A method for underground geological mapping to predict coal seam structural zones

Abstract

The present invention discloses a method for underground geological mapping to predict coal seam structural zones, belonging to the technical field of geological exploration. S1: Arrange the coal mining face, roadway, and the longitudinal direction of the coal seam as the X, Y, and Z axes respectively; S2: Set a number of observation planes along the roadway direction, with intervals in the X-axis direction between the observation planes; S3: Search for the coal seams in the structural zones along the working face and the roadway respectively, record the geological characteristics of the coal seams in the structural zones, observe the key points of the coal seams in the structural zones in the X, Y, and Z directions, and mark them on the geographical coordinate map; S4: Conduct structural connection, and connect the geological bodies with the same structural characteristics with lines; S5: Select an appropriate scale to draw a geological profile; S6: Conduct a systematic analysis of the geological characteristics within and between all the observation planes to generate a geological model, analyze and verify the geological model, and predict the spatial distribution of the coal seam structural zones. The method provided by the present invention makes the results more intuitive and accurate, and has a lower economic cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of geological exploration, and particularly relates to a method for underground geological mapping for predicting coal seam structural zones. Background Art

[0002] The gas occurrence law in strong structural zones is complex and changeable, and the mechanical properties of coal and rock are special, making it extremely prone to gas outbursts, which seriously restricts the safe and efficient production of coal mines. Strong geological structures can profoundly affect gas migration and outbursts by controlling gas occurrence. Therefore, coal and gas outbursts mainly occur in complex strong structural zones. In these areas, the in-situ stress is often concentrated, the coal seams are soft, the fracture connectivity is poor, and the permeability is extremely low. Not only is it easier to accumulate gas, but it also hinders gas desorption, greatly increasing the difficulty of gas outburst prevention and seriously affecting the safe and efficient production of coal mines. Therefore, geological exploration of coal seams in structural zones is particularly important.

[0003] Coal mine geological exploration is to master coal mine geological information, including the occurrence, thickness, quality, structure, etc. of coal seams, in order to guide the exploitation of mineral resources. When conducting coal mine geological exploration, three-dimensional seismic exploration, geophysical logging, and mine seismic prospecting technology means are usually used to detect the geological conditions of the mining area. However, these methods have great limitations, such as complex data interpretation, high cost, and low accuracy, making it difficult to ensure the safe construction of the mining face. Therefore, there is an urgent need for a method for underground geological mapping for predicting coal seam structural zones to achieve the prediction of coal seams in structural zones. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for underground geological mapping for predicting coal seam structural zones, which solves the problems of large limitations, complex data interpretation, high cost, and low accuracy existing in the prior art during coal mine geological exploration.

[0005] To achieve the above purpose, the present invention provides a method for underground geological mapping for predicting coal seam structural zones, including the following steps:

[0006] S1. Arrange the coal mining face, roadway, and the longitudinal direction of the coal seam as the X, Y, and Z axes respectively to represent the three-dimensional spatial position of geological mapping;

[0007] S2. Set a number of observation planes along the Y-axis direction of the roadway, and the observation planes are spaced at intervals in the X-axis direction;

[0008] S3. Search for coal seams in structural zones along the X direction of the working face and the Y direction of the roadway respectively, record the structural types, attitudes, coal body structures, coal seam structures, fracture systems, macroscopic coal and rock types, parting, and geological characteristics of the roof and floor of the coal seams in structural zones, observe the key points of the coal seams in structural zones in the X, Y, and Z directions, and mark them on the geographical coordinate map;

[0009] S4. Conduct structural connection by connecting geological bodies with the same structural features with lines, where the structural features include folds, faults, and collapse columns; thereby predicting the geological features of the structural zones within each independent observation plane and between various observation planes.

[0010] S5. Select an appropriate scale to draw a geological cross-section. The selection of the scale depends on the spacing of the key points of the coal seam in the structural zone; the smaller the scale, the more detailed the geological mapping, and the more intuitively the distribution and structural features of the geological bodies can be shown.

[0011] S6. After completing the structural connection, conduct a systematic analysis of the geological features within and between all observation planes, comprehensively consider the relationships between various structural features, generate a geological model, analyze and verify the geological model, and predict the spatial distribution of folds, faults, and collapse columns in the coal seam structural zone. Through the accurate prediction of the structural zone, it has important theoretical significance for clarifying the influence mechanism of strong structural zones on gas occurrence and gas outburst. At the same time, it provides technical support for guiding the identification and prediction of structural coal seams in the future main mining panels of the mine and timely eliminating potential gas outburst hazards.

[0012] Preferably, the method of mine geological mapping is used to record the key points of the coal seam in the structural zone, including the dip angle of the fault, the throw of the fault, the long axis and short axis lengths of the collapse column, the axis trend of the fold, and the dip angle and range of the smooth surface.

[0013] Preferably, the fold in S4 is specifically the axis trend, dip angle, fold type, and shape of the fold on the observation plane in the direction of the coal mining face and roadway; in specific operation, the folds showing the same or similar characteristics are connected.

[0014] Preferably, the fault in S4 is specifically the fault trend, fault dip angle, fault dip direction on the observation plane in the direction of the coal mining face and roadway, as well as the filling in the fault and the occurrence of coal and rock; in specific operation, the faults with the same or similar faults on the same observation plane or between different observation planes are connected. For the fault structure that is only exposed on one side of the observation plane, use the existing geological data and regional geological laws to determine the location and extension range of the structure, specifically as follows:

[0015] S41. According to the characteristics of the L1 joint, determine the position of the starting point of the L1 joint and measure the width of the L1 joint zone; specifically: The roadway L intersects the fault F obliquely at point O, the fault throw at point O is H1, the width of the L1 joint zone measured along the roadway direction is OA, and a perpendicular line AA' is drawn from point A to the fault plane to obtain the width of the L1 joint zone in the direction perpendicular to the fault plane.

[0016] S42. Measure the azimuth, dip angle, fault throw of the fault plane, as well as the azimuth and gradient of the roadway.

[0017] S43. Convert the measured roadway distance into the distance in the direction perpendicular to the fault plane. The specific expression is as follows:

[0018] B section = B' section · sinωsinβcosα (1)

[0019] In the formula, B section is the width of the L1 joint zone in the direction perpendicular to the fault plane; B' section is the width of the L1 joint zone measured in the roadway; ω is the included angle between the roadway azimuth and the fault plane strike; β is the fault plane dip angle; α is the roadway gradient;

[0020] S44. Substitute the width B section of the L1 joint zone in the direction perpendicular to the fault plane into formula (1) to obtain the fault throw. The fault throws at points O and A' in its strike direction are H1 and H2 respectively. According to the fault throws of these two points and the distance d between them, obtain the attenuation coefficient of the fault and calculate the extension range of the fault. The specific expression is as follows:

[0021]

[0022] Preferably, the subsidence column in S4 is specifically to judge the position of the subsidence column according to the dip direction and dip angle of the rock fracture surface on the observation surface, the rock layer properties, and the groundwater conditions. Judge the size and range of the subsidence column according to the lengths of the long axis and short axis of the exposed subsidence column and the size of the column wall angle. Directly predict and draw the map for the one with a small range. Connect the subsidence columns with the same or similar characteristics on the same observation surface or different observation surfaces, and draw a connecting line to illustrate that the ranges of these subsidence columns are larger and may span different observation surfaces.

[0023] Preferably, in S5, according to the spacing of the key points of the coal seam in the structural belt, the selection of the scale includes the following three situations:

[0024] Situation 1: When the spacing of the key points of the coal seam in the structural belt is not greater than 10 m, select a scale of 1:1000;

[0025] Situation 2: When the spacing of the key points of the coal seam in the structural belt is between 10 m and 20 m, select a scale of 1:2000;

[0026] Situation 3: When the spacing of the key points of the coal seam in the structural belt is not less than 20 m, select a scale of 1:5000.

[0027] Therefore, the underground geological mapping method for predicting the coal seam structural belt adopted by the present invention has the following beneficial effects:

[0028] (1) Different from the traditional field geological mapping technology, this invention applies the geological mapping technology to the coal seam underground in the mine. By observing and recording the geological features on site, it is finally presented in the form of a three-dimensional distribution geological map. The method is reliable and the result is intuitive and accurate;

[0029] (2) The invention divides the coal seam into several observation planes. By connecting the same or similar structural features appearing on the observation planes, not only can geological bodies and geological phenomena be presented on the map in the form of three-dimensional graphics, making geological information more intuitive, clear, and easy to understand and analyze, but also geological features such as geological structures, faults, and lithological changes can be clearly displayed, which helps in the prediction of coal seam structural zones.

[0030] (3) The invention utilizes existing conditions in the mining area such as coal mining faces, roadways, and the longitudinal direction of the coal seam to establish observation planes, observes the key points of the coal seam in the structural zone and marks them on the geographical coordinate map, and finally forms a three-dimensional distribution geological map of the coal seam in the structural zone to achieve the prediction of the coal seam in the structural zone. This method has a lower economic cost and is more conducive to environmental sustainable development.

[0031] (4) As a brand-new method for geological exploration and prediction inside the coal seam, the invention can complement information with traditional methods such as three-dimensional seismic exploration, geophysical logging, and cross-measurement technology means, verify geological information from multiple angles, and make the conclusion more accurate and reliable.

[0032] The technical solution of the present invention will be further described in detail below through the accompanying drawings and embodiments. Description of the Drawings

[0033] Figure 1 is the overall flow chart of a mine geological mapping method for predicting coal seam structural zones of the present invention;

[0034] Figure 2 is the layout diagram of mine structural geological mapping of an embodiment of the present invention;

[0035] Figure 3 is the prediction diagram of mine structural connection of an embodiment of the present invention;

[0036] Figure 4 is the schematic diagram of the normal distance in the direction perpendicular to the fault plane of an embodiment of the present invention. Detailed Embodiments

[0037] The following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the present invention claimed, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0038] Please refer to Figures 1-4 , a mine geological mapping method for predicting coal seam structural zones, comprising the following steps:

[0039] S1. Arrange the coal mining face, roadway, and the longitudinal direction of the coal seam as the X, Y, and Z axes respectively to represent the three-dimensional spatial position of the geological mapping.

[0040] S2. Set up several observation planes along the Y-axis direction of the roadway, with intervals in the X-axis direction between the observation planes.

[0041] S3. Search for the coal seams in the tectonic zones along the X direction of the working face and the Y direction of the roadway respectively, record the tectonic types, attitudes, coal body structures, coal seam structures, fracture systems, macroscopic coal-rock types, parting, and geological characteristics of the roof and floor of the coal seams in the tectonic zones, observe the key points of the coal seams in the tectonic zones in the X, Y, and Z directions, and mark them on the geographical coordinate map; use the method of mine geological mapping to record the key points of the coal seams in the tectonic zones, including the fault dip angle, fault throw, the major and minor axis lengths of the collapse column, the axis trend of the fold, and the dip angle and range of the smooth surface.

[0042] S4. Conduct tectonic connection, connect the geological bodies with the same tectonic characteristics with lines, where the tectonic characteristics include folds, faults, and collapse columns; thus predict the geological characteristics of the tectonic zones within each independent observation plane and between the observation planes; among them, the fold is specifically the axis trend, dip angle, fold type, and form of the fold on the observation plane in the directions of the coal mining face and the roadway; in specific operation, connect the folds showing the same or similar characteristics. The fault is specifically the fault trend, fault dip angle, fault dip direction on the observation plane in the directions of the coal mining face and the roadway, as well as the filling in the fault and the attitude of the coal and rock; in specific operation, connect the faults with the same or similar faults on the same observation plane or between different observation planes. For the fault structure that is only exposed on one side of the observation plane, use the existing geological data and regional geological laws to determine the position and extension range of the structure. Garbiel believes that the width of the fault influence zone, like the fault throw, can be used as an index of the energy consumed during the formation and development of the fault. The larger the fault throw, the larger the width of its influence zone; the smaller the fault throw, the smaller the width of its influence zone. Therefore, there is a certain mathematical relationship between the fault throw and the width of the fault influence zone, which is as follows:

[0043] S41. Determine the position of the starting point of the L1 joint according to the characteristics of the L1 joint, and measure the width of the L1 joint zone; specifically: The roadway L intersects the fault F obliquely at point O, the fault throw at point O is H1, the width of the L1 joint zone measured along the roadway direction is OA, draw a perpendicular line AA' from point A to the fault plane to obtain the width of the L1 joint zone in the direction perpendicular to the fault plane.

[0044] S42. Measure the azimuth, dip angle, fault throw of the fault plane, and the azimuth and gradient of the roadway.

[0045] S43. Convert the measured distance of the roadway into the distance in the direction perpendicular to the fault plane. The specific expression is as follows:

[0046] Section B = Section B'·sinωsinβcosα (1)

[0047] In the formula, Section B is the width of the L1 joint zone in the direction perpendicular to the fault plane; Section B' is the width of the L1 joint zone measured in the roadway; ω is the angle between the roadway azimuth and the strike of the fault plane; β is the dip angle of the fault plane; α is the roadway gradient;

[0048] S44. Substitute the width of the L1 joint zone in the direction perpendicular to the fault plane, Section B, into formula (1) to obtain the fault throw. The fault throws at points O and A' in its strike direction are H1 and H2 respectively. Based on the fault throws at these two points and the distance d between them, obtain the attenuation coefficient of the fault and calculate the extension range of the fault. The specific expressions are as follows:

[0049]

[0050] Specifically for the collapse column, determine the position of the collapse column according to the dip and dip angle of the rock fracture surface, rock properties, and groundwater conditions on the observation surface. Determine the size and range of the collapse column according to the lengths of the major axis and minor axis of the exposed collapse column and the size of the column wall angle. Directly predict and draw the map for the collapse column with a small range. Connect the collapse columns with the same or similar characteristics on the same observation surface or different observation surfaces, and draw a connection map to indicate that these collapse columns have a larger range and may span different observation surfaces.

[0051] S5. Select an appropriate scale to draw the geological section. The selection of the scale depends on the spacing of the key points of the coal seam in the structural zone; the smaller the scale, the more detailed the geological mapping and the more intuitively the distribution and structural characteristics of the geological bodies are shown. Among them, according to the spacing of the key points of the coal seam in the structural zone, the selection of the scale includes the following three situations:

[0052] Situation 1: When the spacing of the key points of the coal seam in the structural zone is no more than 10 m, select a scale of 1:1000;

[0053] Situation 2: When the spacing of the key points of the coal seam in the structural zone is between 10 m and 20 m, select a scale of 1:2000;

[0054] Situation 3: When the spacing of the key points of the coal seam in the structural zone is no less than 20 m, select a scale of 1:5000.

[0055] S6. After completing the structural connection, conduct a systematic analysis of the geological characteristics within and between all observation surfaces, comprehensively consider the relationships between various structural characteristics, generate a geological model, analyze and verify the geological model, and predict the spatial distribution of folds, faults, and collapse columns in the coal seam structural zone. Through the accurate prediction of the structural zone, it has important theoretical significance for clarifying the influence mechanism of strong structural zones on gas occurrence and gas outburst. At the same time, it provides technical support for guiding the identification and prediction of structural coal seams in the future main mining panel of the mine and timely eliminating potential gas outburst hazards.

[0056] Embodiment

[0057] S1: As Figure 2 , taking the coal mining face, roadway and longitudinal direction of coal seam in the north first panel of Yangmei Shijiazhuang Coal Mine in Shanxi as the X, Y, and Z axes respectively to represent the three-dimensional spatial position of geological mapping. The observation surface distances in the X and Y directions are 300m and 10m respectively, and continuous observation is carried out in the Z direction. An observation surface is set every 10m in the Y direction, and the coal seam in the structural belt is observed and recorded along the X direction;

[0058] S2: Search for the structural coal seam along the working face and roadway directions respectively, and observe and record the structural type, occurrence, coal body structure, coal seam structure, fracture system, macroscopic coal rock type, parting and geological characteristics of roof and floor;

[0059] S3: On this basis, through the observation of key points of the coal seam in the structural belt in the X, Y, and Z directions and marking them on the geographical coordinate map, finally form a three-dimensional distribution geological map of the coal seam in the structural belt. During the mapping process, control weak and strong structural points respectively. Among them, more than 100 control points are set for weak structures, and more than 50 control points are set for strong structures, as shown in Table 1

[0060] Table 1 Mapping Points

[0061]

[0062] Furthermore, obtain the geological survey data of each of the said geological survey points. In the embodiment of the present application, the geological survey data includes all data obtained at the geological survey points, including survey point number, survey point coordinates, lithology, contact relationship, fault number, fault strike, fault dip, fault trend and fault property, the lengths of the long and short axes of the collapse column, the strike of the fold axis, smooth surface, etc.

[0063] S4: Apply the theories of structural geology and coal geology to analyze the development law of structures, conduct connection and mapping, and connect the geological bodies with the same structural characteristics with lines. On this basis, observe the structural characteristics appearing on each observation surface, such as fault dip and throw, strike of the fold axis, etc., and associate the structural phenomena with the same or similar characteristics to effectively predict the geological structure of the entire coal seam and structural coal seam.

[0064] S5: Select an appropriate scale to draw a geological cross-section. The selection of the scale depends on the spacing of the key points of the coal seam in the structural belt.

[0065] S6: After completing the structural connection, conduct a systematic and comprehensive analysis of the geological characteristics within all observation surfaces and between each observation surface. Taking the observation surface of the first panel in the north of Shijiazhuang as an example, the following conclusions are found:

[0066] In the observation plane Y1, there is a collapse column with an approximate radius of 5 m and a depth of 2 m. This collapse column shows typical collapse characteristics, and significant vertical displacement and fracture of the rock strata occur here. A normal fault runs through the observation plane along the Y-axis direction, with a fault plane dip angle of 73° and a vertical displacement (throw) of the fault of 0.8 m. The rock strata near this normal fault are folded and uplifted, forming an anticline structure that runs through the entire observation plane. The strike of the anticline axis is NW-SE, showing the deformation characteristics of the rock strata after being subjected to compressive stress.

[0067] In the observation plane Y2, the geological structure is also complex. There is a collapse column with a radius of 3 m and a depth of 2.3 m. This collapse column is similar to the one in the observation plane Y1 but slightly smaller in scale. A normal fault with a dip angle of 80° and a throw of 0.7 m develops on the right side of the collapse column. This fault plane shows a large dip angle, indicating significant sliding and dislocation of the rock strata here. At the same time, a normal fault with a dip angle of 63° and a throw of 0.5 m develops in the upper right corner of the observation plane. There is an anticline structure with the same characteristics as that in the observation plane Y1 between these two faults. The strike of the anticline axis is NW-SE, indicating that this anticline extends from the observation plane Y1 to the observation plane Y2, reflecting a consistent tectonic stress field in the area.

[0068] In the observation plane Yn, the strike of the fold axis mostly shows a downward depression, forming an anticline structure that runs through the entire observation plane. The strike of the anticline axis is NE-SW. The formation of this anticline structure indicates that the rock strata in this area have been subjected to compressive stress in the vertical direction. In addition, there is a small normal fault with a length of 5.3 m along the Y-axis direction. The dip angle of the fault plane is 63°, and the throw of the fault gradually decreases from 1.2 m along the Y-axis direction to 0. By comparing the geological structures of adjacent observation planes, if no structures with the same characteristics are found in adjacent observation planes, it can be inferred that this fault is a local structure in the observation plane Y3 and does not extend to other observation planes. This normal fault shows the characteristics of gradually weakening fault activity, indicating the stress release process of the rock strata here.

[0069] Finally, combining historical data and current observation data, the geological model is corrected and optimized to ensure the accuracy and reliability of the model. By understanding and accurately predicting the tectonic belt in detail, the influence mechanism of the strong tectonic belt on gas occurrence and gas outburst is clarified. At the same time, it provides technical support for guiding the identification and prediction of tectonic coal seams in the future main mining panel of the mine and timely eliminating potential gas outburst hazards.

[0070] Therefore, the present invention adopts the above-mentioned underground geological mapping method for predicting coal seam structural zones. By using existing conditions in the mining area such as coal mining faces, roadways, and the longitudinal direction of coal seams, an observation surface is established. The key points of the coal seam in the structural zone are observed and marked on the geographical coordinate map. Finally, a three-dimensional distribution geological map of the coal seam in the structural zone is formed to achieve the prediction of the coal seam in the structural zone. After using this method, the results are more intuitive and accurate, and the economic cost is lower.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the present invention or make equivalent replacements, and these modifications or equivalent replacements do not enable the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for underground geological mapping of a mine for predicting coal seam structural zones, characterized in that: The following steps are involved: S1. Arrange the coal mining face, tunnel and coal seam longitudinal directions as X, Y and Z axes respectively; S2. Several observation surfaces are set along the Y-axis direction of the tunnel, and the observation surfaces are spaced apart along the X-axis direction; S3. Search for coal seams in the structural belt along the X-axis of the working face and the Y-axis of the roadway, record the structural type, occurrence, coal body structure, coal seam structure, fracture system, macro coal rock type, interlayer and roof and floor geological characteristics of the coal seams in the structural belt, observe the key points of the coal seams in the X-axis, Y-axis and Z-axis directions, and mark them on the geographic coordinate map; S4, connect the geological bodies with the same structural features with lines, where the structural features include folds, faults and collapse columns; S5. Select an appropriate scale to draw the geological cross section. The scale depends on the spacing of key points of the coal seams in the structural belt. S6. Systematically analyze the geological features within and between all observation surfaces, generate geological models, analyze and verify the geological models, and predict the spatial distribution of folds, faults and collapse columns in coal seam structural belts; The key points of the coal seams in the structural belt are recorded by using the method of mine geological mapping, including the fault dip, fault drop, the length of the major and minor axes of the collapse column, the axis direction of the fold, and the dip and range of the smooth surface; The folds in S4 specifically refer to the fold axis direction, inclination, fold type and morphology in the coal mining working face and roadway direction on the observation surface; in specific operations, folds showing the same or similar characteristics are connected; The faults in S4 are specifically the fault strike, fault dip, fault inclination, and the filling and coal rock occurrence in the coal mining working face and roadway direction on the observation surface; in specific operations, the same or similar faults on the same observation surface or between different observation surfaces are connected, and for the fault structure exposed only on one side of the observation surface, the existing geological data and regional geological laws are used to determine the location and extension range of the structure, as follows: S41. According to the characteristics of the L1 joint, the position of the L1 joint starting point is determined, and the width of the L1 joint zone is measured; specifically, the roadway L and the fault F are obliquely intersected at point O, the fault distance at point O is H1, the width of the L1 joint zone measured along the roadway direction is OA, and a perpendicular line AA′ is drawn from point A to the fault plane to obtain the width of the L1 joint zone perpendicular to the fault plane; S42, measuring the azimuth, inclination, fault distance of the fault plane and the azimuth and slope of the roadway. The measured fault distance is H1, that is, the measured fault distance at point O is H1; S43. Convert the measured distance of the tunnel into the distance in the direction perpendicular to the fault plane. The specific expression is as follows: （1） Wherein, Section B is the width of Section L1 in the direction perpendicular to the fault plane; is the width of L1 joint measured in the tunnel; It is the angle between the tunnel orientation and the fault plane direction; is the fault plane dip; is the roadway slope; S44, will Substituting into formula (1), we can obtain the fault throw. The fault throws of points O and A′ on the strike are H1 and H2 respectively. Based on the fault throws of these two points and the distance d between them, we can obtain the attenuation coefficient of the fault and calculate the extension range of the fault. The specific expression is as follows: （2） （3）； The collapse column in S4 is specifically to determine the position of the collapse column according to the inclination and dip of the rock fracture surface on the observation surface, the rock layer properties, and the groundwater conditions. The size and range of the collapse column are determined according to the length of the major and minor axes of the exposed collapse column and the size of the column wall angle. The collapse columns with a small range are directly predicted and mapped. The collapse columns with the same or similar characteristics on the same observation surface or different observation surfaces are linked and connected to draw lines. In S5, according to the spacing of key points of coal seams in the structural belt, the selection of scale includes the following three cases: Case 1: When the spacing between key points of the coal seam in the structural zone is no more than 10 m, a scale of 1:1000 is selected; Case 1: When the spacing between key points of coal seams in the structural zone is between 10m and 20m, a scale of 1:2000 is selected; Case 1: When the spacing between key points of coal seams in the structural belt is not less than 20m, select a scale of 1:5000.

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