A double-trapezoid support wire saw cutting pressure relief and outburst elimination method for coal-passing tunnels

Abstract

The present invention discloses a double-trapezoidal support wire saw cutting pressure relief and outburst elimination method for coal-crossing tunnels, belonging to the technical field of coal seam pressure relief and outburst elimination in coal-crossing tunnels. It includes: planning the cross-section of the large-section coal uncovering tunnel face into a first-level trapezoidal area and a second-level trapezoidal area, and using the trapezoidal platform between the planned second-level trapezoidal area and the coal seam as the support structure for tunnel coal uncovering pressure relief; according to the occurrence of the coal seam in front of the tunnel face and the planning of the large-section coal uncovering tunnel face; based on the planning of the large-section coal uncovering tunnel face and the drilling operation conditions, the reverse cutting method and the sleeve cutting method are used to continuously cut the middle part of the coal seam and the rock mass of the support structure. The present invention uses a double-trapezoidal support structure to achieve directional pressure relief, permeability enhancement and strengthening, efficient gas emission and coordinated control of in-situ stress in the tunnel coal seam, and reserves a free face for subsequent tunnel blasting construction, effectively solving the problems of high cost, low efficiency and insufficient safety in the conventional measures for outburst prevention in coal uncovering at the existing tunnel face.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal seam pressure relief and outburst elimination for coal-crossing tunnels, and particularly relates to a double-trapezoidal support wire saw cutting pressure relief and outburst elimination method for coal-crossing tunnels. Background Technique

[0002] In coal-bearing strata, due to the softness of the coal body structure and insufficient self-stabilization ability, and the dual influence of in-situ stress and gas pressure, the construction process of large-section tunnels is extremely prone to face collapses and coal and gas outburst accidents.

[0003] Currently, the conventional measures for outburst prevention during face coal uncovering include measures such as pre-draining gas, drilling drainage holes, reducing gas pressure, and supporting while excavating to release in-situ stress. However, these measures have problems such as high costs, low efficiency, and insufficient safety.

[0004] The information disclosed in this background art section is only intended to enhance the overall understanding of the present invention and should not be regarded as an admission or any form of implication that this information constitutes prior art already known to those of ordinary skill in the art. Summary of the Invention

[0005] In order to solve the technical problems of high costs, low efficiency, and insufficient safety existing in the conventional measures for outburst prevention during face coal uncovering in the prior art, a double-trapezoidal support wire saw cutting pressure relief and outburst elimination method for coal-crossing tunnels is provided.

[0006] The present invention provides a double-trapezoidal support wire saw cutting pressure relief and outburst elimination method for coal-crossing tunnels, including the following steps:

[0007] First, divide the face of the large-section coal-uncovering tunnel into two first trapezoidal areas with different sizes in the cross-section, and further divide a smaller second trapezoidal area from the two first trapezoidal areas. Use the trapezoidal prism between the planned second trapezoidal area and the coal seam as the support structure for tunnel coal-uncovering pressure relief;

[0008] Then, based on the occurrence of the coal seam in front of the face and the face planning of the large-section coal-uncovering tunnel, carry out precise construction positioning and drilling operations;

[0009] Finally, based on the face planning and drilling operation conditions of the large-section coal-uncovering tunnel, use a diamond wire saw to continuously cut the middle part of the coal seam and the rock mass of the support structure by the reverse cutting method and the nested cutting method to complete the permeability enhancement and pressure relief of the coal seam.

[0010] In some embodiments, dividing the face of the large-section coal-uncovering tunnel into two first trapezoidal areas with different sizes in the cross-section, and further dividing a smaller second trapezoidal area from the two first trapezoidal areas. Use the trapezoidal prism between the planned face and the coal seam as the support structure for tunnel coal-uncovering pressure relief, including:

[0011] The heading face of the large-section coal-uncovering tunnel is planned into two first-level trapezoidal areas with different sizes and stacked vertically in the cross-section. The two first-level trapezoidal areas are divided into multiple sub-blocks. The multiple sub-blocks include two second-level trapezoidal areas that are relatively smaller than the first-level trapezoidal areas. The trapezoidal prism between the planned second-level trapezoidal area and the coal seam is used as the support structure for the coal-uncovering pressure relief of the tunnel.

[0012] In some embodiments, the heading face of the large-section coal-uncovering tunnel is planned into two first-level trapezoidal areas with different sizes in the cross-section. Two relatively smaller second-level trapezoidal areas are separated from the two first-level trapezoidal areas. The trapezoidal prism between the planned second-level trapezoidal area and the coal seam is used as the support structure for the coal-uncovering pressure relief of the tunnel, including:

[0013] The heading face of the large-section coal-uncovering tunnel is planned into two first-level trapezoidal areas with different sizes and stacked vertically in the cross-section. The two first-level trapezoidal areas are divided into six sub-blocks. The six sub-blocks include a first side part, a second side part, and an intermediate part located between the first side part and the second side part. Among them, the first side part includes a first triangular block and a first quadrilateral block. The bottom side of the first triangular block shares a side with the top side of the first quadrilateral part. The second side part includes a second triangular block and a second quadrilateral block. The bottom side of the second triangular block shares a side with the top side of the second quadrilateral block. The intermediate part includes two second-level trapezoidal areas. The bottom side of one second-level trapezoidal area shares a side with the top side of the other second-level trapezoidal area.

[0014] In some embodiments, the sub-block sequence includes: First, determine the length of the bottom side (AB) of the first-level trapezoidal area (ABFE) according to the maximum span of the cross-section. Take the width at the middle position of the truncated side as the length of the bottom side (EF) of the first-level trapezoidal area (EFDC). Take the length of the top side (CD) of the first-level trapezoidal area (EFDC) at a position 1 / 3 of the length of the bottom side (AB) of the first-level trapezoidal area (ABFE). Then, determine the height of the two first-level trapezoidal areas according to 1 / 2 of the cross-section height. Take points (G) and (H) at equal distances on the bottom side (AB), and take points (M) and (N) on the left and right of the center of the bottom side (EF). Connect point (M) and point (N) and point (G) and point (H) to obtain the second-level trapezoidal area (CDNM) and the second-level trapezoidal area (GHNM). Finally, divide the heading face of the tunnel into 6 block areas. Among them, points (A), (B), (E), and (F) all have inclined projection points (a), (b), (e), and (f) in the coal seam respectively. The projections of points (C), (D), (G), (H), (M), and (N) in the coal seam are mirror projections, corresponding to points c, d, g, h, m, and n respectively.

[0015] In some embodiments, precise construction positioning and drilling operations are carried out, including:

[0016] Inclined drilling is carried out at six corner points of the outer contours of two first-order trapezoidal areas on the heading face of the large-section coal uncovering tunnel.

[0017] In some embodiments, continuously cutting the coal seam using a wire saw with the reverse cutting method and the nested cutting method includes:

[0018] Step S31, based on the coal seam space of the borehole, first cut two side edges and one bottom edge of the first triangular block and two side edges of the first quadrilateral block of the large-section coal uncovering tunnel using the reverse cutting method, and then cut two side edges and one bottom edge of the second triangular block and two side edges of the second quadrilateral block of the large-section coal uncovering tunnel;

[0019] Step S32, based on the coal seam space of the borehole, first cut the rear edge of the first triangular block and the rear edge of the first quadrilateral block using the nested cutting method, and then cut the rear edge of the second triangular block and the rear edge of the second quadrilateral block;

[0020] Step S33, based on the coal seam space of the borehole, cut the common edge between the first-order trapezoidal area and the second-order trapezoidal area using the reverse cutting method to complete the cutting of the coal seam.

[0021] In some embodiments, the wire saw is a diamond bead string winding.

[0022] In some embodiments, the slot cut by the diamond wire saw is not used for cutting and excavation, but can provide a free face for subsequent blasting excavation.

[0023] Compared with the prior art, the technical effects achieved by the present invention are as follows:

[0024] (1) The present invention uses the reverse cutting method and the nested cutting method to cut the coal seam rock mass without removing the coal seam rock mass, ensuring construction safety.

[0025] (2) The present invention constructs a double-trapezoidal support system, realizes directional pressure relief, permeability enhancement and strengthening, efficient gas emission and coordinated regulation of in-situ stress of the coal seam through diamond wire saw cutting technology, which is stable and reliable, and avoids the collapse of the heading face.

[0026] (3) The present invention adopts block-by-block cutting, prevents abnormal gas gushing and maximally utilizes the semi-circular area of the tunnel heading face, improving the efficiency of permeability enhancement and pressure relief.

[0027] (4) The slot cut by the diamond wire saw of the present invention is not used for cutting and excavation, but can provide a free face for subsequent blasting excavation, effectively reducing the construction cost of the tunnel.

[0028] (5) The present invention can accurately cut the coal seam in large areas multiple times, accelerating the expansion of fissures in the coal seam, thereby accelerating the adsorption, desorption, and diffusion of gas, achieving an efficient effect of increasing permeability and relieving pressure, and solving the technical problems of high cost, low efficiency, and insufficient safety existing in the conventional measures for outburst prevention during coal face uncovering in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the block division of the coal face in a large-section coal-uncovering tunnel provided by the present invention in an embodiment;

[0030] Figure 2 It is a three-dimensional schematic diagram of the block division of the coal face in a large-section coal-uncovering tunnel provided by the present invention in an embodiment;

[0031] Figure 3 It is a working schematic diagram of the pressure relief and outburst elimination device for cutting the coal seam with a double-trapezoidal side wire saw in a coal-penetrating tunnel provided by the present invention in an embodiment from the first perspective. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The technical solutions of the present invention will be described below through specific embodiments with reference to the accompanying drawings. It should be understood that one or more than four steps mentioned in the present invention do not exclude the existence of other methods and steps before and after the combined steps, or other methods and steps can be inserted between these clearly mentioned steps. It should also be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. Unless otherwise specified, the numbers of each method step are only for the purpose of identifying each method step, rather than limiting the arrangement order of each method or the implementation scope of the present invention. The change or adjustment of their relative relationship can also be regarded as the scope in which the present invention can be implemented under the condition of no substantial change in technical content.

[0033] There are no specific restrictions on the sources of the raw materials and instruments used in the embodiments, and they can be purchased in the market or prepared according to the conventional methods well-known to those skilled in the art.

[0034] Embodiment:

[0035] The present invention provides a pressure relief and outburst elimination method for cutting with a double-trapezoidal support wire saw in a coal-penetrating tunnel. The present invention can accurately cut the coal seam in large areas multiple times, accelerating the expansion of fissures in the coal seam, thereby accelerating the adsorption, desorption, and diffusion of gas, achieving an efficient effect of increasing permeability and relieving pressure, and solving the technical problems of high cost, low efficiency, and insufficient safety existing in the conventional measures for outburst prevention during coal face uncovering in the prior art.

[0036] As Figures 1 - 3 shown, in some embodiments, a pressure relief and outburst elimination method for cutting with a double-trapezoidal support wire saw in a coal-penetrating tunnel is provided. During the implementation of this pressure relief and outburst elimination method for cutting with a double-trapezoidal support wire saw in a coal-penetrating tunnel, a pressure relief and outburst elimination device for cutting the coal seam with a double-trapezoidal side wire saw in a coal-penetrating tunnel is adopted.

[0037] The pressure relief and outburst elimination device for cutting coal seams with a double-trapezoidal side rope saw in a coal-passing tunnel includes a drilling machine and a rope saw machine; in some embodiments, the pressure relief and outburst elimination device further includes: a hydraulic support and guiding device for positioning and guiding the rope saw, and the drilling provides a working space for the hydraulic support and guiding device and the rope saw machine. In some embodiments, the hydraulic support and guiding device includes: a positioning and guiding wheel and a hydraulic telescopic rod, and the positioning and guiding wheel is arranged on the hydraulic telescopic rod.

[0038] The method for pressure relief and outburst elimination by cutting with a double-trapezoidal support rope saw in a coal-passing tunnel is applicable to the cutting of the heading face of a large-section coal uncovering tunnel. The large-section coal uncovering tunnel has the characteristics of large span, flattening, and large cross-sectional area. Coupled with the influence of gas pressure, accidents such as coal and gas outbursts or heading face collapses are likely to occur.

[0039] The method for pressure relief and outburst elimination by cutting with a double-trapezoidal support rope saw in a coal-passing tunnel includes the following steps:

[0040] Step S1, divide the heading face of the large-section coal uncovering tunnel into two first-level trapezoidal areas with different sizes (the large first-level trapezoidal area ABFE and the small first-level trapezoidal area EFDC) in the cross-section, and separate two smaller second-level trapezoidal areas from the two first-level trapezoidal areas as the support structure of the heading face of the large-section coal uncovering tunnel;

[0041] In some embodiments, divide the heading face of the large-section coal uncovering tunnel into two first-level trapezoidal areas that are different in size and stacked up and down in the cross-section. The two first-level trapezoidal areas are divided into multiple blocks, and the multiple blocks include two second-level trapezoidal areas that are relatively smaller than the first-level trapezoidal areas. The two second-level trapezoidal areas are used as the support structure of the heading face of the large-section coal uncovering tunnel;

[0042] During the process of enhancing coal seam permeability and relieving pressure, it is necessary to prevent the stress of the heading face of the large-section coal uncovering tunnel from being too concentrated, and the force exerted on the surrounding rock is greater than the critical value, resulting in a collapse of the heading face. The block division incorporates the concept of multi-step excavation of the tunnel. While enhancing permeability and relieving pressure, a support structure with a double-trapezoidal side is formed, and on the premise of ensuring safety and no collapse, the area of the coal seam cut by the rope saw is made as large as possible.

[0043] Among them, multi-step excavation is a method of tunnel excavation carried out in stages and levels. It divides the heading face of the large-section coal uncovering tunnel into multiple steps, and each step is excavated and supported in sequence, thereby gradually advancing the tunnel. This multi-step excavation helps to disperse and control the pressure from the surrounding rock mass and ensure construction safety.

[0044] In some embodiments, the two first-level trapezoidal regions are divided into six sub-blocks in total. The six sub-blocks include a first side portion, a second side portion, and an intermediate portion located between the first side portion and the second side portion. Among them, the first side portion includes a first triangular block 3 and a first quadrilateral block 4. The base of the first triangular block 3 shares an edge with the top edge of the first quadrilateral portion 4. The second side portion includes a second triangular block 5 and a second quadrilateral block 6. The base of the second triangular block 5 shares an edge with the top edge of the second quadrilateral block 6. The intermediate portion includes two second-level trapezoidal regions. The base of one second-level trapezoidal region 1 shares an edge with the top edge of the other second-level trapezoidal region 2.

[0045] The order of the sub-blocks is as follows:

[0046] The order of the sub-blocks includes: First, determine the length of the base AB of the first-level trapezoidal region ABFE according to the maximum span of the cross-section. Take the width at the middle position of the truncated edge as the length of the base EF of the first trapezoid EFDC. Take the length of the top edge CD of the first-level trapezoidal region EFDC at a position 1 / 3 of the length of the base AB of the first-level trapezoidal region ABFE. Then, determine the height of the two first-level trapezoidal regions according to 1 / 2 of the cross-section height. Take points G and H at equal distances on the base AB, and take points M and N on the left and right of the center of the base EF. Connect point M and point N, and point G and point H to obtain two second-level trapezoidal regions CDNM and second-level trapezoidal region GHNM. Finally, divide the tunnel face into 6 block regions. Among them, points A, B, E, and F all have inclined projection points a, b, e, and f in the coal seam. Points C, D, G, H, M, and N are mirror projections in the coal seam, corresponding to points c, d, g, h, m, and n respectively. For specific reference Figure 2 .

[0047] Dividing into 6 blocks provides a structural form for forming the support of a double trapezoid. If divided into other quantities, there are the following problems:

[0048] (1) If a rectangle is taken from a flat semi-circle and divided into 4 blocks, it will cause the projection in the coal seam to be too small when using a wire saw for cutting, and the cutting area is too small to achieve the purpose of increasing permeability and relieving pressure.

[0049] (2) If simply divided into 3 rectangles, the support force may be insufficient and there is a risk of collapse.

[0050] Dividing into 6 blocks can make the best use of the area of the semi-circular tunnel face and can also form the support of a double trapezoid, which is the preferred way of dividing blocks. In order to form the support structure of the double trapezoidal sides, the trapezoidal support usually consists of cross braces, vertical braces, and diagonal braces to form a stable geometric shape. Its design aims to effectively share and transfer the pressure from the rock and soil mass to prevent the collapse of the tunnel face and the surrounding rock mass. The trapezoidal support has the following advantages:

[0051] (1) Superior mechanical properties: The trapezoidal structure can effectively disperse and transfer the complex stresses from the rock and soil, providing better stability.

[0052] (2) Strong adaptability: Suitable for different types of tunnel cross-sections, especially tunnels with semi-circular or arched cross-sections.

[0053] (3) Convenient construction: Compared with some complex support structures, the construction of trapezoidal supports is relatively simple and easy to implement and maintain.

[0054] Step S2, based on the occurrence conditions of the coal seam in front of the heading face and the heading face planning of the large-section coal-removing tunnel, use a drilling machine to construct a borehole at the positioning point;

[0055] In some embodiments, long and inclined boreholes are constructed, which can project the cutting area on the coal seam as large as possible, improving the efficiency of permeability enhancement and pressure relief.

[0056] Before the tunneling work edge approaches the coal seam, it is necessary to take advanced detection measures to accurately master the seam horizon, occurrence conditions and gas geology laws. In addition, during the construction process, comprehensive advanced geological forecasting needs to be carried out by combining various means such as geological surveys, geophysical prospecting, and drilling.

[0057] According to Article 49 of the "Regulations on the Prevention and Control of Coal and Gas Outbursts", the regional outburst prevention measures for pre-draining the coal seam gas in the cross-cut boreholes for uncovering coal in the cross-cut (including vertical and inclined shafts, etc.) shall be implemented before the minimum normal distance between the uncovering coal work edge and the coal seam is 7m (the distance should be appropriately increased in the tectonic damage zone). The minimum control range of the boreholes is: 12m outside the roadway contour line at the uncovering coal point of the cross-cut and vertical and inclined shafts (6m at the bottom or the lower side of the steeply inclined coal seam). At the same time, it should also be ensured that the minimum distance from the outer edge of the control range to the roadway contour line (including the contour line of the expected roadway section for uncovering coal ahead) is not less than 5m. And when the borehole cannot penetrate the entire coal seam thickness at one time, the minimum advance distance of the coal borehole should be maintained at 15m. However, the increase in the cross-sectional area of the large-section tunnel will significantly change the stress distribution of the surrounding rock. To avoid coal and gas outburst accidents caused by excavation disturbance and insufficient safety distance, the advance safety rock pillar distance of the regional outburst prevention measures needs to be increased accordingly. Through analogy engineering and empirical analysis, the designed value of the advance safety rock pillar for the outburst prevention measures in most tunnel coal-uncovering areas is 10m, and the control range of the boreholes should also be larger. Based on the occurrence conditions of the coal seam in front of the heading face, the angle and length of the boreholes are designed. According to the "Technical Specifications for the Design and Construction of Highway Gas Tunnels" (JTG / T 3374—2020), there is no specific upper limit requirement for the depth of the gas tunnel drainage boreholes. On the premise of meeting the specifications, a larger length will increase the effective area of the wire saw cutting and improve the effect of pressure relief and outburst elimination.

[0058] In the construction of large-section highway tunnels, the tunnel face can be regarded as an elliptical cross-section. Let the length of its major axis be a and the length of its minor axis be b. A point on the ellipse can be expressed by Equation (1):

[0059]

[0060] a, b, and φ represent a point on the ellipse. Through advanced geological exploration and corresponding exploration borehole data during the tunnel excavation process, the coal seam dip angle is known to be α, the coal seam thickness is H, the angle between the tunnel and the coal seam strike is set to β, and the minimum normal distance from the borehole position to the coal seam is S. According to the borehole control range in the "Regulations on the Prevention and Control of Coal and Gas Outbursts", the distance Z outside the tunnel contour line at the coal uncovering location is added as a variable, and the minimum distance W from the outer edge to the tunnel contour line is also added.

[0061] The following formula is applicable to the inclined long boreholes drilled at the six ellipse points A / B / C / D / E / F:

[0062] The horizontal component D of the borehole can be expressed by Equation (2):

[0063]

[0064] The vertical component V of the borehole can be expressed by Equation (3):

[0065] V = Hsin(α) + W + bsin(φ);

[0066] The minimum inclination angle of the borehole is Equation (4):

[0067]

[0068] The minimum deviation angle of the borehole is Equation (5):

[0069]

[0070] The borehole length is Equation (6):

[0071]

[0072] The borehole inclination angle and length formulas for points M / N / E / F are different from the above formulas and can be regarded as a trapezoidal truncated edge with a height of 1 / 4b, divided into two cases: the upper vertex and the lower vertex:

[0073] The minimum inclination angle of the upper vertex boreholes M and N is Equation (7):

[0074]

[0075] The minimum deviation angle of boreholes M and N is Equation (8):

[0076]

[0077] The lengths of boreholes M and N are expressed by Equation (9):

[0078]

[0079] The minimum dip angles of the lower vertex boreholes E and F are expressed by Equation (10):

[0080] θ = arctan(-cot(α));

[0081] The minimum deviation angles of boreholes E and F are expressed by Equation (11):

[0082] ε = -α;

[0083] The lengths of boreholes E and F are expressed by Equation (12):

[0084]

[0085] In some embodiments, for a large-section tunnel coal uncovering heading face, the height is 10 m, the span is 15 m, the coal seam thickness is 4.4 m, the minimum normal distance from the borehole to the coal seam is 10 m, the coal seam dip angle is -5°, the angle between the tunnel and the coal seam strike is 45°, the distance outside the tunnel contour line at the specified coal uncovering location is 15 m, and the minimum distance from the outer edge to the tunnel contour line is 7 m.

[0086] Among them, the minimum dip angle of borehole Aa is 14.57°, the minimum upward angle of borehole Aa is 32.11°, and the length of borehole Aa is 26.34 m.

[0087] The minimum dip angle of borehole Cc is 25.57°, the minimum upward angle of borehole Cc is 51.93°, and the length of borehole Cc is 26.99 m.

[0088] The minimum dip angle of borehole Mm is 87.49°, the minimum upward angle of borehole Mm is 2.51°, and the length of borehole Mm is 14.41 m.

[0089] The minimum dip angle of borehole Ee is 85°, the minimum upward angle of borehole Ee is 5°, and the length of borehole Ee is 9.42 m.

[0090] The specific calculation process is as follows:

[0091]

[0092]

[0093] Therefore, the minimum dip angle of borehole Aa is 14.57°, the minimum deviation angle of borehole Aa is 32.11°, and the length of borehole Aa is 26.34 m.

[0094]

[0095] Therefore, the minimum dip angle of borehole Cc is 25.57°, the minimum deviation angle of borehole Cc is 51.93°, and the length of borehole Cc is 26.99 m.

[0096]

[0097] Therefore, the minimum dip angle of borehole Mm is 87.49°, the minimum deviation angle of borehole Mm is 2.51°, and the length of borehole Mm is 14.41 m.

[0098]

[0099] Therefore, the minimum dip angle of borehole Ee is 85°, the minimum deviation angle of borehole Ee is 85°, and the length of borehole Ee is 9.42 m.

[0100] According to the borehole control target of this implementation technology, the target area covers the borehole control range in the "Regulations on the Prevention and Control of Coal and Gas Outburst", enabling the target range of wire saw cutting of coal seams for pressure relief and permeability enhancement to meet the requirements of coal seam gas pressure relief and permeability enhancement; at the same time, without removing the coal seam rock mass, the coal seam rock mass is cut to ensure construction safety.

[0101] In some embodiments, inclined boreholes are drilled at six corner points on the outer contours of two first-level trapezoidal areas on the heading face of the large-section coal-removing tunnel.

[0102] Step S3, finally, based on the heading face planning and borehole conditions of the large-section coal-removing tunnel, a wire saw machine is used to continuously cut the middle part of the coal seam and the rock mass of the support structure by the reverse cutting method and the nested cutting method to complete the pressure relief and permeability enhancement of the coal seam. In some embodiments, the wire saw is a diamond bead wire winding.

[0103] In some embodiments, using the wire saw to continuously cut the coal seam by the reverse cutting method and the nested cutting method includes:

[0104] Step S31, based on the coal seam space of the borehole, first cut the two side edges (side edges CceE and CcmM) and one bottom edge EemM of the first triangular block 3 of the large-section coal-removing tunnel and the two side edges (side edges AaeE and GgmM) of the first quadrilateral block 4 by the reverse cutting method, and then cut the two side edges (side edges DdnN and DdfF) and one bottom edge FfnN of the second triangular block 5 of the large-section coal-removing tunnel and the two side edges (side edges HhnN and BbfF) of the second quadrilateral block 6; it is necessary to cut one side first and then the other side because it is necessary to continuously monitor and guard against abnormal gas outbursts to ensure the safety of construction personnel. When the gas pressure is less than 0.74 MPa specified for gas tunnel construction and the gas concentration is less than 1%, the cutting of the next section can continue. The block-by-block cutting should be combined with real-time gas monitoring, and it is best to have an interval of more than 2 hours in the middle. The stress of the surrounding rock should also be monitored to prevent the direct collapse of the heading face.

[0105] As shown in Figure 3 , specifically, taking the cutting of EemM as an example, the positioning guide wheel 1 is pushed to the deepest part of the borehole and fixed by the hydraulic telescopic rod 2. The diamond bead wire 3 is wound around the positioning guide wheel 1 of the support guide device in two boreholes on the side to be cut. It is necessary to adjust the positions of the tensioning device 6 and the wire saw machine 5 to make the wire saw closely adhere to the face between the two boreholes. The cutting position on the face is adjusted and fixed by the rotary wheel 4. Start the wire saw machine 5 to cut the coal and rock mass at a constant speed. The wire saw 3 is continuously tightened and cut forward by the movement of the wire saw machine 5 and the tensioning device 6 until the wire saw 3 cuts to the position of the connection line of the two positioning guide wheels 1. At the same time, the water spraying device is opened at the wire inlet end to wash out the cut coal and rock debris.

[0106] Step S32: Based on the coal seam space of the borehole, the sleeve cutting method is adopted to first cut the rear edge ecm of the first triangular block 3 and the rear edge aemg of the first quadrilateral block 4, and then cut the rear edge dfn of the second triangular block 5 and the rear edge bfnh of the second quadrilateral block 6.

[0107] The cutting sequence is to give priority to cutting the rear edges ecm and dfn. After monitoring the stress change and no abnormal gas emission, then cut the rear edges aemg and bfnh. The sleeve cutting method means that when three sides of the tetrahedron have been cut, the rear edge of the rock mass can be directly cut.

[0108] Specifically, taking the cutting of the rear edge aemg as an example, on the premise that the sides AEea, GMmg, and EMme have all been cut, the positioning guide wheel is pushed to the deepest point a of the borehole Aa and the deepest point g of the borehole Gg and fixed by the hydraulic telescopic rod. At the same time, the cutting flat edge of the two-point positioning guide wheel is adjusted to be on the same flat edge as the pre-cut edge of the coal seam. Then, the wire is sleeved in the already cut flat edge to determine the sleeve cutting loop. The sleeve cutting loop is: wire saw machine → tensioning wheel → rotary wheel → a-point positioning guide wheel → e-point coal seam rock mass → m-point coal seam rock mass → g-point positioning guide wheel → rotary wheel → tensioning wheel → wire saw machine. The wire saw at the coal body is closely adhered to the coal seam by adjusting the positions of the tensioning device and the wire saw machine. The cutting position is adjusted and fixed by the rotary wheel. Start the wire saw machine to cut the coal seam, and at the same time, open the water spraying device at the wire inlet end to wash out the cut coal and rock debris.

[0109] Step S33: Based on the coal seam space of the borehole, the common edge MmnN between the secondary trapezoidal area 1 and the secondary trapezoidal area 2 is cut using the reverse cutting method to complete the cutting of the coal seam. Cutting the common edge MmnN is for stress release. The supported secondary trapezoidal area 1 and secondary trapezoidal area 2, under normal circumstances, will not have too much stress concentration because no rock mass is removed, and the risk of collapse is relatively small. However, if the coal body cutting causes the coal seam to be damaged too severely, damaging the contact edge of the coal and rock mass on the trapezoidal back edge, affecting the stability of the coal and rock, resulting in a large amount of stress concentrating on the supported secondary trapezoidal area 1 and secondary trapezoidal area 2, it may directly push them out. But cutting the common edge MmnN can greatly reduce the stress concentration, release the pressure, ensure that the two trapezoidal supports are independent, further maintain stability, and prevent the face from collapsing.

[0110] The nested cutting method is repeatedly used to continuously cut the coal seam to complete pressure relief and permeability enhancement and stress release; when cutting the coal body by the nested cutting method multiple times, considering the damage of the wire saw cutting to the borehole, during the nested cutting operation, the length of the support guiding device is adjusted from far to near. During this process, it is still ensured that the cutting flat edges of the two positioning guide wheels in the bottom borehole and the pre-cut edge of the coal seam are on the same flat edge. The nested cutting steps are repeated to perform multiple slotting pressure relief on the coal seam. To facilitate the movement of the wire saw machine in the roadway, a track-type wire saw machine is adopted and equipped with a traction device to ensure sufficient tension during cutting.

[0111] To facilitate the movement of the wire saw machine in the roadway, a track-type wire saw machine is adopted and equipped with a traction device to ensure sufficient tension during cutting.

[0112] During the implementation process, diamond wire saws are used to cut the coal seam and rock stratum to achieve efficient and silent effects, increase the stability of construction, and further reduce costs.

[0113] It can be used in conjunction with gas drainage boreholes to achieve a better effect of discharging gas and reduce the risk of coal and gas outburst.

[0114] The present invention uses the reverse cutting method and the nested cutting method to cut the coal seam rock mass without removing the coal seam rock mass to ensure construction safety; the present invention constructs a double-trapezoidal support system, which is stable and reliable, and avoids the collapse of the face; the present invention adopts block cutting to prevent abnormal gas gushing and maximally utilize the semi-circular area of the tunnel face, improving the efficiency of permeability enhancement and pressure relief. The present invention can fully provide a stress release space for the coal seam and accelerate the gas pressure release speed to achieve the purpose of pressure relief, permeability enhancement, and outburst elimination before uncovering the coal, can fully release the in-situ stress, and leave a supporting rock mass at the face, eliminating the collapse risk that may be caused by cutting the coal seam. The present invention has the characteristics of improving the coal seam extraction efficiency, low cost, high safety, and stable and reliable.

[0115] The foregoing description of specific exemplary embodiments of the invention is for purposes of illustration and exemplification. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that, according to the above teachings, many modifications and variations are possible. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the invention and its practical applications, so that those skilled in the art can implement and utilize the various different exemplary embodiments of the invention, as well as various different selections and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A double-trapezoidal support wire saw cutting pressure relief and outburst elimination method for coal-passing tunnels, characterized in that, It includes the following steps: First, divide the face of the large-section coal uncovering tunnel into two first-level trapezoidal areas with different sizes on the cross-section, and further divide smaller second-level trapezoidal areas from the two first-level trapezoidal areas. Use the trapezoidal prism between the planned second-level trapezoidal area and the coal seam as the support structure for coal uncovering and pressure relief in the tunnel. Then, based on the occurrence of the coal seam in front of the face and the face planning of the large-section coal uncovering tunnel, carry out precise construction positioning and drilling operations. Finally, based on the face planning and drilling operation conditions of the large-section coal uncovering tunnel, use a diamond wire saw to continuously cut the middle part of the coal seam and the rock mass of the support structure by the reverse cutting method and the sleeve cutting method to complete the permeability enhancement and pressure relief of the coal seam; Divide the face of the large-section coal uncovering tunnel into two first-level trapezoidal areas with different sizes and stacked on top of each other on the cross-section. The two first-level trapezoidal areas are divided into six blocks in total. The six blocks include a first side part, a second side part, and a middle part located between the first side part and the second side part. Among them, the first side part includes a first triangular block and a first quadrilateral block, and the bottom edge of the first triangular block shares an edge with the top edge of the first quadrilateral part. The second side part includes a second triangular block and a second quadrilateral block, and the bottom edge of the second triangular block shares an edge with the top edge of the second quadrilateral block. The middle part includes two second-level trapezoidal areas, and the bottom edge of one second-level trapezoidal area shares an edge with the top edge of the other second-level trapezoidal area; The block sequence includes: First, determine the length of the bottom edge AB of the first-level trapezoidal area ABFE according to the maximum span of the cross-section, take the width at the middle position of the cut edge as the length of the bottom edge EF of the first-level trapezoidal area EFDC, take the length of the top edge CD of the first-level trapezoidal area EFDC at 1 / 3 of the length of the bottom edge AB of the first-level trapezoidal area ABFE. Then, determine the height of the two first-level trapezoidal areas according to 1 / 2 of the cross-section height. Take points G and H at equal distances on the bottom edge AB, and take points M and N on the left and right of the center of the bottom edge EF. Connect point M and point N and point G and point H to obtain the second-level trapezoidal area CDNM and the second-level trapezoidal area GHNM. Finally, divide the face of the tunnel into 6 block areas. Among them, points A, B, E, and F all have inclined projection points a, b, e, and f in the coal seam respectively, and the projections of points C, D, G, H, M, and N in the coal seam are mirror projections, corresponding to points c, d, g, h, m, and n respectively; Using a wire saw to continuously cut the coal seam by the reverse cutting method and the sleeve cutting method includes: Step S31, based on the coal seam space of the drill holes, first cut the two side edges and one bottom edge of the first triangular block of the large-section coal uncovering tunnel and the two side edges of the first quadrilateral block by the reverse cutting method, and then cut the two side edges and one bottom edge of the second triangular block of the large-section coal uncovering tunnel and the two side edges of the second quadrilateral block; Step S32, based on the coal seam space of the drill holes, first cut the rear edge of the first triangular block and the rear edge of the first quadrilateral block by the sleeve cutting method, and then cut the rear edge of the second triangular block and the rear edge of the second quadrilateral block; Step S33, based on the coal seam space of the drill holes, cut the common edge of the first-level trapezoidal area and the second-level trapezoidal area by the reverse cutting method to complete the cutting of the coal seam.

2. The double-trapezoid support wire saw cutting pressure relief and outburst elimination method for coal-passing tunnels according to claim 1, wherein, Precision construction positioning and drilling operations are carried out, including: Inclined drilling is carried out at six corner points on the outer contours of two first-level trapezoidal areas on the heading face of the large-section coal uncovering tunnel.

3. The double-trapezoid support wire saw cutting pressure relief and outburst elimination method for coal-penetrating tunnels according to claim 1, wherein The wire saw is wound with diamond beads.

4. The double-trapezoid support wire saw cutting pressure relief and outburst elimination method for coal-passing tunnels according to claim 1, wherein, The slot cut by the diamond wire saw is not used for cutting and excavation, but can provide a free face for subsequent blasting excavation.

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