Extra-thick coal seam roadway bottom coal self-replacement-gob-side entry retaining scour prevention combined arrangement method

Abstract

The invention discloses an extra-thick coal seam roadway bottom coal self-replacement-gob-side entry retaining scour prevention combined arrangement method, which comprises the following steps of: crushing bottom coal with specific width and depth at the lower part of a haulage roadway in a slotting manner in a haulage roadway tunneling process, and transporting the crushed bottom coal to a slotted position for compacting; the self-replacement process of the bottom coal of the haulage roadway is achieved, and stress concentration of the coal body on the lower portion of the haulage roadway is prevented by destroying the integrity of the bottom layer coal body; then, a haulage roadway of an upper section is reserved in a gob-side entry retaining mode in the stoping process of the upper section of the top layer, in this way, the pressure relief effect of the previous slotting can be kept, and secondary unloading is conducted on stress of a coal body on the lower portion of the haulage roadway by combining the gob-side entry retaining mode with the previous slotting; finally, the periphery of the haulage roadway is located in a stress reduction area, safe mining of the top layer under the roadway bottom coal retaining environment during mining of the ultra-thick coal seam is achieved, and the purpose of source scour prevention is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of safe production in coal mines, and in particular to a combined arrangement method for self-replacement of bottom coal in a roadway of an extra-thick coal seam and anti-bumping of a roadway retained along the goaf. Background Art

[0002] In the downward mining of extra-thick coal seams with strong impact tendency, the method of mining top layers first is adopted for mining. Especially when the thickness of the extra-thick coal seam is greater than 8m, since the height of the transport tunnel of the working face is less than the thickness of the coal seam, in order to avoid the roof collapse accident caused by leaving the top coal, the tunnel is excavated along the top and leaving the bottom coal. Because the bottom of this kind of tunnel is a high-strength coal body and is in an open and unsupported state, the stress concentration of the bottom layer coal body is high, and it is easy to cause floor-type rock burst. In order to reduce the probability of rock burst in this kind of tunnel during its use, the previous technology is to use a large-diameter drilling pressure relief method on the bottom plate during the excavation of the transport tunnel to reduce the stress concentration of the tunnel bottom plate, and then use the grouting reinforcement method to strengthen the strength of the bottom plate; the above-mentioned pressure relief method is better when the bottom plate is a loose, low-strength rock layer or coal body, but when the bottom plate of the transport tunnel is a thick coal seam, its stress concentration is high, and the above-mentioned pressure relief method cannot effectively unload the bottom coal impact pressure.

[0003] Therefore, how to provide a new method to effectively unload the high stress of the lower bottom coal of the tunnel during the top layer mining of extra-thick coal seams with strong impact tendency, reduce the stress concentration of the lower bottom coal of the tunnel during the excavation of the upper section transportation tunnel and the upper section mining of the top layer of the extra-thick coal seam, prevent the occurrence of bottom plate type impact ground pressure, achieve the purpose of source prevention, and ensure the safe progress of the excavation of the transportation tunnel and the mining of the top layer coal mining face, 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 combined arrangement method of self-replacement of bottom coal in extra-thick coal seam tunnels and anti-bumping of gob-retained tunnels, which can effectively solve the above-mentioned technical problems.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a method for the joint arrangement of self-replacement of bottom coal in extra-thick coal seam roadway and anti-bumping of gob-side roadway retention, the specific steps of which are:

[0006] Step 1: In the downward mining of the extra-thick coal seam with strong impact tendency, the method of prioritizing the top layer is adopted for mining. In order to improve the coal recovery rate and the efficiency of tunnel support, the transport level tunnel of the top layer is excavated along the roof of the coal seam, and preventive pressure relief drilling is carried out at the excavation working face;

[0007] Step 2: During the excavation of the transport tunnel in the upper section of the top layer, blasting or large-diameter drilling is used to reduce the stress concentration of the surrounding rock at the excavation head and the side wall of the transport tunnel;

[0008] Step 3: During the excavation of the transport tunnel in the upper section of the top layer, the stress concentration of the bottom coal in the lower part of the tunnel is relatively high. In order to avoid the impact of the bottom coal, the bottom coal is crushed to relieve the pressure at the beginning of the excavation tunnel. Specifically, the machinery is arranged at the beginning of the excavation of the transport tunnel in the upper section of the top layer, and a mining excavator loader is used to groove the bottom layer coal body at the bottom of the transport tunnel. The width of the crushing groove is A and the depth is h. The groove is constructed along the excavation direction of the transport tunnel. The crushed coal body produced by the groove is transported by a transfer conveyor to the grooved part behind the mining excavator loader for compaction, so as to realize the self-replacement process of the bottom coal of the transport tunnel. With the excavation process of the transport tunnel, the integrity of the bottom coal is continuously destroyed, the high stress of the bottom coal is unloaded, and the bottom coal is relieved once;

[0009] Step 4. When the top layered transport tunnel is excavated, the bottom coal grooving and pressure relief work is closely followed by the excavation of the transport tunnel. During excavation, the bottom coal in the lower part of the transport tunnel is continuously grooved and self-replaced for pressure relief. The stress concentration degree of the bottom coal is checked according to the bottom plate type rock burst hazard warning index. According to the bottom plate type rock burst warning index, the distance between the bottom coal grooving and pressure relief position and the excavation head is adjusted. That is, if the rock burst warning index is high, it means that the risk of rock burst is high. At this time, the distance between the two should be shortened, which can achieve a better pressure relief effect.

[0010] Step 5. Before starting mining of the upper section of the top layer, first determine the width of the filling body along the goaf, and then adopt the goaf-retaining method to mine the upper section of the top layer. Since grooving and self-replacement have already been used for pressure relief, the transport tunnel of the upper section is retained by retaining the goaf, and the stress of the bottom coal of the transport tunnel is secondary relieved, so that the area around the transport tunnel is in a stress reduction zone, thereby ensuring the safe mining of the extra-thick coal seam.

[0011] Furthermore, in the step 1, at a position within 10 m from the excavation head in the transport tunnel, the drilling construction is completed at one time according to the bottom plate type impact ground pressure prevention design requirements, so as to achieve the effect of pre-pressure relief before excavation.

[0012] Furthermore, the extremely thick coal seam with strong impact tendency in step 1 refers to a coal seam with a burial depth exceeding 400m, a thickness greater than 8m, and a hard rock layer with a single layer thickness exceeding 10m within 100m above the coal seam.

[0013] Furthermore, the depth h of the crushing and grooving in step three is the thickness of the bottom layer coal body; the width A is determined according to the bucket width of the mining excavator loader used in the construction, that is, the width A is equal to the bucket width.

[0014] Furthermore, in the step 4, the bottom coal slotting and pressure relief work is carried out immediately after the excavation of the transport level tunnel, and the distance between the two is maintained in the range of 5 to 10 meters.

[0015] Furthermore, the specific process of determining the width of the filling body of the gob-side entry retaining in step 5 is as follows: assuming that the width of the filling body of the gob-side entry retaining is Z, it is calculated according to the following formula:

[0016]

[0017] Where: q is the load transmitted to the bottom coal of the gob-side roadway in the extra-thick coal seam, b is the roadway span, m; h1 is the collapse height of the roof of the adjacent gob, m; L is the length of the fracture block above the coal pillar, m; y is the bulk density of the roof rock layer, KN / m 3 ; M is the thickness of the extra-thick coal seam, m; α is the basic breaking angle, °.

[0018] Further, the height H and width T of the mining excavator loader in step 3 are determined as follows:

[0019] Assuming the height of the transport tunnel is X and the width is Y, the height H and width T must satisfy XH≥1m, YT≥3m.

[0020] Furthermore, after the stress of the bottom coal in the lower part of the transport tunnel is relieved for the second time, the stress will generally not be concentrated again. However, during the mining process, due to the influence of force majeure factors, the stress in the crushed and compacted bottom coal area at the lower part of the original transport tunnel is redistributed, and there may be a certain impact tendency. Therefore, CT inversion or electromagnetic radiation method is used to monitor the stress concentration degree of the bottom coal. If the stress concentration of the bottom coal is detected, large-diameter drilling or blasting is performed to relieve the stress of the bottom coal at the original slotted and compacted part of the lower part of the transport tunnel to relieve the stress of the bottom coal again.

[0021] Compared with the prior art, since the stress concentration degree of the lower bottom coal area is relatively high during the excavation of the transport tunnel, in order to avoid the occurrence of bottom plate type impact ground pressure, the present invention uses a mining excavator loader to break the bottom coal of a specific width and depth in the lower part of the transport tunnel by slotting during the excavation of the transport tunnel, and then uses a transfer conveyor to transport the broken bottom coal to the slotted area behind the mining excavator loader for compaction, thereby realizing the self-replacement process of the bottom coal of the transport tunnel (that is, the original whole coal body is formed into a broken coal body by slotting and backfilling), and the stress concentration of the lower coal body of the transport tunnel is prevented by destroying the integrity of the bottom layer coal body; in order to further reduce the stress concentration degree of the lower coal body of the transport tunnel, the method of retaining the tunnel along the goaf is used to retain the upper section of the transport tunnel during the mining process of the upper section of the top layer, so that the pressure relief effect of the previous slotting can be maintained, and the stress of the lower coal body of the transport tunnel is secondary unloaded by combining the method of retaining the tunnel along the goaf with the previous slotting, so that the area around the transport tunnel is finally in a stress reduction zone. The present invention solves the problem of easy impact of the bottom coal of the transport tunnel during top layer mining of extra-thick coal seams with strong impact tendency by combining self-replacement of bottom coal grooving in the transport tunnel with leaving tunnel along the goaf during mining of the upper section of the top layer. This realizes the safe mining of the top layer in an environment where bottom coal is left in the tunnel during mining of extra-thick coal seams, thus achieving the purpose of preventing impact at the source. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the overall layout of the present invention;

[0023] Figure 2 yes Figure 1 Rotational cross-section along the mid-DD direction.

[0024] In the figure: 1-basic roof; 2-direct roof; 3-coal mining working face in the lower section of the top layer; 4-transportation level tunnel; 5-filling body along the goaf; 6-goaf area in the upper section of the top layer; 7-bottom layer coal body; 8-groove; 9-bottom plate. DETAILED DESCRIPTION

[0025] The present invention will be further described below.

[0026] like Figure 1 and 2 As shown, the specific steps of the present invention are:

[0027] Step 1: In the downward mining of extra-thick coal seams with strong impact tendency, the method of prioritizing the top layer is adopted for mining. In order to improve the coal recovery rate and tunnel support efficiency, the top layer transportation tunnel is excavated along the coal seam roof, and preventive pressure relief drilling is carried out on the excavation working face; in the transportation tunnel within 10m from the excavation head, the drilling construction is completed in one go according to the bottom plate type impact ground pressure prevention design requirements to achieve the effect of pre-pressure relief before excavation. The extra-thick coal seam with strong impact tendency refers to a hard rock layer with a burial depth of more than 400m, a coal seam thickness of more than 8m, and a single layer of more than 10m thick within 100m above the coal seam.

[0028] Step 2: During the excavation of the transport tunnel in the upper section of the top layer, blasting or large-diameter drilling is used to reduce the stress concentration of the surrounding rock at the excavation head and the side wall of the transport tunnel;

[0029] Step 3: During the excavation of the transport tunnel in the upper section of the top layer, the stress concentration of the bottom coal in the lower part of the tunnel is relatively high. In order to avoid the impact of the bottom coal, the bottom coal is crushed to relieve pressure at the beginning of the excavation tunnel. Specifically, the machinery is arranged at the beginning of the excavation of the transport tunnel in the upper section of the top layer, and a mining excavator loader is used to groove the bottom layer coal body at the bottom of the transport tunnel. The width of the crushing groove is A and the depth is h. The groove is constructed along the excavation direction of the transport tunnel. The crushed coal body produced by the groove is transported by a transfer conveyor to the grooved part behind the mining excavator loader for compaction, so as to realize the self-replacement process of the bottom coal of the transport tunnel. With the excavation process of the transport tunnel, the integrity of the bottom coal is continuously destroyed, the high stress of the bottom coal is unloaded, and the bottom coal is relieved once. The depth h of the crushing groove is the thickness of the bottom layer coal body. The width A is determined according to the bucket width of the mining excavator loader used in the construction, that is, the width A is equal to the bucket width. The height H and width T of the mining excavator loader are determined as follows:

[0030] Assuming the height of the transport tunnel is X and the width is Y, the height H and width T must satisfy XH≥1m, YT≥3m.

[0031] Step 4: When the top layer transport tunnel is excavated, the bottom coal slotting and pressure relief work is closely followed by the excavation of the transport tunnel, and the distance between the two is kept in the range of 5 to 10 meters. During excavation, the bottom coal of the transport tunnel is continuously slotted and self-replaced for pressure relief, and the stress concentration of the bottom coal is checked according to the floor type rock burst hazard warning index. According to the floor type rock burst warning index, the distance between the bottom coal slotting and pressure relief position and the excavation head is adjusted. Specifically, if the rock burst warning index is high, the distance between the slotting and pressure relief position and the excavation head is shortened. The original distance between the two is kept in the range of 5 to 10 meters. When adjusting, the excavation head is suspended. After the slotting work is carried out to 1 to 5 meters away from the excavation head, the two are pushed forward at the same time. By shortening the direct distance between the two, the required pressure relief effect is guaranteed.

[0032] Step 5: Before starting mining in the upper section of the top layer, determine the width of the backfill body along the gob. The specific process is: assuming that the width of the backfill body along the gob is Z, it is calculated according to the following formula:

[0033]

[0034] Where: q is the load transmitted to the bottom coal of the gob-side roadway in the extra-thick coal seam, b is the roadway span, m; h1 is the collapse height of the roof of the adjacent gob, m; L is the length of the fracture block above the coal pillar, m; y is the bulk density of the roof rock layer, KN / m 3 ; M is the thickness of the extra-thick coal seam, m; α is the basic breaking angle, °.

[0035] Then, the upper section of the top layer is mined by retaining a tunnel along the goaf. Since grooving and self-replacement have already relieved pressure once, the transport tunnel of the upper section is retained by retaining a tunnel along the goaf, and the stress of the bottom coal in the transport tunnel is relieved for a second time, so that the area around the transport tunnel is in a stress reduction zone, thereby ensuring the safe mining of the extra-thick coal seam.

[0036] As an improvement of the present invention, after the stress of the bottom coal in the lower part of the transport tunnel is unloaded for the second time, the stress will generally not be concentrated again. However, during the mining process, due to the influence of force majeure factors, the stress in the crushed and compacted bottom coal area in the lower part of the original transport tunnel is redistributed, and there may be a certain impact tendency. Therefore, CT inversion or electromagnetic radiation method is used to monitor the stress concentration degree of the bottom coal. If it is monitored that the stress of the bottom coal is concentrated, large-diameter drilling or blasting is performed to unload the stress of the bottom coal at the original slotted and compacted part of the lower part of the transport tunnel, so as to unload the stress of the bottom coal again.

[0037] 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 self-replacement of bottom coal in extra-thick coal seam roadway and joint arrangement of gob-side roadway anti-bumping, characterized in that: The specific steps are: Step 1: In the downward mining of the extra-thick coal seam with strong impact tendency, the method of prioritizing the top layer is adopted for mining work. The transport level tunnel of the top layer is excavated along the roof of the coal seam, and preventive pressure relief drilling is carried out on the excavation working face; Step 2: During the excavation of the transport tunnel in the upper section of the top layer, blasting or large-diameter drilling is used to reduce the stress concentration of the surrounding rock at the excavation head and the side wall of the transport tunnel; Step 3: During the excavation of the transport tunnel in the upper section of the top layer, the stress concentration of the bottom coal in the lower part of the tunnel is relatively high. In order to avoid the impact of the bottom coal, the bottom coal is crushed to relieve the pressure at the beginning of the excavation tunnel. Specifically, the machinery is arranged at the beginning of the excavation of the transport tunnel in the upper section of the top layer, and a mining excavator loader is used to groove the bottom layer coal body at the bottom of the transport tunnel. The width of the crushing groove is A and the depth is h. The groove is constructed along the excavation direction of the transport tunnel. The crushed coal body produced by the groove is transported by a transfer conveyor to the grooved part behind the mining excavator loader for compaction, so as to realize the self-replacement process of the bottom coal of the transport tunnel. With the excavation process of the transport tunnel, the integrity of the bottom coal is continuously destroyed, the high stress of the bottom coal is unloaded, and the bottom coal is relieved once; Step 4: When the top layer transport tunnel is excavated, the bottom coal slotting and pressure relief work is closely followed by the excavation of the transport tunnel. During excavation, the bottom coal at the bottom of the transport tunnel is continuously slotted and self-replaced for pressure relief. The stress concentration of the bottom coal is checked according to the floor type rock burst hazard warning index. According to the floor type rock burst hazard warning index, the distance between the bottom coal slotting and pressure relief position and the excavation head is adjusted; Step 5. Before starting mining of the upper section of the top layer, first determine the width of the filling body along the goaf, and then adopt the goaf-retaining method to mine the upper section of the top layer. Since grooving and self-replacement have already been used for pressure relief, the transport tunnel of the upper section is retained by retaining the goaf, and the stress of the bottom coal of the transport tunnel is secondary relieved, so that the area around the transport tunnel is in a stress reduction zone, thereby ensuring the safe mining of the extra-thick coal seam.

2. The method for self-replacement of bottom coal in extra-thick coal seam roadway and anti-bumping combined arrangement of gob-side entry retention according to claim 1 is characterized in that: In the step 1, the drilling construction is completed at one time at a location within 10m from the excavation head of the transport tunnel according to the bottom plate type impact ground pressure prevention design requirements, so as to achieve the effect of pre-pressure relief before excavation.

3. The method for self-replacement of bottom coal in extra-thick coal seam roadway and anti-bumping combined arrangement of gob-side roadway retention according to claim 1 is characterized in that: The extremely thick coal seam with strong impact tendency in step 1 refers to a coal seam with a burial depth exceeding 400m, a thickness greater than 8m, and a hard rock layer with a single layer thickness exceeding 10m within 100m above the coal seam.

4. The method for self-replacement of bottom coal in extra-thick coal seam roadway and anti-bumping combined arrangement of gob-side roadway retention according to claim 1 is characterized in that: The depth h of the crushing and grooving in step 3 is the thickness of the bottom layer coal body; the width A is determined according to the bucket width of the mining excavator loader used in the construction.

5. The method for self-replacement of bottom coal in extra-thick coal seam roadway and anti-bumping combined arrangement of gob-side roadway retention according to claim 1 is characterized in that: In the step 4, the bottom coal slotting and pressure relief work is closely followed by the excavation of the transport level tunnel, and the distance between the two is maintained in the range of 5 to 10 meters.

6. The method for self-replacement of bottom coal in extra-thick coal seam roadway and anti-bumping combined arrangement of gob-side roadway retention according to claim 1 is characterized in that: The specific process of determining the width of the filling body of the gob-side entry retaining in step 5 is as follows: assuming that the width of the filling body of the gob-side entry retaining is Z, it is calculated according to the following formula: Where: q is the load transmitted to the bottom coal of the gob-side roadway in the extra-thick coal seam, b is the roadway span, m; h1 is the collapse height of the roof of the adjacent gob, m; L is the length of the fracture block above the coal pillar, m; y is the bulk density of the roof rock layer, KN / m 3 ; M is the thickness of the extra-thick coal seam, m; α is the basic breaking angle, °.

7. The method for self-replacement of bottom coal in extra-thick coal seam roadway and anti-bumping combined arrangement of gob-side roadway retention according to claim 1 is characterized in that: The height H and width T of the mining backhoe loader in step 3 are determined as follows: Assuming the height of the transport tunnel is X and the width is Y, the height H and width T must satisfy XH≥1m, YT≥3m.

8. The method for self-replacement of bottom coal in extra-thick coal seam roadway and anti-bumping combined arrangement of gob-side roadway retention according to claim 1 is characterized in that: After the stress of the bottom coal in the transport tunnel is relieved for the second time, the stress concentration of the bottom coal is monitored by CT inversion or electromagnetic radiation method during the mining process. If the stress concentration of the bottom coal is detected, large-diameter drilling or blasting is performed to relieve the stress of the bottom coal at the original slotting and compacting location in the lower part of the transport tunnel to relieve the stress of the bottom coal again.

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