Method of overburden pressure relief in goaf area

Abstract

The present application proposes a method for decompressing overburden in goaf areas, which includes S01, drilling on the roof of a tunnel adjacent to the goaf, and the formed borehole extends obliquely to a second rock layer adjacent to the upper end of the goaf; S02, delivering an elastomeric device to the bottom of the borehole. The method for decompressing overburden in goaf areas uses the formation of local high stress or strain energy around the elastomeric device to effectively cut off or reduce the energy transfer of high-position rock formations, prevent or reduce the transfer of creep potential energy to the production tunnel side, and ensure the stability of the isolation coal pillars in the production working face tunnel and the safety of production.

Description

Technical Field

[0001] The invention belongs to the technical field of coal mining, and in particular relates to a method for relieving pressure of overburden in a goaf area. Background Art

[0002] The goaf is divided into the goaf after the working face is mined and advanced and the goaf adjacent to the production working face. After the coal seam is mined, the rock strata on the roof of the goaf will collapse and deform layer by layer from bottom to top. Usually the first rock layer M1 (direct roof) and the second rock layer M2 (basic roof) collapse, and the third rock layer M3 and above will bend and deform instead of falling. However, due to the influence of geological and rock strata structure reasons, abnormal situations may sometimes occur. The fracture position of the second rock layer M2 is not ideal, and a rock layer plate-body rock beam is formed on the goaf side above the coal pillar in the goaf. This plate-body rock beam is called a transfer rock beam in mine pressure research. For example, Figure 1 shown.

[0003] exist Figure 1 In the figure, the fracture position of the second rock layer M2 (basic top) located on the side of the isolation coal pillar in the adjacent goaf is not ideal, and there is a distance L from the isolation coal pillar of the production working face. When mining at the production working face, the mining effect will directly induce the overlying rock layer adjacent to the goaf to sink again. At this time, the third rock layer M3 and above will generate motion potential energy, which will act on the "transfer rock beam" of the second rock layer and produce the transfer rock beam torque rotation effect, referred to as the transfer rock beam effect. In severe cases, the transfer rock beam effect directly affects the stability of the isolation coal pillar of the production working face tunnel, produces surrounding rock destruction, affects production operations, causes stress concentration, and triggers rock mass disasters such as impact ground pressure or tunnel floor drum.

[0004] In coal mining, when the above serious situation occurs, it will seriously affect normal production. Therefore, it is often necessary to choose the right time or the right location according to the needs, and take various methods to relieve the pressure of the overburden strata in the goaf, aiming to cut off the rock stratum plate-body beam and eliminate the influence of the transmission rock beam effect. Such as the pre-drilling deep hole blasting fracture pressure relief method of the top stratum of the production tunnel, the high-pressure water fracture pressure relief method of the top stratum drilling hole, the artificial cutting top (blasting) pressure relief method, and the top deep hole (blasting) slit pressure relief method, etc.

[0005] At present, there are certain shortcomings in the pressure relief methods adopted for the overlying rock strata in the goaf. For example, the deep hole blasting fracturing pressure relief method requires the use of explosive detonator fuses. First of all, these materials are strictly controlled materials for safety, which are extremely inconvenient to purchase and use. In addition, there are technical difficulties in mastering the technical parameters and effects. The hydraulic fracturing pressure relief method has high water pressure requirements and is often not selected due to large equipment investment. The effect of low water pressure cannot meet the requirements. In short, the pressure relief technical means currently used are artificial high-pressure and strong technologies, which are not easy to operate and implement, and may affect other production links.

[0006] Therefore, it is necessary to design a method for decompression of overburden in goaf areas. Summary of the invention

[0007] In view of some or all of the above technical problems existing in the prior art, the present invention proposes a method for decompression of overburden in goaf. The method for decompression of overburden in goaf forms local high stress or strain energy around the elastic body device, effectively cuts off or reduces the energy transfer of high-position rock formations, prevents or reduces the transmission of creep potential energy to the production tunnel side, and ensures the stability of the isolation coal pillar in the production working face tunnel and the safety of production.

[0008] According to the present invention, a method for decompression of overburden in goaf is provided, comprising the following steps:

[0009] S01, drilling operation is performed on the top plate of the tunnel near the side of the goaf, and the drilled hole formed extends obliquely to the second rock layer above the upper end of the goaf,

[0010] S02, sending the elastic device to the bottom of the borehole.

[0011] In one embodiment, the drilling operation is performed, and in step S02, after each drilling is completed, the elastomeric device is sent to the bottom of the corresponding drilling hole.

[0012] In one embodiment, in step S01, the starting point of the drilling is 0.2-0.5 meters away from the coal pillar, and the interval between adjacent starting points of the drilling is 1-3 meters.

[0013] In one embodiment, in step S01, the formed drilling hole has an oblique inclination angle of 30-85 degrees.

[0014] Or / and, the formed borehole passes through the second rock layer by 0.1-0.2 meters.

[0015] In one embodiment, before step S01, it is necessary to mark the drilling positions according to the design requirements, and before drilling, drill holes are made at the starting points of each drilling hole.

[0016] In one embodiment, in step S02, the elastomeric device includes a first cylinder, a second cylinder and a pushing body which are sequentially connected in the axial direction, wherein the anti-extrusion capacity of at least the upper section of the first cylinder is smaller than the anti-extrusion capacity of the second cylinder.

[0017] In one embodiment, the first column is cylindrical, and an axially extending notch is provided on the outer wall of the upper end; the second column is cylindrical, and the outer wall of the upper end is wrapped and sleeved on the outer wall of the first column; the pushing body is constructed to be sealed at the lower end of the second column.

[0018] In one embodiment, the first column and the second column are both made of PVC material.

[0019] In one embodiment, a hoop is provided on the outer wall of the lower end of the second column, and a plurality of circumferentially spaced steel wire fins are provided on the hoop, wherein the lower end of each of the steel wire fins expands radially outward relative to the upper end.

[0020] In one embodiment, in the step S02, the elastic body device is delivered into the drill hole through a drill rod, and a concave-convex matching circumferential clamping structure is provided on the contact surface between the drill rod and the pushing body.

[0021] Compared with the prior art, the advantages of the present invention are: on one side of the coal pillar of the production tunnel, a hole is drilled obliquely from the roof to a rock layer position at a predetermined position above the coal pillar adjacent to the goaf, and after drilling to the predetermined position in the rock layer, the elastic device is delivered to the bottom of the hole, and the elastic device installed in the drill hole is located exactly in the predetermined rock layer above the goaf. Therefore, when the overlying rock layer of the goaf sinks and moves, the elastic device will be squeezed by the overlying rock layer. Under the squeezing effect of the moving rock layer, a small local high stress concentration and elevation area or strain energy concentration and elevation area will be generated between the elastic device at the bottom of the hole and the surrounding rock mass. This artificially created local high stress concentration area is called an "artificial stress concentration area". Due to the mining effect of the mining field, the overlying rock layer of the goaf moves continuously, and the "artificial stress concentration area" in the rock layer will further exert force by the force of the overlying rock layer movement, causing the rock layer that acts as a rock beam to produce deformation displacement or complex crack and fissure development changes. This development trend of the rock formation using force will make the energy of the "artificial stress concentration area" continue to exert force and accelerate the development of cracks and fissures in the rock formation around the "artificial stress concentration area" until the fracture completely eliminates the transmission rock beam effect. The result of this leveraging force mode is that the rock formation at the appropriate position above the coal pillar will produce cracks and fissures in the rock formation as expected until the fracture collapses. This change process of the overburden layer from developing cracks to fracture collapse is very helpful in weakening or eliminating the unbalanced compressive stress and destructive effect of the overburden movement potential energy in the goaf on the coal pillar with the help of the rock formation (rock plate-body transmission rock beam). At this point, the elastomer device has completed the prevention or reduction of the transmission of creep potential energy to the production tunnel side. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0023] Figure 1 A schematic diagram of the overburden in the goaf is shown;

[0024] Figure 2 The drill holes in the overburden of the goaf are shown, along with the elastomeric device;

[0025] Figure 3 The layout of the boreholes in the tunnel roof for decompression of the overburden in the goaf is shown;

[0026] Figure 4 An elastomeric device is shown.

[0027] In the drawings, the same reference numerals are used for the same components. The drawings are not drawn to scale. DETAILED DESCRIPTION

[0028] In order to make the technical solutions and advantages of the present invention more clearly understood, the exemplary embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than an exhaustive list of all the embodiments. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0029] The present application relates to a method for decompression of overburden in goaf. In the method for decompression of overburden in goaf, Figure 2 As shown, first, step S01 is performed to perform a drilling operation on the roof of the tunnel adjacent to the side of the goaf. The formed borehole extends obliquely to the second rock layer M2 adjacent to the upper end of the goaf. Then, step S02 is performed to send the elastomer device 10 to the bottom of the borehole so that the elastomer device 10 installed in the borehole is located exactly in the predetermined rock layer above the goaf. When the overlying rock layer of the goaf sinks and moves, the elastomer device 10 will be squeezed by the overlying rock layer. Under the squeezing effect of the moving rock layer, a small local high stress concentration increase area or strain energy concentration increase area will be generated between the elastomer device 10 at the bottom of the hole and the surrounding rock mass. This artificially created local high stress concentration area is called an "artificial stress concentration area." Due to the mining effect of the mining area, the overburden strata in the goaf area continue to move, and the "artificial stress concentration area" in the rock strata will further exert force by taking advantage of the movement of the overburden strata, causing the rock strata that acts as the transmission rock beam to deform or develop complex cracks and fissures. This development trend of the rock strata leveraging force will make the energy of the "artificial stress concentration area" continue to exert force and accelerate the development of cracks and fissures in the rock strata around the "artificial stress concentration area" until the fracture completely eliminates the transmission rock beam effect. The result of this leveraging force mode is that the rock strata at the appropriate position above the coal pillar will produce rock strata cracks and fissures as expected until the fracture collapses. This change process of the overburden strata from crack development to fracture collapse is very helpful to weaken or eliminate the unbalanced compressive stress and destructive effect of the overburden strata movement potential energy in the goaf area on the coal pillar by taking advantage of the rock strata (rock stratum plate-body transmission rock beam). At this point, the elastic device 10 has completed the task of preventing or reducing the creep potential energy from being transferred to the production tunnel side, thereby ensuring the stability of the coal pillars isolating the production working face tunnel and the safety of production.

[0030] Specifically, in step S01, on the roof in the tunnel near the side of the goaf, drilling begins according to the first drilling starting point set in advance. From the drilling starting point of the roof, that is, the initial drilling position of the drilling to the end position of the drilling, a right triangle can be formed on the roof horizontal line. Since the height of the second rock layer M2 can be known through geological exploration data. In order to ensure that the drilling passes through the upper boundary of M2 and at the same time make the workload burden not too much, a right-angled side b of the right triangle is 10-20 cm larger than the height of M2 (that is, a right-angled side b of the triangle passes through the upper boundary of M2 and then extends 10-20 cm), for example 15 cm. The length of the side length of the drilling of the right triangle changes with the inclination angle β. According to the present application, the inclination angle β can be 30-85 degrees. Of course, in the process of setting the inclination angle β, the convenience of the drilling operator and the applicable conditions of the drilling tool can be considered, and the size of the inclination angle β can be reasonably selected. The final hole position of the borehole is the bottom of the borehole. According to the pressure relief principle, the designed final hole position of the borehole should pass through the upper interface of the pressure-relieved rock layer M2, so as to ensure good pressure relief capacity.

[0031] In step S01, the drilling operation starts from the end close to the working face and performs multiple drilling operations at intervals along the direction of the tunnel. In step S02, after each drilling is completed, the elastic device is sent to the bottom of the corresponding drilling hole. Figure 3 The diagram shows the distribution of the starting points of the drilling holes on the roof. For example, in order to reserve space for drilling operations, each drilling hole is 200-500 mm away from the coal pillar. Figure 2 and 3 The mark is 300 mm. The adjacent drilling starting points are spaced 1-3 meters apart, for example, 1.5 meters. The above setting helps to ensure the smooth drilling of oblique holes during the drilling process, and ensures accurate drilling, thereby ensuring an ideal pressure relief effect.

[0032] Before drilling holes on the roof of the tunnel, the drilling positions required by the design should be marked with lines: the distance between the opening (starting) hole drilling position and the coal pillar and the spacing between the holes. When drilling holes, a drill nest should be made first, and it is easy to grasp the direction of the drilling hole by using the drill nest. After the hole is completed, the drill slag should be cleaned first, and then the elastomer device 10 is sent to the bottom of the hole at a predetermined height position of the second rock layer M2 using a drill rod. During the drilling process, conventional drilling tools can be used for drilling to reduce production costs. For example, a Φ75 mm drill bit can be used for drilling. Of course, according to different needs, a Φ50 mm drill bit or a Φ100 mm drill bit can also be used.

[0033] In the method of decompression of overburden in goaf area, construction can be carried out before production of the mining face, or after mining of the working face begins.

[0034] Figure 4 An elastomeric device 10 is shown. Figure 4 As shown, the elastic body device 10 comprises a first column 1, a second column 2 and a pushing body 3 which are sequentially connected in the axial direction. Among them, the anti-extrusion capacity of at least the upper section of the first column 1 is smaller than the anti-extrusion capacity of the second column 2.

[0035] The first cylinder 1 is cylindrical, and an axially extending notch 11 is provided on the outer wall of the upper end. After the elastic body device 10 is inserted into the borehole, its upper end is closer to the bottom of the borehole. Preferably, a plurality of, for example, four notches 11 are provided on the circumference of the first cylinder 1, and the notches 11 are evenly distributed. In the axial direction, the length of the notch 11 is about half of the length of the first cylinder 1. The notch 11 is provided so that the upper and lower ends of the first cylinder 1 have different anti-extrusion deformation capabilities. The second cylinder 2 is cylindrical, and the outer wall of the upper end is wrapped and sleeved on the outer wall of the first cylinder 1. For example, if the axial length of the first cylinder 1 is 310 mm, the length of the notch 11 is 150 mm, the plug-in length with the second cylinder 2 is 60 mm, and the distance from the bottom of the notch 11 to the upper end face of the second cylinder 2 is 100 mm. The axial length of the second cylinder 2 is 360 mm. The above structure is simple, especially the anti-extrusion deformation ability of the plug-in part of the first column 1 and the second column 2 is increased, resulting in different anti-extrusion strain abilities of different sections of the elastic device 10. For example, the first column 1 and the second column 2 can be interference fit. After the elastic device 10 is placed in the borehole, the elastic device 10 spans the upper interface of the second rock layer M2, that is, the two ends of the elastic device 10 are respectively located in the second rock layer M2 and the third rock layer M3.

[0036] Preferably, the wall thickness of the first cylinder 1 is greater than or equal to 1 mm, and is constructed as a PVC cylinder. The upper end of the cylinder of the first cylinder 1 is divided into four equal parts in a "cross" shape by an electric saw or other mechanical processing means. The second cylinder 2 is a PVC cylinder with a wall thickness greater than or equal to 1 mm. The outer wall of the second cylinder 2 is substantially the same as the size of the drill bit. For example, when drilling with a Φ75 mm drill bit, the outer wall size of the second cylinder 2 is also 75 mm.

[0037] The push body 3 is configured to be fixedly blocked at the lower end of the second column 2. When the elastomeric device 10 is sent into the borehole, the push body 3 is abutted against the drill rod to send the elastomeric device 10 into the borehole. In addition, a concave-convex matching circumferential clamping structure is provided on the contact surface between the drill rod and the push body 3 for abutment between the two, thereby facilitating a better delivery operation. For example, a "cross"-shaped groove 31 is provided on the lower end surface of the push body 3. At the same time, a "cross"-shaped bar is protrudingly provided on the end surface of the drill rod that contacts the push body 3, for matching insertion into the groove 31.

[0038] A hoop 4 is provided on the outer wall of the lower end of the second column 2. A plurality of circumferentially spaced steel wire feet 5 are provided on the hoop 4. The lower end of each steel wire foot 5 is radially expanded relative to the upper end. In other words, the steel wire foot 5 is similar to an umbrella-shaped structure. When the elastomeric device 10 is fed into the borehole, the steel wire feet 5 of the above structure are tightened inwardly by the drilling pressure, and do not affect the movement of the elastomeric device 10 toward the bottom end in the borehole. However, when the elastomeric device 10 is fed into place, the steel wire feet 5 can abut against the wall of the borehole, thereby preventing the elastomeric device 10 from retreating, thereby ensuring the position of the elastomeric device 10 in the borehole.

[0039] The pressure relief technology proposed in this application does not require strong human interference. The outstanding advantage is that it uses the force of the rock formation's own movement to generate the force of the elastic device to achieve a one-two-one ...

[0040] First, the height of the rock stratum to be unloaded should be determined by analyzing the occurrence state of the overlying rock stratum in the goaf and the characteristics of the subsidence movement. Then, an inclined borehole should be drilled from the top of the tunnel to the rock stratum to be unloaded in accordance with the predetermined direction and orientation. Then, the elastic device is pushed to the bottom of the borehole by the drill rod to complete the installation work. According to the pre-designed and calculated drilling parameters, the drilling and installation process is very simple and convenient. Compared with other unloading methods, it saves time, labor, and labor, and the construction is fast, which completely solves the difficult and troublesome problem of unloading technology for overlying rock strata in goafs. The design principle and concept of the elastic device are novel, scientific and objective, the required processing materials and parts are easy to purchase, and the processing process is easy to control and realize. The construction process of the overlying rock unloading method in the goaf is independent and does not interfere with other production links. The unloading technology and principle are feasible and are particularly suitable for unloading soft rock strata on the roof. The engineering cost is low and the construction operation is simple and easy to master. When unloading the overlying rock stratum adjacent to the goaf, the operation is separated by coal pillars, which is highly safe.

[0041] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic creative concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and / or modifications that fall within the scope of the present invention, and changes and / or modifications made according to the embodiments of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for relieving pressure on overburden in goaf area, characterized in that: The steps include: S01, drilling operation is performed on the top plate of the tunnel near the side of the goaf, and the drilled hole formed extends obliquely to the second rock layer above the upper end of the goaf, In step S01, the formed borehole has an oblique inclination angle of 30-85 degrees, or / and the formed borehole passes over the second rock layer by 0.1-0.2 meters, S02, sending the elastomeric device to the bottom of the drill hole. In the step S02, the elastomeric device includes a first column, a second column and a pushing body which are sequentially connected in the axial direction, wherein the anti-extrusion capacity of at least the upper section of the first column is smaller than the anti-extrusion capacity of the second column, a hoop is provided on the outer wall of the lower end of the second column, and a plurality of circumferentially spaced steel wire wing feet are provided on the hoop, and the lower end of each of the steel wire wing feet is radially expanded relative to the upper end.

2. The method for decompression of overburden in goaf according to claim 1, characterized in that: In step S01, the drilling operation is performed multiple times at intervals along the direction of the tunnel starting from the end close to the working face, and in step S02, after each drilling is completed, the elastic device is sent to the bottom of the corresponding drilling hole.

3. The method for relieving pressure of overburden in goaf area according to claim 2, characterized in that: In step S01, the distance between the starting point of the drilling hole and the coal pillar is 0.2-0.5 meters, and the interval between adjacent starting points of the drilling holes is 1-3 meters.

4. The method for decompression of overburden in goaf according to claim 1, characterized in that: Before step S01, it is necessary to mark the drilling positions according to the design requirements, and before drilling, drill holes are made at the starting points of each drilling hole.

5. The method for decompression of overburden in goaf according to claim 1, characterized in that: The first column is cylindrical, and an axially extending notch is arranged on the outer wall of the upper end; the second column is cylindrical, and the outer wall of the upper end is wrapped and sleeved on the outer wall of the first column; the pushing body is constructed to be sealed at the lower end of the second column.

6. The method for decompression of overburden in goaf according to claim 1, characterized in that: The first column and the second column are both made of PVC material.

7. The method for relieving pressure on overburden in goaf according to any one of claims 1 to 6, characterized in that: In the step S02, the elastic body device is delivered into the drill hole through a drill rod, and a concave-convex matching circumferential clamping structure is provided on the contact surface between the drill rod and the pushing body.

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