Working face outburst prevention and control method based on mining mode

Abstract

The invention provides a working face outburst prevention and control method based on a mining mode. The method comprises the following steps that S1, three-direction stress of a coal rock mass is defined; s2, classifying and dividing stress loading and unloading paths of the coal and rock mass of the working face in a mining mode according to a loading and / or unloading mode of the coal and rock mass under three-way stress; s3, in the coal mining process, according to the types of stress loading and unloading paths generated by coal and rock masses of different working faces, the tunneling speed is correspondingly set, and / or the corresponding stress is controlled. According to the working face outburst prevention and treatment method, mining modes are classified according to different stress loading and unloading paths, mechanical behaviors of the coal body under different mining conditions can be accurately described and predicted, and the breaking strength and the gas emission risk of the coal body are accurately evaluated; and different tunneling rates are adopted for different mining modes, the tunneling rate can be adjusted according to the actual mechanical state of the coal body, and the risk of coal and gas outburst is remarkably reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of coal and gas outburst prevention and control, and to a method for preventing and controlling the danger of outburst in an underground coal mine excavation working face, and in particular to a method for preventing and controlling an outburst in a working face based on a mining mode. Background Art

[0002] Coal and gas outburst disasters have restricted the safe mining of coal mines with their long-term, complex and recurring nature. The continuous occurrence of outburst accidents in recent years indicates that the prevention and control of outburst disasters has entered a bottleneck period. At present, in order to prevent and control outburst disasters in coal mines, my country has put forward a key strategy of "regional comprehensive outburst prevention measures first, local comprehensive outburst prevention measures as a supplement", and has implemented a "four-in-one" comprehensive prevention and control strategy for regional and local outburst prevention measures. However, the core of these outburst prevention measures is to reduce the gas content in the coal seam to below the safety threshold.

[0003] Research shows that the key to the incubation and initiation of coal outbursts lies in the timely exposure of coal bodies. Due to mining disturbance, the coal bodies in front of the working face are inevitably subjected to concentrated stress before being exposed. With the stress transition and transient equilibrium, continuous damage and instability are caused under the action of residual stress. Therefore, the occurrence of a coal and gas outburst accident is that after artificial mining disturbance, the three-dimensional stress in the stratum is readjusted and distributed, causing the deformation and destruction of the coal body. This process is accompanied by the desorption and migration of gas in the coal seam, which induces outbursts after being incubated under certain conditions. The instability of coal body damage caused by ground stress under mining is a necessary condition for the occurrence of outbursts. The degree of coal body damage and instability plays a key role in the distribution of outburst strength. Therefore, according to the mechanical conditions met at different stages in the process of coal body damage and instability, it is the key to the prevention and control of outbursts to impose measures through artificial intervention to hinder the development of the key stages of the outburst incubation process. In addition, studies have shown that whether the coal body under dynamic load will become unstable and fail is not only affected by the load size but also closely related to the stress change path. When carrying out outburst prevention work, the stress state of the coal seam, the mining rate and method should also be considered. Therefore, it is urgent to provide a method for preventing and controlling outbursts in the excavation working face to fill the gap in the existing technology. Summary of the invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the present invention provides a method for preventing and controlling a working face outburst based on a mining mode, which specifically includes the following technical solutions:

[0005] A method for preventing and controlling a working face outburst based on a mining mode comprises the following steps:

[0006] S1, defines the three-dimensional stress of coal rock mass, that is, the stress in the direction of coal seam strike is the minimum principal stress, the stress perpendicular to the direction of coal seam strike in the horizontal plane is the intermediate principal stress, and the stress perpendicular to the direction of coal seam strike in the vertical plane is the maximum principal stress;

[0007] S2, according to the loading and / or unloading mode of the coal-rock mass under triaxial stress, classify and divide the stress loading and unloading paths of the coal-rock mass in the working face under the mining mode;

[0008] S3, during the coal mining process, the excavation rate is set and / or the corresponding stress magnitude is controlled according to the type of stress loading and unloading path occurring in the coal and rock mass at different working faces.

[0009] Furthermore, in step S2, the stress loading and unloading paths of the coal and rock mass of the working face in the mining mode are divided into the following four types:

[0010] Stress path I: One-way progressive unloading mode with constant pressure of the intermediate principal stress, that is, the minimum principal stress is progressively unloaded, the maximum principal stress is progressively loaded, and the intermediate principal stress remains constant;

[0011] Stress path II: Bidirectional progressive unloading mode, i.e., the maximum principal stress is progressively loaded, and the intermediate principal stress and the minimum principal stress are progressively unloaded;

[0012] Stress path III: Bidirectional progressive loading, minimum principal stress sudden unloading mode, that is, the maximum principal stress and the intermediate principal stress are progressively loaded, and the minimum principal stress is suddenly unloaded;

[0013] Stress path IV: bidirectional loading with the minimum principal stress kept constant, unidirectional servo mode, that is, the maximum principal stress and the intermediate principal stress are loaded progressively, and the minimum principal stress is kept constant.

[0014] Furthermore, for stress path I, the excavation rate of the working face is calculated by the following formula:

[0015]

[0016] In the formula, v Ⅰ is the excavation rate of the working face of stress path I, mm / s; δ Ⅰ is the peak compressive strength of the stress path, MPa.

[0017] Furthermore, for stress path II, the excavation rate of the working face is calculated by the following formula:

[0018]

[0019] In the formula, v Ⅱ is the excavation rate of the working face of stress path II, mm / s; δ Ⅱ is the peak compressive strength of stress path II, MPa.

[0020] Furthermore, for stress path III, the minimum stress to which the coal and rock mass of the working face can be unloaded is calculated by the following formula:

[0021]

[0022] In the formula, σ Ⅲ is the minimum stress to which the coal and rock mass of the working face can be unloaded, MPa; δ Ⅲ is the peak compressive strength of stress path III, MPa.

[0023] Furthermore, for stress path IV, the minimum servo stress of the coal and rock mass at the working face is calculated by the following formula:

[0024]

[0025] In the formula, σ Ⅳ is the minimum servo stress of coal and rock mass at the working face, MPa; δ Ⅳ is the peak compressive strength of stress path IV, MPa.

[0026] Furthermore, the peak compressive strength correction factor of the stress path is set to 0.8.

[0027] Furthermore, corresponding stress loading and unloading path types are set for different coal mining working faces, specifically:

[0028] The stress loading and unloading path type of the coal mining face is stress path I;

[0029] The stress loading and unloading path type of the coal roadway excavation working face is stress path II;

[0030] The stress loading and unloading path type of the Shimen coal uncovering working face is stress path III;

[0031] The type of stress loading and unloading path for preventing coal wall disasters at the coal roadway excavation working face is stress path IV.

[0032] Based on the above technical solution, the present invention has the following beneficial effects:

[0033] 1. The method for preventing and controlling working face outbursts recorded in the present invention classifies the mining modes according to four different stress loading and unloading paths. This scientific and refined classification method can accurately describe and predict the mechanical behavior of the coal body under different mining conditions, thereby more accurately evaluating the destructive strength of the coal body and the risk of gas outburst.

[0034] 2. The method for preventing and controlling coal and gas outbursts in the working face recorded in the present invention adopts differentiated excavation rates for different mining modes, can adjust the excavation rate according to the actual mechanical state of the coal body, significantly reduce the risk of coal and gas outbursts, and improve the safety and excavation efficiency of the excavation process.

[0035] 3. The method for preventing and controlling gas outbursts on working faces recorded in the present invention adopts differentiated gas control measures according to different mining modes, effectively improving the effect of gas outburst prevention measures and the efficiency of working face excavation. It is a precise deployment of disaster prevention and control based on source, intensity, time and space, and realizes the concept of source-based identification of gas outbursts. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 : Schematic diagram of the working face protrusion prevention method described in the present invention;

[0037] Figure 2 :Schematic diagram of mechanical loading and unloading stress path I during coal-rock outburst process;

[0038] Figure 3 :Schematic diagram of mechanical loading and unloading stress path II during coal-rock outburst process;

[0039] Figure 4 :Schematic diagram of mechanical loading and unloading stress path III during coal-rock outburst process;

[0040] Figure 5 :Schematic diagram of mechanical loading and unloading stress path IV during coal-rock outburst process; DETAILED DESCRIPTION

[0041] It should be noted that:

[0042] 1. Certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. Therefore, the specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in components' functions as the criterion for distinction. Unless otherwise defined, the technical terms or scientific terms used in this disclosure should have the common meanings understood by people with ordinary skills in the field to which this disclosure belongs.

[0043] 2. Mining mode refers to the laws and patterns of stress changes, deformation and destruction of coal rock mass and strata caused by mining activities during the coal mining process.

[0044] 3. Three-dimensional force refers to the principal stresses that the coal rock mass is subjected to in the X-axis, Y-axis, and Z-axis directions. The X-axis direction refers to the direction of the coal seam, the Y-axis direction refers to the direction perpendicular to the direction of the coal seam in the horizontal plane, and the Z-axis direction refers to the direction perpendicular to the direction of the coal seam in the vertical plane. Among them: σ1 is the maximum principal stress, indicating the force of the coal rock mass in the Z-axis direction; σ2 is the intermediate principal stress, indicating the force of the coal rock mass in the Y-axis direction; σ3 is the minimum principal stress, indicating the force of the coal rock mass in the X-axis direction.

[0045] The following is combined with Figure 1 To Attachment Figure 5, the present invention is described in detail by way of embodiments.

[0046] A method for preventing and controlling a working face outburst based on a mining mode comprises the following steps:

[0047] S1, during coal mining, outbursts are accompanied by sudden or gradual loading and unloading of coal and rock mass under three-dimensional forces. In this process, the loading and unloading directions and rates of coal and rock mass are complex and changeable, and are completely different from each other. In order to accurately describe and predict the mechanical behavior of coal and rock mass under different mining conditions, according to the loading and / or unloading mode of the main stress of coal and rock mass in the X-axis, Y-axis, and Z-axis directions, the stress loading and unloading paths of coal and rock mass under mining mode are classified as follows:

[0048] Stress path I is a unidirectional progressive unloading mode in which the intermediate principal stress maintains a constant pressure, that is, in stress path I, σ3 is progressively unloaded, σ1 is progressively loaded, and σ2 remains constant;

[0049] Stress path II is a bidirectional progressive unloading mode, that is, in stress path II, σ1 is progressively loaded, and σ2 and σ3 are progressively unloaded;

[0050] Stress path III is a bidirectional progressive loading and minimum principal stress sudden unloading mode, that is, in stress path III, σ1 and σ2 are progressively loaded, and σ3 is suddenly unloaded;

[0051] Stress path IV is a bidirectional loading and unidirectional servo mode in which the minimum principal stress is kept constant, that is, in stress path IV, σ1 and σ2 are loaded progressively, and σ3 remains constant.

[0052] S2, in order to improve the safety and efficiency of the excavation process, during the excavation process, different excavation rates and / or corresponding stress magnitudes are set according to the stress loading and unloading path types of the coal and rock mass at the working face, which can effectively reduce the risk of coal and gas outbursts in the coal and rock mass and improve the safety and efficiency of the excavation process. Specifically, the following calculation methods are included:

[0053] S201, for stress path I, the working face excavation rate is calculated by the following formula:

[0054]

[0055] S202, for stress path II, the working face excavation rate is calculated by the following formula:

[0056]

[0057] S203, for stress path III, the minimum stress to which the coal and rock mass of the working face can be unloaded is calculated by the following formula:

[0058]

[0059] S204, for stress path IV, the minimum servo stress of the coal and rock mass at the working face is calculated by the following formula:

[0060]

[0061] In the above formula:

[0062] v Ⅰ 、v Ⅱ They are the working face advancement rates of stress path I and stress path II, mm / s;

[0063] σ Ⅲ is the minimum stress to which the coal and rock mass at the working face can be unloaded, MPa;

[0064] σ Ⅳ is the minimum servo stress of coal and rock mass at the working face, MPa;

[0065] δ Ⅰ -δ Ⅳ They are the peak compressive strengths of stress path I to stress path IV, MPa.

[0066] The calculation method of peak compressive strength is briefly described as follows:

[0067] The original triaxial stresses of the coal body in front of the working face under different stress paths were determined. Based on the original triaxial stresses, triaxial compression tests of coal samples were carried out in the laboratory in accordance with GB / T23561.9-2009 “Methods for determination of physical and mechanical properties of coal and rock” to determine the peak compressive strength of the coal samples. The peak compressive strength of the coal samples determined in the experiment can be used to replace the peak compressive strength during the excavation process.

[0068] S3, in order to ensure that the coal and rock mass at the working face will not exceed its yield point during the excavation process and avoid the instability caused by the coal and rock mass entering the complete plastic yield state, the peak compressive strength δ in step S2 is Ⅰ -δ Ⅳ To make corrections, use:

[0069] S301, in stress path I and stress path II, set the peak compressive strength δ Ⅰ and δ Ⅱ The safety factor is 0.8, that is, the maximum excavation rate of the working face is determined by 0.8 times the peak compressive strength in stress path I and stress path II;

[0070] S302, in stress path III, set the peak compressive strength δ Ⅲ The safety factor is 0.8, that is, the minimum stress to which the working surface can be suddenly unloaded is determined by 0.8 times the peak compressive strength;

[0071] S303, in stress path IV, set the peak compressive strength δ Ⅳ The safety factor is 0.8, that is, the minimum servo stress of the working surface is determined by 0.8 times the peak compressive strength.

[0072] S4, in order to better control and prevent outburst accidents in mining working faces, the main corresponding stress loading and unloading path types are set for different working faces, specifically:

[0073] The stress loading and unloading path type of the coal mining face is stress path I;

[0074] The stress loading and unloading path type of the coal roadway excavation working face is stress path II;

[0075] The stress loading and unloading path type of the Shimen coal uncovering working face is stress path III;

[0076] The type of stress loading and unloading path for preventing coal wall disasters at the coal roadway excavation working face is stress path IV.

[0077] S5, the strength of the coal body is significantly affected by the stress path. Whether the coal body under dynamic load is unstable or not is closely related to the stress change path in addition to the load size. Therefore, in addition to taking the excavation rate of step S2 or S3 and / or controlling the corresponding stress size for outburst prevention and control on the already formed stress path, corresponding gas control measures can also be taken in accordance with the provisions of the "Detailed Rules for Preventing and Controlling Coal and Gas Outbursts" to strengthen the gas extraction effect and further reduce the gas occurrence level.

Claims

1. A method for preventing and controlling outbursts in a working face based on a mining mode, characterized in that: The following steps are involved: S1, defines the three-dimensional stress of coal rock mass, that is, the stress in the direction of coal seam strike is the minimum principal stress, the stress perpendicular to the direction of coal seam strike in the horizontal plane is the intermediate principal stress, and the stress perpendicular to the direction of coal seam strike in the vertical plane is the maximum principal stress; S2, according to the loading and / or unloading mode of the coal-rock mass under triaxial stress, classify and divide the stress loading and unloading paths of the coal-rock mass in the working face under the mining mode; S3, during the coal mining process, the excavation rate is set and / or the corresponding stress magnitude is controlled according to the type of stress loading and unloading path occurring in the coal and rock mass at different working faces.

2. A method for preventing and controlling working face outburst based on mining mode according to claim 1, characterized in that: In step S2, the stress loading and unloading paths of the coal and rock mass of the working face in the mining mode are divided into the following four types: Stress path I: One-way progressive unloading mode with constant pressure of the intermediate principal stress, that is, the minimum principal stress is progressively unloaded, the maximum principal stress is progressively loaded, and the intermediate principal stress remains constant; Stress path II: Bidirectional progressive unloading mode, i.e., the maximum principal stress is progressively loaded, and the intermediate principal stress and the minimum principal stress are progressively unloaded; Stress path III: Bidirectional progressive loading, minimum principal stress sudden unloading mode, that is, the maximum principal stress and the intermediate principal stress are progressively loaded, and the minimum principal stress is suddenly unloaded; Stress path IV: bidirectional loading with the minimum principal stress kept constant, unidirectional servo mode, that is, the maximum principal stress and the intermediate principal stress are loaded progressively, and the minimum principal stress is kept constant.

3. A method for preventing and controlling working face outburst based on mining mode according to claim 2, characterized in that: For stress path I, the excavation rate of the working face is calculated by the following formula: In the formula, v Ⅰ is the excavation rate of the working face of stress path I, mm / s; δ Ⅰ is the peak compressive strength of the stress path, MPa.

4. A method for preventing and controlling working face outburst based on mining mode according to claim 2, characterized in that: For stress path II, the working face advancement rate is calculated by the following formula: In the formula, v Ⅱ is the excavation rate of the working face of stress path II, mm / s; δ Ⅱ is the peak compressive strength of stress path II, MPa.

5. The method for preventing and controlling working face outburst based on mining mode according to claim 2 is characterized in that: For stress path III, the minimum stress that the coal and rock mass of the working face can be unloaded to is calculated by the following formula: In the formula, σ Ⅲ is the minimum stress to which the coal and rock mass at the working face can be unloaded, MPa; δ Ⅲ is the peak compressive strength of stress path III, MPa.

6. A method for preventing and controlling working face outburst based on mining mode according to claim 2, characterized in that: For stress path IV, the minimum servo stress of the coal and rock mass at the working face is calculated by the following formula: In the formula, σ Ⅳ is the minimum servo stress of coal and rock mass at the working face, MPa; δ Ⅳ is the peak compressive strength of stress path IV, MPa.

7. A method for preventing and controlling a working face outburst based on a mining mode according to any one of claims 3 to 6, characterized in that: Set the peak compressive strength correction factor of the stress path to 0.

8.

8. A method for preventing and controlling a working face outburst based on a mining mode according to any one of claims 2 to 6, characterized in that: The corresponding stress loading and unloading path types are set for different coal mining working faces, specifically: The stress loading and unloading path type of the coal mining face is stress path I; The stress loading and unloading path type of the coal roadway excavation working face is stress path II; The stress loading and unloading path type of the Shimen coal uncovering working face is stress path III; The type of stress loading and unloading path for preventing coal wall disasters at the coal roadway excavation working face is stress path IV.

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