Method for analyzing influence of hard roof movement on mine pressure and gas emission rule

Abstract

The invention relates to the technical field of mine pressure appearance analysis, and discloses a method for analyzing the influence of hard roof movement on mine pressure and gas emission laws, which comprises the following steps of: establishing a numerical simulation geometric model of coal seam fully mechanized caving mining by utilizing FLAC3D finite element software, and adopting the same rock mechanical parameters for rock stratums in the geometric model; analyzing and obtaining an influence rule of the compressive strength, the layer position, the thickness and the mining height of the hard roof on the mine pressure appearance; according to the method for analyzing the influence of the movement of the hard roof on the mine pressure and the gas emission rule, a numerical simulation geometric model of coal seam fully mechanized caving mining is established by utilizing FLAC3D finite element software, and the influence of the change of the compressive strength, the layer position, the thickness and the mining height of the high-position hard roof on large-space stope mine pressure display is obtained through a simulation experiment; therefore, the rule of the influence of the compressive strength, the layer position, the thickness and the mining height of the high-position hard roof on large-space stope mine pressure appearance can be conveniently researched.

Description

Technical Field

[0001] The invention relates to the technical field of mine pressure manifestation analysis, and in particular to a method for analyzing the influence of hard roof movement on mine pressure and gas emission rules. Background Art

[0002] The geological conditions of coal seams in China's coal mines are particularly complex. Nearly half of the coal seams in the mining areas are covered by hard roofs that are difficult to collapse. Most of the mining areas that are key national construction projects have such conditions. Mine pressure manifestation refers to the deformation and displacement of the surrounding rock strata caused by the mining of coal seams during the coal mining process, which in turn causes changes in ground pressure. The hardness, structure, movement characteristics of the roof, and the mining method of the mine will affect the manifestation of mine pressure. When the hard roof is displaced or broken, this sudden movement may cause a sharp change in mine pressure, endangering the safety of equipment and personnel. The movement of the roof will produce stress concentration areas around the goaf, which may cause local collapse. In addition, it may also cause mine roof collapse. The drastic changes in mine pressure manifestation will cause a large amount of abnormal gas to gush out instantly from other areas such as the working face, increasing the safety risks of mine operations.

[0003] Previous studies on the effect of hard roof on the manifestation of mine pressure mainly focused on the impact of the breaking and instability of low-level single-layer hard roof on mine pressure. However, due to the effective improvement of coal mining technology in recent years, the technology of large-scale high-mine mining has been gradually advanced and matured, and scholars generally recognize that the breaking and instability of multi-layer hard roof will also affect the manifestation of mine pressure. However, existing studies have not yet considered the impact of the occurrence state of high-level hard roof on the manifestation of mine pressure. Summary of the invention

[0004] In order to solve the problem that the above existing studies do not consider the influence of the occurrence state of high-level hard roof on the manifestation of mine pressure in the influence of hard roof on the manifestation of mine pressure, the present invention is implemented through the following technical scheme: a method for analyzing the influence of hard roof movement on mine pressure and gas emission law, including the following methods:

[0005] The numerical simulation geometric model of coal seam fully mechanized caving mining is established by using FLAC3D finite element software, and the rock strata in the geometric model all adopt the same rock mechanics parameters;

[0006] Analyze and obtain the influence of the compressive strength, layer position, thickness and mining height of the hard roof on the manifestation of mine pressure;

[0007] Based on the "OX" breaking mechanism of the hard roof, the change of the goaf volume before and after the hard roof breaks is analyzed, and a calculation model for the increase in gas outburst in the goaf during the periodic pressure is established;

[0008] Based on the on-site fully mechanized caving working face monitoring results, verify whether the calculation model of the increase in gas outburst in the goaf during the period of pressure increase is accurate.

[0009] Furthermore, the influence of the compressive strength of hard roof at different heights on the mine pressure is analyzed, specifically:

[0010] In the simulation experiment of the geometric model, the mining height, layer position and thickness parameters are controlled to remain unchanged, and the compressive strength is changed from low to high;

[0011] As the compressive strength of the hard roof changes, the changes in the height and angle of the collapse zone are analyzed, and then the deformation influence of the overburden displacement field is analyzed; the changes in the influence range of the advance support stress of the working face are analyzed; the mean value of the peak value of the advance support stress of the working face, the forward displacement of the peak influence area, and the changes in the stress concentration area are analyzed;

[0012] Analyze the release characteristics of rock energy under different hard roof compressive strengths.

[0013] Furthermore, the influence of different high-level hard roof layers on the mining pressure manifestation in the mining area is analyzed, specifically:

[0014] In the simulation experiment of the geometric model, the mining height, compressive strength and thickness parameters are controlled to remain unchanged, and the layers are changed from low to high.

[0015] With the change of the hard roof layer, the change of the collapse zone height and collapse angle is analyzed, and then the deformation influence of the overburden displacement field is analyzed; the change of the influence range of the working face advance support stress is analyzed; the change of the mean value of the working face advance support stress peak, the forward displacement of the peak influence area and the stress concentration area is analyzed;

[0016] Analyze the energy release characteristics of rock strata under different hard roof layers.

[0017] Furthermore, the influence of different high-level hard roof thicknesses on the mining pressure in the mining area is analyzed, specifically:

[0018] In the simulation experiment of the geometric model, the mining height, layer position and compressive strength parameters are controlled to remain unchanged, and the thickness is increased in sequence;

[0019] As the thickness of the hard roof changes, the changes in the height and angle of the collapse zone are analyzed, and then the deformation influence of the overburden displacement field is analyzed; the changes in the influence range of the advance support stress of the working face are analyzed; the changes in the mean value of the peak value of the advance support stress of the working face, the forward displacement of the peak influence area, and the stress concentration area are analyzed;

[0020] Analyze the release characteristics of rock energy under different hard roof thicknesses.

[0021] Furthermore, the influence of different high-level hard roof mining heights on the mining pressure in the mining area is analyzed, specifically:

[0022] In the simulation experiment of the geometric model, the thickness, layer position and compressive strength parameters are controlled to remain unchanged, and the mining height is changed from low to high;

[0023] As the mining height of the hard roof changes, the changes in the height and angle of the collapse zone are analyzed, and then the deformation influence of the overburden displacement field is analyzed; the changes in the influence range of the advanced support stress of the working face are analyzed; the changes in the mean value of the peak value of the advanced support stress of the working face, the forward displacement of the peak influence area, and the stress concentration area are analyzed;

[0024] Analyze the energy release characteristics of rock strata under different hard roof mining heights.

[0025] Furthermore, based on the hard roof "OX" breaking mechanism, a calculation model for the increase in gas outburst in the goaf during the periodic pressure is established, specifically:

[0026] The shape of the goaf after the hard roof is broken is simplified to a quadrangular prism with a right-angled trapezoidal cross section;

[0027] Calculate the change in the volume of the goaf space before and after the hard roof collapses, and then estimate the increase in gas outburst in the goaf:

[0028]

[0029] Among them, Q is the increase of gas outburst in the goaf, C is the average gas concentration in the goaf, ΔV is the change of the spatial volume of the goaf before and after the hard roof collapses, L1 and L2 are the short and long sides of the hard roof, m1 is the coal mining thickness, m2 is the coal caving thickness, m3 is the thickness of the soft rock layer below the hard roof, α is the final inclination angle of the broken block, and K p is the expansion coefficient of the remaining coal and gangue under the hard roof, t2 is the duration of the cycle pressure, and γ is the air leakage rate.

[0030] Furthermore, it is verified whether the calculation model of the increase in gas outburst in the goaf during the periodic pressure is accurate, specifically:

[0031] According to the field measured data of the fully mechanized caving working face, the gas outflow volume of the working face and the gas outflow volume of the goaf before and after the periodic pressure when the working face experiences several periodic pressures accompanied by the rotation and breaking of the hard roof of the goaf are obtained;

[0032] Calculate whether the error between the actual increase in gas outflow from the goaf after the periodic pressure increase and the theoretical increase in gas outflow obtained by the calculation model for the increase in gas outflow from the goaf during the periodic pressure increase is within a set range.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The analysis method of the influence of hard roof movement on mine pressure and gas emission law is to establish a numerical simulation geometric model of coal seam fully mechanized caving mining by using FLAC3D finite element software, and obtain the influence of changes in high-position hard roof compressive strength, layer, thickness and mining height on the mine pressure manifestation in a large space mine through simulation experiments, so as to facilitate the study of the influence of high-position hard roof compressive strength, layer, thickness and mining height on the mine pressure manifestation in a large space mine; by using the change in the volume of the goaf after the hard roof breaks and rotates, a calculation model for the increase in gas emission in the goaf during the periodic pressure is established, so as to study and obtain the law of gas emission, and then quantify the increase in gas emission in the goaf during the periodic pressure. This method makes up for the shortcomings of the current research on the influence of the occurrence state of high-position hard roof on mine pressure manifestation and the influence of hard roof movement on gas emission, has strong feasibility, and is suitable for the study of strong mine pressure manifestation in large space mines. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic diagram of a geometric model in an embodiment of the present invention;

[0036] Figure 2 is a spatial distribution diagram of the displacement field of overburden rock under different compressive strengths in an embodiment of the present invention;

[0037] Figure 3 It is a cloud diagram of vertical stress field distribution of overburden rock under different compressive strengths in the embodiment of the present invention;

[0038] Figure 4 : is a peak evolution diagram of the advanced support stress of the working face under different compressive strengths in an embodiment of the present invention;

[0039] Figure 5 Schematic diagram of energy release of all rock formations breaking and instability under different compressive strengths in an embodiment of the present invention;

[0040] Figure 6 : is a spatial distribution diagram of the displacement field of the overburden rock at different layers in the embodiment of the present invention;

[0041] Figure 7 It is a cloud diagram of vertical stress field distribution of overburden in different layers in the embodiment of the present invention;

[0042] Figure 8 : is a peak evolution diagram of the advanced support stress of the working face at different layers in the embodiment of the present invention;

[0043] Fig. 9 Schematic diagram of energy release of all rock strata breaking and instability at different layers in an embodiment of the present invention;

[0044] Fig.10 : is a spatial distribution diagram of the displacement field of overburden rock at different thicknesses in an embodiment of the present invention;

[0045] Fig.11It is a cloud diagram of vertical stress field distribution of overburden with different thicknesses in the embodiment of the present invention;

[0046] Fig.12 1 is a peak evolution diagram of the advanced support stress of the working surface at different thicknesses in an embodiment of the present invention;

[0047] Fig.13 Schematic diagram of energy release of all rock layers breaking and instability at different thicknesses in an embodiment of the present invention;

[0048] Fig.14 It is a spatial distribution diagram of the displacement field of the overburden rock at different mining heights in the embodiment of the present invention;

[0049] Fig.15 It is a cloud diagram of vertical stress field distribution of overburden strata at different mining heights in the embodiment of the present invention;

[0050] Fig.16 This is a peak evolution diagram of the advanced support stress of the working face at different mining heights in an embodiment of the present invention;

[0051] Fig.17 Schematic diagram of energy release of all rock strata breaking and instability at different mining heights in an embodiment of the present invention;

[0052] Fig.18 This is a simplified model diagram of the goaf area before the hard roof breaks in an embodiment of the present invention;

[0053] Fig.19 This is a simplified model diagram of the goaf area after the hard roof is broken in the embodiment of the present invention;

[0054] Fig. 20 Schematic diagram of the relationship between support resistance and gas outflow from the working face in an embodiment of the present invention. DETAILED DESCRIPTION

[0055] 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.

[0056] The embodiment of the analysis method of the influence of the hard roof movement on the mine pressure and gas emission law is as follows:

[0057] See also Figure 1-Figure 20 , a method for analyzing the influence of hard roof movement on mine pressure and gas emission law, including the following methods:

[0058] The numerical simulation geometric model of fully mechanized top coal caving mining is established by using FLAC3D finite element software. The rock strata in the geometric model use the same rock mechanics parameters. The influence of the compressive strength, layer position, thickness and mining height of the hard roof on the mine pressure is analyzed, including:

[0059] 1. Analyze the influence of different high-level hard roof compressive strength on the mining pressure in the mining area, specifically:

[0060] In the simulation experiment of the geometric model, the mining height, layer and thickness parameters are controlled to remain unchanged, and the compressive strength is changed from low to high; with the change of the compressive strength of the hard roof, the changes in the height and angle of the collapse zone are analyzed, and then the deformation influence of the overburden displacement field is analyzed; the changes in the influence range of the advance support stress of the working face are analyzed; the mean value of the peak value of the advance support stress of the working face, the forward shift of the peak influence area and the changes in the stress concentration area are analyzed; the release characteristics of rock strata under different hard roof compressive strengths are analyzed.

[0061] 2. Analyze the influence of different high-level hard roof layers on the mining pressure manifestation in the mining area, specifically:

[0062] In the simulation experiment of the geometric model, the mining height, compressive strength and thickness parameters are controlled unchanged, and the layers are changed from low to high in sequence; with the change of the hard roof layer, the changes in the height and angle of the collapse zone are analyzed, and then the deformation influence of the overburden displacement field is analyzed; the changes in the influence range of the advance support stress of the working face are analyzed; the mean value of the peak value of the advance support stress of the working face, the forward shift of the peak influence area and the changes in the stress concentration area are analyzed; and the energy release characteristics of the rock formations under different hard roof layers are analyzed.

[0063] 3. Analyze the influence of different high-level hard roof thickness on the mining pressure in the mining area, specifically:

[0064] In the simulation experiment of the geometric model, the mining height, layer position and compressive strength parameters are controlled unchanged, and the thickness is increased successively; with the change of the thickness of the hard roof, the changes in the height and angle of the collapse zone are analyzed, and then the deformation influence of the overburden displacement field is analyzed; the changes in the influence range of the advance support stress of the working face are analyzed; the changes in the mean peak value of the advance support stress of the working face, the forward shift of the peak influence area and the stress concentration area are analyzed; and the release characteristics of rock strata under different hard roof thicknesses are analyzed.

[0065] 4. Analyze the influence of different high-level hard roof mining heights on the mining pressure in the mining area, specifically:

[0066] In the simulation experiment of the geometric model, the thickness, layer and compressive strength parameters are controlled unchanged, and the mining height is changed from low to high; as the mining height of the hard roof changes, the changes in the height and angle of the collapse zone are analyzed, and then the deformation influence of the overburden displacement field is analyzed; the changes in the influence range of the advance support stress of the working face are analyzed; the mean value of the peak value of the advance support stress of the working face, the forward shift of the peak influence area and the changes in the stress concentration area are analyzed; and the release characteristics of rock strata under different hard roof mining heights are analyzed.

[0067] Taking the 8103 working face of Tashan Coal Mine as the background, the following specific implementation is carried out:

[0068] Based on the whole process of fully mechanized top-caving mining in extra-thick coal seams, the numerical simulation geometric model of fully mechanized top-caving mining in coal seams was established using FLAC3D finite element software. Figure 1 As shown in Figure 1, the size of the geometric model is 760m×420m (length×height). Except for the hard roof, floor and coal seam, the thickness of the other rock layers is 5m. The rock layers all use the same rock mechanics parameters, as shown in Table 1:

[0069] Table 1

[0070]

[0071] A simulation analysis was conducted on the influence of the compressive strength, layer position, thickness and mining height of high-position hard roof on the deformation characteristics of the overburden displacement field of different hard roofs, the evolution characteristics of the mining stress field of different hard roofs, the evolution law of the advanced support stress of the working face of different hard roofs and the energy release characteristics of the rock strata of different hard roofs on the manifestation of mining pressure in large-space mining areas.

[0072] (1) Analyze the influence of different high-level hard roof compressive strength on the mine pressure manifestation in large-space mining areas

[0073] In the simulation experiment, the mining height, layer position and thickness parameters are kept constant, and the compressive strength is 50MPa, 70MPa, 90MPa and 100MPa respectively. As shown in Table 2:

[0074] Table 2

[0076]

[0077] According to the simulation test analysis, the change of compressive strength has no obvious effect on the deformation of the displacement field of the overburden rock. The height of the collapse zone is between 94.47m and 94.53m, and the collapse angle is between 47.3° and 47.8°. Figure 3 It can be seen that with the increase of the compressive strength of the hard roof, the influence range D of the advanced support stress of the working face gradually increases from 27.52m to 38.99m; combined with Figure 3 and Figure 4It can be seen that the mean value of the peak value of the advanced support stress of the working face, the forward displacement of the peak influence area and the stress concentration area will increase with the increase of compressive strength; the energy release characteristics of the rock formation under different hard roof strengths are analyzed. Figure 5 It can be seen that the energy released by the hard roof is greater than that of other rock layers. As the compressive strength increases, the energy released by the breaking of the hard roof increases continuously. In summary, the compressive strength has a positive effect on the induction of strong mine pressure in the mining area.

[0078] (2) Analyze the influence of different high-level hard roof layers on the mine pressure manifestation in large-space mining areas

[0079] In the simulation experiment, the mining height, compressive strength and thickness parameters are kept constant, and the layers are 50m, 100m, 150m, 200m and 250m respectively. As shown in Table 3:

[0080] Table 3

[0081]

[0082] Combination Figure 6 According to the simulation test analysis, the change of the layer position has no obvious effect on the deformation of the overburden displacement field. The height of the collapse zone is between 93.15m and 94.53m, and the collapse angle is between 49.1° and 54.2°. Figure 7 It can be seen that as the hard roof layer increases, the influence range D of the working face advance support stress increases first and then decreases; combined with Figure 7 and Figure 8 It can be seen that the mean value of the peak value of the advanced support stress of the working face, the forward displacement of the peak influence area, and the stress concentration area will change in a "Λ" shape with the increase of the layer, and all reach the peak value at the layer of 150m. By analyzing the energy release characteristics of the rock strata under different hard roof layers, it is found that Fig. 9 It can be seen that as the layer increases, the energy released by the breaking of the hard roof changes in an "Λ" shape. In summary, the layer shows a phenomenon of first strengthening and then weakening for the strong mine pressure in the mining area, and reaches the maximum at the 150m layer.

[0083] (3) Analyze the influence of different high-level hard roof thicknesses on the mine pressure in large-space mining areas

[0084] The simulation experiment controlled the mining height, layer position, and compressive strength parameters to remain unchanged, and the thickness was 10m, 15m, 20m, 25m, and 30m, respectively. As shown in Table 4:

[0085] Table 4

[0086]

[0087] Combination Fig.10According to the simulation test analysis, the change of thickness has no obvious effect on the deformation of the overburden displacement field. The height of the collapse zone is between 91.95m and 94.53m, and the collapse angle is between 46.5° and 47.4°. Fig.11 It can be obtained that as the thickness of the hard roof increases, the influence range D of the working face advance support stress increases accordingly; combined with Fig.11 and Fig.12 It can be seen that the mean value of the peak value of the advanced support stress of the working face, the forward displacement of the peak influence area, and the stress concentration area will increase with the increase of thickness; by analyzing the energy release characteristics of the rock formation under different hard roof thicknesses, Fig.13 It can be seen that as the thickness increases, the energy released by the breaking of the hard roof continues to increase. In summary, the thickness and the strong mining pressure in the mining area are positively correlated.

[0088] (4) Analyze the impact of different high-level hard roof mining heights on the mine pressure in large-space mining areas

[0089] The simulation experiment controlled the thickness, layer position, and compressive strength parameters to remain unchanged, and the mining heights were 5m, 10m, 15m, and 20m, respectively. As shown in Table 5:

[0090] Table 5

[0091]

[0092] Combination Fig.14 According to the simulation test analysis, the change of mining height has a significant impact on the deformation of the overburden displacement field, among which the collapse zone height increases from 20.52m to 94.53m, and the collapse angle increases from 12.5° to 47.3°; Fig.15 It can be seen that as the mining height of the hard roof increases, the influence range D of the advanced support stress of the working face increases accordingly; combined with Fig.15 and Fig.16 It can be seen that the mean peak value of the advanced support stress of the working face decreases with the increase of mining height, and the forward movement of the peak influence area and the stress concentration area will increase with the increase of mining height; the energy release characteristics of the rock strata under different hard roof mining heights are analyzed. Fig.17 It can be seen that with the increase of mining height, the energy released by the breaking of the hard roof continues to increase. In summary, except for the peak value of the advanced support stress of the working face which decreases with the increase of mining height, other aspects increase accordingly.

[0093] According to the above summary and analysis, the increase in the compressive strength, thickness and mining height of the hard roof has a significant impact on the manifestation of mine pressure, while the change in the stratigraphic position only has a significant impact on the mine pressure at 150m. Therefore, by adopting the above method, the influence of the movement of the hard roof on the law of mine pressure manifestation can be simulated and analyzed, so as to prepare protective measures in advance, protect equipment and personnel, and reduce safety hazards.

[0094] The maximum bending moment of the hard roof occurs in the center of the plate, and then cracks are formed at the two longitudinal grooves. As the cracks on all sides penetrate, it becomes a flat "O" shape. The bending moment in the center of the plate exceeds the strength limit to form cracks, resulting in "X"-shaped rupture, which is the "OX" fracture mechanism of the hard roof. The fracture of the hard roof will cause the volume of the coal seam goaf to decrease, squeezing the gas therein and causing gas to gush out.

[0095] Combined with the on-site measured data of 8214 fully mechanized caving working face in Tashan Coal Mine in Datong Mining Area, the effect of hard roof collapse on gas emission is analyzed.

[0096] Based on the "OX" breaking mechanism of the hard roof, the change of the goaf volume before and after the hard roof breaks is analyzed, and a calculation model for the increase in gas outburst in the goaf during the periodic pressure is established. Specifically:

[0097] like Fig.18 and Fig.19 As shown in the figure, the goaf shape after the hard roof is broken is simplified into a quadrangular prism with a right-angled trapezoidal cross section. Fig.18 and Fig.19 In the figure, L3 is the distance between the hard roof and the coal seam floor, and ΔH is the total displacement of the end of the broken block of the hard roof;

[0098] Calculate the change in the volume of the goaf space before and after the hard roof collapses, and then estimate the increase in gas outburst in the goaf. The increase in gas outburst in the goaf during the pressure period is Q:

[0099]

[0100] Among them, Q is the increase of gas outburst in the goaf, C is the average gas concentration in the goaf, ΔV is the change of the spatial volume of the goaf before and after the hard roof collapses, L1 and L2 are the short and long sides of the hard roof, m1 is the coal mining thickness, m2 is the coal caving thickness, m3 is the thickness of the soft rock layer below the hard roof, α is the final inclination angle of the broken block, and K p It is the expansion coefficient for breaking the residual coal and gangue under the hard roof, t2 is the duration of the cycle pressure, and the air leakage rate is 15%.

[0101] According to the field measured data of 8214 fully mechanized caving working face and the monitoring data obtained by the internal bundle pipe arranged on site in the goaf, it is calculated that the increase in gas outburst Q in the goaf during the period of pressure increase is about 14.5m 3 / min.

[0102] According to the on-site fully mechanized caving working face monitoring results, the calculation model of the increase in gas emission in the goaf during the periodic pressure is verified to be accurate, specifically:

[0103] According to the field measured data of the fully mechanized caving working face, the gas outflow volume of the working face and the gas outflow volume of the goaf before and after the periodic pressure when the working face experienced several periodic pressures and accompanied by the rotation and breaking of the hard roof of the goaf was obtained;

[0104] Calculate whether the error between the actual increase in gas outflow from the goaf after periodic pressure increase and the theoretical increase in gas outflow obtained by the calculation model for the increase in gas outflow from the goaf during periodic pressure increase is within the set range.

[0105] according to Fig. 20 Analysis shows that the working face experienced five cycles of pressure in May. With the rotation and breaking of the hard roof in the goaf, the gas outflow from the working face increased significantly and was slightly delayed from the peak value of the support resistance. Based on the measured data, the average gas outflow from the working face and the average gas outflow from the goaf before and during the five cycles of pressure were recorded and summarized, as shown in Table 6 and Table 7 respectively:

[0106] Table 6

[0107]

[0108] Table 7

[0109]

[0110] Through on-site measurement of gas outburst in various parts of the 8214 working face, it is concluded from Table 6 and Table 7 that gas outburst in the goaf during normal mining accounts for 56.9% of the total gas outburst, and gas outburst in the goaf during periodic pressure accounts for 64.5% of the total gas outburst. 3 / min, the errors between the two are 8.28%, 1.38%, 7.59%, 3.45% and 4.83% respectively, which verifies the correctness of the model.

[0111] The results show that the breaking and rotation of the hard roof causes high-gas gas in the goaf to flow into the working face, resulting in abnormal gas outflow during the periodic pressure inflow. By establishing the calculation model for the increase in gas outflow in the goaf during the periodic pressure inflow after the above verification, the increase in gas outflow can be analyzed and obtained in time after the drastic change in mine pressure, so as to take corresponding safety measures in time, thereby reducing the safety hazards of mine operations.

[0112] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that many changes, modifications, substitutions and variations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for analyzing the influence of hard roof movement on mine pressure and gas emission law, characterized in that: The following methods are included: The numerical simulation geometric model of coal seam fully mechanized caving mining is established by using FLAC3D finite element software, and the rock strata in the geometric model all adopt the same rock mechanics parameters; Analyze and obtain the influence of the compressive strength, layer position, thickness and mining height of the hard roof on the manifestation of mine pressure; Based on the "OX" breaking mechanism of the hard roof, the volume change of the goaf before and after the hard roof breaks is analyzed, and a calculation model for the increase in gas outburst in the goaf during the periodic pressure is established; Based on the on-site fully mechanized caving working face monitoring results, verify whether the calculation model of the increase in gas outburst in the goaf during the period of pressure increase is accurate.

2. The method for analyzing the influence of hard roof movement on mine pressure and gas emission law according to claim 1 is characterized in that: The influence of different high-level hard roof compressive strength on the mining pressure in the mining area is analyzed, specifically: In the simulation experiment of the geometric model, the mining height, layer position and thickness parameters are controlled to remain unchanged, and the compressive strength is changed from low to high; As the compressive strength of the hard roof changes, the changes in the height and angle of the collapse zone are analyzed, and then the deformation influence of the overburden displacement field is analyzed; the changes in the influence range of the advance support stress of the working face are analyzed; the mean value of the peak value of the advance support stress of the working face, the forward displacement of the peak influence area, and the changes in the stress concentration area are analyzed; Analyze the release characteristics of rock energy under different hard roof compressive strengths.

3. The method for analyzing the influence of hard roof movement on mine pressure and gas emission law according to claim 1 is characterized in that: The influence of different high-level hard roof layers on the mining pressure manifestation in the mining area is analyzed, specifically: In the simulation experiment of the geometric model, the mining height, compressive strength and thickness parameters are controlled to remain unchanged, and the layers are changed from low to high. With the change of the hard roof layer, the change of the collapse zone height and collapse angle is analyzed, and then the deformation influence of the overburden displacement field is analyzed; the change of the influence range of the working face advance support stress is analyzed; the change of the mean value of the working face advance support stress peak, the forward displacement of the peak influence area and the stress concentration area is analyzed; Analyze the energy release characteristics of rock strata under different hard roof layers.

4. The method for analyzing the influence of hard roof movement on mine pressure and gas emission law according to claim 1 is characterized in that: The influence of different high-level hard roof thicknesses on the mining pressure in the mining area is analyzed, specifically: In the simulation experiment of the geometric model, the mining height, layer position and compressive strength parameters are controlled to remain unchanged, and the thickness is increased in sequence; As the thickness of the hard roof changes, the changes in the height and angle of the collapse zone are analyzed, and then the deformation influence of the overburden displacement field is analyzed; the changes in the influence range of the advance support stress of the working face are analyzed; the changes in the mean value of the peak value of the advance support stress of the working face, the forward displacement of the peak influence area, and the stress concentration area are analyzed; Analyze the release characteristics of rock energy under different hard roof thicknesses.

5. The method for analyzing the influence of hard roof movement on mine pressure and gas emission law according to claim 1 is characterized in that: The influence of different high-level hard roof mining heights on the mining pressure in the mining area is analyzed, specifically: In the simulation experiment of the geometric model, the thickness, layer position and compressive strength parameters are controlled to remain unchanged, and the mining height is changed from low to high; As the mining height of the hard roof changes, the changes in the height and angle of the collapse zone are analyzed, and then the deformation influence of the overburden displacement field is analyzed; the changes in the influence range of the advanced support stress of the working face are analyzed; the changes in the mean value of the peak value of the advanced support stress of the working face, the forward displacement of the peak influence area, and the stress concentration area are analyzed; Analyze the energy release characteristics of rock strata under different hard roof mining heights.

6. The method for analyzing the influence of hard roof movement on mine pressure and gas emission law according to claim 1 is characterized in that: Based on the hard roof "OX" breaking mechanism, a calculation model for the increase in gas outburst in the goaf during the period of pressure increase is established, specifically: The shape of the goaf after the hard roof is broken is simplified to a quadrangular prism with a right-angled trapezoidal cross section; Calculate the change in the volume of the goaf space before and after the hard roof collapses, and then estimate the increase in gas outburst in the goaf: Among them, Q is the increase of gas outburst in the goaf, C is the average gas concentration in the goaf, ΔV is the change of the spatial volume of the goaf before and after the hard roof collapses, L1 and L2 are the short and long sides of the hard roof, m1 is the coal mining thickness, m2 is the coal caving thickness, m3 is the thickness of the soft rock layer below the hard roof, α is the final inclination angle of the broken block, and K p is the expansion coefficient of the remaining coal and gangue under the hard roof, t2 is the duration of the cycle pressure, and γ is the air leakage rate.

7. The method for analyzing the influence of hard roof movement on mine pressure and gas emission law according to claim 6 is characterized in that: Verify whether the calculation model of the increase in gas outburst in the goaf during the periodic pressure is accurate, specifically: According to the field measured data of the fully mechanized caving working face, the gas outflow volume of the working face and the gas outflow volume of the goaf before and after the periodic pressure when the working face experiences several periodic pressures accompanied by the rotation and breaking of the hard roof of the goaf are obtained; Calculate whether the error between the actual increase in gas outflow from the goaf after the periodic pressure increase and the theoretical increase in gas outflow obtained by the calculation model for the increase in gas outflow from the goaf during the periodic pressure increase is within a set range.

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