A method for treating old goaf using directional drilling

Abstract

The present invention belongs to the technical field of coal mine filling and mining, and specifically relates to a method for treating old goaf areas using directional drilling, including constructing a directional grouting borehole on the bottom plate side, and constructing the first horizontal branch to the height of the collapse zone; constructing a directional hydrophobic borehole on the top plate side, and the horizontal section is located at the bottom of the vertical range of the collapse zone in height; grouting the collapse zone from the directional grouting borehole, and the grouting material is a non-cementing slurry, and the secreted water is extracted at the same time; extending the vertical section depth of the directional grouting borehole and constructing the next horizontal branch, and continuing to grout the collapse zone; the depth of each downward extension is successively reduced, and the concentration of each grouting is successively increased. The present invention constructs a directional multi-horizontal branch well from the bottom of the coal seam from top to bottom to grout the gaps in the collapse zone, and the grouting material uses a non-cementing material, and the concentration increases in level in turn. In combination with hydrophobic drilling, the drilling construction volume can be greatly reduced, the filling material cost can be reduced, the filling rate of the collapse zone gap can be increased, and water can be saved.

Description

Technical Field

[0001] The invention belongs to the technical field of coal mine filling mining, and in particular relates to an old goaf area treatment method using directional drilling. Background Art

[0002] The goaf is a broken rock area formed near the coal mining area after the coal mining causes the rock to collapse. Figure 1 As shown, it generally includes collapse areas and water-conducting fracture zones. Above the water-conducting fracture zones is a curved sinking zone. At the same time, coal mining will also cause cracks in the rock strata at a certain depth in the bottom plate to form a bottom plate fracture zone. The old goaf area specifically refers to the goaf area formed after a long period of coal mining. Generally, a collapse area is formed on the ground.

[0003] There are a large number of voids in the rock blocks in the collapse zone of the old goaf, which causes the old goaf to be compressed and deformed for a long time, and then causes the surface to sink slowly for a long time. If road construction, reclamation and other work are carried out in the surface collapse area, slurry will generally be injected into the collapse zone of the old goaf to fill the voids, thereby reducing further compression of the old goaf.

[0004] The existing method of grouting to fill the gaps in the old goaf is relatively uniform, that is, vertical drilling from the surface to penetrate the water-conducting fracture zone and then grouting into the collapsed zone. However, the water-conducting fracture zone is large, and there are layered and mutually interlocking rock blocks. When the borehole passes through the water-conducting fracture zone, if it passes through the interlocking area between these rock blocks, that is, through the cracks between these rock blocks, it will cause the flushing fluid to leak. In addition, the presence of cracks can easily cause the drilling to deviate during construction, which is not conducive to construction according to the set final hole position. This ultimately leads to low drilling success rate, low qualification rate, high construction cost, long construction period, and even unsatisfactory grouting filling effect.

[0005] The existing materials for grouting and filling old goafs generally include non-cementitious materials (such as pure fly ash) and cementitious materials (such as cement). Non-cementitious materials generally have a high water content, which easily leads to a low filling rate of the voids in the collapse zone and a poor sinking reduction effect. The diffusion radius of the cementitious material slurry is small, the material is expensive, and the drilling construction volume is large, resulting in high costs. In addition, the existing technology for grouting and filling voids in old goafs does not take into account the inclination of the coal seam, that is, it does not take into account the inclination characteristics of the old goaf for design, and there is still room for optimization. Summary of the invention

[0006] In order to solve the problems of low drilling porosity, difficult filling material selection, and lack of consideration for coal seam inclination during traditional grouting filling of old goafs, the present invention proposes a method for treating old goafs using directional drilling, in which directional multi-horizontal branch wells are constructed from the bottom of the coal seam to perform grouting filling of the voids in the collapsed zone. The grouting material is a non-cementitious material, and the concentration increases in sequence with the level. Combined with hydrophobic drilling, the amount of drilling construction can be greatly reduced, the cost of filling materials can be reduced, the filling rate of the voids in the collapsed zone can be increased, and water can be saved. The present invention is particularly suitable for treating steeply inclined coal seams, moderately inclined coal seams, and gently inclined coal seams with an inclination angle greater than 20°. Specifically, the technical solution of the present invention includes the following steps:

[0007] S1: Directional grouting drilling is constructed from the ground on the bottom plate side. The directional grouting drilling includes a vertical section and a first horizontal branch. The first horizontal branch is constructed to the vertical range of the collapse zone.

[0008] S2: construct directional drainage drilling holes from the ground on the roof side. The directional drainage drilling holes include vertical and horizontal sections. The horizontal section is located at the bottom of the vertical range of the collapse zone;

[0009] S3: Grouting is carried out from the directional grouting borehole to the collapse zone. The grouting material is a non-cementing slurry mixed with fly ash and water. At the same time, directional hydrophobic drilling is used to extract the exuded water;

[0010] S4: Extend the vertical section depth of the directional grouting borehole, and then construct the second horizontal branch from the bottom of the vertical section hole to the collapse zone;

[0011] S5: Grouting is carried out from the directional grouting borehole to the collapse zone. The grouting material is a non-cementing slurry mixed with fly ash and water. At the same time, directional hydrophobic drilling is used to extract the exuded water;

[0012] S6: Continue to extend the directional grouting drilling according to steps S4-S5 and construct horizontal branches to the collapse zone, and then grout until the collapse zone of the entire goaf is filled.

[0013] Preferably, the horizontal branch of the directional grouting borehole horizontally penetrates the entire collapse zone, and a flower pipe is arranged within the collapse zone.

[0014] Preferably, during grouting of the horizontal branch of each directional grouting borehole, grouting is stopped when the grouting pressure reaches the designed grouting pressure and the grouting material can no longer be injected under the grouting pressure.

[0015] Preferably, fly ash can be replaced by coal gangue ground into powder.

[0016] Preferably, the extracted water is further used to prepare grouting material.

[0017] Preferably, the depth of each downward extension of the directional grouting drilling hole decreases successively.

[0018] Preferably, the grouting concentration of each horizontal branch of the directional grouting drilling increases from top to bottom.

[0019] Preferably, step S6 also includes: finally filling the directional grouting borehole and the directional hydrophobic borehole.

[0020] The key means and beneficial effects of the present invention are as follows: the present invention constructs directional multi-horizontal branch wells from the bottom of the coal seam to perform grouting filling on the voids in the collapsed zone, and the grouting material is selected from non-cementitious materials, and the concentration increases in sequence according to the level. In combination with hydrophobic drilling, the drilling construction volume can be greatly reduced, the filling material cost can be reduced, the filling rate of the voids in the collapsed zone can be increased, and water can be saved. The key means and beneficial effects of the present invention can be specifically referred to the introduction of the specific implementation method section below. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic cross-sectional view of an old goaf area in the old goaf area treatment method of the present invention;

[0022] Figure 2 It is a cross-sectional schematic diagram of the first treatment stage in the old goaf treatment method of the present invention;

[0023] Figure 3 It is a cross-sectional schematic diagram of the second treatment stage in the old goaf treatment method of the present invention;

[0024] Figure 4 It is a cross-sectional schematic diagram of the third treatment stage in the old goaf treatment method of the present invention;

[0025] Figure 5 It is a cross-sectional schematic diagram of the fourth treatment stage in the old goaf treatment method of the present invention;

[0026] Figure 6 It is a cross-sectional schematic diagram of the old goaf area after final treatment in the old goaf area treatment method of the present invention;

[0027] In the figure, there are residual coal pillars 1, coal seam mining area 2, floor fissure area 3, collapse zone 4, water-conducting fissure zone 5, directional grouting borehole 6, first horizontal branch 61, second horizontal branch 62, third horizontal branch 63, fourth horizontal branch, directional drainage borehole 7, first filling body 81, second filling body 82, third filling body 83, and fourth filling body 84. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is described in more detail below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0029] like Figure 1The figure shows an old goaf area. The original coal seam has an inclination of 35°, which is a medium-inclined coal seam. The goaf area is formed after the coal seam mining area 2 is mined. The upper and lower sides of the coal seam mining area 2 are residual coal pillars 1. Affected by the large inclination of the coal seam, the overall thickness of the goaf area basically increases gradually from bottom to top. The thickness here is the vertical distance from the boundary of the goaf area to the bottom of the coal seam (the dotted line in the figure), specifically referring to the direction perpendicular to the inclination of the coal seam. The goaf area includes a collapse zone 4 and a water-conducting fracture zone 5. The average thickness of the coal seam within the coal seam mining area 2 is 3.2m, and the thickness of the collapse zone 4 is mainly between 12.5 and 16.0m. The thickness of the water-conducting fracture zone 5 is mainly between 20.2 and 29.4 m, and the vertical height of the collapse zone 4 is about 150 m. The lower part of the collapse zone 4 is the bottom plate fracture zone 3, and the average thickness of the fractures in the bottom plate fracture zone 3 is 2.5 m. Here, the bottom plate fracture zone mainly refers to the area where the fractures are relatively developed, such as the fractures are connected in the thickness direction. It can be seen that the thickness of the water-conducting fracture zone 5 is much greater than that of the bottom plate fracture zone 3. At the same time, it is affected by the shape of the rock mass in the water-conducting fracture zone 5, which can easily lead to borehole deviation. The fractures in the bottom plate fracture zone 3 are relatively uniform and dense, which is easy to drill and can ensure that the borehole is drilled along the designed direction.

[0030] In view of the above-mentioned goaf, the present invention proposes a method for treating old goaf using directional drilling, comprising the following steps:

[0031] Step 1: Figure 2 As shown, a directional grouting borehole 6 is constructed from the ground on the bottom plate side. The directional grouting borehole 6 includes a vertical section and a first horizontal branch 61. The first horizontal branch 61 is located in the vertical range of the collapse zone 4 in height, and is located a certain distance below its highest point. In this embodiment, the first horizontal branch 61 is about 8 to 10 meters below the highest point of the collapse zone 4. The first horizontal branch 61 passes through the residual coal pillar 1 and enters the collapse zone 4. The first horizontal branch 61 preferably runs through the entire collapse zone 4 horizontally, and a flower pipe is arranged in the collapse zone 4. Since the amount of gravel in the collapse zone above the first horizontal branch 61 is small, basically no drilling alarm will occur during drilling;

[0032] Step 2: If Figure 2 As shown, a directional drainage borehole 7 is constructed from the ground on the top plate side, and the directional drainage borehole 7 includes a vertical section and a horizontal section, and the horizontal section is located at the bottom of the vertical range of the collapse zone 4 in height;

[0033] Step three: grouting from the directional grouting borehole 6 to the collapse zone 4, the grouting material is a non-cementing slurry mixed with fly ash and water, the fly ash can also be replaced by coal gangue ground into powder, the water-cement volume ratio of the grouting material is 50%; when the grouting pressure reaches the designed grouting pressure and the grouting material can no longer be injected under the grouting pressure, the grouting is stopped, and the designed grouting pressure of this embodiment is 5MPa; during the grouting process, the fly ash is continuously attached to the gravel of the collapse zone, that is, the gaps between the gravel are continuously filled, and the water flows to the bottom of the collapse zone 4 due to gravity, and the directional hydrophobic borehole 7 is used to extract the secreted water, and the extracted water is continuously used to prepare the grouting material; finally, the first horizontal branch 61 is filled; Figure 3 As shown, after three steps of grouting, a first filling body 81 is formed in the collapse zone 4;

[0034] Four steps: Figure 3 As shown, the vertical section depth of the directional grouting borehole 6 is extended to a depth of 55m, and then a second horizontal branch 62 is constructed from the bottom of the vertical section hole to the collapse zone 4. The second horizontal branch 62 preferably runs horizontally through the entire collapse zone 4, and a flower pipe is arranged in the collapse zone 4. Since the gravel in the collapse zone above the second horizontal branch 62 is basically filled densely, the amount of unfilled gravel is small, and basically no drilling error will occur during drilling;

[0035] Step 5: grouting from the directional grouting borehole 6 to the collapse zone 4, the grouting material is a non-cementing slurry mixed with fly ash and water, the fly ash can also be replaced by coal gangue ground into powder, the water-cement volume ratio of the grouting material is 60%; when the grouting pressure reaches the designed grouting pressure and the grouting material can no longer be injected under the grouting pressure, the grouting is stopped, and the designed grouting pressure of this embodiment is 5MPa or 6MPa; during the grouting process, the fly ash is continuously attached to the gravel of the collapse zone, that is, the gaps between the gravel are continuously filled, and the water flows to the bottom of the collapse zone 4 due to gravity, and the directional hydrophobic borehole 7 is used to extract the secreted water, and the extracted water is continuously used to prepare the grouting material; finally, the second horizontal branch 62 is filled; Figure 4 As shown, after five steps of grouting, a second filling body 82 is formed in the collapse zone 4;

[0036] Six steps: Figure 4 As shown, the vertical section depth of the directional grouting borehole 6 is extended to a depth of 40m, and then a third horizontal branch 63 is constructed from the bottom of the vertical section hole to the collapse zone 4. The third horizontal branch 63 preferably runs horizontally through the entire collapse zone 4, and a flower pipe is arranged in the collapse zone 4. Since the gravel in the collapse zone above the third horizontal branch 63 is basically filled densely, the amount of unfilled gravel is small, and basically no drilling error will occur during drilling;

[0037] Step 7: grouting from the directional grouting borehole 6 to the collapse zone 4, the grouting material is a non-cementing slurry mixed with fly ash and water, the fly ash can also be replaced by coal gangue ground into powder, the water-cement volume ratio of the grouting material is 70%; when the grouting pressure reaches the designed grouting pressure and the grouting material can no longer be injected under the grouting pressure, the grouting is stopped, and the designed grouting pressure of this embodiment is 5MPa or 7MPa; during the grouting process, the fly ash is continuously attached to the gravel of the collapse zone, that is, the gaps between the gravel are continuously filled, and the water flows to the bottom of the collapse zone 4 due to gravity, and the directional hydrophobic borehole 7 is used to extract the secreted water, and the extracted water is continuously used to prepare the grouting material; finally, the third horizontal branch 63 is filled; Figure 5 As shown, after the six-step grouting, a third filling body 83 is formed in the collapse zone 4;

[0038] Eight steps: Figure 5 As shown, the vertical section depth of the directional grouting borehole 6 is extended to a depth of 25 m, and then a fourth horizontal branch 64 is constructed from the bottom of the vertical section hole to the collapse zone 4. The fourth horizontal branch 64 preferably runs horizontally through the entire collapse zone 4, and a flower pipe is arranged in the collapse zone 4. Since the gravel in the collapse zone above the fourth horizontal branch 64 is basically filled densely, the amount of unfilled gravel is small, and basically no drilling error will occur during drilling;

[0039] Nine steps: grouting from the directional grouting borehole 6 to the collapse zone 4, the grouting material is a non-cementing slurry mixed with fly ash and water, the fly ash can also be replaced by coal gangue ground into powder, and the water-cement volume ratio of the grouting material is 80%; when the grouting pressure reaches the designed grouting pressure and the grouting material cannot be further injected under the grouting pressure, the grouting is stopped, and the designed grouting pressure of this embodiment is 5MPa or 8MPa; during the grouting process, the fly ash is continuously attached to the gravel of the collapse zone, that is, the gaps between the gravel are continuously filled, and the water flows to the bottom of the collapse zone 4 due to gravity, and the directional hydrophobic borehole 7 is used to extract the secreted water, and the extracted water is continuously used to prepare the grouting material; finally, the directional grouting borehole 6 and the directional hydrophobic borehole 7 are filled; Figure 6 As shown, after nine steps of grouting, a fourth filling body 84 is formed in the collapse zone 4; the filling of the goaf is completed.

[0040] The present invention constructs directional multi-horizontal branch wells from top to bottom of the coal seam floor to perform grouting to fill the voids in the collapsed zone. Since the thickness of the floor fracture zone is much smaller than the thickness of the water-conducting fracture zone, and the fractures in the floor fracture zone are evenly and densely developed, which are different from the mutually interlocking rectangular rock blocks in the water-conducting fracture zone, the drilling construction workload is small, the drilling hole success rate is high, and the construction cost is low.

[0041] The present invention adopts a top-down grouting method. The grouting material can be selected from non-cemented fly ash or coal gangue ground into powder. During grouting, the fly ash is continuously attached to the gravel blocks of the collapse zone until the gaps between the gravel blocks of the collapse zone are filled densely. Water is drawn out from the hydrophobic drilling hole and can be continuously utilized. Thanks to this grouting and hydrophobic method, non-cemented materials can be used without wasting filling materials. This can greatly reduce the filling cost and ensure the density of the grouting filling.

[0042] The grouting concentration of the present invention increases from top to bottom, and a dense grouting filling body is formed in a certain range below the grouting borehole during grouting. However, it can be determined that part of the fly ash has also been attached to the gravel in the collapse zone below the dense grouting filling body, that is, the grouting filling time of the uppermost horizontal branch hole is the longest, and the grouting amount must be the largest. The grouting filling time and the grouting amount gradually decrease downward, because the upper horizontal branch hole will fill the gaps in the collapse zone of all ranges below it, but the filling range is focused on being near its borehole. Therefore, the subsequent grouting concentration can be increased, and the grouting pressure can also be increased.

[0043] In addition, the grouting scheme for treating old goaf areas of the present invention can reduce water consumption. On the one hand, water can be recycled and avoid occupying the gaps in the collapse zone, thereby increasing the filling rate while reducing water consumption. On the other hand, when grouting from top to bottom, fine-grained fly ash is concentrated on the bottom plate of the coal seam, which can prevent water from being lost from the cracks in the bottom plate of the coal seam. The grouting scheme from the bottom plate can reduce the loss of water from the water-conducting fracture zone.

[0044] The present invention is not limited to the above examples. Any changes, modifications, additions or substitutions made by those skilled in the art within the essential scope of the present invention without departing from the purpose and scope of the technical solution of the present invention should also be covered by the scope of protection of the claims of the present invention.

Claims

1. A method for treating an old goaf using directional drilling, wherein the old goaf is a closed old goaf formed by a single coal seam, characterized in that: Directional multi-horizontal branch wells are constructed from the bottom of the coal seam to fill the gaps in the collapsed zone with grouting, including the following steps: S1: Directional grouting drilling is constructed from the ground on the bottom plate side. The directional grouting drilling includes a vertical section and a first horizontal branch. The first horizontal branch is constructed to the vertical range of the collapse zone. S2: construct directional drainage drilling holes from the ground on the roof side. The directional drainage drilling holes include vertical and horizontal sections. The horizontal section is located at the bottom of the vertical range of the collapse zone; S3: Grouting is carried out from the directional grouting borehole to the collapse zone. The grouting material is a non-cementing slurry mixed with fly ash and water. At the same time, directional hydrophobic drilling is used to extract the exuded water; S4: Extend the vertical section depth of the directional grouting borehole, and then construct the second horizontal branch from the bottom of the vertical section hole to the collapse zone; S5: Grouting is carried out from the directional grouting borehole to the collapse zone. The grouting material is a non-cementing slurry mixed with fly ash and water. At the same time, directional hydrophobic drilling is used to extract the exuded water; S6: Continue to extend the directional grouting drilling according to steps S4-S5 and construct the horizontal branch to the collapse zone, and then grout until the collapse zone of the entire old goaf is filled; Among them, the depth of each downward extension of the directional grouting drilling hole decreases successively, and the grouting concentration of each horizontal branch of the directional grouting drilling hole increases successively from top to bottom; The horizontal branch of the directional grouting drilling hole runs horizontally through the entire collapse zone, and flower pipes are arranged within the collapse zone; When grouting the horizontal branch of each directional grouting borehole, grouting is stopped when the grouting pressure reaches the designed grouting pressure and the grouting material can no longer be injected under the grouting pressure.

2. The method for treating old goaf according to claim 1, characterized in that: Fly ash can be replaced by grinding coal gangue into powder.

3. The method for treating old goaf according to claim 1, characterized in that: The pumped water is then used to prepare the grouting material.

4. The method for treating old goaf according to claim 1, characterized in that: Step S6 also includes: finally filling the directional grouting borehole and the directional drainage borehole.

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