A method for evaluating the bearing capacity of intact floor in pressure mining

Abstract

The present invention discloses a method for evaluating the bearing capacity of a complete bottom plate during pressure mining, comprising the following steps: (1) determining the damage depth of the bottom plate; (2) determining whether the bottom plate damage zone has affected the aquifer, and if so, mining is unsafe; otherwise, evaluation is performed using steps (3)-(8); (3) determining the location of a specific water-bearing rock layer, coring, and obtaining the porosity n of the water-bearing rock layer; (4) obtaining the tensile strength values ​​of the water-bearing rock layer itself, the overlying rock layer of the aquifer, and the rock samples of the contact zone between the aquifer and the overlying rock layer; (5) obtaining the water pressure value of the top plate of the water-bearing rock layer; (6) obtaining the effective water pressure of the water-bearing rock layer; (7) obtaining the effective tensile strength and determining the minimum effective tensile strength; and (8) calculating the water inrush safety factor e. The method has a simple principle, is easy to apply, and has a more accurate evaluation result.

Description

Technical Field

[0001] The invention relates to the technical field of coal seam floor pressure bearing capacity evaluation, and in particular to a method for evaluating the pressure bearing capacity of a complete floor during pressure mining. Background Art

[0002] Water damage is one of the five major disasters in underground coal mining. Once it occurs, it often causes major casualties and property losses. There are mainly roof water damage, floor water damage, old empty water damage and other forms. The channels for water inrush include natural channels, artificial channels and disturbance activation channels. The prevention and control of mine water damage is relatively difficult. The specific work is divided into two aspects: prevention and control. The premise of prevention and control is to scientifically carry out water damage risk assessment. At present, the evaluation of water damage in bottom plate pressure mining mainly refers to the water inrush coefficient method in the "Coal Mine Water Prevention and Control Detailed Rules". This method is an empirical method that summarizes the examples of water inrush at home and abroad for decades. The water inrush coefficient method calculates the ratio of the water pressure of the bottom plate aquifer to the thickness of the bottom plate aquiclude, and then compares the water inrush coefficient limit value specified in the "Coal Mine Water Prevention and Control Detailed Rules" to evaluate the safety of the bottom plate under pressure mining. Since this method is summarized from experience, the evaluation conclusion is generally conservative and the evaluation result is not accurate enough. Summary of the invention

[0003] In view of the above-mentioned technical deficiencies, the purpose of the present invention is to provide a method for evaluating the bearing capacity of a complete floor in pressure mining, which has a simple principle, is easy to apply, and provides more accurate evaluation results.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The present invention provides a method for evaluating the bearing capacity of a complete floor in pressure mining, comprising the following steps:

[0006] (1) Determine the damage depth of the working face floor under mining conditions;

[0007] (2) Compare the damage depth determined in step (1) with the top surface of the water-bearing rock layer in the working face floor and the bottom boundary of the floor damage zone. If the floor damage zone has affected the aquifer, mining at the working face is unsafe and a water disaster will occur. Otherwise, use steps (3) to (8) for evaluation.

[0008] (3) Determine the location of the specific water-bearing rock formation, drill and sample the water-bearing rock formation itself, the overlying rock formation, and the contact zone between the aquifer and the overlying rock formation to obtain core samples; obtain the porosity n of the water-bearing rock formation by coring the water-bearing rock formation through multiple holes and long distances;

[0009] (4) Obtain the tensile strength values ​​of the rock samples of the aquifer itself, the overlying rock layer of the aquifer, and the contact zone between the aquifer and the overlying rock layer, which are N1, N2, and N3 respectively;

[0010] (5) Testing and obtaining the roof water pressure value P of the water-bearing rock formation during the collection or coring process;

[0011] (6) Calculate the effective water pressure of the water-bearing rock layer P0 = P × n;

[0012] (7) Calculate the effective tensile strength N of the water-bearing rock layer 1y =N1×(1-n), effective tensile strength of the overlying rock layer of the aquifer N 2y =N2×(1-n), the effective tensile strength of the contact zone between the aquifer and the overlying rock layer N 3y =N3×(1-n), by comparing the effective tensile strength of the three types of rock formations, the minimum effective tensile strength N is determined 0y ;

[0013] (8) The thickness of the overlying rock layer of the aquifer is h, then the water inrush safety factor is e = (N 0y +(h×2.2 / 100)) / P0; if e>1, the evaluated pressure-bearing capacity of the complete bottom plate of the pressurized working face is sufficient, and the working face mining process is safe; otherwise, the working face mining process is unsafe.

[0014] Preferably, in step (1), the microseismic electrical method is used to determine the damage depth of the working face bottom plate.

[0015] Preferably, the microseismic electrical method specifically comprises the following steps:

[0016] (a) Determine the location for the microseismic electrical integrated monitoring system;

[0017] (b) Construction of integrated microseismic electrical monitoring system;

[0018] (c) Obtain monitoring data from the integrated microseismic electrical monitoring system;

[0019] (d) Analyze the temporal and spatial distribution of bottom plate microseismic events and monitor the evolution of current and apparent resistivity in bottom plate sections;

[0020] (e) The damage depth of the working face mining floor is determined by the number of floor microseismic events, energy and density accumulation layers, and the abnormal apparent resistivity area of ​​the monitoring floor section.

[0021] Preferably, the sampling depth of the water-bearing rock formation in step (3) is 5-10 meters.

[0022] Preferably, when coring in step (3), three groups of samples are taken from the corresponding water-bearing stratum itself, the overlying stratum of the aquifer, and the rock samples in the contact zone between the aquifer and the overlying stratum. The tensile strength values ​​N1, N2, and N3 in step (4) are the average values ​​of the tensile strength values ​​of the three groups of samples.

[0023] The beneficial effects of the present invention are:

[0024] The method of the present invention is based on the tensile strength theory, takes into account the porosity of the main water-bearing rock layer of the bottom plate, and draws on the effective stress principle. The method has a simple principle, is easy to apply, and has a more accurate evaluation result. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 This is a schematic diagram of the state of the crushed stone of the present invention when it is not compressed; DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] like Figure 1 As shown, this embodiment provides a method for evaluating the bearing capacity of a complete floor during pressure mining, comprising the following steps:

[0029] (1) Determine the damage depth of the working face floor under mining conditions;

[0030] (2) Compare the damage depth determined in step (1) with the top surface of the water-bearing rock layer in the working face floor and the bottom boundary of the floor damage zone. If the floor damage zone has affected the aquifer, mining at the working face is unsafe and a water disaster will occur. Otherwise, use steps (3) to (8) for evaluation.

[0031] (3) Determine the location of the specific water-bearing rock formation, drill and sample the water-bearing rock formation itself, the overlying rock formation, and the contact zone between the aquifer and the overlying rock formation to obtain core samples; obtain the porosity n of the water-bearing rock formation by coring the water-bearing rock formation through multiple holes and long distances;

[0032] (4) Obtain the tensile strength values ​​of the rock samples of the aquifer itself, the overlying rock layer of the aquifer, and the contact zone between the aquifer and the overlying rock layer, which are N1, N2, and N3 respectively;

[0033] (5) Testing and obtaining the roof water pressure value P of the water-bearing rock formation during the collection or coring process;

[0034] (6) Calculate the effective water pressure of the water-bearing rock layer P0 = P × n;

[0035] (7) Calculate the effective tensile strength N of the water-bearing rock layer 1y =N1×(1-n), effective tensile strength of the overlying rock layer of the aquifer N 2y =N2×(1-n), the effective tensile strength of the contact zone between the aquifer and the overlying rock layer N 3y =N3×(1-n), by comparing the effective tensile strength of the three types of rock formations, the minimum effective tensile strength N is determined 0y ;

[0036] (8) The thickness of the overlying rock layer of the aquifer is h, then the water inrush safety factor is e = (N 0y +(h×2.2 / 100)) / P0; if e>1, the evaluated pressure-bearing capacity of the complete bottom plate of the pressurized working face is sufficient, and the working face mining process is safe; otherwise, the working face mining process is unsafe.

[0037] The sampling depth of the water-bearing rock layer in step (3) is 5-10 meters. When coring in step (3), three groups of samples are taken from the corresponding water-bearing rock layer itself, the overlying rock layer of the water-bearing layer, and the rock samples in the contact zone between the water-bearing layer and the overlying rock layer. The tensile strength values ​​N1, N2, and N3 in step (4) are the average values ​​of the tensile strength values ​​of the three groups of samples, which can make the tensile strength values ​​of the measured samples more accurate.

[0038] In step (1), the damage depth of the working face floor is determined by using a microseismic electrical method, and the microseismic electrical method specifically includes the following steps:

[0039] (a) Determine the location for the microseismic electrical integrated monitoring system;

[0040] (b) Construction of integrated microseismic electrical monitoring system;

[0041] (c) Obtain monitoring data from the integrated microseismic electrical monitoring system;

[0042] (d) Analyze the temporal and spatial distribution of bottom plate microseismic events and monitor the evolution of current and apparent resistivity in bottom plate sections;

[0043] (e) The damage depth of the working face mining floor is determined by the number of floor microseismic events, energy and density accumulation layers, and the abnormal apparent resistivity area of ​​the monitoring floor section.

[0044] The microseismic electrical method described in this embodiment is an existing method well known to those skilled in the art and will not be described in detail here.

[0045] This embodiment uses an existing method well known to those skilled in the art to measure the porosity n of the water-bearing rock formation and the top water pressure value P of the water-bearing rock formation; the specific method will not be described in detail here.

[0046] The method of this embodiment is based on the tensile strength theory, takes into account the porosity of the main water-bearing rock layer of the bottom plate, and draws on the effective stress principle. The method is simple in principle, easy to apply, and the evaluation result is more accurate.

[0047] This embodiment can also be used together with other evaluation methods for comprehensive verification to make the evaluation results more accurate.

[0048] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for evaluating the bearing capacity of a complete floor in pressure mining, characterized in that: The following steps are involved: (1) Determine the damage depth of the working face floor under mining conditions; (2) Compare the damage depth determined in step (1) with the top surface of the water-bearing rock layer in the working face floor and the bottom boundary of the floor damage zone. If the floor damage zone has affected the aquifer, mining at the working face is unsafe and a water disaster will occur. Otherwise, use steps (3) to (8) for evaluation. (3) Determine the location of the specific water-bearing rock formation, drill and sample the water-bearing rock formation itself, the overlying rock formation, and the contact zone between the aquifer and the overlying rock formation to obtain core samples; obtain the porosity n of the water-bearing rock formation by coring the water-bearing rock formation through multiple holes and long distances; (4) Obtain the tensile strength values ​​of the rock samples of the aquifer itself, the overlying rock layer of the aquifer, and the contact zone between the aquifer and the overlying rock layer, which are N1, N2, and N3 respectively; (5) Testing and obtaining the roof water pressure value P of the water-bearing rock formation during the collection or coring process; (6) Calculate the effective water pressure of the water-bearing rock layer P0 = P × n; (7) Calculate the effective tensile strength N of the water-bearing rock layer 1y =N1×(1-n), effective tensile strength of the overlying rock layer of the aquifer N 2y =N2×(1-n), the effective tensile strength of the contact zone between the aquifer and the overlying rock layer N 3y =N3×(1-n), by comparing the effective tensile strength of the three types of rock formations, the minimum effective tensile strength N is determined 0y ; (8) The thickness of the overlying rock layer of the aquifer is h, then the water inrush safety factor is e = (N 0y +(h×2.2 / 100)) / P0; if e>1, the evaluated pressure-bearing capacity of the complete bottom plate of the pressurized working face mining is sufficient, and the working face mining process is safe; otherwise, the working face mining process is unsafe.

2. The method for evaluating the bearing capacity of a complete floor in pressure mining according to claim 1, characterized in that: In step (1), the microseismic electrical method is used to determine the damage depth of the working face bottom plate.

3. The method for evaluating the bearing capacity of a complete floor in pressure mining according to claim 2, characterized in that: The microseismic electrical method specifically comprises the following steps: (a) Determine the location for the microseismic electrical integrated monitoring system; (b) Construction of integrated microseismic electrical monitoring system; (c) Obtain monitoring data from the integrated microseismic electrical monitoring system; (d) Analyze the temporal and spatial distribution of bottom plate microseismic events and monitor the evolution of current and apparent resistivity in bottom plate sections; (e) The damage depth of the working face mining floor is determined by the number of floor microseismic events, energy and density accumulation layers, and the abnormal apparent resistivity area of ​​the monitoring floor section.

4. The method for evaluating the bearing capacity of a complete floor in pressure mining according to claim 1, characterized in that: The sampling depth of the water-bearing rock layer in step (3) is 5-10 meters.

5. The method for evaluating the bearing capacity of a complete floor in pressure mining according to claim 1, characterized in that: When coring in step (3), three groups of samples are taken from the corresponding water-bearing rock layer itself, the overlying rock layer of the aquifer, and the rock samples in the contact zone between the aquifer and the overlying rock layer. The tensile strength values ​​N1, N2, and N3 in step (4) are the average values ​​of the tensile strength values ​​of the three groups of samples.

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