A construction method applicable to coal seam tunnels with high ground stress outbursts

Abstract

This invention relates to the field of tunnel engineering technology, specifically providing a construction method suitable for tunnels in high-stress coal seams. The method divides the excavation face into four areas: upper bench, middle bench, lower bench, and invert zone, where anti-outburst work is carried out separately. Two anti-outburst operations are conducted at two stages, 5m and 2m vertical distance from the coal seam, facilitating effective coverage of the detection borehole length and improving the accuracy of anti-outburst verification. The upper bench is used to pre-expose the coal seam, effectively reducing the outburst risk in large-section tunnels. The middle bench, lower bench, and invert zone are excavated simultaneously, effectively solving the deformation control problem of the remaining large section under high stress. This fully addresses the engineering challenge of ensuring safe coal seam excavation and effectively controlling deformation under the contradictory coupling of high stress and outburst-prone coal seams.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering technology, and in particular to a construction method applicable to tunnels in coal seams with high ground stress outbursts. Background Technology

[0002] When traversing an outburst-prone coal seam, the transition from a high-strength rock stratum to a low-strength coal seam causes a sudden change in the rock and coal's resistance to coal and gas outbursts. The risk of coal and gas outbursts reaches its maximum the moment the coal seam is exposed. Therefore, addressing the safety issues during excavation of outburst-prone coal seams and reducing the risk of coal and gas outbursts through excavation methods is a key consideration in selecting construction methods for outburst-prone coal seam tunnels. Furthermore, deep, high-stress outburst-prone coal seams, due to their great depth, high stress levels, and the presence of weak interlayers, exacerbate the large deformations after tunnel excavation. Effectively controlling deformation is another crucial consideration in construction methods.

[0003] To reduce the risk of coal and gas outbursts in coal seams, a method of slow excavation with small cross sections should generally be adopted. However, for soft rock tunnels with high ground stress, a method of rapid excavation and support with simultaneous excavation of each cross section should be adopted to control deformation. Under the contradictory coupling conditions of high ground stress and coal seam outbursts, how to safely expose coal and excavate while effectively controlling deformation is a major engineering challenge in tunnel construction. Summary of the Invention

[0004] The purpose of this invention is to solve the problem that existing tunnel excavation methods from rock strata to exposed coal seams are difficult to excavate safely and effectively control deformation, and to provide a construction method suitable for high-stress outburst coal seam tunnels.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: Firstly, a construction method suitable for tunnels in coal seams with high ground stress and outbursts is provided, including: S1, the upper bench, middle bench, lower bench and invert arch area are excavated simultaneously to a distance of more than or equal to 5m from the top of the coal seam. Comprehensive anti-outburst work is carried out on the upper bench, middle bench, lower bench and invert arch area until the anti-outburst effect meets the preset requirements. The top surface of the inner rail is designed to be located on the lower bench. S2, middle bench, lower bench and invert arch area are suspended from tunneling. Upper bench continues to be tunneled forward to 2m from the vertical distance of the coal seam roof. Comprehensive anti-outburst work is carried out on the upper bench again until the anti-outburst effect meets the preset requirements. S3. Continue tunneling forward on the upper step until the roof of the coal seam is exposed, then carry out comprehensive anti-outburst work on the semi-coal and semi-rock tunneling face until the anti-outburst effect meets the preset requirements; S4. Continue tunneling up the bench to pass through the coal seam until the distance from the bottom of the coal seam is greater than or equal to 2m. S5, the middle bench, the lower bench and the invert arch area are excavated simultaneously until they pass through the coal seam; S6. After the initial support ring is formed, construct the invert arch lining and invert arch filling; S7. After the initial support deformation stabilizes, construct the arch wall lining and complete the excavation of the section crossing the coal seam.

[0006] The construction method described in this invention, applicable to tunnels in coal seams with high ground stress and outbursts, divides the excavation face into four areas: upper bench, middle bench, lower bench, and invert arch area. Outburst prevention work is carried out in each of these four areas separately. Two outburst prevention operations are conducted at two stages, 5m and 2m vertical distance from the coal seam, which facilitates the effective coverage of the detection boreholes, thereby improving the accuracy of outburst prevention verification. The upper bench is used to pre-expose the coal seam, effectively reducing the outburst risk in large-section tunnels. The middle bench, lower bench, and invert arch area are excavated simultaneously, effectively solving the deformation control problem of the remaining large section under high ground stress. This fully addresses the engineering challenge of ensuring safe coal seam excavation and effectively controlling deformation under the contradictory coupling of high ground stress and outburst-prone coal seams.

[0007] Preferably, step S2 also includes pre-construction pipe roof support.

[0008] Preferably, the pipe length of the advanced central pipe shed support is greater than or equal to 9m, the circumferential spacing is 30-40cm, and the longitudinal spacing is 5-6m.

[0009] Preferably, in step S3, after the pilot tunnel is opened on the upper bench to expose the coal seam, the remaining part of the upper bench is excavated to expose the coal seam.

[0010] Preferably, the width and height of the pilot tunnel are 2-3m.

[0011] Preferably, step S4 further includes pre-construction support, which includes large pipe roof support and small pipe protection. The pipes for the large pipe roof support are 12m long or longer, with a circumferential spacing of 30-40cm and a longitudinal spacing of 9-10m. The pipes for the small pipe protection are 4-5m long, with a circumferential spacing of 30-40cm and a longitudinal spacing of 2-3m.

[0012] Preferably, in step S4, the upper bench is excavated in segments, with each excavation length less than or equal to the spacing of one steel frame. A temporary invert is constructed as the upper bench is excavated, and the temporary invert includes steel supports with shotcrete applied to the steel supports. In step S5, the middle and lower benches are both excavated in segments, with each excavation length less than or equal to the spacing of three steel frames. The invert area is excavated in segments, with each excavation length less than or equal to 3 meters.

[0013] Preferably, the arch feet on both sides of the upper, middle and lower steps are equipped with locking anchor pipes.

[0014] Preferably, the comprehensive anti-outburst work of the working face in the middle step, lower step and invert arch area in step S1 is replaced by steps S2-S4.

[0015] Preferably, the initial support includes a first initial support and a second initial support from the outside to the inside, and the second initial support is constructed after the first initial support forms a ring.

[0016] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: The construction method described in this invention, applicable to tunnels in coal seams with high ground stress and outbursts, divides the excavation face into four areas: upper bench, middle bench, lower bench, and invert arch area. Outburst prevention work is carried out in each of these four areas separately. Two outburst prevention operations are conducted at two stages, 5m and 2m vertical distance from the coal seam, which facilitates the effective coverage of the detection boreholes, thereby improving the accuracy of outburst prevention verification. The upper bench is used to pre-expose the coal seam, effectively reducing the outburst risk in large-section tunnels. The middle bench, lower bench, and invert arch area are excavated simultaneously, effectively solving the deformation control problem of the remaining large section under high ground stress. This fully addresses the engineering challenge of ensuring safe coal seam excavation and effectively controlling deformation under the contradictory coupling of high ground stress and outburst-prone coal seams. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the cross-section after the completion of a construction method applicable to high-stress coal seam tunnels; Figure 2 This is a longitudinal cross-sectional schematic diagram of step S1 of a construction method applicable to coal seam tunnels with high ground stress outbursts. Figure 3 This is a longitudinal cross-sectional schematic diagram of step S2 of a construction method applicable to coal seam tunnels with high ground stress protrusion. Figure 4 This is a longitudinal profile diagram of step S3 of a construction method applicable to coal seam tunnels with high ground stress outbursts. Figure 5 This is a longitudinal cross-sectional schematic diagram of step S4 in a construction method applicable to coal seam tunnels with high ground stress outbursts. Figure 6 This is a longitudinal profile diagram of step S7 of a construction method applicable to coal seam tunnels with high ground stress outbursts.

[0018] Icons: 11-Initial support; 12-Invert lining; 13-Invert filling; 14-Arch wall lining; 1-Upper bench; 2-Middle bench; 3-Lower bench; 4-Invert area; 5-Coal seam; 6-Guide tunnel; 7-Temporary invert; 8-Anchor pipe; 9-Middle pipe roof support. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings.

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] Unless otherwise specified, the use of terms such as "upper," "lower," "left," "right," "center," "inner," and "outer" to indicate orientation or positional relationships in the description of specific embodiments of the present invention is based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationship in which the product / equipment / device is typically placed during use. These terms are merely for the purpose of facilitating the description of the present invention or simplifying the description in specific embodiments, enabling those skilled in the art to quickly understand the solution, and do not indicate or imply that a particular device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, they should not be construed as limitations on the present invention.

[0022] Furthermore, the use of terms such as "horizontal," "vertical," "suspended," and "parallel" does not imply that the corresponding device / component / element must be absolutely horizontal, vertical, suspended, or parallel, but rather that it can be slightly tilted or have a deviation. For example, "horizontal" merely means that its direction is more horizontal relative to "vertical," not that the structure must be completely horizontal, but can be slightly tilted. Alternatively, it can be simplified to mean that the corresponding device / component / element, when set in a "horizontal," "vertical," "suspended," or "parallel" direction, can have an error / deviation of ±10% relative to the corresponding direction, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, and more preferably within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its function in the present invention.

[0023] Furthermore, the use of terms such as "first," "second," and "third" in terminology is merely for distinguishing descriptions of identical or similar components and should not be interpreted as emphasizing or implying the relative importance of a particular component.

[0024] Furthermore, in the description of the embodiments of the present invention, "several", "more than", and "a number of" represent at least two. The number can be any number, such as two, three, four, five, six, seven, eight, or nine, and can even exceed nine.

[0025] Furthermore, in the description of the technical solution of this invention, unless otherwise explicitly specified / limited / restricted, the terms "set up," "install," "connect," "link," "provided with," "laid out," and "arranged" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to common connection methods in the art, such as welding, riveting, bolting, and threaded connections. Such connections can be mechanical, electrical, or communication connections; they can be direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components.

[0026] Example 1 like Figures 1-6 As shown, the construction method for tunnels in coal seams with high ground stress outbursts, as employed in this invention, includes: S1, upper bench 1, middle bench 2, lower bench 3 and invert arch area 4 are excavated simultaneously to a distance of more than or equal to 5m from the top of the coal seam. Comprehensive anti-outburst work is carried out on upper bench 1, middle bench 2, lower bench 3 and invert arch area 4 until the anti-outburst effect meets the preset requirements. The top surface of the inner rail is designed to be located on lower bench 3. S2, middle bench 2, lower bench 3 and invert arch area 4 are suspended from tunneling. Upper bench 1 continues to tunnel forward to a distance of 2m from the vertical distance of the coal seam roof. Comprehensive anti-outburst work is carried out on upper bench 1 again until the anti-outburst effect meets the preset requirements. S3. After advancing forward from step 1 to expose the roof of coal seam 5, carry out comprehensive anti-outburst work on the semi-coal and semi-rock tunneling face until the anti-outburst effect meets the preset requirements. S4. Continue tunneling up step 1 through coal seam 5 to a point where the distance from the bottom plate of coal seam 5 is greater than or equal to 2m. S5, middle bench 2, lower bench 3 and invert arch area 4 were excavated simultaneously until they passed through coal seam 5; S6. After the initial support 11 is formed into a ring, construct the invert arch lining 12 and the invert arch filling 13. S7. After the initial support 11 has stabilized, construct the arch wall lining 14 to complete the excavation of the section crossing the coal seam.

[0027] Specifically, the working face is divided into four areas: upper bench 1, middle bench 2, lower bench 3, and invert arch area 4. The inner rail top surface is designed to be located at lower bench 3. Upper bench 1, middle bench 2, lower bench 3, and invert arch area 4 are excavated simultaneously to a point where the vertical distance from the coal seam roof is greater than or equal to 5m. Figure 2As shown, comprehensive outburst prevention work was carried out on the working faces of the four areas until the outburst prevention effect met the preset requirements. The risk of coal and gas outbursts in the upper, middle, lower, left, and right ranges of the excavation face was checked. If all indicators met the requirements, the excavation could proceed. A 5m safety zone should always be maintained in front of the working face and around the excavation outline. The safety zone refers to the area where there is no outburst risk, as evaluated by the drill cuttings gas desorption index method. The cumulative gas desorption amount was determined by the drill cuttings gas desorption index method. K 1 and differential pressure reading ∆ h The risk assessment is conducted using a 2-value method, and various existing technologies can be used for gas outburst prevention measures. Simultaneous excavation of the upper bench 1, middle bench 2, lower bench 3, and invert arch zone 4 can be carried out using the conventional bench method found in existing technologies.

[0028] Excavation is suspended in the middle bench 2, lower bench 3, and invert arch area 4. Excavation continues in the upper bench 1, carried out under the protection of the advanced central pipe roof support 9. The pipes in the advanced central pipe roof support 9 are 9m long or longer, with a circumferential spacing of 30-40cm and a longitudinal spacing of 5-6m. This prevents collapse and roof fall due to large deformation and is more suitable for high ground stress environments. For example, if the advanced central pipe roof support 9 uses Φ89 pipes, each 9m long, with a circumferential spacing of 40cm and a longitudinal spacing of 6m. Excavation continues until a distance of 2m from the coal seam roof is reached. Figure 3 As shown, comprehensive anti-outburst work is carried out again on the upper step 1 until the anti-outburst effect meets the preset requirements.

[0029] After the upper bench 1 exposes the roof of coal seam 5, comprehensive anti-outburst work is carried out in the semi-coal, semi-rock tunneling face until the anti-outburst effect meets the preset requirements. If the upper bench 1 cannot expose the roof of coal seam 5 in one full section (e.g., when the coal seam intersects the cross section obliquely, the distance of one excavation cannot completely expose the roof of coal seam 5), a pilot tunnel 6 can be opened on the upper bench to expose the roof of coal seam 5. Figure 4 Then proceed with the excavation of the remaining part of the upper step 1. The width and height of the pilot tunnel 6 are respectively 2-3m.

[0030] The tunneling continues on step 1, with the excavation process carried out under the protection of advanced support. Advanced support includes large pipe roof support and small pipe protection, protecting the arch area and the coal seam area along the sidewalls. This prevents arch collapse and localized coal seam slippage from further triggering larger collapses, roof falls, or coal and gas outbursts. It is more suitable for high ground stress environments and coal seam coupling conditions. The pipe length of the large pipe roof support is greater than or equal to 12m, with a circumferential spacing of 30-40cm and a longitudinal spacing of 9-10m. The pipe length of the small pipe protection is 4-5m, with a circumferential spacing of 30-40cm and a longitudinal spacing of 2-3m. For example, if Φ108 large pipe roof + Φ42 small pipes are used, the large pipe roof has a single length of 12m, a circumferential spacing of 40cm, and a longitudinal spacing of 9m; the small pipe has a single length of 4.5m, a circumferential spacing of 40cm, and a longitudinal spacing of 2.4m. The distance from the excavation outline to the bottom plate of coal seam 5 should not be less than 2m. Figure 5 As shown.

[0031] The upper step 1 is excavated in segments, with each excavation length less than or equal to the spacing of one steel frame. As the upper step 1 is excavated, temporary invert arches 7 and anchor pipes 8 at the arch feet on both sides are constructed. The specific quantity and size are set according to actual needs. The temporary invert arches 7 can temporarily form a ring to ensure that the upper step 1 can be excavated slowly while effectively controlling deformation and preventing settlement. The temporary invert arches 7 include steel supports, and shotcrete is sprayed on the steel supports.

[0032] The middle bench 2, lower bench 3, and invert arch area 4 were excavated simultaneously until they passed through the coal seam 5. During the excavation, the middle bench 2 and lower bench 3 were excavated in sections, and anchor pipes 8 were installed at the arch feet on both sides to control deformation and settlement. The length of each excavation was less than or equal to the spacing of 3 steel frames. The invert arch area 4 was excavated in sections, with the length of each excavation less than or equal to 3m. The large cross-section formed by the middle bench 2, lower bench 3, and invert arch area 4 was excavated and supported quickly to effectively control deformation.

[0033] After the entire cross-section passes through coal seam 5, initial support 11 is constructed. After the initial support 11 forms a ring, invert arch lining 12 and invert arch filling 13 are constructed. After the initial support 11 has stabilized, arch wall lining 14 is constructed, completing the excavation of the section crossing the coal seam. Figure 6 As shown. Under the conditions of high ground stress and coal seam coupling, the initial support 11 is a double-layer support. If both the first and second initial supports are made of HW200 steel, the second initial support is erected after the first initial support forms a ring. The deformation stability of the initial support 11 can be defined as a daily deformation of less than 2 mm / day, or a significant decrease in the deformation rate and a tendency to converge.

[0034] In some optional embodiments, the comprehensive anti-outburst work of the working face of the middle step 2, lower step 3 and inverted arch area 4 in step S1 is replaced by being carried out in steps S2-S4.

[0035] The construction method described in this invention, applicable to tunnels in coal seams with high ground stress and outbursts, divides the excavation face into four areas: upper bench 1, middle bench 2, lower bench 3, and invert arch area 4. Outburst prevention work is carried out in each area separately. Two outburst prevention operations are conducted at two stages, 5m and 2m vertical distance from the coal seam, which facilitates the effective coverage of the detection boreholes, thereby improving the accuracy of the outburst prevention effect verification. The upper bench is used to pre-expose the coal seam, effectively reducing the outburst risk of coal seam exposure in large-section tunnels. The middle bench 2, lower bench 3, and invert arch area 4 are excavated simultaneously, effectively solving the deformation control problem of the remaining large section under high ground stress. This fully solves the engineering problem of ensuring safe coal seam exposure and excavation while effectively controlling deformation under the contradictory coupling of high ground stress and outburst coal seams.

[0036] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A construction method suitable for tunnels in coal seams with high ground stress outbursts, characterized in that, include: S1, the upper step (1), middle step (2), lower step (3) and invert arch area (4) are excavated simultaneously to a distance of more than or equal to 5m from the top of the coal seam. Comprehensive anti-outburst work is carried out on the upper step (1), middle step (2), lower step (3) and invert arch area (4) until the anti-outburst effect meets the preset requirements. The top surface of the inner rail is located on the lower step (3). S2, middle bench (2), lower bench (3) and invert arch area (4) are suspended from tunneling. Upper bench (1) continues to tunnel forward to a distance of 2m from the top of the coal seam. Comprehensive anti-outburst work is carried out on upper bench (1) again until the anti-outburst effect meets the preset requirements. S3. After advancing forward on the upper step (1) until the top of the coal seam (5) is exposed, carry out comprehensive anti-outburst work on the semi-coal and semi-rock tunneling face until the anti-outburst effect meets the preset requirements. S4. Continue tunneling up the step (1) through the coal seam (5) to a point where the distance from the bottom plate of the coal seam (5) is greater than or equal to 2m; S5, the middle bench (2), the lower bench (3) and the invert arch area (4) are excavated simultaneously until they pass through the coal seam (5); S6. After the initial support (11) is formed into a ring, construct the invert arch lining (12) and invert arch filling (13); S7. After the initial support (11) has stabilized, construct the arch wall lining (14) and complete the excavation of the section crossing the coal seam. In step S4, it also includes construction advance support, which includes large pipe roof support and small pipe protection. The pipe length of the large pipe roof support is greater than or equal to 12m, the circumferential spacing is 30-40cm, and the longitudinal spacing is 9-10m. The pipe length of the small pipe protection is 4-5m, the circumferential spacing is 30-40cm, and the longitudinal spacing is 2-3m. The upper step (1) adopts segmented excavation, and the length of each excavation is less than or equal to the spacing of 1 steel frame. As the upper step (1) is excavated, a temporary invert arch (7) is constructed. The temporary invert arch (7) includes steel support, and shotcrete is sprayed on the steel support. In step S5, the middle step (2) and the lower step (3) are both excavated in segments, and the length of each excavation is less than or equal to the spacing of 3 steel frames. The invert arch area (4) adopts segmented excavation, and the length of each excavation is less than or equal to 3m. As the upper step (1), middle step (2) and lower step (3) are excavated, locking foot anchor pipes (8) are set at the arch feet on both sides respectively.

2. The construction method for tunnels in coal seams with high ground stress outbursts according to claim 1, characterized in that, Step S2 also includes pre-construction pipe roof support (9).

3. The construction method for tunnels in coal seams with high ground stress outbursts according to claim 2, characterized in that, The pipe length of the advanced central pipe shed support (9) is greater than or equal to 9m, the circumferential spacing is 30-40cm, and the longitudinal spacing is 5-6m.

4. The construction method for tunnels in coal seams with high ground stress outbursts according to claim 1, characterized in that, In step S3, after the guide tunnel (6) is opened on the upper bench (1) to expose the coal seam (5), the remaining part of the upper bench (1) is then excavated to expose the coal seam (5).

5. A construction method for tunnels in coal seams with high ground stress outbursts according to claim 4, characterized in that, The width and height of the guide tunnel (6) are 2-3m respectively.

6. A construction method for tunnels in high-stress coal seams according to any one of claims 1-5, characterized in that, The comprehensive anti-outburst work of the working face of the middle step (2), lower step (3) and inverted arch area (4) in step S1 is replaced by the work in steps S2-S4.

7. A construction method for tunnels in coal seams with high ground stress outbursts according to any one of claims 1-5, characterized in that, The initial support (11) includes the first initial support and the second initial support from the outside to the inside. The second initial support is constructed after the first initial support is formed into a ring.

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