A method, system and medium for determining activation of mining fault

Abstract

The present invention provides a method, system and medium for determining fault activation caused by mining, which relates to the field of geological engineering technology, including: by analyzing the response speed of multiple stresses to the fault outcrop during the mining process of the working face, the maximum shear stress mutation point is used as a characteristic indicator of fault activation; excavating along the working face perpendicular to the fault in sections, obtaining the settlement value and the maximum shear stress on the monitoring line, and using the mutation point of the settlement value as the starting point of fault activation, wherein the timing of the maximum shear stress mutation point is earlier than the mutation point of the settlement value; by analyzing that the maximum shear stress influence range generated by the mining of the working face on the surface is greater than the movement influence range, the position when the maximum shear stress still maintains the original rock stress level and the angle between the line connecting the coal seam mining boundary point and the horizontal line on one side of the pillar is used as the stress angle, and the stress angle is used as the influence boundary for determining fault activation. The above method is helpful to achieve comprehensive and accurate determination of fault activation.

Description

Technical Field

[0001] The present invention relates to the field of geological engineering technology, and in particular to a method, system and medium for determining activation of a mining fault. Background Art

[0002] Coal occupies a major position in my country's energy structure, but due to high-intensity, large-scale continuous mining, shallow coal resources are gradually exhausted, and mining has shifted to deep deposits with more complex geological conditions. Among them, faults, as common geological structures in complex mining conditions, are prone to slip and instability due to mining, which may cause geological disasters such as water inrush and rock burst, seriously affecting the safe production and ecological environment management of the mining area.

[0003] In the existing technology, Yu Xueyi and others used numerical simulation to study the setting of fault protection coal pillars in response to the phenomenon that underground mining in the Pubai mining area caused fault activation and damaged houses in Zhangpo Village far away from the mining area. Kong Xiansen and others found that if the influence of faults was ignored, the surface damage after mining would be more serious than expected. The reason is that the separation space formed by fault slip controls the scope and extent of mining impact. Diao Xinpeng and others used InSAR technology, theoretical analysis and similar material simulation to reveal and verify that the fundamental cause of abnormal damage to buildings in Shiqiao Village was local fault activation. Yu Qiuge and others combined numerical simulation and similar material experiments to study the mechanism and difficulty of fault activation in upper and lower plate mining. The results showed that the abnormal surface subsidence at the fault outcrop was the result of the soil being fractured by the cantilever after the fault slip became unstable.

[0004] However, it is difficult to fully capture the transmission and changes of stress in faults and surrounding rock masses only through theoretical and numerical simulations, resulting in insufficient understanding of the dynamic development process of mining deformation from the inside out and the stress transfer mechanism under the influence of faults. It is difficult to accurately obtain the corresponding characteristics of surface stress caused by mining under fault conditions, and provide a scientific basis for the identification of damage to mining buildings and surface damage. Summary of the invention

[0005] The present invention provides a method, system and medium for determining fault activation caused by mining. The method is helpful to achieve comprehensive and accurate determination of fault activation.

[0006] A method for determining fault activation caused by mining, comprising the following steps:

[0007] A three-dimensional numerical model was constructed based on the actual geological conditions of the working face in the mining area. A monitoring line was set at the top of the model to simulate the mining process of the working face in the mining area and obtain the dynamic changes of various stresses at the fault outcrop. The stress mutation point of the maximum shear was determined as the characteristic indicator of fault activation.

[0008] Obtain the settlement value and maximum shear stress on the monitoring line, and take the mutation point of the settlement value as the starting point of fault activation;

[0009] The distance between the settlement position where the settlement value of 10 mm appears in the footwall of the fault and the coal seam mining boundary of the model is taken as the surface movement influence range of fault activation, and the distance between the position where the maximum shear stress still maintains the original rock stress level and the coal seam mining boundary is taken as the surface stress influence range of fault activation, and this is used to judge the activation status of the mining fault at the working face in the mining area.

[0010] Preferably, it also includes: taking the angle between the line connecting the coal seam mining boundary points and the horizontal line on one side of the pillar when the maximum shear stress is restored to the position where the original rock stress level is still maintained as the stress angle, and taking the stress angle as the influencing boundary for determining fault activation.

[0011] Preferably, the simulating the mining process of the working face in the mining area and obtaining the dynamic changes of various stresses at the fault outcrop comprises the following steps:

[0012] Excavation is carried out in sections perpendicular to the fault along the working face, and the overburden strata are fractured and collapsed. The overburden strata are regarded as a cantilever beam subjected to uniformly distributed loads;

[0013] For any point A(x,y) in the cantilever beam, its surface is subjected to a normal stress σ perpendicular to the cross section. x , σ y and the shear stress τ parallel to the cross section xy According to the geometric mechanics relationship, the normal stress and shear stress are expressed as:

[0014]

[0015] In the formula, σ x and σ y They refer to the normal stress in the X and Y directions, τ xy It refers to the shear stress parallel to the cross section, q refers to the load on the overburden, h is the distance between the overburden and the coal seam floor, and x and y are the coordinates of any point in the cantilever beam.

[0016] Preferably, the maximum shear stress is the principal shear stress with the largest absolute value, then the maximum shear stress τ max for:

[0017]

[0018] Where σ1 is the maximum principal stress and σ3 is the minimum principal stress.

[0019] Preferably, it also includes:

[0020] Before using the stress angle as the influencing boundary for determining fault activation, the boundary angle, movement angle, and stress angle are defined to obtain the distance between the working surface and the fault;

[0021] By analyzing the relationship between the boundary angle, movement angle and stress angle and the distance between the working face and the fault, as well as the coordinated variation law between the three angle values, the stress angle is used as the influencing boundary for determining fault activation.

[0022] Preferably, it also includes:

[0023] The width of the fault protection coal pillar is determined by the stress angle. If the mining influence range of the working face defined by the stress angle is just transferred to one side of the fault, the width D of the fault protection coal pillar is:

[0024]

[0025] Where H is the thickness of the overlying rock layer on the working face, α is the stress angle, and θ is the fault dip angle.

[0026] A mining fault activation determination system, the system comprising:

[0027] processor;

[0028] a memory having stored thereon a computer program executable on the processor;

[0029] Wherein, when the computer program is executed by the processor, the steps of the method for determining the activation of a mining fault are implemented.

[0030] A computer-readable storage medium stores a data processing program, and when the data processing program is executed by a processor, the steps of the method for determining the activation of a mining fault are implemented.

[0031] Compared with the prior art, the present invention analyzes different types of stress change processes and finds that the maximum shear stress begins to mutate first, and then the stress value maintains a stable growth state. The maximum shear stress is selected as the benchmark for judging the "activation" of the fault to avoid multiple activations. The surface movement influence range and the surface stress influence range are used as the basis for judging fault activation. At the same time, by establishing the relationship between the mechanical angle value parameters with missing measured data and the movement angle value parameters with rich data, the stress angle is used as the influence boundary for determining fault activation, and the surface stress characteristics of mining under fault conditions are accurately obtained, thereby achieving a comprehensive and accurate judgment of fault activation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a flow chart of the method for determining the activation of a mining fault provided in the first embodiment of the present invention.

[0033] Figure 2 It is a schematic diagram of the cantilever beam mechanical model provided by the first embodiment of the present invention.

[0034] Figure 3 (a) is the dynamic change curve of normal stress Sxx; Figure 3 (b) is the dynamic change curve of normal stress Syy; Figure 3 (c) is the dynamic change curve of normal stress Szz; Figure 3 (d) is the dynamic change curve of shear stress Sxy; Figure 3 (e) is the dynamic change curve of shear stress Sxz; Figure 3 (f) is the dynamic change curve of shear stress Syz; Figure 3 (g) is the dynamic change curve of maximum principal stress; Figure 3 (h) is the dynamic change curve of minimum principal stress; Figure 3 (i) is the dynamic change curve of maximum shear stress;

[0035] Figure 4 (a) is the surface settlement curve after each excavation of the working face, Figure 4 (b) is the trend of surface subsidence at the fault outcrop. Figure 4 (c) is the surface settlement curve, Figure 4 (d) is the changing trend of the scope of influence of surface movement during mining.

[0036] Figure 5 (a) is the maximum shear stress variation curve when the stop-mining line is 450m, 350m, 250m, 100m and 50m away from the fault. Figure 5 (b) is the stress variation trend at the fault outcrop during mining. Figure 5 (c) is the changing trend of the influence range of surface stress with the progress of mining.

[0037] Figure 6 It is the relationship between the three angle values ​​and the mining progress, as well as the coordinated change relationship between the three angle values.

[0038] Figure 7 A schematic diagram is provided for the fault protection coal pillar;

[0039] Figure 8 Schematic diagram of the impact range of surface movement, the impact range of surface stress and the stress angle. DETAILED DESCRIPTION

[0040] Many specific details are described in the following description to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific implementation disclosed below.

[0041] The first embodiment of the present invention provides a method for determining the activation of a mining fault. Figure 1 , which is a flow chart of the first embodiment of the present invention. Figure 1 - Figure 2The method provided by the first embodiment of the present invention is described in detail.

[0042] Step S101, by analyzing the response speed of various stresses to the fault outcrop during the mining process of the working face, the maximum shear stress mutation point is used as a characteristic indicator of fault activation.

[0043] This step is used to determine a stress index that has a fast propagation speed, a wide impact range, and obvious change characteristics.

[0044] The overburden movement and stress redistribution caused by underground mining are gradually transmitted upward from the mining space. When the mining effect is transmitted to the surface, different areas will be damaged to a certain extent according to the scale of stress disturbance, and pressurization areas, pressure relief areas and pressure stabilization areas will be formed in the overburden. Figure 2 , This figure is a schematic diagram of the cantilever beam mechanical model. After the working face is mined, the overlying rock strata fracture and collapse. At this time, it can be regarded as a cantilever beam subjected to a uniformly distributed load.

[0045] For any point A(x,y) in the cantilever beam, its surface is subjected to a normal stress (σ x , σ y ) and the shear stress τ parallel to the cross section xy According to the geometric mechanics relationship, the normal stress and shear stress can be expressed as:

[0046]

[0047] Where q represents the load of the overburden, and its value is related to the elastic modulus, bulk density and height from the bottom of the key layer, and h is the distance between the overburden and the bottom of the coal seam.

[0048] From the above formula, it can be seen that when the load q is constant, the magnitude of the three stress components is mainly inversely proportional to the overburden height h, that is, the closer to the coal seam, the more obvious the stress concentration phenomenon. Therefore, in the process of stress transmission, its influence intensity will continue to decay with the increase of overburden height. In addition, the fault, as a structural surface with weak mechanical properties, will also produce a certain barrier and absorption of stress, resulting in the failure to present a stress change law with obvious characteristics on the surface.

[0049] The various stresses include: normal stress, shear stress, maximum principal stress, minimum principal stress, and maximum shear stress.

[0050] As the working face continues to advance toward the fault, the dynamic change law of stress at the fault outcrop is roughly similar, that is, under the action of mining, the stress value at the fault outcrop first rises or falls gently, and then at a certain moment, the stress value suddenly changes significantly, which is a sign that the working face mining disturbs the fault and activates it. The distance between the stop mining line and the fault at this time can be used as the starting point of fault activation. The time point at which each of the above stresses suddenly changes represents its sensitivity to fault disturbance and its propagation speed in the overlying rock formation.

[0051] By analyzing the above different types of stress change processes, the maximum shear stress first begins to change suddenly, and then the stress value keeps a stable growth state and then gradually flattens out. Among them, the maximum shear stress refers to the principal shear stress with the largest absolute value. The maximum shear stress can be used to determine the failure point and strength limit of the material, and has more practical physical significance than other stress indicators.

[0052] The maximum shear stress is the principal shear stress with the largest absolute value, assuming that for any force-bearing unit, there is a normal stress σ in the x and y directions. x and σ y , the shear stress in the xoy plane is τ xy , then the maximum shear stress τ max for:

[0053]

[0054] Where σ1 is the maximum principal stress and σ3 is the minimum principal stress.

[0055] Step S102, excavate in sections along the working face perpendicular to the fault, obtain the settlement value and maximum shear stress on the monitoring line, and use the mutation point of the settlement value as the starting point of fault activation, wherein the timing of the maximum shear stress mutation point appears earlier than the mutation point of the settlement value.

[0056] This step is used to take the mutation point of the settlement value as the starting point of fault activation.

[0057] By obtaining the settlement value on the monitoring line, the surface settlement curve after each excavation of the working face is drawn. The surface settlement curve is symmetrical about the goaf in a "funnel shape"; and as the goaf continues to expand, the maximum surface settlement value and the settlement influence range are also increasing, and the settlement center is constantly moving toward the fault. The above characteristic description of the distribution of surface settlement conforms to the law of conventional mining subsidence. When the stop mining line is less than or equal to a certain distance from the fault, the surface settlement curve gradually changes from "symmetrical" to "asymmetrical", and the closer to the fault, the more obvious this non-skewed sinking phenomenon is. This is the result of fault activation under mining action. Therefore, the timing of the settlement mutation point is used as a sign of fault activation.

[0058] At the same time, by analyzing the settlement value and the maximum shear stress on the monitoring line, it can be found that the maximum shear stress mutation point occurs earlier than the settlement mutation point. For a detailed analysis, please refer to the second embodiment of the present invention.

[0059] Step S103, by analyzing that the influence range of the maximum shear stress generated by the working face mining on the surface is larger than the influence range of the movement, the angle between the position when the maximum shear stress is restored to the original rock stress level and the horizontal direction on one side of the pillar is taken as the stress angle, and the stress angle is used as the influence boundary for determining the fault activation.

[0060] This step is used to use the stress angle as the influencing boundary for determining fault activation, thereby determining whether the fault is activated.

[0061] The maximum shear stress influence range generated by the mining of the working face on the ground surface is greater than the movement influence range, including:

[0062] After each mining, the settlement value and maximum shear stress on the monitoring line are extracted. For judging the movement influence range, the distance between the position where the footwall of the fault has a 10mm settlement and the leftmost boundary of the model is used; for judging the stress influence range, the distance between the nearest position where the footwall of the fault still maintains the original rock stress level and the leftmost boundary of the model is used.

[0063] With each excavation step, the position where the footwall of the fault experiences a 10 mm settlement and the most recent position where the footwall of the fault still maintains the original rock stress level are recorded, namely, the movement influence range and stress influence range.

[0064] After n steps of excavation, there are n pairs of influence ranges. Then a scatter plot of each influence range with respect to the excavation distance is drawn and fitted to obtain the relevant fitting formula.

[0065] The change rules of the two influence ranges are mainly manifested as follows: before the fault is disturbed, the surface movement and stress influence range show an accelerated growth trend under the action of mining; and after the working face disturbs the fault, the surface movement stress influence range slows down under the barrier effect of the fault, and finally approaches an interval. In general, the maximum shear stress influence range generated by the working face mining on the surface is larger than the movement influence range. Before the stress angle is used as the influence boundary for determining fault activation, it also includes:

[0066] Define the boundary angle, movement angle, and stress angle to obtain the distance between the working face and the fault; by analyzing the relationship between the boundary angle, movement angle, and stress angle with the distance between the working face and the fault, as well as the coordinated change law between the three angle values, the stress angle is used as the influence boundary for determining fault activation. The width of the fault protection coal pillar is determined by the stress angle. If the mining influence range of the working face defined by the stress angle is just transferred to one side of the fault, the width D of the fault protection coal pillar is:

[0067]

[0068] Where H is the thickness of the overlying rock layer on the working face, α is the stress angle, and θ is the fault dip angle.

[0069] The second embodiment of the present invention provides an application example of the method for determining fault activation caused by mining, which is as follows:

[0070] Based on the actual geological data of the 158 working face in a mining area of ​​Wannian Mine in Handan City, the working face is located in the Shanxi Formation of the Permian System. The overall occurrence pattern is from SN to NW, the working face floor elevation is 750m to 900m, the coal seam dip is 1° to 14°, the average mining thickness is 5m, and the mining depth is 610m. The working face has a strike length of 546m and a dip width of 130m. Its top and bottom plates are mainly composed of carbonate shale and siltstone, which are partially affected by small faults and are easily broken and fall off. The geological structure around the 158 working face is complex, with three major normal faults, namely F49 (H=100-150m, ∠65-70°), F13 (H=80-140m, ∠65-70°) and F15 (H>600m, ∠70°). Among them, the F13 fault is located about 120m northeast of the 158 working face. Its trend is approximately parallel to that of the working face, and it extends for several kilometers. It is very susceptible to fault activation caused by mining, which in turn affects the normal deformation law of the surface.

[0071] The establishment of the numerical model of this embodiment mainly refers to the actual geological conditions of the 158 working face of Wannian Mine. First, in order to minimize the boundary effect, after calculating the impact range of the working face mining, a boundary coal pillar of sufficient width is set for the model, and the size of the constructed model is finally determined to be 3000m×2000m×370m. Then, according to the geological profile and drilling lithology information, the strata with thin thickness or similar lithology are merged to determine the two-dimensional profile of the model; then Rhino and Griddle software are used for three-dimensional modeling and meshing respectively. Considering the stability of the grid and the efficiency of the later simulation operation, a quadrilateral grid with a side length of 20m is selected to generate. Finally, a total of 969798 units and 172823 nodes are divided. According to the results of the on-site geological survey and related rock mechanics tests, the rock physical and mechanical parameters of the model of this embodiment are shown in the table below.

[0072]

[0073] The model boundary adopts roller support constraint conditions, that is, the displacement speeds of the left, right and bottom boundaries of the entire model are all constrained, leaving the top surface free. Since the upper part of the model has been simulated to the surface, there is no need to add additional load conditions to the upper part. After that, only gravity is applied to the model as the initial stress using the model gravity command, and the Mohr-Coulomb constitutive model is used as the yield criterion for coal rock materials. After assigning values ​​to each rock layer and fault fracture zone as above, an initial equilibrium calculation is performed. Finally, the null command is used to excavate in sections perpendicular to the fault along the working face. When the working face is mined, the length and width of the goaf are both more than 1.4 times the mining depth, indicating that the surface has reached a fully mined state. In order to obtain the surface movement and stress data, a monitoring line is set at the top of the model using the profile post-processing command, and the numerical calculation results on the monitoring line are fully extracted.

[0074] The corresponding numerical model was established using the aforementioned 3D modeling and meshing methods, where the fault dip angle was 70°, the fall was 30m, the fault width was 5m, and a 50m fault protection coal pillar was set. Then, 20 segmented excavations were carried out perpendicular to the fault along the working face, with each excavation of 30m. Finally, a monitoring point was set at the fault outcrop to extract the stress value after each excavation and draw the corresponding stress dynamic change curve. Please refer to Figure 3 , this figure shows the dynamic change curves of various stresses.

[0075] By analyzing the above 9 different types of stress change processes, we can find that when the working face is mined to 240m, the maximum shear stress begins to change suddenly, and then the stress value keeps growing steadily until the mining reaches 510m, when the stress change gradually becomes gentle. The maximum shear stress is selected to analyze the stress evolution characteristics of the surface during mining.

[0076] Since the main purpose of this invention is to study the movement and deformation law of overburden and the stress transfer characteristics of the working face during the mining process, it is planned to carry out segmented excavation along the working face perpendicular to the fault, excavating 50m each time, excavating 10 times in total, mining the full height once, and then extracting the settlement value and maximum shear stress of the monitoring line after each excavation. The following is a detailed analysis of the changes in the overburden during the excavation process mainly from the two aspects of displacement and stress.

[0077] Please see Figure 4(a) This figure shows the surface settlement curve after each excavation of the working face. When the stop mining line is more than 200m away from the fault, the surface settlement curve is symmetrical about the goaf in a "funnel shape"; and as the goaf continues to expand, the maximum surface settlement value and the settlement influence range are also increasing, and the settlement center is constantly moving toward the fault. The above characteristic description of the distribution of surface settlement is consistent with the law of conventional mining subsidence. When the stop mining line is less than or equal to 200m away from the fault, the surface settlement curve gradually changes from "symmetrical" to "asymmetrical", and the closer to the fault, the more obvious this non-skewed sinking phenomenon is. At the same time, combined with Figure 4 (b) shows the trend of surface settlement at the fault outcrop. It can be found that when the working face is 200m away from the fault, the settlement value at the fault outcrop suddenly increases by about 50mm compared with the previous value, and then continues to sink at a large amplitude. This is the result of fault activation under mining action, so we can take the timing of the settlement mutation point as a sign of fault activation. Especially at a position about 45m away from the fault in the upper plate, the rate of change of surface settlement increases sharply. This is because the expansion of the goaf intensifies the disturbance of the fault. When the upper plate rock layer slides along the fault surface with weaker mechanical strength, the fault outcrop will produce a large movement deformation, and at the same time accelerate the convergence speed of the settlement boundary. When the stop mining line is 50m away from the fault, the impact of mining on the fault is further intensified. At this time, the height of the sinking step at the fault outcrop reaches 460mm, and the shape of the right half of the surface settlement curve is close to vertical.

[0078] The current "three-down" coal mining regulations mainly use the 10mm settlement contour line as an important indicator for delineating the mining impact range. Therefore, the present invention can extract the surface settlement value on the monitoring line and define the distance between the position where 10mm settlement occurs in the footwall of the fault and the leftmost boundary of the model as the surface movement impact range under the fault occurrence conditions. Figure 4 (c) In the surface settlement curve, when the working face is 50m away from the fault, the surface of the fault footwall has an uplift deformation of about 5 to 6mm. This is because the large-scale subsidence of the fault hanging wall has caused the rock mass in the footwall to lose support. Figure 4 (d) shows the changing trend of the scope of influence of surface movement during mining. Based on the above analysis, we can take "working face 200m away from the fault" as the starting point of the displacement disturbance fault. Before the fault was disturbed, the scope of influence of surface movement showed a steady expansion trend under the action of mining; and when the working face was less than 200m away from the fault, that is, the fault began to activate, the growth rate of the scope of influence of surface movement slowed down, indicating that the barrier effect of the fault on displacement began to appear. In addition, during the entire mining process, the change law of the scope of influence of surface movement conforms to the fitting distribution characteristics of the quadratic polynomial, as shown in the following formula, and its fitting degree R 2 =0.997, indicating a good fitting effect.

[0079] y=-0.00125x 2 -0.039x+1951.6

[0080] In order to clearly show the change of overburden stress before and after fault activation, this embodiment only draws the maximum shear stress change curve when the stop-mining line is 450m, 350m, 250m, 100m and 50m away from the fault, as shown in Figure 2. Figure 5 (a) shown.

[0081] When the working face is more than 250m away from the fault, the underground mining does not disturb the fault, and the surface stress change curve is approximately symmetrical about the goaf. The mining action causes the stress value of the overlying rock strata in the goaf to be the highest, about 0.34MPa; the stress on both sides of the goaf gradually decreases to the level of the original rock stress (0.03MPa). In addition, at a position of about 135m before and after the goaf, a regional stress increase phenomenon occurs. This is because the increase in the underground open area will cause the load of the upper rock strata in the goaf to transfer to the arch feet on both sides, and form a stress concentration zone in the coal wall before and after the working face. Therefore, the above-mentioned mining stress change characteristics basically conform to the general law of "goaf pressure relief, surrounding rock stress concentration".

[0082] As the distance between the working face and the fault continues to decrease, the maximum stress point gradually shifts toward the fault. When the distance between the working face and the fault is less than or equal to 250m, the shape of the stress change curve gradually changes from symmetric to asymmetric, especially near the fault outcrop, where the stress value drops sharply. This is the result of the balance of the underlying rock being broken by mining, and the upper rock mass sliding along the fault plane with weak mechanical strength. At the same time, combined with Figure 5 (b) shows the stress change trend at the fault outcrop during the mining process. It can be found that when the working face is 250m away from the fault, the stress value at the fault outcrop has a significant sudden increase compared with the previous one, indicating that the mining stress has been transmitted to the fault and has a significant impact on it. Compared with the timing of the aforementioned "settlement mutation point", the stress disturbed the fault earlier.

[0083] When the working face is 50m away from the fault, the impact of mining on the fault is further aggravated. Compared with the fault not disturbed, the stress convergence speed of the footwall surface is accelerated at this time, and the surface stress level is restored to below the original rock stress, which also reflects the barrier effect of the fault on stress transmission.

[0084] Combined with the description of the characteristics of overburden movement in the previous section, we can find that the distribution of surface stress is consistent with the movement distribution of conventional mining subsidence basins to a certain extent, that is, the surface above the goaf is significantly affected by mining, and the farther away from the goaf, the weaker the mining impact. Therefore, according to the definition principle of the scope of surface movement influence, the distance between the position of the fault footwall when it is restored to the original rock stress level and the leftmost boundary of the model can be used as the scope of surface stress influence under fault occurrence conditions. The trend of the scope of surface stress influence with the progress of mining is shown in the figure. Figure 5 (c) as shown.

[0085] Based on the above analysis, we can take "working face 250m away from the fault" as the starting point of the stress disturbance fault. Before the fault was disturbed, the surface stress influence range showed an accelerated growth trend under the action of mining; when the working face was less than 250m away from the fault, the growth rate of the surface stress influence range slowed down and eventually approached an interval (2150-2160m), indicating that the fault began to have a barrier effect on stress. In addition, during the entire mining process, the change law of the surface stress influence range conforms to the fitting distribution characteristics of the quadratic polynomial, as shown in the following formula, and its fitting degree R 2 =0.997, indicating a good fitting effect.

[0086] y=-0.00106x 2 +0.133x+2157.5

[0087] In order to explore the coordinated change relationship between surface stress and displacement under fault conditions, this embodiment uses the obtained displacement and stress change curves to first determine the boundary angle and movement angle based on the indicators of 10 mm sinking and 2 mm / m inclination, and then defines the angle between the position when the maximum shear stress is restored to the original rock stress level and the horizontal direction on one side of the pillar as the stress angle. Figure 6 The relationship between the three angle values ​​and the mining progress and the coordinated change relationship between the three angle values ​​are shown respectively.

[0088] As the distance between the working face and the fault decreases, the stress angle and boundary angle show a slow growth trend. However, when the working face mining disturbs the fault, the growth rate of the two angle values ​​suddenly increases when the stop mining line is 250m and 200m away from the fault, respectively, indicating that the fault has a barrier effect on both deformation and stress at this time, and the expansion of its influence range begins to slow down. The changes in the boundary angle and stress angle during the mining process are consistent with the fitting distribution characteristics of the Logistic function, as shown in the following formula, and their fitting degrees are 0.975 and 0.952, respectively, indicating that the fitting effect is good.

[0089]

[0090] Figure 6(c) shows the change of the moving angle with the progress of mining. When the distance between the working face and the fault is greater than 200m, the moving angle value remains relatively stable; when the distance between the working face and the fault is 200m, the moving angle suddenly drops, indicating that the influence range of the surface tilt deformation suddenly increases. Combined with the tilt change curve in the figure, it can be found that the position where the moving angle suddenly drops corresponds to an independent inflection point, that is, three extreme values ​​appear on a tilt curve, indicating that when the working face disturbs the fault, there is often a hidden mining damage zone near the conventional mining subsidence basin. Due to the limitations of numerical simulation, it cannot be reflected on the settlement curve, but can be clearly shown on the tilt curve. Then, as the working face is further mined, the two areas will eventually become one, which is consistent with the conclusion of the change of the plastic zone in the previous section. When the distance between the working face and the fault is less than 200m, the moving angle value gradually increases, indicating that the tilt influence range begins to be blocked by the fault. The change law of the moving angle during mining conforms to the fitting distribution characteristics of the polynomial, as shown in the following formula, and its fitting degree is 0.873.

[0091] y=-5.765x 3 +5.317x 2 -0.144x+67.733

[0092] Figure 6 (b) shows the coordinated change relationship between the boundary angle and the stress angle. When the distance between the working face and the fault is greater than 200m, the changes in the stress angle and the boundary angle are relatively stable and the degree of aggregation is high. When the distance between the working face and the fault is less than 200m, both angles show a significant sudden increase, indicating that the influence of settlement and stress begins to weaken under the barrier effect of the fault. The coordinated change law of the movement angle and the stress angle (such as Figure 6 (d) In addition to the above characteristics, when the working face is 200m away from the fault, the two angle values ​​have a significant sudden drop, which is related to the independent inflection point on the inclination change curve. In addition, the coordinated change law of the boundary angle, movement angle and stress angle during the mining process conforms to the polynomial fitting distribution characteristics, as shown in the following formula, and their fitting degrees reach 0.931 and 0.853 respectively, indicating that the fitting effect is good.

[0093] y=0.141x 2 -14.282x+398.3

[0094] y=0.066x 3 -7.641x 2 +295.2x+3737.27

[0095] In summary, since the stress influence range generated by working face mining on the ground surface is larger than the movement influence range, the conventional boundary angle or movement angle used to determine the influence range of fault activation can no longer be used to guide the placement of appropriate protective coal pillars. Therefore, in actual mining operations, the stress angle can be used to determine the width of the fault protective coal pillar. Figure 7 As shown in the figure, this is a schematic diagram of the fault protection coal pillar. If the mining influence range of the working face defined by the stress angle is just transferred to one side of the fault, the width D of the fault protection coal pillar should satisfy the following formula:

[0096]

[0097] Where H is the thickness of the overlying rock layer on the working face, α is the stress angle, and θ is the fault dip angle.

[0098] A third embodiment of the present invention provides a mining fault activation determination system, which is used to implement any of the mining fault activation determination methods described above. The mining fault activation determination system includes:

[0099] Stress analysis module, which is used to analyze the response speed of various stresses to the fault outcrop during the mining process of the working face, and use the maximum shear stress mutation point as a characteristic indicator of fault activation;

[0100] The displacement analysis module is used to excavate in sections along the working face perpendicular to the fault, obtain the settlement value and maximum shear stress on the monitoring line, and use the mutation point of the settlement value as the starting point of fault activation. The maximum shear stress mutation point appears earlier than the mutation point of the settlement value.

[0101] The activation judgment module is used to analyze that the influence range of the maximum shear stress generated on the surface by working face mining is larger than the influence range of movement. The angle between the position when the maximum shear stress is restored to the original rock stress level and the horizontal direction on one side of the pillar is taken as the stress angle, and the stress angle is used as the influence boundary for determining fault activation.

[0102] A fourth embodiment of the present invention provides a computer-readable storage medium, on which a data processing program is stored. When the data processing program is executed by a processor, the steps of determining the activation of a mining-induced fault described above are implemented.

[0103] Although the present invention is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. A method for determining fault activation caused by mining, characterized in that: include: A three-dimensional numerical model was constructed based on the actual geological conditions of the working face in the mining area. A monitoring line was set at the top of the model to simulate the mining process of the working face in the mining area and obtain the dynamic changes of various stresses at the fault outcrop. The stress mutation point of the maximum shear was determined as the characteristic indicator of fault activation. Obtain the settlement value and maximum shear stress on the monitoring line, and take the mutation point of the settlement value as the starting point of fault activation; The distance between the settlement position where the settlement value of 10mm appears in the footwall of the fault and the coal seam mining boundary of the model is taken as the surface movement influence range of fault activation, and the distance between the position where the maximum shear stress still maintains the original rock stress level and the coal seam mining boundary is taken as the surface stress influence range of fault activation, and the activation state of the mining fault in the working face of the mining area is judged by this. The method of simulating the mining process of the working face in the mining area and obtaining the dynamic changes of various stresses at the fault outcrop includes the following steps: Excavation is carried out in sections perpendicular to the fault along the working face, and the overburden strata are fractured and collapsed. The overburden strata are regarded as a cantilever beam subjected to uniformly distributed loads; For any point A(x,y) in the cantilever beam, its surface is subjected to a normal stress σ perpendicular to the cross section. x , σ y and the shear stress τ parallel to the cross section xy According to the geometric mechanics relationship, the normal stress and shear stress are expressed as: In the formula, σ x and σ y They refer to the normal stress in the X and Y directions, τ xy is the shear stress parallel to the cross section, q is the load on the overburden, h is the distance between the overburden and the coal seam floor, and x and y are the coordinates of any point in the cantilever beam; The maximum shear stress is the principal shear stress with the largest absolute value, so the maximum shear stress τ max for: Where σ1 is the maximum principal stress and σ3 is the minimum principal stress.

2. The method for determining fault activation caused by mining according to claim 1, characterized in that: Also includes: The angle between the position where the maximum shear stress is restored to the original rock stress level and the line connecting the coal seam mining boundary points and the horizontal line on one side of the pillar is taken as the stress angle, and the stress angle is used as the influencing boundary for determining fault activation.

3. The method for determining fault activation caused by mining according to claim 1, characterized in that: Also includes: Before using the stress angle as the influencing boundary for determining fault activation, the boundary angle, movement angle, and stress angle are defined to obtain the distance between the working surface and the fault; By analyzing the relationship between the boundary angle, movement angle and stress angle and the distance between the working face and the fault, as well as the coordinated variation law between the three angle values, the stress angle is used as the influencing boundary for determining fault activation.

4. The method for determining fault activation caused by mining according to claim 1, characterized in that: Also includes: The width of the fault protection coal pillar is determined by the stress angle. If the mining influence range of the working face defined by the stress angle is just transferred to one side of the fault, the width D of the fault protection coal pillar is: Where H is the thickness of the overlying rock layer on the working face, α is the stress angle, and θ is the fault dip angle.

5. A mining fault activation determination system, characterized in that: The system comprises: processor; a memory having stored thereon a computer program executable on the processor; Wherein, when the computer program is executed by the processor, the steps of the method for determining the activation of a mining fault as described in any one of claims 1 to 4 are implemented.

6. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a data processing program, and when the data processing program is executed by a processor, the steps of the method for determining the activation of a mining fault as described in any one of claims 1 to 4 are implemented.

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