Whole-layer presplitting blasting pressure relief method

Abstract

The invention discloses a whole-layer presplitting blasting pressure relief method, which relates to the technical field of blasting pressure relief, and comprises the following steps of: 1, determining the position of a key layer; secondly, blast holes are constructed in a top area, close to the top, of the key layer, a bottom area, close to the bottom, of the key layer and a middle area between the top area and the bottom area; thirdly, the blast holes in the top area and the bottom area are filled with energy-gathered cartridges, and the included angle between the energy-gathered direction of the energy-gathered cartridges and the horizontal direction is smaller than 10 degrees; the blast hole in the middle area is filled with a common cartridge bag; and fourthly, the energy-gathered cartridge bag is detonated firstly, and then the common cartridge bag is detonated. When the method is implemented, the man-made energy release belt is formed on the upper portion and the lower portion of the key layer in an energy-gathered cutting mode, then blasting pressure release is conducted on the key layer, the man-made energy release belt can obstruct the stress redistribution and energy transfer process, and therefore the rock burst risk of the thick and hard top plate can be greatly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of blasting pressure relief, in particular to a whole-layer pre-splitting blasting pressure relief method. Background Art

[0002] In recent years, with the exponential growth of energy consumption, the contradiction between coal supply and demand has become increasingly intensified. Furthermore, shallow coal reserves are limited and cannot meet the needs of enterprises for coal, so they have turned their attention to deep coal mining. However, high stress and horizontal dominant stress have become the norm in deep areas, and joints, bedding, fissures, faults, and fracture zones are widely developed. The stress environment and occurrence conditions of the rock mass are extremely prone to rock burst accidents. Based on the need for safe and efficient mining of rock burst mine working faces, blasting-based pressure relief methods have shown significant advantages in rock burst disaster management, especially for roof pressure relief solutions, which are essentially blasting technology. The principle of blasting in pressure relief engineering is to use the shock wave generated by the explosion of explosives to break the rock and create cracks, improve the properties of the surrounding rock, and ultimately form a loose zone around the blast hole, providing space for the release and compensation of high ground stress.

[0003] At present, in the process of on-site application in coal mines, pressure relief methods such as strike and dip blasting, combined blasting of deep and shallow holes, and pre-splitting blasting of the entire layer of high-level lanes have been formed. However, all blasting pressure relief technologies are inseparable from the fan-shaped blastholes inclined to the working face. The blasthole spacing is arranged in combination with geological conditions such as roof thickness and lithology, and the blasthole row spacing is more often arranged according to the on-site mining pitch. This is to achieve the purpose of roof cutting and pressure relief, change the original stress transmission path of the basic roof, and effectively transfer the pressure of the overlying rock strata to the goaf. However, neither the upward stress redistribution process nor the downward energy transfer process (deep rock crushing) can block the impact of the two processes on the working face, and the pressure relief effect is not ideal. Summary of the Invention

[0004] The purpose of the present invention is to provide a whole-layer pre-splitting blasting pressure relief method to solve the problems existing in the above-mentioned prior art and improve the pressure relief effect.

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

[0006] The present invention provides a whole-layer pre-splitting blasting pressure relief method, comprising:

[0007] Step 1: Determine the key layer location;

[0008] Step 2: constructing blastholes in the top area near the top, the bottom area near the bottom, and the middle area between the top area and the bottom area of ​​the key layer;

[0009] Step 3: Filling shaped charges into the blastholes in the top and bottom regions, with the angle between the shaped charge's focusing direction and the horizontal direction being less than 10 degrees; and filling ordinary charges into the blastholes in the middle region;

[0010] Step 4: Detonate the shaped charge first, then the ordinary charge.

[0011] Preferably, in step 2, if the bottom surface of the key layer is within the range of 0 to 10 m above the coal seam, all blastholes are drilled from the air intake lane and the return air lane toward the key layer; if the bottom surface of the key layer is within the range of 10 to 40 m above the coal seam, the extraction lane is arranged in the key layer and all blastholes are drilled from the extraction lane toward the key layer; if the bottom surface of the key layer is within the range of 40 to 100 m above the coal seam, a high-level lane arranged along the direction of the working face is first constructed in the key layer, and then the blastholes are drilled from the high-level lane toward the key layer.

[0012] Preferably, the blast holes in the central area are arranged in a plum blossom pattern.

[0013] Preferably, in step 4, a digital electronic detonator is used for delayed detonation when detonating the ordinary explosive package.

[0014] Preferably, the angle of the blastholes drilled from the air inlet tunnel and the return air tunnel toward the key layer is 10 to 30 degrees.

[0015] Preferably, if there are two key layers, the lower key layer is decompressed by using the transverse "fan-shaped cutting top" method; the upper key layer is decompressed by using the decompression methods in the above steps 2 to 4.

[0016] Preferably, if a blasthole collapses or charging fails, a reinforced blasthole is added next to the blasthole, or cross holes are arranged on both sides of the blasthole to provide new free surfaces for blasting the upper and lower and left and right blastholes, thereby achieving the purpose of weakening the integrity of the roof.

[0017] Preferably, the optimal delay time for delayed blasting is determined based on the detection of the fracture zone in the on-site blasting test.

[0018] Preferably, both the shaped charge and the ordinary charge are forward detonated.

[0019] Preferably, the length and angle of a single row of blastholes are designed according to geological conditions and the thickness of the key layer, and the spacing between two adjacent rows of blastholes is arranged according to the mining step spacing of the working face.

[0020] Compared with the prior art, the present invention has achieved the following technical effects:

[0021] When the present invention is implemented, an artificial energy release belt is first formed by energy-concentrated cutting at the upper and lower parts of the key layer, and then the key layer is blasted to release pressure. The artificial energy release belt can block the stress redistribution and energy transfer process, thereby greatly reducing the risk of impact ground pressure of thick hard roof. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 This is a schematic diagram of the traditional blasting decompression scheme;

[0024] Figure 2 Schematic diagram of the blasting pressure relief effect of the key layer of the present invention

[0025] Figure 3 A schematic diagram of the arrangement of the upper, middle and lower blastholes in the whole-layer pre-splitting blasting pressure relief method provided by the present invention;

[0026] Figure 4 The diagram of blasthole arrangement is shown when the bottom of the key layer is within the range of 0 to 10 m above the coal seam.

[0027] Figure 5 This is a schematic diagram of the blasthole arrangement for the upper and lower composite key layers;

[0028] Figure 6 A schematic diagram of a reinforced blasthole next to the blasthole when the blasthole collapses or charging fails;

[0029] Figure 7 When the hole collapses or the charge is unsuccessful, a schematic diagram of cross hole arrangement is made on both sides of the blasthole;

[0030] In the figure: 1-strike blasthole; 2-inclined blasthole; 3-key layer; 4-adjacent goaf; 5-retained coal pillar; 6-air inlet lane; 7-working face; 8-return air lane; 9-working face width; 10-distance between thick hard roof and working face; 11-energy focusing direction; 13-central crushing area; 14-ordinary explosive package delayed blasting area; 16-energy focusing blasting area; 18-energy focusing blasthole; 19-ordinary blasting blasthole; 20-plum blossom type hole area; 21-extraction lane; 22-upper energy release zone area; 23-lower pressure relief area; 26-collapse hole position; 27-enhanced blasthole; 28-cross hole. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] The purpose of the present invention is to provide a whole-layer pre-splitting blasting pressure relief method to solve the problems existing in the prior art and improve the pressure relief effect.

[0033] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] First, some technical terms involved in the embodiments of this application are introduced.

[0035] The key layer is the thick hard roof above the coal seam.

[0036] Shaped charge, a shaped charge is a special blasting device that uses the concave part of the charge to concentrate the explosive energy in a local area, thereby enhancing the penetration and fragmentation ability of the charge in a specific direction.

[0037] The working principle of shaped charges is based on the focused charge effect. This is achieved through the special shape of the charge (such as the concave cavity), which concentrates the explosive energy in a small area, forming a high-density, high-velocity, and high-pressure gas jet. This jet increases the explosive power, giving the shaped charge a strong destructive force in a specific direction.

[0038] Among the related technologies, rock burst prevention and control technologies mainly include coal seam water injection, borehole pressure relief, hydraulic fracturing, blasting-based roof and floor blasting and coal seam pressure relief. The first three are widely used in the field of rock burst disaster management and coalbed methane extraction in shallow coal mines. For deep coal mines, thanks to the characteristics of blasting such as simple process and good pressure relief effect, the proportion of rock burst prevention and control applications with blasting technology as the core accounts for 40%. In deep coal mines, based on their own characteristics, pressure relief methods such as strike and dip hole blasting, deep and shallow hole combination blasting, and high-level lane whole-layer pre-splitting blasting have been formed, and technologies such as large-diameter deep hole blasting, delayed detonation, and concentrated energy blasting (slit charging and blasthole grooving) have been successively applied in coal mine roof and floor blasting and coal seam pressure relief projects. Thus, a rock burst prevention and pressure relief system for deep coal mines is constructed.

[0039] Coal seam water injection: Before mining, pressurized water is injected into the coal seam through drilling holes to pre-wet the coal body. Water can change the mechanical properties of the coal and make the stress distribution uniform, thereby preventing the occurrence of coal explosion.

[0040] Drilling pressure relief: Drill holes in the high stress areas of the roof and floor plates, and use artificial methods to reduce the stress environment of the surrounding rock or change the stress distribution of the surrounding rock, so that the peak support pressure is transferred to the deep part of the surrounding rock. While transferring the high stress around the tunnel, it can also provide effective compensation space for the expansion and deformation of the surrounding rock, absorb part of the deformation, and thus reduce the scope of surrounding rock rupture.

[0041] Hydraulic fracturing: Drill holes are drilled from the roof of the two tunnels to the side of the goaf at a small angle to the plumb line. Through segmented hydraulic fracturing in the drill holes, a leading crack is formed in the hard rock layer overlying the tunnel along the axial direction of the tunnel, thereby cutting off the lateral cantilever structure above the goaf, thereby achieving the purpose of reducing the confining pressure stress in the tunnel.

[0042] Strike and Dip Hole Blasting: Blast holes are arranged along the strike and dip of the trench. Strike hole 1 is angled toward the adjacent goaf 4, cutting off the cantilever structure adjacent to goaf 4. Dip hole 2 is angled toward the overlying roof of the working face, alleviating the pressure of the thick, hard roof on the working face.

[0043] Combined deep and shallow hole blasting: Fan-shaped blast holes are arranged along the inclined working face of the trench. Dip hole 2 uses three different lengths of blast holes: deep, medium and shallow to solve the problem of anti-blowout and pressure relief of the composite key layer of the overlying roof.

[0044] Whole-layer pre-splitting blasting of high-level tunnels: construct high-level tunnels from the air intake tunnel or return air tunnel to the high-level thick hard roof, arrange them along the direction of the working face, and construct fan-shaped hole blasting from the high-level tunnel to achieve whole-layer pre-splitting blasting of the thick hard roof, solving the problem of anti-impact and pressure relief of the high-level thick hard roof.

[0045] Traditional pressure relief methods include coal seam water injection, borehole pressure relief, and hydraulic fracturing. A comprehensive set of pressure relief methods has been developed around drilling to address coal seam pressure (coal seam water injection), working face roof and floor pressure (borehole pressure relief), and pressure in adjacent goafs (hydraulic fracturing). This method has achieved good results in shallow coal seams. However, coal mining has begun to shift to deeper depths (mining depths > 600m). The high stress environment at depth creates complex internal rock structures, leading to borehole collapse, stress concentration, and dense cracks, making traditional pressure relief methods unsuitable.

[0046] Pressure relief methods with blasting as the core (blasting of strike and dip holes, combined blasting of deep and shallow holes, and pre-splitting blasting of the entire layer of high-level tunnels). Pressure relief technology with blasting as the core has been widely used in deep coal mines, and the trial of new technologies has gradually formed a blasting pressure relief and anti-blowout system (large-diameter deep hole blasting, delayed detonation, and concentrated energy blasting (slit charging and blasthole grooving)). However, all blasting pressure relief technologies are inseparable from fan-shaped blastholes inclined to the working face. The blasthole spacing is arranged in combination with geological conditions such as roof thickness and lithology, and the blasthole row spacing is more often arranged according to the on-site mining step spacing, so as to achieve the purpose of top cutting and pressure relief, change the original stress transmission path of the basic roof, and effectively transfer the pressure of the overburden to the goaf. However, neither the upward stress redistribution process nor the downward energy transfer process (deep rock crushing) can block the impact of the two processes on the working face, and the pressure relief effect is not ideal.

[0047] In response to the above problems, an embodiment of the present invention proposes a whole-layer pre-splitting blasting pressure relief method, which uses shaped charges to form horizontal through-cracks in the upper and lower parts of the key layer, and at the same time uses delayed detonation to increase the crushing effect of the middle area. On the one hand, it achieves the purpose of weakening the thick and hard roof, and on the other hand, it forms an "artificial energy release zone" between the deep rock layer and the working face, thereby blocking the stress redistribution and energy transfer process, thereby greatly reducing the impact ground pressure risk of the high-position thick and hard roof.

[0048] The following combination Figures 1 to 7 , describing embodiments of the present invention.

[0049] The present invention provides a whole-layer pre-splitting blasting pressure relief method, comprising:

[0050] Step 1: Determine the location of key layer 3;

[0051] Step 2: construct blastholes in the top area near the top, the bottom area near the bottom, and the middle area between the top area and the bottom area of ​​the key layer 3;

[0052] Step 3: Load shaped charges into the blastholes in the top and bottom regions, with the angle between the shaped charge's focusing direction and the horizontal direction being less than 10 degrees; load ordinary charges into the blastholes in the middle region;

[0053] Step 4: Detonate the shaped charge first. The loose areas formed by the explosion of the upper and lower shaped charges need to be connected, so that a barrier belt or artificial energy release belt can be formed at the top and bottom of the key layer 3, such as Figure 2 The shaped charge blasting area 16 in the middle is then detonated with the ordinary charge. That is, the ordinary charge in the middle area is delayed detonation, and its blasting area is the ordinary charge delayed blasting area 14. The optimal delay time for delayed detonation should be determined based on the crack zone detection of the on-site blasting test, such as Figure 2As shown, conventional explosive charges are used to blast the central crushing area 13 .

[0054] It can be understood that the above energy focusing direction can be approximately horizontal, such as Figure 2 The energy focusing direction is shown in 11.

[0055] Figure 2 The downward arrow in the figure indicates the direction of energy transfer from top to bottom; the upward arrow indicates the direction of stress redistribution energy transfer from bottom to top.

[0056] When the present invention is implemented, an artificial energy release belt is first formed by energy-gathering cutting at the upper and lower parts of the key layer 3, and then the key layer 3 is blasted to release pressure. The artificial energy release belt can block the stress redistribution and energy transfer process, thereby greatly reducing the impact ground pressure risk of the thick hard roof. It can be understood that the detonation of the ordinary charge must be realized after the blasting of the shaped charge and the horizontal cutting are completed, so as to achieve a better stress barrier effect.

[0057] like Figure 4 The upper blast holes and the lower blast holes are energy-gathering blast holes 18 , and the middle blast holes are ordinary blast holes 19 .

[0058] Considering that the current deep coal mine working face 7 adopts a long-wall mining method with a span of more than 200m, Figure 1 (the width of the working face 9 and the length >1000m) are required to ensure that the blastholes cover the entire working face 7. In some embodiments, in step 2, if the bottom surface of the key layer 3 is within the range of 0-10m above the coal seam, all blastholes are drilled from the air intake tunnel 6 and the return air tunnel 8 toward the key layer 3, with the angle of the blastholes being 10-30°; if the bottom surface of the key layer 3 is within the range of 10-40m above the coal seam, the extraction tunnel 21 is arranged in the key layer 3 and all blastholes are drilled from the extraction tunnel 21 toward the key layer 3; if the bottom surface of the key layer 3 is within the range of 40-100m above the coal seam, a high-level tunnel arranged along the direction of the working face 7 is first constructed in the key layer 3, and then blastholes are drilled from the high-level tunnel toward the key layer 3.

[0059] The distance between the bottom of the key layer 3 and the coal seam is Figure 1 The distance between the thick hard top plate and the working surface is 10.

[0060] In this embodiment, the angle of the blasthole is greatly reduced in the air inlet tunnel 6 and the return air tunnel 8 (both tunnels are low-level tunnels), and the extraction tunnel 21 or high-level tunnel is directly arranged in the key layer 3, which is beneficial to increase the coverage area of ​​the blasthole and thus improve the blasting effect.

[0061] For example Figure 4As shown, in some examples, in order to cut off the connection between the key layer near the goaf 4 and the key layer above the goaf, if the borehole is constructed in the low-position roadway, it is necessary to increase the strike hole, if the borehole is constructed in the extraction roadway and the high-position roadway, it is necessary to set some boreholes to cut off the connection with the goaf, that is, to extend the depth of the part of the borehole, so that the part of the borehole is extended to above the goaf 4 or into the goaf, and then the vertical shaped charge blasting or ordinary blasting can be used.

[0062] In some examples, the boreholes in the middle region are arranged in the form of a quincunx borehole pattern. The quincunx borehole pattern is a commonly used borehole arrangement in engineering blasting or other related fields. In the quincunx borehole pattern, the boreholes are arranged in a pattern like a quincunx. Specifically, the boreholes are arranged in staggered rows and columns, as shown in Figure 3 As shown, the positions of the two adjacent rows of boreholes are staggered, so that the distribution of the boreholes is similar to the petals of a quincunx, hence the name quincunx borehole pattern.

[0063] This embodiment is beneficial to improve the blasting effect.

[0064] In some examples, in step four, the digital electronic detonator is used for delay blasting when the ordinary explosive package is detonated.

[0065] This embodiment provides a delay blasting method with high safety.

[0066] In some examples, if there are two layers of key layers 3, the lower key layer 3 uses ordinary roof cutting pressure relief, such as the lower pressure relief region 23 in Figure 5 , specifically, transverse "fan-shaped roof cutting" pressure relief; and the upper key layer 3 uses the pressure relief method in steps two to four above for pressure relief, such as the upper energy release zone 22 in Figure 5 .

[0067] The above examples take into account that the purpose of the pressure relief method in steps two to four is to artificially construct an energy release zone between the coal mining face and the high-position overburden strata, to absorb (dissipate) the energy released by the overburden strata due to tectonic stress (rock rupture due to strata movement). This is the main purpose. For the key layer directly above the working face (i.e. the lower key layer), the energy from the high position cannot be transmitted to this position, and the threat to the working face is small, so only ordinary block blasting is required.

[0068] In some examples, if the borehole collapses or the charging is unsuccessful, such as the collapsed borehole position 26, an enhanced borehole 27 is arranged beside the borehole, or cross holes 28 are arranged on both sides of the borehole, to provide new free surfaces for the upper and lower and left and right borehole blasting, to achieve the purpose of weakening the overall integrity of the roof.

[0069] This embodiment is beneficial to improve the stability and reliability of the blasting.

[0070] In some embodiments, both the shaped charge and the ordinary charge are forward detonated.

[0071] In some embodiments, the length and angle of a single row of blastholes are designed according to geological conditions and the thickness of the key layer 3 , and the spacing between two adjacent rows of blastholes is arranged according to the mining pitch of the working face 7 .

[0072] The basic idea of ​​the whole-layer pre-splitting blasting pressure relief method provided by the present invention is to form an "artificial energy release belt" in the form of horizontal shaped charges in the uppermost and lowermost blastholes of the thick hard roof, and to fragment the central area of ​​the middle-layer blastholes by delayed detonation, thereby achieving the purpose of weakening the roof, weakening and blocking the energy transfer from deep rock formations to the working face 7, and solving the problem of strong impact tendency of the longwall mining working face 7. The core idea is "two cuts and one blast". The blasting pressure relief method can reasonably set the length, angle and spacing of the blastholes according to the location of the thick hard roof on site, and determine the optimal delay time in combination with field tests to ensure that the roof can be fully weakened and reduce the risk of impact ground pressure of the roof on the working face 7.

[0073] This patented invention is a whole-layer pre-splitting blasting and pressure relief method based on a shaped charge and delayed detonation, creating an "artificial energy relief belt." This method applies directional fracture and delayed detonation to blasting and pressure relief engineering, creating an "artificial energy relief belt" through a "two-cut, one-blast" hole pattern. This weakens and blocks energy transfer from deep rock formations to the working face. Compared to existing technologies, this method has the following advantages:

[0074] 1. The directional fracture technology of shaped charges can form ultra-long main fractures in the horizontal direction, which can meet the requirements of on-site mining step distance. The main fractures of each blasthole are connected to form a barrier zone, blocking the connection between the roof and the upper and lower rock layers.

[0075] 2. The plum blossom-shaped perforation area 20 achieves optimal fragmentation of the barrier zone, which, on the one hand, weakens the thick hard roof layer, and on the other hand, ultimately transforms the thick hard roof layer into an "artificial energy dissipation zone";

[0076] 3. The “energy dissipation zone” can effectively reduce the impact risk from the overlying rock strata. The energy transmitted from the deep rock strata to the working face 7 is reflected and refracted in the broken area of ​​the stratum in the form of waves, maximizing the energy consumption in the energy transfer process.

[0077] 4. This method can adapt to thick hard roofs at different levels. At the same time, combined with the ultra-deep hole scheme of the low-level lane, it can realize the blasting decompression of thick hard roofs at multiple levels.

[0078] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A whole-layer pre-splitting blasting pressure relief method, characterized by: include: Step 1: Determine the key layer location; Step 2: constructing blastholes in the top area near the top, the bottom area near the bottom, and the middle area between the top area and the bottom area of ​​the key layer; Step 3: Filling shaped charges into the blastholes in the top and bottom regions, with the angle between the shaped charge's focusing direction and the horizontal direction being less than 10 degrees; and filling ordinary charges into the blastholes in the middle region; Step 4: Detonate the shaped charge first, then the ordinary charge.

2. The whole-layer pre-splitting blasting pressure relief method according to claim 1 is characterized in that: In step 2, if the bottom surface of the key layer is within the range of 0 to 10 m above the coal seam, all blastholes are drilled from the air intake lane and the return air lane toward the key layer; if the bottom surface of the key layer is within the range of 10 to 40 m above the coal seam, the extraction lane is arranged in the key layer and all blastholes are drilled from the extraction lane toward the key layer; if the bottom surface of the key layer is within the range of 40 to 100 m above the coal seam, a high-level lane arranged along the working face direction is first constructed in the key layer, and then the blastholes are drilled from the high-level lane toward the key layer.

3. The whole-layer pre-splitting blasting pressure relief method according to claim 2, characterized in that: The blast holes in the middle area are arranged in a plum blossom pattern.

4. The whole-layer pre-splitting blasting pressure relief method according to claim 1 is characterized in that: In step 4, a digital electronic detonator is used to perform delayed detonation when detonating ordinary explosive packs.

5. The whole-layer pre-splitting blasting pressure relief method according to claim 2, characterized in that: The angle of the blast holes drilled from the air inlet tunnel and the return air tunnel toward the key layer is 10 to 30 degrees.

6. The whole-layer pre-splitting blasting pressure relief method according to claim 1, characterized in that: If there are two key layers, the lower key layer is decompressed by cutting the top; the upper key layer is decompressed by the decompression method in steps 2 to 4 above.

7. The whole-layer pre-splitting blasting pressure relief method according to claim 1 is characterized in that: If a blasthole collapses or charging fails, a reinforced blasthole will be added next to the blasthole, or cross holes will be arranged on both sides of the blasthole to provide new free surfaces for blasting the upper and lower and left and right blastholes, so as to achieve the purpose of weakening the integrity of the roof.

8. The whole-layer pre-splitting blasting pressure relief method according to claim 4, characterized in that: The optimal delay time for delayed blasting should be determined based on the detection of the crack area during the on-site blasting test.

9. The whole-layer pre-splitting blasting pressure relief method according to claim 4, characterized in that: The shaped charge and the common charge both adopt forward detonation.

10. The whole-layer pre-splitting blasting pressure relief method according to claim 4, characterized in that: The length and angle of a single row of blastholes are designed according to the geological conditions and the thickness of the key layer, and the spacing between two adjacent rows of blastholes is arranged according to the mining step spacing of the working face.

Images