Active pressure relief roadway fixing method and system for overlying remaining coal pillars

Abstract

The invention discloses an active pressure relief roadway fixing method and system for an overlying remaining coal pillar, relates to the technical field of mine pressure control and safe mining, and solves the problems that in the prior art, effective source load shedding is difficult to implement on the overlying remaining coal pillar; and when the lower layer roadway passes through the coal pillar high stress influence area, the mine pressure is strong, the maintenance cost is high, and the treatment effect is unstable. The active pressure relief roadway fixing method comprises the steps that S1, based on mine production geological data, the stress influence range of an upper-layer target coal pillar on a lower-layer roadway is determined, and one or more pressure relief coal body units are designed and determined in the upper-layer target coal pillar; s2, the one or more pressure relief coal body units are pulled out so that the pressure relief coal body units can be removed from the upper-layer target coal pillar, and pressure relief cavities corresponding to the pressure relief coal body units are formed in the upper-layer target coal pillar; a pressure relief cavity is formed, so that a concentrated stress peak value near the lower-layer roadway is moved outwards to an area far away from the lower-layer roadway.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mine pressure control and safe mining, and particularly relates to a method and system for active pressure relief and roadway stabilization of overlying residual coal pillars. BACKGROUND

[0002] Under the condition of coal seam mining, especially under the condition of coal seam descending mining sequence (mining layer by layer from top to bottom), various types of coal pillars are often left after the mining of the upper coal seam due to the protection of shafts and roadways, surface buildings or mining area boundary isolation, etc., forming overlying residual coal pillars. As one of the main bearing bodies, the residual coal pillars will bear and transmit the load of the overlying rock strata for a long time after the goaf is formed, making the coal and rock mass below it in a high support pressure or stress concentration state. Since the collapse body or filling body in the goaf usually presents a loose-compact evolution process, it is difficult to provide continuous bearing and stiffness comparable to the original rock in a long time scale, and the load tends to be transmitted to the lower coal seam through the residual coal pillars and the surrounding solid coal and rock mass, thereby forming a continuous high stress influence zone in the projection range of the residual coal pillars and near the boundary thereof; When the lower coal seam tunnel or mining crossheading passes through the influence zone, the surrounding rock of the tunnel often appears in an unfavorable state of plastic zone expansion and crack development, etc., which further leads to severe mine pressure manifestations such as roof subsidence, floor heave, rib spalling, etc., serious convergence of the tunnel cross section, and increased maintenance frequency. At this time, if the passive reinforcement (such as densifying anchor rods and anchor cables, erecting sheds, thickening by shotcreting, etc.) is simply relied on, the support strength and density often need to be significantly improved, which is high in engineering cost and long in construction period, and since the stress source still exists, the surrounding rock deformation and mine pressure manifestations may still occur repeatedly, and the treatment effect is limited.

[0003] In view of the above problems, one type of method in the prior art adopts measures such as blasting pressure relief, CO2 fracturing, hydraulic fracturing, etc. to form a fracture zone or damage zone in the coal and rock mass, so as to induce stress redistribution by reducing the integrity and stiffness of the medium, in order to achieve local unloading and peak stress migration. However, the action object of this type of method is usually the coal and rock medium in the stress transmission process or the pressure relief zone around the tunnel, and the unloading range and effect are easily affected by factors such as the in-situ stress field, original cracks, sealing quality and crack closure compaction, etc., and it is difficult to effectively and controllably control the surrounding rock of the tunnel; Another type of method tends to adopt the method of expanding and digging the sidewall of the tunnel, cleaning and breaking the surrounding rock, and cooperating with secondary support, etc. to restore the clearance of the tunnel and inhibit the deformation development. However, in the high stress influence zone of the residual coal pillars, the surrounding rock of the tunnel is often in a critical state of high stress and broken softening, and the expansion and digging of the sidewall will further expand the excavation section, weaken the bearing structure of the surrounding rock and introduce significant construction disturbance, which is easy to induce the risk of roof development into overall caving, etc., and the safety and implementability are poor. SUMMARY

[0004] Therefore, this application provides an active pressure relief and roadway stabilization method and system for overlying coal pillars, in order to solve the problem that it is difficult to effectively reduce the load on overlying coal pillars in the prior art, resulting in strong mine pressure, high maintenance costs and unstable treatment effects when the lower roadway passes through the high stress influence zone of the coal pillar.

[0005] To achieve the above objectives, this application provides the following technical solution: An active decompression and roadway stabilization method for overlying residual coal pillars includes the following steps: S1: Based on the mine's production geological data, determine the stress influence range of the upper target coal pillar on the lower roadway, and design and determine one or more pressure relief coal body units within the upper target coal pillar. Each pressure relief coal body unit shall include at least its spatial location and pressure relief volume. S2: Remove one or more depressurized coal body units to remove them from the upper target coal pillar and form a depressurized cavity corresponding to the depressurized coal body unit in the upper target coal pillar; By forming a pressure relief cavity, the concentrated stress peak near the lower roadway is shifted to a region far away from the lower roadway.

[0006] Optionally, step S2 includes: selecting a working position in the lower roadway, and constructing one or more guide holes upward from the working position, so that the one or more guide holes pass through the roof of the lower roadway and penetrate into the upper target coal pillar, and removing the depressurized coal body unit through the guide holes.

[0007] Optionally, in step S2, a safety chamber is constructed in the lower roadway; and one or more pilot holes are constructed on the roof of the safety chamber in an inclined manner; the removal device enters the target coal pillar through the pilot holes to cut and crush the depressurized coal body unit, so that the depressurized coal body unit determined by the design is removed.

[0008] Optionally, the safety chamber is equipped with reinforced support, including bolt support and / or cable support, in conjunction with shotcrete support.

[0009] Optionally, after step S2, step S3 is also included: injecting quick-setting filling material into the pressure relief cavity through the guide hole, so that the quick-setting filling material solidifies in the pressure relief cavity to construct a flexible support.

[0010] Optionally, step S4 is included after step S3: monitoring the deformation of the surrounding rock in the lower roadway and comparing the deformation of the surrounding rock before and after step S2 and / or step S3 to quantitatively evaluate the pressure relief effect.

[0011] Optionally, step S2 includes: arranging an upper working roadway along the upper target coal pillar in the upper coal seam, the upper working roadway being adjacent to the upper target coal pillar, and the upper target coal pillar forming one side of the upper working roadway; removing one or more depressurized coal body units in the upper working roadway to form a corresponding depressurized cavity in the upper target coal pillar.

[0012] Optionally, the depressurization cavity penetrates the upper target coal pillar.

[0013] This application discloses an active pressure relief and roadway stabilization system for overlying residual coal pillars, comprising: an upper target coal pillar, a lower roadway, a safety chamber, and a removal device; The upper target coal pillar is located above the lower roadway, and at least a portion of the lower roadway is within the stress influence range of the upper target coal pillar. The safety chamber is located in the lower roadway and is situated within the stress influence range of the upper target coal pillar; The removal equipment is arranged in the safety chamber. One or more guide holes are constructed by the removal equipment. The guide holes extend upward from the top plate of the safety chamber and penetrate into the upper target coal pillar. One or more depressurized coal body units are designed within the upper target coal pillar, and the number of depressurized coal body units corresponds one-to-one with the number of guide holes; The removal device is used to enter the upper target coal pillar through the guide hole and remove the pressure-relieved coal body unit to form a pressure-relieved cavity corresponding to the pressure-relieved coal body unit, thereby shifting the concentrated stress peak near the lower roadway to an area far away from the lower roadway.

[0014] Optionally, the removal device includes: a drilling device for constructing pilot holes and cutting and crushing the depressurized coal body units; A closed recovery device, connected to the drilling device, is used to recover rock and coal chips generated by the drilling device during the construction of the pilot hole and the cutting and crushing of the depressurized coal body unit.

[0015] Compared with the prior art, this application has at least the following beneficial effects:

[0016] Mine production geological data, including geological and mining data, is used to quantitatively identify and spatially locate the load transfer relationship between the upper target coal pillar, surrounding rock, and lower roadway. Based on the geological and mining data, the stress influence range of the upper target coal pillar on the lower roadway can be determined, thereby predicting potential risks of mine pressure manifestation such as roof subsidence, sidewall spalling, floor heave, and increased roadway convergence, and providing boundary conditions for the selection of subsequent pressure relief targets. When designing and determining one or more pressure relief coal body units within the upper target coal pillar, by clarifying the spatial location and pressure relief volume of the pressure relief coal body units, the spatial coordinate range and removal boundary of the coal body to be removed (including the center position, outline, and volumetric dimensions of the pressure relief unit) can be determined, thus forming an feasible pressure relief plan.

[0017] After removing one or more depressurized coal body units from the upper target coal pillar, one or more depressurized cavities corresponding to the depressurized coal body units are formed within the upper target coal pillar. Due to the significant reduction in the bearing capacity and overall stiffness of the cavity region, the transmission path of the overlying load within the coal pillar is weakened and restructured. This causes the loads that were originally concentrated near the lower roadway to be redistributed through the non-removed area of ​​the coal pillar and its surrounding coal and rock mass. Consequently, the peak stress concentration in the area adjacent to the lower roadway shifts outward to areas farther from the lower roadway, reducing the stress level and deformation driving force of the surrounding rock in the lower roadway. Attached Figure Description

[0018] To more intuitively illustrate the prior art and this application, several exemplary figures are provided below. It should be understood that the specific shapes and structures shown in the figures should not generally be regarded as limiting conditions for implementing this application; for example, based on the technical concept disclosed in this application and the exemplary figures, those skilled in the art are able to easily make conventional adjustments or further optimizations to the addition / reduction / classification, specific shapes, positional relationships, connection methods, size ratios, etc. of certain units (components).

[0019] Figure 1 A schematic diagram of the spatial layout of the lower roadway, safety chamber, roof, removal equipment, upper target coal pillar and goaf provided for one embodiment of this application; Figure 2 A schematic diagram illustrating the spatial projection relationship between the upper target coal pillar and the lower roadway, provided as an embodiment of this application; Figure 3 A schematic diagram of the upper target coal pillar and its decompression cavity provided for another embodiment of this application; Figure 4 A schematic diagram of the spatial layout of the lower roadway, roof, upper target coal pillar, upper working roadway and goaf provided for another embodiment of this application; Figure 5A schematic diagram illustrating the coordination between the roof and the upper target coal pillar, provided for another embodiment of this application; Figure 6 for Figure 5 A cross-sectional view along the direction aa.

[0020] Explanation of reference numerals in the attached figures: 1. Lower roadway; 11. Safety chamber; 2. Upper target coal pillar; 21. Pressure relief cavity; 3. Roof; 31. Pilot hole; 4. Goaf; 5. Removal device; 51. Hole forming device; 511. Drill bit assembly; 52. Sealing and recovery device; 6. Upper working roadway. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0022] In the description of this application: unless otherwise stated, "multiple" means two or more. Expressions such as "including", "comprising", and "having" also mean "not limited to" (certain units, components, materials, steps, etc.).

[0023] refer to Figures 1-6 This application discloses an active pressure relief and roadway stabilization method for overlying residual coal pillars, comprising the following steps: S1: Based on the mine production geological data, determine the stress influence range of the upper target coal pillar 2 on the lower roadway 1, and design and determine one or more pressure relief coal body units within the upper target coal pillar 2. The pressure relief coal body unit shall at least include its spatial location and pressure relief volume. Mine production geological data includes geological data and mining data. These data are used to quantitatively identify and spatially locate the load transfer relationship between the "upper target coal pillar 2 – surrounding rock – lower roadway 1". Geological data should at least include: coal seam depth, coal and rock strata thickness and combination, roof and floor lithology and structural plane development, fault / fold and other structural information, key layer distribution, coal and rock mechanical parameters (such as compressive strength, elastic modulus, internal friction angle, etc.), and original rock stress test or calculation results. Mining data should at least include: the extent of the upper working face goaf 4, the geometric dimensions and location of the coal pillars, the mining process and advancement sequence, the collapse and compaction characteristics of goaf 4, the location of the lower roadway 1, and its spatial correspondence with the coal pillars. Based on the above data, the stress influence range of the upper target coal pillar 2 on the lower roadway 1 can be determined, that is, which roadway sections of the lower roadway 1 are under the influence of coal pillar support pressure or stress concentration, thereby predicting the potential risks of mine pressure manifestation such as roof 3 subsidence, sidewall spalling, floor heave, and increased roadway convergence, and providing boundary conditions for the selection of subsequent pressure relief targets. Furthermore, when designing and determining one or more pressure relief coal body units within the upper target coal pillar 2, by clarifying the spatial location and pressure relief volume of the pressure relief coal body units, the spatial coordinate range and removal boundary of the coal body to be removed can be determined (including the center position, outline, and volume scale of the pressure relief unit), thereby forming an implementable pressure relief plan: ensuring that the pressure relief effect is focused on the bearing parts that contribute more significantly to the stress of the lower roadway 1, and controlling the pressure relief intensity and influence range through the design of the pressure relief volume, realizing the proactive pressure relief pre-design of "fixed point, quantitative, and plannable", laying the foundation for the subsequent formation of pressure relief cavity 21 and induced stress redistribution.

[0024] S2: Remove one or more depressurized coal body units to remove them from the upper target coal pillar 2 and form a depressurized cavity 21 corresponding to the depressurized coal body unit in the upper target coal pillar 2; By forming a pressure relief cavity 21, the concentrated stress peak near the lower roadway 1 is moved outward to a region far away from the lower roadway 1.

[0025] In step S2, after removing one or more depressurized coal body units from the upper target coal pillar 2, one or more depressurized cavities 21 corresponding to the depressurized coal body units are formed within the upper target coal pillar 2. Due to the significant reduction in the bearing capacity and overall stiffness of the cavity region, the transmission path of the overlying load within the coal pillar is weakened and reconstructed. This causes the load, originally concentrated near the lower roadway 1, to be redistributed more frequently through the non-removed area of ​​the coal pillar and its surrounding coal and rock mass. Consequently, the peak stress concentration in the area adjacent to the lower roadway 1 shifts outward to the area far from the lower roadway 1, reducing the stress level and deformation driving force of the surrounding rock of the lower roadway 1. Compared to existing methods that use explosive decompression, CO2 fracturing, and hydraulic fracturing to create fissures within the coal and rock mass to weaken the medium and indirectly induce stress redistribution, this application directly weakens the coal pillar's load-bearing structure by "removing a predetermined volume of coal and forming a cavity." The decompression target is closer to the key load-bearing structure of the coal pillar, and the decompression range and amount can be planned and controlled by the spatial location and volume of the decompressed coal unit, thus making it more conducive to achieving controllable and consistent decompression effects. At the same time, compared to high-disturbance treatment methods such as widening and excavating the lower roadway 1, this application moves the decompression effect forward to the interior of the upper target coal pillar 2, reducing the concentrated load on the lower roadway 1 by changing the load-bearing structure. This reduces the probability and degree of the roadway's surrounding rock entering a state of intense mining pressure manifestation, thereby achieving the technical effect of active decompression and roadway consolidation.

[0026] It should be noted that the number, spatial location, and decompression volume of the decompression coal body units are not arbitrarily set, but can be determined and verified by combining theoretical calculations and numerical simulations, so as to obtain the desired decompression effect while ensuring the overall stability of the coal pillar. Specifically, theoretical calculations can be based on the mining pressure theory and the coal pillar bearing mechanism to analyze the bearing pressure distribution characteristics of the upper target coal pillar 2 and its transmission law to the lower roadway 1. For example, based on the coal pillar width-to-height ratio, the geometric relationship between the coal pillar and the goaf 4, the burial depth and overlying load, and coal and rock mechanical parameters, the stress concentration factor, bearing safety factor, and expected peak stress level near the lower roadway 1 of the coal pillar and its edge area can be calculated, thereby determining the bearing area that needs to be weakened and the target stress reduction range, and based on this, the number, arrangement location, and overall decompression volume range of the decompression coal body units can be initially given. Furthermore, numerical simulations can employ methods such as discrete element method (DEM) or finite element method (FEM) to establish a three-dimensional mechanical model comprising "upper target coal pillar 2 – goaf 4 – roof and floor surrounding rock – lower roadway 1". Coal and rock material parameters, structural surfaces, goaf caving and compaction characteristics, and boundary stress conditions are incorporated into the model. By comparing the stress and displacement field responses under "no pressure relief" and "different pressure relief coal body unit schemes", the outward displacement distance of peak stress near lower roadway 1, the stress reduction magnitude, and the convergence deformation trend of the roadway surrounding rock are evaluated. Simultaneously, the possibility of new excessive concentration or instability risks in the remaining bearing area of ​​the coal pillar is examined. Through the approach of "theoretical calculation providing initial values ​​– numerical simulation for scheme comparison and safety verification", iterative optimization of the pressure relief coal body unit parameters can be achieved, ensuring that while meeting the pressure relief target, the overall stability of the coal pillar and construction feasibility are considered, thereby improving the reliability and engineering adaptability of the active pressure relief roadway stabilization scheme.

[0027] Step S2 includes: selecting a working position in the lower roadway 1, and constructing one or more guide holes 31 upward from the working position, so that the one or more guide holes 31 pass through the roof 3 of the lower roadway 1 and penetrate into the upper target coal pillar 2, and removing the depressurized coal body unit through the guide holes 31.

[0028] In this embodiment, step S2 involves selecting a work location within the lower roadway 1 and constructing a guide hole 31 upwards, thereby creating a controlled work channel between the lower roadway 1 and the upper target coal pillar 2. Since the guide hole 31 passes through the roof 3 of the lower roadway 1 from bottom to top and penetrates into the upper target coal pillar 2, it enables spatial positioning and access to the depressurized coal body unit.

[0029] It should be noted that the lower roadway 1 can be a mining area main roadway, a return roadway (including a transport roadway or a return air roadway), a tunneling roadway, or a connecting roadway, etc. As long as at least part of its roadway section is within the stress influence range of the upper target coal pillar 2, the working position can be selected in the lower roadway 1 to construct the pilot hole 31 and carry out the removal operation of the pressure-relieved coal body unit. The working position can be selected according to the roadway space conditions, support conditions, and construction organization needs to meet the safety and operability of the construction of the pilot hole 31 and the removal operation.

[0030] In step S2, a safety chamber 11 is constructed in the lower roadway 1; and one or more guide holes 31 are constructed upward in an inclined manner on the roof plate 3 of the safety chamber 11; the removal device 5 enters the target coal pillar through the guide holes 31 to cut and crush the depressurized coal body unit, so that the depressurized coal body unit determined by the design is removed.

[0031] In this embodiment, step S2 first involves constructing a safety chamber 11 within the lower roadway 1. The safety chamber 11 is preferably located in a relatively safe position facing or close to the projection area of ​​the upper target coal pillar 2. Through a reasonable chamber cross-section and support arrangement, it satisfies the working space requirements for the construction of the guide hole 31 and the removal operation, while minimizing or eliminating the existing transportation, ventilation, and pedestrian functions of the lower roadway 1. This allows for the establishment of a stable working base without significantly affecting the normal production organization of the lower roadway 1. Subsequently, one or more guide holes 31 are constructed upwards at an angle on the roof 3 of the safety chamber 11. The inclined guide holes 31 can spatially point to the pre-designed and determined stress-relief coal body unit inside the upper target coal pillar 2, forming a controlled channel from the lower roadway 1 to the interior of the target coal pillar. In particular, the construction organization of "pre-depression" can be achieved by the inclined hole layout: before the tunnel face of the lower roadway 1 enters the stress influence range of the upper target coal pillar 2, the guide holes 31 can be constructed and removed in the key bearing area of ​​the coal pillar diagonally above the tunnel face, so that the stress relief cavity 21 is formed before the roadway enters the high stress influence area, thereby weakening the bearing path of the coal pillar in advance, inducing the outward movement of concentrated stress, and reducing the stress level and deformation driving force of the surrounding rock when the roadway passes through later.

[0032] It should be noted that the pilot hole 31 is preferably constructed at an upward angle. The upward angle can be understood as the upward inclination angle of the axis of the pilot hole 31 relative to the horizontal plane. Using an upward angle for the pilot hole 31 can, on the one hand, make it easier for the coal and rock debris generated during the removal process to fall back or migrate along the direction of the pilot hole 31 under the action of gravity, thereby reducing the probability of accumulation and blockage in the hole, ensuring smooth slag discharge, and improving the continuity and construction efficiency of the removal of the pressure-relieved coal body unit. On the other hand, the upward angle of the hole arrangement is conducive to the pilot hole 31 avoiding or weakening the unfavorable intersection with the potential shear failure zone of the roof 3 in space, reducing the risk of shear slippage and hole wall instability of the surrounding rock near the pilot hole 31 under concentrated stress.

[0033] Furthermore, the guide hole 31 can be designed with a large elevation angle, preferably greater than or equal to the shear failure angle of the top plate 3 rock, so as to improve the smoothness of the removal product migration along the channel while satisfying the stability of the guide hole 31.

[0034] In some embodiments, if the inclined guide hole 31 is inconvenient to use due to roadway space, construction organization, or geological conditions, the guide borehole can also be constructed in a vertical direction. In this case, in order to ensure that the depressurized coal body unit can be removed according to the design volume and form the corresponding depressurized cavity 21, the corresponding cutting / breaking path can be adjusted to perform radial rotation scanning around the axis of the guide hole 31, that is, to expand the removal range in segments or layers in the circumferential direction with the guide hole 31 as the center, and form a cavity contour that matches the volume of the depressurized coal body unit through circumferential scanning, so that the depressurized cavity 21 can still play the role of weakening the local bearing capacity of the coal pillar and inducing stress redistribution, thereby achieving the effect of active depressurization and roadway consolidation of the lower roadway 1.

[0035] Safety chamber 11 is equipped with reinforced support, which includes anchor bolt support and / or anchor cable support, and is combined with shotcrete support.

[0036] In this embodiment, the safety chamber 11 serves as the work base for the construction of the pilot hole 31 and the depressurization operation. The stability of the surrounding rock directly affects the safety of personnel and the operation process, as well as the continuity of subsequent depressurization construction. Therefore, the safety chamber 11 is preferably located in a roadway section or stratum with relatively intact surrounding rock conditions and relatively stable lithology, so as to avoid strongly fractured zones, weak interlayers, and tectonic influence zones as much as possible, thereby reducing the risk of initial instability of the surrounding rock. Based on this, by installing reinforced support in safety chamber 11, a combined support system of "anchor bolt support and / or anchor cable support + shotcrete support" is formed: anchor bolt support is used to reinforce and constrain the shallow fractured zone of the surrounding rock, improve the integrity of the surrounding rock and suppress early damage such as delamination and spalling; anchor cable support is used to incorporate the deep stable rock strata of the surrounding rock into the load-bearing system, enhancing the arch effect and overall deformation resistance; shotcrete support is used to seal and reinforce the surface of the surrounding rock, reduce spalling caused by adverse factors such as weathering and water seepage, and form a composite load-bearing structure together with anchor bolts / anchor cables. Through the above-mentioned reinforced support, the overall stability and deformation resistance of the surrounding rock of safety chamber 11 can be significantly improved, providing a reliable safety barrier for stress disturbances that may occur during the construction of pilot hole 31 and the removal of the depressurized coal body unit, thereby effectively protecting the safety of personnel and equipment in the working area and reducing the risk of accidents such as roof falls and spalling during operation.

[0037] After step S2, step S3 is also included: injecting quick-setting filling material into the pressure relief cavity 21 through the guide hole 31, so that the quick-setting filling material solidifies in the pressure relief cavity 21 to construct a flexible support.

[0038] In this embodiment, after forming the pressure relief cavity 21 in step S3, a quick-setting filling material is injected into the pressure relief cavity 21 through the guide hole 31, allowing it to quickly solidify within the cavity to form a flexible load-bearing body, thereby establishing a controllable mechanical transition between "pressure relief" and "stability". Specifically, although the formation of the pressure relief cavity 21 can weaken the local load-bearing capacity of the upper target coal pillar 2 and induce the stress peak to shift outward, the cavity may have the risk of local collapse or gradual collapse under certain geological conditions. Once a sudden collapse occurs, the internal load-bearing structure of the coal pillar will change instantaneously, easily causing a sudden change in stress redistribution, which will then adversely disturb the surrounding rock of the lower roadway 1. After being injected through the guide hole 31, the quick-setting filling material can solidify and harden in a short time and fill the cavity space, transforming the cavity from a "completely unloaded cavity" into a "low-rigidity support with a certain load-bearing capacity". This flexible support can deform to a certain extent when bearing the overlying load and gradually participate in the load-bearing. Thus, it retains the function of the pressure relief cavity 21 in weakening stiffness and promoting the outward shift of peak stress, while also providing buffer support for the surrounding rock of the cavity, suppressing the rapid instability and overall collapse of the cavity boundary, and avoiding stress mutation and impact mine pressure caused by collapse.

[0039] It should be noted that the quick-setting filling material is preferably a low-strength quick-setting filling material, so that it forms a low-stiffness, deformable, flexible load-bearing body after curing, avoiding excessive stiffness that would lead to load reconcentration. The low-strength quick-setting filling material can be quick-setting cement-based material, quick-setting mortar, low-grade cement-mortar system, foamed concrete, foaming material, high-water material, or any combination of the above materials; among them, an appropriate proportion can be selected according to the downhole water content, construction time requirements, and cavity size, and accelerators, expansion agents, or fiber reinforcement components can be added to adjust the setting time, fluidity, and early strength growth characteristics, thereby meeting the construction requirements of injection through the guide hole 31, rapid curing, and formation of a flexible load-bearing body.

[0040] Step S4 is included after step S3: monitoring the deformation of the surrounding rock in the lower roadway 1 and comparing the deformation of the surrounding rock before and after step S2 and / or step S3 to quantitatively evaluate the pressure relief effect.

[0041] In this embodiment, step S4 monitors the deformation of the surrounding rock in the lower roadway 1 and compares the deformation response before and after steps S2 and / or S3 to achieve quantitative verification and feedback control of the stress relief and roadway stabilization effect. Since the lower roadway 1 typically exhibits typical deformation characteristics such as roof subsidence, sidewall convergence, floor heave, and roadway cross-section convergence within the stress-affected zone of the overlying coal pillar, the surrounding rock deformation directly characterizes the stress level and stability of the roadway's surrounding rock. Therefore, continuous or phased monitoring of the surrounding rock deformation can objectively reflect the degree of improvement in the roadway's stress environment after the implementation of stress relief measures. Monitoring methods can employ conventional measurement techniques such as roadway convergence monitoring, roof and floor convergence measurement, sidewall displacement measurement, and cross-sectional change measurement. By comparing the deformation and its growth rate before and after decompression (such as the convergence rate per unit time, the subsidence rate of roof 3, etc.), the formation of decompression cavity 21 and the construction of flexible bearing body can be quantitatively judged to weaken the manifestation of mine pressure, and the reduction of surrounding rock deformation caused by the outward movement of concentrated stress can be verified to meet expectations.

[0042] Furthermore, the quantitative assessment results can serve as a basis for optimizing subsequent construction parameters: when the pressure relief effect is insufficient, pressure relief can be supplemented by increasing the number of pressure-relief coal body units, adjusting their spatial positions, or increasing the pressure relief volume; when monitoring shows abnormal local deformation or stress disturbance risks, risk control can be achieved by adjusting the filling range, filling intensity, or construction rhythm. Thus, step S4 enables the active pressure relief and roadway consolidation process of this application to possess the closed-loop characteristics of being "monitorable, comparable, assessable, and adjustable," improving the verifiability and engineering adaptability of the pressure relief effect, and further ensuring the long-term stability and safe production of the lower roadway 1.

[0043] refer to Figure 4 In some embodiments, step S2 includes: arranging an upper working roadway 6 along the upper target coal pillar 2 in the upper coal seam, the upper working roadway 6 being adjacent to the upper target coal pillar 2, and the upper target coal pillar 2 forming one side of the upper working roadway 6; removing one or more depressurized coal body units in the upper working roadway 6 to form a corresponding depressurized cavity 21 in the upper target coal pillar 2.

[0044] In this embodiment, step S2 involves arranging an upper working roadway 6 along the upper target coal pillar 2 within the upper coal seam, making the working roadway adjacent to the target coal pillar and using the target coal pillar as one side of the working roadway. This creates a stable and accessible working interface on the side of the target coal pillar, enabling the removal of the depressurized coal body unit nearby. Compared to the method of entering the coal pillar through the guide hole 31 of the lower roadway 1 to carry out removal, this embodiment represents another removal path for the depressurized coal body unit: it utilizes the close proximity between the upper working roadway 6 and the target coal pillar, allowing the spatial position of the depressurized coal body unit to be directly located and implemented from the side wall of the coal pillar, reducing the length of the working channel and the number of intermediate rock strata traversed, which is beneficial to improving the operability and construction efficiency of the removal operation.

[0045] The pressure relief cavity 21 penetrates the upper target coal pillar 2.

[0046] In this embodiment, the pressure relief cavity 21 penetrates the upper target coal pillar 2, forming a through hole / cavity running along a predetermined direction inside the target coal pillar. Because the through hole further reduces the effective load-bearing cross-section and overall continuity of the coal pillar, the main load-bearing path of the overlying load inside the coal pillar is more strongly cut off or bypassed, causing stress to redistribute within the coal pillar and surrounding coal and rock mass. This causes the stress peak, originally concentrated in the area adjacent to the lower roadway 1, to shift more towards the remaining load-bearing areas on both sides of the coal pillar and areas further away from the lower roadway 1, thereby achieving a more significant pressure relief effect under certain conditions and further mitigating the mine pressure manifestation in the lower roadway 1. Compared to a non-through, localized pressure relief cavity 21, this through hole form has a more direct effect on changing the load-bearing path inside the coal pillar and a higher pressure relief intensity, making it suitable for working conditions requiring a greater reduction in the load-bearing capacity of the coal pillar.

[0047] refer to Figure 1 This application discloses an active pressure relief and roadway stabilization system for overlying residual coal pillars, comprising: an upper target coal pillar 2, a lower roadway 1, a safety chamber 11, and a removal device 5; The upper target coal pillar 2 is located above the lower roadway 1, and at least a portion of the lower roadway 1 is within the stress influence range of the upper target coal pillar 2. Safety chamber 11 is located in the lower roadway 1, and safety chamber 11 is located within the stress influence range of the upper target coal pillar 2; The removal device 5 is arranged inside the safety chamber 11. One or more guide holes 31 are constructed through the removal device 5. The guide holes 31 extend upward from the top plate 3 of the safety chamber 11 and penetrate into the upper target coal pillar 2. One or more depressurized coal body units are designed within the upper target coal pillar 2, and the number of depressurized coal body units corresponds one-to-one with the number of guide holes 31. The removal device 5 is used to enter the upper target coal pillar 2 through the guide hole 31 to remove the pressure-relieved coal body unit to form a pressure-relieved cavity 21 corresponding to the pressure-relieved coal body unit, thereby shifting the concentrated stress peak near the lower roadway 1 to a region far away from the lower roadway 1.

[0048] The removal device 5 includes: a hole-forming device 51, used to construct the guide hole 31 and cut and crush the depressurized coal body unit; The closed recovery device 52 is connected to the drilling device 51 and is used to recover the rock and coal chips generated by the drilling device 51 during the construction of the guide hole 31 and the cutting and crushing of the depressurized coal body unit.

[0049] In this system implementation, the drilling device 51 can be a drilling rig suitable for high-angle drilling. It uses a drill bit assembly 511 to create a guide hole 31 and cut and crush the pressure-relieved coal body unit within the upper target coal pillar 2. The drill bit assembly 511 can be selected from various forms, such as a high-pressure water jet cutting head, a mechanical milling head, or a jet crushing device for air extraction, depending on the coal and rock conditions and pressure relief requirements, to create a pressure-relief cavity 21 within the target coal pillar that matches the designed pressure-relief volume. The drilling device 51 can be remotely controlled, allowing the cutting and crushing operations to be carried out away from potentially hazardous areas, reducing the risk of exposure to high-stress environments. Simultaneously, a closed recovery device 52 is connected to the drilling device 51, enabling the continuous extraction and recovery of rock and coal chips generated during drilling and cutting / crushing through the guide hole 31. This recovery process can utilize the weight-bearing descent of the rock / coal chips, hydraulic carrying, or mechanical screw conveying for continuous transport, and then centralized collection within the closed recovery device 52.

[0050] The technical features of the above embodiments can be combined in any way (as long as there is no contradiction in the combination of these technical features). For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described; these embodiments not explicitly written should also be considered to be within the scope of this specification.

[0051] The present application has been described in a relatively specific and detailed manner above through general descriptions and specific embodiments. It should be understood that, based on the technical concept of the present application, several conventional adjustments or further innovations can be made to these specific embodiments; however, as long as they do not depart from the technical concept of the present application, the technical solutions obtained by these conventional adjustments or further innovations also fall within the protection scope of the claims of the present application.

Claims

1. A method for active pressure relief and roadway stabilization over a residual coal pillar, characterized in that, The method comprises the following steps: S1: determining the stress influence range of the upper target coal pillar on the lower roadway based on mine production geological data, and designing and determining one or more pressure-relief coal body units in the upper target coal pillar, the pressure-relief coal body unit at least comprising a spatial position and a pressure-relief volume thereof; S2: removing the one or more pressure-relief coal body units to remove them from the upper target coal pillar and form a pressure-relief cavity corresponding to the pressure-relief coal body unit in the upper target coal pillar; By forming the pressure-relief cavity, the concentrated stress peak near the lower roadway is moved to an area far away from the lower roadway.

2. The method of claim 1, wherein, Step S2 comprises: selecting a working position in the lower roadway, and drilling one or more guide holes from the working position upward, so that the one or more guide holes pass through the roof of the lower roadway and penetrate into the upper target coal pillar, and the pressure-relief coal body unit is removed through the guide hole.

3. The method of claim 2, wherein, In step S2, a safety chamber is constructed in the lower roadway, and one or more guide holes are constructed in an inclined manner upward from the roof of the safety chamber; the removal operation device enters the target coal pillar through the guide hole to cut and crush the pressure-relief coal body unit, so that the designed and determined pressure-relief coal body unit is removed.

4. The method of claim 3, wherein, The safety chamber is provided with reinforced support, which comprises anchor rod support and / or anchor cable support, and is matched with shotcrete support.

5. The method of claim 2 or 3, wherein, After step S2, step S3 is further included: injecting rapid-setting filling material into the pressure-relief cavity through the guide hole, so that the rapid-setting filling material is solidified in the pressure-relief cavity to construct a flexible bearing body.

6. The method of claim 5, wherein, After step S3, step S4 is further included: monitoring the deformation amount of the surrounding rock of the lower roadway, and comparing the deformation amount of the surrounding rock before and after step S2 and / or step S3 is implemented, to quantitatively evaluate the pressure-relief effect.

7. The method of claim 1, wherein, Step S2 comprises: arranging an upper working roadway in the upper coal seam along the upper target coal pillar, the upper working roadway being arranged adjacent to the upper target coal pillar, and the upper target coal pillar constituting one side of the roadway in the upper working roadway; and removing the one or more pressure-relief coal body units in the upper working roadway to form a corresponding pressure-relief cavity in the upper target coal pillar.

8. The method of claim 1, wherein, The pressure-relief cavity penetrates through the upper target coal pillar.

9. A self-relieving pressure releasing and roadway stabilizing system overlying a residual coal pillar, characterized in that, Comprise: The upper target coal pillar, the lower roadway, the safety chamber, and the removal operation device; The upper target coal pillar is located above the lower roadway, and at least part of the roadway section of the lower roadway is located in the stress influence range of the upper target coal pillar; The safety chamber is arranged in the lower roadway, and the safety chamber is located in the stress influence range of the upper target coal pillar; The removal operation device is arranged in the safety chamber, and one or more guide holes are drilled by the removal operation device, the guide holes extending upward from the roof of the safety chamber and penetrating into the upper target coal pillar; One or more pressure-relief coal body units are designed and determined in the upper target coal pillar, and the number of pressure-relief coal body units corresponds to the number of guide holes one by one; The removal operation device is used to enter the upper target coal pillar through the guide hole, and remove the pressure-relief coal body unit to form a pressure-relief cavity corresponding to the pressure-relief coal body unit, so as to move the concentrated stress peak near the lower roadway to an area far away from the lower roadway.

10. The active pressure-relief main entry system of claim 9, wherein, The removal operation device comprises a hole-forming device for drilling the guide hole and cutting and crushing the pressure-relief coal body unit. The closed recovery device is arranged in communication with the hole-forming device and is used for recovering the rock and coal cuttings generated in the process of cutting and crushing the pressure-relieved coal body unit during the construction of the guide hole.

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