A gangue cemented downward filling coal mining method with three-in-one extremely close-range coal seams

Abstract

The present invention discloses a gangue cementation downward filling coal mining method of a coal seam at very close distance, firstly, the upper goaf is filled with gangue, and pipes are buried in the gangue piles at different filling heights for grouting to form a stable gangue cementation body, thereby reducing the creep settlement of gangue; drilling holes on the construction ground and lowering grouting flower pipes to avoid grouting in the separation layer, seal the cracks between the overburden stratum and the coal pillar, and improve the strength of the surrounding rock; grouting and filling are performed in the incomplete filling area of ​​the upper goaf until the overburden stratum, the filling body and the bottom plate of the upper coal seam form a stable rock mass, thereby providing strong support for the mining of the lower coal seam and the filling of the goaf. The present invention realizes the gangue cementation filling mining of the lower coal seam at very close distance under the protection of the artificial strong roof constructed by the trinity of the overburden rock, the filling body and the bottom plate of the upper goaf, and efficiently disposes of the solid waste of the coal mine, effectively controls the surface subsidence, and liberates the resources of the coal seam at very close distance.

Description

Technical Field

[0001] The invention relates to the technical field of coal mining, and in particular to a gangue cemented descending filling coal mining method of a coal seam in an extremely close distance. Background Art

[0002] In the mining of coal resources, gangue cementing and filling mining can control surface subsidence to a certain extent, and effectively dispose of coal mine solid wastes such as coal gangue and fly ash. For extremely close coal seams, the downward mining method is usually adopted. Due to the small distance between coal seams, the mutual influence between the upper and lower coal seams is significant: before the mining of the lower coal seam in the extremely close coal seam, the integrity of the roof has been damaged by the mining of the upper coal seam, thus affecting the gangue cementing and filling effect of the lower coal seam; field production experience shows that the roof is prone to roof collapse and roof leakage accidents during the downward mining of extremely close coal seams, which seriously threatens the safe mining of the lower coal seam. In view of the above-mentioned problems of the downward mining method, it is urgent to seek an efficient and safe gangue cementing and downward filling coal mining method for extremely close coal seams, so as to improve the gangue cementing and filling effect of close coal seams and liberate the resources of close coal seams. Summary of the invention

[0003] The purpose of the present invention is to provide a three-in-one gangue cemented downward filling coal mining method for extremely close coal seams, which provides a safe mining environment for the mining of the lower coal seams by filling the upper goaf with gangue and grouting and solidifying it.

[0004] To achieve the above purpose, the present invention provides a three-in-one gangue cemented downward filling coal mining method in a very close distance coal seam, comprising the following steps:

[0005] Step S1, firstly, the upper coal seam of the extremely close coal seam is mined according to the production design to form a goaf, a row of grouting pipes is laid at the bottom of the goaf, and then the goaf is filled with gangue, and multiple rows of grouting pipes are buried at different heights of the gangue pile, and the spacing between each row of grouting pipes gradually increases from the bottom of the goaf to the top, and grouting operations are first performed through a row of grouting pipes at the bottom of the goaf to grout the cracks in the floor of the upper coal seam, and then grouting operations are performed step by step on the upper row of grouting pipes, and finally a stable gangue cement body is formed to reduce the creep settlement of the gangue;

[0006] Step S2, drilling a plurality of coal pillar fissure grouting boreholes and overburden rock fissure grouting boreholes from the ground surface, wherein the bottom end of the coal pillar fissure grouting borehole is located at the bottom of the coal pillar, and the bottom end of the overburden rock fissure grouting borehole is located in the goaf space after the upper coal seam is mined; placing grouting flower pipes under the coal pillar fissure grouting boreholes and the overburden rock fissure grouting boreholes according to the height of the fissure zone, avoiding separation, grouting and plugging the fissures in the overburden rock stratum and the coal pillar, and improving the surrounding rock strength of the upper goaf;

[0007] Step S3, increasing the grouting pressure of the overburden stratum fissure grouting drilling hole until the slurry breaks through the grouting plug at the bottom end of the borehole, and a cementing paste is formed in the incomplete filling area of ​​the upper goaf, until the overburden stratum of the upper coal seam, the filling body of the goaf and the bottom plate form a stable rock mass, providing favorable roof conditions for the gangue cementing filling mining of the lower coal seam;

[0008] Step S4: The upper goaf adopts a dynamic filling method. After the upper coal seam is mined, a goaf is formed, that is, gangue filling and grouting are performed to timely control the sinking speed of the roof and the bottom plate;

[0009] Step S5, the mining operation of the lower coal seam is carried out after the upper goaf and the roof and floor are stabilized, and the width of the mining working face is greater than the width of the upper coal seam working face; the goaf formed after mining repeats steps S1-S2, and secondary mining fissure grouting drilling is constructed to complete the gangue cementation filling of the lower coal seam and the grouting reinforcement of the roof and floor.

[0010] Furthermore, in the step S1, the buried pipe spacing N for grouting in the gangue pile, when the gangue filling rate of the goaf is lower than 50%, the buried pipe spacing N and the slurry diffusion radius r should satisfy N≤0.5r; when the gangue filling rate of the goaf is higher than 50%, the buried pipe spacing N and the slurry diffusion radius r should satisfy N≤r.

[0011] Furthermore, the interlayer distance between the upper coal seam and the lower coal seam is not less than 2m.

[0012] Furthermore, the gangue filling height h and mining height H of the goaf areas of the upper coal seam and the lower coal seam should satisfy h≥0.8H.

[0013] Furthermore, the particle size gradation range of the gangue used to fill the goaf is 20-30 mm.

[0014] Furthermore, the coal seam advancement step distance during the continuous mining and filling cycle of the upper coal seam and the lower coal seam is not greater than 2m, and the interval between coal seam mining and goaf gangue filling is less than 12h.

[0015] Furthermore, the spacing d between the overburden fissure grouting boreholes and the secondary mining fissure grouting boreholes and the periodic pressure step distance L should satisfy d=L / 2.

[0016] Furthermore, grouting is started when the overburden stratum fissure grouting drilling holes and the secondary mining fissure grouting drilling holes are d / 2 behind the gangue filling working face.

[0017] The beneficial effects of the present invention are:

[0018] (1) By grouting to seal the secondary mining cracks in the surrounding rock of the upper goaf area in the extremely close distance of the coal seam, cementing the gangue to fill the loose body and fill the incomplete filling area, an artificial strong roof consisting of the roof cover, filling body and floor of the upper goaf area is constructed to protect the gangue cementing filling mining of the lower coal seam;

[0019] (2) Bury pipes and inject grouting layer by layer in the waste rock filling bulk to reduce the creep settlement of the waste rock, inject grouting to fill the incomplete filling area, increase the solid waste disposal volume and filling rate in the goaf, and improve the control effect of ground subsidence;

[0020] (3) The filling body in the goaf area of ​​the upper coal seam supports part of the load, which reduces the concentrated stress of the coal pillars on both sides of the upper coal seam, liberates part of the coal pillars in the lower coal seam, and can increase the coal seam production in the mining area. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a construction process diagram of the three-in-one gangue cementation downward filling coal mining method of the present invention in extremely close distance coal seams;

[0022] Figure 2 It is a schematic diagram of coal mining by coal gangue cementation filling in the upper part of a coal seam at a very close distance of the present invention;

[0023] Figure 3 It is a schematic diagram of coal mining with gangue cementation and filling in the lower part of a coal seam at a very close distance according to the present invention.

[0024] In the figure, 1-upper coal seam, 2-lower coal seam, 3-coal pillar fissure grouting drilling hole, 4-overburden rock fissure grouting drilling hole, 5-secondary mining fissure grouting drilling hole, 6-grouting flower pipe, 7-pre-buried grouting pipe, 8-separation layer, 9-bottom plate, 10-roof plate, 11-overburden rock, 12-waste filling working face. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Since the interlayer spacing of close-distance coal seams is small, the mining disturbance is relatively large. In order to prevent the mining of the lower coal seam from causing strong disturbance, resulting in serious damage to the upper coal seam and loss of mining conditions, the downward mining method is generally adopted for extremely close-distance coal seams. The present invention provides a three-in-one gangue cementation downward filling coal mining method for extremely close-distance coal seams, comprising the following steps:

[0027] Step S1: First, the upper coal seam 1 of the coal seam at a very close distance is mined according to the production design to form a goaf. First, a row of pre-buried grouting pipes 7 are laid at the bottom of the goaf. Figure 1As shown, the goaf is then filled with gangue, and multiple rows of pre-buried grouting pipes 7 are buried at different heights of the gangue pile. The pre-buried grouting pipes 7 are laid at the bottom of the goaf, mainly to grout and reinforce the cracks in the bottom plate 9. The bottom plate 9 also serves as the roof of the lower coal seam 2. Therefore, reinforcing it can control its settlement speed and increase stability. The spacing between each row of pre-buried grouting pipes 7 gradually increases from the bottom of the goaf upward, so that the slurry can be more fully infiltrated into the gangue pile from the bottom to the top, preventing it from forming gaps and affecting the overall stability. The specific construction steps are: first, grouting operations are performed through a row of pre-buried grouting pipes 7 at the bottom of the goaf to fill the cracks in the bottom plate of the upper coal seam with grouting, and then grouting operations are performed step by step on the previous row of pre-buried grouting pipes 7, and a certain period of solidification period is given to allow it to solidify step by step from bottom to top, eventually forming a stable gangue cement body, and finally reducing the creep settlement of the gangue pile.

[0028] Step S2, respectively, drill a plurality of coal pillar fissure grouting boreholes 3 and overburden rock fissure grouting boreholes 4 from the ground surface, the bottom end of the coal pillar fissure grouting borehole 3 is located at the bottom of the coal pillar, and the bottom end of the overburden rock fissure grouting borehole 4 is located in the goaf space after the upper coal seam 1 is mined. According to the height of the fracture zone, the grouting flower tube 6 is placed in the coal pillar fissure grouting borehole and the overburden rock fissure grouting borehole, and the separation layer 8 is avoided, and the fissures in the overburden rock and the coal pillar are grouted to improve the surrounding rock strength of the upper goaf. By drilling the coal pillar fissure grouting borehole 3 and grouting through the grouting flower tube 6, the supporting force of the upper coal pillar can be strengthened. By drilling the overburden rock fissure grouting borehole 4 and grouting through the grouting flower tube 6, the rock column fissures above the upper goaf can be filled and blocked, and the upper rock can be reinforced as a whole. Delamination refers to the difference in the amount of subsidence between different rock layers due to asynchronous sinking. In the roof composed of multiple rock layers, delamination 8 may occur in multiple places. Because delamination grouting under high-pressure grouting conditions will compact the rock layer below the delamination, it will aggravate the degree of mining damage to the rock layer below the delamination, which is not conducive to building an artificial strong roof below it. Therefore, when setting the grouting flower pipe 6, it is necessary to avoid the delamination 8. When the cementing slurry passes through the grouting borehole, the grouting flower pipe 6 flows evenly to the cracks in the surrounding rock of the borehole through the casing opening and seals the cracks.

[0029] Step S3, increase the grouting pressure of the overburden stratum fissure grouting drilling hole until the slurry breaks through the grouting plug at the bottom of the borehole, and forms a cement paste in the incomplete filling area of ​​the upper goaf, until the overburden stratum, goaf filling body and floor of the upper coal seam form a stable rock mass, providing favorable roof conditions for the gangue cementing filling mining of the lower coal seam 2. Through the above three steps, a strong top support foundation is provided for the mining of the lower coal seam, providing reliable safety guarantee for the mining of the lower coal seam and the filling of the lower goaf.

[0030] Step S4: The upper goaf adopts a dynamic filling method. After the upper coal seam is mined, a goaf is formed, that is, gangue filling and grouting operations are performed to timely control the sinking speed of the roof 10 and the bottom plate 9, providing favorable conditions for the rapid mining of the lower coal seam. Figure 2 After the upper goaf is filled for a certain distance, the lower coal seam can be mined, thus forming a dynamic situation of double mining in which the upper part is mined first and then the lower coal seam is mined. On the one hand, it ensures the safety of the lower mining, and on the other hand, it greatly improves the efficiency of coal mining. Figure 3 shown.

[0031] Step S5: After the upper goaf, roof 10 and floor 9 of the lower coal seam 2 are stabilized, mining is carried out, and the width of the mining working face is greater than the width of the upper coal seam working face. Figure 1 As shown. Since the upper goaf, floor and overburden have been reinforced, that is, the stability of the upper part is guaranteed, when mining the lower coal seam, the lower coal pillar does not need to be too large. Therefore, the coal mining face can be expanded, thereby increasing the amount of coal mined.

[0032] Repeat steps S1-S2 in the goaf formed after mining, construct secondary mining fissure grouting drilling holes 5, complete the gangue cementation filling of the lower coal seam and the grouting reinforcement of the top and bottom plates, that is, reinforce the lower goaf and its upper and lower rocks to provide support and guarantee for the coal seam operation below.

[0033] In step S1, the buried pipe spacing N of the buried pipe grouting in the gangue pile, when the gangue filling rate of the goaf is less than 50%, the buried pipe spacing N and the slurry diffusion radius r should satisfy N≤0.5r; when the gangue filling rate of the goaf is greater than 50%, the buried pipe spacing N and the slurry diffusion radius r should satisfy N≤r. The purpose is to effectively diffuse the grouting and effectively fill the space in the goaf except the gangue.

[0034] In addition, since this method is a continuous mining and filling operation, gangue filling and grouting operations are carried out during the coal mining process, which will consume gangue and grouting. Since the raw materials for grouting are mostly fly ash and fine-grained gangue, the gangue consumption in the overall filling process is quite considerable, which provides a good channel for the beneficial treatment of gangue.

[0035] The extremely close distance coal seams referred to in this method have an interlayer distance of no less than 2 meters between the upper coal seam and the lower coal seam. If it is less than 2 meters, the two coal seams can be treated as one coal seam for super thick coal seam mining. When the interlayer distance is too large, the mining of the upper coal seam has little impact on the lower coal seam, and there is no need to use the method of building an artificial strong roof to cover the mining of the adjacent coal seam. Therefore, according to field experience, the upper and lower coal seams using this method are within the critical range of 2 meters.

[0036] In order to minimize the deformation of the surrounding rock in the initial filling stage and improve the strength of the artificial strong roof structure, the goaf gangue filling height h and the mining height H should satisfy h≥0.8H.

[0037] The particle size distribution of the gangue used to fill the goaf is controlled at 20-30mm to reduce the flow resistance of the slurry in the gangue bulk, so that the cementing slurry and the gangue are fully in contact to form a stable gangue cemented filling body.

[0038] In order to control the degree of surrounding rock disturbance and damage during coal seam mining as much as possible, the coal seam advancement step distance during the continuous mining and filling cycle of the upper coal seam 1 and the lower coal seam 2 is not greater than 2m, and the interval between coal seam mining and goaf gangue filling is less than 12h. The expansion deformation induced by mining of the roof and floor plates is controlled by filling the goaf as soon as possible.

[0039] In order to improve the gangue cementation filling effect in the goaf space and effectively seal the surrounding rock mining-induced cracks, the spacing d between the overburden rock fracture grouting boreholes 4 and the secondary mining fracture grouting boreholes 5 and the periodic pressure step distance L should satisfy d=L / 2, and grouting should start when the drilling distance is d / 2 behind the gangue filling working face 12.

[0040] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited thereto. Various changes that can be made within the knowledge scope of technicians in the relevant technical field without departing from the spirit of the present invention are all within the protection scope of the claims of the present invention.

Claims

1. A three-in-one gangue cementation downward filling coal mining method in extremely close distance coal seams, characterized in that: The following steps are involved: Step S1, firstly, the upper coal seam of the extremely close coal seam is mined according to the production design to form a goaf, a row of grouting pipes is laid at the bottom of the goaf, and then the goaf is filled with gangue, and multiple rows of grouting pipes are buried at different heights of the gangue pile, and the spacing between each row of grouting pipes gradually increases from the bottom of the goaf to the top, and grouting operations are first performed through a row of grouting pipes at the bottom of the goaf to grout the cracks in the floor of the upper coal seam, and then grouting operations are performed step by step on the upper row of grouting pipes, and finally a stable gangue cement body is formed to reduce the creep settlement of the gangue; Step S2, constructing a plurality of coal pillar fissure grouting boreholes and overburden rock fissure grouting boreholes from the ground surface, wherein the bottom end of the coal pillar fissure grouting borehole is located at the bottom of the coal pillar, and the bottom end of the overburden rock fissure grouting borehole is located in the goaf space after the upper coal seam is mined; placing grouting flower pipes under the coal pillar fissure grouting boreholes and the overburden rock fissure grouting boreholes according to the height of the fissure zone, avoiding separation, grouting and plugging the fissures in the overburden rock stratum and the coal pillar, and improving the surrounding rock strength of the upper goaf; Step S3, increasing the grouting pressure of the overburden stratum fissure grouting drilling hole until the slurry breaks through the grouting plug at the bottom end of the borehole, and a cementing paste is formed in the incomplete filling area of ​​the upper goaf, until the overburden stratum, the goaf filling body and the bottom plate of the upper coal seam form a stable rock mass, providing favorable roof conditions for the gangue cementing filling mining of the lower coal seam; Step S4: The upper coal seam is mined by continuous mining and filling. After the upper coal seam is mined, a goaf is formed, that is, gangue filling and grouting are performed to timely control the sinking speed of the roof and floor; Step S5, the mining operation of the lower coal seam is carried out after the upper goaf and the roof and floor are stabilized, and the width of the mining working face is greater than the width of the upper coal seam working face; the goaf formed after mining repeats steps S1-S2, and secondary mining fissure grouting drilling is constructed to complete the gangue cementation filling of the lower coal seam and the grouting reinforcement of the roof and floor.

2. The method for coal mining with gangue cementation and downward filling in extremely close-range coal seams according to claim 1 is characterized in that: In the step S1, the buried pipe spacing N for grouting in the gangue pile, when the gangue filling rate of the goaf is lower than 50%, the buried pipe spacing N and the slurry diffusion radius r should satisfy N≤0.5r; when the gangue filling rate of the goaf is higher than 50%, the buried pipe spacing N and the slurry diffusion radius r should satisfy N≤r.

3. The method for coal mining with gangue cementation and downward filling in extremely close-range coal seams according to claim 1 is characterized in that: The interlayer distance between the upper coal seam and the lower coal seam is not less than 2m.

4. The method for coal mining with gangue cementation and downward filling in extremely close-range coal seams according to claim 1 is characterized in that: The gangue filling height h and mining height H of the goaf areas of the upper coal seam and the lower coal seam satisfy h≥0.8H.

5. The method for coal mining with gangue cementation and downward filling in extremely close-range coal seams according to claim 1 is characterized in that: The particle size gradation range of the gangue used to fill the goaf is 20-30 mm.

6. The method for coal mining with gangue cementation and downward filling in extremely close-range coal seams according to claim 1 is characterized in that: The coal seam advancement step distance during the continuous mining and filling cycle of the upper coal seam and the lower coal seam is not greater than 2m, and the interval between coal seam mining and goaf gangue filling is less than 12h.

7. The method for coal mining with gangue cementation and downward filling in extremely close-range coal seams according to claim 1 is characterized in that: The spacing d between the overburden stratum fissure grouting boreholes and the secondary mining fissure grouting boreholes and the periodic pressure step distance L satisfy d=L / 2.

8. The method for coal mining with gangue cementation and downward filling in extremely close-range coal seams according to claim 7 is characterized in that: Grouting begins when the overburden stratum fissure grouting drilling holes and the secondary mining fissure grouting drilling holes are d / 2 behind the gangue filling working face.

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