L-shaped roadway excavation through pressure relief method

Abstract

The application discloses an L-shaped roadway driving and penetrating support pressure relief method, which determines a pressure relief scheme of each region according to the relationship between the size of a coal pillar and the depth of a coal wall to be relieved, constructs a fixed-diameter pressure relief borehole in the driving head along the axial direction of the roadway at a penetrating position, constructs a variable-diameter pressure relief borehole in the production side of the penetrated roadway towards the working face, constructs a roof blasting borehole in the coal pillar inside the driving roadway if the size of the coal pillar exceeds the depth of the coal wall to be relieved, and constructs a roof blasting borehole in the shoulder of the non-production side of the driving roadway if the size of the coal pillar does not exceed the depth of the coal wall to be relieved. The method improves the driving and penetrating efficiency of the roadway, protects the support strength of the original support body of the roadway while ensuring the pressure relief effect of the driving region to be relieved, and significantly reduces the impact risk degree during the driving and penetrating of the L-shaped roadway.

Description

Technical Field

[0001] This invention belongs to the field of tunnel excavation and pressure relief technology, specifically relating to a method for pressure relief during L-shaped tunnel excavation and support. Background Technology

[0002] With the large-scale mining of coal resources, the reserves of shallow coal resources are constantly decreasing. Domestic coal mining has begun to shift from shallow mining to deep mining. Mine mining will face a more complex geological environment. Under the high stress conditions in the deep coal seam, the tunneling of the roadway, especially when the tunnel is completed, is very likely to induce rock burst accidents.

[0003] When a roadway is excavated and connected, the conventional pressure relief measures are to construct advance pressure relief holes along the roadway axis at the excavation face to pre-depressurize the coal body in front of the excavation face, and at the same time, to construct fan-shaped holes at a certain angle away from the roadway axis at the excavation face to pre-depressurize the coal body on both sides of the excavation face.

[0004] There are three problems with the conventional pressure relief measures. First, most mines currently use the tunneling and anchoring process, and due to the limited space for pressure relief construction, it is difficult to construct pressure relief holes ahead of the face. Second, when the "L-shaped" roadway is completed, the short-short ...

[0005] To improve tunneling efficiency while ensuring tunnel support strength and reducing impact risks during tunnel breakthrough, the key is to reduce stress concentration in the breakthrough area while maintaining tunnel support strength. This invention comprehensively considers tunneling technology, tunneling efficiency, decompression efficiency, decompression effect, and the special engineering conditions of "L-shaped" tunnels, proposing a decompression and support method for "L-shaped" tunnel breakthrough, which is of great significance for the safe and efficient breakthrough of "L-shaped" tunnels. Summary of the Invention

[0006] The purpose of this invention is to provide a method for stress relief and support during L-shaped tunnel excavation and breakthrough, which solves the problem of low excavation efficiency caused by short excavation and unloading at the face during the breakthrough of existing L-shaped tunnels, and the damage to the sidewall support caused by the fan-shaped holes on both sides.

[0007] The technical solution adopted in this invention is: a method for stress relief through support during L-shaped tunnel excavation, and the specific operation steps are as follows:

[0008] Step 1: Based on the relationship between the coal pillar size and the depth of the coal wall to be depressurized, determine the depressurization scheme for the roadway tunneling through the depressurization area.

[0009] Step 2: Determine the breakthrough point based on the tunnel excavation method;

[0010] Step 3: Design the depressurization parameters for each area to be depressurized;

[0011] Step 4: Perform pre-depressurization treatment in each area to be depressurized;

[0012] Step 5: Excavate the connecting tunnel within the pressure relief range.

[0013] The invention is further characterized in that,

[0014] Preferably, the method for determining the depth of coal wall to be depressurized is as follows:

[0015] If the coal seam thickness is less than 3.5m, the pressure relief depth shall not be less than 15m;

[0016] If the coal seam thickness is 3.5 to 8m, the pressure relief depth should not be less than 20m.

[0017] If the mining thickness is greater than 8m, the pressure relief depth should be no less than 25m.

[0018] Preferably, if the coal pillar size exceeds the coal wall pressure relief depth, fixed-diameter pressure relief boreholes are arranged in the area to be excavated, variable-diameter pressure relief boreholes are arranged in the working face pressure relief area, and fan-shaped blasting holes are arranged in the solid coal pressure relief area. If the coal pillar size does not exceed the coal wall pressure relief depth, fixed-diameter pressure relief boreholes are arranged in the area to be excavated, variable-diameter pressure relief boreholes are arranged in the working face pressure relief area, and axial blasting holes are arranged in the solid coal pressure relief area.

[0019] Preferably, the breakthrough location is determined according to the tunnel excavation method, which mainly includes determining the specific location of the breakthrough location in the tunnel, the length of the tunnel to be excavated area, and the length from the corner to the breakthrough location.

[0020] Preferably, the pressure relief boreholes in the area to be excavated are located at the breakthrough point, and construction proceeds from the breakthrough point towards the excavation face. At least three boreholes are drilled, oriented along the roadway axis, with a length equal to the length of the area to be excavated. This allows for the early release of energy within the coal seam ahead of the excavation face, reducing stress concentration.

[0021] Preferably, in the area to be depressurized on the working face, a variable-diameter depressurization borehole is constructed. The starting position of the borehole is offset from the production side of the tunneling roadway, and the offset distance is not less than the support length of the production side support of the tunneling roadway. The drilling direction is along the axial direction of the tunneling roadway, and the borehole length is equal to the sum of the length of the area to be excavated and the distance from the corner to the breakthrough position. The borehole is divided into a small-diameter part and a large-diameter part. The diameter of the small-diameter part is not greater than 120mm, and the length is not less than the support length of the production side support of the already penetrated roadway. The diameter of the large-diameter part is not less than 200mm, so as to ensure that the stress concentration of the coal in the area to be depressurized on the working face is reduced while protecting the roadway support from being damaged by the depressurization activity.

[0022] Preferably, if the coal pillar size exceeds the coal wall's unloading depth, a pair of symmetrically distributed fan-shaped blasting holes are arranged in the solid coal unloading area. The blasting hole construction position should ensure that the sealing length is not less than one-third of the blasting hole length, the horizontal direction of the borehole deviates from the roadway axis by 15° to 75°, and the elevation angle is 30° to 75°, ensuring that the borehole end position exceeds the coal wall's unloading depth, and the cracks generated by the blasting at the end positions of the two blasting holes are connected.

[0023] If the coal pillar size does not exceed the depth of the coal wall to be unloaded, axial blasting holes should be arranged in the solid coal unloaded area. The construction position of the blasting holes should ensure that the sealing length is not less than one-third of the blasting hole length. The drilling direction should be along the roadway axis, with an elevation angle of 30° to 75°, and the crack range generated by the blasting at the end of the blasting holes at both ends should be continuous.

[0024] Preferably, the sum of the length of the unstressed area of ​​the working face and the support length of the production wall support of the roadway to be penetrated should exceed the unstressed depth of the coal wall of the production wall of the roadway to be penetrated, so as to ensure the unstressing effect of the coal body in the unstressed area of ​​the working face.

[0025] The beneficial effects of this invention are as follows: The L-shaped roadway excavation and connection support decompression method of this invention involves constructing fixed-diameter decompression holes in the reverse direction along the roadway axis towards the area to be excavated at the connection point. This ensures a good decompression effect on the coal body in the area to be excavated, while avoiding mutual interference between roadway face excavation and face decompression construction, thus improving roadway excavation efficiency. In another roadway, variable-diameter decompression holes are constructed in the area to be decompressed at the working face from the production side. These are equivalent to fan-shaped holes constructed at the face, with the smaller diameter length not less than the length of the production side support of the already connected roadway. The starting position of the construction deviates from the length of the production side support of the roadway to be connected. Based on the relationship between the coal pillar size and the depth of the coal wall to be decompressed, fan-shaped roof blasting holes are constructed in the roadway to be connected towards the coal pillar, or axial roof blasting holes are constructed towards the shoulder of the coal pillar. This ensures a good decompression effect on the coal body in the connection area while avoiding the damage to the support structures on both sides of the roadway to be connected caused by conventional large-diameter decompression drilling. Therefore, this invention is of great significance in improving the excavation efficiency of "L-shaped" roadways, the coal body decompression effect, and ensuring the original support strength of the roadways, as well as in ensuring efficient and safe production in mines. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the arrangement of pressure relief boreholes along the axial direction of the tunnel in this invention.

[0027] Figure 2 This is a schematic diagram of the axial pressure relief drilling arrangement of parallel tunnels in the tunnels that have been penetrated in this invention;

[0028] Figure 3 This is a schematic diagram of the blast hole's inclination profile if the coal pillar size exceeds the coal wall's unloading depth in this invention.

[0029] Figure 4 This is a schematic diagram of the blast hole orientation if the coal pillar size does not exceed the coal wall pressure relief depth in this invention.

[0030] Figure 5 This is a schematic diagram of the layout of L-shaped roadway tunneling and support pressure relief boreholes if the coal pillar size exceeds the coal wall pressure relief depth.

[0031] Figure 6 This is a schematic diagram of the layout of the L-shaped roadway tunneling and support pressure relief boreholes if the coal pillar size does not exceed the coal wall pressure relief depth.

[0032] In the diagram: GH - roadway to be connected, XH - roadway already connected, 1 - connection location, 2 - tunneling face, 3 - starting position of production side pressure relief hole construction in the connected roadway, 4 - location of roof blasting hole construction in the connected area, 5 - location of roof blasting hole construction in the tunneling face area. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0034] Example 1

[0035] This invention discloses a method for stress relief during L-shaped roadway excavation and connection. An already connected roadway and a roadway to be connected are arranged in an "L" shape. The connection point is determined in the roadway to be connected. Stress relief boreholes are drilled in the reverse direction along the roadway axis at the excavation face towards the connection point. Stress relief boreholes are also drilled in the stress relief area of ​​the working face in the already connected roadway towards the working face. Fan-shaped blasting holes are drilled into the coal pillar or axial blasting holes are drilled into the shoulder of the coal pillar in the roadway to be connected. This method improves the efficiency of roadway excavation and connection, ensures the stress relief effect of the coal body to be unloaded in the connection area, and protects the support strength of the original roadway support structure. It can significantly reduce the impact risk during the connection of the "L-shaped" roadway. Figure 1-4 As shown, the details are as follows:

[0036] Step 1: Based on the relationship between the coal pillar size and the depth of the coal wall to be depressurized, determine the depressurization scheme for the roadway excavation and breakthrough of the depressurization area; arrange fixed diameter depressurization boreholes in the area to be excavated, arrange variable diameter depressurization boreholes in the working face area to be depressurized, and arrange blasting holes A and B in the solid coal area to be depressurized; the blasting angles of blasting holes A and B are determined according to the relationship between the coal pillar size and the depth of the coal wall to be depressurized.

[0037] The breakthrough location is determined based on the excavation method of the roadway GH to be broken through. This mainly includes determining the length of the area to be excavated in the roadway GH to be broken through, and the distance of the breakthrough location from the corner. The corner is formed by the vertically interconnected already broken roadway XH and the roadway GH to be broken through.

[0038] The specific method for determining the depth of coal face pressure relief is as follows:

[0039] If the coal seam thickness is less than 3.5m, the pressure relief depth shall not be less than 15m;

[0040] If the coal seam thickness is 3.5 to 8m, the pressure relief depth should not be less than 20m.

[0041] If the mining thickness is greater than 8m, the pressure relief depth should be no less than 25m.

[0042] Step 2: Determine the breakthrough point based on the tunnel excavation method;

[0043] Step 3: Design the depressurization parameters for each area to be depressurized;

[0044] Design fixed-diameter pressure relief boreholes in the area to be excavated in roadway GH. The construction position of the fixed-diameter pressure relief boreholes is located at the breakthrough position, and construction is carried out from the breakthrough position towards the excavation face. The number of boreholes shall not be less than 3, and the direction shall be along the axis of roadway GH. They shall be arranged in a positive three-flower or inverted three-flower pattern, and the length shall be guaranteed to penetrate the length of the area to be excavated in roadway GH.

[0045] A variable-diameter pressure relief borehole is designed in the pressure relief area of ​​the working face. The construction location is in roadway XH, with the starting position offset from the production sidewall of roadway GH. The offset distance is equal to the support length of the production sidewall support of roadway GH. The drilling direction is along the axial direction of roadway GH. The borehole length is equal to the sum of the length of the area to be excavated in roadway GH and the distance from the breakthrough point to the corner. The borehole is divided into a small-diameter part and a large-diameter part. The diameter of the small-diameter part is not greater than 120mm and the length is not less than the support length of the production sidewall support of roadway XH. The diameter of the large-diameter part is not less than 200mm. This is to ensure that the stress concentration of the coal body in the pressure relief area of ​​the working face is reduced while protecting the support of roadway GH and the production sidewall of roadway XH from damage by the pressure relief activity.

[0046] In step 3, if the coal pillar size exceeds the depth of the coal wall to be depressurized, symmetrical blasting holes A and B are arranged in the solid coal depressurization area. Blasting hole A ensures that the sealing length is not less than one-third of the length of blasting hole A. The horizontal direction of the borehole deviates from the GH axis of the roadway by 15° to 75°, and the elevation angle is 30° to 75°. The final position of the borehole is ensured to exceed the depth of the coal wall to be depressurized. Blasting hole B ensures that the sealing length is not less than one-third of the length of blasting hole B. The other parameters are the same as those of blasting hole A. The cracks generated by the blasting at the final positions of blasting holes A and B are connected.

[0047] If the coal pillar size does not exceed the depth of the coal wall to be depressurized, the drilling direction of blasting hole A and blasting hole B is along the GH axis of the roadway, and is carried out towards the roof of the area to be excavated, with an elevation angle of 30° to 75°.

[0048] Step 4: Perform pre-decompression treatment in each area to be decompressed; when the pre-decompression measures are completed, the remaining tunneling distance should not be less than 50m.

[0049] The sum of the length of the pressure relief drilling area and the support length of the GH production side support of the roadway should exceed the peak value of the GH production side support stress in order to ensure the pressure relief effect of the coal body in the pressure relief area of ​​the working face.

[0050] Step 5: Excavate the connecting tunnel within the pressure relief range.

[0051] Example 2

[0052] The L-shaped roadway excavation and connection support method provided by this invention is applied to a coal mine. The already connected roadway XH is the cut-in, and the roadway GH to be connected is the return airway. The production side support length L3 of the return airway is 7m, the coal seam thickness is 6m, the coal wall pressure relief depth is 20m, and the coal pillar size is 30m. Figure 5 As shown, it includes the following steps:

[0053] Step 1: Based on the relationship between the coal pillar size and the depth of the coal wall to be unloaded, determine the unloading scheme for the S1 area to be unloaded during the tunneling and breakthrough of the GH roadway.

[0054] Specifically, if the coal pillar size exceeds the depth of the coal wall to be depressurized, a fixed diameter depressurization borehole K1 is constructed in the area to be excavated S1, a variable diameter depressurization borehole K2 is constructed in the area to be depressurized S2 of the working face, and fan-shaped blasting holes A and B are constructed in the area to be depressurized S3 of the solid coal in the roadway to be penetrated GH.

[0055] Step 2: Determine the breakthrough point 1 based on the tunnel excavation method;

[0056] Specifically, the tunnel is excavated and connected at position 1 of the GH connection point. The length L1 from the corner to the connection point is 20m, and the length L2 of the tunnel to be excavated is 50m.

[0057] Step 3: Design the depressurization parameters for each area to be depressurized;

[0058] Specifically, at the tunnel GH breakthrough point 1, five fixed-diameter pressure relief boreholes K1 are constructed at the tunnel face 2, arranged in an inverted three-row pattern. The borehole diameter is 200mm, with the lower row 0.5-1.5m from the floor and the upper row 0.5-2.0m from the floor. The spacing between adjacent boreholes in the upper and lower rows is 1m. The boreholes are 50m long and run along the axial direction of the tunnel GH to be penetrated. In the XH tunnel, perpendicular to the production side face towards the working face in the pressure relief area S2, variable-diameter pressure relief boreholes K2 are constructed. The starting position 3 of the pressure relief boreholes in the already penetrated production side face is 7m away from the return tunnel GH by the length L3. The construction length L4 is 13m, with a small diameter of 120mm and a length of L5 of 10m. The large diameter is 200mm and the length is... The length L6 is 60m, the distance from the bottom plate is 0.5 to 1.5m, and the hole spacing is 1m. In the tunnel GH, the length L7 of the tunnel GH is 10m from the tunnel GH (i.e., the construction position 4 of the roof blasting hole in the tunnel GH) and the length L8 of the tunneling face is 10m from the tunneling face (i.e., the construction position 5 of the roof blasting hole in the tunneling face), the roof blasting holes A and B are respectively constructed towards the solid coal unloading area S3. The hole depth is 39m, the deviation from the tunnel GH axis is 35°, the elevation angle is 30°, and the charge length is 25m. This makes the blasting gap S4 at the end of the roof blasting hole A in the tunnel GH connected with the blasting gap S5 at the end of the roof blasting hole B in the tunneling face.

[0059] Step 3: Perform pre-depressurization treatment in each area to be depressurized;

[0060] Specifically, the pre-decompression works for each pressure-relief area will be completed when there are 50m of tunneling remaining.

[0061] Step 4: Excavate the through roadway GH within the pressure relief range.

[0062] Specifically, after the pre-depressurization works in each depressurization area are completed, excavation begins from the tunnel face 2 of roadway GH until the roadway is completed.

[0063] Example 3

[0064] The L-shaped roadway excavation and connection support stress relief method provided by this invention is applied to a coal mine. The already connected roadway XH is the cut-in, and the roadway GH to be connected is the return airway. The length of the production support structure in the return airway is L3, which is 7m. The coal seam thickness is 6m, the stress relief depth of the coal wall is 20m, and the coal pillar size is 6m. Figure 6 As shown, it includes the following steps:

[0065] Step 1: Based on the relationship between the coal pillar size and the depth of the coal wall to be unloaded, determine the unloading scheme for the S1 area to be unloaded during the tunneling and breakthrough of the GH roadway.

[0066] Specifically, since the coal pillar size does not exceed the coal wall pressure relief depth, a fixed diameter pressure relief borehole K1 is to be constructed in the area to be excavated S1, a variable diameter pressure relief borehole K2 is to be constructed in the area to be pressure relief S2 of the working face, and axial blasting holes A and B are to be constructed in the roof of the roadway to be penetrated GH towards the solid coal pressure relief area S3.

[0067] Step 2: Determine the breakthrough point 1 based on the tunnel excavation method;

[0068] Specifically, the tunnel was excavated and connected at point 1 of the tunnel GH connection point. The length L1 from the corner to the connection point is 20m, and the length L2 of the tunnel to be excavated is 50m.

[0069] Step 3: Design the depressurization parameters for each area to be depressurized;

[0070] Specifically, at the tunnel GH breakthrough point 1, five fixed-diameter pressure relief boreholes K1 are constructed at the tunnel face 2, arranged in an inverted three-row pattern. The borehole diameter is 200mm, with the lower row 0.5-1.5m from the floor and the upper row 0.5-2.0m from the floor. The spacing between adjacent boreholes in the upper and lower rows is 1m. The boreholes are oriented along the tunnel GH axis and have a length of 50m. In the XH tunnel, perpendicular to the production side face, in the pressure relief area S2, variable-diameter pressure relief boreholes K2 are constructed. The construction location is 7m away from the tunnel GH by a length L3, and the construction area length L4 is 13m. The smaller diameter is 120mm, with a length L5 of 10m, and the larger diameter is 200mm, with a length L6 of [missing information]. 60m, 0.5-1.5m from the bottom plate, 1m spacing between holes; in the tunnel GH, one roof blast hole A and one roof blast hole B are constructed in the tunnel GH at a length L7 10m from the tunnel GH (i.e., the construction position 4 of the roof blast hole in the tunnel GH) and the tunneling face area at a length L8 10m from the tunneling face (i.e., the construction position 5 of the roof blast hole in the tunneling face) towards the solid coal unloading area S3. The hole depth is 34m, along the tunnel GH axis, at an elevation angle of 30°, and the charge length is 22m, so that the blasting fracture S4 at the end of the roof blast hole A in the tunnel GH is connected to the blasting fracture S5 at the end of the roof blast hole B in the tunneling face area.

[0071] Step 3: Perform pre-depressurization treatment in each area to be depressurized;

[0072] Specifically, the pre-decompression works for each pressure-relief area will be completed when there are 50m of tunneling remaining.

[0073] Step 4: Excavate the through roadway GH within the pressure relief range.

[0074] Specifically, after the pre-depressurization works in each depressurization area are completed, excavation will begin from the GH excavation face 2 of the roadway to be connected until the roadway is connected.

Claims

1. A method for stress relief and support during L-shaped tunnel excavation, characterized in that, Includes the following steps: Step 1: Based on the relationship between the coal pillar size and the depth of the coal wall to be depressurized, determine the depressurization scheme for the roadway tunneling through the depressurization area. In step 1, fixed-diameter pressure relief boreholes are arranged in the area to be excavated, variable-diameter pressure relief boreholes are arranged in the area to be pressure relieved in the working face, and blasting holes A and B are arranged in the area to be pressure relieved in the solid coal. The blasting angles of blasting holes A and B are determined according to the relationship between the size of the coal pillar and the depth to be pressure relieved in the coal wall. The breakthrough location is determined based on the excavation method of the roadway GH to be broken through. This mainly includes determining the length of the area to be excavated in the roadway GH to be broken through, and the distance of the breakthrough location from the corner. The corner is formed by the vertically interconnected already broken roadway XH and the roadway GH to be broken through. Step 2: Determine the breakthrough point based on the tunnel excavation method; Step 3: Design the depressurization parameters for each area to be depressurized; In step 3, if the coal pillar size exceeds the depth of the coal wall to be depressurized, symmetrical blasting holes A and B are arranged in the solid coal depressurization area. Blasting hole A ensures that the sealing length is not less than one-third of the length of blasting hole A. The horizontal direction of the borehole deviates from the GH axis of the roadway by 15°~75°, and the elevation angle is 30°~75° to ensure that the end position of the borehole exceeds the depth of the coal wall to be depressurized. Blasting hole B ensures that the sealing length is not less than one-third of the length of blasting hole B. The other parameters are the same as those of blasting hole A, and the cracks generated by the blasting at the end positions of blasting holes A and B are connected. If the coal pillar size does not exceed the coal wall pressure relief depth, the drilling of blasting hole A and blasting hole B is carried out horizontally along the GH axis of the roadway towards the roof of the area to be excavated, with an elevation angle of 30°~75°. Step 4: Perform pre-depressurization treatment in each area to be depressurized; Step 5: Excavate the connecting tunnel within the pressure relief range.

2. The method for stress relief and support during L-shaped tunnel excavation and breakthrough according to claim 1, characterized in that, The method for determining the depth of the coal wall to be depressurized is as follows: If the coal seam thickness is less than 3.5m, the pressure relief depth shall not be less than 15m; If the coal seam thickness is 3.5~8m, the pressure relief depth should not be less than 20m; If the mining thickness is greater than 8m, the pressure relief depth should be no less than 25m.

3. The method for stress relief and support during L-shaped tunnel excavation and breakthrough according to claim 1, characterized in that, Step 3 is as follows: Design fixed-diameter pressure relief boreholes in the area to be excavated in roadway GH. The construction location of the fixed-diameter pressure relief boreholes is located at the breakthrough position, and construction is carried out from the breakthrough position towards the excavation face. The number of boreholes shall not be less than 3, and the direction shall be along the axis of roadway GH. They shall be arranged in a positive three-flower or inverted three-flower pattern, and the length shall be guaranteed to penetrate the length of the area to be excavated in roadway GH.

4. The method for stress relief and support during L-shaped tunnel excavation and breakthrough according to claim 1, characterized in that, In step 3, variable-diameter pressure relief boreholes are designed in the pressure-relief area of ​​the working face. The construction location is in roadway XH. The starting position of the pressure relief boreholes in the production side of the already penetrated roadway is offset from the production side of roadway GH. The offset distance is equal to the support length of the production side support of roadway GH. The drilling direction is along the axial direction of roadway GH. The drilling length is equal to the sum of the length of the area to be excavated in roadway GH and the distance from the penetration position to the corner. The borehole is divided into a small-diameter part and a large-diameter part. The diameter of the small-diameter part is not greater than 120mm and the length is not less than the support length of the production side support of roadway XH. The diameter of the large-diameter part is not less than 200mm. This is to ensure that the stress concentration of the coal body in the pressure-relief area of ​​the working face is reduced while protecting the support of the production side of roadway GH and roadway XH from being damaged by the pressure relief activities.

5. The method for stress relief and support during L-shaped tunnel excavation and breakthrough according to claim 1, characterized in that, The sum of the length of the pressure relief borehole construction area and the support length of the GH production side support of the roadway should exceed the peak value of the GH production side support stress in order to ensure the pressure relief effect of the coal body in the pressure relief area of ​​the working face.

6. The method for stress relief and support during L-shaped tunnel excavation and breakthrough according to claim 1, characterized in that, Step 4: Perform pre-decompression treatment in each area to be decompressed. When the pre-decompression measures are completed, the remaining tunneling distance should not be less than 50m.

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