A method for evaluating and comprehensively preventing and controlling the instability of collapse columns in longwall coal mining faces

Abstract

The present application relates to the field of coal mining technology and provides a method for the instability assessment and comprehensive prevention and control of collapse columns in longwall coal mining working faces. The method is based on different preset instability models to determine the instability of collapse columns of different risk types, and based on the instability determination results of the collapse columns, the instability of collapse columns of different risk types is prevented and controlled. Thus, by analyzing the structural characteristics of the collapse columns, the cementation state of the surrounding rocks, and the stress distribution laws, the possible disaster-causing mechanisms are clarified, and effective targeted instability prevention and control measures are taken, providing a scientific basis and reliable technical support for the prevention and control of mine pressure disasters, and ensuring the safe production of the working face.

Description

Technical Field

[0001] The present application relates to the field of coal mining technology, and in particular to a method for evaluating and comprehensively preventing and controlling the instability of collapse columns in longwall coal mining working faces. Background Art

[0002] In some mining areas, large subsidence columns develop from the surface into the coal seam, exerting a significant traction on the surrounding substructure. When a longwall face pushes through a subsidence column, it is sometimes necessary to directly cut and mine the large subsidence column to reduce the frequency of face relocation and improve face production efficiency. However, this can pose serious safety risks.

[0003] When the column is highly cemented, it may slide entirely due to its own weight during mining, or rotate and tilt entirely due to the clamping force of the overburden. When cracks develop within the column or large, interconnected structural surfaces exist, mining and the resulting mining stresses may cause partial sliding or shearing of the column. Whether the column slides entirely due to its own weight, rotates and tilts entirely due to the clamping force of the overburden, or slides or shears partially due to mining stress, these can all lead to mine pressure problems, such as the collapse of working face supports and roof falls near the column, seriously threatening working face safety.

[0004] Therefore, there is an urgent need to provide a technical solution to the above-mentioned deficiencies in the existing technology. Summary of the Invention

[0005] The purpose of this application is to provide a method for assessing and comprehensively preventing and controlling the instability of collapse columns in longwall coal mining working faces, so as to solve or alleviate the problems existing in the above-mentioned prior art.

[0006] In order to achieve the above objectives, this application provides the following technical solutions:

[0007] The present application provides a method for instability assessment and comprehensive prevention and control of collapse columns in longwall coal mining working faces, comprising: step S101, based on different preset instability models, performing instability judgment on collapse columns of different risk types; step S102, based on the instability judgment results of the collapse columns, performing instability prevention and control on the collapse columns of different risk types.

[0008] Preferably, in step S101, according to the instability model:

[0009] ρgV>2cH(L H +L h )+2μH(σ h ·L h +σ H ·L H )

[0010] The overall sliding instability after activation of the complete collapse column is determined; where ρ is the rock density of the collapse column, g is the acceleration of gravity, V is the volume of the collapse column, c is the cohesion of the contact surface between the collapse column and the rock mass, H is the height of the collapse column above the coal seam level, L H is the vertical direction of the collapse column to the maximum horizontal principal stress σ H Axis length, L h The collapse column is perpendicular to the minimum horizontal principal stress σ h is the axial length of the column, and μ is the friction coefficient of the contact surface between the collapse column and the rock mass.

[0011] Preferably, in step S101, according to the instability model:

[0012] ρgV>∫ A (2c·dA+2μσ·dA)

[0013] The instability of the collapse column with a continuous main weak surface is judged; where ρ is the rock density of the collapse column, g is the acceleration of gravity, V is the volume of the collapse column, c is the cohesion of the contact surface between the collapse column and the rock mass, μ is the friction coefficient of the contact surface between the collapse column and the rock mass, A is the contact area of ​​the contact surface between the collapse column and the rock mass, and σ is the compressive normal stress on the collapse column.

[0014] Preferably, in step S101, according to the instability model:

[0015]

[0016] The instability risk of the rotating pressure frame of the collapse column is determined; where F max is the maximum support force of the hydraulic support corresponding to the collapse column; ρ is the rock density of the collapse column, g is the acceleration of gravity, V is the volume of the collapse column, L h L is the axial length of the collapse column perpendicular to the minimum horizontal principal stress, 支 is the distance between the hydraulic support and the coal wall of the working face, θ is the overburden rotation angle of the working face, E i is the elastic modulus of the overlying rock layer i, h i is the thickness of the overlying rock layer i.

[0017] Preferably, in step S102, in response to the overall sliding or angular rotation of the collapse column, blasting is performed in the goaf behind the collapse column to increase the volume of falling gangue and the expansion coefficient, and / or belt filling is performed under the collapse column to support the collapse column.

[0018] Preferably, in step S102, the blasting of the goaf behind the collapse column increases the volume of the gangue falling and the expansion coefficient, including: arranging deep hole drillings in a grid pattern in the goaf behind the collapse column, loading explosives in the deep hole drillings and detonating them in batches to induce the roof rock layer to fall; and regulating the blasting parameters so that the expansion coefficient of the falling gangue is controlled to be above 1.2, so that the falling gangue fills the pores of the goaf.

[0019] Preferably, in step S102, strip filling is performed below the collapse column to support the collapse column, including: arranging a pair of strip-type cement walls in the goaf below the collapse column, and filling the area between the cement wall pairs with waste gangue generated during the coal mining process, and the filling process is carried out synchronously with the advancement of the coal mining working face to form a strip-shaped continuous support body; wherein the expansion coefficient of the waste gangue is above 1.2.

[0020] Preferably, in response to The strip width is 10 meters; in response to The strip width is 15 to 20 meters; The strip width is 30 meters; in response to The strip width is 50 meters.

[0021] Beneficial effects:

[0022] In the method for assessing and comprehensively preventing and controlling the instability of collapsed columns in longwall coal mining working faces provided in the embodiments of the present application, instability determinations are made for collapsed columns of different risk types based on different preset instability models, and instability prevention and control measures are implemented for collapsed columns of different risk types based on the instability determination results of the collapsed columns. Thus, by analyzing the structural characteristics of the collapsed columns, the cementation state of the surrounding rocks, and the stress distribution patterns, the possible disaster-causing mechanisms are clarified, and effective targeted instability prevention and control measures are taken, providing a scientific basis and reliable technical support for preventing and controlling mine pressure disasters, thereby ensuring safe production at the working face. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings in the specification, which constitute a part of this application, are used to provide further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute improper limitations on this application.

[0024] in:

[0025] Figure 1 A schematic flow chart of a method for assessing and comprehensively preventing and controlling collapse columns in a longwall coal mining face according to some embodiments of the present application;

[0026] Figure 2 A schematic diagram of the column rotation when the working surface passes through the collapse column according to some embodiments of the present application;

[0027] Figure 3 Schematic diagram of the displacement of the contact point of the overlying i-th rock layer when the collapse column rotates according to some embodiments of the present application. DETAILED DESCRIPTION

[0028] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments. Each example is provided by way of explanation of the present application and does not limit the present application. In fact, it will be clear to those skilled in the art that modifications and variations can be made in the present application without departing from the scope or spirit of the present application. For example, a feature shown or described as part of one embodiment can be used in another embodiment to produce yet another embodiment. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention should fall within the scope of protection of the embodiments of the present invention.

[0029] When the longwall working face pushes mining through the collapse column, it is necessary to comprehensively assess the risks of collapse column rock sliding, local cutting, etc., and propose scientific control plans. Based on this, the embodiment of the present application proposes a method for instability assessment and comprehensive prevention and control of collapse columns in longwall coal mining working faces. By analyzing the structural characteristics of the collapse column, the cementation state of the surrounding rock and the stress distribution law, the possible disaster-causing mechanism is clarified, which can provide a scientific basis and reliable technical support for the prevention and control of mine pressure disasters and ensure the safe production of the working face.

[0030] like Figures 1 to 3 As shown in the figure, the instability assessment and comprehensive prevention and control methods of the longwall mining face collapse column include:

[0031] Step S101: Based on different preset instability models, instability determination is performed on collapse columns of different risk types.

[0032] When a longwall coal mining face is about to complete the cutting of a sinkhole column, there is almost no support at the bottom of the column except for the support force of the supports (hydraulic supports). Whether the sinkhole column loses its stability depends on the cohesion and friction at the contact surface between its own weight and the surrounding rock mass. At this time, the sinkhole column often slides. In other words, when the weight of the sinkhole column is greater than the combined force of the cohesion and friction at the contact surface (composed of the influence of contact surface friction, cohesion and principal stress), the sinkhole column will slide or become unstable.

[0033] Therefore, for a well-cemented collapse column (the degree of cementation of the collapse column is determined by coring the collapse column through geological drilling), after activation (the stable state is destroyed), the instability model is as follows:

[0034] ρgV>2cH(L H +L h )+2μH(σ h ·L h +σ H ·L H )

[0035] Determine whether a complete collapse column has the risk of overall sliding instability. Where, ρ is the rock density of the collapse column, which can be measured in the laboratory after dispersed sampling on site; g is the acceleration of gravity; V is the volume of the collapse column, which can be determined by calculating the geometric shape of the collapse column after on-site geological drilling; c is the cohesion of the contact surface between the collapse column and the rock mass, which can be determined by taking a combined sample of the collapse column and the adjacent rock layer on site and conducting a direct shear test; H is the height of the collapse column above the coal seam level; L H is the vertical direction of the collapse column to the maximum horizontal principal stress σ H Axis length, L h is the vertical direction of the collapse column to the minimum horizontal principal stress σ h The axis length of the column, μ is the friction coefficient of the contact surface between the collapse column and the rock mass, which can be determined by taking a combined sample of the collapse column and the adjacent rock layer on site and conducting a direct shear test; the maximum horizontal principal stress σ H , minimum horizontal principal stress σ h It can be determined through in-situ ground stress testing.

[0036] The collapse column is composed of rock mass with many tiny cracks inside. When there is a main weak plane in the collapse column (the tiny cracks in the collapse column are connected to form a plane that runs through the entire collapse column), the instability risk of the collapse column becomes more complex and variable, especially when the geometric dimensions of the oblique cylinder, the occurrence of the weak plane and the direction of the principal stress are involved. After calculating the cohesion and friction between the collapse column and the contact surface and making corrections, according to the instability model:

[0037] ρgV>∫ A (2c·dA+2μσ·dA)

[0038] The instability of a collapsed column with a continuous main weak surface is determined. Here, ρ is the rock density of the collapsed column, g is the acceleration of gravity, V is the volume of the collapsed column, c is the cohesion between the collapsed column and the rock mass, μ is the friction coefficient between the collapsed column and the rock mass, A is the contact area between the collapsed column and the rock mass, and σ is the compressive normal stress on the collapsed column.

[0039] In longwall coal mining faces, especially when the working face approaches a sinkhole column, the rotation effect of the overburden can cause the sinkhole column to rotate under the clamping force of the overburden. This can lead to increased pressure on the hydraulic supports caused by the sinkhole column rotation, which can lead to a risk of support collapse. This application assesses the risk of support collapse caused by sinkhole column rotation based on the support (hydraulic support) pressure generated by the support (hydraulic support) and the maximum support capacity of the support (hydraulic support).

[0040] Because the tensile strength of the rock is very low, and the tensile strength of the cementation surface is less than that of the rock, the collapse column rotates under the action of mining at the working face. The rotation angle θ caused by mining at the working face causes the cementation surface between the collapse column and the overburden in front of the frame (hydraulic support) to open into a crack due to tension, thus removing the force from the front contact surface. Although the collapse column and the overburden behind the frame (hydraulic support) slide slightly, they still maintain contact, indicating that the contact surface has a strong effect.

[0041] The magnitude of the overburden rotation angle θ of the working face is related to multiple factors, including the mining face parameters: the working face mining height h, the width of the collapse column in the working face advancement direction, that is, the axial length L of the collapse column perpendicular to the minimum horizontal principal stress h , height of the caving zone in the goaf h m , rock expansion coefficient, etc. Specifically, after the overburden of the working face is rotated, according to the formula:

[0042]

[0043] Determine the overburden rotation angle θ of the working face.

[0044] The collapsed column after rotation (rotation angle θ) is under the support force F 支 , Coal body support force before the frame (F 煤x 、F 煤y ) and gravity, the working face maintains a state of equilibrium until the working face is cut again and causes the collapse column to rotate further. The most dangerous state is when the working face is about to cut all the collapse columns. Here, the force of the overlying rock layer i on the collapse column is defined as F 空i , the thickness of the overlying rock layer i is h i , the elastic modulus of the overlying rock layer i is E i , the distance between the hydraulic support and the coal wall of the working face is L 支 , and the collapse column is analyzed, and the displacement Δs generated by the contact point between the collapse column and the overlying rock layer i is i for:

[0045]

[0046] but:

[0047]

[0048] Furthermore, there are:

[0049] F 支 ·L 支 +∑F 空i ·(∑h i -L h sinθ)=ρgV·(L h -L 支 )cosθ

[0050] Constructed based on the support force F 支 Maximum support force F of the bracket max The instability model:

[0051]

[0052] The risk of the rotating support frame of the collapsed column is judged to be unstable. max is the maximum support force of the hydraulic support corresponding to the collapse column; ρ is the rock density of the collapse column, g is the acceleration of gravity, V is the volume of the collapse column, L h L is the length of the axis of the collapse column perpendicular to the minimum horizontal principal stress, 支 is the distance between the hydraulic support and the coal wall of the working face, θ is the overburden rotation angle of the working face, E i is the elastic modulus of the overlying rock layer i, h i is the thickness of the overlying rock layer i.

[0053] When F max / F 支 <1, that is, the maximum support force of the hydraulic support corresponding to the collapse column is less than the support support force F 支 When F max / F 支 >1, that is, the maximum support force of the hydraulic support corresponding to the collapse column is greater than the support support force F 支 When the hydraulic support is used, it can successfully cut and push through the collapsed column.

[0054] Step S102: Based on the instability determination result of the collapsed column, instability prevention and control are performed on collapsed columns of different risk types.

[0055] After the well-bonded collapse column becomes unstable due to activation, the entire collapse column moves (slides as a whole); the collapse column containing a penetrating weak surface is divided into an upper part and a lower part by the penetrating weak surface. After the collapse column becomes unstable, the upper part or the lower part of the collapse column moves and rotates, which may lead to the risk of frame crushing. Regardless of whether the collapse column slides as a whole or rotates at an angle, in this application, preventive measures are taken to increase the supporting effect of the overlying rock in the goaf on the collapse column, and a new support body is constructed under the collapse column to support the collapse column. In other words, the goaf behind the collapse column is blasted to increase the volume of gangue falling and the coefficient of crushing expansion, and / or, belt filling is performed under the collapse column to support the collapse column. Furthermore, by blasting the goaf behind the collapse column to increase the volume of gangue falling and the coefficient of crushing expansion, the supporting effect of the falling gangue on the overlying rock strata is improved, thereby increasing the supporting effect of the overlying rock on the collapse column; the collapse column is supported by belt filling under the collapse column.

[0056] In a specific application scenario, when deep hole blasting is carried out in the goaf to induce rock fall, deep holes are drilled in a grid pattern in the goaf behind the collapse column, and explosives are loaded in the deep holes and detonated in batches to induce the roof rock layer to fall. That is, deep holes are drilled in the goaf behind the collapse column, with a spacing of 6 to 8 meters and a hole depth of 5 to 10 meters, and are distributed in a grid pattern. Then, low-impact, high-fragmentation explosives (such as emulsion explosives) are loaded in the deep holes and detonated in batches to induce the roof rock layer to fall. During blasting, the blasting block size is qualitatively controlled by adjusting the blasting parameters so that the expansion coefficient of the falling waste rock is controlled to be above 1.2 (preferably 1.2 to 1.3), so that the falling waste rock can fully fill the pores of the goaf.

[0057] In another specific application scenario, when strip filling is performed under the collapse column to support the collapse column, a pair of strip cement walls are arranged in the goaf below the collapse column. The width of the wall pair is 10 meters, the thickness is 1 meter, and the interval between the wall pairs is 30 meters. The wall material is ordinary cement mortar (mixed with fly ash or slag to reduce costs and enhance strength). Among them, the cement wall construction is completed by drilling grouting or formwork casting. The height of each pair of cement walls must be flush with the top of the goaf to form a rigid support

[0058] The area between the cement walls is filled with waste gangue generated during the coal mining process, and the gangue filling process adopts layered filling and compaction. The crushing coefficient of the waste gangue is above 1.2 (preferably 1.2-1.3), and the filling process is carried out synchronously with the advancement of the coal mining working face to form a strip-shaped continuous support body, which effectively avoids the problem of insufficient support caused by filling delay.

[0059] In the embodiment of the present application, the width of the filling strip (strip-shaped continuous support body) is dynamically adjusted according to the risk of the rotation pressure frame of the collapse column. <F max / F 支 <1.0, the strip width is 10 meters; when 0.5 <F max / F 支 When ≤0.8, the strip width gradually increases within the range of 15 to 20 meters; when 0.3 <F max / F 支 When ≤0.5, the strip width is 30 meters; when F max / F 支 When the pressure is ≤0.3, the strip width is 50 meters. At the same time, stress sensors and displacement monitoring devices are placed in the strip filling area to monitor the stress and support status of the collapsed column in real time. Based on the monitoring data, the strip filling process and filling materials are dynamically adjusted to effectively ensure the stability of the support system.

[0060] Therefore, through the analysis of the structural characteristics of the collapse column, the bonding state of the surrounding rock and the stress distribution law, the possible disaster-causing mechanism is clarified, and through deep-hole blasting in the goaf to induce caving, strip-type cement wall filling, gangue filling, and monitoring and feedback of stress sensors and displacement monitoring devices, the collapse column is prevented from becoming unstable, providing a scientific basis and reliable technical support for the prevention and control of mine pressure disasters, and ensuring safe production on the working face.

[0061] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0062] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0063] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0064] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0065] In the present invention, the terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0066] The foregoing description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are readily apparent to those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for assessing and comprehensively preventing and controlling the instability of a longwall coal mining face collapse column, characterized in that: include: Step S101: Based on different preset instability models, perform instability determination on collapsed columns of different risk types; wherein, according to the instability model: ； Determine the overall sliding instability after activation of the complete collapsed column; where, is the rock mass density of the collapse column, is the acceleration due to gravity, is the volume of the collapse column, is the cohesion between the contact surface of the collapse column and the rock mass, is the height of the collapse column above the coal seam level, The collapse column is perpendicular to the maximum horizontal principal stress The axis length, The collapse column is perpendicular to the minimum horizontal principal stress The axis length, is the friction coefficient of the contact surface between the collapse column and the rock mass; According to the instability model: ； The instability of the collapsed column with a continuous main weak surface is determined; where, is the contact area between the collapse column and the rock mass, is the compressive normal stress of the collapsed column; According to the instability model: ； The risk of the rotary pressure frame of the collapse column is judged to be unstable; where, is the maximum supporting force of the hydraulic support corresponding to the collapse column; is the distance between the hydraulic support and the coal wall of the working face, is the overburden rotation angle of the working face, For the above The elastic modulus of the rock layer, For the above the thickness of the rock layers; Step S102: Based on the instability determination result of the collapsed column, instability prevention and control are performed on the collapsed columns of different risk types.

2. The method for assessing and comprehensively preventing and controlling the instability of a longwall coal mining face collapse column according to claim 1 is characterized in that: In step S102, In response to the overall sliding or angular rotation of the collapse column, blasting is performed in the goaf behind the collapse column to increase the volume of falling waste rock and the expansion coefficient, and / or belt filling is performed under the collapse column to support the collapse column.

3. The method for assessing and comprehensively preventing and controlling the instability of a longwall coal mining face collapse column according to claim 2, characterized in that: In step S102, the blasting of the goaf behind the collapse column to increase the volume of the gangue falling and the expansion coefficient includes: Arranging deep holes in a grid pattern in the goaf behind the collapse column, loading explosives into the deep holes and detonating them in batches to induce the roof rock layer to fall; The blasting parameters are adjusted so that the expansion coefficient of the falling gangue is controlled to be above 1.2, so that the falling gangue can fill the pores in the goaf.

4. The method for assessing and comprehensively preventing and controlling the instability of a longwall coal mining face collapse column according to claim 2, wherein: In step S102, the belt filling is performed below the collapse column to support the collapse column, including: A pair of strip-type cement walls are arranged in the goaf below the collapse column, and the area between the cement walls is filled with waste gangue generated during the coal mining process, and the filling process is carried out synchronously with the advancement of the coal mining working face to form a strip-shaped continuous support body; wherein the expansion coefficient of the waste gangue is above 1.

2.

5. The method for assessing and comprehensively preventing and controlling the instability of a longwall coal mining face collapse column according to claim 4, characterized in that: In response to , the strip width is 10 meters; In response to , the strip width is 15~20 meters; In response to , the strip width is 30 meters; In response to , the strip width is 50 meters.

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