A method for predicting the height of water-conducting fracture zone in coal seam stratified fully mechanized caving mining

Abstract

The invention relates to the technical field of mining data processing, and specifically discloses a method for predicting the height of a water-conducting fracture zone in coal seam stratified fully mechanized caving mining, which is used to solve the problem that the traditional material point method is difficult to accurately capture the fracture expansion path and height. The method uses a microseismic sensor array to monitor the arrival time difference of P waves and S waves of microseismic events in real time, and uses a microseismic event processing host based on the first, second and third equation groups, combined with a stress intensity factor and a fracture expansion speed formula, to calculate the three-dimensional expansion path and cumulative effect of the fracture, and finally uses a fracture zone height prediction formula to comprehensively consider the physical properties of the rock formation and stress data, accurately predict the final height of the fracture zone, and transmit it to an anchor adjustment device for support optimization; the invention significantly improves the accuracy of fracture zone height prediction by calculating the fracture expansion path, speed and cumulative effect, combined with the physical properties of the rock formation and the stress environment, and ensures the safety and real-time monitoring effectiveness during coal seam mining.

Description

Technical Field

[0001] The present invention relates to the field of mining data processing, and more specifically, to a method for predicting the height of water-conducting fracture zones in coal seam stratified fully mechanized caving mining. Background Art

[0002] In deep multi-layer coal mines, when coal seam stratified fully mechanized caving is used for resource exploitation, the mining of each coal seam will cause the movement and destruction of the overlying rock strata, and the cracks will gradually expand and accumulate as the layers are mined. This cumulative effect has a significant impact on the overlying rock strata, especially in areas where the mine is adjacent to water bodies (such as rivers and lakes) or directly connected to groundwater layers. The development of water-conducting fracture zones will cause the fractures to connect with the water body, which in turn causes serious mine water inrush events. The traditional material point method (MPM) has limitations in dealing with such complex fracture expansion and accumulation processes. The material point method is difficult to accurately capture the path and direction of fracture expansion, especially when fractures are generated and dynamically evolved. It is impossible to effectively simulate the height accumulation of fracture zones in multi-layer coal seam mining and their interaction with overlying rock strata and water bodies. The material point method has a high dependence on grid resolution, and it is difficult to adjust the prediction of fracture zone height in real time during dynamic changes, resulting in deviations in the fracture zone expansion path and height prediction. The support anchor plays an important role in the control of the mine roof. The length of the anchor needs to cover the expansion area of ​​the fracture zone to increase the stability of the roof. The installation angle of the anchor needs to be adjusted according to the direction of the fracture expansion. The prediction of the expansion path and height of the water-conducting fracture zone plays a vital role in the adjustment of the length and installation angle of the anchor. Therefore, there is an urgent need for a method to improve the limitations of the material point method in predicting the expansion path and height of the water-conducting fracture zone, so as to guide the anchor adjustment equipment to adjust the anchor length. Summary of the invention

[0003] In order to overcome the above-mentioned defects of the prior art, the present invention provides a method for predicting the height of water-conducting fracture zones in coal seam stratified fully-mechanized caving mining. By calculating the fracture expansion path, speed and cumulative effect, combined with the physical properties and stress environment of the rock formation, the accuracy of fracture zone height prediction is improved, thereby ensuring the safety of coal seam mining and the effectiveness of real-time monitoring.

[0004] The layer-by-layer mining of coal seams leads to the expansion of cracks in the overlying rock strata, which is a dynamic process. The cracks will not only gradually expand with the mining process, but also the expansion speed and direction of the cracks will fluctuate nonlinearly due to changes in geological conditions and stress fields. When the mine is connected to the water body, this dynamic change will suddenly trigger a water inrush event, so it is particularly important to capture the expansion state of the fracture zone in real time and predict it. The complexity of deep multi-layer coal mines is also reflected in the stress coupling effect between the cracks and the overlying rock strata. When the coal seam is mined, the stress redistribution of the overlying rock strata will accelerate the expansion of the cracks, making it more difficult to predict the crack expansion path. This stress coupling not only affects the expansion of the cracks, but also affects the risk assessment of the connection between the cracks and the water body.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for predicting the height of water-conducting fracture zones in coal seam stratified fully mechanized caving mining is provided. The method simulates the rock deformation and fracture expansion in coal seam mining based on the material point method, predicts the height of the water-conducting fracture zone, and records the arrival time difference of P waves and S waves generated by microseismic events in real time through the microseismic sensor array. In order to improve the defects of the material point method, in the microseismic event processing host, the distance between the source and the microseismic receiver is determined based on the first equation, the starting point of the fracture expansion is located, and then the stress intensity factor is used to evaluate the fracture expansion conditions. Combined with the fracture expansion speed formula, the fracture expansion speed is determined, and the second equation is used to simulate the arrival of P waves and S waves of microseismic events from different sources. The relationship between the time difference of the receiver and the crack expansion path in each direction is used to describe the difference in crack expansion between multiple microseismic events, determine the spatial change of the crack, and then use the third equation group to combine time, spatial position and wave propagation time difference. The crack expansion path and cumulative effect between the crack sources are described through the change of time difference and spatial position, and the expansion and cumulative effect of the crack between the seismic sources are characterized. Combined with the real-time monitored stress field data and the physical properties of the mine rock formation, the fracture zone height prediction formula is used to predict the final height of the water-conducting fracture zone. The microseismic event processing host transmits the predicted final height of the water-conducting fracture zone to the anchor adjustment equipment.

[0007] As a further solution of the present invention, the microseismic source is located in the microseismic event processing host based on the first equation. The first equation is a microseismic event location equation. The equation substitutes the observation data of several microseismic receivers to construct several corresponding microseismic event location equations. The three-dimensional coordinates of the source are solved based on the least squares method by the time difference observed several times and the position of the microseismic receiver. The formula of the first equation is:

[0008] ;

[0009] Where: , are the indices of the microseismic event sources and microseismic receivers, , , They are respectively The horizontal, vertical and vertical coordinates of the microseismic source are: , , They are respectively The horizontal, vertical and vertical coordinates of the microseismic receivers are: The first microseismic event The P and S waves of the earthquake source reach the The time difference of the microseismic receivers is obtained by monitoring the microseismic sensor array. , They are the propagation speeds of P waves and S waves respectively, which are determined through geological exploration reports.

[0010] As a further solution of the present invention, the microseismic event processing host obtains the expansion difference of the cracks generated by the microseismic event in different time periods based on the second equation, and solves the distance between different seismic sources by combining the known receiver coordinates and source coordinates with the propagation speed of the S wave. The formula of the second equation is:

[0011] ;

[0012] Where: , , are different from the three-dimensional coordinates The horizontal, vertical and vertical coordinates of the second microseismic source, For the The S wave of the first earthquake source reaches The time of the microseismic receiver, The S wave of the first earthquake source reaches The time of each microseismic receiver.

[0013] As a further solution of the present invention, the third equation group in the microseismic event processing host includes the first equation, the second equation, the third equation and the fourth equation. The left side of the first equation is the time difference between the P wave and the S wave of the microseismic event reaching the microseismic receiver and the sum of the spatial displacement of the crack expansion process. The right side introduces the residual to represent the deviation caused by the measurement error. The formula of the first equation is:

[0014] ;

[0015] Where: is the number of microseismic sources, is the mean time difference between the P-wave and S-wave of all microseismic events arriving at the same microseismic receiver, , , are the displacements of the microseismic source on the horizontal, longitudinal and vertical axes when the microseismic event occurs, , , are the time-space conversion coefficients of the horizontal, vertical and vertical axes, respectively. The error between the predicted crack extension path and earthquake source location and the actual situation.

[0016] As a further solution of the present invention, in the microseismic event processing host, the left side of the second equation in the third equation group is the coupling term of the time difference between the P wave and the S wave of the earthquake source in the horizontal axis direction reaching the microseismic receiver and the displacement of the earthquake source in the horizontal axis direction, plus the secondary contribution term of the earthquake source displacement in the horizontal axis direction to the crack development, plus the coupling term of the horizontal axis earthquake source displacement to the longitudinal axis crack expansion, plus the coupling term of the horizontal axis earthquake source displacement to the vertical axis crack expansion, and the right side of the second equation is the difference between the predicted results of the microseismic source and the crack expansion path in the horizontal axis direction and the actual microseismic observation data. The formula of the second equation is:

[0017] .

[0018] As a further solution of the present invention, in the microseismic event processing host, the left side of the third equation in the third equation group is the coupling term of the time difference between the P wave and the S wave of the microseismic event on the vertical axis reaching the microseismic receiver and the crack displacement extension, plus the coupling term of the earthquake source displacement in the horizontal axis direction and the crack extension in the vertical axis direction, plus the secondary contribution term of the crack in the vertical axis direction, plus the coupling term of the microseismic event longitudinal axis displacement to the vertical axis crack extension, and the right side of the third equation is the difference between the microseismic event displacement and crack extension prediction results on the vertical axis and the actual microseismic observation data. The formula of the third equation is:

[0019] .

[0020] As a further solution of the present invention, in the microseismic event processing host, the left side of the fourth equation in the third equation group is the coupling term of the time difference between the P wave and the S wave of the earthquake source on the vertical axis reaching the microseismic receiver and the expansion of the earthquake source displacement, plus the coupling term of the microseismic event displacement in the longitudinal axis and the expansion of the vertical axis crack, plus the nonlinear expansion term of the microseismic event in the vertical axis direction. The left side of the fourth equation is the error between the predicted result of the microseismic event displacement and the crack expansion in the vertical axis direction and the actual observed value. The formula of the fourth equation is:

[0021] .

[0022] As a further solution of the present invention, the process of solving the expansion path and final height of the water-conducting fracture zone by the microseismic event host through the third equation group of the first equation and the second equation is:

[0023] Step 1, locate the earthquake source and determine the starting point of crack expansion based on the first equation: use the least square method to substitute the observation data of at least but not limited to four microseismic receivers into the first equation, establish the earthquake source location equation, solve the three-dimensional coordinates of the earthquake source, use it as the starting point of crack expansion, and then use the stress intensity factor to evaluate the crack expansion conditions, and combine the crack expansion speed formula to determine the crack expansion speed;

[0024] Step 2, calculate the crack expansion difference and path based on the second equation: by using the known source location and microseismic receiver location, combined with the S-wave velocity, calculate the spatial difference between the sources and the arrival time difference of the P-wave and S-wave, determine the crack expansion path in different time periods, and obtain the crack expansion direction and path changes;

[0025] Step 3: Analyze the cumulative effect and nonlinear expansion of cracks based on the third equation group: By minimizing the residual, optimizing the time-space coupling coefficient in each direction, calculating the displacement change of the crack in each direction, further optimizing the time-space coupling coefficient in each direction, and combining the arrival time difference and spatial displacement of the P wave and S wave of the microseismic event to describe the spatial expansion and cumulative effect of the cracks in each direction;

[0026] Step 4, predict the height of the fracture zone: Based on the fracture zone height prediction formula, according to the fracture toughness, elastic model and principal stress of the rock formation, as well as the cumulative spatial displacement of the fracture extension path on each defense line obtained by solving the first equation, the second equation and the third equation, predict the final height of the fracture zone.

[0027] As a further solution of the present invention, the fracture zone height prediction formula in the microseismic event processing host is:

[0028] ;

[0029] Where: The predicted final height for the fracture zone; is the stress intensity factor of the rock formation, obtained through a three-point bending test of the rock formation sample; is the elastic modulus of the rock formation, obtained from the geological survey report; is the cumulative displacement of the crack in three-dimensional space obtained by solving the first equation, the second equation, and the third equation group; is the principal stress of the rock formation, obtained through stress monitoring equipment; is the crack expansion speed, ,in , are the spatial distance and time difference between the hypocenters of two microseismic events, respectively, which are calculated from the hypocenter locations of the microseismic sensor array monitoring data set and the known locations of the microseismic receivers; is the crack extension time, which is obtained by recording the timestamp and time difference of microseismic events.

[0030] As a further solution of the present invention, the anchor rod adjustment device dynamically adjusts the length and installation angle of the anchor rod according to the fracture zone development and cumulative effect data obtained by the microseismic event processing host, as well as the predicted final height of the fracture zone.

[0031] According to the predicted final height of the fracture zone, the length of the anchor rod ensures that the support structure can penetrate below the fracture zone and cover the extension range of the fracture. If the height of the fracture zone exceeds the length of the existing anchor rod, the length of the anchor rod is increased to extend it below the fracture zone to ensure sufficient anchoring force. If the fracture zone is smaller than the length of the existing anchor rod, the length of the anchor rod is shortened, but it is still necessary to ensure that the extension range of the fracture is covered. The cumulative effect of the fracture reflects the multi-level influence of the fracture extension. The length of the anchor rod is dynamically adjusted according to the cumulative effect of different levels to ensure that the anchor rod can support multiple layers of rock mass at the same time. Through the three-dimensional path of fracture extension provided by the microseismic event processing host, the anchor rod adjustment equipment analyzes the extension direction of the fracture. If 80% of the fracture extends in a certain direction, the anchor rod is installed in the opposite direction of the fracture extension direction to provide a reaction force to the fracture extension.

[0032] Compared with the prior art, the technical effect of the method proposed in the present invention is as follows: the present invention locates the microseismic source through the first equation, determines the starting point of the crack expansion, and then combines the stress intensity factor and the crack expansion speed formula to evaluate the crack expansion conditions, and uses the second equation to calculate the difference in the crack expansion path between different sources. The third set of equations further analyzes the spatial expansion and cumulative effect of the crack, and combines the stress field data to predict the final height of the crack zone. The anchor adjustment equipment dynamically adjusts the length and installation angle of the anchor according to these data to ensure that the support structure can effectively cover the crack expansion area and resist the further expansion of the crack through the reaction force. It not only solves the problem that the traditional material point method is difficult to accurately simulate the crack expansion path and cumulative effect, but also provides a real-time support adjustment basis for mine safety, effectively preventing and controlling the risk of mine water inrush. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of earthquake source positioning according to the present invention;

[0034] Figure 2 A microseismic monitoring digital twin platform for application of the method involved in the present invention;

[0035] Figure 3 A schematic diagram of data flow interaction of the system involved in the present invention;

[0036] Figure 4 This is a numerical analysis diagram of microseismic positioning of the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the present invention to clearly and completely describe the technical solutions in the present invention. Obviously, the described technical solutions are only part of the present invention, not all of it. Based on the content of the present invention, all other technical solutions obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] The material point method is used to simulate rock deformation and crack propagation during coal mining, predict the height of the water-conducting fracture zone, and record the arrival time difference of P waves and S waves generated by microseismic events in real time through the microseismic sensor array.

[0039] like Figures 1 to 4 As shown, the present invention proposes a method for predicting the height of water-conducting fracture zones in coal seam stratified fully mechanized caving mining, which collects microseismic signal data in real time and continuously through a microseismic sensor array, and transmits the acquired data to a microseismic event processing host, which performs P-wave and S-wave first arrival time recording, microseismic event positioning (such as Figure 4 As shown in the figure), magnitude calculation, energy calculation, event storage and seismic moment calculation are performed, while generating network analysis cloud map, stress analysis cloud map, displacement cloud map and fracture water inrush warning indicator display, and in order to improve the shortcomings of the traditional material point method, such as Figure 1 As shown, cracks are generated by rock stratum fracture, and the generated seismic waves are used for analysis and microseismic event positioning. The distance between the earthquake source and the microseismic receiver is determined based on the first equation, and the starting point of the crack expansion is located. The stress intensity factor is then used to evaluate the crack expansion conditions. Combined with the crack expansion velocity formula, the crack expansion velocity is determined. The second equation is used to simulate the relationship between the time difference between the P wave and S wave of different earthquake sources reaching the microseismic receiver and the crack expansion path in each direction, describe the crack expansion difference between multiple microseismic events, and determine the spatial change of the crack. Then, the third equation group is used to combine time, spatial position and wave propagation time difference. The crack expansion path and cumulative effect between the crack sources are described by the change of time difference and spatial position, and the expansion and cumulative effect of the crack between the earthquake sources are characterized. Combined with the real-time monitored stress field data and the physical properties of the mine rock formation, the fracture zone height prediction formula is used to predict the final height of the water-conducting fracture zone. The microseismic event processing host transmits the predicted final height of the water-conducting fracture zone to the anchor adjustment equipment.

[0040] like Figure 2 and Figure 3As shown, the method proposed in the present invention first generates conductive cracks based on the delamination water pressure, destroys the overburden, and generates microseismic events, and then transmits the collected data to the monitoring station through the microseismic sensor array, and then uses the microseismic event analysis host to synchronize time, analyze and process the data, and analyze the development of water-conducting cracks generated by the microseismic events based on the digital twin technology through network communication to obtain data that can solve the technical problems raised by the background technology, and synchronize and store the obtained data through the monitoring host, and then transmit it to the microseismic monitoring digital twin platform that can perform multi-source heterogeneous fusion and real-time mutual feedback analysis for cloud service and big data analysis, perform calculations and analysis on the software of the microseismic monitoring digital twin platform, and finally display it on the terminal computer, and regulate the anchor adjustment equipment based on the microseismic monitoring digital twin platform.

[0041] It should be noted that the microseismic source is located based on the first equation in the microseismic event processing host. The first equation is the microseismic event location equation. The equation substitutes the observation data of several microseismic receivers to construct several corresponding microseismic event location equations. The three-dimensional coordinates of the source are solved based on the least squares method by combining the time difference observed several times and the position of the microseismic receiver. The formula of the first equation is:

[0042] ;

[0043] Where: , are the indices of the microseismic event sources and microseismic receivers, , , They are respectively The horizontal, vertical and vertical coordinates of the microseismic source are: , , They are respectively The horizontal, vertical and vertical coordinates of the microseismic receivers are: The first microseismic event The P and S waves of the earthquake source reach the The time difference of the microseismic receivers is obtained by monitoring the microseismic sensor array. , They are the propagation speeds of P waves and S waves respectively, which are determined through geological exploration reports.

[0044] By using the microseismic event processing host to locate the microseismic source based on the first equation, multiple positioning equations are constructed using the observation data and arrival time difference of the microseismic receiver, and the least squares method is used to accurately solve the three-dimensional coordinates of the source. This method can accurately determine the starting point of the crack expansion, thereby providing accurate initial conditions for the subsequent crack expansion path and height prediction.

[0045] It should be noted that the microseismic event processing host obtains the expansion difference of the cracks generated by the microseismic event in different time periods based on the second equation. The distance between different seismic sources is solved by combining the known receiver coordinates and source coordinates with the propagation speed of the S wave. The formula of the second equation is:

[0046] ;

[0047] Where: , , are different from the three-dimensional coordinates The horizontal, vertical and vertical coordinates of the second microseismic source, For the The S wave of the first earthquake source reaches The time of the microseismic receiver, The S wave of the first earthquake source reaches The time of each microseismic receiver.

[0048] The microseismic event processing host obtains the difference in crack expansion caused by microseismic events based on the second equation, uses the known receiver coordinates and source coordinates, and combines the propagation speed of the S wave to calculate the spatial distance between different sources, thereby accurately describing the expansion path and speed of the cracks in different time periods, and can effectively capture the dynamic changes of the cracks in three-dimensional space, especially for complex mining scenarios with multiple layers of coal seams, where the expansion of cracks is usually nonlinear and multi-directional. Through the time difference and spatial position changes between different sources, the second equation can provide spatial distribution information of crack expansion, reveal how cracks accumulate and expand in different directions, and help predict the changing trend of the crack expansion path.

[0049] It should be noted that the third equation group in the microseismic event processing host includes the first equation, the second equation, the third equation and the fourth equation. The left side of the first equation is the time difference between the P wave and the S wave of the microseismic event reaching the microseismic receiver and the sum of the spatial displacement of the crack expansion process. The right side introduces the residual to represent the deviation caused by the measurement error. The formula of the first equation is:

[0050] ;

[0051] Where: is the number of microseismic sources, is the mean time difference between the P-wave and S-wave of all microseismic events arriving at the same microseismic receiver, , , are the displacements of the microseismic source on the horizontal, longitudinal and vertical axes when the microseismic event occurs, , , are the time-space conversion coefficients of the horizontal, vertical and vertical axes, respectively. The error between the predicted crack extension path and earthquake source location and the actual situation.

[0052] Through the third equation group in the microseismic event processing host, especially the first equation, the arrival time difference of the P wave and S wave of the microseismic event is combined with the spatial displacement of the crack expansion, and the residual is introduced to deal with the deviation caused by the measurement error, which can improve the prediction accuracy of the crack expansion path. This equation analyzes the spatiotemporal data of multiple microseismic sources, combines the time difference and the displacement in each direction, and provides the dynamic expansion information of the crack in three-dimensional space. By minimizing the residual, the error in the prediction model can be corrected and the calculation result of the crack expansion path can be optimized. This method is particularly critical in the description of the spatial expansion path and cumulative effect of the crack, which helps to solve the problem of crack expansion prediction error caused by measurement error and complex geological conditions. Ultimately, it provides the necessary high-precision data support for real-time prediction of crack expansion path, analysis of crack cumulative effect and accurate evaluation of crack zone height in mines.

[0053] It should be noted that in the microseismic event processing host, the left side of the second equation in the third equation group is the coupling term of the time difference between the P wave and S wave of the earthquake source in the horizontal direction reaching the microseismic receiver and the displacement of the earthquake source in the horizontal direction, plus the secondary contribution term of the earthquake source displacement in the horizontal direction to the development of the crack, plus the coupling term of the horizontal axis earthquake source displacement to the longitudinal axis crack extension, plus the coupling term of the horizontal axis earthquake source displacement to the vertical axis crack extension. The right side of the second equation is the difference between the predicted results of the microseismic source and the crack extension path in the horizontal direction and the actual microseismic observation data. The formula of the second equation is:

[0054] .

[0055] In the microseismic event processing host, the second equation in the third equation group fully describes the complex expansion behavior of cracks in three-dimensional space by coupling the time difference between the P wave and the S wave of the earthquake source in the transverse direction with the displacement in the transverse direction, and considering the interactive effect of the displacement in the transverse direction on the expansion of the longitudinal and vertical axes. By introducing the quadratic contribution term and the coupling term between different directions, the equation can capture the interaction between various directions during the crack expansion process. This multi-dimensional coupling relationship makes the prediction of crack expansion more accurate. The residual term on the right represents the difference between the predicted result and the actual observed data, which helps minimize the error and improve the model accuracy. This method provides an accurate mathematical model to solve the problem of crack expansion prediction deviation caused by the coupling of displacements in various directions, ensuring the accurate prediction of the crack expansion path.

[0056] It should be noted that in the microseismic event processing host, the left side of the third equation in the third equation group is the coupling term of the time difference between the P wave and the S wave of the microseismic event on the vertical axis reaching the microseismic receiver and the crack displacement extension, plus the coupling term of the displacement of the earthquake source in the horizontal axis and the crack extension in the vertical axis, plus the secondary contribution term of the crack in the vertical axis, plus the coupling term of the microseismic event vertical axis displacement to the vertical axis crack extension. The right side of the third equation is the difference between the predicted results of the microseismic event displacement and crack extension on the vertical axis and the actual microseismic observation data. The formula of the third equation is:

[0057] .

[0058] In the microseismic event processing host, the third equation of the third equation group fully captures the complex expansion behavior of the crack in the longitudinal direction by coupling the relationship between the arrival time difference of P waves and S waves in the longitudinal direction and the expansion of crack displacement, while considering the influence of the displacement in the transverse direction on the expansion of the longitudinal crack, as well as the coupling effect of the secondary contribution term in the longitudinal direction and the longitudinal displacement on the expansion of the vertical crack. The residual term is introduced on the right side of the equation to reflect the difference between the predicted results of crack expansion and the actual observed data, helping to optimize the prediction accuracy of the crack expansion path. This modeling of multiple coupling relationships can more accurately simulate the changes in the longitudinal direction during the crack expansion process, solve the problem of crack expansion prediction errors caused by the interaction of the various axis directions, and ensure accurate characterization of the crack expansion path and cumulative effects.

[0059] It should be noted that in the microseismic event processing host, the left side of the fourth equation in the third equation group is the coupling term of the time difference between the P wave and the S wave of the earthquake source on the vertical axis reaching the microseismic receiver and the expansion of the earthquake source displacement, plus the coupling term of the microseismic event displacement in the longitudinal axis and the expansion of the vertical axis crack, plus the nonlinear expansion term of the microseismic event in the vertical axis direction. The left side of the fourth equation is the error between the predicted results of the microseismic event displacement and crack expansion in the vertical axis direction and the actual observed value. The formula of the fourth equation is:

[0060] .

[0061] In the microseismic event processing host, the fourth equation of the third equation group can accurately describe the complex expansion dynamics of cracks in the vertical direction by coupling the arrival time difference of P waves and S waves at the earthquake source in the vertical axis with the displacement expansion in the vertical direction, and considering the interaction between the longitudinal axis and the vertical axis, combined with the nonlinear behavior of crack expansion in the vertical direction. The nonlinear expansion term on the left reflects the nonlinear cumulative effect of crack expansion in the vertical direction, and the residual term on the right represents the difference between the predicted results and the actual observed data. By minimizing this error term, the accuracy of the prediction model is optimized. The significance of this equation is that it solves the problem of predicting the nonlinear behavior of crack expansion in the vertical direction, ensures the accurate prediction of the crack expansion path and height in a complex stress environment, and improves the overall accuracy of crack expansion simulation.

[0062] It should be noted that the process of solving the expansion path and final height of the water-conducting fracture zone by the microseismic event host through the third equation group of the first equation and the second equation is:

[0063] Step 1, locate the earthquake source and determine the starting point of crack expansion based on the first equation: use the least square method to substitute the observation data of at least but not limited to four microseismic receivers into the first equation, establish the earthquake source location equation, solve the three-dimensional coordinates of the earthquake source, use it as the starting point of crack expansion, and then use the stress intensity factor to evaluate the crack expansion conditions, and combine the crack expansion speed formula to determine the crack expansion speed;

[0064] Step 2, calculate the crack expansion difference and path based on the second equation: by using the known source location and microseismic receiver location, combined with the S-wave velocity, calculate the spatial difference between the sources and the arrival time difference of the P-wave and S-wave, determine the crack expansion path in different time periods, and obtain the crack expansion direction and path changes;

[0065] Step 3: Analyze the cumulative effect and nonlinear expansion of cracks based on the third equation group: By minimizing the residual, optimizing the time-space coupling coefficient in each direction, calculating the displacement change of the crack in each direction, further optimizing the time-space coupling coefficient in each direction, and combining the arrival time difference and spatial displacement of the P wave and S wave of the microseismic event to describe the spatial expansion and cumulative effect of the cracks in each direction;

[0066] Step 4, predict the height of the fracture zone: Based on the fracture zone height prediction formula, according to the fracture toughness, elastic model and principal stress of the rock formation, as well as the cumulative spatial displacement of the fracture extension path on each defense line obtained by solving the first equation, the second equation and the third equation, predict the final height of the fracture zone.

[0067] It should be noted that the formula for predicting the height of the fracture zone in the microseismic event processing host is:

[0068] ;

[0069] Where: The predicted final height for the fracture zone; is the stress intensity factor of the rock formation, obtained through a three-point bending test of the rock formation sample; is the elastic modulus of the rock formation, obtained from the geological survey report; is the cumulative displacement of the crack in three-dimensional space obtained by solving the first equation, the second equation, and the third equation group; is the principal stress of the rock formation, obtained through stress monitoring equipment; is the crack expansion speed, ,in , are the spatial distance and time difference between the hypocenters of two microseismic events, respectively, which are calculated from the hypocenter locations of the microseismic sensor array monitoring data set and the known locations of the microseismic receivers; is the crack extension time, which is obtained by recording the timestamp and time difference of microseismic events.

[0070] The fracture zone height prediction formula provides a method for accurately predicting the height of the water-conducting fracture zone by comprehensively considering the three-dimensional spatial expansion of the fracture, the physical properties of the rock formation, and the dynamic expansion rate of the fracture. The critical stress intensity factor of crack extension is obtained through three-point bending test of rock samples, which reflects the ability of rock formation to resist crack extension; It is the elastic modulus of the rock formation, provided by the geological survey report, and characterizes the mechanical properties of the rock formation. Cumulative displacement term The first, second and third equation groups are solved by the microseismic event processing host, reflecting the expansion path of the crack in three-dimensional space. The principal stress of the rock formation is obtained in real time through stress monitoring equipment to ensure that the stress environment during crack expansion is accurately reflected. Produced by microseismic events , The calculation and expansion time further refine the cumulative effect of the cracks. The comprehensive application of this formula can not only accurately predict the final height of the crack zone, but also dynamically track the crack expansion process, solving the problem of insufficient accuracy of traditional methods in predicting crack height and improving the effectiveness of coal mining safety management.

[0071] It should be noted that the anchor adjustment device dynamically adjusts the length and installation angle of the anchor according to the fracture zone development and cumulative effect data obtained by the microseismic event processing host, as well as the predicted final height of the fracture zone. According to the predicted final height of the fracture zone, the anchor length ensures that the support structure can penetrate below the fracture zone and cover the extension range of the fracture. If the height of the fracture zone exceeds the length of the existing anchor, the length of the anchor is increased to extend below the fracture zone to ensure sufficient anchoring force. If the fracture zone is less than the length of the existing anchor, the length of the anchor is shortened, but it is still necessary to ensure that the extension range of the fracture is covered. The cumulative effect of the fracture reflects the multi-level influence of the fracture extension. The length of the anchor is dynamically adjusted according to the cumulative effect of different levels to ensure that the anchor can support multiple layers of rock mass at the same time. The anchor adjustment device analyzes the extension direction of the fracture through the three-dimensional path of fracture extension provided by the microseismic event processing host. If 80% of the fracture extends in a certain direction, the anchor is installed in the opposite direction of the fracture extension direction to provide a reaction force to the fracture extension.

[0072] The present invention locates the microseismic source through the first equation, determines the starting point of the crack expansion, and then combines the stress intensity factor and the crack expansion speed formula to evaluate the crack expansion conditions, and uses the second equation to calculate the difference in the crack expansion path between different sources. The third set of equations further analyzes the spatial expansion and cumulative effect of the crack, and combines the stress field data to predict the final height of the crack zone. The anchor adjustment equipment dynamically adjusts the length and installation angle of the anchor according to these data to ensure that the support structure can effectively cover the crack expansion area and resist the further expansion of the crack through the reaction force. It not only solves the problem that the traditional material point method is difficult to accurately simulate the crack expansion path and cumulative effect, but also provides a real-time support adjustment basis for mine safety, effectively preventing and controlling the risk of mine water inrush.

[0073] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

[0074] Finally: The above description is only an implementation mode of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for predicting the height of water-conducting fracture zones in coal seam stratified fully mechanized caving mining, which simulates the rock deformation and fracture expansion in coal seam mining based on the material point method, and predicts the height of water-conducting fracture zones, characterized in that: The microseismic sensor array is used to record the arrival time difference of P waves and S waves generated by microseismic events in real time. In the microseismic event processing host, the distance between the earthquake source and the microseismic receiver is determined based on the first equation to locate the starting point of the crack expansion. The stress intensity factor is then used to evaluate the crack expansion conditions. Combined with the crack expansion velocity formula, the crack expansion velocity is determined. The second equation is used to simulate the relationship between the time difference between the arrival of P waves and S waves from different earthquake sources at the microseismic receiver and the crack expansion path in each direction, describe the crack expansion differences between multiple microseismic events, and determine the spatial variation of the crack. The third equation group is then used to combine time, spatial position and wave propagation time difference. The crack expansion path and cumulative effect between the crack sources are described through the change of time difference and spatial position, and the expansion and cumulative effect of the crack between the earthquake sources are characterized. Combined with the real-time monitored stress field data and the physical properties of the mine rock formation, the final height of the water-conducting fracture zone is predicted using the fracture zone height prediction formula. The microseismic event processing host transmits the predicted final height of the water-conducting fracture zone to the anchor adjustment equipment.

2. The method for predicting the height of water-conducting fracture zones in coal seam stratified fully mechanized caving mining according to claim 1 is characterized in that: The microseismic event processing host performs microseismic source location based on the first equation, and the formula of the first equation is: ； Where: , are the indices of the microseismic event sources and microseismic receivers, , , They are respectively The horizontal, vertical and vertical coordinates of the microseismic source are: , , They are respectively The horizontal, vertical and vertical coordinates of the microseismic receivers are: The first microseismic event The P and S waves of the earthquake source reach the The time difference of the microseismic receivers is obtained by monitoring the microseismic sensor array. , They are the propagation speeds of P waves and S waves respectively, which are determined through geological exploration reports.

3. The method for predicting the height of water-conducting fracture zones in coal seam stratified fully mechanized caving mining according to claim 2 is characterized in that: In the microseismic event processing host, the expansion difference of the cracks generated by the microseismic event in different time periods is obtained based on the second equation. The formula of the second equation is: ； Where: , , are different from the three-dimensional coordinates The horizontal, vertical and vertical coordinates of the second microseismic source, For the The S wave of the first earthquake source reaches The time of the microseismic receiver, The S wave of the first earthquake source reaches The time of each microseismic receiver.

4. A method for predicting the height of water-conducting fracture zones in coal seam stratified fully mechanized caving mining according to claim 3, characterized in that: The third equation group in the microseismic event processing host includes the first equation, the second equation, the third equation and the fourth equation. The formula of the first equation of the microseismic receiver is: ； Where: is the number of microseismic sources, is the mean time difference between the P-wave and S-wave of all microseismic events arriving at the same microseismic receiver, , , are the displacements of the microseismic source on the horizontal, longitudinal and vertical axes when the microseismic event occurs, , , are the time-space conversion coefficients of the horizontal, vertical and vertical axes, respectively. The error between the predicted crack extension path and earthquake source location and the actual situation.

5. A method for predicting the height of water-conducting fracture zones in coal seam stratified fully mechanized caving mining according to claim 4, characterized in that: The formula of the second equation for microseismic receiver is: 。 6. A method for predicting the height of water-conducting fracture zones in coal seam stratified fully mechanized caving mining according to claim 4, characterized in that: The formula of the third equation is: 。 7. A method for predicting the height of water-conducting fracture zones in coal seam stratified fully mechanized caving mining according to claim 4, characterized in that: The formula of the fourth equation is: 。 8. The method for predicting the height of water-conducting fracture zones in coal seam stratified fully mechanized caving mining according to claim 4 is characterized in that: The process of solving the expansion path and final height of the water-conducting fracture zone by the microseismic event host through the first equation, the second equation and the third equation group is as follows: Step 1, locate the earthquake source and determine the starting point of crack expansion based on the first equation: use the least square method to substitute the observation data of at least but not limited to four microseismic receivers into the first equation, establish the earthquake source location equation, solve the three-dimensional coordinates of the earthquake source, use it as the starting point of crack expansion, and then use the stress intensity factor to evaluate the crack expansion conditions, and combine the crack expansion speed formula to determine the crack expansion speed; Step 2, calculate the crack expansion difference and path based on the second equation: by using the known source location and microseismic receiver location, combined with the S-wave velocity, calculate the spatial difference between the sources and the arrival time difference of the P-wave and S-wave, determine the crack expansion path in different time periods, and obtain the crack expansion direction and path changes; Step 3: Analyze the cumulative effect and nonlinear expansion of cracks based on the third equation group: By minimizing the residual, optimizing the time-space coupling coefficient in each direction, calculating the displacement change of the crack in each direction, further optimizing the time-space coupling coefficient in each direction, and combining the arrival time difference and spatial displacement of the P wave and S wave of the microseismic event to describe the spatial expansion and cumulative effect of the cracks in each direction; Step 4, predict the height of the fracture zone: Based on the fracture zone height prediction formula, according to the fracture toughness, elastic model and principal stress of the rock formation, as well as the cumulative spatial displacement of the fracture extension path on each defense line obtained by solving the first equation, the second equation and the third equation, predict the final height of the fracture zone.

9. A method for predicting the height of water-conducting fracture zones in coal seam stratified fully mechanized caving mining according to claim 4, characterized in that: The fracture zone height prediction formula is: ； Where: The predicted final height for the fracture zone; is the stress intensity factor of the rock formation, obtained through a three-point bending test of the rock formation sample; is the elastic modulus of the rock formation, obtained from the geological survey report; is the cumulative displacement of the crack in three-dimensional space obtained by solving the first equation, the second equation, and the third equation group; is the principal stress of the rock formation, obtained through stress monitoring equipment; is the crack expansion speed, ,in , are the spatial distance and time difference between the hypocenters of two microseismic events, respectively, which are calculated from the hypocenter locations of the microseismic sensor array monitoring data set and the known locations of the microseismic receivers; is the crack extension time, which is obtained by recording the timestamp and time difference of microseismic events.

10. A method for predicting the height of water-conducting fracture zones in coal seam stratified fully mechanized caving mining according to claim 9, characterized in that: The anchor rod adjustment device dynamically adjusts the length and installation angle of the anchor rod according to the fracture zone development and cumulative effect data obtained by the microseismic event processing host, as well as the predicted final height of the fracture zone.

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