Caving method for realizing jump back of mining pressure peak point of working face end

Abstract

The present application relates to the field of coal mining, especially to a roof cutting and pressure releasing method for realizing the jump of the peak point of the mining pressure of the working face in the end of mining to the retreat channel. In combination with the problems of the existing technology, such as the experience of the roof cutting parameters, the passivity of the bearing and support of the retreat channel, etc., the present application proposes to realize the jump of the peak point of the mining pressure to the retreat channel and the active support technology by using the roof cutting and pressure releasing technology. Different from the existing roof cutting and pressure releasing technology which surrounds the target rock stratum and establishes the length and angle parameters of the roof cutting according to experience, the present application proposes to determine the depth and angle of the roof cutting through the jump range according to the discovery of the jump of the peak point of the mining pressure after the roof cutting. On this basis, the present application establishes the overall mathematical model of the roof cutting parameters, the size of the retreat channel, the stress and state of the surrounding rock, and the support requirements of the retreat channel, thereby providing scientific and active basis for the roof cutting and the support of the retreat channel.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coal mining, in particular to a roof cutting and pressure releasing method for realizing the jump of a peak point of rock pressure in a retreat passage at the end of mining in a working face. BACKGROUND

[0002] In underground mining, there is a stop line and a retreat passage in front of a longwall working face during the mining process. When the working face enters the end of mining stage, the peak value of the support stress in front of the working face, i.e. the peak point of rock pressure, gradually approaches the side of the retreat passage. There is also a fixed peak point of rock pressure around the retreat passage. As the distance between the two peak points decreases, the two peak points superimpose, couple and converge on the side of the retreat passage. Under the action of superimposed stress, the coal pillar between the working face and the retreat passage gradually loses stability and is damaged under high stress, and even suddenly collapses, thereby affecting the stability of the surrounding rock of the retreat passage. Therefore, common measures for the end of mining include reducing the mining height, controlling the speed, hanging ropes and nets, strengthening the support of the roadway and cutting the roof, etc. The purpose is to ultimately realize the smooth connection of the working face and the retreat passage, and the core content is to protect the stability of the retreat passage to ensure the safe retreat of the equipment.

[0003] In the specific end of mining process, reducing the mining height and controlling the speed are actually to control the movement of overburden rock, thereby avoiding the sudden damage of the coal pillar in front of the working face, and protecting the stability of the surrounding rock of the retreat passage. The hanging rope and net process mainly plays an auxiliary role, i.e. the sudden collapse of the roof caused by the instability of the coal pillar and the roof of the retreat passage, and is not the main technical measure for the end of mining.

[0004] Strengthening the support of the roadway in the end of mining stage is a common method, which mainly passively and negatively increases the support resistance to ensure the stability of the surrounding rock. In fact, it has been proved that this passive increase of resistance to adapt to the movement and load of overburden rock has limited effect, high economic cost and low efficiency. Therefore, in recent years, the control of rock pressure has formed a roadway control concept mainly based on "releasing" and "yielding". As for "yielding", the adjustment of the working face speed is a common means, i.e. avoiding the influence of rock pressure. This method is mainly suitable for the arrangement of the working face support and the connection of the adjacent roadway of the working face during the mining of the working face, and has limited effect on the retreat passage in front of the working face in the advancing direction.

[0005] "Releasing pressure" is a more favorable active pressure control means. For example, when the working face advances for a long distance and the roof has not collapsed, the hard and difficult-to-collapse roof can be forced to fall, thereby avoiding the instantaneous collapse of the large area roof of the working face and the resulting dynamic disaster. In addition, in order to avoid the large load of the adjacent roadway of the working face during the connection of the working face, the recovery roadway can be arranged below the goaf or the roof can be cut to release the pressure. These are the existing pressure releasing methods.

[0006] But in the pressure relief scheme and parameters, especially the design process of the length and angle of pressure relief borehole, the current relies on engineering experience, such as when the pressure relief of the difficult-to-collapse roof is considered, the length and angle of pressure relief are matched to make the pressure relief borehole hit the target rock layer; when the pressure relief roadway is considered, the thickness of the collapsed rock layer is used to form a roadway support by using its crushing expansion, and the length and angle of pressure relief are also given more subjectively to ensure that the cutting height meets the production requirements.

[0007] The same problem exists in the top cutting pressure relief at the end of the working face, and when designing the top cutting scheme and parameters, we pay more attention to hitting the key rock layer with the top cutting borehole, thereby cutting off the mechanical connection between the key rock layer and the rock layer above the front withdrawal channel, so as to ensure that the withdrawal channel is in a state of low bearing and favorable support of the surrounding rock.

[0008] In fact, if the top cutting method can be used to block the mechanical connection to adjust the stress and stability of the surrounding rock of the withdrawal channel, and then give the basic basis for roadway support, even give the geometric size of the roadway in advance, the top cutting scheme and parameters formed are undoubtedly more scientific. SUMMARY

[0009] In view of the above technical problems, the purpose of the present application is to provide a top cutting pressure relief method for realizing the jump of the peak point of mine pressure to the withdrawal channel at the end of the working face, so as to solve the problems of passive support of the withdrawal channel, dependence on experience of the top cutting scheme and parameters, etc.

[0010] To achieve the above purpose, the present application adopts the following technical scheme:

[0011] The top cutting pressure relief method for realizing the jump of the peak point of mine pressure to the withdrawal channel at the end of the working face comprises the following processes:

[0012] a. Before the working face at the end of the mining penetrates the withdrawal channel, the top cutting technology is used to realize the jump of the peak point of mine pressure from the side of the withdrawal channel close to the working face to the solid coal on the other side of the withdrawal channel, and the method for giving the basis for roadway support parameters is provided;

[0013] b. During the mining, the advanced moving peak of mine pressure is formed in front of the working face, and according to the size of the moving peak and the distance between the working face, the technical measures of adjusting the mining height and the mining speed during the end of the mining are used to control the mine pressure, and the jump of the peak to the other side of the withdrawal channel is predicted;

[0014] c. According to the bearing and damage characteristics of the surrounding rock of the withdrawal channel, the distance between the fixed peak point formed by the withdrawal channel and the withdrawal channel is determined;

[0015] d. The peak point of the mobile mine pressure of the working face gradually approaches and couples with the fixed peak point on one side of the withdrawal channel, and the final superimposed peak point is formed at the position of the fixed peak point on one side of the withdrawal channel. In the gradually approaching process, the change of the stress peak value is focused on, the stability of the coal pillar between the peak point and the withdrawal channel is analyzed, and the roof at the position of the final superimposed peak point is artificially cut to realize that the peak value directly jumps from the side of the withdrawal channel close to the working face to the other side, so that the roof of the withdrawal channel avoids the mine pressure peak value.

[0016] e. The height and angle of the cutting roof are determined by considering the roof crushing coefficient, the superimposed peak point position on the side of the working face of the withdrawal channel, the position of jumping to the other side of the withdrawal channel, the roadway geometric size and the support resistance requirement.

[0017] According to the method, preferably, the cutting roof pressure relief method for realizing the jumping of the mine pressure peak point of the working face to the withdrawal channel at the end of mining is suitable.

[0018] Specifically, in step a, at the end of mining of the working face, the cutting roof technology is used to realize the method that the mine pressure peak point on the side of the withdrawal channel close to the working face directly jumps to the other side, and the basic support parameter design basis of the roadway is given.

[0019] In step b, during the mining of the working face, the superimposed peak value of the mobile mine pressure is formed in front, the peak point moves forward, and the distance of the moving peak point ahead of the working face is determined.

[0020]

[0021] In the formula: is the working face superimposed mine pressure peak point and its distance; is the mining height, the mining height before the working face enters the through stage of the end of mining is the same as the height of the withdrawal channel ; is the friction factor; is the triaxial stress coefficient, ; is the shear strength; is the cohesion; is the internal friction angle.

[0022] This part of the theoretical basis has two effects. First, when the position of the point approaches the fixed mine pressure peak point of the withdrawal channel, it enters the end of mining stage, at this time, the comprehensive end of mining technology needs to be considered, such as reducing the mining height, controlling the speed, etc. Second, when the working face enters the superimposed peak point of the surrounding rock of the withdrawal channel, the cutting height needs to be further determined by using this basis, so as to calculate the jumping distance of the mine pressure peak point after cutting.

[0023] In step c, according to the bearing and failure characteristics of the surrounding rock of the retreat channel, the fixed peak point formed by the retreat channel and the distance between the retreat channel are determined:

[0024]

[0025] In the formula: The fixed peak point on one side of the retreat channel and the distance therefrom; The height of the retreat channel; The stress concentration coefficient; The overburden density; The buried depth; The support resistance of the retreat channel.

[0026] In step d, the moving peak point of the working face and the fixed peak point on one side of the retreat channel gradually approach and couple, and the final superimposed peak point is formed at the position of the fixed peak point on one side of the retreat channel. In the process of gradually approaching, the change of the stress peak value is focused on, the stability of the coal pillar between the peak point and the retreat channel is analyzed, and technical solutions such as reinforcement support and net hanging on the coal pillar side of the retreat channel are timely taken to determine the artificial roof cutting at the position of the final superimposed peak point, so as to realize the direct jumping of the peak value from the side of the retreat channel close to the working face to the other side, and to realize the retreat channel roof avoiding the mine pressure peak value.

[0027] In step e, considering the roof crushing coefficient, the superimposed peak point position on the working face side of the retreat channel, the position of jumping to the other side of the retreat channel, the roadway geometric size and the support resistance requirement, the height and angle of the cutting roof are determined.

[0028] According to the roof crushing coefficient, the final mining height M or the roadway height h, the cutting height of the rock stratum can be determined to fall down, which satisfies:

[0029]

[0030] In the formula: The cutting height; The roof rock crushing coefficient.

[0031] Considering the condition of ensuring the cutting height, according to a certain angle, it can be deep into the superimposed mine pressure peak point position, which satisfies:

[0032]

[0033] In the formula: The cutting angle.

[0034] Considering the jumping to the other side of the retreat channel position, the cutting height L and the roadway height h form a new superimposed mine pressure peak value, and its position needs to satisfy:

[0035]

[0036] In the formula: The new peak pressure point at the advanced cutting position; , the width of the alleyway.

[0037] Based on the three constraints, the final cutting height is determined. ,angle tunnel geometry The distance between the peak point jump to the other side of the retreat channel, controlled by several human technical factors, and the basic support resistance of the roadway. The relationship between them satisfies:

[0038]

[0039] Using the three limiting conditions in step e, the first condition ensures that the mining area provides sufficient space for the roof to move, and that the roof loses its mechanical connection as much as possible after being cut off; the second condition ensures that the pressure relief borehole is drilled to the peak point of the mine pressure to achieve the most favorable roof cutting effect; the third condition ensures that the peak point of the mine pressure jumps directly to the other side of the retreat channel after the roof is cut off, ensuring that the retreat channel avoids the influence of high stress.

[0040] By combining these three conditions, the relationship between the cutting length, height, and angle was finally established, thus providing a scientific basis for cutting the top; secondly, among the derived conditions for cutting the top, there exists a... In other words, the requirements for the support resistance of the retreat channel are coupled with the above-mentioned roof cutting requirements, and the relationship between roof cutting parameters, stress distribution and surrounding rock condition, and roadway geometry and support requirements is actually established.

[0041] The method for determining the roof cutting and pressure relief and channel support for realizing the jump retreat channel at the peak point of the mining pressure at the end of the working face, provided by the present invention, has the following advantages:

[0042] (1) A method for artificially intervening and transferring the stress in the surrounding rock of the final withdrawal channel by cutting the top is proposed.

[0043] (2) A scientific method for top cutting scheme and parameters was proposed, which avoids the problems of empirical top cutting scheme and parameters and passive support of retreat channel that exist in existing methods.

[0044] (3) The coupling relationship between the cutting parameters, roadway geometry and surrounding rock stress, state, and retreat channel support scheme and parameters was established, forming a complete system that can provide scientific basis for mine design and production. Attached Figure Description

[0045] Figure 1 The relationship between the peak point of the final mining pressure, convergence, and the transfer of shear stress is given. Detailed Implementation

[0046] The specific embodiments of the present application are described in conjunction with the accompanying drawings.

[0047] In the present embodiment, in the first step, during the working face mining, the advanced moving rock pressure peak value is formed in front , and the peak point moves forward and changes gradually to form , so it is necessary to determine the distance of the moving peak point from the working face :

[0048]

[0049] In the formula: , the working face is ahead of the rock pressure peak point and its distance; , the mining height, the mining height before the working face enters the final mining through stage and the height of the withdrawal channel are the same; , the friction factor; , the triaxial stress coefficient, ; , the shear strength; , the cohesion; , the internal friction angle.

[0050] In the second step, according to the bearing and damage characteristics of the surrounding rock of the withdrawal channel, the fixed peak point of the withdrawal channel is determined and the distance between the withdrawal channel :

[0051]

[0052] In the formula: , the fixed rock pressure peak point on one side of the withdrawal channel and its distance; , the height of the withdrawal channel; , the stress concentration coefficient; , the overburden density; , the buried depth; , the support resistance of the withdrawal channel.

[0053] In the third step, the moving rock pressure peak point of the working face and the fixed peak point on one side of the withdrawal channel gradually approach, couple, and form the final superimposed peak point at the position of the fixed peak point on one side of the withdrawal channel , in the gradual approaching process, the change of the stress peak value is focused on, the stability of the coal pillar between the peak point and the withdrawal channel is analyzed, and technical solutions such as reinforcement support, net hanging, etc. on the coal pillar side of the withdrawal channel are timely taken to determine the artificial roof cutting on the position of the final superimposed peak point, so that the peak value jumps directly from the side of the working face to the other side to realize the roof of the withdrawal channel avoiding the rock pressure peak value.

[0054] The fourth step is to determine the height and angle of the roof cutting, taking into account the roof expansion coefficient, the location of the superimposed peak point on the working face side of the retreat channel, the location of the jump to the other side of the retreat channel, the roadway geometry and support resistance requirements.

[0055] The roof cutting height is determined based on the roof rupture coefficient, the final mining height M, or the roadway height h, ensuring that the rock strata can fall down and satisfy the following conditions:

[0056]

[0057] In the formula: Cutting height; , coefficient of fragmentation of the top strata.

[0058] Considering the requirement of ensuring the cutting height, and at a certain angle, reaching the peak point of the superimposed mine pressure, the following conditions must be met:

[0059]

[0060] In the formula: , the angle of the cut top.

[0061] Considering jumping to the other side of the retreat channel, the top cutting height L and the roadway height h combine to form a new peak of advanced mine pressure. Its location must satisfy the following conditions:

[0062]

[0063] In the formula: The new peak pressure point at the advanced cutting position; , the width of the alleyway.

[0064] Based on the three constraints, the final cutting height is determined. ,angle tunnel geometry The distance between the peak point jump to the other side of the retreat channel, controlled by several human technical factors, and the basic support resistance of the roadway. The relationship between them satisfies:

[0065]

[0066] Using the three limiting conditions in step four, the first condition ensures that the mining area provides sufficient space for roof movement, and that the roof loses its mechanical connection as much as possible after being cut away; the second condition ensures that the pressure relief borehole is drilled to the peak point of the mining pressure. To achieve the most favorable roof cutting effect; the third condition ensures the peak point of the mine pressure after roof cutting. Jump directly to the other side of the retreat channel to ensure that the retreat channel is spared the effects of high stress.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for roof cutting and depressurization to achieve a jump-back channel at the peak point of the final mining pressure in the working face, characterized in that, The process includes the following: a. Before the working face is connected to the retreat passage, use the top cutting technology to make the peak point of the mine pressure jump from the side of the retreat passage close to the working face to the solid coal on the other side of the retreat passage, and give the basis for the roadway support parameters. b. During the mining period, a peak of moving ore pressure is formed in front of the working face. Based on the size of the moving peak and the distance between it and the working face, technical measures such as adjusting the mining height and mining speed during the final mining period are used to control the ore pressure, and to predict when the peak will jump to the other side of the retreat channel. c. Determine the distance between the fixed peak point of the retreat channel and the retreat channel based on the bearing capacity and failure characteristics of the surrounding rock of the retreat channel; d. The moving peak point of the mining pressure during the working face mining gradually approaches and couples with the fixed peak point on one side of the retreat channel, and forms the final superimposed peak point at the fixed peak point position on one side of the retreat channel. During the gradual approach, we focus on the change of the stress peak, analyze the stability of the coal pillar between the peak point and the retreat channel, and determine to manually cut the roof at the position of the final superimposed peak point so that the peak can jump directly from the side of the retreat channel close to the working face to the other side, so that the roof of the retreat channel can avoid the peak of the mining pressure. e. Considering the roof expansion coefficient, the location of the superimposed peak point on the working face side of the retreat channel, the location of jumping to the other side of the retreat channel, the roadway geometry and support resistance requirements, determine the height and angle of roof cutting; Based on the roof expansion coefficient and the final mining height or tunnel height To ensure the rock strata at the cut-off height can fall down, the following conditions must be met: In the formula: Cutting height; The coefficient of fragmentation of the top strata; Considering the requirement of ensuring the cutting height, and at a certain angle, it is possible to penetrate to the location of the peak point of the superimposed mine pressure, satisfying the following: During the ceremony: , cutting angle; Considering jumping to the other side of the retreat channel, the top cutting height L and the roadway height h combine to form a new peak of advanced mine pressure. Its location must satisfy the following conditions: In the formula: The new peak pressure point at the advanced cutting position; Lane width; Based on the three constraints, the final cutting height is determined. ,angle tunnel geometry The distance between the peak point jump to the other side of the retreat channel, controlled by several human technical factors, and the basic support resistance of the roadway. The relationship between them satisfies: In the formula: coefficient of friction; Triaxial stress coefficient ; Shear strength; Cohesion; internal friction angle; Stress concentration factor; The density of the overlying rock; , burial depth; Resistance to the pullback channel support.

2. The method for roof cutting and pressure relief according to claim 1 for realizing the jump retreat channel at the peak point of the mining pressure at the end of the working face, characterized in that, In step a, before the working face completes the retreat passage, the peak point of the mine pressure is made to jump from the side of the retreat passage close to the working face to the solid coal on the other side of the retreat passage using the top cutting technology, and a method is given for the roadway support parameters.

3. The method for roof cutting and pressure relief according to claim 1 for realizing the jump retreat channel at the peak point of the mining pressure at the end of the working face, characterized in that, In step b, during the mining period, a pre-moving peak pressure is formed in front of the working face. Based on the size of the peak pressure and its distance from the working face, technical measures are taken to adjust the mining height and mining speed during the final mining phase to control the mining pressure. Furthermore, predictions are made regarding the peak pressure jumping to the other side of the retreat channel. In the formula: The distance between the peak point of the mine pressure ahead of the working face and its distance; , pick high.

4. The method for roof cutting and pressure relief according to claim 1 for realizing the jump retreat channel at the peak point of the final mining pressure in the working face, characterized in that, In step c, the distance between the fixed peak point of the retreat channel and the retreat channel is determined according to the bearing capacity and failure characteristics of the surrounding rock of the retreat channel: In the formula: The distance between the peak point of the fixed mining pressure on one side of the retreat channel and its location; Height of the retreat passage, mining height at the final stage of the working face Withdrawal channel height Take the same data, that is, control the sampling height.

5. The method for roof cutting and pressure relief according to claim 1 for realizing the jump retreat channel at the peak point of the final mining pressure in the working face, characterized in that, In step d, the moving peak point of the mining pressure during the working face mining gradually approaches and couples with the fixed peak point on one side of the retreat channel, and forms the final superimposed peak point at the fixed peak point position on one side of the retreat channel. During the gradual approach, the focus is on the change of the stress peak, analyzing the stability of the coal pillar between the peak point and the retreat channel, and determining to manually cut the roof at the position of the final superimposed peak point so that the peak can jump directly from the side of the retreat channel close to the working face to the other side, so that the roof of the retreat channel avoids the peak of the mining pressure.

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