Blasting pressure relief method for high-level top plate of large-span long-wall working face

Abstract

The invention discloses a blasting pressure relief method for a high-level top plate of a large-span long-wall working face, and relates to the technical field of coal mining, and the blasting pressure relief method comprises the following steps: S1, determining a blasting working condition according to field exploration data; s2, a plurality of blast holes distributed in the mining direction of the large-span long-wall working face in parallel at intervals are designed according to the blasting working conditions, each blast hole comprises an arc-shaped section and a straight line section completely located in the high-level top plate, and one end of each arc-shaped section penetrates into the high-level top plate and communicates with one end of the corresponding straight line section; the length of each blast hole in the length direction of the large-span long-wall working face is larger than that of the large-span long-wall working face; s3, drilling construction is conducted on all the blast holes; s4, all the blast holes are subjected to charging and plugging; and S5, all the blast holes are detonated. The blast holes cover the long-wall working face, and whole-layer presplitting blasting of the high-position thick and hard top plate can be achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coal mining, in particular to a blasting pressure relief method for high-level roof of large-span longwall face. BACKGROUND

[0002] With the continuous increase of coal mining depth, the probability of rock burst disaster greatly increases. As a very mature technology applied in underground coal mine, blasting shows obvious advantages in the aspect of roof rock burst disaster control. The main principle is to use the shock wave generated by the explosion of explosives to make the rock break and crack, and finally form a loose zone around the blasting hole, and the loose zones of each blast hole connect to form a weak zone (pressure relief zone), which provides a release compensation space for high stress.

[0003] The traditional coal mine blasting pressure relief technology can generally only deal with the rock burst disaster of small-span working face (span < 150m). Although it well cuts off the connection between the adjacent goaf and the coal mining face, and solves the problem of rock burst pressure relief of immediate roof and basic roof. However, with the high development of coal mining mechanization, large-span longwall face has become a common state, and the span of large-span longwall face basically maintains more than 200m, so the original blasting pressure relief technology cannot cover the entire working face.

[0004] When encountering a high-level thick and hard roof of 40m-100m above the coal seam, and a complex deep geostress environment, soft and weakly cemented lithology, and the coverage range of fan-shaped blast hole angle, it is difficult to meet the blasting pressure relief conditions of super-deep blast hole, so traditional coal mine blasting pressure relief technologies such as strike and tendency deep hole blasting, cutting seam charge shaped charge blasting, digital electronic detonator delay blasting, and deep and shallow hole combined blasting are helpless. From the horizontal point of view, the blast hole action area still cannot cover the entire working face; from the vertical point of view, the blast hole cannot penetrate into the high-level thick and hard roof rock layer.

[0005] Although some researches have proposed high-level roadway blasting pressure relief technology, which means excavating a high-level roadway from the crossheading to the target layer, and arranging it along the strike of the working face, so as to realize the precise blasting pressure relief of high-level thick and hard roof. Although the high-level roadway blasting pressure relief technology can solve the problem of rock burst of high-level thick and hard roof, it can only deal with the small area of thick and hard roof existing in high-level, and if the thick and hard roof covers the entire working face, the technology needs to consume more manpower, material resources and financial resources, and the excavation construction of high-level roadway still needs a lot of time, so it is not suitable for wide application. SUMMARY

[0006] The purpose of the present application is to provide a blasting pressure relief method for high-level roof of large-span longwall face, so as to solve the problems existing in the prior art and improve the pressure relief effect of high-level roof of large-span longwall face.

[0007] To achieve the above object, the present application provides the following scheme:

[0008] The present application provides a blasting pressure relief method for high-position roof of large-span longwall face, comprising the following steps:

[0009] Step S1, determining the blasting condition according to the field exploration data, wherein the blasting condition comprises the position of the high-position roof needing to be blasted for pressure relief, the thickness of the high-position roof, the lithology of the high-position roof, the lithology of the rock stratum between the high-position roof and the coal seam, and the span of the large-span longwall face;

[0010] Step S2, designing a plurality of blast holes parallelly and spacedly distributed along the mining direction of the large-span longwall face according to the blasting condition, wherein each blast hole comprises an arc segment and a straight segment all located in the high-position roof, one end of the arc segment penetrates into the high-position roof and communicates with one end of the straight segment, and the other end of all the arc segments is located at the top of the air intake roadway or at the top of the air return roadway; the length of each blast hole along the length direction of the large-span longwall face is greater than the length of the large-span longwall face;

[0011] Step S3, drilling all the blast holes by using a kilometer directional drilling machine;

[0012] Step S4, charging and plugging all the blast holes;

[0013] Step S5, detonating all the blast holes.

[0014] Preferably, the axis of each blast hole is located in a vertical plane parallel to the large-span longwall face; the spacing between two adjacent blast holes, the radian and length of the arc segment, and the length of the straight segment are determined according to the blasting condition.

[0015] Preferably, in the step S5, every three blast holes successively adjacent to each other are divided into a group to form one detonation unit, the blast hole at the middle position in the detonation unit is detonated first, and the remaining two blast holes in the detonation unit are detonated by using a digital electronic detonator.

[0016] Preferably, in the step S3, if the drilling hole collapse phenomenon is encountered, a blast hole is supplemented at 1m beside the collapsed drilling hole to replace the collapsed drilling hole.

[0017] Preferably, two remedial drilling holes intersecting with each other are arranged at the collapsed drilling hole, so that the intersection of the two remedial drilling holes is located at the collapsed drilling hole, to loosen the rock stratum or soil at the region where the collapsed drilling hole is located.

[0018] The application further provides a blasting pressure relief method for a high-position roof of a large-span longwall working face, comprising the following steps.

[0019] In step S1, a blasting condition is determined according to field exploration data, wherein the blasting condition comprises a position of a high-position roof needing to be blasted for pressure relief, a thickness of the high-position roof, a lithology of the high-position roof, a lithology of a rock stratum between the high-position roof and a coal seam, and a span of the large-span longwall working face.

[0020] In step S2, a plurality of blast holes are designed according to the blasting condition, wherein the blast holes are parallel and spaced apart along a mining direction of the large-span longwall working face, each of the blast holes comprises an arc segment and a straight segment located in the high-position roof, one end of the arc segment penetrates into the high-position roof and communicates with one end of the straight segment, a length of each of the blast holes along a length direction of the large-span longwall working face is greater than a length of the large-span longwall working face, all of the blast holes are divided into first blast holes and second blast holes, the other end of the arc segment in each of the first blast holes is located at a top of an air intake roadway, the other end of the arc segment in each of the second blast holes is located at a top of an air return roadway, and the first blast holes and the second blast holes are staggered.

[0021] In step S3, a kilometer directional drilling machine is used to perform drilling construction on all of the blast holes.

[0022] In step S4, all of the blast holes are charged and blocked.

[0023] In step S5, all of the blast holes are detonated.

[0024] Preferably, an axis of each of the blast holes is located in a vertical plane parallel to the large-span longwall working face, a spacing between two adjacent blast holes, an arc degree and a length of the arc segment, and a length of the straight segment are determined according to the blasting condition.

[0025] Preferably, in step S5, every five blast holes that are sequentially adjacent are divided into a group to form a detonation unit, a blast hole at a middle position of the detonation unit is detonated first, the remaining blast holes in the detonation unit are detonated by using a digital electronic detonator with a millisecond delay, and the blast holes farther away from the middle position in the detonation unit are detonated later.

[0026] Preferably, in step S3, if a drilling hole collapse phenomenon occurs, a blast hole is additionally drilled at a position 1 m away from the collapsed drilling hole to replace the collapsed drilling hole.

[0027] Preferably, two remedial drilling holes that intersect with each other are arranged at the collapsed drilling hole, so that a crossing position of the two remedial drilling holes is located at the collapsed drilling hole, to loosen a rock stratum or soil at a region where the collapsed drilling hole is located.

[0028] The present application has the following technical effects relative to the prior art:

[0029] The blasting pressure relief method for the high-position roof of the large-span longwall working face covers the longwall working face with the blast hole, and can realize the whole-layer pre-splitting blasting of the high-position thick and hard roof. The present application uses the kilometer directional drilling machine to perform the drilling construction of the blast hole from the air inlet lane and / or the air return lane, which is convenient for construction, and compared with the existing high-position lane blasting technology, can not only shorten the construction period, but also greatly reduce the construction cost.

[0030] Further, the present application applies the digital electronic detonator to the blasting pressure relief project, controls the different detonation delay times of different blast holes in the same group of initiation units, provides a new free surface for the post-blast hole by the pre-blast hole, and achieves the purpose of optimizing the broken area.

[0031] Further, for the collapsed drill hole, two mutually intersecting remedial drill holes are arranged to loosen and crush the rock or soil in the area where the collapsed drill hole is located, and provide a new free surface for the blasting of the blast holes on both sides, so as to weaken the integrity of the roof, well cope with the collapsed hole problem caused by geological conditions and the like, and the collapsed drill hole and the remedial drill hole also weaken the thick and hard roof at the high position. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description only constitute some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0033] Figure 1 is a schematic view of the position of the high-position roof;

[0034] Figure 2 is a schematic view of the blast hole arrangement in the first embodiment of the present application;

[0035] Figure 3 is a schematic view of the setting of the remedial drill hole for the collapsed drill hole in the first embodiment of the present application Figure 1 ;

[0036] Figure 4 is a schematic view of the setting of the remedial drill hole for the collapsed drill hole in the first embodiment of the present application Figure 2 ;

[0037] Figure 5 is a schematic view of the blast hole arrangement in the second embodiment of the present application;

[0038] In the figure: 1. Coal seam; 2. Rock layer; 3. High-level roof; 4. Blast hole; 41. Straight segment; 42. Arc segment; 5. Air intake lane; 6. Return air lane; 7. Large-span longwall working face; 8. Drilling hole for collapsed hole; 9. Remedial drilling hole; 10. First blast hole; 11. Second blast hole. DETAILED DESCRIPTION

[0039] 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.

[0040] The purpose of the present invention is to provide a blasting pressure relief method for the high-level roof of a large-span longwall working face, so as to solve the problems existing in the above-mentioned prior art and improve the pressure relief effect of the high-level roof of the large-span longwall working face.

[0041] 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.

[0042] Example 1

[0043] like Figures 1 to 4 As shown, this embodiment provides a method for blasting and depressurizing the high-level roof of a large-span longwall working face, comprising the following steps:

[0044] Step S1: Determine blasting conditions based on on-site exploration data, including the location of the high-level roof 3 requiring blasting pressure relief, the thickness of the high-level roof 3, the lithology of the high-level roof 3, the lithology of the rock layer 2 between the high-level roof 3 and the coal seam 1, and the span of the longwall working face 7;

[0045] Step S2, designing a plurality of blastholes 4 distributed in parallel and at intervals along the mining direction of the large-span longwall working face 7 according to the blasting working conditions, each blasthole 4 includes an arc segment 42 and a straight segment 41 all located in the high-level roof 3, one end of the arc segment 42 penetrates the high-level roof 3 and is connected to one end of the straight segment 41, and the other ends of all the arc segments 42 are located at the top of the air inlet tunnel 5 or at the top of the return air tunnel 6; the length of each blasthole 4 along the length direction of the large-span longwall working face 7 is greater than the length of the large-span longwall working face 7, that is, each blasthole 4 covers the large-span longwall working face 7 along the length direction of the large-span longwall working face 7, thereby facilitating the complete blasting pressure relief of the high-level thick hard roof above the entire large-span longwall working face 7, thereby improving the pressure relief effect;

[0046] Step S3, drilling construction is performed on all the blast holes 4 by using a kilometer directional drilling machine, which is a commercially available product known to the skilled person; the kilometer directional drilling machine can realize accurate drilling positioning, and can accurately arrange the blast holes 4 at the predetermined positions according to the design requirements, which helps to improve the blasting effect, makes the broken degree of the rock after blasting more uniform, reduces the overbreak and underbreak phenomenon, and thus improves the engineering quality;

[0047] Step S4, charging and plugging are performed on all the blast holes 4; all the blast holes 4 adopt the normal charge positive initiation mode;

[0048] Step S5, initiation is performed on all the blast holes 4; the shock waves generated by the explosion of all the blast holes 4 make the rock stratum 2 and the high-level roof 3 above the coal seam 1 break and produce fissures, and finally form a loose zone around the blast holes 4, and the loose zones of the blast holes 4 are connected to form a weak zone (pressure relief zone), which provides a release compensation space for stress.

[0049] Since all the blast holes 4 in the embodiment are parallel and spaced apart along the mining direction of the large-span longwall working face 7, the blasting range of the blast holes 4 can theoretically cover the position of the large-span longwall working face 7 during the entire mining process, thereby providing prevention of rock burst disasters during the entire mining process. The large-span longwall working face 7 in the embodiment refers to a large-span longwall working face 7 with a span greater than 200 m, and the high-level roof 3 refers to a thick and hard roof located above the coal seam 1 and having an interval of 40 m-100 m with the coal seam 1.

[0050] In the alternative of the embodiment, it is more preferred that the axis of each blast hole 4 is located in a vertical plane parallel to the large-span longwall working face 7, which can on the one hand make the explosive uniformly distributed in the rock, and the blasting energy can also be more uniformly transmitted to the rock. This can make the rock break more uniformly, avoid the situation of local overbreak or underbreak, and is conducive to subsequent coal mining and transportation. On the other hand, it can facilitate better control of the blasting direction, so that the rock after blasting collapses towards the working face direction, which is convenient for loading and transportation by the coal mining equipment, and at the same time, it can also reduce the damage of blasting to the surrounding rock behind and on both sides of the working face, and maintain the stability of the surrounding rock; the distance between the adjacent two blast holes 4, the curvature and length of the arc-shaped section 42, and the length of the straight section 41 are determined according to the blasting conditions.

[0051] In the optional scheme of the embodiment, preferably, in step S5, every three sequentially adjacent blast holes 4 are divided into a group to form an initiation unit, the blast hole 4 at the middle position of the initiation unit is initiated first, and the other two blast holes 4 in the initiation unit are initiated by using digital electronic detonators with a millisecond delay. Initiating the middle blast hole 4 first can form an initial broken space in the rock, providing a compensation space for the subsequent blasting of the adjacent blast holes 4. In this way, the rock has a larger moving space for subsequent blasting, and the broken rock size is more uniform, which is beneficial to improve the recovery rate of coal and subsequent transportation, processing and other links; initiating the other two blast holes 4 with a millisecond delay makes the blasting stress waves superimpose and interfere with each other, enhancing the breaking effect on the rock. At the same time, since the rock is subjected to blasting impact at different times, the internal fissures develop more fully, further improving the breaking effect.

[0052] In the optional scheme of the embodiment, preferably, in step S3, if the drilling hole collapse phenomenon is encountered, a blast hole 4 is supplemented 1m beside the collapsed drilling hole 8 to replace the collapsed drilling hole 8. The collapse will destroy the original blast hole 4 layout and affect the uniform distribution of blasting energy. Supplementing a blast hole 4 1m beside the collapsed drilling hole can maximize the integrity of the blast hole 4 layout, so that the blasting energy acts on the rock according to the design requirements, and ensures that the rock breaking effect meets the engineering requirements; the charge amount, initiation time and other parameters of each blast hole 4 are calculated based on the original design of the blast hole 4 position and spacing. The replacement of the collapsed drilling hole with a supplemented blast hole 4 can keep the blasting parameters relatively stable, avoid local blasting energy deficiency or excess caused by the collapse, and thus achieve the expected blasting effect, such as uniform rock breaking size, easy subsequent excavation and transportation, etc.

[0053] In the optional scheme of the embodiment, preferably, two mutually intersecting remedial drilling holes 9 are arranged at the position of the collapsed drilling hole 8, so that the intersection of the two remedial drilling holes 9 is located at the position of the collapsed drilling hole 8, to loosen the rock stratum 2 or soil at the region where the collapsed drilling hole 8 is located; by arranging two mutually intersecting remedial drilling holes 9 for the collapsed drilling hole 8, the rock or soil at the region where the collapsed drilling hole 8 is located can be loosened and broken, and at the same time, a new free surface is provided for the blasting of the blast holes 4 on both sides, achieving the purpose of weakening the integrity of the roof, which can well cope with the collapse problem caused by geological conditions and the like on site, and the collapsed drilling hole 8 and the remedial drilling hole 9 also have a certain weakening effect on the thick and hard roof at high level.

[0054] Embodiment Two

[0055] As shown in Figure 5 The embodiment provides a blasting pressure relief method for a high-level roof of a large-span longwall working face. The steps of the embodiment are basically the same as those of Embodiment One, and the difference is only that:

[0056] In the blasting pressure relief method of the high-level roof of the large-span longwall working face of the embodiment, all the blast holes 4 are divided into first blast holes 10 and second blast holes 11, the other end of the arc-shaped section 42 in each first blast hole 10 is located at the top of the air inlet roadway 5, and the other end of the arc-shaped section 42 in each second blast hole 11 is located at the top of the air return roadway 6; and the first blast holes 10 and the second blast holes 11 are staggered. It is worth noting that in this embodiment, the first blast holes 10 are drilled at the top of the air inlet roadway 5 towards the high-level roof 3, and the second blast holes 11 are also drilled at the top of the air return roadway 6 towards the high-level roof 3. This scheme has higher requirements for lithological conditions, and technicians need to judge whether this scheme can be used according to the blasting conditions. If the lithological differences are obvious and the hole collapse phenomenon is frequent, the blasting pressure relief method of the high-level roof of the large-span longwall working face of the first embodiment should be used. If the lithological conditions are good, the blasting pressure relief method of the high-level roof of the large-span longwall working face of the embodiment can be selected. In the construction process of the embodiment, the drilling of the first blast holes 10 and the second blast holes 11 can be carried out simultaneously in the air inlet roadway 5 and the air return roadway 6, which can effectively shorten the construction period.

[0057] In addition, the detonation step in this embodiment is also different from the detonation step of the first embodiment: in step S5, every five sequentially adjacent blast holes 4 are divided into a group to form a detonation unit, the blast hole 4 at the middle position of the detonation unit is detonated first, and the remaining blast holes 4 in the detonation unit are detonated by a digital electronic detonator with a millisecond delay, and the blast holes 4 farther away from the middle position in the detonation unit are detonated later. The blast hole 4 at the middle position is detonated first to provide an initial crushing space and a compensation space for the surrounding rock, and then the remaining blast holes 4 are sequentially detonated with a millisecond delay, which can make the rock subjected to multiple blasting stress waves in different directions, and the rock crushing is more sufficient and the block size after crushing is more uniform, which is beneficial to subsequent mining and transportation operations; detonating the five blast holes 4 in a detonation unit in sequence disperses the total blasting energy to different time releases, avoiding the strong vibration and impact caused by the concentrated release of energy. This helps to protect the surrounding rock mass, roadway, and nearby buildings and equipment, and reduces the damage and safety hazards caused by blasting vibration; by accurately controlling the millisecond delay time, the vibration waves generated by each blast hole 4 are staggered during propagation, reducing the superposition effect of the vibration waves. Especially for the large-span longwall working face 7, this way can effectively reduce the vibration impact of blasting on the roof and the surrounding coal and rock mass, which is beneficial to maintaining the stability of the roof and preventing roof accidents.

[0058] The principles and implementation manners of the present application are described by using specific examples in the present application, and the above examples are only used for helping to understand the method of the present application and its core idea; meanwhile, for the general technical personnel in the art, according to the idea of the present application, the specific implementation manners and application ranges will be changed. In conclusion, the content of the present specification should not be understood as the limitation of the present application.

Claims

1. A method for blasting and unloading pressure at a high-rise roof of a long-span longwall working face, characterized in that: The following steps are involved: Step S1: Determine blasting conditions based on on-site exploration data, including the location of a high-level roof requiring blasting and pressure relief, the thickness of the high-level roof, the lithology of the high-level roof, the lithology of the rock layer between the high-level roof and the coal seam, and the span of the longwall working face; Step S2: designing a plurality of blastholes spaced parallel to and distributed along the mining direction of the large-span longwall working face according to the blasting working conditions, wherein each blasthole includes an arcuate segment and a straight segment entirely located in the high-level roof, one end of the arcuate segment penetrates the high-level roof and communicates with one end of the straight segment, and the other ends of all the arcuate segments are located at the top of the air intake tunnel or at the top of the return air tunnel; the length of each blasthole along the length direction of the large-span longwall working face is greater than the length of the large-span longwall working face; Step S3: drilling all the blastholes using a kilometer-long directional drilling rig; Step S4, charging and plugging all the blastholes; Step S5: detonate all the blast holes.

2. The method for blasting and depressurizing the high-level roof of a large-span longwall working face according to claim 1, characterized in that: The axis of each blasthole is located in a vertical plane parallel to the large-span longwall working surface; the spacing between two adjacent blastholes, the curvature and length of the arc segment and the length of the straight segment are all determined according to the blasting working conditions.

3. The method for blasting and decompressing the high-level roof of a large-span longwall working face according to claim 1, characterized in that: In step S5, every three adjacent blast holes are divided into a group to form a detonating unit, the blast hole in the middle position of the detonating unit is detonated first, and the remaining two blast holes in the detonating unit are detonated with a micro-difference delay using a digital electronic detonator.

4. The method for blasting and decompressing the high-level roof of a large-span longwall working face according to claim 1, characterized in that: In step S3, if a borehole collapse occurs, a blasthole is drilled 1 m away from the collapsed borehole to replace the collapsed borehole.

5. The method for blasting and decompressing the high-level roof of a large-span longwall working face according to claim 4, characterized in that: Two mutually intersecting remedial boreholes are set at the drill hole of the collapsed hole, so that the intersection of the two remedial boreholes is located at the drill hole of the collapsed hole, so as to loosen the rock layer or soil in the area where the drill hole of the collapsed hole is located.

6. A method for blasting and depressurizing the high-level roof of a large-span longwall working face, characterized in that: The following steps are involved: Step S1: Determine blasting conditions based on on-site exploration data, including the location of a high-level roof requiring blasting and pressure relief, the thickness of the high-level roof, the lithology of the high-level roof, the lithology of the rock layer between the high-level roof and the coal seam, and the span of the longwall working face; Step S2: designing a plurality of blastholes distributed in parallel and at intervals along the mining direction of the large-span longwall working face according to the blasting working conditions, wherein each of the blastholes comprises an arc segment and a straight segment located entirely in the high-level roof, one end of the arc segment penetrates the high-level roof and is connected to one end of the straight segment, and the length of each blasthole along the length direction of the large-span longwall working face is greater than the length of the large-span longwall working face; all the blastholes are divided into a first blasthole and a second blasthole, the other end of the arc segment in each of the first blastholes is located at the top of the air inlet tunnel, and the other end of the arc segment in each of the second blastholes is located at the top of the return air tunnel; and the first blastholes and the second blastholes are staggered in distribution; Step S3: drilling all the blastholes using a kilometer-long directional drilling rig; Step S4, charging and plugging all the blastholes; Step S5: detonate all the blast holes.

7. The method for blasting and depressurizing the high-level roof of a large-span longwall working face according to claim 6, characterized in that: The axis of each blasthole is located in a vertical plane parallel to the large-span longwall working surface; the spacing between two adjacent blastholes, the curvature and length of the arc segment and the length of the straight segment are all determined according to the blasting working conditions.

8. The method for blasting and depressurizing the high-level roof of a large-span longwall working face according to claim 6, characterized in that: In step S5, every five adjacent blast holes are divided into a group to form a detonating unit, the blast hole in the middle position of the detonating unit is detonated first, and the remaining blast holes in the detonating unit are detonated with a micro-difference delay using a digital electronic detonator, and the blast holes in the detonating unit that are farther away from the middle position are detonated later.

9. The method for blasting and decompressing the high-level roof of a large-span longwall working face according to claim 6, characterized in that: In step S3, if a borehole collapse occurs, a blasthole is drilled 1 m away from the collapsed borehole to replace the collapsed borehole.

10. The method for blasting and depressurizing the high-level roof of a large-span longwall working face according to claim 9, characterized in that: Two mutually intersecting remedial boreholes are set at the drill hole of the collapsed hole, so that the intersection of the two remedial boreholes is located at the drill hole of the collapsed hole, so as to loosen the rock layer or soil in the area where the drill hole of the collapsed hole is located.

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