A method for determining filling parameters for goaf intervals based on high-water materials

Abstract

This invention discloses a method for determining the interval filling parameters of goaf based on high-water-content materials. First, the height of the pressure arch generated by mining in the current coal seam is calculated, and two cases can be distinguished based on the position of the arch crown. Then, for each case, specific data and screening methods are used to select multiple preliminary schemes. Simultaneously, multiple high-water-content materials with different water-cement ratios are selected as preliminary water-cement ratios. Next, each preliminary scheme is matched with each preliminary water-cement ratio to select a suitable preliminary water-cement ratio for each scheme. After completion, the filling cost per meter of filling for each preliminary scheme is calculated. For each case, the water-cement ratio suitable for the preliminary scheme with the lowest cost is selected as the chosen filling parameter for each case. Finally, the selected filling parameters are verified through simulation experiments to ultimately determine the optimal interval filling parameters for different situations within the mining area, thereby ensuring the support effect of interval filling.

Description

Technical Field

[0001] This invention relates to a method for filling goaf areas with high-water-content materials, specifically a method for determining the interval filling parameters of goaf areas based on high-water-content materials, belonging to the field of coal mine goaf support technology. Background Technology

[0002] Currently, in coal mining, backfilling can reduce surface subsidence above coal-bearing areas and minimize damage to surface buildings and structures, achieving green and efficient coal resource mining. Backfilling under protective coal pillars is one of the main development directions in the mining industry. High-moisture materials have advantages such as low transport resistance, rapid solidification, and high strength, and are gradually being promoted in backfilling mining. However, due to the generally high cost and slow speed of backfilling, it not only increases mining costs and affects mining progress but also restricts the widespread adoption of backfilling mining. Currently, with the introduction of intermittent backfilling mining technology, the industry has effectively reduced backfilling costs and increased backfilling speed. However, the specific construction parameters in existing intermittent backfilling mining processes are all determined based on the experience of construction personnel. This method lacks a scientific and standardized process for determining intermittent backfilling parameters, relying solely on experience. Consequently, in some mining areas, the strength of the backfill body does not match the required backfilling conditions of the goaf, resulting in poor intermittent backfilling support and necessitating re-support. Therefore, providing a method that can scientifically and standardizedly determine the optimal intermittent backfilling parameters for different situations in mining areas through multiple screening and matching processes and simulation tests, thereby achieving a match between the strength of the backfill body and the required backfilling conditions of the goaf and ensuring the support effect of intermittent backfilling, 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 interval filling parameters of goaf based on high-water-content materials. This method can scientifically and standardly determine the optimal interval filling parameters for different situations in the mining area through various screening and matching processes and simulation tests, thereby achieving a match between the strength of the filling body and the required filling conditions of the goaf and ensuring the support effect of the interval filling.

[0004] To achieve the above objectives, the technical solution adopted by this invention is: a method for determining the filling parameters of goaf intervals based on high-water-content materials, the specific steps of which are as follows:

[0005] A. First, determine the coal seam depth of the current mining area. Using the formula P = γh, where P is the overburden load (MPa) and γ is the unit weight of the rock strata (N / m³). 3 h - Coal seam burial depth, m, calculate the load acting above the coal seam; then determine the mining width W and height M of the working face;

[0006] B. Based on the working face parameters determined in step A, calculate the height of the pressure arch generated by mining. The formula is as follows:

[0007]

[0008] In the formula, H is the height of the pressure arch, in meters (m). denoted as θ = 0.5°; W is the mining width of the working face (which becomes the width of the goaf after mining), m; M is the mining height of the working face (which becomes the height of the goaf after mining), m; f is the Protodyakonov coefficient, taken as 0.5°. R c The uniaxial compressive strength of the rock is given in MPa.

[0009] Based on the calculated height of the pressure arch, if the crown of the pressure arch exceeds the surface of the current mining area, the filling body is required to bear the weight of the entire overburden above it; if the crown of the pressure arch does not exceed the surface of the current mining area, the filling body is required to bear the weight of the overburden between its upper surface and the crown.

[0010] C. Using a two-factor, three-level orthogonal test table, the width and spacing of the filling body are set as two factors, and 3m, 4.5m, and 6m are set as three levels. Based on the two cases divided into two categories according to the position of the pressure arch crown in step B, the load of the overburden acting on the filling body under different factor levels in the two cases is calculated. Then, from the results of each case, the schemes in which the filling body load does not exceed 8MPa are selected. If the filling body load corresponding to all schemes in each case does not exceed 8MPa, then the filling spacing is increased by 3m at each level, the three-level values ​​of the filling body width are kept unchanged, and the orthogonal test is carried out again until the filling body load of at least one scheme in the results of each case exceeds 8MPa. Then, the remaining schemes in each case that do not exceed 8MPa are taken as multiple preliminary schemes for each case.

[0011] D. Prepare high water-cement material slurries with different water-cement ratios and pour them into standard molds for curing. After curing, test the uniaxial compressive strength of high water-cement material specimens with different water-cement ratios using a pressure tester. Take each water-cement ratio with a uniaxial compressive strength greater than 2MPa as multiple initial water-cement ratios.

[0012] E. In step D, multiple preliminary water-cement ratios are determined and specimens are prepared. Then, the uniaxial compressive strength of each specimen is compared with the filling load corresponding to the multiple preliminary schemes determined in step C for each case. The preliminary water-cement ratio applicable to each preliminary scheme in each case is selected. Specifically, the process of selecting the preliminary water-cement ratio for each preliminary scheme is as follows: First, the filling load of a preliminary scheme is determined. Then, the uniaxial compressive strength corresponding to each preliminary water-cement ratio is compared with the filling load. The preliminary water-cement ratio that exceeds the filling load by the smallest amount is selected as the preliminary water-cement ratio applicable to the current preliminary scheme.

[0013] Then, the total width of the filling body required for each preliminary scheme in each case along the working face dip is calculated. Next, the weight of filling material required per cubic meter of filling body for each preliminary scheme with the applicable water-cement ratio is calculated. Finally, the filling cost Y per 1m of filling along the working face dip for different preliminary schemes with the applicable water-cement ratio is calculated.

[0014] Y = l 总 Mmy

[0015] In the formula, l 总 y represents the total width of the filling body, in meters; m represents the weight of material per cubic meter, in tons; y represents the unit price of the filling material, in yuan per ton.

[0016] Compare the filling cost per 1m of each preliminary selection scheme in each case, and select the preliminary selection scheme with the lowest cost and its applicable water-cement ratio in each case as the filling parameter selected for each case.

[0017] F. Based on the filling parameters selected in step E, the water-cement ratio in the filling parameters is selected according to the experimental data of the uniaxial compressive strength of the water-cement ratio specimen corresponding to the water-cement ratio in step D. The strain softening constitutive model parameters are corrected in FLAC3D software using the selected experimental data. The corrected parameters are used as the parameters of the filling body in the simulation test. Then, the FLAC3D software is used to carry out the goaf interval filling simulation test and monitor the settlement of each filling body in the simulation test.

[0018] G. Calculate the surface subsidence value by monitoring the maximum subsidence of the filling body. If the calculated surface subsidence value meets the settlement requirements of the protected object, the parameters are determined, and the filling parameters selected in step E are used as the final interval filling parameters. If the surface subsidence value does not meet the settlement requirements of the protected object, the second lowest cost preliminary scheme and its applicable water-cement ratio are selected as the filling parameters in step E, and steps F and G are repeated, and so on, until the surface subsidence value meets the settlement requirements of the protected object. Then the parameters are determined, and the filling width, filling spacing and water-cement ratio of the high-water material in the current preliminary scheme are used as the final interval filling parameters.

[0019] Furthermore, the formula for calculating the load in step C is as follows:

[0020]

[0021] In the formula, l2 is the width of the filling body, m; l1 is the filling spacing, m; h is the coal seam burial depth, m; and γ is the rock stratum unit weight.

[0022] Furthermore, the different water-cement ratios prepared in step D are 1:1, 1.5:1, 2:1...7.5:1, and 8:1.

[0023] Furthermore, the dimensions of the standard trial mold in step D are:

[0024] Furthermore, the formula for calculating the surface subsidence value W in step G is as follows:

[0025]

[0026] In the formula, δ is the approach distance of the top and bottom plates before filling, in mm; η is the compression ratio of the filling material; q 充 Roof subsidence coefficient when the goaf is fully filled; α is the coal seam dip angle, r is the main influence radius; q 条 y is the roof subsidence coefficient during strip mining; x and y are the coordinates of the filling location.

[0027] Compared with existing technologies, this invention first calculates the load above the coal seam based on the coal seam burial depth and determines the mining width and height of the working face at the start of coal seam mining; then it can calculate the pressure arch height generated by the current coal seam mining, compare the pressure arch height with the coal seam depth, and divide it into two cases based on the position of the pressure arch crown; then, for each case, specific data and screening methods are used to select multiple preliminary schemes for each case; simultaneously, multiple high water-cement ratio materials with different water-cement ratios are screened as preliminary water-cement ratios, and then each preliminary scheme is matched with each preliminary water-cement ratio to select a preliminary water-cement ratio suitable for each preliminary scheme. After completion, the calculation is performed. The cost of filling 1m of material in each preliminary selection scheme is calculated. For each case, the water-cement ratio applicable to the preliminary selection scheme with the lowest cost is selected as the filling parameter for each case. Finally, the selected filling parameters are input into FLAC3D software for simulation testing. The simulation test determines the maximum settlement of the filling body with the current filling parameters, and then calculates the surface settlement value. If the surface settlement value meets the requirements, the filling parameter is finally determined as the final interval filling parameter. If the surface settlement value does not meet the requirements, the preliminary selection scheme with the second lowest cost is selected and simulation tests are conducted again until the requirements are met, and the current filling parameter is then used as the final interval filling parameter. Through the above process, it can be seen that this invention can, according to the specific conditions of different mining areas, first divide into two cases, and each case is verified through multiple screening and matching processes and simulation tests. Finally, it scientifically and standardly determines the optimal interval filling parameters for different cases within the mining area, thereby achieving a match between the strength of the filling body and the filling conditions required by the goaf, ensuring the support effect of interval filling. Attached Figure Description

[0028] Figure 1 This is a schematic diagram illustrating the situation in this invention where the filling body needs to bear the weight of the entire overburden.

[0029] Figure 2 This is a schematic diagram illustrating the situation in which the filling body in this invention needs to bear the weight of the overburden between its upper surface and the arch.

[0030] Figure 3 This is a schematic diagram of the load calculation for the filling material in this invention. Detailed Implementation

[0031] The present invention will be further described below.

[0032] The specific steps of this invention are as follows:

[0033] A. First, determine the coal seam depth of the current mining area. Using the formula P = γh, where P is the overburden load (MPa) and γ is the unit weight of the rock strata (N / m³). 3 h - Coal seam burial depth, m, calculate the load acting above the coal seam; then determine the mining width W and height M of the working face;

[0034] B. Based on the working face parameters determined in step A, calculate the height of the pressure arch generated by mining. The formula is as follows:

[0035]

[0036] In the formula, H is the height of the pressure arch, in meters (m). denoted as θ = 0.5°; W is the mining width of the working face, m; M is the mining height of the working face, m; f is the Protodyakonov coefficient, taken as 0.5°. R c The uniaxial compressive strength of the rock is given in MPa.

[0037] Based on the calculated pressure arch height, such as Figure 1 As shown, if the crown of the pressure arch exceeds the surface of the current mining area, then the infill must bear the weight of the entire overburden above; if... Figure 2 As shown, if the crown of the pressure arch does not exceed the surface of the current mining area, then the filling body is required to bear the weight of the overburden between its upper surface and the crown.

[0038] C. Using a two-factor, three-level orthogonal experimental design, the filling width and spacing are set as two factors, and 3m, 4.5m, and 6m are set as three levels. Based on the two cases determined by the position of the pressure arch crown in step B, such as... Figure 3 As shown, the loads exerted on the infill by the overburden under different factor levels in two cases are calculated. The formulas for calculating the loads are as follows:

[0039]

[0040] In the formula, l2 is the width of the filling body, m; l1 is the filling spacing, m; h is the coal seam burial depth, m; and γ is the rock stratum unit weight.

[0041] Next, select the schemes whose filling load does not exceed 8MPa from the results of each case. If the filling load corresponding to all schemes in each case does not exceed 8MPa, then increase the filling spacing by 3m at each level, keep the three levels of filling width unchanged, and conduct orthogonal test again until the filling load of at least one scheme in the results of each case exceeds 8MPa. Then, take the remaining schemes that do not exceed 8MPa as multiple preliminary schemes for each case.

[0042] D. Prepare high-water-cement slurries with water-cement ratios of 1:1, 1.5:1, 2:1...7.5:1, and 8:1 respectively, and pour them into containers with dimensions of... Curing was performed in a standard mold. After curing, the uniaxial compressive strength of high-water-cement material specimens with different water-cement ratios was tested by a pressure machine. Each water-cement ratio with a uniaxial compressive strength greater than 2MPa was selected as a number of initial water-cement ratios. Furthermore, the strength of high-water-cement materials decreased as the water-cement ratio increased.

[0043] E. In step D, multiple preliminary water-cement ratios are determined and specimens are prepared. Then, the uniaxial compressive strength of each specimen is compared with the filling load corresponding to the multiple preliminary schemes determined in step C for each case. The preliminary water-cement ratio applicable to each preliminary scheme in each case is selected. Specifically, the process of selecting the preliminary water-cement ratio for each preliminary scheme is as follows: First, the filling load of a preliminary scheme is determined. Then, the uniaxial compressive strength corresponding to each preliminary water-cement ratio is compared with the filling load. The preliminary water-cement ratio that exceeds the filling load by the smallest amount is selected as the preliminary water-cement ratio applicable to the current preliminary scheme.

[0044] Then, the total width of the filling body required for each preliminary scheme in each case along the working face dip is calculated. Next, the weight of filling material required per cubic meter of filling body for each preliminary scheme with the applicable water-cement ratio is calculated. Finally, the filling cost Y per 1m of filling along the working face dip for different preliminary schemes with the applicable water-cement ratio is calculated.

[0045] Y = l 总 Mmy

[0046] In the formula, l 总 y represents the total width of the filling body, in meters; m represents the weight of material per cubic meter, in tons; y represents the unit price of the filling material, in yuan per ton.

[0047] Compare the filling cost per 1m of each preliminary selection scheme in each case, and select the preliminary selection scheme with the lowest cost and its applicable water-cement ratio in each case as the filling parameter selected for each case.

[0048] F. Based on the filling parameters selected in step E, the water-cement ratio in the filling parameters is selected according to the experimental data of the uniaxial compressive strength of the water-cement ratio specimen corresponding to the water-cement ratio in step D. The strain softening constitutive model parameters are corrected in FLAC3D software using the selected experimental data. The corrected parameters are used as the parameters of the filling body in the simulation test. Then, the FLAC3D software is used to carry out the goaf interval filling simulation test and monitor the settlement of each filling body in the simulation test.

[0049] G. Calculate the surface subsidence value by measuring the maximum subsidence of the monitored infill body. The specific calculation formula is as follows:

[0050]

[0051] In the formula, δ is the approach distance of the top and bottom plates before filling, in mm; η is the compression ratio of the filling material; q 充 Roof subsidence coefficient when the goaf is fully filled; α is the coal seam dip angle, r is the main influence radius; q 条 y is the roof subsidence coefficient during strip mining; x and y are the coordinates of the filling location.

[0052] If the calculated surface subsidence value meets the settlement requirements of the protected object (i.e., the industry-known surface subsidence requirements), then the parameters are determined, and the filling parameters selected in step E are used as the final interval filling parameters. If the surface subsidence value does not meet the settlement requirements of the protected object, then the second lowest cost preliminary scheme and its applicable water-cement ratio are selected as the filling parameters in step E, and steps F and G are repeated, and so on, until the surface subsidence value meets the settlement requirements of the protected object. Then the parameters are determined, and the filling width, filling spacing, and water-cement ratio of the high-water material in the current preliminary scheme are used as the final interval filling parameters.

[0053] 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 goaf interval filling parameters based on high water material, characterized in that, The specific steps are as follows: A、First determine the current coal seam depth, according to the formula P = γh, where P - overburden load, MPa, γ - rock bulk density, N / m 3 h - coal seam depth, m, to calculate the load on the coal seam above; second, determine the working face mining width W and height M; B. According to the working face parameters determined in step A, the pressure arch height generated by mining is calculated, and the formula is: In the formula, H is the pressure arch height, m; is the internal friction angle of rock, °; W is the mining width of the working face, m; M is the mining height of the working face, m; and f is the Proctor coefficient. According to the pressure arch height obtained by calculation, if the pressure arch crown exceeds the current mine surface, it is determined that the filling body needs to bear the weight of all overburden above; if the pressure arch crown does not exceed the current mine surface, it is determined that the filling body needs to bear the weight of the overburden between the surface above and the arch crown; C. Using a two-factor three-level orthogonal test table, the filling body width and filling spacing are set as two factors, 3m, 4.5m, and 6m are set as three levels. According to the two cases divided by the position of the pressure arch crown in step B, the load of the overburden acting on the filling body under different factor levels in two cases is calculated. Then, from the results of each case, select the schemes in which the filling body load does not exceed 8MPa. If the load of the filling body corresponding to all schemes in each case does not exceed 8MPa, increase the filling spacing by 3m for each level, keep the three level values of the filling body width unchanged, and perform the orthogonal test again. Until the filling body load of at least one scheme in each case exceeds 8MPa, then the remaining schemes in each case that do not exceed are selected as multiple preliminary schemes for each case; D. Prepare high-water material slurry with different water-cement ratios, and pour it into standard test molds for curing. After curing, test the uniaxial compressive strength of the high-water material test pieces with different water-cement ratios using a pressure machine. Select the water-cement ratios with uniaxial compressive strength greater than 2MPa as multiple preliminary water-cement ratios; E. Prepare test pieces with the multiple preliminary water-cement ratios determined in step D. Then compare the uniaxial compressive strength of each test piece with the filling body load corresponding to the multiple preliminary schemes determined in step C for each case. Select the preliminary water-cement ratio applicable to each preliminary scheme in each case; Then calculate the total filling body width required for each preliminary scheme in each case along the working face trend. Then calculate the filling material weight required per cubic meter of filling body for the preliminary water-cement ratio applicable to each preliminary scheme in each case. Finally, calculate the filling cost Y per 1m of filling along the working face trend for the preliminary water-cement ratio applicable to different preliminary schemes: Y = 1 总 Mmy wherein l 总 is the sum of the filler widths, m; m is the weight of each cubic meter of material, t; y is the unit price of filling material, yuan / ton; Compare the filling cost per 1m of each preliminary scheme in each case. In each case, select the preliminary scheme with the lowest cost and its applicable water-cement ratio as the selected filling parameters for each case; F. According to the filling parameters selected in step E, and select the water-cement ratio according to the experimental data of the water-cement ratio test piece uniaxial compressive strength corresponding to the water-cement ratio in step D. In the FLAC3D software, use the selected experimental data to correct the strain softening constitutive model parameters. The corrected parameters are used as the parameters of the filling body in the simulation test. Then the FLAC3D software performs interval filling simulation test in the goaf, and monitors the subsidence of each filling body in the simulation test; G. Calculate the surface subsidence value from the maximum subsidence of the filling body. If the calculated surface subsidence value meets the settlement requirements of the protected object, the parameters are determined. If the ground subsidence value does not meet the subsidence requirement of the protected object, in step E, the second-lowest cost initial scheme and its applicable water-cement ratio are selected as the selected filling parameters, and steps F and G are repeated, and so on, until the ground subsidence value meets the subsidence requirement of the protected object, and then the filling width, filling interval and water-cement ratio of the high-water material in the current initial scheme are taken as the final interval filling parameters.

2. The high-water-material-based goaf interval filling parameter determination method according to claim 1, characterized in that, The calculation formula of the load in step C is as follows: In the formula, l2 is the filling body width, m; l1 is the filling interval, m; h is the coal seam buried depth, m; and γ is the rock stratum unit weight.

3. The high-water-material-based goaf interval filling parameter determination method according to claim 1, characterized in that, The different water-cement ratios prepared in step D are 1:1, 1.5:1, 2:1, 7.5:1 and 8:

1.

4. The high-water-material-based goaf interval filling parameter determination method according to claim 1, characterized in that, The dimensions of the standard test bar in step D are 5. The high-water-material-based goaf interval filling parameter determination method according to claim 1, characterized in that, The calculation formula of the ground subsidence value W in step G is as follows: where δ is the roof and floor convergence before filling; c is the compression ratio of the filling body; q 充 is the roof convergence coefficient when the goaf is fully filled; α is the coal seam dip angle, r is the main influence radius; q 条 is the roof convergence coefficient when strip mining; x, y are the coordinates of the filling.

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