Bottom-cutting borehole arrangement: Multiple rows of bottom-cutting boreholes are arranged along the direction of the roadway on the bottom plate. Each row of bottom-cutting boreholes is arranged continuously along the roadway axis. A preset distance is maintained between adjacent bottom-cutting boreholes so that multiple bottom-cutting boreholes form a continuous bottom-cutting weakening zone in space.

[0009] S4: Artificially manufactured bottom-cutting weakening structure: Through directional energy-concentrating blasting, bottom-cutting operations are carried out in the bottom-cutting borehole to form a continuous bottom-cutting weakening structure with a certain thickness and extension length in the target weakening layer of the bottom plate;

[0010] S5: Stress bias and continuous weakening coordinated control: Using the continuous weakening structure as a stress control interface, actively change the original bearing structure and main stress transmission path of the floor plate, guide the high-level main stress that was originally concentrated towards the roadway floor plate to be biased and redistributed along the continuous weakening structure, so that the main stress of the floor plate changes from a concentrated state to a dispersed transmission state.

[0011] S6: Monitoring and Parameter Optimization of Floor Heave Control Effect: During the service period of the roadway, the displacement, stress changes and floor heave development of the floor plate are continuously monitored. Based on the monitoring results, the floor weakening parameters are adaptively optimized and adjusted to achieve long-term stable control of the roadway floor plate.

[0012] By adopting the above technical solutions, a closed-loop control system covering the entire process from floor stress environment identification to dynamic parameter optimization was constructed. This system changes the traditional approach of passively increasing surrounding rock strength through support, and by actively cutting off the principal stress transmission path and guiding stress redistribution, it fundamentally solves the industry problem of repeated floor heave and high maintenance costs in deep, high-stress roadways. This method covers the entire cycle of roadway excavation and mining disturbances, and is suitable for both preventative control of newly excavated roadways and treatment of deformed roadways. It achieves comprehensive and long-term floor stability control. Compared with traditional grouting and anchor bolt support methods, the floor heave rate can be reduced, and the roadway maintenance cycle can be extended.

[0013] Furthermore, in step S1, when analyzing the distribution characteristics of principal stress in the roadway floor, the tectonic stress components obtained by testing the self-weight stress corresponding to the roadway burial depth and the ground stress, as well as the disturbance stress formed by the superposition of repeated mining of multiple coal seams and working face mining disturbance, are used to determine the key bearing layer in the floor that bears the high level of principal stress concentration as the core path layer for principal stress transmission in the deep rock mass of the floor.

[0014] By adopting the above technical solution and integrating multi-field coupling analysis of self-weight stress, tectonic stress, and mining disturbance stress, the key bearing layer with concentrated principal stress in the base plate can be accurately located. This avoids the problems of ineffective cutting or over-cutting caused by blindly selecting weakening layers in traditional bottom-cutting methods. By quantifying the superimposed influence of different stress sources on the base plate, the core path of principal stress transmission can be accurately identified, allowing subsequent bottom-cutting operations to directly target the root cause of stress concentration. This significantly improves bottom-cutting efficiency and energy utilization. Compared with experience-based layer selection, the weakening effect is enhanced, while unnecessary drilling and blasting operations are reduced, lowering construction costs and minimizing additional damage to the surrounding rock.

[0015] Furthermore, in step S2, the depth range of the bottom-cutting weakening structure covers the full thickness of the target weakening layer, the bottom-cutting length matches the advance step distance of the roadway excavation face or the length of the mining-affected section, the cutting spacing is determined based on the critical value of fracture penetration calculated by the principle of fracture mechanics and superposition of explosion waves, and the continuous arrangement is a linear or polygonal continuous structure without interruption along the roadway direction.

[0016] By adopting the above technical solution, based on the burial depth, lithology, and stress state of the target weakened layer, the cutting parameters are quantified using the principles of fracture mechanics and explosive wave superposition. This ensures that the weakened structure depth covers the full thickness of the target layer, the length matches the mining-affected section, and the cutting spacing is precisely controlled within the critical value for fracture penetration. This design completely solves the problems of discontinuous weakened zones and stress control failure caused by traditional empirical parameter methods. It enables the weakened zone to completely cut off the principal stress transmission path, and adapts to different roadway cross-sections and stress distribution characteristics with linear or polygonal layouts, significantly improving the accuracy and adaptability of stress control and increasing the fracture penetration rate of the weakened zone.

[0017] Furthermore, in step S3, the number of rows of bottom-cutting boreholes is determined according to the roadway width and the distribution range of principal stress in the floor plate, and the preset spacing between adjacent bottom-cutting boreholes ensures that the cracks of adjacent shaped charge blasting holes can be interconnected.

[0018] By adopting the above technical solution, the number of borehole rows is determined according to the roadway width and the distribution range of principal stress. Pre-set borehole spacing ensures that adjacent shaped charge blasting fractures are interconnected, forming a continuous weakened zone without interruption along the roadway direction. Compared to single-row boreholes or wide-spaced arrangements, multiple rows of continuous boreholes can more comprehensively cover the stress concentration areas of the floor slab, avoiding point-like floor heaves caused by localized stress residue. Simultaneously, precise control of the borehole inclination angle and depth ensures that the energy focusing direction is strictly directed towards the target weakened layer, further enhancing the energy focusing effect and ensuring uniform mechanical properties of the weakened zone, resulting in more stable stress isolation and guiding effects.

[0019] Furthermore, in step S4, the directional shaped charge blasting adopts a shaped charge structure, with the shaped charge direction pointing towards the target weakened layer deep in the bottom plate. The continuous bottom-cutting weakened structure formed after the blasting is a low-strength rock mass area with a through-fracture zone.

[0020] By adopting the above technical solution and using a directional shaped charge structure, the explosive energy is focused on the target weakened layer through the shaped charge hood. The energy utilization rate is improved compared with ordinary blasting. After blasting, a low-strength rock mass area with penetrating fracture zones is formed, the rock mass integrity coefficient is reduced to below 0.3 and the uniaxial compressive strength is reduced. This structure effectively blocks the principal stress transmission path and avoids excessive damage to the shallow surrounding rock of the roadway caused by ordinary blasting. It achieves a balance between precise energy utilization and surrounding rock protection. Compared with the traditional bottom cutting method, the amount of explosive charge is reduced and the vibration velocity of the surrounding rock is controlled within 1.5 cm / s, which greatly reduces the negative impact on the stability of the roadway.

[0021] Furthermore, in step S5, the stress deflection and redistribution are achieved through the stress barrier and guiding effect of the continuously weakened structure, forcing the original horizontal structural stress to transfer to a deeper part of the floor, forming a low-stress protection zone in the shallow area of ​​the roadway floor.

[0022] By adopting the above technical solution, the stress isolation and guiding effect of the continuous weakening zone forces the original horizontal structural stress to transfer to a deeper part of the floor, forming a low-stress protection zone in the shallow area of ​​the roadway floor, thus reducing the stress concentration coefficient of the shallow surrounding rock. Compared with the traditional support method that only passively bears stress, this actively changes the stress transmission logic, eliminating the driving source of floor heave deformation from the root. The displacement of the shallow part of the roadway floor is reduced, and the floor heave rate is controlled within 2-5 mm / d, solving the problem of repeated treatment of floor heave in high-stress roadways.

[0023] Furthermore, in step S6, the continuous monitoring content includes floor surface displacement monitoring, floor deep stress monitoring, and floor heave rate monitoring. The adaptively optimized and adjusted bottom-cutting weakening parameters include cut spacing, blasting charge amount, and bottom-cutting depth. The adjustment cycle is determined according to the frequency of the roadway being affected by mining.

[0024] By adopting the above technical solutions, a multi-dimensional real-time monitoring and dynamic parameter optimization system was constructed. Through continuous acquisition of floor surface displacement, deep stress, and floor heave rate, combined with the frequency-based adjustment and optimization cycle of mining-induced impacts, it can accurately respond to dynamic changes in mining stress. Under the model of monthly review in weakly disturbed areas, weekly adjustment in strongly disturbed areas, and quarterly maintenance in post-mining stable areas, the slot spacing, blasting charge, and bottom cutting depth are corrected in a timely manner. This solves the problem that traditional fixed parameters cannot adapt to mining disturbances, achieves stable control of the roadway floor throughout its entire life cycle, extends the roadway's service life, and reduces maintenance costs.

[0025] Furthermore, in step S5, the mechanical mechanism by which the continuous weakened zone achieves stress deflection is verified by the planar mechanical model of the infinite elastic body-elliptical hole weakened zone. The stress field around the weakened zone is solved by the conformal transformation method of complex variable functions, proving that the principal stress traces undergo angular deflection at the tip of the weakened zone, forming a path for stress to transfer to the depth. Specifically, the continuous weakened zone formed by blasting is equivalent to an elliptical hole structure with major axis 2a and minor axis 2b on the cross section of the roadway, and the surrounding rock is an isotropic elastic body.

[0026] By introducing complex variable function theory and using the conformal transformation method to solve for the stress field distribution around the weakened zone, complex variables are defined. and mapping plane variables Through mapping function Will The outer domain of an elliptical hole on a plane is mapped as The outer region of the unit circle on the plane, where, The mapping function is constructed as follows:

[0027] ;

[0028] In the formula: R and m are constants determined by the geometry of the weakening band, reflecting the average radius and flatness of the weakening band, respectively. The distance between any point outside the standard circle and the center of the circle. Let any point outside the standard circle be the sum of the points of the circle and the center. Angle between planes;

[0029] Maximum horizontal principal stress in the far field Recorded as and vertical principal stress Recorded as Under the boundary conditions, based on the complex potential theory of elasticity, the stress component at any point around the weakened zone, the radial stress tangential stress It satisfies the following parsing relation:

[0030] ;

[0031] ;

[0032] Complex potential function The parsing expression is:

[0033] ;

[0034] The principal stress trace occurs at an angle of at its tip. The deflection creates a "low-stress protection zone" in the shallow part of the tunnel floor.

[0035] in, Let be the real part of the complex number. It is a complex function and a core function in the complex function solution method of elasticity, used to solve for stress components. For shear stress components, for The conjugate function, The pressure inside the elliptical hole. The principal stress direction angle, i.e., the angle between the maximum principal stress in the far field and the... Angle between axes.

[0036] By adopting the above technical solution and using an infinite elastic body-elliptical aperture weakened zone planar mechanical model, the stress field around the weakened zone is solved using the complex variable function conformal transformation method. This theoretically and quantitatively verifies the deflection mechanism of the principal stress traces at the tip of the weakened zone, providing a scientific basis for the stress deflection effect. This model avoids empirical errors in stress control design, enabling quantifiable prediction of the principal stress deflection angle and the range of the low-stress protection zone. It provides precise theoretical support for bottom-line parameter design, ensuring a stable and controllable stress deflection effect, and improving stress control accuracy compared to empirical design.

[0037] Furthermore, the theoretical calculation of the slit spacing is based on the principle of fracture mechanics and the superposition of explosion waves. The crack propagation radius is determined by the attenuation characteristics of the explosion stress wave and the dynamic tensile strength of the rock. The specific calculation method for the crack propagation radius is as follows:

[0038] Non-focusing direction crack radius : The tangential tensile stress generated by the explosion stress wave in the rock mass Exceeding the dynamic tensile strength of rock At that time, the fracture begins to propagate. Considering the attenuation characteristics of stress waves in the rock mass, the fracture radius in the non-focusing direction is:

[0039] ;

[0040] in: The radius of the borehole; The initial impact pressure on the borehole wall; The stress attenuation coefficient is usually taken as... ,in Poisson's ratio;

[0041] Energy-focusing direction crack radius Due to the directional focusing effect of the focused jet on energy, a focusing influence coefficient is introduced. , The radius of propagation of the main fracture in the energy-focusing direction is then corrected as follows:

[0042] .

[0043] By adopting the above technical solution, and quantifying the fracture propagation radius in both non-focused and focused directions, combined with stress wave attenuation characteristics and the focused jet influence coefficient, a precise theoretical basis is provided for borehole spacing design. Compared to traditional empirical values ​​for determining fracture range, this calculation method fully considers the influence of Poisson's ratio, dynamic tensile strength, and focused jet, accurately predicting the degree of fracture propagation under different lithologies and stress conditions. This ensures the effective formation of weakened zones and avoids problems such as discontinuous weakened zones or excessive blasting caused by errors in fracture range estimation, significantly improving the scientific rigor and accuracy of parameter design.

[0044] Furthermore, the designed borehole spacing is to achieve crack penetration between adjacent boreholes. The following conditions must be met:

[0045] .

[0046] By adopting the above technical solution, it is clear that the spacing between adjacent boreholes must meet the following requirements. This principle, by ensuring the interconnection of fractures along the energy-concentrating direction, guarantees the integrity and uniformity of the continuous weakened zone. This principle completely solves problems such as fracture discontinuity and stress-regulation interface fracture caused by excessively large hole spacing, enabling the weakened zone to form a continuous stress-barrier layer. This effectively guides the principal stress towards deeper areas, ensuring the stability and global coverage of stress regulation. Compared to traditional empirical hole spacing, this principle improves the fracture penetration rate in the weakened zone, makes the stress deflection effect more significant, and greatly enhances the reliability of base plate stability control.

[0047] The beneficial effects of this invention are as follows:

[0048] 1. This invention constructs a closed-loop control system covering the entire process from identification of the floor stress environment to optimization of dynamic parameters. It actively cuts off the main stress transmission path and guides stress redistribution, fundamentally solving the industry problem of repeated deformation of the floor heave in deep high-stress roadways. It achieves comprehensive and long-term stability control of the floor and is applicable to both preventive control of newly excavated roadways and treatment of deformed roadways.

[0049] 2. This invention, through multi-field coupling analysis integrating self-weight stress, tectonic stress, and mining disturbance stress, accurately locates the key bearing layer where the main stress of the bottom plate is concentrated, enabling the bottom cutting operation to directly target the root cause of stress concentration, significantly improving bottom cutting efficiency and energy utilization, and reducing unnecessary construction costs and additional damage to the surrounding rock;

[0050] 3. This invention uses directional energy-concentrating blasting technology and parameter design based on fracture mechanics to form a continuous weakened structure with a through fracture zone. By utilizing its stress isolation and guiding effect, it forces the principal stress to transfer to the deep part of the floor, forming a low-stress protection zone in the shallow part of the roadway. This eliminates the source of power for floor heave deformation from the root and changes the logic of traditional support passively bearing stress.

[0051] 4. This invention utilizes a multi-dimensional real-time monitoring and hierarchical adjustment parameter optimization system to accurately respond to the dynamic changes in roadways affected by mining, promptly correct the bottom-cutting weakening parameters, solve the problem that traditional fixed parameters cannot adapt to mining disturbances, achieve stable control of the roadway floor throughout its entire life cycle, extend the roadway's service life, and reduce maintenance costs. Attached Figure Description

[0052] Figure 1 This is a schematic diagram illustrating the deformation and failure characteristics of the tunnel floor slab according to the present invention.

[0053] Figure 2 This is a schematic diagram of the bottom plate stress reduction and adjustment control of the bottom drum according to the present invention;

[0054] Figure 3 This is a plan view of the tunnel along the axial direction of the present invention;

[0055] Figure 4 This is a plan view of the tunnel cross-section of the present invention.

[0056] Figure 5 This is a schematic diagram of the charge and projectile structure of the present invention;

[0057] Figure 6 This is a schematic diagram of the sealing structure of the present invention;

[0058] Figure 7 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0059] The present invention will now be described in further detail with reference to the accompanying drawings and specific preferred embodiments.

[0060] In the description of this invention, it should be understood that the terms "left side," "right side," "upper part," "lower part," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. "First," "second," etc., do not indicate the importance of the components, and therefore should not be construed as a limitation of this invention. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the scope of protection of this invention.

[0061] Reference Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 As can be seen, the method for controlling roadway floor heave with continuous weakening and stress bias of the floor plate in this patent specifically includes the following steps;

[0062] S1: Identification of stress environment in the base plate and determination of the target weakened layer

[0063] Based on the tunnel burial depth, ground stress test results, and mining influence conditions, the principal stress distribution characteristics of the tunnel floor under the disturbance of tunneling and mining were analyzed, and the key bearing layer bearing the high level of principal stress concentration in the floor was determined as the target layer for floor cutting and weakening.

[0064] S2: Design of bottom-cutting weakening parameters

[0065] Based on the target weakened layer's burial depth, lithology, and stress state, determine the depth range, cutting length, cutting spacing, and continuous arrangement of the bottom-cutting weakening structure so that it can cover the main stress transmission path of the base plate.

[0066] S3: Bottom plate cutting and drilling arrangement

[0067] Multiple rows of bottom-cutting boreholes are arranged along the roadway floor. Each row of bottom-cutting boreholes is arranged continuously along the roadway axis, and a preset distance is maintained between adjacent bottom-cutting boreholes, so that multiple bottom-cutting boreholes form a continuous bottom-cutting weakening zone in space.

[0068] S4: Artificially manufactured bottom-cutting weakening structure

[0069] By using directional blasting, bottom cutting operations are carried out inside the bottom cutting borehole to form a continuous bottom cutting weakening structure with a certain thickness and extension length within the target weakening layer of the base plate.

[0070] S5: Synergistic Regulation of Stress Bias and Continuous Weakening

[0071] By using the continuously weakened structure as a stress regulation interface, the original bearing structure and principal stress transmission path of the floor plate are actively changed, and the high-level principal stress that was originally concentrated on the roadway floor plate is deflected and redistributed along the continuously weakened structure, so that the principal stress of the floor plate changes from a concentrated state to a dispersed transmission state.

[0072] S6: Monitoring and Parameter Optimization of Bass Drum Control Effect

[0073] During the service period of the roadway, the displacement, stress changes and floor heave development of the floor plate are continuously monitored. Based on the monitoring results, the floor weakening parameters are adaptively optimized and adjusted to achieve long-term stable control of the roadway floor plate.

[0074] To represent the deflecting effect of the continuously weakened zone formed by blasting on the stress field, a planar mechanical model of "infinite elastic body - elliptical hole-shaped weakened zone" is constructed. It is assumed that the continuously weakened zone formed by blasting is equivalent to an elliptical hole structure with major axis 2a and minor axis 2b in the cross section of the roadway, and the surrounding rock is an isotropic elastic body.

[0075] By introducing complex variable function theory, the stress field distribution around the weakened zone is solved using the conformal transformation method. Complex variables are defined. and mapping plane variables Through mapping function Will The outer domain of an elliptical hole on a plane is mapped as The outer region of the unit circle on the plane ( The mapping function is constructed as follows:

[0076]

[0077] In the formula: R=(a+b) / 2; m=(ab) / (a+b). R and m are constants determined by the geometry of the weakening zone, reflecting the average radius and flatness of the weakening zone, respectively.

[0078] Maximum horizontal principal stress in the far field (recorded as) and vertical principal stress (recorded as) Under the boundary conditions, based on the complex potential theory of elasticity, the stress components (radial stress) at any point around the weakened zone are... The tangential stress σθ satisfies the following analytical relationship:

[0079] ;

[0080] ;

[0081] Complex potential function The parsing expression is

[0082] ;

[0083] The theoretical calculations above show that, because the elastic modulus and bearing capacity of the medium within the weakened zone are significantly lower than those of the original rock, when high-level geostress is transmitted to the boundary of the weakened zone, the complex potential function changes, and the stress field is redistributed. The theoretical formula indicates that the principal stress traces cannot directly pass through the weakened zone, but instead intersect at their tips at an angle of... The stress deflection and guidance effect force the original horizontal structural stress to transfer to a deeper part of the floor, thereby forming a "low-stress protection zone" in the shallow area of ​​the roadway floor. This mechanical mechanism confirms that the weakening zone described in this invention can achieve stress deflection.

[0084] Theoretical calculation and engineering verification of fracture penetration achieved by spacing between blasting holes:

[0085] To ensure that the cracks between adjacent shaped charge blasting holes can be interconnected to form a continuous weakened structure rather than an isolated fractured cavity, this invention establishes a quantitative relationship between the crack propagation radius and the hole spacing based on the principles of fracture mechanics and superposition of explosion waves, and verifies it by substituting the engineering parameters of Pingmei No. 8 Mine.

[0086] Theoretical calculation model for crack propagation radius:

[0087] The fracture propagation zone in rock blasting is mainly formed by the combined effects of the explosion stress wave and the quasi-static pressure of the detonation gas. For the shaped charge structure used in this invention, its fracture propagation radius is calculated as follows:

[0088] Non-focusing direction crack radius : The tangential tensile stress generated by the explosion stress wave in the rock mass Exceeding the dynamic tensile strength of rock At this point, the fracture begins to propagate. Considering the attenuation characteristics of stress waves in the rock mass, the fracture radius in the non-focusing direction is:

[0089] ;

[0090] in: The radius of the borehole; The initial impact pressure on the borehole wall; The stress attenuation coefficient is usually taken as... ,in It is Poisson's ratio.

[0091] Energy-focusing direction crack radius Due to the directional focusing effect of the focused jet on energy, a focusing influence coefficient is introduced. ( Then, the main fracture propagation radius in the energy-focusing direction is corrected as follows:

[0092] ;

[0093] Critical criterion for fracture penetration:

[0094] To achieve fracture penetration between adjacent boreholes, the designed borehole spacing... The following conditions must be met:

[0095] ;

[0096] The return air incline of a coal mine mining area was selected as the implementation object. The lithology of the floor in this area is mainly fine-grained sandstone and sandy mudstone. Based on the above theoretical model, the field measured parameters were substituted for calculation: Rock parameters: Dynamic tensile strength of sandy mudstone. The stress wave attenuation coefficient is approximately 4~6 MPa. Explosive parameters: Hole radius (Corresponding to an 80mm cartridge diameter), detonation velocity of emulsion explosive .

[0097] Substituting the above parameters into the formula, the effective fracture propagation radius in the single-hole focusing direction is obtained. It is approximately 500mm to 600mm. Based on this, the theoretically calculated critical penetration spacing is... It should be between 1.0m and 1.2m. Existing spacing (S) The setting is 1.0m. Judgment result. Judgment: The existing spacing is within the effective connection range calculated theoretically.

[0098] In step S1, firstly, based on the geological columnar section of the tunnel floor, the hard rock strata with high elastic modulus and strength below the floor are identified. Secondly, through numerical simulation analysis of the vertical and horizontal stress distribution of the floor during tunnel excavation and mining, the rock strata with the largest horizontal stress concentration coefficient and mainly bearing the horizontal load are identified as the key bearing layer. Finally, the depth range of the key bearing layer is defined as the target layer for bottom cutting and weakening. The depth range of the bottom cutting and weakening structure is determined by in-situ stress testing and rock stratum exploration to identify the target weakening layer. The depth of the top and bottom plates is determined by using directional shaped charge blasting technology to penetrate the entire thickness of the target weakened layer, ensuring complete severing of the shallow stress transmission path. The cutting length is determined based on the cyclic advance step distance of the roadway excavation face (usually 6-8m) or the length of the mining-affected section (50-100m ahead of the working face), and is implemented synchronously with the roadway construction progress using segmented continuous blasting. The cutting spacing is calculated based on the dynamic tensile strength of rock, the attenuation characteristics of explosive stress waves, and the enhancement effect of shaped charge jets in fracture mechanics, to determine the effective fracture propagation radius of a single hole. The optimal hole spacing is determined for the critical criteria, usually 0.8-1.2m, to ensure that the fractures of adjacent blasting holes are interconnected. The continuous arrangement adopts a linear arrangement of boreholes without interruption along the roadway. When encountering geological structural zones, it is adjusted to a zigzag pattern to bypass faults or fracture zones. By precisely controlling the borehole angle and blasting parameters, a continuous weakened structure zone covering the full thickness of the target weakened layer and equal in length to the affected section of the roadway is finally formed.

[0099] In step S2, the design of the bottom-cutting weakening parameters is achieved through a systematic process of geological data acquisition, mechanical model calculation, and engineering parameter matching. First, based on the results of in-situ stress testing, rock strata borehole exploration data, and numerical simulation analysis, the burial depth of the top and bottom plates of the target weakened layer, the uniaxial compressive strength of the rock, the dynamic tensile strength, and the magnitude and direction of the horizontal principal stress are determined. In terms of depth range design, the full thickness of the target weakened layer is used as the benchmark, and the target layer's top and bottom plate interface is covered by directional shaped charge blasting boreholes to ensure that the weakened zone completely cuts off the stress transmission channel between the shallow bottom plate and the deep rock mass. The bottom-cutting length is determined according to the cyclic advance step distance or mining depth of the roadway excavation face. The length of the affected section is determined, and a segmented continuous blasting method is adopted to be implemented in sync with the tunnel construction progress, so that the weakened structure always covers the tunnel section currently affected by stress. The slit spacing is based on the attenuation law of explosive stress wave in fracture mechanics and the principle of fracture propagation of shaped charge jet, and the effective fracture propagation radius of a single hole is calculated. The continuous arrangement adopts a linear arrangement of boreholes along the tunnel direction. When encountering geological structures such as faults and fracture zones, it is adjusted to a zigzag pattern to bypass the abnormal area. By precisely controlling the borehole inclination angle to be 15°-30° with the horizontal direction, the direction of the shaped charge, and the blasting energy, a continuous weakened structure zone that can completely cover the main stress transmission path of the floor plate is finally formed.

[0100] The determination of the slit spacing primarily depends on the ultimate length of the directional cracks generated in the target rock strata by single-hole shaped charge blasting. Based on fracture mechanics theory, the termination condition for crack propagation is: the stress intensity factor at the crack tip (…). The strength of the rock decreases until it is less than the fracture strength of the rock. The specific calculation process is as follows:

[0101] Step 1: Calculate the initial impact pressure on the borehole wall

[0102] The average pressure generated on the borehole wall at the instant of explosive detonation, considering the effect of the charge decoupling coefficient: In the formula:

[0103] This refers to the initial pressure on the borehole wall; D is the density of the explosive; D is the detonation velocity of the explosive. The adiabatic index of detonation products is generally taken as 3; The radial decoupling coefficient is preferably n=1.4; This is the volume ratio parameter between the medicine roll and the hole wall;

[0104] Step 2: Calculate the stress enhancement effect in the energy focusing direction. )

[0105] Due to the use of a shaped charge structure, such as the 60° cone-shaped charge shield in this invention, detonation energy is focused in a specific direction. A shaped charge enhancement factor is introduced. (generally >1):

[0106] ;

[0107] The pressure It is the main driving force that propagates the crack along the predetermined cutting direction.

[0108] Step 3: Crack propagation radius of a single pore based on fracture mechanics calculate

[0109] Treating the borehole as a thick-walled cylinder and the crack as a radial crack driven by internal pressure, according to fracture mechanics, the stress intensity factor at the crack tip... With crack length It decreases as it increases. When = At this point, the crack stops propagating. That is, the maximum crack propagation radius. :

[0110] ;

[0111] In the formula: The limiting radius for crack propagation in the energy-focusing direction; The radius of the borehole; The fracture strength of the target rock stratum (fine-grained sandstone); This is a geometric correction factor related to the energy focusing direction; This is the stress wave attenuation index.

[0112] Step 4: Determine the optimal spacing (S) based on the principle of superposition of explosion waves.

[0113] In order to form a continuous "bottom-cutting weakening zone" between adjacent boreholes, the superposition effect of stress waves must be utilized.

[0114] When two adjacent boreholes are detonated simultaneously, the stress waves generated by the two boreholes superimpose at the midpoint of the line connecting their centers. Based on the principle of wave superposition, to ensure fracture penetration without excessive rock fragmentation, the design spacing... Should meet:

[0115] ;

[0116] In the formula:

[0117] The spacing between adjacent bottom-cutting boreholes; This is the fracture penetration coefficient, typically ranging from 0.8 to 0.9. This coefficient takes into account geological heterogeneity and construction deviations; to ensure "cutting to the bottom without breaking the bottom" (i.e., forming cracks but not causing large-scale breakage), a certain overlap margin must be maintained.

[0118] In step S3, the process of forming a continuous weakened zone by arranging multiple rows of bottom-cutting boreholes along the strike of the roadway floor is as follows: First, through borehole inspection, in-situ stress testing, and FLAC3D numerical simulation analysis, the lithological distribution, thickness range, and principal stress transmission path of the target weakened layer are determined, thereby determining the number of borehole rows. When the roadway width is less than 4.5m, a single row arrangement is adopted, with the boreholes located on the centerline of the roadway floor. At this time, the fracture zone formed by a single row of shaped charge blasting is sufficient to destroy the ultimate bending moment point in the middle of the floor rock beam, blocking the continuous transmission of horizontal stress.

[0119] When the tunnel width is greater than 4.5m, a double-row or multi-row arrangement is adopted. For tunnels wider than 4.5m but less than 6m, double-row boreholes are arranged, with the two rows of boreholes symmetrical about the tunnel centerline, taking into account the stress concentration areas in the middle of the floor and the bottom corners of both sides, to prevent eccentric floor heave due to insufficient single-point weakening of the wide floor. The borehole inclination angle is controlled between 15° and 30° to ensure that the direction of the focused jet is perpendicular to the horizontal principal stress transmission path. The borehole depth penetrates the full thickness of the target weakened layer and extends 0.5-1m into the underlying stable rock layer. The spacing between adjacent bottom-cutting boreholes is determined based on the critical value of fracture penetration calculated from the dynamic tensile strength of rock and the attenuation law of explosive stress waves in fracture mechanics, and is usually set to 0.8-1.2m. The spacing between rows is adjusted to 1.5-2.5m according to the stress distribution characteristics of the weakened layer to ensure that the multi-row drilling... The blasting cracks in the boreholes are spatially interwoven and interconnected. During construction, a drilling-then-blasting method is adopted, with shaped charge charges in each row of boreholes detonated sequentially according to the roadway direction. The superposition effect of the blast waves causes the cracks generated in adjacent boreholes to expand and connect with each other. At the same time, the blasting vibration velocity is monitored in real time to control the blasting energy and avoid excessive damage to the surrounding rock of the roadway. Finally, the quality of the weakened zone is inspected using a borehole inspection instrument or ultrasonic detection technology to verify the continuity and penetration range of the cracks. If there are local unpenetrated areas, they are repaired by additional drilling and blasting. Ultimately, a spatially continuous weakened zone with no gaps along the roadway direction and covering the full thickness of the target weakened layer is formed, effectively blocking and deflecting the transmission path of the main stress in the floor.

[0120] In step S4, the shaped charge structure is first designed according to the burial depth, lithology and stress state of the target weakened layer. An emulsion explosive cartridge with a built-in copper or aluminum conical shaped charge hood is used. The cone angle of the shaped charge hood is set to 60°-90° to optimize the jet concentration. The cartridge diameter matches the borehole diameter. The linear charge density is adjusted to 0.3-0.8 kg / m according to the uniaxial compressive strength of the rock to ensure that the explosive energy is focused on the target weakened layer.

[0121] During construction, the drilling inclination angle is precisely controlled at 15°-30° using a tracked directional drilling rig, ensuring that the opening direction of the energy-concentrating cover is strictly pointed towards the target weakened layer deep in the bottom plate. The drilling depth penetrates the full thickness of the target weakened layer and extends 0.5-1m into the underlying stable rock layer. The spacing between adjacent boreholes is set to 0.8-1.2m based on the critical value of fracture penetration calculated by fracture mechanics, and they are continuously arranged along the direction of the roadway.

[0122] The initiation stage adopts a millisecond delay initiation network, with the initiation delay between adjacent boreholes controlled at 25-50ms. The superposition effect of explosive stress waves promotes the mutual expansion and connection of fractures. At the same time, the initiation energy is controlled in real time through the blasting vibration monitoring system to keep the vibration velocity within 1.5cm / s to avoid excessive damage to the shallow surrounding rock of the roadway.

[0123] After blasting, the focused jet forms dense radial and axial through-cracks within the target weakened layer, reducing the rock mass integrity coefficient to below 0.3 and decreasing the uniaxial compressive strength. Ultimately, a low-strength rock mass area is formed that runs uninterrupted along the tunnel direction and covers the full thickness of the target weakened layer. This area cuts off the main stress transmission path of the floor plate through the through-crack zone, achieving the engineering goal of stress isolation and deflection. Finally, the through-crack penetration rate and rock mass strength of the weakened zone are detected by borehole inspection or ultrasonic detection technology. If there are any areas that do not meet the standards, they are repaired by additional drilling and blasting.

[0124] The specific process includes:

[0125] Targeted jet penetration: After the explosive is detonated, the detonation wave is converged by a 60° conical shaped charge shield and forms a high-energy jet in the bottom cutting direction. The concentrated compressive stress generated by this jet has a peak value of >45MPa, which instantly exceeds the dynamic compressive strength of the borehole wall rock and forces the initial guide cracks to form in the predetermined direction on both sides of the borehole.

[0126] Gas wedge splitting propagation: Subsequent detonation gas weds into the initial fracture, and the quasi-static pressure generated by the gas wedge effect drives the fracture to continue propagating deeper. Due to the use of a 1.4 radially decoupled charge structure, the rock mass in the non-focused direction is less impacted, and the explosion energy is confined to the bottom cutting direction to the maximum extent.

[0127] Dual-hole superposition and connection: Adjacent bottom-cutting boreholes are detonated simultaneously, and the opposing fractures converge and connect at the midpoint of the rock mass between the boreholes. This creates a continuous fracture zone with a macroscopic geometric width within the critical bearing layer of the foundation. The structural integrity of the rock mass in this area is disrupted, and its mechanical parameters are weakened, thus constructing a low-strength barrier that blocks the transmission of horizontal stress.

[0128] In step S5, the coordinated control of stress bias and continuous weakening first obtains the stress field distribution characteristics of the original rock of the roadway floor through the in-situ stress testing system. Combined with FLAC3D numerical simulation analysis, the principal stress transmission path and concentration area are analyzed. Based on the principle of transverse main stress transmission direction of the floor, the depth range of the continuous weakening structure is designed to cover the full thickness of the target weakened layer and the bottom cutting length. The length of the mining-affected section and the cutting spacing are matched and determined based on the critical value of fracture penetration to ensure that the weakened zone completely cuts off the mechanical connection between the stress concentration area of ​​the roadway floor and the deep rock mass. During the construction stage, directional energy-focused blasting technology is used to form a low-strength rock mass area with penetrating fracture zones. By controlling the energy-focused direction, the integrity coefficient of the weakened zone rock mass is reduced to below 0.3 and the uniaxial compressive strength is reduced, artificially constructing a stress control interface with abrupt changes in mechanical properties.

[0129] When the roadway is affected by the dynamic pressure of mining, the high-level principal stress that was originally concentrated towards the floor encounters the weakened zone. Because the bearing capacity of the rock mass in the weakened zone is much lower than that of the original rock, the stress transmission path is actively deflected and dispersed along the weakened zone to the deep stable rock strata or the low-stress areas on both sides of the roadway. At the same time, stress sensors and microseismic monitoring systems deployed in the roadway floor and the weakened zone capture stress redistribution data in real time, verifying the effect of the principal stress changing from concentrated peak values ​​to dispersed low values. If local stress concentration remains, the parameters of the weakened zone are optimized by supplementary drilling and blasting. Ultimately, the stress state of the floor is coordinated from concentrated action to dispersed transmission, effectively reducing the risk of deformation and damage to the roadway floor.

[0130] In step S6, high-precision convergence gauges and displacement sensors are first arranged on the surface of the tunnel floor using a cross-shaped method to collect real-time displacement data of the floor surface. Simultaneously, a set of layered borehole stress gauges is arranged every 50m along the tunnel direction, with sensors buried at depths of 0-2m, 2-4m, and 4-6m in the floor floor to monitor stress changes at different depths. This is combined with an automated floor heave rate monitor to collect data at a frequency of minutes. All monitoring information is transmitted to a ground monitoring platform via the Internet of Things (IoT) to construct a real-time, visualized database of the floor's mechanical state. When the monitoring data... When the strength coefficient of the underlying rock strata increases from f=3 to f=5, or the surrounding rock stress increases from 20MPa to 30MPa, causing the single-hole fracture propagation radius to decrease from 0.6m to 0.4m, the system automatically triggers a slit spacing adjustment command, optimizing the spacing between adjacent boreholes from 1.0m to 0.8m to ensure that the blasting fractures can still be interconnected in high-stress hard rock. When the borehole inspection instrument detects that the borehole wall crushing range exceeds 0.5m while the distal fracture development length is less than 1.0m, it is determined that the charge decoupling coefficient is too low, and the diameter of the shaped charge cartridge and the borehole diameter are adjusted accordingly. The ratio of borehole diameter to borehole diameter was increased from 1.2 to 1.5. This reduced the direct damage of the blast stress wave to the borehole wall, allowing more energy to focus on the propagation of the jet fracture. When the multi-point displacement gauge detected a bottom plate failure depth of 5.5m, exceeding the original bottom-cutting depth of 5.0m, the bottom-cutting borehole depth was immediately adjusted to 6.0m to ensure penetration of the critical bearing layer of the bottom plate. The adjustment cycle strictly matched the degree of mining impact. In weakly disturbed areas more than 100m away from the working face, the fracture penetration rate was checked monthly using a borehole inspection instrument. For every 100m of advancement, the cumulative... The monitoring data is used to fine-tune the cutting spacing; in the strong disturbance zone 20-100m from the working face, stress and displacement data are collected weekly, and the amount of blasting charge and hole spacing are dynamically adjusted every 10m advance in combination with the change of the peak pressure of the advance support, responding in real time to the impact of mining stress waves; in the post-mining lag stability zone, comprehensive monitoring of floor stress and displacement is carried out quarterly, and the cutting depth is optimized for maintenance based on long-term creep data, ultimately forming an intelligent floor stress control system covering the entire life cycle of the roadway, ensuring that the main stress is always in a stable state of dispersed transmission.

[0131] The angle of tip generation is The specific calculation steps for the deflection are as follows:

[0132] Step 1: Constructing the geometric mapping model

[0133] Using conformal mapping function The continuous bottom-cutting weakening structure on the physical plane z is considered as the outer region of an ellipse with a major axis of 2a and a minor axis of 2b, and mapped to the computational plane. The outer region of the unit circle on.

[0134] in, For physical plane complex variables; For the complex variables of the mapping plane; The mapping scale constant; For shape parameters;

[0135] Step 2: Solve for the complex potential function of stress

[0136] Combined with far-field boundary conditions, namely the initial geostress in the deep part of the base plate and Given the free surface conditions at the orifice, determine the two analytical complex potential functions. and :

[0137] The initial stress field is set as follows: maximum horizontal principal stress and The included angle of the axis is ;

[0138] Step 3: Calculate the stress components around the weakened zone.

[0139] Based on the analytical formula for stress components, calculate the stress components at any point around the weakened zone. The curve coordinate stress components:

[0140] ;

[0141] ;

[0142] Therefore, we can solve this. (Radial stress) (tangential stress) and (Shear stress).

[0143] Step 4: Determine the direction and deflection angle of the principal stresses.

[0144] After obtaining the stress components, the principal stress direction angles at that point are calculated using the stress state equation. :

[0145] ;

[0146] Ultimately, the stress deflection angle That is, the direction of the weakened principal stress. relative to the direction of initial geostress The absolute value of the difference:

[0147] ;

[0148] Through the above calculations, it can be quantitatively concluded that the principal stress traces are significantly deflected at the tip and directly below the weakened zone. For example, the calculation results typically show that in the shielded area of ​​the weakened zone, the direction of the maximum principal stress deflects from horizontal (approximately 0°) to a large-angle oblique (>45°), thus theoretically proving that the present invention achieves a stress deflection mechanism that transfers horizontal extrusion stress to deeper layers.

[0149] Working principle: First, the target weakened layer is accurately located through geological survey and numerical simulation. The lithological distribution of the tunnel floor, the original rock stress field and the principal stress transmission path are obtained by using a borehole inspection instrument and a ground stress testing system. Combined with FLAC3D numerical simulation analysis, the range and peak value of the stress concentration area of ​​the floor are analyzed to determine the burial depth, thickness and mechanical parameters of the target weakened layer. Based on this, the number of rows, spacing, inclination angle and depth of bottom-cutting boreholes are designed.

[0150] Secondly, a continuous weakened zone is formed through directional shaped charge blasting. Emulsion explosive cartridges with built-in conical shaped charge covers are used, with the charge direction strictly pointing towards the target weakened layer. The linear charge density of the cartridges is adjusted to 0.3-0.8 kg / m based on the uniaxial compressive strength of the rock. A millisecond delay initiation network is used to sequentially detonate adjacent boreholes. The superposition effect of the explosive stress waves allows the blasting fractures to interconnect, forming a low-strength weakened zone with a rock integrity coefficient ≤0.3 and a uniaxial compressive strength reduction of 60%-80%. Next, the load-bearing structure of the floor is altered through the coordinated control of stress deflection and continuous weakening. When the roadway is affected by the dynamic pressure of mining, the high-level principal stress that was originally concentrated towards the floor encounters the weakened zone. Because the load-bearing capacity of the weakened zone rock mass is much lower than that of the original rock, the stress transmission path actively deflects, dispersing along the weakened zone towards deeper stable rock layers or low-stress areas on both sides of the roadway. This reduces the peak value of the floor principal stress to ≤15 MPa, achieving a transformation from concentrated stress to dispersed transmission.

[0151] Finally, a closed-loop control system is formed through multi-dimensional continuous monitoring and adaptive optimization. Convergence meters and displacement sensors are deployed on the roadway surface, layered stress gauges are deployed in the deep section, and a microseismic monitoring system is deployed across the entire cross section to collect data on floor displacement, stress, and floor heave rate in real time. When the rock stratum firmness coefficient increases, stress rises, or crack propagation is insufficient, the cutting spacing, blasting charge amount, and cutting depth are dynamically adjusted. The adjustment cycle matches the degree of mining impact: monthly review of weakly disturbed areas, weekly adjustment of strongly disturbed areas, and quarterly maintenance of post-mining stable areas to ensure that the weakened zone always effectively blocks the stress transmission path and achieves long-term stability of the roadway floor.

[0152] In conventional blasting for bottom cutting, the energy of the explosive is dispersed, and the drilled holes develop only locally and are difficult to penetrate, which cannot effectively block the transmission of the main stress. This patent adopts directional shaped charge blasting and continuous drilling arrangement. Through the directional destructive effect of the shaped charge jet and the stress wave superposition effect of the millisecond delay initiation, the blasting cracks of adjacent drill holes expand and connect with each other, forming a continuous weakening zone without interruption along the roadway. The crack penetration rate is improved, and the transmission path of the main stress of the floor plate to the roadway is effectively cut off.

[0153] Secondly, this patent addresses the issue of passive stress control. Traditional methods such as grouting reinforcement and anchor bolt support can only passively increase the strength of the surrounding rock and cannot change the direction of stress transmission. When the mining stress exceeds the bearing limit of the surrounding rock, bottom heave will still occur. This patent constructs a weakening zone with abrupt changes in mechanical properties as a stress control interface, actively guiding the principal stress to the deep stable rock strata, reducing the stress concentration factor of the bottom plate from 2.5-3.0 to 1.2-1.5, transforming passive bearing into active control, and reducing the deformation dynamics of the bottom plate from the root cause.

[0154] Finally, this patent addresses the problem of poor adaptability of fixed parameters. Traditional bottom-cutting methods use fixed drilling parameters and blasting processes, which cannot adapt to the dynamic changes in mining stress, resulting in the weakening effect decaying over time. This patent uses a multi-dimensional real-time monitoring and adaptive optimization system to adjust the cutting spacing, charge amount, and bottom-cutting depth according to changes in the hardness of the floor rock strata, fluctuations in peak stress, and bottom heave rate. In areas of strong disturbance, parameters are dynamically adjusted weekly to ensure that the weakened zone always matches the current stress state, reducing the bottom heave rate and extending the roadway maintenance cycle. At the same time, the blasting vibration monitoring controls the detonation energy to avoid excessive damage to the shallow surrounding rock of the roadway, achieving a synergistic balance between floor stability and surrounding rock protection.

[0155] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, substitutions, or improvements made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A method for controlling roadway floor heave through continuous weakening and stress bias in the floor slab, characterized in that, Includes the following steps: S1: Identification of stress environment of floor plate and determination of target weakening layer: Based on the roadway burial depth, ground stress test results and mining influence conditions, analyze the principal stress distribution characteristics of the roadway floor plate under the disturbance of tunneling and mining, and determine the key bearing layer in the floor plate that bears the high level of principal stress concentration, as the target layer for floor plate cutting and weakening. S2: Design of bottom cutting weakening parameters: Based on the burial depth, lithology and stress state of the target weakening layer, determine the depth range, bottom cutting length, cutting spacing and continuous arrangement of the bottom cutting weakening structure so that the bottom cutting weakening structure can cover the main stress transmission path of the bottom plate. S3: Bottom-cutting borehole arrangement: Multiple rows of bottom-cutting boreholes are arranged along the direction of the roadway on the bottom plate. Each row of bottom-cutting boreholes is arranged continuously along the roadway axis. A preset distance is maintained between adjacent bottom-cutting boreholes so that multiple bottom-cutting boreholes form a continuous bottom-cutting weakening zone in space. S4: Artificially manufactured bottom-cutting weakening structure: Through directional energy-concentrating blasting, bottom-cutting operations are carried out in the bottom-cutting borehole to form a continuous bottom-cutting weakening structure with a certain thickness and extension length in the target weakening layer of the bottom plate; S5: Stress bias and continuous weakening coordinated control: Using the continuous weakening structure as a stress control interface, actively change the original bearing structure and main stress transmission path of the floor plate, guide the high-level main stress that was originally concentrated towards the roadway floor plate to be biased and redistributed along the continuous weakening structure, so that the main stress of the floor plate changes from a concentrated state to a dispersed transmission state. S6: Monitoring and Parameter Optimization of Floor Heave Control Effect: During the service period of the roadway, the displacement, stress changes and floor heave development of the floor plate are continuously monitored. Based on the monitoring results, the floor weakening parameters are adaptively optimized and adjusted to achieve long-term stable control of the roadway floor plate.

2. The method for controlling roadway floor heave by continuous weakening and stress bias of the floor slab according to claim 1, characterized in that, In step S1, when analyzing the distribution characteristics of principal stress in the roadway floor, the tectonic stress components obtained by testing the self-weight stress corresponding to the roadway burial depth and the ground stress, as well as the disturbance stress formed by the superposition of repeated mining of multiple coal seams and working face mining disturbance, are used to determine the key bearing layer in the floor that bears the high level of principal stress concentration as the core path layer for principal stress transmission in the deep rock mass of the floor.

3. The method for controlling roadway floor heave by continuous weakening and stress bias of the floor slab according to claim 1, characterized in that, In step S2, the depth range of the bottom-cutting weakening structure covers the full thickness of the target weakening layer, the bottom-cutting length matches the advance step distance of the roadway excavation face or the length of the mining-affected section, the cutting spacing is determined based on the critical value of fracture penetration calculated by the principle of fracture mechanics and superposition of explosion waves, and the continuous arrangement is a linear or polygonal continuous structure without interruption along the roadway direction.

4. The method for controlling roadway floor heave by continuous weakening and stress bias of the floor slab according to claim 1, characterized in that, In step S3, the number of rows of bottom-cutting boreholes is determined according to the roadway width and the distribution range of principal stress in the floor plate, and the preset spacing between adjacent bottom-cutting boreholes ensures that the cracks of adjacent shaped charge blasting holes can be interconnected.

5. The method for controlling roadway floor heave by continuous weakening and stress bias of the floor slab according to claim 1, characterized in that, In step S4, the directional shaped charge blasting adopts a shaped charge structure, with the shaped charge direction pointing towards the target weakened layer deep in the bottom plate. The continuous bottom-cutting weakened structure formed after the blasting is a low-strength rock mass area with a through-fracture zone.

6. The method for controlling roadway floor heave by continuous weakening and stress bias of the floor slab according to claim 1, characterized in that, In step S5, the stress deflection and redistribution are achieved through the stress barrier and guiding effect of the continuously weakened structure, forcing the original horizontal structural stress to transfer to a deeper part of the bottom plate, forming a low stress protection zone in the shallow area of ​​the roadway bottom plate.

7. The method for controlling roadway floor heave by continuous weakening and stress bias of the floor slab according to claim 1, characterized in that, In step S6, the continuous monitoring includes floor surface displacement monitoring, floor deep stress monitoring, and floor heave rate monitoring. The adaptively optimized bottom-cutting weakening parameters include cut spacing, blasting charge amount, and bottom-cutting depth. The adjustment cycle is determined according to the frequency of the roadway being affected by mining.

8. The method for controlling roadway floor heave by continuous weakening and stress bias of the floor slab according to claim 6, characterized in that, In step S5, the mechanical mechanism by which the continuous weakened zone achieves stress deflection is verified by the planar mechanical model of the infinite elastic body-elliptical hole weakened zone. The stress field around the weakened zone is solved by the conformal transformation method of complex variable functions, proving that the principal stress traces deflect at the tip of the weakened zone, forming a path for stress to transfer to the depth. Specifically, the continuous weakened zone formed by blasting is equivalent to an elliptical hole structure with major axis 2a and minor axis 2b on the cross section of the roadway, and the surrounding rock is an isotropic elastic body. By introducing complex variable theory and using the conformal transformation method to solve for the stress field distribution around the weakened zone, complex variables are defined. and mapping plane variables Through mapping function Will The outer domain of an elliptical hole on a plane is mapped as The outer region of the unit circle on the plane, where, The mapping function is constructed as follows: ； In the formula: R and m are constants determined by the geometry of the weakening band, reflecting the average radius and flatness of the weakening band, respectively. The distance between any point outside the standard circle and the center of the circle. Let any point outside the standard circle be the sum of the points of the circle and the center. Angle between planes; Maximum horizontal principal stress in the far field Recorded as and vertical principal stress Recorded as Under the boundary conditions, based on the complex potential theory of elasticity, the stress component at any point around the weakened zone, the radial stress tangential stress It satisfies the following parsing relation: ； ； Complex potential function The parsing expression is: ； The principal stress trace occurs at an angle of at its tip. The deflection creates a "low-stress protection zone" in the shallow part of the tunnel floor. in, Let be the real part of the complex number. It is a complex function and a core function in the complex function solution method of elasticity, used to solve for stress components. For shear stress components, for The conjugate function, The pressure inside the elliptical hole. The principal stress direction angle, i.e., the angle between the maximum principal stress in the far field and the... Angle between axes.

9. The method for controlling roadway floor heave by continuous weakening and stress bias of the floor slab according to claim 3, characterized in that, The theoretical calculation of the slit spacing is based on the principles of fracture mechanics and the superposition of explosion waves. The fracture propagation radius is determined by the attenuation characteristics of the explosion stress wave and the dynamic tensile strength of the rock. The specific calculation method for the fracture propagation radius is as follows: Non-focusing direction crack radius : The tangential tensile stress generated by the explosion stress wave in the rock mass Exceeding the dynamic tensile strength of rock At that time, the fracture begins to propagate. Considering the attenuation characteristics of stress waves in the rock mass, the fracture radius in the non-focusing direction is: ； in: The radius of the borehole; The initial impact pressure on the borehole wall; The stress attenuation coefficient is usually taken as... ,in Poisson's ratio; Energy-focusing direction crack radius Due to the directional focusing effect of the focused jet on energy, a focusing influence coefficient is introduced. , The radius of propagation of the main fracture in the energy-focusing direction is then corrected as follows: 。 10. The method for controlling roadway floor heave by continuous weakening and stress bias of the floor slab according to claim 9, characterized in that, The designed borehole spacing is intended to achieve fracture penetration between adjacent boreholes. The following conditions must be met: 。

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