A method for evaluating the pre-control effect of surface fracturing in steeply inclined coal seams during rockburst.

Abstract

This invention provides a method for evaluating the pre-control effect of surface fracturing in steeply inclined coal seams prone to rockburst. The method includes: setting up a microseismic monitoring system according to a preset fracturing control range; monitoring microseismic events and underground microseismic energy events through the microseismic monitoring system to obtain the surface fracturing fracture propagation range, the total energy ratio of underground microseismic energy events, and the ratio of the total number of events; obtaining the average working resistance ratio of the working face support and the average dynamic load coefficient of the working face period based on the change in working resistance of the working face support before and after the fracturing process; monitoring the underground roadway using multi-point displacement gauges to obtain the deformation of the surrounding rock in the roadway; calculating the total score for the surface fracturing effect evaluation based on the above data and classifying the pre-control effect into levels. This method, by analyzing and classifying the surface fracturing pre-control effect of steeply inclined coal seams prone to rockburst, ensures that the pre-control effect achieves the expected results and guarantees the safe and efficient mining of the working face.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ground fracturing for rock burst in steeply inclined coal seam, and particularly relates to a method for evaluating the effect of ground fracturing for rock burst in steeply inclined coal seam. BACKGROUND

[0002] With the gradual depletion of shallow resources, coal mining develops to deep part, and the ground stress of coal and rock environment is high, and the coal and rock mass is easy to accumulate high elastic energy, especially under the mining condition of steeply inclined coal seam, the coal seam environment is complex, which makes the mining process easy to induce mine earthquake and has high impact risk, and seriously threatens the safety production of mine.

[0003] In order to reduce the harm degree of rock burst under the mining condition of steeply inclined coal seam and prevent the occurrence of rock burst accident, the ground fracturing technology is usually used to prevent rock burst in steeply inclined coal seam. Therefore, it is very necessary to design a method for evaluating the effect of ground fracturing for rock burst in steeply inclined coal seam. SUMMARY

[0004] The purpose of the present application is to provide a method for evaluating the effect of ground fracturing for rock burst in steeply inclined coal seam, so as to analyze and classify the effect of ground fracturing for rock burst in steeply inclined coal seam, ensure that the effect of prevention reaches the expected effect, and ensure the safe and efficient mining of the working face.

[0005] To achieve the above purpose, the present application provides the following scheme:

[0006] A method for evaluating the effect of ground fracturing for rock burst in steeply inclined coal seam, comprising the following steps:

[0007] A microseismic monitoring system is set according to a preset fracturing control range; the microseismic monitoring system comprises a ground detector and a downhole detector;

[0008] The microseismic events in the fracturing process are monitored by the ground detector to obtain the ground fracturing crack extension range; the ground fracturing crack extension range comprises a horizontal extension range and a vertical extension range;

[0009] The downhole microseismic energy events in the fracturing process are monitored by the downhole detector to obtain the total energy ratio and the total number ratio of the downhole microseismic energy events;

[0010] The average working resistance ratio of the working face support and the average dynamic load coefficient of the working face periodic pressure are obtained by the change amount of the working resistance of the working face support before and after the fracturing process;

[0011] The deformation amount of the roadway surrounding rock is obtained by monitoring the downhole roadway by the multi-point displacement meter;

[0012] The ground fracturing effect evaluation total score is calculated according to the horizontal extension range, the vertical extension range, the total energy ratio of the downhole microseismic energy event, the total number ratio of the downhole microseismic energy event, the average working resistance ratio of the working face support, the average dynamic load coefficient of the working face periodic pressure and the roadway surrounding rock deformation amount, and the ground fracturing pre-control effect of the rock burst in the steep coal seam is graded according to the ground fracturing effect evaluation total score.

[0013] Optionally, the ground detectors are equidistantly arranged on a circle with the fracturing well mouth as the center; the ground detectors are 6; and the radius of the circle with the fracturing well mouth as the center is calculated by the following formula: Wherein, L is the radius, and Z is the length of the fracturing control range.

[0014] Optionally, the downhole detectors are 3; the downhole detectors are arranged at the center of the fracturing control range and on both sides of the fracturing control range; and the calculation formula of the fracturing control range is as follows: Wherein, M is the fracturing control range.

[0015] Optionally, the calculation formula of the ground fracturing effect evaluation total score is as follows: Q=0.2xA+0.2xB+0.1xC+0.1xD+0.15xE+0.15xF+0.1xG; wherein, Q is the ground fracturing effect evaluation total score, A is the horizontal extension range score, B is the vertical extension range score, C is the total energy ratio score of the downhole microseismic energy event, D is the total number ratio score of the downhole microseismic energy event, E is the average working resistance ratio score of the working face support, F is the average dynamic load coefficient score of the working face periodic pressure, and G is the deformation amount score of the roadway surrounding rock.

[0016] Optionally, the ground fracturing pre-control effect of the rock burst in the steep coal seam is graded according to the ground fracturing effect evaluation total score, and specifically includes the following steps.

[0017] When 0≤Q<1, the ground fracturing pre-control effect of the rock burst in the steep coal seam is determined as the first level;

[0018] When 1≤Q<2, the ground fracturing pre-control effect of the rock burst in the steep coal seam is determined as the second level;

[0019] When 2≤Q<3, the ground fracturing pre-control effect of the rock burst in the steep coal seam is determined as the third level;

[0020] When 3≤Q≤4, the ground fracturing pre-control effect of the rock burst in the steep coal seam is determined as the fourth level.

[0021] According to the specific embodiments of the present application, the present application discloses the following technical effects: the present application provides a ground fracturing pre-control effect evaluation method for rock burst in steeply inclined coal seams, which comprises the following steps: setting a microseismic monitoring system according to a preset fracturing control range; the microseismic monitoring system comprises a ground detector and a downhole detector; monitoring the microseismic events in the fracturing process through the ground detector to obtain the ground fracturing crack propagation range; the ground fracturing crack propagation range comprises a horizontal propagation range and a vertical propagation range; monitoring the downhole microseismic energy events in the fracturing process through the downhole detector to obtain the total energy ratio and the total number ratio of the downhole microseismic energy events; obtaining the average working resistance ratio of the working face support and the average dynamic load coefficient of the working face periodic pressure through the change amount of the working resistance of the working face support before and after the fracturing process; monitoring the underground roadway through a multi-point displacement meter to obtain the deformation amount of the roadway surrounding rock; calculating the ground fracturing effect evaluation total score according to the horizontal propagation range, the vertical propagation range, the total energy ratio of the downhole microseismic energy events, the total number ratio of the downhole microseismic energy events, the average working resistance ratio of the working face support, the average dynamic load coefficient of the working face periodic pressure and the deformation amount of the roadway surrounding rock, and grading the ground fracturing pre-control effect for rock burst in steeply inclined coal seams according to the ground fracturing effect evaluation total score. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings described below only show some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0023] Figure 1 The flow chart of the ground fracturing pre-control effect evaluation method for rock burst in steeply inclined coal seams of the present application embodiment;

[0024] Figure 2 The schematic diagram of the microseismic monitoring system of the present application embodiment.

[0025] The drawings show: 1, ground detector; 2, downhole detector. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments only show some embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0027] The above objects, characteristics and advantages of the present application will be more apparent and understandable from the following detailed description of the present application in conjunction with the accompanying drawings and specific embodiments.

[0028] As shown in the drawings, Figure 1 The present application takes the ground fracturing process of rock burst in a steeply inclined coal seam in a certain mine in Gansu as an example. The example provides a rock burst ground fracturing pre-control effect evaluation method for steeply inclined coal seams, which comprises the following steps:

[0029] Step 100: Set up a microseismic monitoring system according to a preset fracturing control range. The microseismic monitoring system comprises ground geophones 1 and underground geophones 2.

[0030] Specifically, the comprehensive index method is used to evaluate and predict the rock burst danger degree of the mining area, and the fracturing control range is selected according to the evaluation and prediction results. The length Z of the fracturing control range in this example is 240 m.

[0031] Specifically, as shown in the drawings, Figure 2 The ground geophones 1 are equidistantly arranged on a circle with the wellhead of the fracturing well as the center and a radius L. There are 6 ground geophones 1. The calculation formula of the radius of the circle with the wellhead of the fracturing well as the center is: Wherein, L is the radius, and Z is the length of the fracturing control range. The radius L of this example is 80 m.

[0032] Specifically, the underground geophones 2 are 3. The underground geophones 2 are arranged in the crossheading of the working face. One is arranged at the center of the fracturing control range in the crossheading, and one is arranged on each of the left and right sides of the fracturing control range, with an excess length of M. The calculation formula of the excess fracturing control range is: The excess length M of this example is 40 m.

[0033] Step 200: Monitor the microseismic events in the fracturing process through the ground geophones 1 to obtain the ground fracturing crack propagation range.

[0034] Specifically, the ground fracturing crack propagation range comprises a horizontal propagation range and a vertical propagation range. The horizontal propagation range of this example is 218 m, and the vertical propagation range is 49.6 m.

[0035] Step 300: Monitor the underground microseismic energy events in the fracturing process through the underground geophones 2 to obtain the total energy ratio and the total number of events of the underground microseismic energy events.

[0036] Specifically, the time range for monitoring the underground microseismic energy events in the fracturing process through the underground geophones 2 is one month before and after the implementation of the fracturing process. The total energy ratio of the underground microseismic energy events in this example is 1.17, and the total number of events of the underground microseismic energy events is 1.26.

[0037] Step 400: Obtain the average working resistance ratio of the working face support and the working face period by measuring the change in working resistance of the working face support before and after the fracturing process, and then use this to calculate the average dynamic load coefficient.

[0038] Specifically, in this embodiment, the average working resistance ratio of the working face support is 1.31, and the average dynamic load coefficient of the working face periodic pressure is 1.24.

[0039] Step 500: Monitor the underground roadway using multi-point displacement gauges to obtain the deformation of the surrounding rock.

[0040] Specifically, multiple displacement gauges are installed in the underground roadway to monitor the deformation of the surrounding rock within the fracturing control range after surface fracturing. In this embodiment, the deformation of the surrounding rock is 356 mm.

[0041] Step 600: Calculate the total score for surface fracturing effect evaluation based on the horizontal expansion range, vertical expansion range, total energy ratio of underground microseismic energy events, total number of underground microseismic energy events ratio, average working resistance ratio of working face supports, average dynamic load coefficient of working face periodic pressure, and deformation of surrounding rock in the roadway. Then, classify the pre-control effect of surface fracturing for rockburst in steeply inclined coal seams according to the total score for surface fracturing effect evaluation.

[0042] Specifically, the evaluation index scores are first obtained based on the horizontal extension range (a), vertical extension range (b), the total energy ratio of downhole microseismic energy events (c), the total number of downhole microseismic energy events (d), the average working resistance ratio of the working face support (e), the average dynamic load coefficient of the working face periodic pressure (f), and the deformation of the surrounding rock in the roadway (g). The judgment criteria for different evaluation index scores are as follows:

[0043] When 0 ≤ a < 60, the horizontal expansion range score is 1; when 60 ≤ a < 120, the horizontal expansion range score is 2; when 120 ≤ a < 180, the horizontal expansion range score is 3; when 180 ≤ a, the horizontal expansion range score is 4. In this embodiment, the horizontal expansion range score is 4.

[0044] When 0 ≤ b < 15, the vertical expansion range score is 1; when 15 ≤ b < 30, the vertical expansion range score is 2; when 30 ≤ b < 45, the vertical expansion range score is 3; when 45 ≤ b, the vertical expansion range score is 4. In this embodiment, the vertical expansion range score is 4.

[0045] When 1.00 ≤ c < 1.05, the total energy ratio score of the downhole microseismic energy event is 1; when 1.05 ≤ c < 1.15, the total energy ratio score of the downhole microseismic energy event is 2; when 1.15 ≤ c < 1.20, the total energy ratio score of the downhole microseismic energy event is 3; when 1.20 ≤ c, the total energy ratio score of the downhole microseismic energy event is 4. The total energy ratio score of the downhole microseismic energy event in this embodiment is 3.

[0046] When 1.00 ≤ d < 1.15, the total number ratio score of the downhole microseismic energy event is 1; when 1.15 ≤ d < 1.30, the total number ratio score of the downhole microseismic energy event is 2; when 1.30 ≤ d < 1.40, the total number ratio score of the downhole microseismic energy event is 3; when 1.40 ≤ d, the total number ratio score of the downhole microseismic energy event is 4. The total number ratio score of the downhole microseismic energy event in this embodiment is 2.

[0047] When 1.00 ≤ e < 1.10, the average working resistance ratio score of the face support is 1; when 1.10 ≤ e < 1.20, the average working resistance ratio score of the face support is 2; when 1.20 ≤ e < 1.30, the average working resistance ratio score of the face support is 3; when 1.30 ≤ e, the average working resistance ratio score of the face support is 4. The average working resistance ratio score of the face support in this embodiment is 4.

[0048] When 1.50 < f, the average dynamic load coefficient score of the periodic weighting of the face is 1; when 1.35 ≤ f < 1.50, the average dynamic load coefficient score of the periodic weighting of the face is 2; when 1.20 ≤ f < 1.35, the average dynamic load coefficient score of the periodic weighting of the face is 3; when f < 1.20, the average dynamic load coefficient score of the periodic weighting of the face is 4. The average dynamic load coefficient score of the periodic weighting of the face in this embodiment is 3.

[0049] When 1500 < g, the score of the roadway surrounding rock deformation is 1; when 900 ≤ g < 1500, the score of the roadway surrounding rock deformation is 2; when 300 ≤ g < 900, the score of the roadway surrounding rock deformation is 3; when g < 300, the score of the roadway surrounding rock deformation is 4. The score of the roadway surrounding rock deformation in this embodiment is 3.

[0050] Specifically, the formula for calculating the total score of the surface fracturing effect evaluation is: Q = 0.2 × A + 0.2 × B + 0.1 × C + 0.1 × D + 0.15 × E + 0.15 × F + 0.1 × G; where Q is the total score of the surface fracturing effect evaluation, A is the score for the horizontal extension range, B is the score for the vertical extension range, C is the score for the total energy ratio of downhole microseismic energy events, D is the score for the total number of downhole microseismic energy events, E is the score for the average working resistance ratio of the working face support, F is the score for the average dynamic load coefficient of the working face periodic pressure, and G is the score for the deformation of the surrounding rock in the roadway. In this embodiment, the total score Q for the surface fracturing effect evaluation is 3.45.

[0051] More specifically, the specific steps for classifying the pre-control effect of surface fracturing for rockburst in steeply inclined coal seams based on the total score of surface fracturing effect evaluation include:

[0052] When 0≤Q<1, the pre-control effect of surface fracturing for rockburst in steeply inclined coal seams is determined to be poor.

[0053] When 1≤Q<2, the pre-control effect of surface fracturing for rockburst in steeply inclined coal seams is determined to be of medium level;

[0054] When 2≤Q<3, the pre-control effect of surface fracturing for rockburst in steeply inclined coal seams is determined to be good.

[0055] When 3 ≤ O ≤ 4, the pre-control effect of surface fracturing for rockburst in steeply inclined coal seams is determined to be excellent. In this embodiment, the pre-control effect of surface fracturing for rockburst in steeply inclined coal seams is excellent, indicating that the surface fracturing project has achieved the expected results. Furthermore, the mine pressure intensity significantly decreased during subsequent mining operations, and no strong mine pressure or rockburst phenomena occurred. This verifies the feasibility and correctness of the evaluation method for the pre-control effect of surface fracturing for rockburst in steeply inclined coal seams.

[0056] The beneficial effects of this invention are as follows:

[0057] 1) By analyzing and classifying the pre-control effect of surface fracturing on rockburst in steeply inclined coal seams, the pre-control effect was ensured to achieve the expected results, and the safe and efficient mining of the working face was guaranteed.

[0058] 2) The method of the present invention is accurate and reasonable, and has feasibility, correctness and versatility.

[0059] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0060] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for evaluating the effect of ground fracturing pre-control of rock burst in steep coal seam, characterized in that, The method comprises the following steps: a microseismic monitoring system is set according to a preset fracturing control range; the microseismic monitoring system comprises a ground detector and a downhole detector; a microseismic event in a fracturing process is monitored by the ground detector to obtain a ground fracturing crack propagation range; the ground fracturing crack propagation range comprises a horizontal propagation range and a vertical propagation range; a downhole microseismic energy event in the fracturing process is monitored by the downhole detector to obtain a total energy ratio and a total number ratio of the downhole microseismic energy event; an average working resistance ratio of a working face support and a periodic weighting average dynamic load coefficient of the working face are obtained by a change amount of a working resistance of the working face support before and after the fracturing process; a deformation amount of a roadway surrounding rock is obtained by monitoring the roadway surrounding rock by a multi-point displacement meter; a ground fracturing effect evaluation total score is calculated according to the horizontal propagation range, the vertical propagation range, the total energy ratio of the downhole microseismic energy event, the total number ratio of the downhole microseismic energy event, the average working resistance ratio of the working face support, the periodic weighting average dynamic load coefficient of the working face and the deformation amount of the roadway surrounding rock, and a grade of a rock burst ground fracturing pre-control effect of an acute-inclined coal seam is divided according to the ground fracturing effect evaluation total score.

2. The effect evaluation method of rock burst ground fracturing pre-control for steeply inclined coal seam according to claim 1, characterized in that, The ground detectors are equidistantly arranged on a circle with the fracturing well mouth as the center; the ground detectors are 6, and a calculation formula of a radius of the circle with the fracturing well mouth as the center is: Wherein, L is the radius, and Z is the length of the fracturing control range.

3. The effect evaluation method of rock burst ground fracturing pre-control for steeply inclined coal seam according to claim 2, characterized in that, The downhole geophones are 3; the downhole geophones are respectively arranged at the center of the fracturing control range and two sides beyond the fracturing control range; the calculation formula of the fracturing control range is: Wherein, M is beyond the fracturing control range.

4. The effect evaluation method of rock burst ground fracturing pre-control for steeply inclined coal seam according to claim 1, characterized in that, The calculation formula of the ground fracturing effect evaluation total score is: Q=0.2xA+0.2xB+0.1xC+0.1xD+0.15xE+0.15xF+0.1xG; wherein Q is the ground fracturing effect evaluation total score, A is a horizontal propagation range score, B is a vertical propagation range score, C is a total energy ratio score of a downhole microseismic energy event, D is a total number ratio score of the downhole microseismic energy event, E is an average working resistance ratio score of a working face support, F is a periodic weighting average dynamic load coefficient score of the working face, and G is a deformation amount score of a roadway surrounding rock.

5. The effect evaluation method of rock burst ground fracturing pre-control for steeply inclined coal seam according to claim 4, characterized in that, The grade of the rock burst ground fracturing pre-control effect of the acute-inclined coal seam is divided according to the ground fracturing effect evaluation total score, and specifically comprises: when 0≤Q<1, the rock burst ground fracturing pre-control effect of the acute-inclined coal seam is determined as a first grade; when 1≤Q<2, the rock burst ground fracturing pre-control effect of the acute-inclined coal seam is determined as a second grade; when 2≤Q<3, the rock burst ground fracturing pre-control effect of the acute-inclined coal seam is determined as a third grade; when 3≤Q≤4, the rock burst ground fracturing pre-control effect of the acute-inclined coal seam is determined as a fourth grade.

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