A method for determining the replacement step distance between waste and coal seam in composite coal seam open-pit mines

Abstract

The present invention provides a method for determining the replacement step distance between waste and coal seams in a composite coal seam open-pit mine. First, based on the open-pit coal mine mining design and operating parameters, the width c of the transport flat plate, the width d of the safety flat plate, the step slope angle α, and the step height H are obtained. Then, the physical and mechanical parameters of the slope rock mass are determined. Secondly, based on the two-dimensional rigid body limit equilibrium method, the stability coefficient of the boundary slope is calculated. Finally, the replacement step distance between the waste and each coal seam is determined. The method proposed by the present invention can ensure that the slope stability coefficient of the front and rear end walls before and after the waste and coal seam are replaced remains unchanged, can meet the design specifications and slope safety requirements, has a simple calculation process, and does not require the entire inner spoil yard to be constructed from bottom to top for wall compression. Only local wall compression is required, which can save a large amount of waste; can recover a large amount of residual coal resources at the end walls, maximize resource recovery, and have significant economic benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of open-pit mining, and in particular to a method for determining the replacement step distance between waste and coal seams in a composite coal seam open-pit mine. Background Art

[0002] Due to the constraints of mining boundaries and geological conditions, a large amount of coal resources remain in the end wall of the open-pit mine. The traditional mining method uses deep strong steep wall technology to recover the lowest coal seam. The upper coal seams are directly covered by waste, resulting in a large amount of resources being unable to be mined, which is not in line with the scientific mining development concept. Patent application CN111364999A discloses an integrated replacement method for the end wall pressure coal mining and filling of an open-pit coal mine. The method divides the end wall pressure coal of the open-pit mine into several mining stages of equal length, and divides each stage into front and rear sections. According to the front and rear sections, tunneling and filling operations are alternately performed to complete the replacement of the end wall pressure coal, thereby realizing continuous mining and filling of the end wall pressure coal, and can maximize the extraction of end wall resources. However, tunneling is required, which has problems such as long time cycle, high cost, and difficult construction. Patent application CN 112855162 A discloses a mining method for the upper end wall coal seam of a composite coal seam open-pit mine. The method uses the inner dump step to form an operating space for the arrangement of mining equipment, and uses the inner dump step working plate to perform segmented recovery operations of the upper end wall coal seam pressure resources, and mines the upper coal seam and the interbedded gangue between the coal seam and the mining level together. It also points out that the stage-by-stage recovery length of the end wall coal in the advancement direction is equal to the width of the dump step. Patent application CN Patent application 113742949 B discloses a method for determining the mining width of high-level coal seams in composite coal seam open-pit mines. This method uses a numerical simulation method to exploit the three-dimensional support effect of horizontal mining and internal drainage to mine high-level coal seams. Patent application CN 105178964 A discloses a method for designing the morphology of inclined layered slopes in composite coal seam open-pit mines. This method determines the flat width of the slope at each stage. These patents all study the mining methods and mining width of the upper coal seams in open-pit mines. They do not consider the use of local internal drainage to replace the pressure wall with the coal seam while ensuring the overall safety of the slope, nor do they determine the step distance of the replacement. Therefore, there is an urgent need to find a method for determining the step distance of the replacement of waste and coal seams in composite coal seam open-pit mines to provide technical support for the development of open-pit coal mine stripping and drainage engineering. Summary of the Invention

[0003] In view of the above problems, the present invention provides a method for determining the replacement step distance between waste and coal seams in a composite coal seam open-pit mine, comprising the following steps:

[0004] Step 1: According to the open-pit coal mining design and operation parameters, obtain the transport platform width c, safety platform width d, step slope angle α, and step height H;

[0005] Step 2: Determine the physical and mechanical parameters of the slope rock mass based on previous geological exploration and rock and soil physical and mechanical tests;

[0006] Step 3: Based on the two-dimensional rigid body limit equilibrium method, calculate the stability coefficient Fs1 of the boundary slope;

[0007] Step 4: Number the coal seams in the slope from bottom to top. The bottom coal seam is not numbered because it can achieve steep slopes. The second coal seam is numbered M1, the third coal seam is numbered M2, and so on until the top coal seam is numbered M. i ;

[0008] Step 5: Determine the waste and coal seam M i The permutation step length, where i=1,2,3…n; specifically expressed as:

[0009] Step 5.1: Assume that the coal seam M i The mining width is a, and the coal seam M i The displacement step of the first step at the bottom is b, and the limit value of the displacement step b is cdH / tanα;

[0010] Step 5.2: Use the two-dimensional rigid body limit equilibrium method to calculate the stability coefficient F of the slope after displacement. si-1 ;

[0011] Step 5.3: Compare F si-1 With F s1 , if F si-1 > F s1 When , reduce the waste replacement step b; if F si-1 <F s1 When the replacement step b is greater than or equal to cdH / tanα, the coal seam M is increased. i The second step of the lower step of the waste replacement step b1, if it satisfies | F si-1 -F s1 |<0.005, then the replacement step calculation ends, otherwise continue to increase the coal seam M i The third step of the lower step is replaced by the waste material step b1 until | F si-1 -F s1 |<0.005 no longer increases coal seam M i lower steps;

[0012] Step 6: Let i = 1, 2, 3…n, repeat step 5, and determine the replacement step distance between the waste and each coal seam.

[0013] The beneficial effects of the present invention are:

[0014] 1. The method proposed by the present invention does not require the entire inner dump to be compacted from bottom to top, but only requires local compaction, which can save a lot of waste; it can also recover a large amount of residual coal resources at the end of the dump, maximize resource recovery, and achieve significant economic benefits;

[0015] 2. The method proposed in the present invention can ensure that the slope stability coefficient before and after the replacement of waste and coal seam remains unchanged, can meet the design specifications and slope safety requirements, and has a simple calculation process, simple operation, and easy on-site implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the cross-section of the boundary slope in an embodiment of the present invention;

[0017] Figure 2 Flowchart of a method for determining the replacement step distance between waste and coal seams in a composite coal seam open-pit mine according to an embodiment of the present invention;

[0018] Figure 3 The evaluation result of the boundary slope in the embodiment of the present invention;

[0019] Figure 4 This is a schematic diagram of coal seam numbering and naming in an embodiment of the present invention;

[0020] Figure 5 This is a schematic diagram of calculation results when the mining width of the M1 coal seam is 8m and the replacement step distance is 1.5m in an embodiment of the present invention;

[0021] Figure 6 This is a schematic diagram of calculation results when the mining width of the M1 coal seam is 16m and the replacement step distance is 3.5m in an embodiment of the present invention;

[0022] Figure 7 This is a schematic diagram of the calculation results when the mining width of the M1 coal seam is 24m and the replacement step distance is 5m in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The invention will be further described below with reference to the accompanying drawings and specific implementation examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0024] In this embodiment, a certain open-pit mine is taken as an example. The strata in this mine are: Quaternary, conglomerate, coal, weak interbed, with an average coal seam thickness of 12m and an approximate dip of 0°. From bottom to top, they are: 3 coal, 2 coal, 1 coal. The 3 coal floor is a weak layer, and the mineral composition of the weak layer is mainly illite and montmorillonite, which has the characteristic of severe softening when exposed to water. The cross-sectional morphology of the slope at the boundary is as follows: Figure 1 shown.

[0025] like Figure 2As shown, in this embodiment, a method for determining the replacement step distance between waste and coal seams in a composite coal seam open-pit mine includes the following steps:

[0026] Step 1: According to the open-pit coal mine design and operation parameters, obtain the transport plate width c, safety plate width d, step slope angle α, and step height H.

[0027] Step 2: Based on the results of previous geological exploration and physical and mechanical tests of rock and soil, determine the physical and mechanical parameters of the slope rock mass.

[0028] In this embodiment, according to the preliminary design, the width of the transport platform is 37.5m, the width of the safety platform is 5m, the step slope angle is 70°, and the step height is 12m. Based on the results of previous geological exploration and rock and soil physical and mechanical tests, the rock and soil physical and mechanical parameters are shown in Table 1.

[0029] Table 1 Physical and mechanical parameters of rock and soil

[0030]

[0031] Step 3: Evaluate the stability factor F of the boundary slope based on the two-dimensional rigid body limit equilibrium method s1 .

[0032] In this embodiment, the stability coefficient F of the boundary slope is calculated according to the two-dimensional rigid body limit equilibrium method. s1 =1.200, such as Figure 3 shown.

[0033] Step 4: Number the coal seams in the slope from bottom to top. The bottom coal seam is not numbered because it can achieve steep slopes. The second coal seam is numbered M1, the third coal seam is numbered M2, and so on until the top coal seam is numbered M. n ;

[0034] In this embodiment, the coal seams in the slope body are numbered from bottom to top. The middle coal seam is numbered M1, and the top coal seam is numbered M2. Figure 4 shown.

[0035] Step 5: Determine the waste and coal seam M i The permutation step length, where i=1,2,3…n; specifically expressed as:

[0036] Step 5.1: Assume that the coal seam M i The mining width is a, and the coal seam M i The displacement step of the first step at the bottom is b, and the limit value of the displacement step b is cdH / tanα;

[0037] Step 5.2: Use the two-dimensional rigid body limit equilibrium method to calculate the stability coefficient F of the slope after displacement. si-1 ;

[0038] Step 5.3: Compare F si-1 With F s1 , if F si-1 > F s1 When , reduce the waste replacement step b; if F si-1 <F s1 When the replacement step b is greater than or equal to cdH / tanα, the coal seam M is increased. i The second step of the lower step of the waste replacement step b1, if it satisfies | F si-1 -F s1 |<0.005, then the replacement step calculation ends, otherwise continue to increase the coal seam M i The third step of the lower step is replaced by the waste material step b1 until | F si-1 -F s1 |<0.005 no longer increases coal seam M i lower steps;

[0039] Taking coal seam M1 as an example, compared with F si-1 With F s1 , if F si-1 > F s1 When , reduce the waste replacement step b; if F si-1 <F s1 When the step distance b of waste replacement is greater than cdH / tanα, the step distance b1 of waste replacement at the second step below the coal seam M1 is increased until | F si-1 -F s1 |<0.005.

[0040] When the mining width of coal seam M1 is 8m, 16m, and 24m, the replacement step distance of the first step in the lower part of coal seam M1 is 1.5m, 3.5m, and 5m respectively, and the limit values ​​of the replacement step distance are 10.2m, 13.7m, and 16.2m respectively. The calculation results are as follows: Figure 5 、 6 , as shown in 7.

[0041] Step 6: Let i = 1, 2, 3…n, repeat step 5, and determine the replacement step distance between the waste and each coal seam.

Claims

1. A method for determining the replacement step distance between waste and coal seams in a composite coal seam open-pit mine, characterized in that: include: Step 1: According to the open-pit coal mining design and operation parameters, obtain the transport platform width c, safety platform width d, step slope angle α, and step height H; Step 2: Determine the physical and mechanical parameters of the slope rock mass; Step 3: Based on the two-dimensional rigid body limit equilibrium method, calculate the stability coefficient Fs1 of the boundary slope; Step 4: Number the coal seams in the slope from bottom to top. The bottom coal seam is not numbered because it can achieve steep slopes. The second coal seam is numbered M1, the third coal seam is numbered M2, and so on until the top coal seam is numbered M. i ; Step 5: Determine the waste and coal seam M i The permutation step length, where i=1,2,3…n; Step 5.1: Assume that the coal seam M i The mining width is a, and the coal seam M i The displacement step of the first step at the bottom is b, and the limit value of the displacement step b is cdH / tanα; Step 5.2: Use the two-dimensional rigid body limit equilibrium method to calculate the stability coefficient F of the slope after displacement. si-1 ; Step 5.3: Compare F si-1 With F s1 , if F si-1 > F s1 When , reduce the waste replacement step b; if F si-1 <F s1 When the replacement step b is greater than or equal to cdH / tanα, the coal seam M is increased. i The second step of the lower step of the waste replacement step b1, if it satisfies | F si-1 -F s1 |< , then the replacement step calculation ends, otherwise continue to increase the coal seam M i The third step of the lower step is replaced by the waste material step b1 until | F si-1 -F s1 |< No more coal seam M i Lower steps, is the default value; Step 6: Let i = 1, 2, 3…n, repeat step 5, and determine the replacement step distance between the waste and each coal seam.

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