A system for equalizing the stress of an overlying coal pillar and method of use

Abstract

The present application relates to the technical field of mining engineering, and provides a system for balancing and reducing concentrated stress of an overlying coal pillar and a use method, the system for balancing and reducing concentrated stress of an overlying coal pillar, comprising a borehole stress meter monitoring system and a balancing pressure regulating system, the balancing pressure regulating system comprising a pressure regulating elastic expansion bag, a push tube, a two-way pressure regulating two-way valve, a positioning ring, a push cover, an adjustable pressure regulating four-way valve and a lengthening pipe, etc., the borehole stress meter monitoring system and the balancing pressure regulating system are used for monitoring and regulating throughout the process, and the stress of the coal pillar is significantly reduced, the defects that the traditional pressure relief methods such as hydraulic fracturing and blasting pressure relief of the overlying coal pillar cannot significantly and evenly reduce the concentrated stress of the overlying coal pillar are fundamentally solved, various adverse mining environments affected by the concentrated stress of the overlying coal pillar can be effectively solved, and especially, the safety of the fully mechanized (top coal) working face equipment in the last mining area affected by the overlying coal pillar is ensured to be withdrawn, so that the present application has very wide and important popularization and application value.

Description

Technical Field

[0001] This invention relates to the field of mining engineering technology, specifically to a system and method for balancing and reducing concentrated stress in overlying coal pillars. Background Technology

[0002] Coal seams with close proximity are widely distributed in my country, and most of the overlying coal seams are mined out. It is common for both the overlying and underlying coal seams to be mined simultaneously. Due to the limitation on the width of the stop coal pillar, in order to protect the main roadway of the underlying coal seam, the width of the stop coal pillar of the underlying coal seam generally needs to be greater than that of the overlying coal seam. Thus, the stop line of the working face of the underlying coal seam is located below the goaf of the overlying coal seam. Therefore, the entire mining process of the working face of the underlying coal seam is generally affected by the superposition of the overlying coal pillar, especially in the final (stopped) mining area. It is necessary to withdraw the fully mechanized mining equipment of the entire working face. At this stage, it is constantly affected by the concentrated stress of the overlying coal pillar, making it difficult to ensure the safe withdrawal of the working face equipment. In particular, when the concentrated stress transmitted from the coal pillar to the final (stopped) mining area of ​​the underlying coal seam is large, large-scale linkage instability disasters of the overlying rock are likely to occur.

[0003] Currently, the main methods for reducing stress concentration in overlying coal pillars include hydraulic fracturing, blasting, and shock wave decompression. The first two methods have been tested in underground engineering projects. These methods can only reduce the stress concentration in the overlying coal pillar to a certain extent, but the effect is not obvious and the decompression is uneven. In particular, hydraulic fracturing is constrained by the cracks in the coal pillar, and it is difficult to reach the fracturing pressure required by the design. The fracturing effect will also be greatly reduced. The decompression is uneven throughout the process and the fracturing is uncontrollable. Traditional blasting decompression methods can easily induce instability of the rock strata in some areas due to vibration of the overlying rock, and the decompression is uneven and uncontrollable overall. The principle of the traditional method is mainly to make the overlying coal pillar change from the elastic bearing stage to the plastic bearing stage. Even though it is a plastic coal pillar, the overlying strata height in the coal pillar area is still significantly higher than that in the goaf on both sides due to the supporting effect of the remaining coal. Therefore, the coal pillar still bears most of the overlying strata pressure of the goaf on both sides of the coal pillar. Especially when the coal pillar is thick, this results in the coal pillar having a significant bearing capacity even though it has entered the plastic stage. Therefore, it has a greater concentrated stress than the rock mass in the goaf, which is applied to the surrounding rock space of the underlying rock strata, thus drastically affecting the normal shutdown of the fully mechanized (mining) face.

[0004] For the unmined (shutdown) area of ​​a fully mechanized longwall face, as the hydraulic supports are withdrawn in sequence, the supporting capacity of the roof gradually weakens. In addition, the stress concentration of the overlying coal pillar makes the overlying surrounding rock in the entire shutdown area prone to fracture along the coal pillar area, thus triggering a large-scale instability disaster. Therefore, the requirements for stress relief of the overlying coal pillar in the shutdown area are much higher than those for the surrounding rock under other conditions. For example, it is necessary to significantly reduce the stress in the coal pillar area and to monitor and reduce the impact of concentrated stress in the coal pillar in the shutdown area on the underlying shutdown face and supports in a balanced and controllable manner. Traditional methods cannot achieve such requirements.

[0005] Therefore, a revolutionary new method is needed to address the above problems in a targeted manner, to achieve a significant and balanced release of concentrated stress in the coal pillar, and at the same time, to adjust the overburden stress in the unmined area in real time based on monitoring results, so as to achieve safe withdrawal of equipment from the working face. Summary of the Invention

[0006] The purpose of this invention is to fundamentally solve the shortcomings of traditional pressure relief methods such as hydraulic fracturing and blasting of overlying coal pillars, which cannot significantly and evenly reduce the concentrated stress of the overlying coal pillars. It can effectively address various adverse mining environments affected by the concentrated stress of overlying coal pillars, especially ensuring the safe withdrawal of equipment from fully mechanized (stopped) mining faces in areas affected by overlying coal pillars. In the final (stopped) mining areas of fully mechanized (stopped) mining faces, as hydraulic supports are withdrawn sequentially, the supporting capacity of the roof gradually weakens. Coupled with the stress concentration of the overlying coal pillars, the overlying rock in the entire final (stopped) mining area is prone to fracture along the coal pillar area, leading to large-scale instability disasters. Traditional methods cannot effectively solve these problems. This invention proposes a system and method for evenly reducing the concentrated stress of overlying coal pillars, effectively solving the aforementioned problems.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a system for balancing and reducing concentrated stress in overlying coal pillars, comprising a borehole stress gauge monitoring system and a pressure balancing system. The pressure balancing system includes a pressure-regulating elastic expansion bag, a push pipe, a bidirectional pressure-regulating two-way valve, a left-right rotating nut, a positioning ring, a push cover, a right-angle two-way valve, a T-type three-way valve, an adjustable pressure T-type three-way valve, an adjustable pressure four-way valve, an extension pipe, a left-right rotating nut, and a pressure gauge.

[0008] The pressure-regulating elastic expansion bag has a push tube channel hole in the middle, and a first liquid / gas bolt interface is provided on one side of the end of the pressure-regulating elastic expansion bag. A second liquid / gas bolt interface is arranged on the side of the push tube. One end of the bidirectional pressure-regulating two-way valve is the push tube interface end and the pressure-regulating elastic expansion bag interface end. The bidirectional pressure-regulating two-way valve is connected to the second liquid / gas bolt interface of the push tube through a left-right rotating nut, and the bidirectional pressure-regulating two-way valve is connected to the first liquid / gas bolt interface of the pressure-regulating elastic expansion bag through a left-right rotating nut.

[0009] The positioning ring is fixed to the pressure-regulating elastic expansion bag by the positioning bolt. The maximum diameter of the push cover is larger than the diameter of the pressure-regulating elastic expansion bag in the contracted state. The extension tube is set between the right-angle two-way valve and the T-type three-way valve. The two ends of the extension tube are left-hand and right-hand threaded interfaces, which can be connected to left-hand and right-hand nuts (9a). The right-angle two-way valve and the T-type three-way valve are respectively connected to the left-hand and right-hand nuts. The pressure gauge is connected to the adjustable pressure four-way valve through the left-hand and right-hand nuts.

[0010] The borehole stress gauge monitoring system includes a borehole stress gauge and an information receiver. The number of borehole stress gauges is several, and the borehole stress gauges are installed in the lower part of the overlying coal pillar and in the underlying rock strata of the overlying coal pillar. The information receiver is used to receive the monitoring information from the borehole stress gauges.

[0011] As a further embodiment of the present invention, the push tube is extended by a push tube connecting nut, the push tube connecting nut is provided with a bidirectional regulating valve, the end of the push tube is provided with an end sealing bolt, and the inside of the bidirectional pressure regulating two-way valve is a one-way regulating valve.

[0012] As a further embodiment of the present invention, the middle part of the positioning ring is a first push tube channel, one side of the positioning ring is a first positioning hole, the middle part of the push cover is a second push tube channel, and the side of the push cover is a second positioning hole.

[0013] As a further embodiment of the present invention, a one-way regulating valve is arranged in one end channel of the T-type three-way valve, an active adjustment bolt is threadedly connected to the surface of the adjustable pressure four-way valve, a locking nut is threadedly connected to the outer side of the active adjustment bolt, an adjustment rope and a regulating valve are provided inside the adjustable pressure four-way valve, one end of the adjustment rope is connected to the active adjustment bolt, and the other end is connected to the regulating valve, and a pressure relief hole is provided at the end of the adjustable pressure four-way valve near the regulating valve.

[0014] A method for using a system to evenly reduce concentrated stress in an overlying coal pillar, comprising the following steps:

[0015] Install a borehole stress gauge monitoring system;

[0016] Implement a group of pressure regulating tunnels and install a pressure regulating system;

[0017] Monitoring and equalization voltage regulation.

[0018] As a further aspect of the present invention, the step of installing the borehole stress gauge monitoring system specifically includes:

[0019] The number of borehole stress gauges arranged in the overlying coal pillar is no less than 12, arranged in 4 rows, with no less than 3 in each row. The overlying coal pillar is divided into four areas: the middle area of ​​the coal pillar, the central area of ​​the coal pillar, the area of ​​the support area, the support area of ​​the support frame, and the area of ​​the withdrawal channel, as well as two areas near the goaf of the overlying coal seam. One borehole stress gauge is installed in each of the above areas.

[0020] The number of borehole stress gauges arranged in the underlying rock strata area shall not be less than 20. The position of each borehole stress gauge corresponds one-to-one with the borehole stress gauge arranged in the overlying coal pillar directly above it. In addition, a row of borehole stress gauges shall be arranged in the underlying rock strata area of ​​the overlying coal seam goaf on both sides of each row of borehole stress gauges. This is used to realize the whole process and whole area pressure regulation monitoring of the overlying coal pillar and the underlying rock strata area of ​​the coal pillar in the unmined area, and to adjust the borehole spacing and borehole diameter through monitoring data, and to provide a basis for pressure regulation in the pressure regulating tunnel.

[0021] As a further aspect of the present invention, the steps of implementing the pressure regulating tunnel group and installing the pressure regulating system specifically include:

[0022] Step 1: Using mechanical tunneling equipment, one or more pressure regulating tunnels of a certain length are arranged at regular intervals inside the overlying coal pillar from the main roadway of the overlying coal seam. The pressure regulating tunnel group includes pressure regulating tunnels in the middle area of ​​the coal pillar, pressure regulating tunnels in the right side area of ​​the coal pillar, and pressure regulating tunnels in the left side area of ​​the coal pillar. The two ends of the pressure regulating tunnel group are variable diameter sections, and the middle is a cylindrical section. The variable diameter section is divided into a smooth expansion section, a smooth necking section, a stepped expansion section, and a stepped necking section. It is preferred to implement the pressure regulating tunnel group in the middle area of ​​the coal pillar to achieve early release of coal pillar pressure.

[0023] Step 2: Connect the push pipe, push pipe connecting nut, pressure regulating elastic expansion bag, end sealing bolt, left and right turning nut, push cover, two-way pressure regulating two-way valve, and positioning ring into a whole, and push the whole into the cavity of the pressure regulating tunnel group in the middle area of ​​the coal pillar, and inject gas or liquid at a certain pressure.

[0024] Step 3: Implement the other pressure regulating tunnels in the same manner as Steps 1 and 2;

[0025] Step 4: The push pipes between each pressure regulating hole are connected into a complete pressure regulating system through a two-way pressure regulating two-way valve, a right-angle two-way valve, a T-type three-way valve, an extension pipe, an adjustable four-way valve, a left- or right-hand rotating nut, and a push pipe connecting nut, and a certain pressure of gas or liquid is injected to achieve the designed pressure value.

[0026] Step 5: Through subsequent monitoring, pressure is adjusted by actively adjusting bolts, so that the pressure regulating tunnel gradually deforms and narrows, the pressure is gradually released evenly, the roof of the coal pillar area gradually sinks, the overburden height of the coal pillar area and the overlying coal seam goaf gradually becomes consistent, the overall stability of the overburden is qualitatively improved, the pressure of the overlying coal pillar in the unmined area is significantly reduced and balanced, and the safe withdrawal of the working face equipment is ensured.

[0027] As a further aspect of the present invention, the steps of monitoring and equalizing voltage regulation specifically include:

[0028] Step 1: Before drilling the pressure regulating tunnel group, the pre-positioned borehole stress gauges need to monitor the pressure changes inside the coal pillar. All the pressure regulating elastic expansion bags in the pressure regulating tunnel group are filled with liquid or gas to support the pressure regulating tunnel walls, so that the pressure regulating of the pressure regulating tunnel group is in a gradual pressure regulating process, and can ensure that the overlying coal pillar will not suddenly become unstable.

[0029] Step 2: Implement subsequent pressure regulating tunnel groups and install pressure regulating elastic expansion bags in sequence. Adjust the parameters of the pressure regulating tunnel groups according to the monitoring results. After the implementation of multiple pressure regulating tunnel groups, if the pressure reduction of the overlying coal pillar is not significant, it is necessary to further reduce the spacing between pressure regulating tunnels and increase the diameter of the pressure regulating tunnels. The length of the pressure regulating elastic expansion bags should be 1-10m, and the expanded diameter can match the diameter of the pressure regulating tunnel. The spacing between the pressure regulating elastic expansion bags should be 0-5m. The diameter of the pressure regulating tunnel includes the diameter of the pressure regulating tunnels in the two side areas and the diameter of the pressure regulating tunnel in the middle area.

[0030] Step 3: After installing the pressure regulating system, monitor the data changes of the borehole stress gauge and pressure gauge, as well as the pressure relief status of the pressure relief system. Gradually reduce the pressure value of the pressure regulating system through the adjustable four-way valve, thereby further reducing the stress concentration of the coal pillar in a balanced manner.

[0031] Step 4: As the working face is mined back to the final mining area until mining stops, the pre-mining dynamic stress will inevitably cause abnormal increases in the borehole stress gauge data. The pressure value of the pressure regulating system is gradually reduced by using an adjustable four-way valve, thereby further balancing and reducing the stress concentration of the coal pillar until all working face supports are safely withdrawn.

[0032] As a further aspect of the present invention, when multiple pressure regulating tunnels are implemented, the upper pressure regulating tunnel is implemented first, followed by the lower pressure regulating tunnel. The interlayer spacing of each pressure regulating tunnel should be 0-3m, and the length difference between each pressure regulating tunnel should be 2-10m. The upper pressure regulating tunnel is longer and the lower pressure regulating tunnel is shorter, or the upper pressure regulating tunnel is shorter and the lower pressure regulating tunnel is longer, thereby forming an interlayer transition zone.

[0033] As a further aspect of the present invention, the spacing between the pressure regulating tunnels should preferably be 0-5m; the smaller the spacing, the greater the reduction in coal pillar pressure.

[0034] The diameter of the pressure regulating tunnels in the two side zones and the middle zone should preferably be 0.3-1.5m. The larger the diameter, the greater the reduction in coal pillar pressure.

[0035] When the thickness of the overlying coal pillar is less than 3.5m, only one layer of pressure regulating tunnels is needed. When the thickness of the overlying coal pillar is greater than or equal to 3.5m and less than 8m, one to two layers of pressure regulating tunnels can be implemented. When the thickness of the overlying coal pillar is greater than or equal to 8m, two or more layers of pressure regulating tunnels can be implemented. The more layers of pressure regulating tunnels there are, the greater the reduction in coal pillar pressure.

[0036] The beneficial effects of the present invention are: (1) Pressure regulation can be achieved for coal pillars left from thin coal seams to extra-thick coal seams, significantly and evenly reducing stress concentration in coal pillars, and achieving balanced pressure regulation throughout the process;

[0037] It can be implemented under various conditions regardless of whether coal pillar fractures are developed;

[0038] No matter how complex the coal pillar stress is, it can be implemented and achieve balanced pressure regulation throughout the entire process;

[0039] The working face is established before it is far from the cessation of mining, so it does not affect the mining progress of the working face and the construction conditions are excellent.

[0040] All the pressure regulating elastic expansion bags in the pressure regulating system are connected by bidirectional pressure regulating two-way valves, which realizes both independent pressure regulation and the formation of an overall balanced pressure regulating system. In this way, if a pressure regulating elastic expansion bag is damaged and leaks liquid / gas, it will not affect the balanced and stable pressure regulation of the entire pressure regulating system.

[0041] Each push tube is connected by a push tube connecting nut (bidirectional pressure adjustment). Even if the top plate behind the support area is cut off, causing some push tubes to be severed, it will not affect the normal operation of the remaining pressure adjustment system.

[0042] By monitoring the pressure values ​​of the borehole stress gauge monitoring system and the pressure regulating system, the pressure regulating system ultimately increases or decreases the pressure by driving the regulating rope through the active regulating bolt of the adjustable four-way valve, so as to realize the regulating valve's pressure regulating capability. This allows the entire system to automatically regulate pressure and also control and balance, avoiding stress concentration and pressure overload.

[0043] The entire monitoring and pressure regulation system is convenient and quick to use, and provides balanced and controlled pressure regulation throughout the entire process. It has a wide range of important application value and solves key problems that traditional methods cannot solve. This invention fundamentally solves the shortcomings of traditional on-site pressure relief methods such as hydraulic fracturing and blasting of overlying coal pillars, which cannot significantly and evenly reduce the concentrated stress of overlying coal pillars. It can effectively solve various adverse mining environments affected by the concentrated stress of overlying coal pillars, especially ensuring the safe withdrawal of equipment in fully mechanized (release) faces in the unmined areas affected by overlying coal pillars. It has a wide range of important application value. Attached Figure Description

[0044] Figure 1This is a schematic diagram of a pressure-regulating elastic expansion bag structure.

[0045] Figure 2 A schematic diagram of the push tube and the push tube connecting nut;

[0046] Figure 3 This is a schematic diagram of a two-way pressure regulating valve.

[0047] Figure 4 This is a schematic diagram of the positioning ring.

[0048] Figure 5 A schematic diagram of the push shield structure;

[0049] Figure 6 This is a schematic diagram illustrating the connection process of the elastic shrink bag and its accessories.

[0050] Figure 7 This is a schematic diagram showing the connection between the elastic expansion bag and the push tube;

[0051] Figure 8 This is a schematic diagram of the expanded state of the elastic shrink bag;

[0052] Figure 9 Schematic diagram and cross-sectional view of a right-angle two-way valve;

[0053] Figure 10 Schematic diagram and cross-sectional view of a T-type three-way valve;

[0054] Figure 11 Schematic diagram and cross-sectional view of an adjustable pressure T-type three-way valve;

[0055] Figure 12 This is a schematic diagram of an adjustable pressure four-way valve and its cross-section.

[0056] Figure 13 This is a schematic diagram of the extension pipe;

[0057] Figure 14 Pressure indicates intent;

[0058] Figure 15 The pressure regulating system only has an elastic expansion bag (cylindrical shape);

[0059] Figure 16 This is a schematic diagram of a pressure regulating system using an elastic expansion bag (cylindrical) and an elastic expansion bag (expanded diameter).

[0060] Figure 17 This is a schematic diagram of a pressure regulating system using an elastic expansion bag (cylindrical) and an elastic expansion bag (reduced diameter).

[0061] Figure 18 This is a schematic diagram of a pressure regulating system using elastic expansion bags (cylindrical) and elastic expansion bags (reduced diameter and expanded diameter).

[0062] Figure 19 Schematic diagram for arranging borehole stress gauges;

[0063] Figure 20 This is a schematic diagram showing that the length of the pressure regulating tunnel in the middle of the coal pillar in area A and area C is greater than the length of the pressure regulating tunnels on the left and right sides of the coal pillar.

[0064] Figure 21 for Figure 20 Schematic diagram of the first type II cross section;

[0065] Figure 22 for Figure 20 The second type II cross-sectional schematic diagram (if two layers of surge tanks are implemented, and the two layers of surge tanks are arranged overlapping vertically).

[0066] Figure 23 for Figure 20 The third type II cross-section schematic diagram (if two layers of surge tanks are implemented, and the two layers of surge tanks are staggered vertically).

[0067] Figure 24 for Figure 20 A schematic diagram of the fourth type II cross section (the middle section is a larger pressure regulating tunnel, and the two sides are smaller pressure regulating tunnels arranged in two layers).

[0068] Figure 25 for Figure 20 Schematic diagram of the first type II-II section;

[0069] Figure 26 for Figure 20 The second type II-II cross-sectional schematic diagram (if two layers of pressure regulating tunnels are implemented, and the lengths of the pressure regulating tunnels in the corresponding areas of the upper and lower layers are the same);

[0070] Figure 27 for Figure 20 The third type II-II cross-sectional schematic diagram (if two layers of pressure regulating tunnels are implemented, and the length of the pressure regulating tunnels in the corresponding areas of the upper and lower layers is shorter at the top and longer at the bottom);

[0071] Figure 28 for Figure 20 Schematic diagram of the fourth type II-II section (if two layers of pressure regulating tunnels are implemented, and the length of the pressure regulating tunnels in the corresponding areas of the upper and lower layers is longer at the top and shorter at the bottom);

[0072] Figure 29 for Figure 20 The diagram shows the variable diameter section when it is a stepped expansion or necking.

[0073] Figure 30 for Figure 29 Schematic diagram of section II-II;

[0074] Figure 31This is a schematic diagram showing that the pressure regulating tunnels in area C of the pressure regulating tunnel group are of equal length, while the middle section of area A is longer and the two sides are shorter.

[0075] Figure 32 This is a schematic diagram showing that the pressure regulating tunnels in area C of the pressure regulating tunnel group are of equal length, and the pressure regulating tunnels in area A are also of equal length.

[0076] Figure 33 This is a schematic diagram showing that the lengths of the pressure regulating tunnels in area C of the pressure regulating tunnel group are equal, while the lengths in area A decrease sequentially from the left to the right of the coal pillar.

[0077] Figure 34 This is a schematic diagram showing that the lengths of the pressure regulating tunnels in area C of the pressure regulating tunnel group are equal, while the lengths in area A decrease sequentially from the right side of the coal pillar to the left side.

[0078] Figure 35 This is a schematic diagram showing that the pressure regulating tunnels in area C of the pressure regulating tunnel group are of equal length, while those in area A are shorter in the middle of the coal pillar and longer on both sides.

[0079] Figure 36 The diagram shows the length of the pressure regulating tunnel in Zone A of the pressure regulating tunnel group, where the middle section of the coal pillar is shorter and the side sections are longer. The diagram also shows that Zone A has a longer middle section of the coal pillar and shorter side sections.

[0080] Figure 37 This is a schematic diagram showing that the pressure regulating tunnels in area A of the pressure regulating tunnel group are of equal length, while those in area C are longer in the middle of the coal pillar and shorter on both sides.

[0081] Figure 38 for Figure 20 A schematic diagram showing the installation of pressure regulating systems in all pressure regulating tunnels;

[0082] Figure 39 for Figure 38 Schematic diagram of the first type II cross section;

[0083] Figure 40 for Figure 38 The second type II cross-sectional schematic diagram (if two layers of surge tanks are implemented, and the two layers of surge tanks are arranged overlapping vertically).

[0084] Figure 41 for Figure 38 The third type II cross-section schematic diagram (if two layers of surge tanks are implemented, and the two layers of surge tanks are staggered vertically).

[0085] Figure 42 for Figure 38 A schematic diagram of the fourth type II cross section (the middle section is a larger pressure regulating tunnel, and the two sides are smaller pressure regulating tunnels arranged in two layers).

[0086] Figure 43 for Figure 20 A schematic diagram showing that neither area A nor area C of the pressure regulating tunnel has a pressure regulating system installed.

[0087] Figure 44 for Figure 20 A schematic diagram showing that no pressure regulating system is installed in area A of the pressure regulating tunnel;

[0088] Reference numerals: 1-Pressure-regulating elastic expansion bag, 1a-First liquid / gas bolt interface, 1b-Push tube channel hole, 2-Push tube, 2a-Second liquid / gas bolt interface, 2c-Push tube connecting nut, 2c1-One-way pressure regulating valve, 2b-End sealing bolt, 3-Two-way pressure regulating valve, 3a-Push tube interface end, 3b-Pressure-regulating elastic expansion bag interface end, 3c-One-way regulating valve, 4-Positioning ring, 4a-First positioning hole, 4b-First push tube channel, 4d-Positioning bolt, 5-Push cover. 5a-Second positioning hole, 5b-Second push pipe channel, 6-Right-angle two-way valve, 7-T-type three-way valve, 77-Adjustable pressure T-type three-way valve, 77a-One-way pressure regulating valve, 8-Adjustable pressure four-way valve, 8a-Active resistance adjusting bolt, 8b-Locking nut, 8c-One-way pressure regulating valve, 8d-Resistance adjusting rope, 8e-Pressure relief hole, 9-Extension pipe, 9a-Left and right turn nut, 10-Pressure gauge, 11-Overlying coal pillar, 11c-Pressure regulating tunnel group, 11c0-Small drill section, 11cc-Middle area regulation of coal pillar Pressure regulating tunnel, 11cy - Pressure regulating tunnel on the right side of the coal pillar, 11cz - Pressure regulating tunnel on the left side of the coal pillar, 11a - Load curve of the overlying coal pillar after pressure regulation, 11b - Load curve of the overlying coal pillar before pressure regulation, 12 - Overlying coal seam goaf, 13 - Overlying coal seam stop mining line, 14 - Overlying coal seam stop mining line, 15 - Overlying coal seam main roadway, 16 - Borehole stress gauge, 16a - Information receiver, 17 - Underlying strata area, 1D1 - Pressure regulating system layout in area B, 1D2 - Pressure regulating system layout in areas B and A. Pressure regulating systems are installed in both areas 1D3-B and C; pressure regulating systems are installed in areas 1D4-A, B, and C; m1 - distance from the pressure regulating tunnel to the overlying coal seam goaf; m0 - spacing between pressure regulating tunnels; d1 - diameter of pressure regulating tunnels in the two side areas; d0 - diameter of pressure regulating tunnels in the central area; b1 - length of buffer zone in area B (core area 1); b2 - length of support area in area B (core area 2); b3 - length of withdrawal channel area in area B (core area 3); b4 - length of buffer zone in area B (core area 4). Detailed Implementation

[0089] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0090] The specific implementation of the present invention will be described in detail below with reference to specific embodiments. Example 1

[0091] Please refer to 1 Figures 1 to 20The present invention provides a system for balancing and reducing concentrated stress in overlying coal pillars, characterized in that it includes a borehole stress gauge monitoring system and a pressure equalization system. The pressure equalization system includes a pressure-regulating elastic expansion bag 1, a push pipe 2, a bidirectional pressure-regulating two-way valve 3, a left-right rotating nut 9a, a positioning ring 4, a push cover 5, a right-angle two-way valve 6, a T-type three-way valve 7, an adjustable pressure T-type three-way valve 77, an adjustable pressure four-way valve 8, an extension pipe 9, a left-right rotating nut 9a, and a pressure gauge 10.

[0092] The pressure-regulating elastic expansion bag 1 has a push tube channel hole 1b in the middle, and a first liquid / gas bolt interface 1a is provided on one side of the end of the pressure-regulating elastic expansion bag 1. A second liquid / gas bolt interface 2a is arranged on the side of the push tube 2. One end of the bidirectional pressure-regulating two-way valve 3 is the push tube interface end 3a and the pressure-regulating elastic expansion bag interface end 3b. The bidirectional pressure-regulating two-way valve 3 is connected to the second liquid / gas bolt interface 2a of the push tube 2 through a left-right rotating nut 9a, and the bidirectional pressure-regulating two-way valve 3 is connected to the first liquid / gas bolt interface 1a of the pressure-regulating elastic expansion bag 1 through a left-right rotating nut 9a.

[0093] The positioning ring 4 is fixed to the pressure-regulating elastic expansion bag 1 by the positioning bolt 4d. The maximum diameter of the push cover 5 is greater than the diameter of the pressure-regulating elastic expansion bag 1 in the contracted state. The extension tube 9 is set between the right-angle two-way valve 6 and the T-type three-way valve 7. The two ends of the extension tube 9 are left-hand and right-hand threaded interfaces, which can be connected to left-hand and right-hand nuts 9a. The right-angle two-way valve 6 and the T-type three-way valve 7 are respectively connected to the left-hand and right-hand nuts 9a. The pressure gauge 10 is connected to the adjustable pressure four-way valve 8 through the left-hand and right-hand nuts 9a.

[0094] The borehole stress gauge monitoring system includes a borehole stress gauge 16 and an information receiver 16a. There are several borehole stress gauges 16 installed in the lower part of the overlying coal pillar 11 and the underlying rock stratum 17 of the overlying coal pillar 11. The information receiver 16a is used to receive the monitoring information of the borehole stress gauges 16.

[0095] Furthermore, the push tube 2 is extended by a push tube connecting nut 2c, and a two-way regulating valve 2c1 is provided inside the push tube connecting nut 2c. An end sealing bolt 2b is provided on the surface of the push tube 2, and the interior of the two-way pressure regulating valve 3 is a one-way regulating valve 3c.

[0096] Furthermore, the middle part of the positioning ring 4 is the first push tube channel 4b, one side of the positioning ring 4 is the first positioning hole 4a, the middle part of the push cover 5 is the second push tube channel 5b, and the side of the push cover 5 is the second positioning hole 5a.

[0097] Furthermore, a one-way regulating valve 77a is arranged in one end channel of the adjustable pressure T-type three-way valve 77, wherein the adjustable pressure T-type three-way valve 77 is used for one-way liquid / gas injection. An active adjustment bolt 8a is threadedly connected to the pipe wall of the adjustable pressure four-way valve 8, and a locking nut 8b is threadedly connected to the outer side of the active adjustment bolt 8a. An adjustment rope 8d and a regulating valve 8c are provided inside the adjustable pressure four-way valve 8. One end of the adjustment rope 8d is connected to the active adjustment bolt 8a, and the other end is connected to the regulating valve 8c. A pressure relief hole 8e is provided at the end of the adjustable pressure four-way valve 8 near the regulating valve 8c.

[0098] Please see Figures 1 to 44 A method for using a system to evenly reduce concentrated stress in an overlying coal pillar, comprising the following steps:

[0099] Install a borehole stress gauge monitoring system;

[0100] Implement a group of pressure regulating tunnels and install a pressure regulating system;

[0101] Monitoring and equalization voltage regulation.

[0102] Please see Figures 1 to 44 Furthermore, the steps for installing the borehole stress gauge monitoring system specifically include:

[0103] Step 1: The number of borehole stress gauges 16 arranged in the overlying coal pillar 11 shall not be less than 12, arranged in 4 rows, with no less than 3 in each row. The overlying coal pillar 11 shall be divided into four areas: the middle area of ​​the coal pillar, the middle area of ​​the coal pillar, the middle area of ​​the coal pillar, the middle area of ​​the coal pillar, the middle area of ​​the coal pillar, and ...

[0104] Step 2: The number of borehole stress gauges 16 arranged in the underlying rock stratum area 17 shall not be less than 20. The position of each borehole stress gauge 16 corresponds one-to-one with the borehole stress gauge 16 arranged in the overlying coal pillar 11 directly above it. In addition, a row of borehole stress gauges 16 shall be arranged in the underlying rock stratum area of ​​the overlying coal seam goaf 12 on both sides of each row of borehole stress gauges 16. This is used to realize the full-process and full-area pressure regulation monitoring of the overlying coal pillar 11 and the underlying rock stratum area 17 of the coal pillar in the unmined area, and to adjust the borehole spacing and borehole diameter through monitoring data, and to provide a basis for pressure regulation of the pressure regulating tunnel.

[0105] Please see Figures 1 to 44 Furthermore, the steps of implementing the pressure regulating tunnel group and installing the pressure regulating system specifically include:

[0106] Step 1: Using mechanical drilling equipment, one or more pressure regulating tunnel groups 11c of a certain length are arranged at regular intervals inside the overlying coal pillar 11 from the main roadway 15 of the overlying coal seam. Above the pressure regulating tunnel group 11c is a small borehole section 11c0. The pressure regulating tunnel group 11c includes a pressure regulating tunnel 11cc in the middle area of ​​the coal pillar, a pressure regulating tunnel 11cy in the right side area of ​​the coal pillar, and a pressure regulating tunnel 11cz in the left side area of ​​the coal pillar. The two ends of the pressure regulating tunnel group 11c are variable diameter sections, and the middle part is a cylindrical section. The variable diameter section is divided into a smooth expansion area, a smooth necking area, a stepped expansion area, and a stepped necking area. It is preferred to implement the pressure regulating tunnel group 11cc in the middle area of ​​the coal pillar to achieve early release of coal pillar pressure.

[0107] Step 2: Connect the push pipe 2, push pipe connecting nut 2c, pressure regulating elastic expansion bag 1, end sealing bolt 2b, left and right turning nut 9a, push cover 5, two-way pressure regulating two-way valve 3, and positioning ring 4 into a whole, and push the whole into the cavity of the coal pillar pressure regulating hole 11cc, and inject gas or liquid at a certain pressure.

[0108] Step 3: Implement the other pressure regulating tunnels in the same manner as Steps 1 and 2;

[0109] Step 4: The push pipes 2 between each pressure regulating hole are connected into a complete pressure regulating system through the two-way pressure regulating two-way valve 3, right-angle two-way valve 6, T-type three-way valve 7, extension pipe 9, adjustable pressure four-way valve 8, left and right turn nut 9a and push pipe connecting nut 2c, and a certain pressure of gas or liquid is injected to reach the designed pressure value.

[0110] Step 5: Through subsequent monitoring, pressure is adjusted by active adjustment bolt 8a, so that the pressure adjustment tunnel gradually deforms and narrows, the pressure is gradually released evenly, the roof of the coal pillar area gradually sinks, the overburden height of the coal pillar area and the overlying coal seam goaf 12 gradually becomes consistent, the overall stability of the overburden is qualitatively improved, the pressure of the overlying coal pillar 11 in the unmined area is significantly reduced and balanced, and the safe withdrawal of the working face equipment is ensured.

[0111] Please see Figures 1 to 44 Furthermore, the monitoring and voltage equalization adjustment steps specifically include:

[0112] Step 1: Before drilling the pressure regulating tunnel group 11c, the pre-positioned borehole stress gauges 16 need to monitor the pressure changes inside the coal pillar. All the pressure regulating elastic expansion bags 1 of the pressure regulating tunnel group 11c are filled with liquid or gas to support the pressure regulating tunnel wall, so that the pressure regulation of the pressure regulating tunnel group 11c is in a gradual pressure regulation process, and can ensure that the overlying coal pillar 11 will not suddenly become unstable.

[0113] Step 2: Implement the subsequent pressure regulating tunnel group 11c and install the pressure regulating elastic expansion bag 1 in sequence. Adjust the parameters of the pressure regulating tunnel group 11c according to the monitoring results. After the implementation of multiple pressure regulating tunnel groups 11c, if the pressure reduction of the overlying coal pillar 11 is not obvious, it is necessary to further reduce the spacing m0 between the pressure regulating tunnels and increase the diameter of the pressure regulating tunnels. The length of the pressure regulating elastic expansion bag 1 should be 1-10m, and the expanded diameter can match the size of the pressure regulating tunnel diameter. The spacing between the pressure regulating elastic expansion bags 1 should be 0-5m. The diameter of the pressure regulating tunnel includes the diameter d1 of the pressure regulating tunnels in the two side areas and the diameter d0 of the pressure regulating tunnels in the middle area.

[0114] Step 3: After the pressure regulating system is installed, monitor the data changes of the borehole stress gauge 16 and pressure gauge 10 and the pressure relief status of the pressure regulating system. Gradually reduce the pressure value of the pressure regulating system through the adjustable four-way valve 8, thereby further reducing the stress concentration of the coal pillar in a balanced manner.

[0115] Step Four: As the working face is mined back to the final mining area until mining ceases, the stress from the advance mining will inevitably cause an abnormal increase in the data of borehole stress gauge 16. The pressure value of the pressure regulating system will be gradually reduced using the adjustable four-way valve 8, thereby further equalizing and reducing the stress concentration of the coal pillar until all working face supports are safely withdrawn. (See Appendix) Figures 21 to 24 The load curve of the overlying coal pillar after pressure regulation 11a and the load curve of the overlying coal pillar before pressure regulation (two types) (one peak area and two peak areas) 11b.

[0116] Furthermore, the arrangement and parameters of the aforementioned single-layer pressure regulating tunnel group are as follows:

[0117] Please see Figures 1 to 44 From the perspective of the working face advance direction, the pressure regulating tunnel group in the final mining area is in the following order: Area A - step transition zone → Area B - core area → Area C - step transition zone.

[0118] (a) The pressure regulating tunnel group A-stage transition zone is mainly divided into four types:

[0119] ⑨ Equal-length surge tank: The surge tanks on the left, right and middle sides of the coal pillar are all equal-length expansion zones;

[0120] ⑩ Short pressure regulating tunnels on both sides and long pressure regulating tunnel in the middle: The pressure regulating tunnels on the left and right sides of the coal pillar are expansion zones, and the pressure regulating tunnel in the middle of the coal pillar is an expansion zone plus a cylindrical zone;

[0121] ⑪ Type with long pressure regulating tunnels on both sides and short pressure regulating tunnel in the middle: The pressure regulating tunnels on the left and right sides of the coal pillar are expansion zone + cylindrical zone, and the pressure regulating tunnel in the middle of the coal pillar is expansion zone;

[0122] ⑫ Type of pressure regulating tunnel that gradually lengthens from one side to the other: The length of the pressure regulating tunnel increases from the left to the right of the coal pillar, successively forming the expansion zone and the expansion zone + cylindrical zone; or the length of the pressure regulating tunnel increases from the right to the left of the coal pillar, successively forming the expansion zone and the expansion zone + cylindrical zone.

[0123] (b) The working face advance direction, the pressure regulating tunnel group B area - core area is mainly of one type:

[0124] Buffer zone (core zone 1) → support zone (core zone 2) → withdrawal channel zone (core zone 3) → coal pillar buffer zone in front of the stop mining line (core zone 4). The left, right and middle pressure regulating tunnels of the coal pillars in core zones 1 to 4 are all cylindrical. The stop mining line includes the stop mining line 13 of the underlying coal seam and the stop mining line 14 of the overlying coal seam.

[0125] b1 is the buffer length of area B (core area 1), and its value should be in the range of 2-15m;

[0126] b2 is the length of the support area of ​​Zone B (Core Zone 2), which is 4-6m long;

[0127] b3 is the length of the retreat channel in Zone B (Core Zone 3), which is 2-5m long;

[0128] b4 is the buffer length of area B (core area four), and its value should be in the range of 2-15m;

[0129] (c) The working face advancing direction, the pressure regulating tunnel group C area - the step transition zone is mainly divided into three types:

[0130] ① Equal-length pressure regulating tunnels: The pressure regulating tunnels on the left, right, and middle sides of the coal pillar are all equal-length narrowing zones;

[0131] ② The pressure regulating tunnels on both sides are short and the pressure regulating tunnel in the middle is long: the pressure regulating tunnels on the left and right sides of the coal pillar are narrowing zones, and the pressure regulating tunnel in the middle of the coal pillar is a cylindrical zone plus a narrowing zone;

[0132] ③ The type with long pressure regulating tunnels on both sides and short pressure regulating tunnel in the middle: The pressure regulating tunnels on the left and right sides of the coal pillar are cylindrical areas plus narrowing areas, and the pressure regulating tunnel in the middle of the coal pillar is a narrowing area;

[0133] ④ Type of pressure regulating tunnel that gradually lengthens from one side to the other: The length of the pressure regulating tunnel increases from one side to the other, successively forming a narrowing zone, a cylindrical zone, and a narrowing zone.

[0134] The lengths of the expansion zone in area A and the necking zone in area C should preferably be 1-5m;

[0135] The length of the cylindrical pressure regulating tunnel in areas A and C should preferably be 2-15m.

[0136] Please see Figures 1 to 44Furthermore, when implementing pressure regulating tunnels in multiple layers, the upper layer pressure regulating tunnel should be implemented first, followed by the lower layer pressure regulating tunnel. The spacing between each layer of pressure regulating tunnels should be 0-3m, and the length difference between each layer of pressure regulating tunnels should be 2-10m. The upper layer pressure regulating tunnel is longer and the lower layer pressure regulating tunnel is shorter, or the upper layer pressure regulating tunnel is shorter and the lower layer pressure regulating tunnel is longer, thus forming an interlayer transition zone.

[0137] Please see Figures 1 to 44 Furthermore, the spacing m0 between the pressure regulating tunnels should preferably be 0-5m. The smaller the spacing, the greater the reduction in coal pillar pressure.

[0138] The diameters d1 and d0 of the pressure regulating tunnels in the two side zones and the middle zone should be 0.3-1.5m. The larger the diameter, the greater the reduction in coal pillar pressure.

[0139] When the thickness of the overlying coal pillar 11 is less than 3.5m, only one layer of pressure regulating tunnel group 11c needs to be implemented. When the thickness of the overlying coal pillar 11 is greater than or equal to 3.5m and less than 8m, 1-2 layers of pressure regulating tunnel group 11c can be implemented. When the thickness of the overlying coal pillar 11 is greater than or equal to 8m, 2 or more layers of pressure regulating tunnel group 11c can be implemented. The more layers of pressure regulating tunnel group 11c, the greater the reduction in coal pillar pressure.

[0140] Please see Figures 1 to 44 Furthermore, the voltage regulating system has four types of arrangement:

[0141] Type 1 voltage regulation system: The voltage regulation system is only arranged in the B-core area, which is referred to as the B-zone voltage regulation system type 1D1.

[0142] The second type of voltage regulation system: a voltage regulation system is arranged in both the core area of ​​area B and the step transition area of ​​area A, which is referred to as type 1D2, where voltage regulation system is arranged in area B and area A.

[0143] The third type of voltage regulation system: a voltage regulation system is arranged in both the core area of ​​area B and the step transition area of ​​area C, which is referred to as type 1D3 where a voltage regulation system is arranged in both areas B and C.

[0144] The fourth type of voltage regulating system: voltage regulating systems are arranged in areas A, B and C simultaneously, referred to as type 1D4, where voltage regulating systems are arranged in areas A, B and C.

[0145] In the four arrangement methods of the pressure regulating system, the pressure regulating elastic expansion bag 1 can be arranged in each pressure regulating hole, or the pressure regulating elastic expansion bag 1 can be arranged in each pressure regulating hole at intervals. Example 2

[0146] like Figure 39 and 38The pressure regulating tunnel is long in the middle and short on both sides. It adopts a 1D4 type pressure regulating system and is arranged in a single layer. The rest of the structural parts of this embodiment are the same as those of embodiment 1. Example 3

[0147] like Figure 38 and 40 The pressure regulating tunnel is long in the middle and short on both sides. The pressure regulating system 1D4 is arranged in areas A, B and C, and a double-layer pressure regulating tunnel is arranged (the positions of the double-layer pressure regulating tunnels are corresponding vertically). The rest of the structural parts of this embodiment are the same as those of embodiment 1. Example 4

[0148] like Figure 38 and 41 The pressure regulating tunnel is long in the middle and short on both sides. The pressure regulating system 1D4 is arranged in areas A, B and C, and a double-layer pressure regulating tunnel is arranged (the positions of the double-layer pressure regulating tunnel are staggered vertically). The rest of the structural parts of this embodiment are the same as those of embodiment 1. Example 5

[0149] like Figure 38 and 42 The pressure regulating tunnel is long in the middle and short on both sides. The diameter of the middle section of the pressure regulating tunnel is large and the diameter of the two side sections is small. The pressure regulating system 1D4 is arranged in sections A, B and C. The two side sections are arranged with double-layer pressure regulating tunnels and the middle section is arranged with a single-layer pressure regulating system. The rest of the structural parts of this embodiment are the same as those in embodiment 1. Example 6

[0150] like Figure 29 and 30 The pressure regulating tunnels in areas A and C are both long in the middle and short on both sides. The two ends of the pressure regulating tunnels are stepped expansion areas and stepped necking areas 11c1 and 11c2. The pressure regulating system 1D1 can be arranged in area B. The pressure regulating system 1D4 can be arranged in areas A, B and C. Example 7

[0151] like Figure 31 The pressure regulating tunnel has a long central section and short sides in section A, and equal length in section C. The pressure regulating system 1D1 can be arranged in section B. The pressure regulating system 1D4 can be arranged in sections A, B and C. The rest of the structural parts of this embodiment are the same as those in embodiment 1. Example 8

[0152] like Figure 32 The pressure regulating tunnel has equal lengths in areas A and C. The pressure regulating system 1D1 can be arranged in area B. The pressure regulating system 1D4 can be arranged in areas A, B and C. The rest of the structure in this embodiment is the same as in embodiment 1. Example 9

[0153] like Figure 33 and 34The pressure regulating tunnel A section gradually lengthens from one side to the other, while the C section is of equal length. The pressure regulating system 1D1 can be arranged in the B section. The pressure regulating system 1D4 can be arranged in both the A, B and C sections. The rest of the structural parts of this embodiment are the same as those in embodiment 1. Example 10

[0154] like Figure 35 The pressure regulating tunnel A is short in the middle and long on both sides, while C is of equal length. The pressure regulating system 1D1 can be arranged in B. The pressure regulating system 1D4 can be arranged in both A, B and C. The rest of the structural parts of this embodiment are the same as those in embodiment 1. Example 11

[0155] like Figure 36 The pressure regulating tunnel A section is long in the middle and short on both sides, while C section is long in the middle and long on both sides. The pressure regulating system 1D1 can be arranged in B section. The pressure regulating system 1D4 can be arranged in both A section, B section and C section. The rest of the structural parts of this embodiment are the same as those in embodiment 1.

[0156] While several embodiments and examples of the present invention have been described for those skilled in the art, these embodiments and examples are provided as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, and are included within the scope of the invention as described in the claims and its equivalents.

[0157] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A system for balancing and reducing concentrated stress in overlying coal pillars, characterized in that, The system includes a borehole stress gauge monitoring system and a pressure equalization system. The pressure equalization system includes a pressure-regulating elastic expansion bag (1), a push tube (2), a two-way pressure regulating two-way valve (3), a left-right rotating nut (9a), a positioning ring (4), a push cover (5), a right-angle two-way valve (6), a T-type three-way valve (7), an adjustable pressure T-type three-way valve (77), an adjustable pressure four-way valve (8), an extension tube (9), a left-right rotating nut (9a), and a pressure gauge (10). The pressure-regulating elastic expansion bag (1) has a push tube channel hole (1b) in the middle, and a first liquid / gas bolt interface (1a) is provided on one side of the end of the pressure-regulating elastic expansion bag (1). A second liquid / gas bolt interface (2a) is arranged on the side of the push tube (2). One end of the bidirectional pressure-regulating two-way valve (3) is the push tube interface end (3a) and the pressure-regulating elastic expansion bag interface end (3b). The bidirectional pressure-regulating two-way valve (3) is connected to the second liquid / gas bolt interface (2a) of the push tube (2) through a left-right rotating nut (9a), and the bidirectional pressure-regulating two-way valve (3) is connected to the first liquid / gas bolt interface (1a) of the pressure-regulating elastic expansion bag (1) through a left-right rotating nut (9a). The positioning ring (4) fixes the pressure-regulating elastic expansion bag (1) with the positioning bolt (4d). The maximum diameter of the push cover (5) is greater than the diameter of the pressure-regulating elastic expansion bag (1) in the contracted state. The two ends of the extension tube (9) are left-hand and right-hand threaded interfaces, which can be connected to left-hand and right-hand nuts (9a). The right-angle two-way valve (6) and the T-type three-way valve (7) are respectively connected to the left-hand and right-hand nuts (9a). The pressure gauge (10) is connected to the adjustable pressure four-way valve (8) through the left-hand and right-hand nuts (9a). The borehole stress gauge monitoring system includes a borehole stress gauge (16) and an information receiver (16a). The number of borehole stress gauges (16) is several. Several borehole stress gauges (16) are installed in the lower part of the overlying coal pillar (11) and the underlying rock strata (17) of the overlying coal pillar (11). The information receiver (16a) is used to receive the monitoring information of the borehole stress gauges (16). The push tube (2) is extended by a push tube connecting nut (2c). The push tube connecting nut (2c) is equipped with a two-way regulating valve (2c1). The end of the push tube (2) can be connected to an end sealing bolt (2b). The interior of the two-way pressure regulating two-way valve (3) is a two-way regulating valve (3c). The middle part of the positioning ring (4) is the first push tube channel (4b), and one side of the positioning ring (4) is the first positioning hole (4a). The middle part of the push cover (5) is the second push tube channel (5b), and the side of the push cover (5) is the second positioning hole (5a). One-way regulating valve (77a) is arranged in one end channel of the adjustable pressure T-type three-way valve (77). The adjustable pressure four-way valve (8) is threadedly connected to the pipe wall with an active resistance adjusting bolt (8a). A locking nut (8b) is threadedly connected to the outside of the active resistance adjusting bolt (8a). The adjustable pressure four-way valve (8) is provided with a resistance adjusting rope (8d) and a regulating valve (8c). One end of the resistance adjusting rope (8d) is connected to the active resistance adjusting bolt (8a), and the other end is connected to the regulating valve (8c). The adjustable pressure four-way valve (8) is provided with a pressure relief hole (8e) at the end near the regulating valve (8c).

2. A method of using a system for balancing and reducing concentrated stress in an overlying coal pillar, applied to the system for balancing and reducing concentrated stress in an overlying coal pillar as described in claim 1, characterized in that, The steps are as follows: Install a borehole stress gauge monitoring system; Implement a group of pressure regulating tunnels and install a pressure regulating system; Monitoring and equalization voltage regulation.

3. The method of using the system for balancing and reducing concentrated stress in overlying coal pillars according to claim 2, characterized in that, The steps for installing the borehole stress gauge monitoring system specifically include: The number of borehole stress gauges (16) arranged in the overlying coal pillar (11) is no less than 12, arranged in 4 rows, with no less than 3 in each row. The overlying coal pillar (11) is divided into four areas: the middle area of ​​the coal pillar, the middle area of ​​the coal pillar, the middle area of ​​the coal pillar, the middle area of ​​the coal pillar, the middle area of ​​the coal pillar, the middle area of ​​the coal pillar, and ... the middle area of ​​the coal pillar, and the middle area of ​​the coal pillar, the middle area of ​​the coal pillar The number of borehole stress gauges (16) arranged in the underlying rock stratum area (17) is no less than 20. The position of each borehole stress gauge (16) corresponds one-to-one with the borehole stress gauge (16) arranged in the overlying coal pillar (11) directly above. Furthermore, a row of borehole stress gauges (16) is arranged in the underlying rock stratum area of ​​the overlying coal seam goaf (12) on both sides of each row of borehole stress gauges (16). This is used to realize the full-process and full-area pressure regulation monitoring of the overlying coal pillar (11) and the underlying rock stratum area (17) of the coal pillar in the unmined area, and to adjust the borehole spacing and borehole diameter through monitoring data, and to provide a basis for pressure regulation of the pressure regulating tunnel.

4. The method of using the system for balancing and reducing concentrated stress in an overlying coal pillar according to claim 3, characterized in that, The steps for implementing the pressure regulating tunnel group and installing the pressure regulating system specifically include: Step 1: Using mechanical tunneling equipment, one or more pressure regulating tunnel groups (11c) of a certain length are arranged at certain intervals inside the overlying coal pillar (11) from the main roadway (15) of the overlying coal seam. The pressure regulating tunnel group (11c) includes a pressure regulating tunnel (11cc) in the middle area of ​​the coal pillar, a pressure regulating tunnel (11cy) in the right side area of ​​the coal pillar, and a pressure regulating tunnel (11cz) in the left side area of ​​the coal pillar. The two ends of the pressure regulating tunnel group (11c) are variable diameter sections, and the middle part is a cylindrical section. The variable diameter section is divided into a smooth expansion area, a smooth necking area, a step expansion area, and a step necking area. The pressure regulating tunnel group (11cc) in the middle area of ​​the coal pillar is implemented to realize the early release of coal pillar pressure. Step 2: Connect the push tube (2), push tube connecting nut (2c), pressure regulating elastic expansion bag (1), end sealing bolt (2b), left and right rotating nut (9a), push cover (5), two-way pressure regulating two-way valve (3), and positioning ring (4) into a whole, and push the whole into the cavity of the coal pillar pressure regulating hole (11cc), and inject gas or liquid at a certain pressure; Step 3: Implement the other pressure regulating tunnels in the same manner as Steps 1 and 2; Step 4: The push pipes (2) between each pressure regulating hole are connected into a complete pressure regulating system through a two-way pressure regulating two-way valve (3), a right-angle two-way valve (6), a T-type three-way valve (7), an extension pipe (9), an adjustable pressure four-way valve (8), a left and right turn nut (9a), and a push pipe connecting nut (2c), and a certain pressure of gas or liquid is injected to reach the designed pressure value; Step 5: Through subsequent monitoring, pressure is adjusted by active pressure adjusting bolts (8a), so that the pressure adjusting tunnel gradually deforms and shrinks, the pressure is gradually released evenly, the roof of the coal pillar area gradually sinks, the overburden height of the coal pillar area and the overlying coal seam goaf (12) gradually becomes consistent, the overall stability of the overburden is qualitatively improved, the pressure of the overlying coal pillar (11) in the unmined area is significantly reduced and balanced, and the safe withdrawal of the working face equipment is ensured.

5. The method of using the system for balancing and reducing concentrated stress in an overlying coal pillar according to claim 2, characterized in that, The monitoring and voltage equalization steps specifically include: Step 1: The pre-arranged borehole stress gauge (16) needs to monitor the pressure change in the coal pillar before drilling the pressure regulating tunnel group (11c). All the pressure regulating elastic expansion bags (1) of the pressure regulating tunnel group (11c) are filled with liquid or gas to support the pressure regulating tunnel wall, so that the pressure regulation of the pressure regulating tunnel group (11c) is in a gradual pressure regulation process, and can ensure that the overlying coal pillar (11) will not suddenly become unstable. Step 2: Implement the subsequent pressure regulating tunnel group (11c) and install the pressure regulating elastic expansion bag (1) in sequence. Adjust the parameters of the pressure regulating tunnel group (11c) according to the monitoring results. After the implementation of multiple pressure regulating tunnel groups (11c), if the pressure reduction of the overlying coal pillar (11) is not obvious, it is necessary to further reduce the spacing (m0) of the pressure regulating tunnels and increase the diameter of the pressure regulating tunnels. The length of the pressure regulating elastic expansion bag (1) should be 1-10m, and the diameter after expansion can match the size of the pressure regulating tunnel diameter. The spacing between the pressure regulating elastic expansion bags (1) should be 0-5m. The diameter of the pressure regulating tunnel includes the diameter of the pressure regulating tunnels in the two side areas (d1) and the diameter of the pressure regulating tunnels in the middle area (d0). Step 3: After the pressure regulating system is installed, monitor the data changes of the borehole stress gauge (16) and pressure gauge (10) and the pressure relief status of the pressure regulating system. Gradually reduce the pressure value of the pressure regulating system through the adjustable four-way valve (8) to further balance and reduce the stress concentration of the coal pillar. Step 4: When the working face is mined back to the end mining area until mining stops, the pre-mining dynamic stress will inevitably cause the data of the borehole stress gauge (16) to increase abnormally. The pressure value of the pressure regulating system is gradually reduced by the adjustable pressure four-way valve (8), and then the stress concentration of the coal pillar is further reduced in a balanced manner until all the working face supports are safely withdrawn.

6. The method of using the system for balancing and reducing concentrated stress in an overlying coal pillar according to claim 5, characterized in that, When implementing pressure regulating tunnels in multiple layers, the upper layer pressure regulating tunnel should be implemented first, followed by the lower layer pressure regulating tunnel. The spacing between each layer of pressure regulating tunnels should be 0-3m, and the length difference between each layer of pressure regulating tunnels should be 2-10m. The upper layer pressure regulating tunnel is longer and the lower layer pressure regulating tunnel is shorter, or the upper layer pressure regulating tunnel is shorter and the lower layer pressure regulating tunnel is longer, thus forming an interlayer transition zone.

7. The method of using a system for balancing and reducing concentrated stress in an overlying coal pillar according to claim 6, characterized in that, The spacing (m0) between the pressure regulating tunnels should be 0-5m. The smaller the spacing, the greater the reduction in coal pillar pressure. The diameters (d1) of the pressure regulating tunnels in the two side zones and the diameter (d0) of the pressure regulating tunnel in the middle zone should be 0.3-1.5m. The larger the diameter, the greater the reduction in coal pillar pressure. When the thickness of the overlying coal pillar (11) is <3.5m, only one layer of pressure regulating tunnel group (11c) needs to be implemented. When the thickness of the overlying coal pillar (11) is ≥3.5m and <8m, 1-2 layers of pressure regulating tunnel group (11c) can be implemented. When the thickness of the overlying coal pillar (11) is ≥8m, 2 or more layers of pressure regulating tunnel group (11c) can be implemented. The more layers of pressure regulating tunnel group (11c), the greater the reduction in coal pillar pressure.

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