Anti-coal uncovering method

Abstract

The invention discloses an anti-coal-uncovering method which comprises the following steps: S1, when two adjacent roadways reveal the same coal seam, after one roadway uncovers the coal seam, designing and constructing an anti-coal-uncovering joint roadway between the adjacent roadways; s2, finding out the coal seam gas condition in the reverse coal uncovering area of the to-be-uncovered coal seam roadway; s3, a to-be-uncovered coal seam roadway reverse coal uncovering area outburst elimination scheme is formulated, and area outburst prevention measures are taken on to-be-uncovered coal seam roadway reverse coal uncovering; s4, reverse coal uncovering operation is carried out, a to-be-uncovered coal seam is constructed to the top of a roadway, a reverse coal uncovering joint roadway and a to-be-uncovered coal seam roadway are constructed along a coal seam top plate, ultrahigh construction is carried out on the roadway and the coal seam top plate, and advanced grouting reinforcement is carried out on a coal body on the top of the coal uncovering roadway; and S5, recovering the designed height of the roadway, adjusting a roadway support mode to be a U-shaped shed, and finishing reverse coal uncovering until the distance between the roadway and the coal seam is 2m. The method has the beneficial effects that the risks of gas overrun and coal seam spontaneous ignition caused by top falling and loosening of a top coal body during roadway construction can be effectively reduced.

Description

Technical Field

[0001] The invention relates to the technical field of coal mines, in particular to a reverse coal stripping method. Background Art

[0002] Coal mining in the tunnels and tunnels is a link with high gas risk in the coal mine production process. Before the coal seam is uncovered, the gas leakage in the coal seam is very small. Once the coal seam is uncovered, a large amount of initial gas expansion energy will be released in the coal body. It may induce gas accidents such as coal and gas outbursts. In order to ensure gas safety during coal mining in the tunnels and tunnels, the "Detailed Rules for Preventing and Controlling Coal and Gas Outbursts" requires that regional anti-outburst measures be implemented before the minimum normal distance of 7m between the coal mining working face and the coal seam. The anti-outburst measures in the coal mining area are generally implemented before the tunnel is 7m away from the coal seam to be uncovered. Drilling sites are constructed on both sides of the tunnel, and through-layer drilling holes are constructed in the drilling sites and the front to pre-extract gas from the coal seam to be uncovered; or the coal mining measures tunnel is constructed, and through-layer drilling holes are constructed in the measures tunnel to pre-extract gas from the coal seam to be uncovered. The anti-outburst measures in the coal mining area are large in quantity, time-consuming, and have high safety risks.

[0003] The existing technology has the following disadvantages: the outburst prevention works in the stone gate coal mining tunnel area of ​​the coal seam outburst danger zone are large in volume, time-consuming and with high safety risks. During the coal mining operation, if the coal seam to be mined is at the top of the tunnel, the coal body is prone to fall off the top and loosen, causing abnormal gas outburst, and the risk of spontaneous combustion of the coal seam is high.

[0004] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art known to a person skilled in the art. Summary of the invention

[0005] The technical problem to be solved by the present invention is: how to solve the problem that the current outburst prevention engineering in the stone gate coal-uncovering tunnel area in the outburst danger zone of the coal seam is large in amount, long in time and has high safety risks.

[0006] The present invention solves the above technical problems through the following technical means:

[0007] The reverse coal stripping method comprises the following steps:

[0008] Step S1: When two adjacent tunnels uncover the same coal seam, after one of the tunnels uncovers the coal seam, a reverse coal uncovering tunnel is designed and constructed between the adjacent tunnels;

[0009] Step S2: Find out the coal seam gas situation in the reverse coal-excavation area of ​​the coal seam roadway to be uncovered;

[0010] Step S3: Formulate a plan for preventing coal outbursts in the counter-excavation area of ​​the coal seam roadway to be exposed, and implement regional measures to prevent coal outbursts in the counter-excavation area of ​​the coal seam roadway to be exposed;

[0011] Step S4: Implement reverse coal stripping operation, construct the coal seam to be stripped to the top of the roadway, construct the reverse coal stripping joint roadway and the coal seam to be stripped along the coal seam roof, construct the super-high construction of the roadway and the coal seam roof, and implement advanced grouting reinforcement on the coal body at the top of the coal stripping roadway;

[0012] Step S5: Restore the designed height of the tunnel, adjust the tunnel support method to a U-shaped shed, and construct until the tunnel is 2m away from the coal seam, and then the reverse coal stripping is completed.

[0013] The present invention provides a reverse coal stripping method, which is applied to when two adjacent tunnels expose the same coal seam. After one tunnel exposes the coal seam, the reverse coal stripping joint tunnel can be designed and constructed in advance to find out the coal seam gas situation in the reverse coal stripping area of ​​the coal seam to be exposed. The reverse coal stripping of the coal seam to be exposed can intuitively and accurately grasp the coal seam gas situation. Compared with normal stone gate coal stripping, reverse coal stripping in the dangerous area of ​​the protruding coal seam adopts pre-extraction and elimination of outbursts by drilling holes in the layer, and the coal seam to be exposed has been exposed in advance, the engineering volume of regional anti-outburst measures is greatly reduced, the coal stripping period is shortened, and the danger of outbursts during construction is reduced. The reverse coal stripping is constructed in advance with the coal seam roof, which can effectively prevent the coal seam at the top of the tunnel from being soft and falling off, causing gas abnormalities; when the coal seam to be exposed is constructed to the top of the tunnel, the coal body at the top of the coal stripping tunnel is reinforced with advanced grouting, which can effectively reduce the risk of gas exceeding the limit and spontaneous combustion of the coal seam caused by the top coal body falling off and loosening during the tunnel construction.

[0014] Preferably, the adjacent lanes in step S1 are intersecting lanes or parallel lanes.

[0015] Preferably, in step S1, after the reverse coal-excavation joint tunnel is constructed, anti-burst measures are taken for the reverse coal-excavation joint tunnel, the reverse coal-excavation joint tunnel is constructed along the coal seam roof, anchor mesh support is adopted, and the reverse coal-excavation joint tunnel construction section is 12 to 20 m2.

[0016] Preferably, in step S2, according to the coal seam gas conditions in the adjacent uncovered coal seam tunnels, the parameters of the reverse coal uncovering area of ​​the coal seam tunnel to be uncovered are inverted to predict the coal seam outburst hazard in the reverse coal uncovering area of ​​the coal seam tunnel to be uncovered.

[0017] Preferably, in step S3, a plan for eliminating coal outbursts in the reverse coal-exposing area of ​​the roadway to be exposed is formulated by pre-pumping and eliminating coal outbursts in the layer-by-layer drilling area.

[0018] Preferably, in step S4, the construction length of the super-high top section of the tunnel is determined according to the thickness, inclination, mechanical properties and tunnel construction angle of the coal seam, and the super-high range is controlled within 2m; during the construction of the top section of the reverse coal-excavating tunnel, anchor mesh support is adopted.

[0019] Preferably, the top plate anchor cable is a Ф22×6200mm long anchor cable with a spacing of 800mm, and the auxiliary rod anchor rod is a Ф22×2500mm high-strength anchor rod with a spacing of no more than 800mm.

[0020] Preferably, in step S4, the advance grouting reinforcement range is 100-120° of the designed tunnel vault, and the advance grouting holes are arranged in the coal seam 40 cm outside the U-shaped shed outline.

[0021] Preferably, the circumferential spacing of the advance grouting holes is 40 cm, the hole diameter is 94 mm, the angle between the borehole and the center line of the tunnel is 8° to 10°, and the length of the borehole can cover the coal stop point in the tunnel.

[0022] Preferably, in step S4, after all the advance grouting holes are constructed and casing is lowered, grouting is performed on the entire front section of the tunnel with a thickness of at least 30 mm; and then grouting is performed on the drilled holes through the advance grouting casing.

[0023] Preferably, the slurry is 0.5:1 to 0.8:1 pure cement slurry, the grouting pressure is 1 to 2 MPa, and cement-water glass double liquid slurry can be partially used. The slurry strength grade is required to be not less than M10, and the grouting volume of a single hole is 1.5 times that of the drilled cylinder.

[0024] Preferably, in step S5, the distance between the U-shaped sheds is 0.4-0.6m; during the erection of the U-shaped shed support, anchor rods are constructed on the top plate.

[0025] Preferably, the anchor rod specification is Ф22×2500mm high-strength anchor rod, with a ring spacing of 40cm as the advance anchor rod, and construction is carried out every 1.2m.

[0026] Preferably, in step S5, the construction is completed until the tunnel is 2m away from the coal seam, and the reverse coal stripping is completed. Grouting treatment is performed on the reverse coal stripping top coal section and the range of 10m before and after, and observation points are set up.

[0027] Preferably, the reverse-uncovered top coal section and the area within 10m before and after it are sprayed with mining composite mortar in a ratio of 1:2, with a spraying thickness of 60mm and a concrete strength of C20, and observation points are set up.

[0028] The advantages of the present invention are:

[0029] 1. When two adjacent tunnels expose the same coal seam, after one tunnel exposes the coal seam, the other tunnel will carry out reverse coal uncovering operations. Compared with normal stone gate coal uncovering, reverse coal uncovering can grasp the coal seam gas situation in the reverse coal uncovering area in advance, and use seam drilling to eliminate coal bursting in the uncovering area. The amount of regional coal bursting prevention measures is greatly reduced, the coal uncovering period is shortened, and the risk of coal bursting during construction is reduced.

[0030] 2. Counter-coal mining should be carried out in advance with the construction of the coal seam roof, and grouting reinforcement measures should be implemented on the coal body at the top of the coal mining tunnel, which can effectively reduce the risk of gas exceeding the limit and spontaneous combustion of the coal seam caused by the top of the tunnel falling and loosening. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a plan view of reverse coal uncovering in which two intersecting tunnels uncover the same coal seam in an embodiment of the present invention;

[0032] Figure 2 It is a plan view of reverse coal uncovering in which two parallel tunnels uncover the same coal seam in an embodiment of the present invention;

[0033] Figure 3 It is a cross-sectional view of a reverse coal-exposing and outburst-eliminating drilling hole in a roadway of a coal seam to be exposed in an embodiment of the present invention;

[0034] Figure 4 Schematic diagram of drilling holes for reverse coal uncovering and eliminating outbursts in a roadway of a coal seam to be uncovered in an embodiment of the present invention;

[0035] Figure 5 It is the drilling data of the coal seam roadway to be uncovered in the embodiment of the present invention;

[0036] Figure 6 It is a cross-sectional view of reverse coal-excavation construction in a roadway of a coal seam to be uncovered in an embodiment of the present invention;

[0037] Figure 7 It is a cross-sectional view of a roadway in a roadway reverse coal uncovering and advanced grouting section in an embodiment of the present invention;

[0038] Figure 8 Schematic diagram of anchor net support for reverse coal-excavation joint tunnel and coal seam tunnel to be exposed in an embodiment of the present invention;

[0039] Fig. 9 Schematic diagram of the advanced grouting casing in an embodiment of the present invention;

[0040] Numbers in the figure:

[0041] 1. The coal seam tunnel has been uncovered;

[0042] 2. Coal seam tunnels to be uncovered;

[0043] 3. Anti-uncovering coal joint lane;

[0044] 4. Control scope of anti-burst measures in the roadway area of ​​the coal seam to be uncovered;

[0045] 5. The section of super-high construction for the roadway with the coal seam to be exposed; 51. The starting point of super-high construction for the roadway with the coal seam to be exposed; 52. The end point of super-high construction for the roadway with the coal seam to be exposed; 53. The starting point of the roadway design height restoration for the roadway with the coal seam to be exposed;

[0046] 6. Advance grouting hole; 61. U-shaped shed;

[0047] 7. Advance grouting casing; 71. Casing cone head; 72. Casing grouting hole; 73. Casing iron hoop. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] The reverse coal stripping method comprises the following steps:

[0050] S1: When two adjacent tunnels uncover the same coal seam, after one of the tunnels uncovers the coal seam, a counter-uncovering tunnel 3 is designed and constructed between the adjacent tunnels.

[0051] Specifically, adjacent lanes may be intersecting lanes or parallel lanes.

[0052] Among the adjacent tunnels, one of them has been uncovered, which is tunnel 1 with uncovered coal seam, and the other has not been uncovered, which is tunnel 2 with unexposed coal seam. Figure 1 As shown, the uncovered coal seam tunnel 1 and the to-be-exposed coal seam tunnel 2 are in an intersecting tunnel relationship. When the two tunnels are in an intersecting relationship, the anti-coal uncovering tunnel 3 is a connecting tunnel that must be constructed. It is a tunnel with multiple uses (in this case, the connecting tunnel and the anti-coal uncovering tunnel are different parts of one tunnel). The anti-coal uncovering tunnel 3 and the to-be-exposed coal seam tunnel 2 are anti-coal uncovering and regional anti-burst measures are taken at one time.

[0053] like Figure 2 As shown, the exposed coal seam tunnel 1 and the to-be-exposed coal seam tunnel 2 are parallel. When the two tunnels are parallel, the anti-coal-exposing tunnel 3 is dedicated to the gas control of the anti-coal-exposing tunnel 2 for the construction of the to-be-exposed coal seam. The distance between the two coal-exposing points should be less than 40m to facilitate the construction of the anti-coal-exposing tunnel 3 and the implementation of anti-coal-exposing. Regional anti-burst measures shall be taken for the anti-coal-exposing tunnel 3 and the anti-coal-exposing tunnel 2 for the to-be-exposed coal seam respectively.

[0054] After taking anti-blowout measures in the anti-coal tunnel 3, the anti-coal tunnel 3 is constructed along the coal seam roof and supported by anchor mesh. The construction section of the anti-coal tunnel 3 is 12 to 20 m2. When necessary, the construction drilling site is used to arrange anti-blowout drilling holes in the anti-coal tunnel to meet the requirements for implementing regional anti-blowout measures in the anti-coal tunnel.

[0055] S2: Find out the coal seam gas situation in the reverse coal-excavation area of ​​the coal seam to be uncovered.

[0056] The coal mining control range is determined in the coal mining tunnel, the coal stopping section and a certain range around it; measures are taken within the coal mining control range to ensure gas safety during the construction of the coal mining tunnel. The "Detailed Rules for Preventing and Controlling Coal and Gas Outbursts" require that the coal mining tunnel be constructed 10m before the coal seam to drill a exploratory hole to find out the thickness, inclination change, and geological structure of the coal seam; and to construct a pressure measurement hole to measure gas pressure, gas content and other parameters to predict the danger of coal seam outbursts in the coal mining area. According to the prediction results of coal seam outburst hazard, the control scope of coal seam gas outburst prevention measures in coal mining tunnels is determined: "The drilling of through-layer drilling holes for pre-extraction of coal seam gas in coal mining areas should be carried out before the minimum normal distance of 7m between the coal mining working face and the coal seam, and through-layer drilling holes should be used to control at least the following coal seams: 12m outside the tunnel contour line at the stone gate and vertical shaft and inclined shaft coal mining (6m at the bottom or lower wall of the steeply inclined coal seam), and at the same time, it should be ensured that the minimum distance from the outer edge of the control range to the tunnel contour line (including the contour line of the tunnel of the expected coal mining section ahead) is not less than 5m. When the regional outburst prevention measures are difficult to complete in one construction, they can be implemented in sections, but each section should be able to ensure that the coal mining working face is within the coal seam at least 20m in front of the tunnel, and the control scope of the regional outburst prevention measures meets the above requirements."

[0057] During the reverse coal stripping of the coal seam roadway 2 to be exposed, the gas parameters such as coal seam gas pressure and gas content of the adjacent exposed coal seam roadway 1 have been measured, and the coal seam thickness, inclination change, top and bottom plate lithology, geological structure and other conditions can be observed intuitively. Therefore, the reverse coal stripping of the coal seam roadway 2 to be exposed can be determined by inversion according to the coal seam gas conditions of the adjacent exposed coal seam roadway and the coal seam gas conditions of the reverse coal stripping joint roadway 3. The coal seam thickness, inclination change, top and bottom plate lithology, geological structure, coal seam gas pressure, gas content and other parameters in the reverse coal stripping area of ​​the coal seam roadway 2 to be exposed can be predicted for the coal seam outburst hazard in the reverse coal stripping area of ​​the coal seam roadway 2 to be exposed. According to the prediction results of coal seam outburst hazard, the control scope of anti-outburst measures in the reverse coal stripping area of ​​the coal seam roadway to be exposed is determined.

[0058] It should be noted that the inversion method is a mature technical solution in this field and will not be described here. After determining the danger of coal seam outburst according to parameters such as geological structure, coal seam gas pressure, and gas content, the greater the gas pressure and gas content, the greater the danger, the larger the control range, and the stricter the measures to be taken.

[0059] S3: Formulate a plan to prevent coal outbursts in the area of ​​the counter-excavation of the coal seam tunnel 2 to be uncovered, and implement regional measures to prevent coal outbursts in the counter-excavation of the coal seam tunnel 2 to be uncovered.

[0060] In this embodiment, the coal is reversely uncovered in the coal seam tunnel 2 in the coal seam outburst danger zone, and pre-extraction is adopted to eliminate outburst by drilling holes in the layer. The axial direction of the borehole is controlled to 5m (7m when the original gas pressure is ≥2MPa) of the tunnel to be excavated and the coal body of the protruding coal seam is controlled to be not less than 20m in front of the coal seam bottom plate (or roof) of the tunnel. The distance between the two sides of the tunnel is controlled to be not less than 15m. The spacing between boreholes is designed according to the effective extraction radius of the coal seam. The borehole diameter is not less than 102mm, and a 1-inch casing is installed throughout the whole process to protect the hole. The drilling sealing depth is not less than 15m.

[0061] All boreholes must be pumped and evaluated before excavation can begin.

[0062] Application location: Coal seam outburst danger zone, coal seam roadway to be uncovered, original gas pressure of coal seam is 2.8MPa, gas content is 8.4m 3 / t, coal seam thickness 5.2m, coal seam dip angle 9°, no fault. The application site is two cross tunnels exposing the same coal seam, reverse coal excavation, reverse coal excavation joint tunnel 3 and the coal seam to be exposed tunnel 2 reverse coal excavation to take regional anti-burst measures at one time (see Figure 1 , Figure 3 ).like Figure 4 , Figure 5 As shown in the figure, the designed anti-burst drilling holes are in-layer drilling holes with a hole diameter of 113mm and a hole bottom spacing of 3m. Two rows of drilling holes are constructed with a three-hole arrangement and a hole depth of 68 to 78m. A total of 29 drilling holes are constructed. After regional pre-extraction, the residual gas pressure is 0.26MPa and the residual gas content is 3.15m 3 / t, the regional pre-pumping evaluation is qualified.

[0063] S4: Implement reverse coal stripping operations;

[0064] S41, super-high construction of the roadway and top of the coal seam to be uncovered;

[0065] The coal seam to be uncovered is constructed to the top of the tunnel, and the counter-excavation coal tunnel 3 and the coal seam tunnel 2 to be uncovered are constructed along the coal seam roof. Anchor net support is used to construct a certain distance between the tunnel and the coal seam roof.

[0066] The coal seam to be uncovered is constructed to the top of the tunnel. The reverse coal tunnel and the coal seam tunnel to be uncovered are constructed along the coal seam roof. Anchor net support is used. The tunnel is constructed at a certain distance from the coal seam roof. The position of the tunnel bottom is determined by the tunnel design function. The tunnel is gradually raised (see Figure 6 ). The length of the super-elevation construction section 5 of the roadway to be exposed, i.e., the length from the starting point 51 of the roadway to be exposed to the end point 52 of the roadway to be exposed, is determined by the thickness, inclination, mechanical properties and roadway construction angle of the coal seam. The super-elevation range is controlled within 2m, i.e., the height difference between the end point 52 of the roadway to be exposed and the starting point 53 of the roadway to be exposed to restore the normal construction height is controlled within 2m.

[0067] The coal seam tunnel to be uncovered and the super-high construction section 5 of the coal seam roof are supported by anchor mesh. The roof anchor cable is Ф22×6200mm long anchor cable with a spacing of 800mm. The auxiliary anchor rod is Ф22×2500mm high-strength anchor rod with a spacing of no more than 800mm to ensure the support strength of the tunnel.

[0068] The thickness of the coal seam is 5.2m, the inclination of the coal seam is 9°, and the design height of the roadway to be exposed is 3.4m. The coal seam to be exposed will be gradually constructed to the top of the roadway to prevent accidents such as excessive gas and spontaneous combustion of the coal seam caused by the top coal body falling off and loosening during the roadway construction. The roadway and the coal seam roof are gradually super-high, and the roadway height gradually increases from 3.4m to 5.4m. Anchor net support is adopted. The top plate anchor cable is Ф22×6200mm long anchor cable with an interval of 800mm. The auxiliary rod anchor is Ф22×2500mm high-strength anchor rod with a spacing of no more than 800mm. The support of the normal section and the super-high section is shown in Figure 8 .

[0069] In the construction of this embodiment, the tunnel and the coal seam roof are super-highly constructed for a certain distance, so that no coal is left on the top of the tunnel, thereby reducing the risk of gas exceeding the limit and spontaneous combustion of the coal seam caused by the top coal body falling off and loosening during the tunnel construction.

[0070] S42. Carry out advance grouting reinforcement on the top coal body of coal mining tunnel 2.

[0071] After the super-high construction section of the coal seam roadway is completed, the roadway design height is restored and adjusted to a U-shaped shed support. Before restoring the roadway design height, grouting reinforcement is carried out on the top of the reverse coal roadway. The grouting reinforcement range is within the 120° range of the designed roadway arch. Figure 7 As shown, the advance grouting hole 6 is arranged in the coal seam 40cm outside the outline of the U-shaped shed 61, with an annular spacing of 40cm, a hole diameter of 94mm, an angle of 8° to 10° between the borehole and the centerline of the tunnel, and the length of the borehole can cover the position of the coal stop point in the tunnel. The advance grouting hole is casingd throughout the entire process. The casing is a seamless steel pipe with a hole diameter of 76mm and a wall thickness of 3.5mm. The length of a single casing is 1.5m. The casing can be connected with a coupling according to the depth of the drilling hole. The front end of the casing is a casing cone head, and the end is a casing stop grouting section with a length of 15cm. There are casing grouting holes with a hole diameter of 6 to 8mm and a hole spacing of 10 to 20mm, arranged in a plum blossom shape.

[0072] After the construction of the advance grouting hole 6, the casing is immediately lowered. After the construction and casing of all the advance grouting holes 6 are completed, the full section of the tunnel is sprayed with 30mm thickness. Then, 0.5:1~0.8:1 pure cement slurry is injected into the borehole through the advance grouting casing 7, and the grouting pressure is 1~2MPa. When the surrounding rock is broken and groundwater is developed, cement-water glass double liquid slurry can be partially used for the purpose of setting, and the slurry strength grade is required to be not less than M10. The grouting volume of a single hole is generally 1.5 times that of the borehole cylinder. If the grouting volume exceeds the limit and still does not reach 1~2MPa, the slurry should be adjusted to continue grouting until it meets the grouting quality standard to ensure that the rock mass around the borehole and the pores around the steel pipe are filled with slurry before grouting can be stopped.

[0073] S5: Restore the designed height of the tunnel, adjust the tunnel support method to a U-shaped shed, and complete the reverse coal stripping until the tunnel is 2m away from the coal seam.

[0074] After the super-high construction section of the coal seam tunnel is completed, the coal body at the top of the coal seam tunnel is reinforced by advanced grouting, and the tunnel is adjusted to a U-shaped shed support method.

[0075] Specifically, the distance between the sheds is 0.6m; during the erection of the U-shaped shed 61 support, high-strength anchor rods with a specification of Ф22×2500mm are used for the top plate construction, with a ring spacing of 40cm as the advance anchor rod, and construction is carried out every 1.2m to prevent roof leakage.

[0076] The construction of the anti-coal mining tunnel is completed when it is 2m away from the coal seam.

[0077] After the reverse coal stripping is completed, the reverse coal stripping top coal section and the range 10m before and after are sprayed with mining composite mortar in a ratio of 1:2. The spraying thickness is 60mm and the concrete strength is C20. Observation points are set up to prevent the occurrence of spalling, roof falling, gas abnormalities, etc. in the tunnel.

[0078] In this embodiment, when two adjacent tunnels expose the same coal seam, after one tunnel uncovers the coal seam, a reverse coal-exposing tunnel can be designed and constructed in advance to find out the coal seam gas situation in the reverse coal-exposing area of ​​the coal seam to be exposed. The reverse coal-exposing of the coal seam to be exposed can intuitively and accurately grasp the coal seam gas situation. Compared with normal stone gate coal-exposing, reverse coal-exposing in the dangerous area of ​​the coal seam with protruding coal adopts pre-extraction and elimination of outbursts in the area by drilling holes along the layer, and the coal seam to be exposed has been exposed in advance. The amount of regional anti-outburst measures is greatly reduced, the coal-exposing period is shortened, and the danger of outbursts during construction is reduced. The reverse coal-exposing is constructed in advance with the coal seam roof, which can effectively prevent the coal seam at the top of the tunnel from becoming soft and falling off, causing gas abnormalities; when the coal seam to be exposed is constructed to the top of the tunnel, the coal body at the top of the coal-exposing tunnel is reinforced with advanced grouting, which can effectively reduce the risk of gas exceeding the limit and spontaneous combustion of the coal seam caused by the top coal body falling off and loosening during the tunnel construction.

[0079] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for reverse coal stripping, characterized in that: The following steps are involved: Step S1: When two adjacent tunnels uncover the same coal seam, after one of the tunnels uncovers the coal seam, a reverse coal uncovering tunnel is designed and constructed between the adjacent tunnels; Step S2: Find out the coal seam gas situation in the reverse coal-excavation area of ​​the coal seam roadway to be uncovered; Step S3: Formulate a plan for preventing coal outbursts in the counter-excavation area of ​​the coal seam roadway to be exposed, and implement regional measures to prevent coal outbursts in the counter-excavation area of ​​the coal seam roadway to be exposed; Step S4: Implement reverse coal stripping operation, construct the coal seam to be stripped to the top of the roadway, construct the reverse coal stripping joint roadway and the coal seam to be stripped along the coal seam roof, construct the super-high construction of the roadway and the coal seam roof, and implement advanced grouting reinforcement on the coal body at the top of the coal stripping roadway; Step S5: Restore the designed height of the tunnel, adjust the tunnel support method to a U-shaped shed, and construct until the tunnel is 2m away from the coal seam, and then the reverse coal stripping is completed.

2. The reverse coal stripping method according to claim 1, characterized in that: In step S1, the adjacent lanes are cross lanes or parallel lanes.

3. The reverse coal stripping method according to claim 1, characterized in that: In the step S1, after the reverse coal-excavation joint tunnel is constructed, anti-burst measures are taken for the reverse coal-excavation joint tunnel. The reverse coal-excavation joint tunnel is constructed along the coal seam roof and supported by anchor nets. The reverse coal-excavation joint tunnel has a construction section of 12 to 20 m2.

4. The reverse coal stripping method according to claim 1, characterized in that: In step S2, according to the coal seam gas conditions in the adjacent uncovered coal seam tunnels, the parameters of the reverse coal uncovering area of ​​the coal seam tunnel to be uncovered are inverted to predict the coal seam outburst hazard in the reverse coal uncovering area of ​​the coal seam tunnel to be uncovered.

5. The reverse coal stripping method according to claim 1, characterized in that: In the step S3, a plan for eliminating coal outbursts in the reverse coal-exposing area of ​​the roadway to be exposed is formulated by pre-extracting and eliminating coal outbursts in the layer-by-layer drilling area.

6. The reverse coal stripping method according to claim 1, characterized in that: In step S4, the construction length of the super-high top section of the tunnel is determined according to the thickness, inclination, mechanical properties and tunnel construction angle of the coal seam, and the super-high range is controlled within 2m; during the construction of the top section of the reverse coal-excavating tunnel, anchor mesh support is used.

7. The reverse coal stripping method according to claim 1, characterized in that: In step S4, the advance grouting reinforcement range is 100-120° of the designed tunnel vault, and the advance grouting holes are arranged in the coal seam 40 cm outside the U-shaped shed outline.

8. The reverse coal stripping method according to claim 7, characterized in that: In step S4, after all the advance grouting holes are constructed and casing is lowered, grouting is performed on the entire front section of the tunnel with a thickness of at least 30 mm; then grouting is performed on the drilled holes through the advance grouting casing.

9. The reverse coal stripping method according to claim 1, characterized in that: In step S5, the distance between the U-shaped sheds is 0.4-0.6m; during the erection of the U-shaped shed support, anchor rods are constructed on the top plate.

10. The reverse coal stripping method according to claim 1, characterized in that: In step S5, the tunnel is constructed to be 2m away from the coal seam, and the reverse coal stripping is completed. Grouting treatment is performed on the reverse coal stripping top coal section and the area 10m before and after, and observation points are set up.

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