Super-thick coal seam narrow coal pillar double-roadway tunneling and entry retaining stable control method

Abstract

The invention discloses an extra-thick coal seam narrow coal pillar double-roadway tunneling and entry retaining stability control method. The method comprises the following steps that S1, the roadway position of a first mining working face is determined; tunneling is conducted from the two sides respectively, a first mining working face air return gate way is excavated on one side in a single-roadway tunneling mode, and an asymmetric first mining working face haulage gate way and a first mining working face air inlet gate way are excavated on the other side in a narrow coal pillar retaining double-roadway tunneling mode at the same time; s2, tunneling of a gate way in the first mining working face; s3, in the stoping process of the first mining working face, top cutting pressure relief is conducted on a top plate on an advanced working face of a haulage roadway of the first mining working face, and grouting reinforcement is conducted on a coal pillar plate and a slope transition section coal body on a lagging working face of an air inlet roadway of the first mining working face; and S4, tunneling and stoping of the continuous working face. The lateral confining pressure of the narrow coal pillar is improved through asymmetric arrangement of the two roadways, a structure with the weak upper portion and the strong lower portion is formed to transfer a preferential deformation position to adapt to top plate movement, the coal pillar anchoring environment is optimized, and ultra-thick coal seam narrow coal pillar double-roadway tunneling and entry retaining stable control is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of coal mining and tunnel support, and in particular relates to a method for controlling double tunneling and tunnel retention with narrow coal pillars in an extremely thick coal seam. Background Art

[0002] The layout of working face mining tunnels mainly includes single tunnel excavation, double tunnel excavation and multi-tunnel excavation, among which single tunnel and double tunnel excavation are the most widely used. Double tunnel excavation can realize the sequential mining of adjacent working faces and alleviate the tension between mining and excavation in the mine. However, based on the consideration of stable control of mining tunnels, a 30m-50m section protection coal pillar is traditionally left between the double tunnels of extra-thick coal seams (extra-thick coal seams refer to coal seams with a thickness of more than 8m). However, such partial coal pillars are often difficult to recover, which directly leads to a large waste of coal resources, and the coal pillars are prone to form high stress concentration, increasing the risk of rock burst. In the single tunnel excavation layout of extra-thick coal seams, although the adjacent working face mining tunnels can adopt the method of leaving 6-8m narrow coal pillars to excavate along the goaf to reduce coal pillar loss and stress concentration, the coal pillars are easily affected by the overburden movement in the goaf and cause large deformation. Therefore, tunnel excavation is generally delayed for 6-10 months until the overburden movement is basically stable. This not only directly leads to the continuous tension between mining and excavation, but also the effect of controlling the deformation of coal pillars is poor. If it is possible to achieve double-tunnel excavation of narrow coal pillars in extra-thick coal seams and retain one of the tunnels to continue serving the subsequent working face, it will be very beneficial for working face mining succession, coal pillar recovery and prevention and control of rock burst.

[0003] Narrow coal pillars in extra-thick coal seams often deform greatly due to the movement of the upper rock strata, so stable control of narrow coal pillars is the key to achieving double-lane excavation and lane retention. Since the lateral confining pressure is positively correlated with the strength of the coal pillars, in the traditional double-lane arrangement and excavation along the coal seam floor, the sides of the coal pillars in the two lanes are symmetrical free surfaces located at the bottom of the coal pillars. Under the current support system conditions, it is difficult to establish an effective mechanical connection between the two sides of the coal pillars. In addition, due to the small width of the narrow coal pillars, there is no condition for the application of anchor cables. The coal pillars are only supported and reinforced by anchor rods, resulting in serious lack of lateral confining pressure. In addition, the upper part of the coal pillars in extra-thick coal seams is reinforced by the side limit of the top coal, and the coal pillars form a "strong on top and weak on the bottom" structure. When the upper rock strata move, the sides of the coal pillars in the lanes are deformed first, which makes it difficult to use double lanes with narrow coal pillars. Summary of the invention

[0004] The present invention proposes a method for stable control of double-tunnel excavation and retained tunnels in extremely thick coal seams with narrow coal pillars, which can not only ensure normal succession of mining at the working face of the thick coal seam and improve the coal recovery rate, but also solve the problem of difficult control of large deformation of double-tunnel excavation and retained tunnels in extremely thick coal seams with narrow coal pillars.

[0005] To this end, the technical solution adopted by the present invention is: a method for controlling double-lane excavation and lane retention stability in a narrow coal pillar in an extra-thick coal seam, comprising the following steps:

[0006] S1: The tunnel position of the first mining face is determined; excavation starts from both sides, with the return air tunnel of the first mining face being excavated by single tunnel excavation on one side, and the asymmetric transport tunnel and air intake tunnel of the first mining face being excavated by double tunnel excavation with narrow coal pillars on the other side. The transport tunnel and air intake tunnel of the first mining face are staggered up and down, and the air intake tunnel of the first mining face is excavated along the bottom plate of the coal seam, and the transport tunnel of the first mining face is set at the top;

[0007] S2: Excavation of the tunnel in the first mining face; a connecting tunnel is excavated between the transport tunnel of the first mining face and the air intake tunnel of the first mining face, and there is a slope transition section between the transport tunnel of the first mining face and the floor of the face; anchor rods are used to support the coal pillars of the transport tunnel of the first mining face to weaken the strength of the upper part of the coal pillars; anchor rods, anchor cables and metal mesh are used to support the coal pillars of the air intake tunnel of the first mining face, and the length of the anchor cables is between the width of the coal pillar and the sum of the width of the coal pillar and the width of the transport tunnel of the first mining face to strengthen the strength of the lower part of the coal pillar; anchor rods, anchor cables and metal mesh are used to support the roof of the air intake tunnel of the first mining face;

[0008] S3: Mining of the first mining face; during the mining process of the first mining face, the top plate is cut and pressure is relieved on the leading working surface of the transport lane of the first mining face, and grouting is performed on the lagging working surface of the air intake lane of the first mining face to reinforce the coal pillar plate and the coal body in the slope transition section;

[0009] S4: Excavation and mining of the subsequent working face; repeat steps S1, S2 and S3, wherein the return air lane of the subsequent working face is the air intake level lane of the first mining working face.

[0010] As a preferred embodiment of the above scheme, in step S1, the horizontal distance L between the first mining working face transport tunnel and the first mining working face air intake tunnel is calculated by the following formula:

[0011]

[0012] Where S is the mining height, in m; H is the buried depth of the coal seam; ∑h is the thickness of the rock layer in the cross-fall zone, in m; γ is the average bulk density of the rock layer above the coal seam, in m; γ1 is the bulk density of the rock layer in the cross-fall zone, in m; γ2 is the bulk density of the coal body, in m; θ is the angle between the slope transition section and the bottom plate of the coal seam, in °; a is the width of the transport lane, in m; C is the cohesion of the coal body; is the friction angle inside the coal body, unit is m; f is the friction coefficient between the coal seam and the roof and floor.

[0013] It is further preferred that the vertical distance between the transport tunnel of the first mining working face and the air intake tunnel of the first mining working face is not less than the height of the air intake tunnel of the first mining working face, and the scraper conveyor starts from the transport tunnel of the first mining working face and transitions to the coal seam bottom plate with each scraper section at 3°, 6°, 9°, 12°, and at least one section at 15°, 12°, 9°, 6°, 3°, forming a slope transition section of coal body under the scraper conveyor.

[0014] Further optimization is that the transport tunnel of the first mining working face lags behind the air intake tunnel of the first mining working face by 30-50m, the angle between the connecting tunnel and the tunnel axis is between 30° and 60°, and the connecting tunnel opens on the transport tunnel side of the first mining working face close to the first mining working face opening, and opens on the air intake tunnel side of the first mining working face away from the first mining working face opening.

[0015] It is further preferred that in step S3, during the mining process of the first mining working face, the top plate is cut and pressure relieved along the advancement direction of the first mining working face at 100±5m from the advance working face of the transport level tunnel of the first mining working face, the bottom of the top cutting line hole of the first mining working face is close to the goaf side, the angle between the top cutting line of the first mining working face and the vertical direction is 0-15°, and the top cutting height is more than 1 / 2 of the basic roof thickness.

[0016] Beneficial effects of the present invention:

[0017] 1) This method realizes the asymmetric arrangement of double tunnels in the high and low layers of the coal seam. The coal body in the slope transition section below the transport tunnel of the high-level first mining working face can provide lateral confining pressure for the coal pillar of the air intake tunnel of the low-level first mining working face, so that the lower part of the narrow coal pillar is in a three-dimensional stress state. At the same time, grouting reinforcement into the coal body of the slope transition section can provide a stable anchoring foundation for the anchor cable, thereby strengthening the lower part of the coal pillar. At the same time, the coal pillar of the transport tunnel of the high-level first mining working face is only reinforced with anchor rods. Affected by the movement of the upper rock formation, the upper part of the coal pillar is deformed and unloaded first to protect the stability of the lower part of the coal pillar. The top of the transport tunnel of the high-level first mining working face is cut to unload pressure and reduce the load above the coal pillar, thereby ensuring that the air intake tunnel of the low-level first mining working face is retained and continued to be used as the return tunnel of the subsequent working face.

[0018] 2) This method allows narrow coal pillars to be left adjacent to the working faces of extra-thick coal seams, greatly reducing the waste of coal resources. At the same time, the narrow coal pillars are in the area of ​​reduced support pressure, which is not easy to form high stress concentration and reduce the risk of coal pillar impact ground pressure. The simultaneous excavation of two tunnels is conducive to gas emission. After the first mining face is mined, the first mining face air intake tunnel is used as the subsequent working face return tunnel, which can cancel the 6-10 month lag period during single tunnel excavation, realize sequential mining of the working faces, and ensure normal mining and excavation succession in the mine.

[0019] 3) Compared with the traditional arrangement of tunnels along the bottom plate of the coal seam, the thickness of the top coal in the high-level transport tunnel of this method is reduced, which can reduce the collapse rate of the top cutting drilling hole and improve work efficiency. The whole method is simple and easy to implement and has good economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a top view of the narrow coal pillar double tunnel excavation of the first mining face and the subsequent working face (the slender arrow in the figure indicates the tunnel excavation direction, and the short and thick arrow indicates the mining direction).

[0021] Figure 2 This is the cross-section diagram of the double-tunnel excavation of the narrow coal pillar in the first mining face.

[0022] Figure 3 This is the cross-sectional diagram of the narrow coal pillar double tunnel excavation of the first mining face and the subsequent working face.

[0023] Figure 4 This is a schematic diagram of the coal pillar support in a double tunnel with narrow coal pillars.

[0024] Explanation of the accompanying numbers: 1-first mining working face; 2-subsequent working face; 3-anchor rod; 4-anchor cable; 11-return air tunnel of the first mining working face; 12-transport tunnel of the first mining working face; 13-air intake tunnel of the first mining working face; 14-connecting tunnel; 15-slope transition section; 16-top cutting line of the first mining working face; 21-return air tunnel of the subsequent working face; 22-transport tunnel of the subsequent working face; 23-air intake tunnel of the subsequent working face. DETAILED DESCRIPTION

[0025] The present invention will be further described below by way of embodiments and in conjunction with the accompanying drawings:

[0026] like Figure 1-4 As shown, a method for double-lane excavation and lane retention stability control in a particularly thick coal seam with narrow coal pillars mainly comprises the following steps:

[0027] Step 1: Determine the location of the tunnel of the first mining face 1. Figure 1 As shown, excavation 1 is started from both sides respectively, one side excavates the return air tunnel 11 of the first mining face by single tunnel excavation, and the other side excavates the asymmetric first mining face transport tunnel 12 and the first mining face air intake tunnel 13 by double tunnel excavation with narrow coal pillars, and the first mining face transport tunnel 12 and the first mining face air intake tunnel 13 are staggered up and down, the first mining face air intake tunnel 13 is excavated along the bottom plate of the coal seam, and the first mining face transport tunnel 12 is arranged on the top.

[0028] Among them Figure 2 As shown, the horizontal distance L between the first mining face transport tunnel 12 and the first mining face air intake tunnel 13 is calculated by the following formula:

[0029]

[0030] Where S is the mining height, in m; H is the buried depth of the coal seam; ∑h is the thickness of the rock layer in the cross-fall zone, in m; γ is the average bulk density of the rock layer above the coal seam, in m; γ1 is the bulk density of the rock layer in the cross-fall zone, in m; γ2 is the bulk density of the coal body, in m; θ is the angle between the slope transition section and the bottom plate of the coal seam, in °; a is the width of the transport lane, in m; C is the cohesion of the coal body; is the friction angle inside the coal body, unit is m; f is the friction coefficient between the coal seam and the roof and floor.

[0031] The vertical distance between the transport tunnel 12 of the first mining working face and the air intake tunnel 13 of the first mining working face shall not be less than the height of the air intake tunnel 13 of the first mining working face.

[0032] Step 2: Excavation of the tunnel in the first mining face. A connecting tunnel 14 is excavated between the first mining face transport tunnel 12 and the first mining face air intake tunnel 13, and there is a slope transition section 15 between the first mining face transport tunnel 12 and the working face floor.

[0033] Specifically: Figure 1 As shown, during the double-tunnel excavation process, the first mining face transport tunnel 12 lags behind the first mining face air intake tunnel 13 in excavation, and the lag distance is 30-50m. An inclined connecting tunnel 14 is excavated every 100-200m between the first mining face transport tunnel 12 and the first mining face air intake tunnel 13. The angle between the connecting tunnel and the tunnel axis is 30°~60°. The connecting tunnel opens on the first mining face transport tunnel side close to the first mining face for cutting, and opens on the first mining face air intake tunnel side away from the first mining face for cutting.

[0034] like Figure 2 As shown, the first mining working face transport tunnel 12 and the first mining working face air intake tunnel 13 are connected to form the first mining working face, and the scraper conveyor of the working face starts from the first mining working face transport tunnel 12 and transitions to the coal seam bottom plate in the manner of each scraper section 3°, 6°, 9°, 12°, and at least one section 15°, 12°, 9°, 6°, 3°, that is, there are multiple sections of 15°, and a slope transition section 15 coal body is formed under the scraper conveyor.

[0035] like Figure 4 As shown, the coal pillars of the transport lane of the first mining face are supported by anchor rods 3; the coal pillars of the air intake lane of the first mining face are supported by anchor rods 3, anchor cables 4 and metal mesh, and the length of the anchor cables is between the width of the coal pillar and the sum of the width of the coal pillar and the width of the transport lane of the first mining face. The roof of the air intake lane of the first mining face is supported by anchor rods 3, anchor cables 4 and metal mesh.

[0036] Step 3: Mining of the first mining face. During the mining of the first mining face, the top plate is cut and pressure is relieved on the leading working surface of the transport lane of the first mining face, and grouting is performed on the lagging working surface of the air intake lane of the first mining face to reinforce the coal pillar plate and the coal body in the slope transition section.

[0037] Specifically, the roof is cut and pressure-relieved at 100m±5m ahead of the first mining face in the transport lane along the direction of the first mining face. The bottom of the first mining face top cutting line hole is close to the goaf side. The angle between the first mining face top cutting line 16 and the vertical direction is 0-15°, and the top cutting height is more than 1 / 2 of the basic roof thickness. Grouting reinforcement is carried out on the coal pillar plate and the coal body in the slope transition section at 100m-200m behind the first mining face in the air inlet lane.

[0038] Step 4: Excavation and mining of the subsequent working face 2; after completing the mining of the first mining working face, repeat the first, second and third steps to carry out tunnel excavation and coal mining on the subsequent working face, among which the air intake level tunnel of the first mining working face continues to be used as the return air level tunnel 21 of the subsequent working face, and the transport level tunnel 22 and the air intake level tunnel 23 of the subsequent working face need to be excavated according to the above steps.

Claims

1. A method for controlling double-lane excavation and lane retention stability in a narrow coal pillar in an extra-thick coal seam, characterized in that: The steps include: S1: The tunnel position of the first mining face is determined; excavation starts from both sides, with the return air tunnel of the first mining face being excavated by single tunnel excavation on one side, and the asymmetric transport tunnel and air intake tunnel of the first mining face being excavated by double tunnel excavation with narrow coal pillars on the other side. The transport tunnel and air intake tunnel of the first mining face are staggered up and down, and the air intake tunnel of the first mining face is excavated along the bottom plate of the coal seam, and the transport tunnel of the first mining face is set at the top; S2: Excavation of the tunnel in the first mining face; a connecting tunnel is excavated between the transport tunnel of the first mining face and the air intake tunnel of the first mining face, and there is a slope transition section between the transport tunnel of the first mining face and the floor of the face; anchor rods are used to support the coal pillars of the transport tunnel of the first mining face; anchor rods, anchor cables and metal mesh are used to support the coal pillars of the air intake tunnel of the first mining face, and the length of the anchor cable is between the width of the coal pillar and the sum of the width of the coal pillar and the width of the transport tunnel of the first mining face; anchor rods, anchor cables and metal mesh are used to support the roof of the air intake tunnel of the first mining face; S3: Mining of the first mining face; during the mining process of the first mining face, the top plate is cut and pressure is relieved on the leading working surface of the transport lane of the first mining face, and grouting is performed on the lagging working surface of the air intake lane of the first mining face to reinforce the coal pillar plate and the coal body in the slope transition section; S4: Excavation and mining of the subsequent working face; repeat steps S1, S2 and S3, wherein the return air lane of the subsequent working face is the air intake level lane of the first mining working face.

2. The method for double-lane excavation and lane retention stability control in ultra-thick coal seam with narrow coal pillars according to claim 1, characterized in that: In step S1, the horizontal distance L between the first mining face transport tunnel and the first mining face air intake tunnel is calculated by the following formula: Where S is the mining height, in m; H is the buried depth of the coal seam; ∑h is the thickness of the rock layer in the cross-fall zone, in m; γ is the average bulk density of the rock layer above the coal seam, in m; γ1 is the bulk density of the rock layer in the cross-fall zone, in m; γ2 is the bulk density of the coal body, in m; θ is the angle between the slope transition section and the bottom plate of the coal seam, in °; a is the width of the transport lane, in m; C is the cohesion of the coal body; is the friction angle inside the coal body, unit is m; f is the friction coefficient between the coal seam and the roof and floor.

3. The method for double-lane excavation and lane retention stability control of narrow coal pillars in extra-thick coal seams according to claim 1 is characterized by: The vertical distance between the transport tunnel of the first mining working face and the air intake tunnel of the first mining working face shall not be less than the height of the air intake tunnel of the first mining working face. The scraper conveyor starts from the transport tunnel of the first mining working face and transitions to the coal seam bottom plate with each scraper section at 3°, 6°, 9°, 12°, and at least one section at 15°, 12°, 9°, 6°, and 3°. A slope transition section of coal body is formed under the scraper conveyor.

4. The method for double-lane excavation and lane retention stability control in ultra-thick coal seam with narrow coal pillars according to claim 1, characterized in that: The transport tunnel of the first mining working face lags behind the air intake tunnel of the first mining working face by 30-50m. The angle between the connecting tunnel and the tunnel axis is between 30° and 60°. The connecting tunnel opens on the transport tunnel side of the first mining working face and is close to the cutting eye of the first mining working face, and opens on the air intake tunnel side of the first mining working face and is far away from the cutting eye of the first mining working face.

5. The method for double-lane excavation and lane retention stability control in ultra-thick coal seam with narrow coal pillars according to claim 1, characterized in that: In step S3, during the mining process of the first mining working face, the top plate is cut and pressure relieved along the advancement direction of the first mining working face at 100±5m from the advance working face of the transport level tunnel of the first mining working face. The bottom of the top cutting line of the first mining working face is close to the goaf side, the angle between the top cutting line of the first mining working face and the vertical direction is 0-15°, and the top cutting height is more than 1 / 2 of the basic roof thickness.

Images