A method for preventing erosion by subsequent space grouting and filling in isolated working face

Abstract

The present invention provides a method for preventing impact of subsequent spatial grouting and filling in an isolated working face, including: obtaining goaf information corresponding to each adjacent goaf of an isolated coal pillar, and determining the full mining degree of the overburden corresponding to each adjacent goaf; determining the grouting filling method according to the full mining degree, and determining the grouting hole interval corresponding to each adjacent goaf according to the goaf information; grouting and filling each adjacent goaf based on the grouting hole interval and the grouting filling method; determining the width of the negative coal pillar, and staggering the transport lane and the return air lane in the bottom rock layer below the adjacent goaf to form a negative coal pillar. The present invention shares the overburden load of the isolated coal pillar by subsequent spatial grouting and filling in the adjacent goaf of the isolated coal pillar to reduce the risk of impact ground pressure. After grouting and filling, the negative coal pillar roadway is arranged so that the transport lane and the return air lane are in a low stress area. At the same time, the loose structure above the roadway roof can greatly attenuate the energy of the mine earthquake stress wave, ensuring the safe operation of the two lanes during mining.

Description

Technical Field

[0001] The invention relates to the technical field of coal mining, in particular to a method for preventing impact by subsequent space grouting and filling of an isolated island working face. Background Art

[0002] After mining, some coal mines will leave behind a large number of isolated coal pillars. Since both sides of the isolated coal pillars are goafs, the overlying rock strata are broken and moved on a large scale, making the stress concentration of the isolated working face much higher than that of the conventional working face, greatly increasing the impact hazard of the isolated working face and the difficulty of preventing and controlling rock burst. Existing rock burst prevention and control measures, such as top blasting, coal seam water injection, and drilling pressure relief, cannot fundamentally guarantee the safe recovery of coal resources in isolated coal pillars.

[0003] At present, for the mining of isolated working faces, the "negative coal pillar" roadway external staggered layout method can adjust the overburden structure, which can reduce the stress concentration of the roadway surrounding rock to a certain extent, thereby reducing the risk of roadway impact. However, the mining of isolated working faces still has the following problems: (1) Mining activities may cause the overburden structure of the working face and the goaf to be broken and unstable, which has a great risk of induced impact; (2) The gravity of the overburden strata on the isolated working face and the transfer load of the goaf on both sides are superimposed, and the high stress concentration makes the isolated working face at risk of overall instability type impact ground pressure, which cannot be fundamentally solved by existing methods; (3) The method of determining the position of the negative coal pillar roadway relies heavily on experience, and the layout design is not scientific and reasonable, which poses a potential threat to the stability of the surrounding rock of the negative coal pillar roadway under the floor of the goaf.

[0004] Therefore, the prior art has defects and needs to be improved and developed. Summary of the invention

[0005] The present application provides a method for preventing impact of space grouting and filling in an isolated working face, so as to solve the technical problems in the related art that the isolated working face has the risk of impact ground pressure and the surrounding rock stability of the negative coal pillar tunnel under the floor of the goaf is poor.

[0006] To achieve the above objectives, this application adopts the following technical solutions:

[0007] The first aspect of the present application provides a method for preventing erosion by subsequent space grouting and filling in an isolated working face, comprising:

[0008] Obtain goaf information corresponding to each adjacent goaf of the isolated coal pillar, and determine the full mining degree of the overburden corresponding to each adjacent goaf;

[0009] Determine the grouting filling method of each adjacent goaf according to the sufficient mining degree of the overburden corresponding to each adjacent goaf, and determine the grouting hole interval corresponding to each adjacent goaf according to the goaf information corresponding to each adjacent goaf;

[0010] Perform grouting filling on each adjacent goaf based on the grouting hole spacing and grouting filling method;

[0011] The width of the negative coal pillar is determined according to the basic information of the isolated working face collected in advance, and the transport tunnel and the return air tunnel are arranged in the bottom rock layer below the adjacent goaf according to the width of the negative coal pillar to form a negative coal pillar.

[0012] In one implementation, the goaf information includes: surface subsidence, burial depth, mining depth, mining height, coal seam inclination, collapse zone height, initial pressure step distance, goaf strike length, goaf dip width and coal seam spontaneous combustion tendency level; the basic information of the isolated island working face includes: overburden density of the isolated coal pillar, coal body cohesion, internal friction angle, friction coefficient of the contact surface between the coal seam and the roof and floor plates, stress concentration coefficient of the isolated coal pillar and the internal conditions of its adjacent goaf.

[0013] In one implementation, determining the sufficient mining degree of overburden corresponding to each adjacent goaf includes:

[0014] If the strike length or dip width of the adjacent goaf is greater than the preset multiple of the mining depth, the overburden structure of the adjacent goaf is fully mined;

[0015] If the strike length and dip width of adjacent goafs are both less than or equal to a preset multiple of the mining depth, the degree of full mining of the overburden structure of the adjacent goafs is insufficient mining.

[0016] In one implementation, the method of determining the grouting filling method of each adjacent goaf area according to the sufficient mining degree of the overburden corresponding to each adjacent goaf area includes:

[0017] When the overburden structure corresponding to the adjacent goaf is fully mined, the grouting filling method of the adjacent goaf is grouting filling of the collapse zone;

[0018] When the degree of full mining of the overburden structure corresponding to the adjacent goaf is not full mining, the grouting filling method of the adjacent goaf is separation layer high pressure grouting filling and collapse zone grouting filling.

[0019] In one implementation, the step of determining the grouting hole intervals corresponding to each adjacent goaf according to goaf information corresponding to each adjacent goaf includes:

[0020] The diffusion radius of the slurry material is obtained, and the interval of the grouting holes corresponding to each adjacent goaf is determined according to the diffusion radius of the slurry material and the goaf strike length and the goaf dip width of each adjacent goaf.

[0021] In one implementation, grouting is completed for each adjacent goaf based on the grouting hole spacing and grouting filling method, including:

[0022] Determine the grouting filling range of each adjacent goaf according to the initial pressure step distance;

[0023] Based on the grouting hole spacing and grouting filling method, grouting filling is completed for each adjacent goaf within the grouting filling range.

[0024] In one implementation, the step of completing grouting filling of adjacent goaf areas includes:

[0025] When grouting is performed on adjacent goafs where the overburden structure is fully mined, a ground hole is constructed from the surface above the middle of the grouting filling range of the adjacent goaf, and the final hole is constructed to the bottom plate of the goaf. Grouting is performed on the goaf to consolidate the collapsed overburden in a while-drilling manner;

[0026] When grouting filling is carried out on adjacent goafs where the degree of full mining of the overburden structure is not full mining, start from the surface above the middle of the grouting filling range of the adjacent goaf, drill a hole on the construction ground to below the unbroken main key layer, and carry out delamination grouting filling. After the grouting pressure is formed, stop grouting filling, continue drilling downward until the bottom plate of the goaf, and use the method of filling while drilling to fill the goaf with grouting.

[0027] In one implementation, the determining of the negative coal pillar width according to pre-collected basic information of the isolated working face includes:

[0028] According to the mining height, internal friction angle, friction coefficient of the contact surface between the coal seam and the roof and floor, stress concentration coefficient of the isolated coal pillar, bulk density of the overburden of the isolated coal pillar, burial depth and cohesion of the coal body, the width of the limit equilibrium zone of the isolated coal pillar is calculated;

[0029] The height of the transport tunnel, the height of the return air tunnel, and the angle between the contour line of the vertical stress change rate of the bottom plate of the isolated working face of 1% and the vertical line are obtained, and the negative coal pillar width is calculated based on the height of the transport tunnel, the height of the return air tunnel, the angle and the width of the limit equilibrium zone of the isolated coal pillar.

[0030] In one implementation, according to the width of the negative coal pillar, the transport lane and the return air lane are staggered in the floor rock layer below the adjacent goaf to form a negative coal pillar, and further includes:

[0031] If there is accumulated water and / or toxic and harmful gases inside the adjacent goaf, the accumulated water and / or toxic and harmful gases shall be completely discharged during the excavation of the transport tunnel and the return air tunnel.

[0032] In one implementation, after the transport lane and the return air lane are staggered in the floor rock layer below the adjacent goaf according to the width of the negative coal pillar to form a negative coal pillar, the method further includes:

[0033] Inspection holes are randomly arranged along the strike of adjacent goafs, and the inspection holes are drilled from the surface to the floor of the goaf;

[0034] Determine the grouting height based on the mining height, ground subsidence and collapse zone height, and observe by coring through inspection holes;

[0035] If the thickness of the grouting filling body reaches the grouting filling height, and no abnormal phenomenon of block falling or circulating fluid leakage occurs when the construction reaches the lower area of ​​the main key layer, the grouting filling quality is qualified;

[0036] If the thickness of the grouting filling body does not reach the grouting filling height, or if abnormal block falling or circulating fluid leakage occurs when the construction reaches the lower area of ​​the main key layer, additional grouting filling is carried out.

[0037] Beneficial effects of the present invention: The embodiment of the present application obtains goaf information corresponding to each adjacent goaf of the isolated coal pillar, and determines the degree of full mining of the overburden corresponding to each adjacent goaf; determines the grouting filling method of each adjacent goaf according to the degree of full mining of the overburden corresponding to each adjacent goaf, and determines the grouting hole interval corresponding to each adjacent goaf according to the goaf information corresponding to each adjacent goaf; performs grouting filling on each adjacent goaf based on the grouting hole interval and grouting filling method; determines the negative coal pillar width according to the pre-collected basic information of the isolated working face, and arranges the transport lane and the return air lane in the floor rock layer below the adjacent goaf according to the negative coal pillar width to form a negative coal pillar. The present invention reduces the overburden load of the isolated coal pillar by subsequent spatial grouting filling of the goaf adjacent to the isolated coal pillar, so as to reduce the risk of rock burst. After grouting filling, negative coal pillar tunnels are arranged so that the transport tunnels and return air tunnels are in the stress reduction zone. At the same time, the loose structure of the goaf above the roof of the negative coal pillar tunnel can greatly attenuate the energy of the mine earthquake stress wave transmitted from the top of the tunnel, avoid the formation of the impact source, and ensure the safe operation of the transport tunnel and return air tunnel during mining. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0039] Figure 1 It is a flow chart of a preferred embodiment of the method for preventing erosion by subsequent space grouting and filling of an isolated working face in the present invention.

[0040] Figure 2 It is a schematic diagram of the subsequent space grouting filling and negative coal pillar tunnel arrangement of the isolated island working face of the present invention.

[0041] Figure 3 It is a schematic diagram of the arrangement of grouting holes and inspection holes according to an embodiment of the present invention.

[0042] Description of reference numerals:

[0043] 1. Goaf on the east side; 2. Grouting filling body; 3. Bottom rock layer; 4. Transport tunnel; 5. Lower exit of cutting eye; 6. Isolated working face; 7. Coal seam; 8. Upper exit of cutting eye; 9. Return air tunnel; 10. Goaf on the west side; 11. Inspection hole; 12. Grouting hole; 13. Slurry; 14. Main key layer. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the present invention clearer and more specific, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0045] The present invention proposes a method for coordinated prevention and control of rock burst through subsequent spatial grouting filling of an isolated working face and arrangement of negative coal pillar tunnels, which can ensure the safe and efficient recovery of isolated island coal resources and is of great significance for promoting the sustainable development of coal resources and meeting the growing energy demand.

[0046] See also Figure 1 The method for preventing erosion by subsequent space grouting and filling of an isolated working face according to an embodiment of the present invention comprises the following steps:

[0047] Step S100, obtaining goaf information corresponding to each adjacent goaf of the isolated coal pillar, and determining the sufficient mining degree of the overburden corresponding to each adjacent goaf.

[0048] In one embodiment of the present application, the goaf information includes: surface subsidence, burial depth, mining depth, mining height, coal seam inclination, collapse zone height, initial pressure step distance, goaf strike length, goaf dip width and coal seam spontaneous combustion tendency level.

[0049] Specifically, for each adjacent goaf of the isolated coal pillar, the goaf information of each adjacent goaf is first collected, including: surface subsidence S, burial depth H and mining depth H0, mining height M, coal seam inclination α, collapse zone height h, initial pressure step d, goaf strike length L and dip width W, and coal seam spontaneous combustion tendency level, so as to facilitate the subsequent judgment of the sufficient mining degree of the overburden in the adjacent goaf.

[0050] In one embodiment of the present application, the degree of sufficient mining of the overburden structure corresponding to each adjacent goaf is determined, including: if the goaf strike length or the goaf dip width of adjacent goafs is greater than a preset multiple of the mining depth, then the degree of sufficient mining of the overburden structure of the adjacent goafs is sufficient mining; if the goaf strike length and the goaf dip width of adjacent goafs are both less than or equal to a preset multiple of the mining depth, then the degree of sufficient mining of the overburden structure of the adjacent goafs is insufficient mining.

[0051] Specifically, the preset multiple is 1.2, that is, to judge the degree of sufficient mining on both sides of the isolated working face, if the strike length L of the goaf of the isolated working face or the dip width W of the goaf is greater than 1.2H0, then the overburden structure above the goaf on this side of the isolated working face is fully mined, otherwise the overburden structure is not fully mined, and the main key layer is not broken. By comparing the relationship between the strike length of the goaf and the dip width of the goaf and the mining depth, the embodiment of the present application can determine the degree of sufficient mining of adjacent goafs, and then select a suitable grouting filling method.

[0052] like Figure 1 As shown, the subsequent space grouting and anti-collision method for the isolated island working face also includes the following steps:

[0053] Step S200, determining the grouting filling method of each adjacent goaf according to the sufficient mining degree of the overburden corresponding to each adjacent goaf, and determining the grouting hole interval corresponding to each adjacent goaf according to the goaf information corresponding to each adjacent goaf.

[0054] In one embodiment of the present application, the grouting filling method of each adjacent goaf is determined according to the degree of full mining of the overlying strata corresponding to each adjacent goaf, including: when the degree of full mining of the overlying strata structure corresponding to the adjacent goaf is full mining, the grouting filling method of the adjacent goaf is collapse zone grouting filling; when the degree of full mining of the overlying strata structure corresponding to the adjacent goaf is insufficient mining, the grouting filling method of the adjacent goaf is separation layer high-pressure grouting filling and collapse zone grouting filling.

[0055] Specifically, the embodiment of the present application reduces the advanced support stress generated during mining of the isolated working face through grouting filling. The filling body and the isolated coal pillar in front of the working face share the load, thereby reducing the stress concentration degree of the isolated working face and significantly reducing the risk of rock burst in the isolated working face.

[0056] In one embodiment of the present application, the grouting hole intervals corresponding to each adjacent goaf are determined based on the goaf information corresponding to each adjacent goaf, including: obtaining the diffusion radius of the slurry material, and determining the grouting hole intervals corresponding to each adjacent goaf based on the diffusion radius of the slurry material and the goaf strike length and goaf dip width of each adjacent goaf.

[0057] Specifically, the diffusion radius of the slurry material is determined by the properties of the slurry material itself. The object of grouting in the collapsed zone is the collapsed overburden within 2d of the isolated island coal pillar.

[0058] like Figure 1 As shown, the subsequent space grouting and anti-collision method for the isolated island working face also includes the following steps:

[0059] Step S300: completing grouting filling for each adjacent goaf based on the grouting hole spacing and grouting filling method.

[0060] In one embodiment of the present application, grouting filling is completed for each adjacent goaf based on the grouting hole spacing and the grouting filling method, including: determining the grouting filling range of each adjacent goaf according to the initial pressure step distance; based on the grouting hole spacing and the grouting filling method, completing grouting filling for each adjacent goaf within the grouting filling range.

[0061] In one embodiment of the present application, grouting filling is completed for each adjacent goaf, including:

[0062] When grouting is performed on adjacent goafs where the overburden structure is fully mined, a ground hole is constructed from the surface above the middle of the grouting filling range of the adjacent goaf, and the final hole is constructed to the bottom plate of the goaf. Grouting is performed on the goaf to consolidate the collapsed overburden in a while-drilling manner;

[0063] When grouting filling is carried out on adjacent goafs where the degree of full mining of the overburden structure is not full mining, start from the surface above the middle of the grouting filling range of the adjacent goaf, drill a hole on the construction ground to below the unbroken main key layer, and carry out delamination grouting filling. After the grouting pressure is formed, stop grouting filling, continue drilling downward until the bottom plate of the goaf, and use the method of filling while drilling to fill the goaf with grouting.

[0064] The slurry materials used for grouting filling in the embodiment of the present application can be selected from cement and fly ash, or modified magnesium slag and fly ash.

[0065] The embodiment of the present application targets the overburden structures with different mining degrees on the upper part of the goaf on both sides of the isolated working face, performs delamination grouting and collapse zone grouting for the non-fully mined overburden structures, and performs collapse zone grouting for the fully mined overburden structures, wherein the delamination grouting can compact the voids in the goaf, and form a compaction zone in the middle of the goaf, which can be carried together with the coal pillars and collapsed overburden filling bodies on both sides of the isolated working face; the collapse zone grouting can consolidate the collapsed overburden and support it, preventing the activation of the overburden structure in the adjacent goaf of the isolated working face during mining, and the coordinated breaking of the overburden with the current isolated working face to cause mine earthquakes and large-scale surface subsidence and other disasters, while the advanced support stress generated during the mining of the working face and the stress concentration degree of the isolated working face will be greatly reduced, which greatly reduces the surrounding rock control cost during the mining of the isolated working face, and is conducive to ensuring safe, green and efficient mining of the isolated working face.

[0066] like Figure 1 As shown, the subsequent space grouting and anti-collision method for the isolated island working face also includes the following steps:

[0067] Step S400, determine the negative coal pillar width according to the pre-collected basic information of the isolated working face, and arrange the transport tunnel and the return air tunnel in the floor rock layer below the adjacent goaf according to the negative coal pillar width to form a negative coal pillar.

[0068] Specifically, the transport tunnel and the return air tunnel are staggered in the bottom rock layer below the goaf on both sides of the isolated working face, forming a "negative coal pillar" with the transport tunnel of the previous working face and the return air tunnel of the next working face.

[0069] In one embodiment of the present application, the basic information of the isolated working face includes: the isolated coal pillar overburden density, coal body cohesion, internal friction angle, friction factor of the contact surface between the coal seam and the roof and floor, stress concentration coefficient of the isolated coal pillar and the internal conditions of the adjacent goaf. Specifically, the isolated coal pillar overburden density γ, coal body cohesion c and internal friction angle are collected in advance. The friction factor f between the contact surface of the coal seam and the roof and floor, the stress concentration coefficient of the isolated coal pillar and the internal conditions of the adjacent goaf. Specifically, the internal conditions of the adjacent goaf refer to whether there is water accumulation and toxic and harmful gases in the goaf.

[0070] In one embodiment of the present application, the width of the negative coal pillar is determined based on the basic information of the isolated working face collected in advance, including: calculating the width of the limit equilibrium zone of the isolated coal pillar based on the mining height, internal friction angle, friction coefficient of the contact surface between the coal seam and the roof and floor plates, stress concentration coefficient of the isolated coal pillar, cover rock density, burial depth and coal body cohesion; obtaining the height of the transport lane, the height of the return air lane and the angle between the contour line of the vertical stress change rate of 1% of the bottom plate of the isolated working face and the vertical line, and calculating the negative coal pillar width based on the height of the transport lane, the height of the return air lane, the angle and the width of the limit equilibrium zone of the isolated coal pillar.

[0071] Specifically, the horizontal distance between the left side of the transport tunnel of the previous strip mining working face and the left side of the return air tunnel of the current island working face, that is, the negative coal pillar width:

[0072] l≥(z1+z2)tanθ-x0

[0073] Where z1 is the height of the transport lane, z2 is the height of the return air lane; θ is the angle between the contour line of the vertical stress change rate of the bottom plate of the isolated working face of 1% and the vertical line, which is determined according to the numerical simulation results; x0 is the width of the limit equilibrium zone of the isolated coal pillar, which is calculated according to the following formula:

[0074]

[0075] Among them, the determination of the width of the negative coal pillar can ensure that the transport tunnel and the return air tunnel are arranged in the stress reduction area and the relatively balanced stress area of ​​the bottom plate, thereby reducing the difficulty of tunnel maintenance.

[0076] Based on the arrangement of negative coal pillars in the tunnels of the isolated working face, the embodiment of the present application provides a method for determining the width range of negative coal pillars, which can enable the negative coal pillar tunnels to be located in the stress reduction zone of the rock mass that has been fully unloaded below the goaf, and the stress of the tunnel surrounding rock changes evenly, which can improve the tunnel support conditions and reduce the tunnel maintenance costs.

[0077] In one embodiment of the present application, the transport tunnel and the return air tunnel are staggered in the bottom rock layer below the adjacent goaf according to the width of the negative coal pillar to form a "negative coal pillar", and also include: if there is accumulated water and / or toxic and harmful gases inside the adjacent goaf, then all the accumulated water and / or toxic and harmful gases will be discharged during the excavation of the transport tunnel and the return air tunnel.

[0078] In one embodiment of the present application, after completing the grouting filling of each adjacent goaf based on the grouting hole spacing and the grouting filling method, it also includes: randomly arranging inspection holes along the strike of adjacent goafs, and the inspection holes are constructed from surface drilling to the bottom plate of the goaf; determining the grouting filling height according to the mining height, surface subsidence and collapse zone height, and coring through the inspection holes for observation; if the thickness of the grouting filling body reaches the grouting filling height, and no abnormal phenomenon of block falling or circulating fluid leakage occurs when the construction reaches the lower area of ​​the main key layer, the grouting filling quality is qualified; if the thickness of the grouting filling body does not reach the grouting filling height, or abnormal phenomenon of block falling or circulating fluid leakage occurs when the construction reaches the lower area of ​​the main key layer, supplementary grouting filling is performed.

[0079] Specifically, after the grouting work is completed, inspection holes are randomly arranged along the strike within the adjacent goaf of the isolated working face, and the drilling is constructed from the surface to the floor of the goaf. Through observation of drilling cores, if the thickness of the grouting filling body reaches the grouting filling height, and there is no abnormal phenomenon of block falling or circulating fluid leakage when the construction reaches the lower area of ​​the main key layer, it indicates that the grouting filling quality is qualified. Otherwise, additional grouting is carried out near the inspection hole.

[0080] The calculation formula for the grouting filling height is [MS-(0.03-0.05)h], and the inspection holes are arranged at intervals along the direction of the goaf to ensure that the number of inspection holes is 2%-5% of the number of grouting holes.

[0081] In the embodiment of the present application, the vertical distance z1 between the roof of the negative coal pillar roadway and the goaf above it ranges from 3 to 5m. If there is water accumulation or spontaneous combustion tendency not less than level II in the goaf on both sides of the isolated working face, the vertical distance between the roof of the negative coal pillar roadway and the goaf above is at least 4m, which can ensure the support and reinforcement effect and stability of the roadway roof rock during the excavation of the transport roadway and the return air roadway and the mining of the isolated working face. The vertical distance between the top plate of the upper and lower exits of the cut eye and the bottom plate of the goaf on one side of the corresponding isolated working face is not less than 2.5m, which can ensure the support effect of the upper and lower exits of the cut eye during the construction of the cut eye even if there is water accumulation and the spontaneous combustion period is short in the goaf on both sides of the isolated working face. The negative coal pillar roadway is arranged in an external staggered form. At the end of the transport roadway, a lower exit of the cut eye is constructed perpendicular to the transport roadway towards the coal seam. After the coal seam is exposed, the cut eye section is continued to be constructed along the direction of the coal seam bottom plate. At the end of the return air roadway, an upper exit of the cut eye is constructed perpendicular to the return air roadway towards the coal seam. After the upper exit of the cut eye is constructed to expose the coal seam, the upper exit of the cut eye is connected with the cut eye section to complete the external staggered layout of the negative coal pillar roadway.

[0082] A specific embodiment is listed below for illustration.

[0083] In the early stage of mining, a certain mine adopted strip skipping, leaving many isolated coal pillars. Conventional mining with coal pillars was adopted in the isolated working face, and severe rock burst occurred during the mining process, which not only caused damage to the transport tunnel and the return air tunnel, but also the impact of the coal wall on the isolated working face caused the support in the working face to move backward, and the front beam of the support and the jack of the guard plate were damaged in large quantities, causing many people to be injured. Other isolated working faces of the mine adopted the method of the present invention to carry out grouting filling and negative coal pillar mining to prevent rock burst, such as Figure 2 As shown:

[0084] Step 1: Collect basic information of the isolated working face and goaf information of the goaf strips on both sides.

[0085] Surface subsidence S of goaf 1 on the east side of isolated working face 6 e The surface subsidence of the western goaf is 800 mm. w The coal seam 7 is buried at a depth of 280m, with an average mining depth H0 of 400m, a mining height M of 5m, an average inclination angle α of 2°, and a spontaneous combustion tendency level of II. The strike length L of the east goaf 1 is 800m, and the width W is 630m. The strike length L of the west goaf 10 is 780m, and the inclination width W is 110m. At the same time, there is water accumulation in the strip goafs on both sides of the isolated working face 6, and there is no toxic or harmful gas. The average bulk density γ of the overburden of the isolated working face 6 is 26kN / m 3The cohesion c of coal seam 7 is 1.8MPa, the internal friction angle φ is 25°, the friction coefficient f of the contact surface between the coal seam and the roof and floor plates is 0.2, the height of the main key layer 14 of the isolated working face is 175m, the height of the collapse zone of the east strip goaf area h is 15m, and the initial collapse step distance of the basic top is 33m, the height of the collapse zone of the west strip goaf area is 13m, and the initial collapse step distance of the basic top is 25m.

[0086] Step 2: Determine the degree of sufficient mining of the overburden in the goaf on both sides of the isolated working face.

[0087] The length L and width W of goaf 1 on the east side of the isolated working face are both greater than 1.2H0, which shows that the overburden structure above goaf 1 on the east side of the isolated working face is fully mined; for goaf 10 on the west side of the isolated working face, the width does not reach 1.2H0, so the overburden structure of goaf 10 on the west side is not fully mined, the main key layer 14 has not been broken, and there is a delamination area between it and the water-conducting fracture zone.

[0088] Step 3: Grouting is performed on the subsequent space of the goaf, grouting is performed on the collapsed zone on the fully mined side, and grouting is performed on the abscission layer and collapsed zone on the non-fully mined side.

[0089] like Figure 3 As shown in the figure, for the fully mined overburden structure on the east side of the isolated island working face 6, a grouting hole 12 is drilled from the upper surface construction ground at a position 35m away from the isolated island coal pillar in the goaf, and the final hole is constructed to the bottom plate of the goaf. The grouting holes are arranged every 100m in parallel to the direction of the goaf, with a total of 8 grouting holes. The grouting filling slurry material is a mixture of cement and fly ash, and the slurry diffusion radius is 100m. The collapsed overburden within a width of 70m on the side of the east goaf 1 close to the isolated island coal pillar is grouting and consolidation; for the non-fully mined overburden structure on the west side of the isolated island working face, the overburden structure is mined from the west side of the goaf. Surface construction is carried out above the middle of area 10. Grouting holes 12 are drilled on the ground to below the unbroken main key layer 14. A grouting hole is arranged every 100m at a distance of 25m from the isolated coal pillar and parallel to the direction of the goaf. A total of 8 grouting holes are used for stratum grouting filling. The material of the grouting filling slurry 13 is a mixture of cement and fly ash, and the slurry diffusion radius is 100m. After the grouting pressure is formed, the grouting filling is stopped, and drilling continues downward until the bottom of the coal seam 7. The way of filling while drilling is adopted to grout the collapsed overburden within a width of 50m on the side of the west goaf 10 close to the isolated coal pillar.

[0090] Step 4: Arrange the negative coal pillar tunnel and discharge the accumulated water and harmful gases when digging the tunnel.

[0091] The transport tunnel 4 and the return air tunnel 9 are arranged outwardly in the bottom rock layer 3 below the goaf on both sides of the isolated working face 6, forming a "negative coal pillar" with the transport tunnel of the previous working face and the return air tunnel of the next working face; during the excavation of the transport tunnel 4 and the return air tunnel 9, advanced exploration and water discharge operations are used to drain the accumulated water in the goaf on both sides of the isolated working face 6.

[0092] Step 5: Arrange inspection holes along the direction of the goaf on both sides of the isolated working face to determine the quality of grouting filling and whether additional grouting is needed.

[0093] Inspection holes 11 are randomly arranged along the strike within the goaf on both sides of the isolated working face 6, with one inspection hole 11 arranged in each of the east goaf 1 and the west goaf 10. The holes are all drilled from the surface to the bottom plate of the goaf. Through core drilling observation, it was found that the thickness of the grouting filling body 2 in the goaf 1 on the east side of the isolated working face reached 2.48m, which is basically consistent with the calculated grouting filling height. When the upper surface drilling of the goaf 10 on the west side of the isolated working face reached the lower area of ​​the main key layer 14, no abnormal phenomenon of block falling or circulating fluid leakage occurred, and the height of the grouting filling body in the west goaf 10 was 4.5m. The subsequent spatial grouting filling quality of the goafs on both sides of the isolated working face was qualified.

[0094] In this embodiment, due to the presence of water in the goaf on both sides of the isolated working face 6 and the small inclination of the coal seam, the vertical distance z1 between the roof of the negative coal pillar tunnel and the goaf above is 5m, and the vertical distance between the roof of the upper outlet 8 and the lower outlet 5 of the cutting eye and the bottom plate of the goaf on one side of the corresponding isolated working face is 3m; the height z2 of the transport tunnel 4 and the return air tunnel 9 is designed to be 4m, and the numerical simulation results are analyzed, and it is finally obtained that the width of the negative coal pillar is at least 16.5m, and the transport tunnel 4 and the return air tunnel 9 are arranged according to the negative coal pillar width of 17m.

[0095] After the grouting filling work is completed, the negative coal pillar tunnel is laid out, and the lower outlet 5 of the cut eye is constructed at the end of the transport tunnel 4 perpendicular to the transport tunnel 4 toward the coal seam 7. After exposing the coal seam 7, the cut eye section is continued to be constructed along the direction of the bottom rock layer 3, and the upper outlet 8 of the cut eye is constructed at the end of the return air tunnel 9 perpendicular to the return air tunnel 9 toward the coal seam 7. After constructing the upper outlet 8 of the cut eye to expose the coal seam 7, the upper outlet 8 of the cut eye is connected with the cut eye section, and the layout of the negative coal pillar tunnel is completed.

[0096] The isolated working face 6 was mined, and rock burst monitoring was carried out for eight consecutive months, and no rock burst events occurred. No pressure relief measures were taken on the isolated working face 6 during the mining period. The monitoring support pressures of the transport tunnel 4 and the return air tunnel 9 were small and relatively balanced, indicating that the proposed grouting filling and negative coal pillar mining collaborative anti-rock burst method ensured the safe and efficient mining of the isolated working face 6.

[0097] In summary, the present invention discloses a method for subsequent spatial grouting and anti-collision of an isolated working face, comprising: obtaining goaf information corresponding to each adjacent goaf of an isolated coal pillar, and determining the degree of sufficient mining of the overburden corresponding to each adjacent goaf; determining the grouting filling method of each adjacent goaf according to the degree of sufficient mining of the overburden corresponding to each adjacent goaf, and determining the grouting hole spacing corresponding to each adjacent goaf according to the goaf information corresponding to each adjacent goaf; grouting and filling each adjacent goaf based on the grouting hole spacing and the grouting filling method; determining the negative coal pillar width according to the basic information of the isolated working face collected in advance, and staggering the transport lane and the return air lane in the bottom rock layer below the adjacent goaf according to the negative coal pillar width to form a "negative coal pillar". The present invention arranges negative coal pillar tunnels after grouting filling, so that the transport tunnel and the return air tunnel are in the stress reduction zone. At the same time, the loose structure of the goaf above the roof of the negative coal pillar tunnel can greatly attenuate the energy of the mine earthquake stress wave transmitted from the top of the tunnel, avoid the formation of the impact source, and ensure the safe operation of the transport tunnel and the return air tunnel during mining.

[0098] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preventing erosion by subsequent space grouting and filling in an isolated island working face, characterized in that: include: Obtain goaf information corresponding to each adjacent goaf of the isolated coal pillar, and determine the full mining degree of the overburden corresponding to each adjacent goaf; Determine the grouting filling method of each adjacent goaf according to the sufficient mining degree of the overburden corresponding to each adjacent goaf, and determine the grouting hole interval corresponding to each adjacent goaf according to the goaf information corresponding to each adjacent goaf; Perform grouting filling on each adjacent goaf based on the grouting hole spacing and grouting filling method; Determine the width of the negative coal pillar according to the basic information of the isolated working face collected in advance, and arrange the transport lane and the return air lane in the floor rock layer below the adjacent goaf according to the width of the negative coal pillar to form a negative coal pillar; Determine the sufficient mining degree of the overburden corresponding to each adjacent goaf, including: If the strike length or dip width of the adjacent goaf is greater than the preset multiple of the mining depth, the overburden structure of the adjacent goaf is fully mined; If the strike length and dip width of the adjacent goaf are both less than or equal to the preset multiple of the mining depth, the full mining degree of the overburden structure of the adjacent goaf is insufficient mining; The grouting filling method of each adjacent goaf is determined according to the sufficient mining degree of the overburden corresponding to each adjacent goaf, including: When the overburden structure corresponding to the adjacent goaf is fully mined, the grouting filling method of the adjacent goaf is grouting filling of the collapse zone; When the degree of full mining of the overburden structure corresponding to the adjacent goaf is not full mining, the grouting filling method of the adjacent goaf is separation layer high pressure grouting filling and collapse zone grouting filling.

2. The method for preventing erosion by subsequent space grouting and filling at an isolated island working face according to claim 1 is characterized in that: The goaf information includes: surface subsidence, burial depth, mining depth, mining height, coal seam inclination, collapse zone height, initial pressure step distance, goaf strike length, goaf dip width and coal seam spontaneous combustion tendency level; the basic information of the isolated island working face includes: overburden density of the isolated coal pillar, coal body cohesion, internal friction angle, friction coefficient of the contact surface between the coal seam and the roof and floor plates, stress concentration coefficient of the isolated coal pillar and the internal conditions of its adjacent goaf.

3. The method for preventing erosion by subsequent space grouting and filling at an isolated island working face according to claim 2 is characterized in that: The step of determining the grouting hole intervals corresponding to each adjacent goaf according to the goaf information corresponding to each adjacent goaf includes: The diffusion radius of the slurry material is obtained, and the interval of the grouting holes corresponding to each adjacent goaf is determined according to the diffusion radius of the slurry material and the goaf strike length and the goaf dip width of each adjacent goaf.

4. The method for preventing erosion by subsequent space grouting filling on an isolated island working face according to claim 1 is characterized in that: Based on the grouting hole spacing and grouting filling method, grouting filling is completed for each adjacent goaf, including: Determine the grouting filling range of each adjacent goaf according to the initial pressure step distance; Based on the grouting hole spacing and grouting filling method, grouting filling is completed for each adjacent goaf within the grouting filling range.

5. The method for preventing erosion by subsequent space grouting filling of isolated island working face according to claim 4 is characterized in that: The grouting filling of each adjacent goaf area includes: When grouting is performed on adjacent goafs where the overburden structure is fully mined, a ground hole is constructed from the surface above the middle of the grouting filling range of the adjacent goaf, and the final hole is constructed to the bottom plate of the goaf. Grouting is performed on the goaf to consolidate the collapsed overburden in a while-drilling manner; When grouting filling is carried out on adjacent goafs where the degree of full mining of the overburden structure is not full mining, start from the surface above the middle of the grouting filling range of the adjacent goaf, drill a hole on the construction ground to below the unbroken main key layer, and carry out delamination grouting filling. After the grouting pressure is formed, stop grouting filling, continue drilling downward until the bottom plate of the goaf, and use the method of filling while drilling to fill the goaf with grouting.

6. The method for preventing erosion by subsequent space grouting filling on an isolated island working face according to claim 2 is characterized in that: Determining the negative coal pillar width according to the pre-collected basic information of the isolated working face includes: According to the mining height, internal friction angle, friction coefficient of the contact surface between the coal seam and the roof and floor, stress concentration coefficient of the isolated coal pillar, bulk density of the overburden of the isolated coal pillar, burial depth and cohesion of the coal body, the width of the limit equilibrium zone of the isolated coal pillar is calculated; The height of the transport tunnel, the height of the return air tunnel, and the angle between the contour line of the vertical stress change rate of the bottom plate of the isolated working face of 1% and the vertical line are obtained, and the negative coal pillar width is calculated based on the height of the transport tunnel, the height of the return air tunnel, the angle and the width of the limit equilibrium zone of the isolated coal pillar.

7. The method for preventing erosion by subsequent space grouting and filling at an isolated island working face according to claim 2 is characterized in that: According to the width of the negative coal pillar, the transport lane and the return air lane are arranged in the floor rock layer below the adjacent goaf to form a negative coal pillar, including: If there is accumulated water and / or toxic and harmful gases inside the adjacent goaf, the accumulated water and / or toxic and harmful gases shall be completely discharged during the excavation of the transport tunnel and the return air tunnel.

8. The method for preventing erosion by subsequent space grouting and filling in an isolated island working face according to claim 1 is characterized in that: After the transport lane and the return air lane are arranged in the floor rock layer below the adjacent goaf according to the width of the negative coal pillar to form a negative coal pillar, the method further includes: Inspection holes are randomly arranged along the strike of adjacent goafs, and the inspection holes are drilled from the surface to the floor of the goaf; Determine the grouting height based on the mining height, ground subsidence and collapse zone height, and observe by coring through inspection holes; If the thickness of the grouting filling body reaches the grouting filling height, and no abnormal phenomenon of block falling or circulating fluid leakage occurs when the construction reaches the lower area of ​​the main key layer, the grouting filling quality is qualified; If the thickness of the grouting filling body does not reach the grouting filling height, or if abnormal block falling or circulating fluid leakage occurs when the construction reaches the lower area of ​​the main key layer, additional grouting filling is carried out.

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