A tomographic processing method based on drilling observation of mining areas

Abstract

The present invention discloses a tomographic processing method for mining areas based on borehole observation. Utilizing the principle that cosmic ray muons lose intensity after passing through matter, muon detectors are arranged in boreholes to observe muon intensity underground, thereby obtaining information on the distribution of material opacity at various locations underground with respect to zenith angle and azimuth. Through multi-borehole and multi-position depth measurements, a cross-coverage of muon observations of the observation area is formed, thereby establishing a density inversion solution equation, and ultimately solving the accurate three-dimensional density structure under the surface. The muon source used in the present invention is a natural source, and muons do not damage the observed object. The observable depth can reach up to a depth of one kilometer, and the existing boreholes in the mining area are fully utilized to provide a safety detection function, thereby ensuring safe production.

Description

Technical Field

[0001] The present invention belongs to mine geological exploration and mine goaf detection technology, and relates to a mine tomography method based on borehole muon imaging. Background Art

[0002] As a major player in mineral resource mining and utilization, China has invested enormous sums in the development and utilization of these resources. Maintaining the continued, efficient, and safe development and utilization of these resources is a major issue. Furthermore, with the development of these resources, an increasing number of abandoned mines have emerged. The geological structures surrounding these mines, influenced by factors such as the meteorological environment, hydrological conditions, topography, and geological structure, are prone to deformation and collapse, posing significant safety risks to the safe mining of mineral resources and the post-processing of tailings and waste. In severe cases, excessive stress can cause cracks in the ground, creating voids, which in turn can cause deformation of foundations and buildings, posing safety risks.

[0003] To locate and address weak zones and voids in underground mines, various detection methods have emerged. Conventional methods include resistivity, radar, and seismic refraction. Resistivity methods suffer from multi-solution issues: the physical field anomaly is not unique to the geological body. Different geological bodies with the same electrical and physical properties may manifest as the same anomalous electrical layer. Similarly, the same geological layer may manifest as several different anomalous electrical layers due to differences in moisture, particle size, and other factors. This greatly complicates data analysis and interpretation. Ground-penetrating radar (GPR) has limitations in terms of detection depth and the ability to accurately locate and assess the development of weak zones and voids. Seismic refraction methods also have limitations in their inability to detect relatively low-velocity strata beneath high-velocity strata. Furthermore, greater depths require larger survey sites and higher seismic excitation energy. Therefore, there is an urgent need to develop new methods for detecting weak zones and voids in mining areas to achieve this goal. Summary of the Invention

[0004] In response to the deficiencies in the prior art, the present invention aims to provide a tomography processing method for a mining area based on borehole observation. By placing a cosmic ray muon receiving device below the surface along the borehole, the flux information of cosmic rays after passing through the stratum material is detected, thereby inverting and calculating the density length distribution information at different geological positions of the mine at the observation position of this borehole; according to the way the cosmic ray receiving device moves up and down in the borehole, the density length distribution information at different depths in the mining area at this borehole position can be detected; by completing muon observation tests at multiple borehole positions and multiple borehole depths, the underground density structure of the entire observation area of ​​the mining area is given, and underground weak areas and voids are discovered in time, thereby avoiding accidents and protecting people's lives and property.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A tomographic processing method for a mining area based on borehole observation comprises the following steps:

[0007] Step 1: Use a high-precision GPS positioning system to obtain a positioning base point (X0, Y0, Z0) above the surface of the coal mining area to be measured. This will serve as a reference point for the subsequent drilling location and the muon detector position.

[0008] Step 2: Based on the actual needs of the project, make full use of existing drill holes, determine the drill hole locations required for detection in the entire detection area, and drill new holes as needed;

[0009] Step 3: Place muon detectors in the borehole and ensure that the detection range of the muon detectors can cross-cover the detection area;

[0010] Step 4: When the observation begins, the muon detector is lowered along the drilling line to the required observation depth and then turned on. The muon detector records the current position information into the data file. At the same time, the muon detector begins to receive muons from various zenith angles and azimuth directions, and records the incident position (x in ,y in ,z in ) and the emission position (x out ,y out ,z out ), complete the muon information detection at this location of the borehole;

[0011] Step 5: Change the depth of the muon detector by using the hoisting rope and repeat the measurement process of step 4 to complete the muon information observation at different depths of this borehole;

[0012] Step 6: After completing the muon information observation at different depths in one borehole, repeat steps 4 and 5 to perform muon information observation at different depths in other boreholes until the muon information observation is completed in all boreholes.

[0013] Step 7: Summarize and process the collected muon information data according to the muon detector at each detection position (X i ,Y i ,Z i ) at the muon incident position (x in ,y in ,z in ) and the emission position (x out ,y out ,z out ), and obtain the detection position in the borehole (X i ,Y i ,Z i) with the distribution of the number of muons at zenith angle and azimuth angle

[0014] Step 8, according to step 7 Based on the distribution information of cosmic ray muon flux at sea level with zenith angle and azimuth Calculate the muon attenuation information at each detection position in the borehole Then, based on the public data, the distribution information of the opacity information under the surface with the zenith angle and azimuth angle can be obtained by the attenuation information ratio. i ;

[0015] Step 9, the RL i and the internal density structure ρ of the area to be measured j The linear equations are as follows:

[0016]

[0017] Among them, RL i L is the product of the density of the muon observation data in the test area at the i-th specific azimuth and zenith angle × length, ij The length of the jth grid penetrated by the product of density × length; according to the sizes of the detection area area_X, area_Y, area_Z, set the sizes of the solution grid grid_x, grid_y, grid_z, and obtain the number of solution grids num_x, num_y, num_z; the number of grid density parameters solved j = num_x × num_y × num_z;

[0018] Based on the above formula, the linear inversion equations required for muon imaging can be obtained as follows:

[0019]

[0020] Step 10: Since the muon track is a straight line, it only passes through a very small area of ​​the detection area, so the matrix It is a large sparse matrix. The linear equation of the sparse matrix coefficients is solved by the MATLAB built-in function lsqr least squares iterative algorithm. j , and obtain the accurate three-dimensional density structure of the subsurface.

[0021] The present invention also includes the following technical features:

[0022] Specifically, in step 6, one muon detector can be used to work continuously, or the same muon detector can be used to work simultaneously to complete the muon information observation of all boreholes.

[0023] Specifically, in step 7, according to the muon incident position (xin ,y in ,z in ) and the emission position (x out ,y out ,z out ) Calculate the zenith angle zenithθ and azimuth angle The formula is: where x = x in -x out ;y=y in -y out ; z=z in -z out .

[0024] Specifically, in step 9, num_x=area_X / grid_x; num_y=area_Y / grid_y;

[0025] num_z=area_Z / grid_z.

[0026] Compared with the prior art, the present invention has the following technical effects:

[0027] This invention utilizes boreholes in mining areas to deploy cosmic ray muon detectors. By observing cosmic ray muons, the inversion of the subsurface density structure in the mining area is achieved. This allows the identification of potential density weak zones and goafs beneath the mining area, providing timely information for decision-making and preventing the further development of density weak zones and goafs, which could lead to production safety accidents. The muon source used in this invention is natural, harmless to the observed objects, and can be observed up to a depth of one kilometer. The invention also fully utilizes existing boreholes in the mining area, providing a safety detection function to ensure safe production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the detector layout;

[0029] Figure 2 This is a side view of the muon detector;

[0030] Figure 3 This is a top-down diagram of the muon detector;

[0031] Figure 4 is the distribution relationship between density muon attenuation muonratio and density length at different zenith angles;

[0032] Figure 5 The left picture in the middle is the geological density model, and the right picture is the inversion result of the present invention. DETAILED DESCRIPTION

[0033] The present invention proposes a mining area tomography method based on borehole muon imaging. Utilizing the principle that cosmic ray muons lose intensity after passing through matter, muon detectors are arranged in boreholes to observe muon intensity underground, thereby obtaining distribution information of material opacity at various positions underground as a function of zenith angle and azimuth angle. Through multi-borehole and multi-position depth measurements, cross-coverage of muon observations in the observation area is achieved, thereby establishing a density inversion solution equation and ultimately solving the precise three-dimensional density structure beneath the surface.

[0034] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0035] Example 1:

[0036] This embodiment provides a tomographic processing method for a mining area based on drilling observation, comprising the following steps:

[0037] Step 1: Use a high-precision GPS positioning system to obtain a positioning base point (X0, Y0, Z0) above the surface of the coal mining area to be measured. This will serve as a reference point for the subsequent drilling location and the muon detector position.

[0038] Specifically, in this embodiment, the ground surface of the mining area to be observed is first reached, and a high-precision GPS positioning system is used to obtain a positioning base point (X0, Y0, Z0) as a reference point for the subsequent drilling position and the position of the cosmic ray detection device; a position-sensitive cosmic ray muon detector to be measured is selected;

[0039] Step 2: Based on the actual needs of the project, make full use of existing drill holes, determine the drill hole locations required for detection in the entire detection area, and drill new holes as needed;

[0040] Step 3: Place muon detectors in the borehole and ensure that the detection range of the muon detectors can cross-cover the detection area; Figure 1 The figure shows the layout of the muon detectors. The detection ranges of the various muon detectors overlap and cover the detection area.

[0041] Specifically, the cosmic ray muon receiving device required for observation is called a muon detector, such as Figure 2 and Figure 3As shown, its overall structure is cylindrical and has the function of detecting the position of muon tracks. Muon detectors of different diameters can be selected according to the diameter of the borehole. The muon detector has its own power supply, which can record the position information of the muon track and save it as a data file. At the same time, the muon detector also has the function of transmitting data back to the ground. It can transmit data in real time or at fixed time intervals according to the settings. The detector layout plan should be laid out according to the density of the borehole and the accuracy requirements of the tomographic processing. The layout principle is that the detection range of multiple detectors must be cross-covered for the observation area. (This can be achieved by using one detector to achieve cross-coverage of the observation area through multiple observations, or by using multiple detectors to achieve cross-coverage of the observation area through simultaneous observations.)

[0042] Step 4: When the observation begins, the muon detector is lowered along the drilling hole to the required observation depth along with the hoisting rope and then turned on. The muon detector will send the current position information (X i ,Y i ,Z i ) is recorded in the data file, and at the same time the muon detector begins to receive muons from various zenith angles and azimuth directions, and records the incident position of the received muons (x in ,y in ,z in ) and the emission position (x out ,y out ,z out ), complete the muon information at this location of this borehole detection;

[0043] Specifically, after a period of observation (depending on the depth of the muon detector from the surface, the required observation time varies from several minutes to several hours), when enough muons are accumulated, the drilling position (X i ,Y i ,Z i ) detection;

[0044] Step 5: Change the depth of the muon detector by using the hoisting rope and repeat the measurement process of step 4 to complete the muon information observation at different depths of this borehole;

[0045] Step 6: After completing the muon information observation at different depths in one borehole, repeat steps 4 and 5 to perform muon information observation at different depths in other boreholes until the observation of all boreholes is completed;

[0046] Specifically, this process can use one muon detector for continuous operation, or use the same muon detector for simultaneous operation to improve efficiency.

[0047] Step 7: After the above steps, the collected muon information data is aggregated and processed according to the detection position (X i ,Y i ,Z i ) at the muon incident position (x in ,y in ,z in ) and the emission position (x out ,y out ,z out ), and obtain the detection position in the borehole (X i ,Y i ,Z i ) distribution of muon number with zenith angle and azimuth

[0048] According to the muon incident position (x in ,y in ,z in ) and the emission position (x out ,y out ,z out ) Calculate the zenith angle zenithθ and azimuth angle The formula is: where x = x in -x out ;y=y in -y out ; z=z in -z out ;

[0049] Step 8: Muon flux distribution information at the downhole muon detection position obtained in step 7 Based on the distribution information of cosmic ray muon flux at sea level with zenith angle and azimuth The muon attenuation information at each detection position in the borehole is calculated. Then, based on the public data, the distribution information RL of the subsurface opacity (density length RL) with the zenith angle and azimuth angle can be obtained by using the attenuation information ratio. (zenith，azimuth) ;

[0050] Step 9: Set the sizes of the solution grids grid_x, grid_y, and grid_z according to the sizes of the detection area area_X, area_Y, and area_Z, and obtain the number of solution grids num_x, num_y, and num_z; where num_x = area_X / grid_x; num_y = area_Y / grid_y; and num_z = area_Z / grid_z.

[0051] The number of grid density parameters to be solved j = num_x × num_y × num_z; Muon observation data RL i(zenith，azimuth) and the internal density structure ρ of the area to be measured j The linear equations can be expressed as follows:

[0052]

[0053] Among them, RL i L is the product of the density of the muon observation data in the test area at the i-th specific azimuth and zenith angle × length, ij is the length of the jth grid penetrated by the product of the ith density × length. Based on the above formula, the linear inversion equations required for muon imaging can be obtained as follows:

[0054]

[0055] Step 10: Since the muon track is a straight line, it only passes through a very small area of ​​the detection area, so the matrix Most of the elements in are 0, which is a large sparse matrix. Matlab has a relatively mature solution for the linear equation of sparse matrix coefficients. The lsqr least squares iterative algorithm built into Matlab can be used to solve ρ j , and obtain the accurate three-dimensional density structure of the subsurface. Figure 5 In the figure, the left picture is the geological density model, and the right picture is the inversion result of this scheme. The low-density anomaly area is marked in the figure.

Claims

1. A tomographic processing method based on drilling observation of mining areas, characterized in that: The following steps are involved: Step 1: Use a high-precision GPS positioning system to obtain a positioning base point (X0, Y0, Z0) above the surface of the coal mining area to be measured. This will serve as a reference point for the subsequent drilling location and the muon detector position. Step 2: Based on the actual needs of the project, make full use of existing drill holes, determine the drill hole locations required for detection in the entire detection area, and drill new holes as needed; Step 3: Place muon detectors in the borehole and ensure that the detection range of the muon detectors can cross-cover the detection area; Step 4: When the observation begins, the muon detector is lowered along the drilling line to the required observation depth and then turned on. The muon detector records the current position information into the data file. At the same time, the muon detector begins to receive muons from various zenith angles and azimuth directions, and records the incident position (x in ,y in ,z in ) and the emission position (x out ,y out ,z out ), complete the muon information detection at this location of the borehole; Step 5: Change the depth of the muon detector by using the hoisting rope and repeat the measurement process of step 4 to complete the muon information observation at different depths of this borehole; Step 6: After completing the muon information observation at different depths in one borehole, repeat steps 4 and 5 to perform muon information observation at different depths in other boreholes until the muon information observation is completed in all boreholes. Step 7: Summarize and process the collected muon information data according to the muon detector at each detection position (X i ,Y i ,Z i ) at the muon incident position (x in ,y in ,z in ) and the emission position (x out ,y out ,z out ), and obtain the detection position in the borehole (X i ,Y i ,Z i ) with the distribution of the number of muons at zenith angle and azimuth angle Step 8, according to step 7 Based on the distribution information of cosmic ray muon flux at sea level with zenith angle and azimuth Calculate the muon attenuation information at each detection position in the borehole Then, based on the public data, the distribution information of the opacity information under the surface with the zenith angle and azimuth angle can be obtained by the attenuation information ratio. i ; Step 9, the RL i and the internal density structure ρ of the area to be measured j The linear equations are as follows: Among them, RL i L is the product of the density of the muon observation data in the test area at the i-th specific azimuth and zenith angle × length, ij The length of the jth grid penetrated by the product of density × length; according to the sizes of the detection area area_X, area_Y, area_Z, set the sizes of the solution grid grid_x, grid_y, grid_z, and obtain the number of solution grids num_x, num_y, num_z; the number of grid density parameters solved j = num_x × num_y × num_z; Based on the above formula, the linear inversion equations required for muon imaging can be obtained as follows: Step 10: Since the muon track is a straight line, it only passes through a very small area of ​​the detection area, so the matrix It is a large sparse matrix. The linear equation of the sparse matrix coefficients is solved by the MATLAB built-in function lsqr least squares iterative algorithm. j , and obtain the accurate three-dimensional density structure of the subsurface.

2. The method for tomographic processing of mining areas based on drilling observation according to claim 1, characterized in that: In step 6, one muon detector may be used for continuous operation, or the same muon detector may be used for simultaneous operation to complete muon information observation of all boreholes.

3. The method for tomographic processing of mining areas based on drilling observation according to claim 1, characterized in that: In step 7, the muon incident position (x in ,y in ,z in ) and the emission position (x out ,y out ,z out ) Calculate the zenith angle zenithθ and azimuth angle The formula is: where x = x in -x out ;y=y in -y out ; z=z in -z out .

4. The method for tomography treatment of mining areas based on drilling observation according to claim 1, characterized in that: In step 9, num_x=area_X / grid_x; num_y=area_Y / grid_y; num_z=area_Z / grid_z.

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