A method for determining the boundary of a top blast in an underground stope

Abstract

The present application belongs to the field of underground mining blasting, and relates to a method for determining the top boundary of underground stope blasting, and the specific steps include: determining a preliminary scheme through theoretical analysis and field comparison, three-dimensional detection of the empty area, establishment of the empty area model, top section of the empty area, determination and drawing of the top boundary of the stope blasting. The technical scheme of the present application has an important role in the stability of the empty area roof after blasting.

Description

Technical Field

[0001] This invention belongs to the field of underground mining blasting and relates to a method for determining the blasting boundary at the top of an underground mine, which plays an important role in the stability of the roof of the void after blasting. Background Technology

[0002] After underground mining is carried out by medium-deep hole blasting, goaf areas will be formed. The stability of the goaf areas is very important, especially during the ore extraction process. The shock waves and splashed rocks caused by the collapse of the goaf areas may damage equipment and, in severe cases, injure personnel.

[0003] The collapse of a goaf mainly consists of two parts: the collapse of the side walls and the collapse of the roof. Therefore, studying the stability of the roof is crucial for the stability of the goaf. The stability of the roof is related to the span of the goaf, the rock conditions, and the morphology of the roof.

[0004] Under normal circumstances, the shape of the roof of the goaf is generally consistent with the shape of the ore body. Sometimes the ore body is more horizontal, and the top of the stope will be similar to a flat roof. From a safety point of view, these arrangements are not conducive to the stability of the goaf.

[0005] During the mining process, a large amount of waste rock is generated. Currently, waste rock can also be utilized, and its price is not low. Some mines may even have their own waste rock processing plants. In this case, it is advisable to do a good job in the early stage, starting with deep hole blasting in the mining area, and to make reasonable arrangements for the deep hole blasting boundaries in the mining area roof. Once the mining is completed, the waste rock will be utilized on the one hand, and the stability of the roof of the goaf will be increased on the other hand, making the goaf safer. Summary of the Invention

[0006] In order to increase the stability of the roof of the void, this invention proposes a method for determining the blasting boundary at the top of the underground mining area.

[0007] To achieve the above technical objectives, the technical solution adopted in this application is: a method for determining the blasting boundary at the top of an underground mining area, comprising:

[0008] Preliminary plan determined: Theoretical analysis shows that the roof boundary of the deep-hole blasting design in the mining area needs to be arranged in an arch shape. The arch shape of the deep-hole blasting boundary should be consistent with the shape of the collapsed goaf in the mining area. The arch height and span of the mining area are calculated based on the pressure arch theory. Field measurements were conducted on a gentle goaf area for scanning and modeling, and the results were compared with the theoretical analysis results: The theoretically calculated arch height and the measured arch height range were compared. If the theoretical value is greater than the measured value range, the arch height is selected from the theoretical value range for subsequent analysis; if the theoretical value is less than the measured value range, the arch height is selected from the measured value range for subsequent analysis. Based on field observations and measurements, the actual collapsed arch shape is larger than expected. Based on theoretical calculations, the arch height is selected from the range of measured values ​​for subsequent analysis, taking into account the over-excavation factor of blasting, and subtracting the over-excavation value of 0.5m; and the value is determined according to the actual lithological characteristics of the stope: the specific method is that when the rock is stable and bedding, joints, fissures, and cavities are not well developed, the arch height of the blasting boundary at the top of the stope is the smaller value after subtracting 0.5m from the measured value range; if the rock is loose and bedding, joints, fissures, and cavities are relatively well developed, the arch height of the blasting boundary at the top of the stope is the larger value after subtracting 0.5m from the measured value range. In actual application, adjustments can be made according to the actual effect. The deep hole blasting boundary in the stope is arranged as a circular arch, and finally the blasting boundary of the stope roof is drawn;

[0009] Three-dimensional detection of the empty area uses a three-dimensional laser detection system to scan the empty area of ​​the mining area and obtain a detection point file, which includes the spatial coordinates of all detection points.

[0010] Empty area model establishment: Based on the detection point file, i.e. the scanned spatial points, a measured model of the empty area in the mining area is established;

[0011] Top section of the void: Based on the measured model of the void in the stope, the void at the top of the ore body with a relatively gentle ore boundary is selected as the sectioning object.

[0012] Determination and drawing of the blasting boundary at the top of the mining area: Observe the cut section and compare it with the design of the central hole blasting in order to determine the position of the arch and measure its height.

[0013] As an improved technical solution of this application, when using the three-dimensional laser detection system technology, the probe is extended into the empty area to scan using an extension rod.

[0014] As an improved technical solution in this application, when using the three-dimensional laser detection system technology, it is necessary to use a total station to measure the coordinates of the probe's points and the coordinates of a point on the probe rod, and to calculate the azimuth angle.

[0015] As an improved technical solution in this application, the empty area model is established as follows: after the mining area is detected, a point file is formed, which is the scanned spatial points. The detection point file is converted by the software that comes with the detection system to generate a .str file. Then, the .str file is processed by the modeling software to establish a measured model of the mining area empty area.

[0016] As an improved technical solution in this application, the top section of the empty area is cut: Open the selected empty area model with 3D software, select to create a block, select to cut the section in a direction perpendicular to the direction of the empty area, select manual cutting section, set the front face and back face to 0.01, cut directly, then close the solid and export the section.

[0017] As an improved technical solution in this application, the determination and drawing of the blasting boundary at the top of the stope are as follows: the over-excavation value is generally taken as 0.5m, so the arch height ranges from 2.5 to 3.5m. Therefore, the blasting boundary of the medium-deep hole at the top of the stope is a circular arch with a width of 15m and an arch height of 2.5-3.5m. When the rock is stable and bedding, joints, fissures, and cavities are not well developed, the arch height of the blasting boundary at the top of the stope is taken as a small value, between 2.5 and 3m. If the rock is loose and bedding, joints, fissures, and cavities are well developed, the arch height of the blasting boundary at the top of the stope is taken as a large value, between 3 and 3.5m. In actual application, it can be adjusted according to the actual effect.

[0018] Beneficial effects:

[0019] 1. This invention is based on the results obtained from theoretical calculations and comparative analysis of actual measurements of empty areas, and can directly guide the design of medium-hole blasting.

[0020] 2. Enhanced stability of the airspace roof, making the airspace safer;

[0021] 3. In existing technology, the boundary of deep holes in the top of the stope is consistent with the ore body boundary of the stope. This leads to poor stability of the roof of the empty area formed after mining. In contrast, the present invention sets the blasting boundary of the stope roof to be arched and inconsistent with the ore body boundary. The advantage of this is that the roof of the empty area formed after blasting will be more stable.

[0022] 4. Conventional mining techniques do not allow for the determination of the arch height by blasting the roof boundary. The method used in this invention to determine the arch height is not through theoretical calculation, but by selecting a suitable mining area—specifically, one with a gently sloping roof—and obtaining the range of the arch height through actual measurements, then subtracting the empirical blasting value of 0.5m.

[0023] 5. The present invention provides specific selection methods in practical applications. Attached Figure Description

[0024] Figure 1 A schematic diagram showing the boundary of a medium-deep hole blasting operation at the top of a mining area;

[0025] In the diagram, 1: top blasting boundary, 2: mine boundary, 3: hole bottom distance, 4: blasting boundary on both sides, 5: core, 6: drilling tunnel, 7: medium-deep hole. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art to which this invention pertains.

[0027] Definition: "Development" is a term in engineering geology, referring to the intensity and degree of harm to engineering projects. Generally speaking, it refers to the development of adverse geological phenomena, such as joints and fissures. Taking joint development as an example: Immature joints: 1-2 groups of joints, regular, structural type, spacing greater than 1m, mostly closed joints, the rock mass is cut into large blocks. Moderately developed joints: 2-3 groups of joints, X-shaped, relatively regular, mainly structural type, most spacing greater than 0.4m, mostly closed joints with some slightly open joints, little filling material, the rock mass is cut into large blocks. Well-developed joints: 3 or more groups of joints, irregular, X-shaped or star-shaped, mainly structural and weathering type, most spacing less than 0.4m, mostly open joints, some with filling material, the rock mass is cut into blocks. Joints are well-developed: there are more than 3 groups of joints, which are disordered and mainly weathered and structural. Most of them are less than 0.2m apart, mainly open joints, with a few wide open joints. They are generally filled with material, and the rock mass is cut into fragments.

[0028] A method for determining the blasting boundary at the top of an underground mining area includes the following steps: determining a preliminary scheme through theoretical analysis and on-site comparison; three-dimensional detection of the void area; establishment of a void area model; cross-section of the top of the void area; and determination and drawing of the blasting boundary at the top of the mining area.

[0029] The specific steps are as follows:

[0030] 1. A preliminary plan was determined through theoretical analysis and comparison with actual on-site conditions.

[0031] According to the pressure arch theory, after mining through medium-deep hole blasting, a goaf will be formed. The roof of the goaf will deform, and the deformation will increase over time. When the deformation exceeds the rock's bearing capacity, a collapse will occur, eventually forming a relatively stable arch shape. Therefore, the roof boundary of the medium-deep hole blasting design needs to be arranged in an arch shape to ensure greater stability of the goaf roof after subsequent mining. The arch shape of the medium-deep hole blasting boundary should be consistent with the shape of the collapsed goaf to ensure greater stability of the goaf roof after blasting.

[0032] In underground mining, it is difficult to encounter rock masses with good integrity throughout the mining area. According to Protodyakonov's theory, rock masses with poor integrity can be regarded as loose bodies with certain cohesion. When mining is carried out, the roof will collapse. This collapse is limited and will form a balanced arch, called a pressure arch.

[0033] The formula for calculating the pressure arch height is h = a1 / f

[0034] Where h is the arch height, a1 is half the span of the mining area, and f is the Protodyakonov coefficient.

[0035] If the width (span) of a certain mine is 15m, then a1 is 7.5m. If the Protodyakonov coefficient f is greater than 8, then the pressure arch height is less than 0.94m.

[0036] However, on-site observations revealed that the height of the roof arch in the empty area often exceeded 0.94m, which is greater than the theoretical calculation value. This is because the theoretical calculation assumes an ideal homogeneous state, while the underground rock mass is heterogeneous and is affected by forces in other directions besides gravity.

[0037] Therefore, theoretical calculations can serve as a verification and supplement to the actual on-site conditions. Specifically, the theoretically calculated arch height is compared with the measured arch height range. If the theoretical value is greater than the measured value range, the theoretical value is selected for subsequent analysis; if the theoretical value is less than the measured value range, the measured value range is selected for subsequent analysis. Based on on-site observation and measurement, the actual collapsed arch was larger than the theoretically calculated value, so the measured value range was selected for subsequent analysis of the arch height.

[0038] Taking into account the over-excavation factor of blasting, the over-excavation value of blasting is reduced by 0.5m, and the value is determined according to the actual lithological characteristics of the stope: Specifically, when the rock is stable and bedding, joints, fissures, and cavities are not well developed, the arch height of the blasting boundary at the top of the stope is taken as the smaller value after subtracting 0.5m from the measured value range. If the rock is loose and bedding, joints, fissures, and cavities are relatively well developed, the arch height of the blasting boundary at the top of the stope is taken as the larger value after subtracting 0.5m from the measured value range. In actual application, it can be adjusted according to the actual effect. The deep hole blasting boundary in the stope is arranged as a circular arch, and finally the blasting boundary of the stope roof is drawn.

[0039] Three-dimensional detection of the empty area uses a three-dimensional laser detection system to scan the empty area of ​​the mining area and obtain a detection point file, which includes the spatial coordinates of all detection points.

[0040] Empty area model establishment: Based on the detection point file, i.e. the scanned spatial points, a measured model of the empty area in the mining area is established;

[0041] Based on theory and actual field conditions, it is necessary to select relatively gentle stope areas for scanning modeling and cross-sectioning (stopes with relatively flat roof boundaries, because after blasting, the roof will experience under-excavation, over-excavation in some areas, and collapse in others due to the clamping effect, resulting in a near-arched roof that closely resembles the actual state after a long period of roof collapse). Comparative analysis will then be conducted: the arch height will be measured, and the arch height values ​​for each stope will be statistically analyzed to obtain the arch height range. Stopes with excessively high arch heights can be excluded; for example, while most stopes have arch heights between 3-4 meters, some may reach over 5 meters. Such data is not representative and needs to be discarded. The range of measured arch heights will be determined. Considering the over-excavation factor, the over-excavation value is reduced by 0.5m (empirical value), and the value is determined according to the actual lithological characteristics of the stope: Specifically, when the rock is stable and bedding, joints, fissures, and cavities are not well developed (geological terminology, determined by geological professionals), the arch height of the blasting boundary at the top of the stope is the smaller value after subtracting 0.5m from the measured value range. If the rock is loose and bedding, joints, fissures, and cavities are relatively developed, the arch height of the blasting boundary at the top of the stope is the larger value after subtracting 0.5m from the measured value range. In actual application, adjustments can be made according to the actual effect. The deep hole blasting boundary in the stope is arranged as a circular arch, and finally the blasting boundary of the stope roof is drawn.

[0042] The technical purpose of this step is to conduct a preliminary analysis to determine the blasting boundary at the top of the mining area, in order to further determine the blasting boundary.

[0043] The innovation of this step is:

[0044] (1) Through theoretical analysis, it was determined that the deep hole blasting boundary of the top plate of the empty area is arranged in an arch shape;

[0045] (2) The method for determining the arch height was determined by selecting a suitable stope (a stope with a relatively flat roof boundary, because after such blasting, the roof will be under-excavated on both sides due to the clamping effect, with some areas being over-excavated and some areas collapsing, and the roof will be close to an arch shape, close to the actual state after the roof collapses and is left for a long time). The range of the measured arch height of the roof was then subtracted from the blasting over-excavation value, and the value was determined according to the actual lithological characteristics of the stope. The blasting over-excavation value was 0.5m, which was an empirical value.

[0046] 2. Three-dimensional airspace detection

[0047] A three-dimensional laser detection system is used to scan the stope area, obtaining a point file containing the spatial coordinates of all detection points. Specifically, a three-dimensional laser detection system (VS150, C-ALS, CMS, etc.) is employed to scan the stope area. Personnel do not need to approach the stope; the probe is inserted into the stope using an extension rod for scanning. The detection data is automatically transferred to a computer, generating the point file.

[0048] To locate the goaf in the mining area, surveying technicians need to use a total station (a specialized surveying tool) to measure the coordinates of points on the probe and the coordinates of points on the probe rod, and calculate the azimuth. The purpose is to create a point file by probing the goaf, which will then be used to build a goaf model.

[0049] The azimuth of the empty area is part of the empty area detection. The purpose is to introduce the model after the empty area detection into the actual coordinate system. The specific operation method is to use a total station (a professional surveying equipment) in conjunction with existing coordinate points to measure a coordinate point on the probe and a coordinate point on the probe rod. Draw the two points on CAD and connect them to make a north-facing auxiliary line. This will allow you to measure the azimuth of the empty area. Then, by measuring the probe coordinates and the azimuth of the empty area, the model is adjusted to the actual spatial location of the mine site using 3D software.

[0050] 3. Establish an empty area model

[0051] Based on the probe point file, i.e., the scanned spatial points, a measured model of the stope void is established. Specifically: after stope exploration, point files are generated, i.e., the scanned spatial points. The software included with the exploration system (3D laser exploration systems such as VS150, C-ALS, etc.) converts the probe point file into a .str file. Then, modeling software (commonly 3DMine, Surpac, Datemine, etc.) processes the .str file to establish the measured model of the stope void. Taking Surpac as an example, the .str file is opened with Surpac, the solid module is located, and a triangulation network is created to construct the measured model of the stope void. The model is then adjusted to the actual spatial location of the mine stope by measuring the probe coordinates and the void azimuth (connecting the solids with lines, a function of 3D software). The technical objective is to build a 3D model to serve as a basis for subsequent roof section cutting.

[0052] 4. Sectioning of the roof of the vacant area

[0053] Based on the measured model of the stope void, a stope void with a relatively gentle top boundary of the ore body is selected as the cross-section object. Specifically, a stope void with a relatively gentle top boundary of the ore body is generally chosen as the cross-section object. According to field experience, after blasting in this type of stope, under-excavation, over-excavation in some areas, and collapse in some areas will occur on both sides of the roof due to the clamping effect, and the roof will be close to an arch shape, similar to the actual state of the roof after long-term placement following collapse. The specific cross-section steps are as follows: Open the selected void model in 3D software, select "Create Block," select "Section and Cutting Section": select the direction perpendicular to the void strike to cut the section (the obtained section takes the top area (one layer height) as the research object), select "Manual Cutting Section," set the front face back to 0.01, cut directly, then close the solid, and export the section. The technical purpose is to use the cross-section to serve the subsequent analysis and determination of the roof boundary.

[0054] Compared to existing technologies, the research location after sectioning in this application is different. The research location after sectioning in this paper is the top plate of the empty area, with the top region (one layer height) as the research object. The purpose is to facilitate the observation of the top plate of the empty area and the measurement of the arch height.

[0055] 5. Determination of the blasting boundary at the top of the mining area

[0056] The cross-section after cutting is observed and compared with the design of the central hole blasting. The purpose is to determine the position of the arch and measure its height. Taking a certain mine as an example, a stope with a relatively flat roof is selected. Because the ore body is relatively flat, the blasting design boundary is close to the flat roof. According to field experience, after blasting in this type of stope, the roof will be under-excavated on both sides due to the clamping effect, some areas will be over-excavated, and some areas will collapse. The roof will be close to the arch shape, which is close to the actual state after the roof collapses and is left for a long time.

[0057] Example: The width of the stope is 15m. According to the measured model profile, the arch height is generally around 3-4m, which is greater than the theoretical value of 0.91m. Considering the impact of blasting over-excavation, based on experience, the blasting over-excavation value is generally taken as 0.5m. Therefore, the range of the arch height is 2.5-3.5m. Thus, the boundary of the deep-hole blasting at the top of the stope is a circular arch with a width of 15m and an arch height of 2.5-3.5m.

[0058] In practical applications, when the rock is stable and bedding, joints, fissures, and cavities are not well developed, the arch height of the blasting boundary at the top of the stope should be a small value, between 2.5 and 3 meters. If the rock is loose and bedding, joints, fissures, and cavities are relatively well developed, the arch height of the blasting boundary at the top of the stope should be a large value, between 3 and 3.5 meters. In actual application, adjustments can be made according to the actual effect.

[0059] The circular arch is drawn using 2D drawing software (usually CAD) to serve as the blasting boundary of the mining area roof.

[0060] Specific applications:

[0061] like Figure 1 As shown, a mine in Anhui province has a stope width of 15m and a length of 85m. Each stope is divided into multiple sections, each section being 12.5m high. Generally, a stope consists of 3-4 sections. In the diagram: 1. Top blasting boundary; 2. Mine boundary; 3. Bottom hole distance; 4. Side blasting boundaries; 5. Drilling core; 6. Rock drilling tunnel; 7. Medium-deep hole.

[0062] After the mining operation is completed, a 3D laser probing system (VS150 laser detector, C-ALS laser detector, CMS laser detector, etc.) is generally used to scan the stope area. The resulting point file (scanned spatial points) is generated by the probing system's built-in software (such as VS150 or C-ALS) and converted into a .str file. This .str file is then processed by modeling software (commonly 3dmine, Surpac, Datemine, etc.) to create a measured model of the stope area. Taking Surpac as an example, the .str file is opened with Surpac, the solid module is located, a triangulation network is created, and a measured model of the stope area is constructed. The model is then adjusted to the actual spatial location of the mining area by measuring the probe coordinates and the azimuth angle of the stope.

[0063] Select a relatively flat stope area at the top of the ore body as the cutting target. Open the selected stope model in 3D software, select "Create Block," then select "Section and Cutting Section," and choose "Manual Cutting Section." Set the front and back faces to 0.01, and cut directly. Observe the roof after cutting multiple stopes and measure the arch height. The arch height is generally around 3-4m. Considering the impact of blasting over-excavation, the blasting over-excavation value is selected as 0.5m based on experience. Therefore, the arch height is taken as 2.5-3.5m. Thus, the blasting boundary of the stope roof is a circular arch with a width of 15m and an arch height of 2.5-3.5m. Based on the lithological characteristics of a mine in Anhui Province, the eastern part of the mine generally has relatively stable rock with underdeveloped bedding, joints, fissures, and cavities, while the western part has relatively loose rock with well-developed bedding, joints, fissures, and cavities. Therefore, the arch height in the eastern part generally tends to be smaller, such as between 2.5 and 3 meters, while the arch height in the western part generally tends to be larger, such as between 3 and 3.5 meters. Although the overall lithology in the eastern part is better, there may be localized areas that are more fractured with well-developed bedding, joints, fissures, and cavities. In such cases, the arch height will also be larger.

[0064] Use CAD software to draw the blasting boundary of the mining area roof.

[0065] By applying this method, the roof of the empty area is arched, which significantly enhances the stability of the roof and makes the empty area safer. In addition, the arrangement of the arch will lead to moderate dilution of the top of the mine, and the waste rock produced can be used for stone processing, increasing efficiency.

[0066] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A method for determining the blasting boundary at the top of an underground mining area, characterized in that, include: Preliminary plan determined: Theoretical analysis shows that the roof boundary of the deep-hole blasting design in the mining area needs to be arranged in an arch shape. The arch shape of the deep-hole blasting boundary should be consistent with the shape of the collapsed goaf in the mining area. The arch height and span of the mining area are calculated based on the pressure arch theory. Field measurements are conducted on a gentle goaf area for scanning and modeling, and the arch height results are compared with those from the theoretical analysis. If the theoretical value is greater than the measured value, the arch height is selected from the theoretical value for subsequent analysis; if the theoretical value is less than the measured value, the arch height is selected from the measured value for subsequent analysis. Considering the over-excavation factor, a 0.5m over-excavation value is subtracted, and the value is determined based on the actual lithological characteristics of the stope. The value determined based on the actual lithological characteristics of the stope includes: if the rock is stable and bedding, joints, fissures, and cavities are not well-developed, the lower value of the measured range of the blasting boundary arch height at the top of the stope is taken; if the rock is loose and bedding, joints, fissures, and cavities are well-developed, the higher value of the measured range of the blasting boundary arch height at the top of the stope is taken. The deep-hole blasting boundary in the stope is arranged as a circular arch, and the final blasting boundary of the stope roof is drawn. Three-dimensional detection of empty areas uses a three-dimensional laser detection system to scan the empty areas of the mining area and obtain detection point files, i.e., the scanned spatial points; Empty area model establishment: Based on the detection point file, a measured model of the empty area in the mining area is established; Top section of the void: Based on the measured model of the void in the stope, the void at the top of the ore body with a relatively gentle ore boundary is selected as the sectioning object. Determination and drawing of the blasting boundary at the top of the mining area: Observe the cut section and compare it with the design of the central hole blasting in order to determine the position of the arch and measure its height.

2. The method for determining the blasting boundary at the top of an underground mining area according to claim 1, characterized in that, When using a three-dimensional laser detection system, the probe is extended into the empty area to scan using an extension rod.

3. The method for determining the blasting boundary at the top of an underground mining area according to claim 2, characterized in that, When using a three-dimensional laser detection system, a total station is required to measure the coordinates of the probe's points and the coordinates of a point on the probe rod, and to calculate the azimuth angle.

4. The method for determining the blasting boundary at the top of an underground mining area according to claim 1, characterized in that, Empty area model establishment: After the mining area is explored, point files are generated, which are the scanned spatial points. The software that comes with the exploration system converts the exploration point files to generate .str files. Then, the modeling software processes the .str files to establish a measured model of the mining area empty area.

5. The method for determining the blasting boundary at the top of an underground mining area according to claim 1, characterized in that, Sectioning the top of the empty area: Open the selected empty area model in 3D software, select Create Block, select the direction perpendicular to the direction of the empty area to cut the section, select Manual Cutting Section, set the front and back faces to 0.01, cut directly, then close the solid and export the section.

6. The method for determining the blasting boundary at the top of an underground mining area according to claim 1, characterized in that, Determination and drawing of the blasting boundary at the top of the stope: If the over-excavation value is taken as 0.5m, the arch height range is 2.5-3.5m. Therefore, the blasting boundary of the medium-deep hole at the top of the stope is a circular arch with a width of 15m and an arch height of 2.5-3.5m. When the rock is stable and bedding, joints, fissures, and cavities are not well developed, the arch height of the blasting boundary at the top of the stope is taken as a small value, between 2.5-3m. If the rock is loose and bedding, joints, fissures, and cavities are well developed, the arch height of the blasting boundary at the top of the stope is taken as a large value, between 3-3.5m. In actual application, it can be adjusted according to the actual effect.

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