Methods for arranging roadways in isolated coal seam pillars

Abstract

This invention discloses a method for arranging roadways in an isolated coal pillar in a coal seam, comprising: obtaining the key roof strata at the top of the coal pillar; the coal pillar having a first side and a second side in its width direction, and performing roof cutting and pressure relief on the key roof strata of the first and second sides of the coal pillar; arranging return airway and intake airway staggered in the height and width directions within the coal pillar; one of the return airway and the intake airway being adjacent to the roof and constructed as an upper roadway, and the other being adjacent to the floor and constructed as a lower roadway; the upper roadway being excavated a first preset distance before the lower roadway; after pressure relief construction is performed in the middle region of the coal pillar in the upper roadway, the lower roadway is excavated; and supporting the intake airway and the return airway. This invention can proactively optimize the stress environment of the coal pillar, ensuring the safety and stability of the roadway.

Description

Technical Field

[0001] This invention belongs to the field of coal seam mining technology, and specifically relates to a method for arranging roadways in isolated coal seam pillars. Background Technology

[0002] In coal mining operations, due to factors such as tight working face continuity and complex geological conditions, isolated coal pillars surrounded by goaf areas are often formed. In early mining practices, due to insufficient theoretical guidance, ultra-wide coal pillars with a width of 30-50 meters were often left between adjacent working faces in extra-thick coal seams (thickness ≥10m).

[0003] In related technologies, after the mining of extra-thick coal seams, the intense structural movement of the overlying strata causes isolated coal pillars to bear extremely high stress concentrations, often forming high-stress zones within them. If roadways are directly located within these zones, it will lead to severe deformation and plastic damage of the surrounding rock, making maintenance extremely difficult and posing significant safety risks. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the related art.

[0005] Therefore, embodiments of the present invention propose a method for arranging roadways in isolated coal pillars in coal seams that can actively optimize the stress environment of coal pillars and ensure the safety and stability of roadways.

[0006] The method for arranging roadways in coal seam islands and coal pillars according to embodiments of the present invention includes:

[0007] Obtain the key strata of the roof at the top of the coal pillar;

[0008] The coal pillar has a first side and a second side in its width direction, and the key strata of the roof on the first side and the second side of the coal pillar are cut off to relieve pressure;

[0009] The return airway and intake airway are arranged in a staggered manner in the height and width directions within the coal pillar;

[0010] One of the return airway and the intake airway is adjacent to the roof and is constructed as an upper airway, and the other is adjacent to the floor and is constructed as a lower airway. The upper airway is excavated a first preset distance before the lower airway. After the pressure relief construction is carried out in the middle area of ​​the coal pillar in the upper airway, the lower airway is excavated.

[0011] The intake airway and the return airway are supported.

[0012] The roadway layout method for isolated coal pillars in this invention optimizes the roadway layout and excavation sequence of the isolated coal pillar working face. Through roof-cutting and pressure-relief technology, it improves the stress environment of the isolated coal pillar in extra-thick coal seams, optimizes the external stress environment of the coal pillar, cuts off the stress transmission structure of the roof, and eliminates the main stress concentration sources. This allows for a more complete release of stress in the overlying strata, fundamentally improving the stress environment of the roadway and facilitating mine disaster prevention and mitigation. This embodiment further transfers stress within the isolated coal pillar by sequentially excavating different roadways and improves the internal stress distribution of the coal pillar through active pressure relief, providing a favorable stress environment for the excavation of the lower roadways and enhancing the safety of roadway excavation.

[0013] In some embodiments, during the step of cutting off the roof and relieving pressure on the key strata of the first and second sides of the coal pillar, hydraulic fracturing is performed on the key strata of the roof above the first side and the key strata of the roof above the second side of the coal pillar, so as to achieve hydraulic fracturing and cutting off the roof and relieving pressure on the key strata of the roof on both sides of the coal pillar.

[0014] In some embodiments, hydraulic fracturing is performed by arranging first hydraulic fracturing holes above the first and second sides of the coal pillar, the first hydraulic fracturing holes being arranged along the extension direction of the coal pillar.

[0015] Alternatively, hydraulic fracturing can be carried out by arranging a second hydraulic fracturing hole above the first and second sides, with the second hydraulic fracturing hole inclined toward the middle of the coal pillar and / or inclined toward the excavation direction of the intake airway and the return airway.

[0016] In some embodiments, the step of arranging return airway and intake airway staggered in the height and width directions within the coal pillar includes:

[0017] The stress monitoring data of the coal pillar is obtained and combined with numerical simulation to determine the stress distribution in the coal pillar;

[0018] Identify the high-stress and low-stress zones within the coal pillar;

[0019] One of a return airway and an intake airway is arranged in the low-stress zone adjacent to the roof of the coal pillar, and the other of a return airway and an intake airway is arranged in the low-stress zone adjacent to the floor of the coal pillar. The return airway and the intake airway are spaced apart in the width direction of the coal pillar.

[0020] In some embodiments, the upper roadway is arranged adjacent to the first side of the coal pillar, the lower roadway is arranged adjacent to the second side of the coal pillar, a first free coal pillar is reserved between the upper roadway and the goaf on the first side of the coal pillar, and a second free coal pillar is reserved between the lower roadway and the goaf on the second side of the coal pillar.

[0021] In some embodiments, the distance between the first and second sides of the coal pillar is greater than or equal to 30m, the thickness of the coal pillar is greater than or equal to 10m, and the width of the first and second free coal pillars is 8m to 10m.

[0022] In some embodiments, the step of depressurizing the middle region of the coal pillar in the upper roadway before excavating the lower roadway includes:

[0023] Along the extension direction of the upper roadway, blasting pressure relief holes are constructed sequentially in the upper roadway. The blasting pressure relief holes extend toward the middle area of ​​the coal pillar or the intake airway and are used for blasting pressure relief.

[0024] After the blasting and decompression work in the upper roadway reaches the second preset distance along the extension direction of the upper roadway, the construction of the lower roadway is carried out. The second preset distance is less than the first preset distance.

[0025] In some embodiments, the depth of the blasting pressure relief hole is And satisfy:

[0026]

[0027] In the formula, The width between the first and second sides of the coal pillar. The widths of the first and second free coal pillars are given. The width of the upper tunnel is given. The height of the upper tunnel. This refers to the thickness of the coal seam.

[0028] In some embodiments, the first preset distance is greater than or equal to 100m, and the second preset distance is greater than or equal to 50m;

[0029] And / or, the diameter of the blasting relief hole is 60mm to 100mm, the plugging length of the blasting relief hole is not less than 1 / 2 of the depth of the blasting relief hole, and the charge density in the blasting relief hole is not less than 1Kg / m;

[0030] And / or, during blasting decompression operations, at least one blasting decompression hole is spaced between each subsequent blasting decompression and the previous blasting decompression.

[0031] In some embodiments, the upper tunnel is a return air tunnel, and the lower tunnel is an intake air tunnel;

[0032] And / or, the top of the upper tunnel is arranged along the roof plate, and the bottom of the lower tunnel is arranged along the floor plate;

[0033] And / or, the top of the upper roadway is supported by prestressed anchor bolts or prestressed anchor cables, the sides of the upper roadway are supported by split grouting anchor cables and / or shotcrete, and the lower roadway is supported by a combination of full-section split grouting anchor cables and shotcrete.

[0034] And / or, in the step of obtaining the key strata of the roof at the top of the coal pillar, by obtaining the roof and surrounding rock data information of the coal pillar, and judging the key strata of the roof at the top of the coal pillar based on the mine pressure and strata control theory. Attached Figure Description

[0035] Figure 1 This is a flowchart of the roadway layout method in coal seam island coal pillars according to an embodiment of the present invention.

[0036] Figure 2 This is a schematic diagram of the arrangement of the first hydraulic fracturing holes in the coal pillar of the coal seam island according to an embodiment of the present invention.

[0037] Figure 3 This is a schematic diagram of the arrangement of the first hydraulic fracturing holes in the coal pillar of the coal seam island according to an embodiment of the present invention from another perspective.

[0038] Figure 4 This is a schematic diagram of the arrangement of the second hydraulic fracturing holes in the coal pillar of the coal seam island according to an embodiment of the present invention.

[0039] Figure 5 This is a schematic diagram of the arrangement of the second hydraulic fracturing hole in the coal pillar of the coal seam island according to an embodiment of the present invention from another perspective.

[0040] Figure 6 This is a schematic diagram of the layout of the return airway in the coal seam island coal pillar according to an embodiment of the present invention.

[0041] Figure 7 This is a schematic diagram of the arrangement of blasting pressure relief holes in the return airway of an isolated coal pillar in a coal seam, according to an embodiment of the present invention.

[0042] Figure 8 This is a schematic diagram of the excavation of the return airway and intake airway in a coal seam island coal pillar according to an embodiment of the present invention.

[0043] Figure 9 This is a schematic diagram of the tunneling process from another perspective in the return airway and intake airway of an isolated coal pillar in a coal seam, according to an embodiment of the present invention.

[0044] Figure 10 This is a schematic diagram of the arrangement of the 1525 intake airway and the 1525 return airway in the isolated coal pillar according to an embodiment of the present invention.

[0045] Figure 11 This is a schematic diagram from another perspective showing the arrangement of the 1525 intake airway and the 1525 return airway in the isolated coal pillar according to an embodiment of the present invention.

[0046] Figure label:

[0047] 1. Coal pillar; 11. Return airway; 12. Intake airway; 13. First uncoiled coal pillar; 14. Second uncoiled coal pillar;

[0048] 2. Key strata in the roof

[0049] 3. Goaf;

[0050] 41. First hydraulic fracturing hole; 411. Climbing section; 412. Horizontal section; 42. Second hydraulic fracturing hole; 421. Non-fracturing section; 422. Fracturing section;

[0051] 5. Explosive pressure relief hole;

[0052] 61. Return airway 1525; 62. Intake airway 1525; 63. Goaf 1513; 64. Goaf 1503;

[0053] 7. Working face roadway. Detailed Implementation

[0054] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0055] The inventors recognized that when the roadway layout in related technologies adopts a parallel arrangement of two roadways, the strength and stability of the large coal pillars are used to support the pressure of the overlying strata, but this has the following drawbacks:

[0056] (1) Unrelieved pressure on both sides of isolated coal pillars: The core challenge of isolated coal pillars lies in the high stress concentration caused by the coal pillar itself. While supporting the weight of the overlying rock in the goaf, the coal pillar also becomes a powerful stress transmission medium, causing the roadway in this section (especially the roadway along the goaf) to be under peak stress for a long time. This directly causes severe deformation and damage to the surrounding rock. Unrelieved roadways often fall into a vicious cycle of "deformation-re-deformation" during their service life, which greatly increases the maintenance cost throughout the entire life cycle.

[0057] (2) Lack of basis for roadway layout and excavation sequence: During the synchronous excavation of two parallel roadways at close range, the stress fields of their surrounding rock will be significantly superimposed, forming a disturbance zone that affects each other. This leads to a rapid expansion of the plastic zone of the surrounding rock, continuous evolution of deformation, and difficulty in stabilization, resulting in frequent maintenance of the roadways during the construction stage. This working condition seriously restricts the excavation efficiency and constitutes the main technical problem of roadway stability control.

[0058] (3) No blasting pressure relief in the middle of the coal pillar: When tunneling is carried out in an isolated coal pillar without blasting pressure relief measures, it will cause secondary concentration of stress in the surrounding rock. This high-stress environment is very likely to cause large-scale plastic deformation and damage to the surrounding rock of the tunnel, which will significantly restrict subsequent tunneling construction.

[0059] (4) Limited support methods: For high-stress, large-deformation roadways, the traditional passive support mode of "anchor wire mesh cable + frame" has become a technical bottleneck. In actual production, it shows obvious lag and poor control effect. This not only leads to a sharp increase in the comprehensive support cost over the roadway's life cycle, but also becomes a potential threat to mine safety production, and there is an urgent need to transform to a high pre-tightening force, grouting modification and synergistic support system.

[0060] Therefore, embodiments of the present invention provide a method for arranging roadways in isolated coal pillars in coal seams that can actively optimize the stress environment of coal pillars and ensure the safety and stability of roadways.

[0061] See Figure 1 The method for arranging roadways in coal seam islands and coal pillars according to embodiments of the present invention includes:

[0062] S101. Obtain the key stratum 2 of the roof at the top of coal pillar 1.

[0063] Specifically, by acquiring data on the roof and surrounding rock of coal pillar 1, and based on the theory of mine pressure and strata control, the key strata 2 of the roof of coal pillar 1 are determined. The roof and surrounding rock data can include data obtained through methods such as roadway roof columnar sections and observation of surrounding rock structures. Then, based on the theory of mine pressure and strata control, combined with the roadway roof columnar sections and observation of surrounding rock structures, the key strata 2 of the roof of coal pillar 1 are determined.

[0064] S102, the coal pillar 1 has a first side and a second side in its width direction, and the key rock layer 2 of the roof of the first side and the second side of the coal pillar 1 is cut off to relieve pressure.

[0065] See Figures 2-5 During the mining of the working faces on both sides of the coal pillar 1 in the width direction, hydraulic fracturing technology can be used to hydraulically fracture and cut off the key rock strata 2 on both sides of the roof of the coal pillar 1 to relieve pressure, cut off the stress propagation path of the cantilever beam of the roof of the goaf 3, fundamentally improve the stress environment of the roadway, and help the mine prevent and mitigate disasters.

[0066] S103. Within the coal pillar 1, return airway 11 and intake airway 12 are arranged in a staggered manner in the height and width directions.

[0067] See Figures 6-9This embodiment includes a roadway layout plan, which can make the return airway 11 and intake airway 12 more rationally arranged. The two can better avoid high stress areas and optimize the stress distribution inside the coal pillar 1 during the tunneling process, thereby improving the safety of the roadway.

[0068] Of S104, return airway 11, and intake airway 12, one is adjacent to the roof and constructed as the upper roadway, and the other is adjacent to the floor and constructed as the lower roadway. The upper roadway is excavated a first predetermined distance before the lower roadway. After decompression work is carried out in the middle area of ​​the coal pillar 1 in the upper roadway, the lower roadway is excavated. This embodiment optimizes the roadway layout and excavation sequence within the coal pillar 1, avoiding the mutual interference between the two roadways in traditional parallel excavation and improving roadway safety.

[0069] Preferably, in this embodiment, the upper tunnel is a return air tunnel 11, and the lower tunnel is an intake air tunnel 12. The top of the upper tunnel is arranged along the roof plate, and the bottom of the lower tunnel is arranged along the floor plate.

[0070] S105. Support is provided for intake airway 12 and return airway 11, thereby improving the integrity and stability of the surrounding rock bearing structure.

[0071] In this embodiment, the top of the upper roadway is supported by prestressed anchor bolts or prestressed anchor cables, the sides of the upper roadway are supported by split grouting anchor cables and / or shotcrete, and the lower roadway is supported by a combination of full-section split grouting anchor cables and shotcrete.

[0072] In the figure of this embodiment, the up-down direction is the thickness direction of the coal pillar, the left-right direction is the width direction of the coal pillar, and the front-back direction is the tunneling direction of the intake and return airways.

[0073] This embodiment employs differentiated roadway support, devising a differentiated active reinforcement strategy to effectively control the surrounding rock. For the upper roadway, the roof is actively supported by high-prestressed anchor bolts or cables, while the sides are supported by a combination of high-pressure fracturing grouting anchor cables and shotcrete grouting technology. The lower roadway is a full-coal roadway. Because it is entirely located within coal pillar 1 and has weak bearing capacity, a combined support method of full-section high-pressure fracturing grouting anchor cables and shotcrete grouting is adopted. This allows for the overall modification of the loose coal mass, improving the integrity and stability of the surrounding rock bearing structure through active modification.

[0074] The roadway layout method for isolated coal pillars in this invention optimizes the roadway layout and excavation sequence of the isolated coal pillar working face. It improves the stress environment of the isolated coal pillar in extra-thick coal seams through roof-cutting and pressure-relief technology, optimizes the external stress environment of coal pillar 1, cuts off the stress transmission structure of the roof, and eliminates the main stress concentration sources. This allows for a more complete release of stress in the overlying strata, fundamentally improving the stress environment of the roadway and facilitating mine disaster prevention and mitigation. In this embodiment, by excavating different roadways sequentially, the stress within the isolated coal pillar is further transferred, and active pressure relief improves the internal stress distribution of coal pillar 1, providing a favorable stress environment for the excavation of the lower roadways and enhancing the safety of roadway excavation.

[0075] In some embodiments, during step S102, the key strata 2 of the roof on the first and second sides of the coal pillar 1 are cut off and depressurized by hydraulic fracturing, and the key strata 2 of the roof on the upper part of the first side and the upper part of the roof on the second side of the coal pillar 1 are hydraulically fracturing to cut off and depressurize the key strata 2 of the roof on both sides of the coal pillar 1.

[0076] During hydraulic fracturing, fracturing can be carried out in advance by arranging the first hydraulic fracturing hole 41 above the first and second sides of the coal pillar 1 during the mining of the working faces on both sides of the coal pillar 1.

[0077] For example, see Figure 2 and Figure 3 After determining the key roof stratum 2, the distance L1 between the key roof stratum 2 and the top of the coal pillar 1 is approximately 15m to 25m (e.g., 19m). Therefore, multiple first hydraulic fracturing holes 41 (including an uphill section 411 and a horizontal section 412) can be arranged within the key roof stratum 2. The first hydraulic fracturing holes 41 extend along the general excavation direction of the intake and return airways, and the multiple first hydraulic fracturing holes 41 are arranged at intervals in the vertical direction. The distance L5 between two adjacent first hydraulic fracturing holes 41 can be 6m to 1m. 0m (e.g., 8m), the distance between the uppermost first hydraulic fracturing hole 41 and the top of the coal pillar 1 is approximately 35m. Specifically, three first hydraulic fracturing holes 41 are arranged on each side of the width direction of the coal pillar 1. The horizontal distance L2 between the lowermost first hydraulic fracturing hole 41 and the side of the coal pillar 1 is approximately 8m, the horizontal distance L3 between the middle first hydraulic fracturing hole 41 and the side of the coal pillar 1 is approximately 10m, and the horizontal distance L4 between the uppermost first hydraulic fracturing hole 41 and the side of the coal pillar 1 is approximately 12m.

[0078] Alternatively, hydraulic fracturing can be carried out by arranging a second hydraulic fracturing hole 42 above the first and second sides.

[0079] See Figure 4 and Figure 5The second hydraulic fracturing hole 42 is divided into a fracturing section 422 and a non-fracturing section 421. The second hydraulic fracturing hole 42 is shorter in depth than the first hydraulic fracturing hole 41. The second hydraulic fracturing hole 42 is inclined towards the middle of the coal pillar 1 and the direction of roadway extension. The second hydraulic fracturing hole 42 is a generally straight hole. The fracturing section 422 accounts for more than 60% of the total depth of the second hydraulic fracturing hole 42 and extends into the key roof strata 2. For example, when the depth of the second hydraulic fracturing hole 42 is 50m, the length L6 of the fracturing section 422 is not less than 35m (e.g., 39m). The angle β between the axis of the second hydraulic fracturing hole 42 and the direction of roadway extension can be from 35 degrees to 50 degrees. In this embodiment, the distance between two adjacent second hydraulic fracturing holes 42 is 6m to 10m, for example, the distance between two adjacent second hydraulic fracturing holes 42 is 6m.

[0080] See Figures 6-9 In some embodiments, the step of arranging return airway 11 and intake airway 12 staggered in the height and width directions within the coal pillar 1 includes:

[0081] S201. Obtain stress monitoring data of coal pillar 1 and combine it with numerical simulation to determine the stress distribution in coal pillar 1.

[0082] S202. Identify the high-stress and low-stress zones in coal pillar 1. Return airway 11 and intake airway 12 avoid the high-stress zones, thereby improving construction safety and roadway stability.

[0083] S203. One of the return airway 11 and the intake airway 12 is arranged in the low stress zone of the roof adjacent to the coal pillar 1, and the other of the return airway 11 and the intake airway 12 is arranged in the low stress zone of the floor adjacent to the coal pillar 1. The return airway 11 and the intake airway 12 are spaced apart in the width direction of the coal pillar 1.

[0084] In this embodiment, the upper roadway is the return airway 11, located on the first side adjacent to the coal pillar 1. The lower roadway is the intake airway 12, located on the second side adjacent to the coal pillar 1. A first free coal pillar 13 is reserved between the upper roadway and the goaf 3 on the first side of the coal pillar 1, and a second free coal pillar 14 is reserved between the lower roadway and the goaf 3 on the second side of the coal pillar 1. This embodiment achieves a reasonable layout of the free roadways by reserving free coal pillars of corresponding widths, avoiding high stress peak areas and fundamentally improving the stress environment of the roadways.

[0085] The distance between the first and second sides of coal pillar 1 is greater than 30m, for example, 30m to 50m. The thickness of coal pillar 1 is greater than or equal to 10m, and the width of the first free-run coal pillar 13 and the second free-run coal pillar 14 is 8m to 10m. This embodiment can be applied to isolated coal pillars in extra-thick coal seams, improving the shortcomings and instability of roadway layout in related technologies, resulting in better overall structural stability and effectively mitigating the impact of stress within coal pillar 1 on roadway stability.

[0086] See Figures 6-9 In some embodiments, the step of depressurizing the middle region of coal pillar 1 in the upper roadway before excavating the lower roadway includes:

[0087] S301, such as Figure 6 and Figure 7 As shown, the upper roadway is excavated first at a predetermined distance. The predetermined distance is greater than or equal to 100m, for example, the predetermined distance is 100m, 120m, 145m, etc. When the predetermined distance is less than 100m, it is not conducive to subsequent blasting and decompression construction, and it is not possible to optimize the stress inside coal pillar 1 in advance, which is not conducive to the excavation construction of the lower roadway.

[0088] S302. Along the extension direction of the upper roadway, blasting pressure relief holes 5 are constructed sequentially in the upper roadway. The blasting pressure relief holes 5 extend toward the middle area of ​​the coal pillar 1 or the intake airway 12 and are used for blasting pressure relief.

[0089] S303, such as Figure 8 and Figure 9 As shown, construction of the lower roadway begins after the blasting and decompression work in the upper roadway reaches the second preset distance, along the extension direction of the upper roadway. The second preset distance is less than the first preset distance, and the second preset distance is greater than or equal to 50m. For example, the second preset distance is 50m, 55m, 75m, etc. When the second preset distance is less than 50m, stress optimization inside coal pillar 1 cannot be performed in advance, which is not conducive to the excavation of the lower roadway.

[0090] In subsequent construction, the upper tunnel will always be constructed a certain distance ahead of the lower tunnel. At the same depth, blasting and depressurization will be carried out first, and then the lower tunnel will be excavated until the construction of both the upper and lower tunnels is completed.

[0091] like Figure 6 As shown, further, in step S302, the depth of the blasting pressure relief hole 5 is... And satisfy:

[0092]

[0093] In the formula, The width between the first and second sides of coal pillar 1. The widths of the first free coal pillar 13 and the second free coal pillar 14 are given. The width of the upper passageway. The height of the upper tunnel. This refers to the thickness of the coal seam.

[0094] In this embodiment, the diameter of the blasting pressure relief hole 5 is 60mm to 100mm, the plugging length of the blasting pressure relief hole 5 is not less than 1 / 2 of the depth of the blasting pressure relief hole 5, and the charge density inside the blasting pressure relief hole 5 is not less than 1Kg / m. This ensures the effectiveness of blasting pressure relief, allowing the stress inside the coal pillar 1 to be fully relieved.

[0095] During blasting decompression operations, at least one blasting decompression hole 5 is spaced between each subsequent blasting decompression and the previous blasting decompression. This can improve operational efficiency, reduce construction costs, and ensure the decompression effect.

[0096] This invention optimizes the layout of roadways within isolated coal pillars and the excavation sequence of different roadways. It improves the stress environment of isolated coal pillars in extra-thick coal seams through hydraulic fracturing and roof cutting decompression technology, and supplements it with active support and grouting active modification, which greatly increases the self-stabilizing ability of the roadways. Under the premise of ensuring safety, it realizes the layout of double roadways in isolated coal pillars in extra-thick coal seams.

[0097] This invention optimizes the roadway layout and excavation sequence. It analyzes the stress state of coal pillar 1 based on its thickness and width, using theoretical analysis and numerical simulation to identify high-stress areas. The roadways are then positioned in low-stress areas, thus placing them within the stress-reduced zone of coal pillar 1 and avoiding high-stress peak areas. By optimizing the roadway layout and excavation sequence within coal pillar 1, the mutual interference between two roadways during traditional parallel excavation is avoided, improving roadway safety.

[0098] This invention actively improves the external stress environment of coal pillar 1: During the mining of the working faces on both sides of coal pillar 1, hydraulic fracturing and roof cutting are carried out in advance in the roadway near coal pillar 1 to actively cut off the stress transmission structure of the roof, fundamentally improving the stress environment of coal pillar 1, eliminating a major stress concentration source, allowing the stress of the overlying strata to be released more fully, fundamentally improving the stress environment of the roadway, and facilitating mine disaster prevention and mitigation.

[0099] In this embodiment of the invention, active pressure relief improves the internal stress environment of coal pillar 1. With the advance of the upper return airway 11, the stress inside the isolated coal pillar is further transferred. Through active blasting pressure relief, the internal stress distribution of coal pillar 1 is improved, providing a good stress environment for the excavation of intake airway 12, which is conducive to improving the safety of intake airway 12.

[0100] This invention optimizes the roadway support method. Compared with the existing support methods that use anchor bolts, anchor cables, and scaffolding, which are passive support methods, this invention adopts a combination of high-prestressed hollow grouting anchor cables, shotcreting, and grouting control. Furthermore, it designs the support for two roadways differently to achieve safe roadway excavation. Under the premise of ensuring support stability, the cost and construction efficiency are more controllable and more practical.

[0101] The following describes a specific embodiment of the present invention:

[0102] See Figure 10 and Figure 11 In a certain mine, the 1525 intake airway 62 and 1525 return airway 61 need to be located within an isolated coal pillar. The coal seam thickness is m=28m, and the coal pillar width is 50m. The 1513 goaf 63 and 1503 goaf 64 have already been mined. The 1525 intake airway 62 and 1525 return airway 61 need to be located within the coal pillar between the 1513 goaf 63 and 1503 goaf 64. The total length of the working face roadway 7 is approximately 2000m. The original section coal pillar size was 50m. The layout and principle of this isolated coal pillar roadway are as follows:

[0103] ①The reasonable double-roadway layout is determined by theoretical analysis, numerical simulation and field monitoring. The 61 coal pillar in the 1525 return airway is arranged on the right side of the coal pillar, along the roof, and is a small coal pillar 10m away from the 1503 goaf. The 62 coal pillar in the 1525 intake airway is arranged on the left side along the floor, and is a small coal pillar 10m away from the 1513 goaf.

[0104] ②Since the mining of the 1513 and 1503 goaf areas has been completed, the first hydraulic fracturing hole regional fracturing technology is used to perform regional fracturing on the key rock strata of the 1513 and 1503 roof. After the fracturing is completed, the 1525 return airway is excavated. After excavating a certain distance, blasting relief holes are drilled 1-1.5m along the sidewall of the 1525 return airway. The blasting relief holes are spaced 1m apart and explosives are charged at intervals. The length of the relief hole is calculated to be 29m according to the formula, the plugging length is 15m, and the explosive charge is 14kg.

[0105] ③ After blasting to relieve pressure in the center of the coal pillar along the 1525 return airway, the 1525 intake airway will start to be excavated again until it passes through the isolated coal pillar.

[0106] The arrangement and sequential excavation of the 1525 intake airway and the 1525 return airway resolved the mutual interference during parallel excavation. The initial excavation made full use of the stability of the coal seam roof. After blasting to relieve pressure, the excavation of the intake airway began. By changing the excavation sequence and blasting to relieve pressure, the superimposed stress effect of the intake airway was greatly improved, and the safety of the roadway excavation was enhanced.

[0107] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0108] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0109] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0110] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0111] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0112] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A roadway arrangement method in an isolated coal pillar of a coal seam, characterized in that, include: Obtain the key strata of the roof at the top of the coal pillar; The coal pillar has a first side and a second side in its width direction, and the key strata of the roof on the first side and the second side of the coal pillar are cut off to relieve pressure; The return airway and intake airway are arranged in a staggered manner in the height and width directions within the coal pillar; One of the return airway and the intake airway is adjacent to the roof and constructed as an upper roadway, and the other is adjacent to the floor and constructed as a lower roadway. The upper roadway is excavated a first predetermined distance before the lower roadway. After decompression work is carried out in the middle area of ​​the coal pillar in the upper roadway, the lower roadway is excavated. The upper roadway is arranged adjacent to the first side of the coal pillar, and the lower roadway is arranged adjacent to the second side of the coal pillar. A first free coal pillar is reserved between the upper roadway and the goaf on the first side of the coal pillar, and a second free coal pillar is reserved between the lower roadway and the goaf on the second side of the coal pillar. The distance between the first side and the second side of the coal pillar is greater than or equal to 30m, the thickness of the coal pillar is greater than or equal to 10m, and the width of the first free coal pillar and the second free coal pillar is 8m to 10m. The intake airway and the return airway are supported; The steps include: depressurizing the central region of the coal pillar in the upper roadway, followed by excavation of the lower roadway, comprising: Along the extension direction of the upper roadway, blasting pressure relief holes are constructed sequentially in the upper roadway. The blasting pressure relief holes extend toward the middle area of ​​the coal pillar or the intake airway and are used for blasting pressure relief. After the blasting and decompression work in the upper roadway reaches the second preset distance along the extension direction of the upper roadway, the construction of the lower roadway is carried out. The second preset distance is less than the first preset distance. The depth of the blasting pressure relief hole is , and satisfies: wherein is the width between the first and second sides of the coal pillar, is the width of the first and second free-standing coal pillars, is the width of the upper roadway, is the height of the upper roadway, is the coal seam thickness; The first preset distance is greater than or equal to 100m, and the second preset distance is greater than or equal to 50m; the diameter of the blasting pressure relief hole is 60mm to 100mm, the plugging length of the blasting pressure relief hole is not less than 1 / 2 of the depth of the blasting pressure relief hole, and the charge density in the blasting pressure relief hole is not less than 1Kg / m; during the blasting pressure relief operation, there is at least one blasting pressure relief hole between the last blasting pressure relief and the previous blasting pressure relief.

2. The roadway layout method in coal pillar island of coal seam according to claim 1, characterized in that, In the process of cutting off the roof and relieving pressure on the first and second sides of the coal pillar, hydraulic fracturing is performed on the key roof strata above the first side and the second side of the coal pillar to achieve hydraulic fracturing and roof cutting and pressure relief on both sides of the coal pillar.

3. The roadway arrangement method in coal pillar island of coal seam according to claim 2, characterized in that, Hydraulic fracturing is performed by arranging first hydraulic fracturing holes above the first and second sides of the coal pillar. These first hydraulic fracturing holes are arranged along the extension direction of the coal pillar. Alternatively, hydraulic fracturing can be carried out by arranging a second hydraulic fracturing hole above the first and second sides, the second hydraulic fracturing hole being inclined toward the middle of the coal pillar, and / or inclined toward the excavation direction of the intake airway and the return airway.

4. The method for arranging roadways in coal seam islands and coal pillars according to claim 1, characterized in that, The steps include arranging return airways and intake airways staggered in the height and width directions within the coal pillar, comprising: The stress monitoring data of the coal pillar is obtained and combined with numerical simulation to determine the stress distribution in the coal pillar; Identify the high-stress and low-stress zones within the coal pillar; One of a return airway and an intake airway is arranged in the low-stress zone adjacent to the roof of the coal pillar, and the other of a return airway and an intake airway is arranged in the low-stress zone adjacent to the floor of the coal pillar. The return airway and the intake airway are spaced apart in the width direction of the coal pillar.

5. The method for arranging roadways in coal seam islands and coal pillars according to any one of claims 1 to 4, characterized in that, The upper tunnel is a return air tunnel, and the lower tunnel is an intake air tunnel; And / or, the top of the upper tunnel is arranged along the roof plate, and the bottom of the lower tunnel is arranged along the floor plate; And / or, the top of the upper roadway is supported by prestressed anchor bolts or prestressed anchor cables, the sides of the upper roadway are supported by split grouting anchor cables and / or shotcrete, and the lower roadway is supported by a combination of full-section split grouting anchor cables and shotcrete. And / or, in the step of obtaining the key strata of the roof at the top of the coal pillar, by obtaining the roof and surrounding rock data information of the coal pillar, and judging the key strata of the roof at the top of the coal pillar based on the theory of mine pressure and strata control.

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