A method for determining reasonable scale of mining area under thick overburden based on similar simulation

Abstract

The application discloses a method for determining reasonable scale of mining area under thick overburden rock based on similar simulation, which comprises the following steps: determining the thickness and position of the thick overburden rock according to the mine drilling column chart, determining the suitable geometric similarity ratio and laying the two-dimensional similar simulation experiment frame; arranging n simulation working faces in the experiment frame in sequence; arranging stress gauges in the middle of the coal seam from the second working face; excavating each working face in sequence, recording all stress gauge values after each excavation and obtaining the support pressure peak value after each working face excavation; drawing the support pressure peak value under different mining scales into the mining scale-support pressure peak value curve, obtaining the support pressure peak value variation after adjacent two excavations, calculating the support pressure peak value variation rate, and determining the reasonable scale of the mining area under the thick overburden rock according to the support pressure peak value variation rate. In this way, the production capacity of the mining area can be ensured, the development cost can be reduced, and the impact induced by the overburden rock movement due to the too large scale of the mining area can be avoided.

Description

Technical Field

[0001] This invention relates to a method for determining the reasonable scale of mining areas under thick overburden based on similarity simulation, belonging to the field of coal mine safety technology. Background Technology

[0002] Currently, for mines with thick overburden, theoretical calculations are often used to determine the appropriate size of the mining area. However, this method often oversimplifies the mine's geological conditions and cannot accurately determine the appropriate size of the mining area. This can easily lead to situations where the mining area is too large, causing rockbursts induced by the movement of the thick overburden, or too small, resulting in excessive development costs and limited production capacity. Another method is to determine the appropriate size of the mining area based on analogous analysis of mine microseismic monitoring data, but this method is only applicable to mining areas with similar geological conditions and has significant limitations. Therefore, developing a new method for determining the appropriate size of mining areas under thick overburden that can both ensure production capacity and reduce development costs, while avoiding rockbursts induced by overburden movement due to excessively large mining areas, and which also allows for relatively simple data collection and analysis and has good applicability to mining areas with different geological conditions, is one of the research directions in this industry. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a method for determining the reasonable scale of mining areas under thick overburden based on similarity simulation. This method can ensure the production capacity of the mining area and reduce development costs, while avoiding the impact induced by overburden movement due to excessively large mining area scale. At the same time, the collection and analysis of experimental data is relatively simple, and it has good applicability to mining areas with different geological conditions.

[0004] To achieve the above objectives, the technical solution adopted by this invention is: a method for determining the reasonable scale of mining areas under thick overburden based on similarity simulation, the specific steps of which are as follows:

[0005] A. Determine the coal seam thickness, the location and thickness of the overlying strata, and the thickness H of the super-thick overlying strata based on the comprehensive columnar section of the mining area. Then, determine the geometric similarity ratio γ of the model based on the thickness H of the super-thick overlying strata. At the same time, determine the length L of the actual fully mechanized mining face based on the coal seam thickness and the location of the overlying strata, and lay out a two-dimensional similarity simulation test frame.

[0006] B. Starting from a position l away from one side boundary of the experimental frame, n simulated working faces with a dip length of L / γ are arranged sequentially towards the other side boundary. Except for the simulated working face closest to the side boundary of the experimental frame, multiple stress gauges are arranged in the middle of the coal seam of each of the other working faces at intervals d. The reason for not arranging stress gauges in the first simulated working face is that after the first working face is excavated, the peak support pressure appears in the second working face, and so on. After the second working face is excavated, the peak support pressure appears in the third working face. Therefore, it is sufficient to start arranging stress gauges from the second working face.

[0007] C. Starting from the side closest to the test frame and moving towards the other boundary, simulate excavation of each simulated working face in sequence. After each excavation, record the stress count values ​​to obtain the peak support pressure σ after excavation of each working face. Plot the peak support pressure of each time as a mining scale-peak support pressure curve to obtain the change in peak support pressure Δσ after two adjacent excavations. The specific calculation formula is as follows:

[0008]

[0009] Where, σ i Let be the peak value of the working face support pressure after the excavation of the i-th working face, i=2,3,…,n.

[0010] D. Based on the change in peak bearing pressure obtained in step C, calculate the rate of change of peak bearing pressure to determine the reasonable scale of the mining area under the thick overburden. The specific calculation formula is as follows:

[0011]

[0012] Where, Δσ i Let represent the change in peak stress after the excavation of the i-th working face, where i = 3, 4, ..., n.

[0013] The standard for determining the reasonable scale of a mining area under a thick overburden is: if the stress peak change rate α calculated after the excavation of the i-th working face is... i If the stress change is greater than 200%, the reasonable scale of the mining area under the thick overburden is determined to be (i-1)*L. The principle behind this judgment is as follows: The inventors discovered that when simulating the scale of a mining area under thick overburden, only one layer of thick overburden exists. Given a sufficient number of simulated working faces to be excavated, a sudden increase in stress change will inevitably occur, and only one simulated working face will exhibit a stress peak change rate α during excavation. i It is greater than 200%, therefore, based on this characteristic, a unique and reasonable scale can be determined.

[0014] Furthermore, in step B, the distance l is (60~100m) / γ.

[0015] Furthermore, in step B, the number of simulated working surfaces, n, is not less than 4. This ensures that the determined reasonable scale is more accurate after simulation.

[0016] Furthermore, when the coal seam thickness is greater than 3.5m, the dip length L of the fully mechanized mining face is set to 150~240m; when the coal seam thickness is less than 3.5m, the dip length L of the fully mechanized mining face is set to 120~150m; the spacing d of the stress gauges in the simulated working face is 20m / γ. Different dip lengths of the fully mechanized mining face are determined according to different coal thicknesses to ensure the stability of coal seam mining.

[0017] Compared with existing technologies, this invention first determines the thickness H of the thick overburden based on the mine borehole columnar section, then determines the geometric similarity ratio γ of the model and the length L of the actual fully mechanized mining face, and lays out a two-dimensional similarity simulation test frame; then, starting from a distance l from the boundary of the test frame, n simulated working faces are arranged sequentially, and starting from the second working face, stress gauges are arranged sequentially in the middle of the coal seam at intervals d; then, the mining faces are simulated in sequence, and after each excavation, the stress count values ​​are recorded to obtain the peak support pressure σ after excavation of each simulated working face. The peak support pressure of each time is plotted as a mining scale-peak support pressure curve, and the change in peak support pressure Δσ after two adjacent excavations is obtained. Finally, based on the change in peak support pressure, the rate of change of peak support pressure α is calculated, and the reasonable scale of the mining area under the thick overburden is determined according to the magnitude of the rate of change of peak support pressure. This invention can accurately determine the reasonable size of the mining area, thereby reducing the impact risk of the mining face at the design level; avoiding situations where the mining area size determined by empirical methods is too large, leading to rock bursts induced by the movement of thick overburden, or the mining area size is too small, resulting in excessive development costs and limited production capacity. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the borehole column in the mining area according to an embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of the rock strata distribution and working face layout in a similar simulation experiment according to an embodiment of the present invention.

[0020] Figure 3 This is a schematic diagram of the peak value of the mining scale and the support pressure in an embodiment of the present invention. Detailed Implementation

[0021] The present invention will be further described below.

[0022] like Figure 1 As shown, this is a comprehensive columnar section of boreholes in a certain mining area of ​​a certain mine in this embodiment; the average thickness of the coal seam is 20m, and there is a 120m thick sandstone layer 80m above the coal seam, determining the actual length L of the fully mechanized mining face to be 180m; the working face and stress gauge arrangement of the two-dimensional similarity simulation experimental platform are as follows. Figure 2 As shown. The peak bearing pressure curves after excavation of each working face and the reasonable dimensions of the mining area are as follows. Figure 3 As shown. The specific operation steps of this embodiment are as follows:

[0023] A. Based on the comprehensive columnar section of the borehole in the mining area, it was determined that there is a 120m thick sandstone layer 80m above the coal seam. Then, the geometric similarity ratio of the model was determined to be γ=200, and a two-dimensional similarity simulation experimental frame was laid out.

[0024] B. Starting 0.3m from one side boundary of the test frame, arrange six simulated working faces with a dip length of 180m / 200=0.9m in sequence, and number them from 1 to 6 from one side boundary of the test frame to the other side. Then, arrange multiple stress gauges in the middle of the coal seam of each working face numbered 2 to 6 at intervals of 0.1m.

[0025] C. Simulate the excavation of each simulated working face in sequence from number 1 to 6. After each excavation, record the stress count value to obtain the peak support pressure σ after excavation of each simulated working face. Plot the peak support pressure of each time as a mining scale-peak support pressure curve to obtain the change in peak support pressure Δσ after two adjacent excavations. The specific calculation formula is as follows:

[0026]

[0027] Where, σ i Let be the peak value of the working face support pressure after the excavation of the i-th working face, i=2, 3, 4, 5, 6.

[0028] Since the peak support pressure occurred in working face 2 after excavation of working face 1, and similarly, the peak support pressure occurred in working face 3 after excavation of working face 2. Figure 2 Calculations show that after the second working face is excavated, the peak change in support pressure between it and the first working face is 29.6 N (i.e., 51.2 - 21.6 = 29.6). After the third working face is excavated, the peak change in support pressure is 31.5 N. After the fourth working face is excavated, the peak change in support pressure is 127.8 N. After the fifth working face is excavated, the peak change in support pressure is 140.8 N.

[0029] D. Based on the change in peak bearing pressure obtained in step C, calculate the rate of change of peak bearing pressure to determine the reasonable scale of the mining area under the thick overburden. The specific calculation formula is as follows:

[0030]

[0031] Where, Δσ i Let represent the change in peak stress after excavation of the i-th working face, where i = 3, 4, 5, 6.

[0032] The standard for determining the reasonable scale of a mining area under a thick overburden is: if the calculated rate of change of peak stress α after the excavation of the i-th working face is... iIf the change is greater than 200%, then the reasonable size of the stope under the key layer of thick overburden should be (i-1)*L. In this embodiment, after the third working face is excavated, the peak change rate of the support pressure is 6.41%, and after the fourth working face is excavated, the peak change rate of the support pressure is 300.57%, which is greater than 200%. Therefore, the reasonable size of the stope under this mine condition is (4-1)×180m=540m.

[0033] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for determining the reasonable scale of a mining area under a thick overburden based on similarity simulation, characterized in that, The specific steps are as follows: A. Determine the coal seam thickness, the location and thickness of the overlying strata, and the thickness H of the super-thick overlying strata based on the comprehensive columnar section of the borehole in the mining area. Then, determine the geometric similarity ratio γ of the model based on the thickness H of the super-thick overlying strata. At the same time, determine the length L of the actual fully mechanized mining face based on the coal seam thickness and the location of the overlying strata, and lay out a two-dimensional similarity simulation test frame. B. Starting from a position l away from one side boundary of the test frame, n simulated working faces with a dip length of L / γ are arranged sequentially towards the other side boundary. In addition to the simulated working face closest to the side boundary of the test frame, multiple stress gauges are arranged in the middle of the coal seam of each of the other working faces at a spacing of d. C. Starting from the side closest to the test frame and moving towards the other boundary, simulate excavation of each simulated working face in sequence. After each excavation, record the stress count values ​​to obtain the peak support pressure σ after excavation of each working face. Plot the peak support pressure of each time as a mining scale-peak support pressure curve to obtain the change in peak support pressure Δσ after two adjacent excavations. The specific calculation formula is as follows: Board i =s i -s i-1 Where, σ i The peak value of the working face support pressure after the excavation of the i-th working face, i = 2, 3, ..., n; D. Based on the change in peak bearing pressure obtained in step C, calculate the rate of change of peak bearing pressure to determine the reasonable scale of the mining area under the thick overburden. The specific calculation formula is as follows: Where, Δσ i Let represent the change in peak stress after excavation of the i-th working face, where i = 3, 4, ..., n; The standard for determining the reasonable scale of a mining area under a thick overburden is: if the stress peak change rate α calculated after the excavation of the i-th working face is... i If the percentage is greater than 200%, then the reasonable size of the mining area under the thick overburden is determined to be (i-1)*L.

2. The method for determining the reasonable scale of mining areas under thick overburden based on similarity simulation according to claim 1, characterized in that, In step B, the distance l is (60-100m) / γ.

3. The method for determining the reasonable scale of mining areas under thick overburden based on similarity simulation according to claim 1, characterized in that, In step B, the number of simulated working surfaces n is not less than 4.

4. The method for determining the reasonable scale of mining areas under thick overburden based on similarity simulation according to claim 1, characterized in that, When the coal seam thickness is greater than 3.5m, the dip length L of the fully mechanized mining face is set to 150-240m; when the coal seam thickness is less than 3.5m, the dip length L of the fully mechanized mining face is set to 120-150m; the arrangement spacing d of the stress gauges in the simulated working face is 20m / γ.

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