Method for repairing ground fissures caused by coal mining subsidence in aeolian sand area

Abstract

The invention belongs to the field of eolian sand area coal mine ecological restoration, and particularly relates to a restoration method for ground fissures caused by coal mining subsidence in an eolian sand area. Dividing the ground fissures into boundary ground fissures, middle ground fissures and tension ground fissures according to the development law of the ground fissures caused by coal mining subsidence in the aeolian sand area; according to the characteristic that boundary ground fissures are slightly pulled, the ground fissures can be filled to the maximum extent by adopting a repairing means of drilling a loose stratum before mining, mixing a mixture of dry fly ash and dry cement powder and injecting water for curing after mining; according to the characteristics of initial tension and later compression of the middle ground fissure, cementing slurry is injected when the stratum on one side collapses and is tensioned, and a uniform smearing effect is achieved after the stratum on the other side collapses, so that the middle ground fissure is filled to the maximum extent. And aeolian sand filling slurry is injected into the tensile ground fracture with the shallow development depth. According to the development law of the ground fissures caused by coal mining subsidence in the aeolian sand area, a targeted repairing means is adopted, and the repairing effect is good.

Description

Technical Field

[0001] The invention belongs to the field of ecological restoration of coal mines in aeolian sand areas, and in particular relates to a method for repairing ground fissures caused by mining subsidence in coal mines in aeolian sand areas. Background Art

[0002] The typical geological characteristics of the western mining area are shallow coal seams, thick coal seams, thin bedrock, and aeolian sand strata on the surface. Due to the thin bedrock, there is generally only one key layer in the stratum, namely the basic top. In addition, the thickness of the coal seam is large. After the coal seam is mined, the cracks caused by the destruction of the bedrock reach the surface directly, and ground fissures are generated in the aeolian sand strata on the surface. And because the basic top is mostly unstable due to sliding, after the coal seam is mined, the water-conducting fissures are basically vertical from the coal seam to the surface, that is, ground fissures will appear directly above the surface corresponding to the initial break position of the basic top and the periodic break position, and the damage form of the ground fissures in the inclination is similar to the O-ring shape of the basic top break.

[0003] Coal mining under the above-mentioned western aeolian sand geological conditions will further deteriorate the already fragile ecological environment. Many scholars have studied the development laws of ground fissures formed by coal mining under the above-mentioned geological conditions, but there is still a lack of ecological restoration methods for ground fissures under this condition. The current method of repairing ground fissures is to fill the ground fissures after coal mining, but this filling method is mostly suitable for cracks that only develop on the shallow surface. The cracks are mostly formed by shallow surface deformation and tension. The crack depth is shallow and does not penetrate the loose layer, that is, there is a curved sinking zone in the overburden. If it is directly used to repair ground fissures that reach the surface, due to the large depth and length of the ground fissures, it is easy to fill the ground fissures unevenly, and there will still be residual water loss channels connected to the goaf. Therefore, it is necessary to take targeted governance measures according to the development laws of ground fissures caused by coal mining subsidence in aeolian sand areas to improve the governance effect. Summary of the invention

[0004] In view of the above technical problems, the present invention proposes a method for repairing ground fissures caused by coal mining subsidence in aeolian sand areas, comprising the following steps:

[0005] S1: The estimated initial breaking position and periodic breaking position of the basic roof after the working face is mined; the breaking position of the basic roof is the position where the ground fissures in the stratum are generated, and the ground fissures develop to the surface;

[0006] S2: The ground fissures are divided into boundary ground fissures and middle ground fissures along the mining direction of the working face;

[0007] S3: Before the working face is mined, the stratum is drilled at the expected location of the boundary ground fissure, and dry cement powder and fly ash are mixed into it during the drilling process to form a mixed stirring zone; after the working face is mined, an appropriate amount of water is injected into the mixed stirring zone;

[0008] S4: For each middle ground fissure, after the working face is mined, before the stratum on the cut-eye side of the middle ground fissure collapses and the stratum on the recovery line side collapses, a mixed filling slurry formed by a certain concentration of cement, fly ash and water is injected into it; as the working face continues to advance, the stratum on the recovery line side of the middle ground fissure collapses, and the strata on both sides of the middle ground fissure slide in the vertical direction to more evenly spread the mixed filling slurry between the ground surfaces on both sides of the middle ground fissure.

[0009] Preferably, in step S1, the basic top is the only key layer in the overburden.

[0010] Preferably, in step S2, several ground fissures close to the cutting eye and several ground fissures close to the harvesting line are classified as boundary ground fissures, and all ground fissures that are slightly tensile belong to boundary ground fissures.

[0011] Preferably, in step S2, the ground fissures between the boundary ground fissures on the cutting eye side and the boundary ground fissures on the withdrawal line side are classified as middle ground fissures, and all the middle ground fissures are in a compressed state after the working face is mined.

[0012] Preferably, in step S3, the drilling depth is the entire aeolian sand layer, and the drilling range on the plane is the entire development length of the ground fissure.

[0013] Preferably, after the mining of the working face is completed, if tensile ground fissures are generated outside the mining line, or outside the mining line and the cutting eye, aeolian sand filling slurry is injected into them. The aeolian sand filling slurry is made by mixing pure aeolian sand with water.

[0014] Beneficial technical effects: The present invention divides ground fissures into boundary ground fissures, middle ground fissures and tensile ground fissures according to the development law of ground fissures caused by coal mining subsidence in aeolian sand areas. According to the characteristics of slight tension in boundary ground fissures, the ground fissures are filled to the maximum extent by drilling loose strata before mining and mixing dry fly ash and dry cement powder mixture, and then water-injecting and solidifying after mining. According to the characteristics of the middle ground fissures being initially tensile and later compressive, after the collapse of the strata on one side, cementitious slurry is injected to fill the ground fissures when the strata are tensile, and after the collapse of the strata on the other side, a smoothing effect is achieved, thereby filling the middle ground fissures to the maximum extent. For tensile ground fissures with shallow development depth, it is sufficient to inject aeolian sand filling slurry, which saves costs. According to the development law of ground fissures caused by coal mining subsidence in aeolian sand areas, the present invention adopts targeted repair methods, and the repair effect is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a plan view of ground fissures caused by coal mining subsidence in aeolian sand areas;

[0016] Figure 2 This is a cross-sectional diagram of ground fissures caused by coal mining subsidence in aeolian sand areas;

[0017] Figure 3 This is a schematic diagram of the boundary ground fissure repair process of the present invention;

[0018] Figure 4 This is a schematic diagram of the middle ground fissure repair process of the present invention;

[0019] Figure 5 This is a schematic diagram of the process of repairing tensile ground cracks according to the present invention;

[0020] In the figure, aeolian sand layer 1, ordinary bedrock layer 2, basic roof 3, direct roof 4, coal seam 5, goaf 6, ground fissures 7, ground fissures corresponding to the initial breaking of the basic roof 8, cutting eye 9, recovery line 10, working face 11, mixing and stirring zone 12, mixing and stirring zone after consolidation 13, aeolian sand filling slurry 14, mixed filling slurry 15; tensile ground fissures I, boundary ground fissures II, and middle ground fissures III. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the accompanying drawings.

[0022] like Figure 1-5 As shown, the present invention proposes a method for repairing ground fissures caused by coal mining subsidence in aeolian sand areas, comprising the following steps:

[0023] S1: It is estimated that the initial fracture position and periodic fracture position of the basic roof 3 after the working face 11 is mined. The working face 11 is arranged in the coal seam 5. In the case where there is only one key layer in the overburden, that is, the basic roof 3 is the only key layer in the overburden, the fracture position of the basic roof 3 is the generation position of the ground fissure 7 in the stratum, that is, a ground fissure 7 will be generated directly above each fracture position of the basic roof 3, and the ground fissure 7 develops from the basic roof 3 to the surface, penetrating the upper ordinary bedrock layer 2 and the aeolian sand layer 1; the lower part of the basic roof 3 is the direct roof 4, and the direct roof 4 collapses into rubble to form a goaf 6 after the working face is mined; Figure 1 The damage form of the ground fissure 7 shown in the plane is consistent with the O-ring form of the basic top break;

[0024] S2: All ground fissures 7 directly caused by the breaking of the basic roof 3 are divided into boundary ground fissures II and middle ground fissures III. Specifically, several ground fissures 7 near the cutting eye 9 and several ground fissures 7 near the withdrawal line 10 are classified as boundary ground fissures II. Generally speaking, after the mining of the working face 11 is completed, the boundary ground fissures II are slightly stretched due to the cantilevered effect of the boundary basic roof 3, that is, the opening of the ground fissures 7 in the boundary ground fissures II is slightly larger (relative to the middle ground fissures); generally, 2-4 ground fissures 7 near the cutting eye 9 and 2-4 ground fissures 7 near the withdrawal line 10 can be classified as boundary ground fissures II to ensure that all ground fissures are slightly stretched. All slightly tensile ground fissures 7 belong to boundary ground fissures II; for example, three ground fissures 7 close to the cut eye 9 and the withdrawal line 10 are selected as boundary ground fissures II, among which the ground fissure 7 farthest from the cut eye 9 and the ground fissure 7 farthest from the withdrawal line 10 may be in a compressed state; that is to say, it is necessary to ensure that all slightly tensile ground fissures 7 close to the cut eye 9 and the withdrawal line 10 belong to boundary ground fissures II; the ground fissure 7 between the boundary ground fissure II on the cut eye side and the boundary ground fissure II on the withdrawal line side is designated as a middle ground fissure III, and after the mining of the working face 11 is completed, all the ground fissures 7 in the middle ground fissure III are in a compressed state;

[0025] S3: Before mining at working face 11, Figure 1 , Figure 3 As shown, the estimated location of ground fissure 7 in boundary ground fissure II ( Figure 3 In (a), a spiral drill is used to drill vertically downward into the aeolian sand layer 1 at the expected position of the ground fissure 7. The drilling depth is designed according to needs, preferably the entire aeolian sand layer 1. The drilling range on the plane is the development length of the entire ground fissure 7. Dry cement powder and fly ash are mixed into the loose aeolian sand 1 during the drilling process, that is, dry cement powder and fly ash powder are mixed into the drilled loose aeolian sand 1 to form a mixing zone 12 ( Figure 3 (b));

[0026] After the working face 11 is mined, the ground fissure 7 in the boundary ground fissure II is formed. At this time, the mixture of aeolian sand, cement and fly ash in the mixing zone 12 will flow to the lower part of the ground fissure 7 due to its loose state. More water will flow into the larger gap. Since the mixing zone 12 covers the entire length of the ground fissure 7 on the plane, the ground fissure 7 in the boundary ground fissure II will be filled with the mixture of aeolian sand, cement and fly ash. Then, an appropriate amount of water is injected into the mixing zone 12 so that the mixture of aeolian sand, cement and fly ash forms a cementitious mixed material that fills the entire ground fissure 7 ( Figure 3 (c));

[0027] S4: Figure 1 , Figure 4As shown, for each ground fissure 7 in the middle ground fissure III, after the working face 11 is mined, after the ground fissure 7 is formed, and before the stratum on the cut-eye side of the ground fissure 7 collapses and the stratum on the side of the withdrawal line collapses, the ground fissure 7 is in a tensile state and the width of the ground fissure is relatively large. A mixed filling slurry 15 formed by a mixture of cement, fly ash and water of a certain concentration is injected therein. The mixed filling slurry 15 flows downward continuously along with the cracks of the ground fissure 7 expanding. More slurry flows into the larger cracks, and the ground fissure 7 in the middle ground fissure III is filled with the mixed filling slurry 15 in the length direction. Since the cracks at the bottom of the ground fissure 7 are smaller, the mixed filling slurry 15 may not flow in ( Figure 4 (a));

[0028] As the working face 11 continues to advance, the strata on one side of the ground fissure 7 collapse, and the strata on both sides of the ground fissure 7 slide in the vertical direction. During the sliding process, the mixed filling slurry 15 will be more evenly applied to the ground layers on both sides of the ground fissure 7, that is, more evenly applied to the ground fissure 7, and the application range can be expanded in height ( Figure 4 (b)); the later ground fissure III is in a continuous pressure state, which will make the mixed filling slurry 15 more evenly distributed, and can further improve the repair effect of each ground fissure 7 in the middle ground fissure III.

[0029] S5: Figure 1-2 , Figure 5 As shown, after the mining of the working face 11 is completed, some ground fissures 7 will be formed outside the mining line 10, or outside the mining line 10 and the cutting eye 8. These ground fissures 7 are not ground fissures 7 caused by the direct breaking of the basic roof 3, but ground fissures 7 caused by the tension of the aeolian sand layer 1 after the mining of the working face 11. These ground fissures 7 are classified as tension ground fissures I in the present invention. The characteristics of these ground fissures 7 are that the crack depth is small and the cross section is an opening shape with a large top and a small bottom ( Figure 5 In (a), since the tensile ground fissure I does not penetrate the entire aeolian sand layer 1, especially there is no crack in the bedrock layer below it, the ground fissure 7 of the tensile ground fissure I will not cause water to flow into the goaf 6. Therefore, it is only necessary to inject aeolian sand filling slurry 14 into the tensile ground fissure I after the working face 11 is mined, and pure aeolian sand can be mixed with water.

[0030] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of methods under the inspiration of the present invention. Any technical solution that is the same or similar to that of the present application falls within the protection scope of the present invention.

Claims

1. A method for repairing ground fissures caused by coal mining subsidence in aeolian sand areas, characterized in that: The following steps are involved: S1: The estimated initial breaking position and periodic breaking position of the basic roof after the working face is mined; the breaking position of the basic roof is the position where the ground fissures in the stratum are generated, and the ground fissures develop to the surface; S2: The ground fissures are divided into boundary ground fissures and middle ground fissures along the mining direction of the working face; S3: Before the working face is mined, the stratum is drilled at the expected location of the boundary ground fissure, and dry cement powder and fly ash are mixed into it during the drilling process to form a mixed stirring zone; after the working face is mined, an appropriate amount of water is injected into the mixed stirring zone; S4: For each middle ground fissure, after the working face is mined, before the stratum on the cut-eye side of the middle ground fissure collapses and the stratum on the recovery line side collapses, a mixed filling slurry formed by a certain concentration of cement, fly ash and water is injected into it; as the working face continues to advance, the stratum on the recovery line side of the middle ground fissure collapses, and the strata on both sides of the middle ground fissure slide in the vertical direction to more evenly spread the mixed filling slurry between the ground surfaces on both sides of the middle ground fissure.

2. The repair method according to claim 1, characterized in that: In step S1, the basic top is the only key layer in the overburden.

3. The repair method according to claim 1, characterized in that: In step S2, several ground fissures close to the cutting eye and several ground fissures close to the harvesting line are classified as boundary ground fissures, and all ground fissures that are slightly tensile belong to boundary ground fissures.

4. The repair method according to claim 3, characterized in that: In step S2, the ground fissures between the boundary ground fissures on the cutting eye side and the boundary ground fissures on the withdrawal line side are classified as middle ground fissures. After the working face is mined, all the middle ground fissures are in a compressed state.

5. The repair method according to claim 1, characterized in that: In step S3, the drilling depth is the entire aeolian sand layer, and the drilling range on the plane is the entire length of the ground fissure development.

6. The repair method according to any one of claims 1 to 5, characterized in that: After the mining of the working face is completed, if tensile ground fissures occur outside the mining line, or outside the mining line and the cutting eye, aeolian sand filling slurry is injected into them. The aeolian sand filling slurry is made by mixing pure aeolian sand and water.

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