Rock burst prevention and control arrangement method for rock burst mine island working face

Abstract

The invention discloses a rock burst prevention and control arrangement method for a rock burst mine island working face. An air return gate way and a haulage gate way are constructed in goaf areas on the two adjacent sides of the island working face in a negative coal pillar mode; a plurality of pressure relief chambers are constructed in the two gate ways respectively and used for pre-pressure relief of the working face; the distance between every two adjacent pressure relief chambers is determined according to the large-diameter drill hole pressure relief influence radius and the blasting pressure relief influence radius, so that it is guaranteed that a pressure relief area covers the whole island working face; a large-diameter drill hole and a blasting drill hole are constructed in each pressure relief chamber, it is ensured that cracks generated by large-diameter drill hole construction are communicated with one another to form a weakening zone, and a continuous broken layer is formed after blasting of the blasting drill hole; and finally, the pressure relief work is completed after evaluation. By means of the pressure relief process, pressure relief and scour prevention treatment can be conducted on the island working face and the roadways on the two sides of the island working face, the rock burst risk of the working face and the roadways on the two sides is effectively reduced, and therefore a safe environment is provided for recovering rock burst mine strip remaining coal pillars.

Description

Technical Field

[0001] The invention belongs to the technical field of coal mine production safety, and in particular relates to a method for arranging an isolated island working face in a rock burst mine to prevent and control rock burst. Background Art

[0002] Rock burst is a special form of mine pressure. With the increasing depth of coal mining in recent years, the harm of rock burst has become increasingly serious. In addition, deep isolated working faces will be formed during the mining process of rock burst mines. Isolated working faces refer to the working faces adjacent to the working face to be mined that have been completely mined out. Since the isolated working face is affected by the mining of the goaf and the working face, the overburden strata are more active and the surrounding rock is more severely damaged than the ordinary working face, which poses a serious challenge to the safe and efficient mining of the working face. In order to reduce the rock burst of the working face, the negative coal pillar layout is currently adopted for the isolated working face, that is, the return air level and the transport level are arranged in the mined working faces on both sides of the adjacent sides, and a part of the goaf is used as a reserved coal pillar. This negative coal pillar method is used to achieve the pressure relief effect of the two tunnels. Although this layout solves the problem of tunnel pressure relief to a certain extent, since the return air tunnel and the transport tunnel are in the goaf, it is impossible to directly relieve the pressure on the isolated working face from the two sides and the top of the tunnel, which leads to the continuous increase in the risk of impact ground pressure on the isolated working face during the mining process. If not promptly prevented and controlled, the stress distribution of the isolated working face will still lead to mining disasters such as tunnel bottom bulging, roof subsidence, equipment damage and support system paralysis in the later stage. In order to maintain the safety and stability of the mine production system, it is necessary to further carry out anti-impact arrangements for the isolated working face.

[0003] Based on the above problems, how to provide a new method to achieve pressure relief and anti-impact treatment for the above-mentioned isolated working face and the tunnels on both sides, effectively reduce the risk of rock burst in the working face and the tunnels on both sides, and thus provide a safe environment for recovering the coal pillars left in the rock burst mine strips, is the research direction required by the present invention. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the present invention provides a method for arranging an isolated working face to prevent and control rock burst in a rock burst mine, which can achieve pressure relief and anti-impact treatment for the above-mentioned isolated working face and the tunnels on both sides of the face, effectively reducing the risk of rock burst in the working face and the tunnels on both sides, thereby providing a safe environment for recovering the coal pillars left in the rock burst mine strip.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a method for preventing and controlling rock burst in an isolated island working face of a rock burst mine, the specific steps of which are:

[0006] Step 1: excavate the return air tunnel and the transport tunnel from the goafs on both sides of the isolated working face, and leave a certain distance of goaf between each tunnel and the isolated working face as a negative coal pillar;

[0007] Step 2: Preset multiple pressure relief chamber construction points in the return air lane and the transport lane respectively. The pressure relief chamber construction points in each lane are equally spaced along their respective directions. Then, determine the influence radius R1 of large-diameter drilling pressure relief and the influence radius R2 of blasting pressure relief, and then determine the spacing L between adjacent pressure relief chambers in each lane. The length of L satisfies L≥2R3, and R3 is the larger value between R1 and R2, so as to ensure that the pressure relief area covers the entire island working surface and has the required pressure relief effect.

[0008] Step 3: Determine the construction point of the pressure relief chamber and the distance L between adjacent pressure relief chambers according to step 2, and excavate multiple pressure relief chambers from the return air level and the transport level through the negative coal pillar area to the two sides of the coal wall of the isolated island working face. The pressure relief chambers are used to pre-depressurize the isolated island working face and provide space for workers to construct pressure relief drilling holes;

[0009] Step 4: In each pressure relief chamber, large-diameter drilling and blasting drilling are constructed toward the isolated island working face. According to the principle of unloading rock burst, the parameters of large-diameter drilling and blasting drilling are determined to ensure that the cracks generated by the large-diameter drilling construction are interconnected to form a weakened zone, and a continuous broken layer is formed after blasting of the blasting drilling;

[0010] Step 5. After the construction is completed, a monitoring method is used to evaluate the pre-pressure relief effect of the isolated working face after the current construction pressure relief. If the pressure relief requirements are met, the pressure relief construction of the isolated working face is completed; if not, it is necessary to increase the construction density of large-diameter drilling and blasting drilling in each pressure relief chamber until the pre-pressure relief effect of the isolated working face meets the pressure relief requirements and the pressure relief work is completed.

[0011] Furthermore, when setting up the negative coal pillar in step one, it is necessary to set up the negative coal pillar at the low stress position of the goaf according to the stress condition of the isolated island working face, determine the reasonable size of the negative coal pillar, and determine the setting distance L1 of the negative coal pillar; the reason is: in practice, the coal pillar is simultaneously subjected to the coupling effect of static load and dynamic load. Static load provides the basic stress background for the coal pillar, and the dynamic load is superimposed on it to make the stress state of the coal pillar more complicated. The plastic deformation and damage of the coal pillar under the action of static load will reduce the ability of the coal pillar to resist dynamic load, and the impact of dynamic load will further expand the plastic zone and damage range of the coal pillar, resulting in faster instability and failure of the coal pillar. Therefore, it is selected to set up the negative coal pillar at the low stress position.

[0012] Furthermore, the influence radius R1 of the large diameter drilling pressure relief in step 2 is specifically expressed as follows:

[0013]

[0014] Where: S is the loose coefficient of the hole wall of the island working face and the two sides of the tunnel; K is the drilling cuttings coefficient, and Q1 is the amount of drill cuttings when drilling a large-diameter hole at a high-stress position on the island working face, and Q2 is the amount of drill cuttings when drilling a large-diameter hole at a normal-stress position on the island working face;

[0015] The blasting pressure relief influence radius R2, the specific formula is:

[0016]

[0017] where σ cd and σ ld is the uniaxial dynamic compressive strength and uniaxial dynamic tensile strength of the rock mass, MPa; ρ0 is the density of the explosive, Kg / m3; D c is the blasting speed of explosives, m / s; K is the radial uncoupled charge coefficient; l c is the axial charge coefficient; n is the pressure increase coefficient when the explosive explosion product expands and collides with the borehole wall; η is the expansion adiabatic index of the detonation product; r b is the blasting hole radius, mm; B = [(1 + b) 2 +(1+b 2 )-2μ d (1-μ d )(1-b) 2 ] 1 / 2 , b=μ d / 1-μ d , μ d is the dynamic Poisson's ratio of the rock mass, μ is the static Poisson's ratio of the rock mass; α and β are the load propagation attenuation indexes, α=2+μ d / 1-μ d , β=2-μ d / 1-μ d .

[0018] Furthermore, the construction of the pressure relief chamber in step three adopts a step working surface construction method or a pilot tunnel construction method. These two methods are adopted because they cause less disturbance to the surrounding rock during the construction process and the construction methods are relatively mature.

[0019] Furthermore, in step 4, the parameters of large diameter drilling and blasting drilling are determined as follows:

[0020] The depth S1 of the large-diameter borehole is determined according to the drilling position of the borehole. When drilling on an isolated island working face, the depth of the borehole is 1 to 3 times the mining height; when drilling on both sides of the tunnel, the depth of the borehole is 3 to 4 times the mining height. The actual length is determined based on the actual drilling construction length on site combined with the pressure relief effect of practical feedback; the specific calculation formula for the construction aperture D1 of the large-diameter borehole is as follows:

[0021] D1=ωl(3)

[0022] Where: l is the height of the strip coal pillar in the mine, m; strip coal pillar refers to the coal pillar left behind by strip mining; ω is the proportional coefficient, ranging from 0.05 to 0.10;

[0023] The diameter D2 of the blasting drill hole is 60mm~100mm, and is comprehensively selected according to the width of the isolated island working surface, the thickness and hardness of the rock layer; the specific calculation formula of the blasting drill hole depth S2 is as follows:

[0024]

[0025] Where: H is the vertical distance from the key induced coal layer to the strip residual coal pillar; θ is the rock formation pressure relief angle, which is related to the properties of the rock formation.

[0026] Furthermore, in step five, at least two methods, namely the drill cuttings method and the stress online monitoring method, are used to respectively evaluate the pre-pressure relief effect of the isolated island working face after the current construction pressure relief. If both evaluation methods meet the pressure relief requirements, it is determined that the pressure relief requirements are met; otherwise, it is determined that the pressure relief requirements are not met.

[0027] Compared with the prior art, the present invention first excavates the return air tunnel and the transport tunnel in the goaf on both sides of the isolated working face, and leaves the goaf as the negative coal pillar; and constructs a plurality of pressure relief chambers in the return air tunnel and the transport tunnel, respectively, the pressure relief chambers are used for pre-pressure relief of the isolated working face, and provide workers with space for constructing pressure relief drilling holes; the spacing between adjacent pressure relief chambers is determined according to the influence radius of large-diameter drilling pressure relief and the influence radius of blasting pressure relief, so as to ensure that the pressure relief area covers the entire isolated working face and has the required pressure relief effect; in each pressure relief chamber, large-diameter drilling holes and blasting drilling holes are constructed toward the isolated working face, and the parameters of large-diameter drilling holes and blasting drilling holes are determined according to the principle of unloading impact ground pressure, so as to ensure that the cracks generated by the large-diameter drilling construction are interconnected to form a weakened zone, and the blasting drilling holes form a continuous broken layer after blasting; finally, a monitoring method is used to evaluate the pre-pressure relief effect of the isolated working face after the current construction pressure relief, and finally the pressure relief work is completed. Through the above-mentioned pressure relief process, the isolated working face and the tunnels on both sides can be treated with pressure relief and anti-impact treatment, effectively reducing the risk of rock burst in the working face and the tunnels on both sides, thereby providing a safe environment for recovering the coal pillars left in the rock burst mine strips. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the construction layout of the present invention;

[0029] Figure 2 yes Figure 1 Cross-section view along the AA direction.

[0030] In the figure: 1. Return air tunnel; 2. Transport tunnel; 3. Goaf; 4. Large diameter borehole; 5. Pressure relief chamber; 6. Blasting borehole; 7. Fine-grained sandstone; 8. Mudstone; 9. Medium-grained sandstone; 10. Isolated working face. DETAILED DESCRIPTION

[0031] The present invention will be further described below.

[0032] like Figure 1 and 2 As shown, the specific steps of the present invention are:

[0033] Step 1: excavate the return air tunnel 1 and the transport tunnel 2 from the goaf 3 on both sides of the isolated working face 10, and leave a certain distance of goaf 3 between each tunnel and the isolated working face 10 as a negative coal pillar; when leaving the negative coal pillar, it is necessary to leave a negative coal pillar at the low stress of the goaf 3 according to the stress state of the isolated working face 10, determine the reasonable size of the negative coal pillar and determine the distance L1 of the negative coal pillar; the reason is: in practice, the coal pillar is simultaneously subjected to the coupling of static load and dynamic load. Static load provides the basic stress background for the coal pillar, and the dynamic load is superimposed on it to make the stress state of the coal pillar more complicated. The plastic deformation and damage of the coal pillar under the static load will reduce the coal pillar's ability to resist dynamic load, and the impact of dynamic load will further expand the plastic zone and damage range of the coal pillar, resulting in faster instability and failure of the coal pillar. Therefore, the negative coal pillar is left at the low stress.

[0034] Step 2: Preset multiple pressure relief chamber 5 construction points in the return air tunnel 1 and the transport tunnel 2 respectively. The pressure relief chamber 5 construction points in each tunnel are equally spaced along their respective directions. Then, determine the influence radius R1 of the pressure relief of the large-diameter borehole 4 and the influence radius R2 of the blasting pressure relief, and then determine the spacing L between adjacent pressure relief chambers 5 in each tunnel. The length of L satisfies L≥2R3, and R3 is the larger value between R1 and R2, so as to ensure that the pressure relief area covers the entire island working surface and has the required pressure relief effect; the influence radius R1 of the pressure relief of the large-diameter borehole 4 is specifically formulated as follows:

[0035]

[0036] Where: S is the loose coefficient of the hole wall of the isolated working face 10 and the two sides of the tunnel; K is the drilling cuttings coefficient, and Q1 is the amount of drill cuttings when drilling a large diameter borehole 4 at a high stress position of the isolated working surface 10, and Q2 is the amount of drill cuttings when drilling a large diameter borehole 4 at a normal stress position of the isolated working surface 10;

[0037] The blasting pressure relief influence radius R2, the specific formula is:

[0038]

[0039] where σcd and σ ld is the uniaxial dynamic compressive strength and uniaxial dynamic tensile strength of the rock mass, MPa; ρ0 is the density of the explosive, Kg / m3; D c is the blasting speed of explosives, m / s; K is the radial uncoupled charge coefficient; l c is the axial charge coefficient; n is the pressure increase coefficient when the explosive explosion product expands and collides with the borehole wall; η is the expansion adiabatic index of the detonation product; r b is the blasting hole radius, mm; B = [(1 + b) 2 +(1+b 2 )-2μ d (1-μ d )(1-b) 2 ] 1 / 2 , b=μ d / 1-μ d , μ d is the dynamic Poisson's ratio of the rock mass, μ is the static Poisson's ratio of the rock mass; α and β are the load propagation attenuation indexes, α=2+μ d / 1-μ d , β=2-μ d / 1-μ d .

[0040] Step three, according to step two, determine the construction point of the pressure relief chamber 5 and the distance L between adjacent pressure relief chambers 5, and excavate multiple pressure relief chambers 5 from the return air level tunnel 1 and the transport level tunnel 2 through the negative coal pillar area to the two sides of the coal wall of the isolated working face 10. The pressure relief chamber 5 is used to pre-relieve pressure on the isolated working face 10 and provide workers with space for constructing pressure relief drilling holes; the construction of the pressure relief chamber 5 adopts the step working face construction method or the pilot tunnel construction method. These two methods are used because they cause less disturbance to the surrounding rock during construction and the construction methods are more mature.

[0041] Step 4: construct a large-diameter borehole 4 and a blasting borehole 6 in each pressure relief chamber 5 toward the isolated island working face. According to the principle of unloading rock burst, determine the parameters of the large-diameter borehole 4 and the blasting borehole 6 to ensure that the cracks generated by the construction of the large-diameter borehole 4 are interconnected to form a weakened zone, and the blasting borehole 6 forms a continuous broken layer after blasting; determine the parameters of the large-diameter borehole 4 and the blasting borehole 6, specifically:

[0042] The hole depth S1 of the large-diameter borehole 4 is determined according to the drilling position of the borehole. When drilling in the isolated working face 5, the hole depth of the borehole is 1 to 3 times the mining height; when drilling holes on both sides of the tunnel, the hole depth of the borehole is 3 to 4 times the mining height. The actual length is determined according to the actual drilling construction length on site combined with the pressure relief effect of practical feedback; the specific calculation formula for the construction hole diameter D1 of the large-diameter borehole 4 is as follows:

[0043] D1=ωl(3)

[0044] Where: l is the height of the strip coal pillar in the mine, m; strip coal pillar refers to the coal pillar left behind by strip mining; ω is the proportional coefficient, ranging from 0.05 to 0.10;

[0045] The hole diameter D2 of the blasting drill hole 6 is 60 mm to 100 mm, and is comprehensively selected according to the width of the isolated island working surface 10, the thickness and hardness of the rock layer; the specific calculation formula of the hole depth S2 of the blasting drill hole 6 is as follows:

[0046]

[0047] Where: H is the vertical distance from the key induced coal layer to the strip residual coal pillar; θ is the rock formation pressure relief angle, which is related to the properties of the rock formation.

[0048] Step 5. After the construction is completed, at least two methods, namely the drill cuttings method and the stress online monitoring method, are used to evaluate the pre-pressure relief effect of the isolated working face 10 after the current construction pressure relief. If the evaluations of the two methods both meet the pressure relief requirements, it is determined that the pressure relief requirements are met, otherwise it is determined that the pressure relief requirements are not met. If the pressure relief requirements are met, the pressure relief construction of the isolated working face 10 is completed; if not, it is necessary to increase the construction density of large-diameter drill holes 4 and blasting drill holes 6 in each pressure relief chamber 5 until the pre-pressure relief effect of the isolated working face 10 meets the pressure relief requirements and the pressure relief work is completed.

[0049] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preventing and controlling rock burst in an isolated working face of a rock burst mine, characterized in that: The specific steps are: Step 1: excavate the return air tunnel and the transport tunnel from the goafs on both sides of the isolated working face, and leave a certain distance of goaf between each tunnel and the isolated working face as a negative coal pillar; Step 2: Preset multiple pressure relief chamber construction points in the return air lane and the transport lane respectively. The pressure relief chamber construction points in each lane are equally spaced along their respective directions. Then, determine the influence radius R1 of large-diameter drilling pressure relief and the influence radius R2 of blasting pressure relief, and then determine the spacing L between adjacent pressure relief chambers in each lane. The length of L satisfies L≥2R3, and R3 is the larger value between R1 and R2, so as to ensure that the pressure relief area covers the entire island working surface and has the required pressure relief effect. Step 3: Determine the construction point of the pressure relief chamber and the distance L between adjacent pressure relief chambers according to step 2, and excavate multiple pressure relief chambers from the return air level and the transport level through the negative coal pillar area to the two sides of the coal wall of the isolated island working face. The pressure relief chambers are used to pre-depressurize the isolated island working face and provide space for workers to construct pressure relief drilling holes; Step 4: In each pressure relief chamber, large-diameter drilling and blasting drilling are constructed toward the isolated island working face. According to the principle of unloading rock burst, the parameters of large-diameter drilling and blasting drilling are determined to ensure that the cracks generated by the large-diameter drilling construction are interconnected to form a weakened zone, and a continuous broken layer is formed after blasting of the blasting drilling; Step 5. After the construction is completed, a monitoring method is used to evaluate the pre-pressure relief effect of the isolated working face after the current construction pressure relief. If the pressure relief requirements are met, the pressure relief construction of the isolated working face is completed; if not, it is necessary to increase the construction density of large-diameter drilling and blasting drilling in each pressure relief chamber until the pre-pressure relief effect of the isolated working face meets the pressure relief requirements and the pressure relief work is completed.

2. The method for preventing and controlling rock burst in isolated island working face of rock burst mine according to claim 1, characterized in that: When setting the negative coal pillar in step 1, it is necessary to set the negative coal pillar at the low stress part of the goaf according to the stress condition of the isolated island working face, determine the reasonable size of the negative coal pillar and determine the setting distance L1 of the negative coal pillar.

3. The method for preventing and controlling rock burst in isolated island working face of rock burst mine according to claim 1, characterized in that: The influence radius R1 of the large diameter drilling pressure relief in step 2 is as follows: Where: S is the loose coefficient of the hole wall of the island working face and the two sides of the tunnel; K is the drilling cuttings coefficient, and Q1 is the amount of drill cuttings when drilling a large-diameter hole at a high-stress position on the island working face, and Q2 is the amount of drill cuttings when drilling a large-diameter hole at a normal-stress position on the island working face; The blasting pressure relief influence radius R2, the specific formula is: where σ cd and σ ld is the uniaxial dynamic compressive strength and uniaxial dynamic tensile strength of the rock mass, MPa; ρ0 is the density of the explosive, Kg / m3; D c is the blasting speed of explosives, m / s; K is the radial uncoupled charge coefficient; l c is the axial charge coefficient; n is the pressure increase coefficient when the explosive explosion product expands and collides with the borehole wall; η is the expansion adiabatic index of the detonation product; r b is the blasting hole radius, mm; B = [(1 + b) 2 +(1+b 2 )-2μ d (1-μ d )(1-b) 2 ] 1 / 2 , b=μ d / 1-μ d , μ d is the dynamic Poisson's ratio of the rock mass, μ is the static Poisson's ratio of the rock mass; α and β are the load propagation attenuation indexes, α=2+μ d / 1-μ d , β=2-μ d / 1-μ d .

4. The method for preventing and controlling rock burst in isolated island working face of rock burst mine according to claim 1, characterized in that: The construction of the pressure relief chamber in step three adopts the step working surface construction method or the pilot tunnel construction method.

5. The method for preventing and controlling rock burst in isolated island working face of rock burst mine according to claim 1, characterized in that: The parameters of large diameter drilling and blasting drilling are determined in step 4, specifically: The depth S1 of the large-diameter borehole is determined according to the drilling position of the borehole. When drilling on an isolated island working face, the depth of the borehole is 1 to 3 times the mining height; when drilling on both sides of the tunnel, the depth of the borehole is 3 to 4 times the mining height. The actual length is determined based on the actual drilling construction length on site combined with the pressure relief effect of practical feedback; the specific calculation formula for the construction aperture D1 of the large-diameter borehole is as follows: D1=ωl (3) Where: l is the height of the strip coal pillar left in the mine, m; ω is the proportionality coefficient; The hole diameter D2 of the blasting drilling hole is 60mm~100mm; the specific calculation formula of the hole depth S2 of the blasting drilling hole is as follows: Where: H is the vertical distance from the key induced coal layer to the strip residual coal pillar; θ is the rock formation pressure relief angle, which is related to the properties of the rock formation.

6. The method for preventing and controlling rock burst in isolated island working face of rock burst mine according to claim 1, characterized in that: In the step five, at least two methods, namely the drill cuttings method and the stress online monitoring method, are used to respectively evaluate the pre-pressure relief effect of the isolated island working face after the current construction pressure relief. If both evaluation methods meet the pressure relief requirements, it is determined that the pressure relief requirements are met; otherwise, it is determined that the pressure relief requirements are not met.

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