Combined arrangement method of self-replacement of roadway floor coal in extra-thick coal seam and anti-caving along gob

Abstract

The application discloses a kind of thick coal seam roadway floor coal self replacement-gob-side entry retaining combined arrangement method, in the process of excavating transport roadway, the specific width and depth of floor coal under transport roadway is broken by the way of grooving after, and the broken floor coal is transported to the place that has been grooved to compact, realize the self replacement process of floor coal of transport roadway, by destroying the integrity of bottom slice coal body, prevent stress concentration of coal body under transport roadway;Then, the upper section of top slice mining process is retained by the way of gob-side entry retaining, which can maintain the pressure relief effect of previous grooving, and the stress of coal body under transport roadway is unloaded twice by the way of gob-side entry retaining combined with previous grooving, finally, the surrounding of transport roadway is in stress reduction zone, realizes the safe mining of top slice under the environment of roadway leaving floor coal in thick coal seam mining, and achieves the purpose of source prevention.

Description

Technical Field

[0001] This invention belongs to the field of coal mine safety production technology, specifically a combined arrangement method of bottom coal self-replacement and goaf retention for anti-scour in extra-thick coal seam roadways. Background Technology

[0002] In the downward mining of extra-thick coal seams with a strong tendency for rockburst, the method of prioritizing the mining of the top layer is adopted for mining operations. Especially when the thickness of the extra-thick coal seam exceeds 8m, because the height of the haulage roadway is less than the thickness of the coal seam, the haulage roadway is excavated along the roof while leaving the bottom coal to avoid roof collapse accidents. This type of roadway, due to its bottom being a high-strength coal body in an open and unsupported state, has a high stress concentration in the bottom coal body, making it prone to floor-type rockbursts. To reduce the probability of rockbursts during the service life of this type of roadway, previous techniques involved using large-diameter boreholes to relieve stress on the floor during haulage roadway excavation, followed by grouting reinforcement to strengthen the floor. While this stress relief method works well when the floor is a loose, low-strength rock strata or coal body, it is ineffective when the haulage roadway floor is a thick coal seam with high stress concentration, as the above methods cannot effectively unload the bottom coal rockburst pressure.

[0003] Therefore, the research direction required by this invention is to provide a new method for effectively unloading the high stress in the bottom coal of the roadway during the top-layer mining of extra-thick coal seams with strong impact tendency, reducing the stress concentration in the bottom coal of the roadway during the excavation of the upper section of the top-layer mining of extra-thick coal seams and the mining of the upper section, preventing the occurrence of bottom-type rockbursts, achieving the purpose of preventing rockbursts at the source, and ensuring the safe progress of the excavation of the transport roadway and the mining of the top-layer mining face. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a combined arrangement method of bottom coal self-replacement and goaf-prevention roadway retention in extra-thick coal seams, which can effectively solve the aforementioned technical problems.

[0005] To achieve the above objectives, the technical solution adopted by this invention is: a combined arrangement method of bottom coal self-replacement and goaf-prevention roadway retention in extra-thick coal seams, the specific steps of which are as follows:

[0006] Step 1: In the downward mining of extra-thick coal seams with strong impact tendency, the method of prioritizing the mining of the top layer is adopted for mining operations. In order to improve the coal extraction rate and roadway support efficiency, the transport roadway of the top layer is excavated along the roof of the coal seam, and preventive pressure relief boreholes are drilled at the excavation face.

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

[0008] Step 3: During the excavation of the top-layer upper section transport roadway, the stress concentration of the bottom coal in the lower part of the roadway is relatively high. To avoid bottom coal impact, the bottom coal is crushed at the beginning of the roadway for decompression. Specifically, machinery is arranged at the beginning of the excavation of the top-layer upper section transport roadway. A mining excavator loader is used to cut grooves in the bottom coal body of the lower part of the transport roadway. The width of the crushing groove is A and the depth is h. The groove is cut along the excavation direction of the transport roadway. The crushed coal body produced by the groove is transported by a transfer conveyor to the grooved area behind the mining excavator loader for compaction. This realizes the self-replacement process of the bottom coal in the transport roadway. As the transport roadway is excavated, the integrity of the bottom coal is continuously destroyed, the high stress of the bottom coal is unloaded, and the bottom coal is decompressed once.

[0009] Step 4: During the excavation of the top-layer transport roadway, the bottom coal trenching and pressure relief work closely follows the excavation face of the transport roadway. During excavation, continuous trenching and self-replacement pressure relief measures are carried out on the bottom coal in the lower part of the transport roadway. The stress concentration of the bottom coal is checked according to the floor-type rockburst hazard warning index. Based on the floor-type rockburst warning index, the distance between the bottom coal trenching and pressure relief position and the excavation face is adjusted. That is, if the rockburst warning index is high, it indicates that the risk of rockburst is greater. At this time, the distance between the two should be shortened to achieve a better pressure relief effect.

[0010] Step 5: Before starting the upper section mining of the top layer, first determine the width of the filling body of the gob-side retaining roadway, and then use the gob-side retaining roadway method to carry out the upper section mining of the top layer. Since the slotting and self-replacement have already carried out one stress relief, by retaining the upper section's transport roadway through the gob-side retaining roadway, the stress of the bottom coal in the lower part of the transport roadway is relieved a second time, so that the area around the transport roadway is in a stress reduction zone, thereby ensuring the safe mining of the extra-thick coal seam.

[0011] Furthermore, in step one, drilling is carried out in one go at a location within 10m of the tunnel face in the transport tunnel, in accordance with the design requirements for bottom plate type rock pressure prevention, so as to achieve the effect of pre-depressurization before tunneling.

[0012] Furthermore, the strong impact-prone extra-thick coal seam in step one refers to a coal seam with a burial depth of more than 400m, a coal seam thickness of more than 8m, and a hard rock layer with a single layer thickness of more than 10m within 100m above the coal seam.

[0013] Furthermore, in step three, the depth h of the crushing and slotting is the thickness of the bottom layer of coal; 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 step four, the bottom coal trenching and pressure relief work closely follows the excavation face of the transport roadway, and the distance between the two is maintained within the range of 5 to 10 meters.

[0015] Furthermore, the specific process for determining the width of the gob-side retaining fill in step five is as follows: Let the width of the gob-side retaining fill be Z, then it is calculated according to the following formula:

[0016]

[0017] In the formula: q is the load transferred to the bottom coal of the roadway along the extra-thick coal seam; b is the roadway span (m); h1 is the roof collapse height of the adjacent goaf (m); L is the length of the fracture block of the main roof above the coal pillar (m); y is the unit weight of the roof strata (kN / m³). 3 M is the thickness of the extra-thick coal seam, in meters; α is the basic roof breaking angle, in degrees.

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

[0019] Let the height of the transport tunnel be X and the width be Y. Then the height H and the width T must satisfy XH≥1m and YT≥3m.

[0020] Furthermore, after the stress in the bottom coal of the lower part of the transport roadway is relieved for the second time, the stress generally will not concentrate again. However, due to the influence of force majeure during the mining process, the stress in the bottom coal area that has been broken and compacted in the original transport roadway may be redistributed, which may have a certain tendency to impact. Therefore, CT inversion or electromagnetic radiation methods are used to monitor the stress concentration of the bottom coal. If stress concentration is detected in the bottom coal, large-diameter drilling or blasting is carried out on the coal body in the original slotted and compacted area in the lower part of the transport roadway to relieve the stress of the bottom coal again.

[0021] Compared with existing technologies, due to the high stress concentration in the lower coal seam area during the excavation of transport level tunnels, this invention avoids the occurrence of floor-type rockbursts. During the excavation process, a mining excavator loader is used to create slots to break the lower coal seam of a specific width and depth. A transfer conveyor then transports the broken coal to the slotted area behind the mining excavator loader for compaction, achieving a self-replacement process of the lower coal seam (i.e., breaking the original monolithic coal body into a broken coal body through slotting and backfilling). By disrupting the integrity of the bottom coal layer, stress concentration in the lower coal seam of the transport level tunnel is prevented. To further reduce the stress concentration in the lower coal seam of the transport level tunnel, a gob-side retention method is used during the mining of the upper section of the top layer to retain the upper section of the transport level tunnel. This maintains the stress relief effect of the previous slotting and, by combining the gob-side retention method with the previous slotting, a secondary stress unloading is performed on the lower coal seam of the transport level tunnel, ultimately placing the area around the transport level tunnel in a stress-reduced zone. This invention solves the problem of easy impact on the bottom coal in the transport roadway during the mining of top-layered extra-thick coal seams with strong impact tendency by combining the self-replacement of bottom coal in the transport roadway with the combination of the top layer mining and the retention of roadway along the goaf. It achieves safe mining of the top layer under the condition of retaining bottom coal in the roadway during the mining of extra-thick coal seams and achieves the purpose of preventing impact at the source. Attached Figure Description

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

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

[0024] In the diagram: 1-basic roof; 2-direct roof; 3-lower section coal mining face of the roof layer; 4-transport roadway; 5-goaf backfill; 6-upper section goaf of the roof layer; 7-lower section coal body; 8-slot; 9-floor plate. Detailed Implementation

[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 as follows:

[0027] Step 1: In the downward mining of extra-thick coal seams with a strong tendency to rock bursts, the method of prioritizing the mining of the top layer is adopted. To improve the coal extraction rate and roadway support efficiency, the haulage roadway of the top layer is excavated along the roof of the coal seam, and preventive pressure relief boreholes are drilled at the excavation face. Within 10m of the excavation face in the haulage roadway, borehole construction is completed in one go according to the bottom-type rock burst prevention design requirements to achieve the effect of pre-pressure relief before excavation. The extra-thick coal seam with a strong tendency to rock bursts refers to a coal seam with a burial depth of more than 400m, a coal seam thickness of more than 8m, and a single layer of hard rock with a thickness of more than 10m within 100m above the coal seam.

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

[0029] Step 3: During the excavation of the top-layer upper section transport roadway, the stress concentration of the bottom coal in the lower part of the roadway is relatively high. To avoid bottom coal impact, a bottom coal crushing method is used to relieve pressure at the beginning of the excavation. Specifically, machinery is arranged at the beginning of the top-layer upper section transport roadway excavation. A mining excavator loader is used to cut grooves in the bottom coal layer of the lower part of the transport roadway. The width of the crushing groove is A, and the depth is h. The groove is constructed along the excavation direction of the transport roadway. The crushed coal produced by the groove is transported by a transfer conveyor to the grooved area behind the mining excavator loader for compaction, realizing the self-replacement process of the bottom coal in the transport roadway. As the transport roadway is excavated, the integrity of the bottom coal is continuously destroyed, unloading the high stress of the bottom coal and completing the first-stage pressure relief of the bottom coal. The depth h of the crushing groove is the thickness of the bottom coal layer. 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] Let the height of the transport tunnel be X and the width be Y. Then the height H and the width T must satisfy XH≥1m and YT≥3m.

[0031] Step 4: During the excavation of the top-level transport roadway, the bottom coal trenching and pressure relief work should closely follow the excavation face of the transport roadway, with the distance between the two maintained within the range of 5-10m. During excavation, continuous trenching and self-replacement pressure relief measures should be implemented on the bottom coal in the lower part of the transport roadway. The stress concentration degree of the bottom coal should be checked according to the floor-type rockburst hazard warning index. Based on the floor-type rockburst warning index, the distance between the bottom coal trenching and pressure relief position and the excavation face should be adjusted. Specifically: if the rockburst warning index is high, the distance between the trenching and pressure relief position and the excavation face should be shortened. The original distance should be maintained within the range of 5-10m. During the adjustment, the excavation face work should be suspended. After the trenching work reaches 1-5 meters from the excavation face, both should proceed simultaneously. By shortening the direct distance between them, the required pressure relief effect can be ensured.

[0032] Step 5: Before commencing mining in the upper section of the top layer, first determine the width of the fill material for the gob-side retaining area. The specific process is as follows: Let the width of the fill material for the gob-side retaining area be Z, then calculate it according to the following formula:

[0033]

[0034] In the formula: q is the load transferred to the bottom coal of the roadway along the extra-thick coal seam; b is the roadway span (m); h1 is the roof collapse height of the adjacent goaf (m); L is the length of the fracture block of the main roof above the coal pillar (m); y is the unit weight of the roof strata (kN / m³). 3 M is the thickness of the extra-thick coal seam, in meters; α is the basic roof breaking angle, in degrees.

[0035] Furthermore, the method of retaining the roadway along the gob is adopted for the mining of the upper section of the top layer. Since the trenching and self-replacement have already relieved the pressure once, the method of retaining the roadway along the gob preserves the transport roadway of the upper section, and relieves the stress of the bottom coal in the lower part of the transport roadway a second time, so that the area around the transport roadway 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 roadway is depressurized twice, the stress will generally not concentrate again. However, during the mining process, due to the influence of force majeure, the stress in the bottom coal area that has been broken and compacted in the lower part of the original transport roadway is redistributed, which may have a certain tendency to impact. Therefore, CT inversion or electromagnetic radiation methods are used to monitor the stress concentration of the bottom coal. If stress concentration is detected in the bottom coal, large-diameter drilling or blasting is performed on the coal body in the original slotted and compacted area in the lower part of the transport roadway to depressurize it again and unload the stress of the bottom coal.

[0037] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A combined arrangement method of self-replacement of bottom coal and gob-side roadway anti-scour in extra-thick coal seam roadways, characterized in that, The specific steps are as follows: Step 1: In the downward mining of extra-thick coal seams with strong impact tendency, the method of prioritizing the mining of the top layer is adopted for mining operations. The transport roadway of the top layer is excavated along the roof of the coal seam, and preventive pressure relief boreholes are drilled at the excavation face. Step 2: During the excavation of the upper section of the top layer transport tunnel, blasting or large-diameter drilling is used at the excavation face and sidewalls of the transport tunnel to reduce the stress concentration of the surrounding rock. Step 3: During the excavation of the top-layer upper section transport roadway, the stress concentration of the bottom coal in the lower part of the roadway is relatively high. To avoid bottom coal impact, the bottom coal is crushed at the beginning of the roadway for decompression. Specifically, machinery is arranged at the beginning of the excavation of the top-layer upper section transport roadway. A mining excavator loader is used to cut grooves in the bottom coal body of the lower part of the transport roadway. The width of the crushing groove is A and the depth is h. The groove is cut along the excavation direction of the transport roadway. The crushed coal body produced by the groove is transported by a transfer conveyor to the grooved area behind the mining excavator loader for compaction. This realizes the self-replacement process of the bottom coal in the transport roadway. As the transport roadway is excavated, the integrity of the bottom coal is continuously destroyed, the high stress of the bottom coal is unloaded, and the bottom coal is decompressed once. Step 4: During the excavation of the top-layer transport roadway, the bottom coal trenching and pressure relief work follows the excavation face of the transport roadway. During the excavation, the bottom coal in the lower part of the transport roadway is continuously trenched and self-replaced to relieve pressure. The stress concentration of the bottom coal is checked according to the bottom plate type rockburst hazard warning index. Based on the bottom plate type rockburst hazard warning index, the distance between the bottom coal trenching and pressure relief position and the excavation face is adjusted. Step 5: Before starting the upper section mining of the top layer, first determine the width of the filling body of the gob-side retaining roadway, and then use the gob-side retaining roadway method to carry out the upper section mining of the top layer. Since the slotting and self-replacement have already carried out one stress relief, by retaining the upper section's transport roadway through the gob-side retaining roadway, the stress of the bottom coal in the lower part of the transport roadway is relieved a second time, so that the area around the transport roadway is in a stress reduction zone, thereby ensuring the safe mining of the extra-thick coal seam.

2. The method for combined arrangement of bottom coal self-replacement and goaf-prevention roadway retention in extra-thick coal seams according to claim 1, characterized in that, In step one, drilling is carried out in one go at a location within 10m of the tunnel face in the transport tunnel, in accordance with the design requirements for anti-rock pressure of the bottom plate type, so as to achieve the effect of pre-depressurization before tunneling.

3. The method for combined arrangement of bottom coal self-replacement and gob-side roadway anti-scour in extra-thick coal seam roadways according to claim 1, characterized in that, In step one, a strong impact-prone extra-thick coal seam refers to a coal seam with a burial depth of more than 400m, a coal seam thickness of more than 8m, and a hard rock layer with a single layer thickness of more than 10m within 100m above the coal seam.

4. The combined arrangement method of self-replacement of bottom coal and gob-side roadway anti-scour in extra-thick coal seam roadways according to claim 1, characterized in that, In step three, the depth h of the crushing and slotting is the thickness of the bottom coal layer; the width A is determined according to the bucket width of the mining excavator loader used in the construction.

5. The method for combined arrangement of bottom coal self-replacement and goaf-prevention roadway retention in extra-thick coal seams according to claim 1, characterized in that, In step four, the bottom coal trenching and pressure relief work closely follows the excavation face of the transport roadway, and the distance between the two is maintained within the range of 5 to 10 meters.

6. The combined arrangement method of self-replacement of bottom coal and gob-side roadway anti-scour in extra-thick coal seam roadways according to claim 1, characterized in that, The specific process for determining the width of the gob-side retention filling body in step five is as follows: Let the width of the gob-side retention filling body be Z, then it is calculated according to the following formula: ； In the formula: q is the load transferred to the bottom coal of the roadway along the extra-thick coal seam; b is the roadway span (m); h1 is the roof collapse height of the adjacent goaf (m); L is the length of the fracture block of the main roof above the coal pillar (m); y is the unit weight of the roof strata (kN / m³). 3 M is the thickness of the extra-thick coal seam, in meters; α is the basic roof breaking angle, in degrees.

7. The method for combined arrangement of bottom coal self-replacement and goaf-prevention roadway retention in extra-thick coal seams according to claim 1, characterized in that, The height H and width T of the mining excavator loader in step three are determined as follows: Let the height of the transport tunnel be X and the width be Y. Then the height H and the width T must satisfy XH≥1m and YT≥3m.

8. The method for combined arrangement of bottom coal self-replacement and goaf-prevention roadway retention in extra-thick coal seams according to claim 1, characterized in that, After the stress of the bottom coal in the lower part of the transport roadway is relieved twice, the stress concentration of the bottom coal is monitored by CT inversion or electromagnetic radiation during the mining process. If stress concentration is detected in the bottom coal, large-diameter drilling or blasting is carried out on the coal body in the original slotted and compacted area in the lower part of the transport roadway to relieve the stress of the bottom coal again.

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