Thick and hard roof impact disaster control method based on blasting technology

Abstract

The invention discloses a thick and hard roof impact disaster control method based on the blasting technology, and relates to the technical field of blasting pressure relief. If the bottom face of the key layer is within the range of 20 m above the coal seam, blast holes are constructed from the low-position roadway to the key layer; if the working face span is gt; if the height is 150 m and the bottom surface of the key layer is within the range of 20-40 m above the coal seam, blast holes are constructed from the extraction roadway to the key layer; if the working face span is gt; if the bottom surface of the key layer is within the range of 40-100 m above the coal seam, a high-position roadway is constructed in the key layer along the trend of the working face, and then the blast hole is constructed from the high-position roadway to the key layer; if the working face span is gt; if the position of the bottom face of the key layer is 100 m above the coal seam, the blast hole is drilled from the ground to the key layer for construction. According to the method, the working face span and the occurrence position of the thick and hard roof are taken as starting points, different conditions of covering the working face with the thick and hard roof are divided, and a corresponding blasting pressure relief technology is given, so that the blasting pressure relief effect is improved.

Description

Technical Field

[0001] This invention relates to the field of blasting and pressure relief technology, and in particular to a method for mitigating impact disasters on thick, hard roofs based on blasting technology. Background Technology

[0002] Rockburst disasters refer to the sudden and violent destruction of rock masses surrounding mine tunnels or working faces due to the instantaneous release of elastic deformation energy. They are often accompanied by coal and rock ejection, loud noises, and blast waves. Characterized by their suddenness, instantaneousness, and immense destructive power, rockbursts pose a serious threat to the safe production of underground engineering projects such as coal mines, potentially leading to casualties, equipment damage, and tunnel collapses. The control of rockburst disasters is urgently needed. Based on the need for safe and efficient mining in underground coal mines, blasting methods have shown significant advantages in roof rockburst disaster control in anti-rockburst and pressure relief engineering. Blasting technology is the primary method for roof pressure relief in coal mines. Its principle is mainly to use the shock wave generated by the explosion of explosives to break up the rock and create fissures, ultimately forming a loosened zone around the blast hole. The connection of these loosened zones from each blast hole constitutes a weak zone (pressure relief zone), providing space for the release and compensation of high ground stress. Furthermore, pressure relief technologies such as strike-and-dip deep-hole blasting, slotted charge shaped charge blasting, and combined deep and shallow-hole blasting have been developed around blasting pressure relief. These technologies can effectively solve the deformation problem of roadways left along the goaf, but they can only address small-scale rockburst problems caused by the immediate or main roof and cannot cover the entire working face, resulting in less than ideal pressure relief effects. At the same time, the randomness of the location of the thick, hard roof above the working face greatly increases the difficulty of managing rockburst disasters. Summary of the Invention

[0003] The purpose of this invention is to provide a method for mitigating impact disasters on thick, hard roofs based on blasting technology, so as to solve the problems existing in the prior art and improve the blasting pressure relief effect.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] This invention provides a method for mitigating impact disasters on thick, hard roofs based on blasting technology, comprising:

[0006] Determine the location of the bottom surface of the critical layer;

[0007] If the bottom of the key layer is within 20m above the coal seam, then the blast holes should be constructed from the lower roadway toward the key layer.

[0008] If the working face span is >150m and the bottom of the key layer is within 20-40m above the coal seam, then the blast holes are constructed from the extraction roadway toward the key layer.

[0009] If the working face span is >150m and the bottom of the key layer is within 40-100m above the coal seam, then a high-level roadway is constructed along the working face strike within the key layer, and then the blast holes are constructed from the high-level roadway toward the key layer.

[0010] If the working face span is greater than 150m and the bottom of the key layer is located more than 100m above the coal seam, then the blast holes are drilled from the ground toward the key layer.

[0011] In some implementations, the borehole spacing, row spacing, and charge quantity are designed based on the lithology of the key strata and construction conditions on site.

[0012] In some implementations, the depth of the blast holes is increased, either by increasing the directional borehole depth or by increasing the depth of the blast holes pointing towards the adjacent goaf, in order to cut off the impact of the goaf on the mining face.

[0013] In some implementations, the extraction roadway is located above the key layer, and the blast holes are drilled from top to bottom.

[0014] In some implementations, the elevated tunnel is located below the key layer, and the blast holes are drilled from bottom to top.

[0015] In some implementations, the borehole spacing needs to be designed based on the on-site mining step distance, and the borehole spacing needs to be designed according to the working face direction and roof thickness parameters, so as to ensure the stable and orderly collapse of the roof.

[0016] In some implementations, the working face needs to be accurately positioned on the ground before drilling the borehole from the ground toward the key layer.

[0017] In some implementations, the boreholes are drilled from the ground toward the critical layer, and after the explosive charge is loaded, detonation is initiated using a detonating cord.

[0018] In some implementations, the blast holes are constructed from the lower alley towards the critical layer using a combination of deep and shallow holes.

[0019] In some implementations, if a composite critical layer is present, the corresponding borehole construction method is selected based on the location of each critical layer.

[0020] The present invention achieves the following technical effects compared to the prior art:

[0021] This invention discloses a method for mitigating impact disasters caused by thick, hard roofs based on blasting technology. The core idea is "suppressing disasters with blasting." Starting from the working face span and the location of the thick, hard roof, it classifies different situations of thick, hard roofs overlying the working face and provides corresponding blasting decompression techniques: for small-span, low-lying roofs, blast holes are drilled from the low-lying roadway towards the critical layer; if necessary, ultra-deep blasting holes can be added. For large-span, low-lying roofs, fan-shaped blasting holes are placed under the existing drainage roadway. For large-span, high-lying roofs, fan-shaped blasting holes are placed on the upper part of the high-lying roadway for precise blasting. For large-span, ultra-high-lying roofs, ultra-deep straight-hole blasting is used on the surface. This solves the problem that existing coal mine solutions cannot cover the entire working face area and cannot handle high-lying, thick, hard roofs. The impact disaster mitigation method provided by this invention can flexibly select the corresponding blasting decompression technology according to the working face span and the location of the thick, hard roof, ensuring that the thick, hard roof can collapse smoothly, reducing the impact risk of thick, hard roofs at different layers, and ensuring safe production in the longwall mining face. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a commonly used strike and dip hole blasting pressure relief scheme in coal mines;

[0024] Figure 2 This is a schematic diagram showing the span of the working face and the location of key layers;

[0025] Figure 3 This is the explosion decompression design diagram for scenario 1 of the present invention;

[0026] Figure 4 This is the explosion pressure relief design diagram for scenario 2 of the present invention;

[0027] Figure 5 This is the explosion pressure relief design diagram for scenario 3 of the present invention;

[0028] Figure 6 This is the explosion pressure relief design diagram for scenario 4 of the present invention;

[0029] In the diagram: 1-Strike hole, 2-Dip hole, 3-Key layer, 4-Adjacent goaf, 5-Intake airway, 6-Working face, 7-Directly overlying overburden, 8-Return airway, 9-Retained coal pillar, 10-Working face span, 11-Distance between thick, hard roof and coal seam, 12-Ultra-deep blast hole in low-level roadway, 13-Drainage roadway, 14-Fan-shaped blast hole below drainage roadway, 15-High-level roadway, 16-Fan-shaped blast hole above high-level roadway, 17-Ultra-deep straight hole on the surface, 18-Distance between roof and surface. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the 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.

[0031] The purpose of this invention is to provide a method for mitigating impact disasters on thick, hard roofs based on blasting technology, in order to solve the problems existing in the prior art and improve the blasting pressure relief effect.

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] First, some technical terms involved in the embodiments of this application will be introduced.

[0034] The key layer is the thick, hard roof above the coal seam.

[0035] Low-level airways refer to the intake and return airways of the working face.

[0036] Hole 1 slopes towards the adjacent goaf or working face. This is generally done to sever connection with the adjacent working face or goaf.

[0037] Inclined hole 2, tilted towards the working face.

[0038] Among related technologies, blasting methods are characterized by simple processes, low costs, and minimal disturbance to the surrounding rock when applied to the control of rockburst disasters in coal mines. Furthermore, pressure relief technologies such as strike-and-dip deep-hole blasting and deep-shallow-hole combined blasting have gradually been developed.

[0039] Strike and dip deep-hole blasting: The blast holes are arranged along the strike and dip of the roadway. The strike blast holes treat the roof adjacent to goaf 4 to prevent the roof from collapsing unsuccessfully according to the blast hole spacing, thus preventing the phenomenon of water gushing into the goaf roadway. The dip blast holes treat the roof above the working face.

[0040] Deep and shallow hole combined blasting: To address the issues of critical layers at different locations, the blast holes are divided into upper, middle and lower layers along the working face. Deep holes are the primary critical layer, and shallow holes are the secondary critical layer, ensuring the smooth collapse of the roof of each critical layer.

[0041] Some studies, based on the above-mentioned basic blasting pressure relief methods, utilize shaped charge blasting for directional roof pre-splitting pressure relief, including two types: slotting charge and grooving blasting. By using shaped charge directional slotting technology, through-type fractures are formed deep on both sides of the borehole wall, cutting off the overhanging structure of the roadway and weakening the transmission of stress above the roadway, thereby achieving effective pre-splitting.

[0042] Strike-and-dip deep-hole blasting and combined deep-and-shallow-hole blasting are the most commonly used pressure relief methods in coal mines. They are generally only suitable for small-span working faces and rockburst disasters caused by thick, hard roofs, and are used to solve the deformation problem of roadways left along the goaf. However, with the development of mechanized coal mining, the span of long-arm mining faces has increased to over 200m, and traditional blasting pressure relief schemes cannot cover the entire working face area.

[0043] If the thick, hard roof is far from the working face, the depth of the blast holes will reach over 80 meters. However, the high ground stress and weak rock strata at depth make it difficult to meet the drilling and charging conditions for ultra-deep blast holes. The problem of excessively large superimposed angles leads to frequent hole collapses, with a success rate of no more than 20%. On the one hand, from a horizontal perspective, the area of ​​effect of the blast holes still cannot cover the entire working face; on the other hand, from a vertical perspective, the blast holes cannot penetrate into the thick, hard roof rock strata, and the blasting pressure relief effect is not ideal.

[0044] While traditional blasting for roof cutting can alleviate rockburst problems to some extent, for most mines, this technology is heavily dependent on the working face span and the location of the thick, hard overlying roof. Although some researchers have incorporated shaped charge blasting into traditional blasting methods, increasing the effective range of the blast holes, this has not resulted in significant stress transfer from the overlying strata. The center of the working face and a large area above it still exhibit a strong tendency for rockbursts, and high-energy rockburst events frequently occur.

[0045] The following is combined with Figures 1 to 6 The following describes embodiments of the present invention.

[0046] This invention provides a method for mitigating impact disasters on thick, hard roofs based on blasting technology, comprising:

[0047] Determine the location of the bottom surface of critical layer 3;

[0048] The following working face span is Figures 1-6 The working surface span is 10.

[0049] Scenario 1: If the bottom surface of the critical layer 3 is within 20m above the coal seam, then boreholes are constructed from the lower roadway toward the critical layer 3; the lower roadway refers to the intake airway 5 and return airway 8 of the working face 6. In some cases, some ultra-deep blasting boreholes can be applied to increase the coverage of the boreholes; that is, ultra-deep blasting boreholes 12 in the lower roadway.

[0050] Scenario 2: If the working face span is >150m and the bottom of the key layer 3 is within 20-40m above the coal seam, then blast holes are constructed from the extraction roadway 13 toward the key layer 3; that is, fan-shaped blast holes 14 are placed under the extraction roadway.

[0051] Case 3: If the working face span is >150m and the bottom of the key layer 3 is within 40-100m above the coal seam, then a high-level roadway 15 is constructed along the direction of the working face 6 within the key layer 3, and then the blast holes are constructed from the high-level roadway 15 toward the key layer 3; that is, a fan-shaped blast hole 16 is placed on the high-level roadway.

[0052] Scenario 4: If the working face span is greater than 150m and the bottom of the key layer 3 is located more than 100m above the coal seam, then the blast hole is drilled from the ground toward the key layer 3.

[0053] The distance between the bottom surface of the key layer 3 and the coal seam is 11, which is the distance between the thick, hard roof and the coal seam.

[0054] In this treatment method, if the bottom of the key layer 3 is located within 20m above the coal seam, since the key layer 3 is close to the coal seam and the low roadway, the blasting holes can be directly constructed from the low roadway toward the key layer 3.

[0055] If the working face span is greater than 150m and the bottom of the key layer 3 is within 20-40m above the coal seam, if blast holes are constructed from the low-level roadway toward the key layer 3, the length of the blast holes will be too long, which may easily lead to hole collapse. Therefore, the blast holes are constructed in the extraction roadway 13, which is closer to the key layer 3, in order to achieve the goal of covering as much of the large-span key layer 3 as possible and improve the blasting effect.

[0056] If the working face span is greater than 150m and the bottom of the key layer 3 is within 40-100m above the coal seam, using the extraction roadway 13 to construct blast holes would result in excessively long blast holes, which could easily lead to hole collapse. Therefore, a high-level roadway 15 is constructed within the key layer 3, arranged along the working face 6, and then the blast holes are constructed from the high-level roadway 15 toward the key layer 3. This achieves the goal of covering as much of the large-span key layer 3 as possible, thereby improving the blasting effect.

[0057] If the working face span is greater than 150m and the bottom of the key layer 3 is more than 100m above the coal seam, it will be difficult to construct the high-level roadway 15 along the working face 6 from within the key layer 3. Therefore, it is necessary to drill the blast holes from the ground toward the key layer 3, which is a simpler and more feasible method.

[0058] Specifically, the excavation of the high-level roadway 15 from the low-level roadway to the key layer 3 is divided into two steps. The first step is to excavate the roadway along an upward incline, and the second step is to lay the high-level roadway 15 along the direction of the thick, hard roof. When excavating the roadway from the two roadways (i.e., the low-level roadway) to the high-level thick, hard roof, due to factors such as the weight of the tunneling machine, the inclination angle of the roadway cannot be set too high, and it is set at 15-18° on site. At the same time, the width of the working face 6 using long-arm mining is generally 150m to 300m. Therefore, the limit height of the high-level roadway 15 for relieving pressure on the thick, hard roof can be determined based on this width and the angle of the roadway. Thus, the roof height range for the application of the blasting pressure relief technology in the high-level roadway 15 is 40-100m.

[0059] Lower limit: 150 × tan15° = 40.5m

[0060] Upper limit: 300 × tan18° = 97.5m

[0061] This invention discloses a method for mitigating impact disasters caused by thick, hard roofs based on blasting technology. The core idea is "suppressing disasters with blasting." Starting from the span of the working face and the location of the thick, hard roof, different scenarios of thick, hard roofs over the working face 6 are identified, and corresponding blasting decompression techniques are provided: for small-span, low-lying roofs, blasting holes are drilled from the low-lying roadway towards the critical layer 3; if necessary, ultra-deep blasting holes can be added. For large-span, low-lying roofs, fan-shaped blasting holes are placed below the existing extraction roadway 13. For large-span, high-lying roofs, precise blasting is performed using fan-shaped blasting holes placed above the high-lying roadway 15. For large-span, ultra-high-lying roofs, ultra-deep straight holes 17 are used for blasting. This solves the problem that existing coal mine solutions cannot cover the entire working face 6 area and cannot handle high-lying, thick, hard roofs. The impact disaster mitigation method provided by this invention can flexibly select the corresponding blasting decompression techniques according to the working face span and the location of the thick, hard roof, ensuring the smooth collapse of the thick, hard roof, reducing the impact risk of thick, hard roofs at different layers, and guaranteeing safe production in the longwall mining face 6.

[0062] In some embodiments, the borehole spacing, row spacing, and charge quantity are designed based on the lithology of the key layer 3 on site and the construction conditions.

[0063] This embodiment can further improve the blasting and pressure relief effect.

[0064] Specifically, in some examples, the borehole spacing needs to be designed according to the on-site mining step distance, and the borehole spacing needs to be designed according to the working face 6 direction and the thickness parameters of the roof, so as to ensure the stable and orderly collapse of the roof.

[0065] In particular, the spacing of the blast holes in the extraction roadway 13 and the high-level roadway 15 needs to be designed according to the on-site mining step distance, and the spacing between the blast holes needs to be designed according to parameters such as the orientation of the working face 6 and the thickness of the roof, so as to ensure the stable and orderly collapse of the roof.

[0066] In some embodiments, the depth of the blast hole or the blast hole pointing to the adjacent goaf 4 is increased to cut off the impact of the goaf on the mining of the working face 6.

[0067] This embodiment is applicable to blasting any critical layer 3 at any location. This effectively cuts off the impact of the goaf on the mining face 6, ultimately improving the blasting effect.

[0068] In some embodiments, the extraction roadway 13 is located above the critical layer 3, and the blast holes are drilled from top to bottom. In some examples, when the extraction roadway 13 is located below the critical layer 3, the blast holes are drilled from bottom to top. In this embodiment, the extraction roadway 13 is opened outside the critical layer 3.

[0069] In some embodiments, the elevated tunnel 15 is located below the critical layer 3, and the blast holes are drilled from bottom to top. In some examples, when the elevated tunnel 15 is located above the critical layer 3, the blast holes are drilled from top to bottom. In this embodiment, the elevated tunnel 15 is opened inside the critical layer 3.

[0070] In some embodiments, before drilling boreholes from the ground toward the critical layer 3, it is necessary to accurately position the working face 6 on the ground.

[0071] In some embodiments, boreholes are drilled from the ground toward the critical layer 3, and after the explosives are loaded, detonation is initiated using a detonating cord.

[0072] In some embodiments, the blast holes are constructed from the lower alley toward the key layer 3 using a combination of deep and shallow holes.

[0073] In some embodiments, if a composite key layer 3 is present, the corresponding borehole construction method is selected according to the position of each key layer 3.

[0074] In this embodiment, the composite key layer is that key layer 3 appears at different heights. Therefore, it is necessary to survey the location and span of each key layer 3, and then carry out corresponding blast hole construction for key layers 3 at different locations and spans according to the above embodiment.

[0075] For example, if the bottom surface of the first key layer 3 is 10m above the coal seam and has a span of 150m, and the bottom surface of the second key layer 3 is 30m above the coal seam and has a span of 160m, then the first key layer 3 applies to case 1, and the second key layer 3 applies to case 2. The blast holes for the first key layer 3 are constructed from the lower roadway towards the key layer 3. The blast holes for the second key layer 3 are constructed from the extraction roadway 13 towards the key layer 3.

[0076] More specific embodiments of the present invention are as follows:

[0077] First, conduct on-site exploration to determine the span of the longwall face and the location of the thick, hard roof. Then, adopt different blasting and decompression techniques for the thick, hard roof under different conditions.

[0078] If the thick, hard roof is located within 20m above the coal seam, in the original scheme (i.e. Figure 1 Based on the deep hole blasting (shown in the diagram), ultra-deep blasting holes are added along the working face at the 6th dip to address the pressure relief problem of the thick and hard roof in the central area. The depth and angle (elevation angle) of the ultra-deep blasting holes are designed according to the thickness of the central area and the span of the working face without affecting the original hole layout.

[0079] If the working face span is >150m and the thick hard roof is located within 20-40m above the coal seam, fan-shaped blasting is arranged in the extraction roadway 13. The original blasting holes can no longer meet the needs of the large-span working face 6. The existing extraction roadway 13 is used to arrange fan-shaped blasting holes downward to the thick hard roof. The depth and angle (plunge angle) of the blasting holes are designed according to the coverage of the thick hard roof.

[0080] If the working face span is greater than 150m and the thick, hard roof is located within 40-100m above the coal seam, high-level roadway 15 blasting is directly adopted. High-level roadway 15 is excavated from the low-level roadway to the bottom of the thick, hard roof along the strike. In high-level roadway 15, fan-shaped blast holes are arranged to blast and relieve pressure on the thick, hard roof. The depth and angle (elevation angle) of the blast holes are designed according to the coverage range of the thick, hard roof.

[0081] If the working face span is greater than 150m and the thick, hard roof is located more than 100m above the coal seam, ultra-deep straight-hole blasting (17) is used. The location of the working face (6) is determined on the ground, especially confirming the distance (18) between the roof and the ground. Ultra-deep holes are drilled from the ground towards the location of the thick, hard roof, and blasting is carried out using detonating cord. The hole depth is designed based on the roof thickness.

[0082] The method provided by this invention has the following advantages compared with existing technologies:

[0083] 1. The blasting and decompression technology provided by this invention can achieve full coverage of the working face 6 in the working face 6 under different conditions.

[0084] 2. The high-level tunnel blasting method can achieve precise pressure relief of the thick and hard roof at high levels in the working face;

[0085] 3. Combining the low-level roadway scheme, blasting in extraction roadway 13 or high-level roadway 15 can achieve the blasting pressure relief target of the composite key layer.

[0086] 4. The method can flexibly cope with thick and hard roofs in different locations, and at the same time meet the requirements for impact disaster control of small-span and large-span working faces.

[0087] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for mitigating impact disasters on thick, hard roofs based on blasting technology, characterized in that: include: Determine the location of the bottom surface of the critical layer; If the bottom of the key layer is within 20m above the coal seam, then the blast holes should be constructed from the lower roadway toward the key layer. If the working face span is >150m and the bottom of the key layer is within 20-40m above the coal seam, then the blast holes are constructed from the extraction roadway toward the key layer. If the working face span is >150m and the bottom of the key layer is within 40-100m above the coal seam, then a high-level roadway is constructed along the working face strike within the key layer, and then the blast holes are constructed from the high-level roadway toward the key layer. If the working face span is greater than 150m and the bottom of the key layer is located more than 100m above the coal seam, then the blast holes are drilled from the ground toward the key layer.

2. The method for mitigating impact disasters on thick, hard roofs based on blasting technology according to claim 1, characterized in that: The design of borehole spacing, row spacing, and charge quantity is based on the lithology of the key strata and construction conditions.

3. The method for mitigating impact disasters on thick, hard roofs based on blasting technology according to claim 1, characterized in that: Increase the depth of blast holes pointing towards the adjacent goaf to cut off the impact of the goaf on the working face.

4. The method for mitigating impact disasters on thick, hard roofs based on blasting technology according to claim 2, characterized in that: The extraction roadway is located above the key layer, and the blast holes are drilled from top to bottom.

5. The method for mitigating impact disasters on thick, hard roofs based on blasting technology according to claim 2, characterized in that: The elevated tunnel is located below the key layer, and the blast holes are drilled from bottom to top.

6. The method for mitigating impact disasters on thick, hard roofs based on blasting technology according to claim 2, characterized in that: The spacing between the blast holes needs to be designed based on the on-site mining step distance, while the spacing between the blast holes needs to be designed according to the working face direction and the thickness parameters of the roof, so as to ensure the stable and orderly collapse of the roof.

7. The method for mitigating impact disasters on thick, hard roofs based on blasting technology according to claim 2, characterized in that: Before drilling the borehole from the ground toward the key layer, it is necessary to accurately position the working face on the ground.

8. The method for mitigating impact disasters on thick, hard roofs based on blasting technology according to claim 2, characterized in that: The borehole is drilled from the ground toward the key layer, and after the explosive charge is loaded, it is detonated using a detonating cord.

9. The method for mitigating impact disasters on thick, hard roofs based on blasting technology according to claim 2, characterized in that: The blast holes are constructed from the lower-level alley towards the key layer using a combination of deep and shallow holes.

10. The method for mitigating impact disasters on thick, hard roofs based on blasting technology according to claim 1, characterized in that: If a composite critical layer is present, the corresponding borehole construction method shall be selected according to the location of each critical layer.

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