Method for slowing down mining subsidence through water injection expansion inverted arch of floor rock stratum

Abstract

The invention relates to the field of coal mining and subsidence control, in particular to a method for slowing down mining subsidence through floor rock stratum water injection expansion inverted arches. Comprising the steps of determining the range of a floor failure zone below a coal seam, and selecting a rock stratum with a certain thickness below the floor failure zone as an isolation protection zone; the lower part of the isolation protection zone is a water injection expansion zone, and the rock stratum of the isolation protection zone adjacent to the water injection expansion zone is a water-encountering non-expansion rock stratum; directional drilling is constructed in a working face roadway, and a directional drilling horizontal section is constructed in a water injection expansion zone; after the working face is pushed over the horizontal section of a certain directional drill hole and before the working face reaches the hole opening of the directional drill hole, water is injected into the directional drill hole at high pressure, then the water injection pressure is reduced, and the water injection amount is controlled to reach the water absorption limit of a water injection expansion zone. Water is injected into the bottom plate rock stratum to enable the bottom plate rock stratum to expand, so that the bottom plate rock stratum is lifted to support the goaf, sinking of the overlying rock stratum is reduced, and surface subsidence is controlled. The method realizes settlement reduction only through water injection expansion, and is low in cost and environment-friendly.

Description

Technical Field

[0001] The invention relates to the field of coal mining and subsidence control, and in particular to a method for slowing down mining subsidence by water injection expansion and reverse arching of a bottom rock layer. Background Art

[0002] Due to the large-scale mining areas formed by coal mining, the overlying rock layers gradually collapsed under the action of gravity, which in turn caused surface subsidence. The surface deformation caused by this process will cause cracks, tilts and even collapse risks of buildings and other infrastructure (such as houses, roads, bridges, railway tunnels, etc.), posing a serious threat to the safety of life and property of residents. Surface subsidence will also damage land resources, cause surface vegetation degradation, damage the surface drainage system, cause river interruption, lake drying up and groundwater level drop, and affect the sustainable use of regional water resources. At the same time, the subsidence process destroys biological habitats and affects the balance and stability of the mining area ecosystem. The surface subsidence caused by coal mining has far-reaching negative impacts on the environment, economy and society, and effective prevention and control measures are urgently needed to reduce its harm.

[0003] At present, some mining areas usually use backfill mining to solve problems such as mine environmental damage, surface subsidence and waste of coal resources. By filling the mined space with solid, paste or high-water filling materials during the mining process, a filling body is formed to support and control the overlying rock strata, thereby greatly reducing the adverse impact of coal mining on the environment. However, the commonly used partial backfill mining technology requires the construction of an independent backfill pipeline system in the mining area or on the ground, which increases the cost of coal mining and causes mining and backfilling interference problems that affect the efficient mining of coal. Summary of the invention

[0004] In order to solve the problems of high cost and low efficiency in the subsidence control methods in the prior art, the present invention proposes a method for slowing mining subsidence by injecting water into the bottom rock stratum to expand and reversely arch, which is suitable for the situation where there is a rock stratum that is easy to absorb water and expand in the bottom of the coal seam; the method comprises the following steps:

[0005] S1: Determine the range of the floor damage zone below the coal seam, select a rock layer of a certain thickness below the floor damage zone as an isolation protection zone, the isolation protection zone will be arched after the water injection expansion zone expands, but no cracks will be generated to connect to the upper floor damage zone, or the generated cracks will not be connected to the cracks in the floor damage zone; the lower part of the isolation protection zone is a water injection expansion zone, the rock layer in the water injection expansion zone can have the property of swelling when exposed to water, and the rock layer adjacent to the isolation protection zone and the water injection expansion zone is selected to be a rock layer that does not swell when exposed to water;

[0006] S2: construct directional drilling holes in the tunnels on one side or both sides of the working face, wherein the horizontal section of the directional drilling holes is constructed in the water injection expansion zone, the directional drilling holes are constructed in the direction of the opposite tunnel in the width direction of the working face, and the directional drilling holes are constructed in the direction of the eye cutting in the advancing direction of the working face;

[0007] S3: Install a packer at the orifice of the directional drilling hole to seal the rock formations corresponding to the bottom plate damage zone and the isolation protection zone;

[0008] S4: After the working face passes through a horizontal section of a directional borehole and before reaching the orifice of the directional borehole, high-pressure water is first injected into the directional borehole to form cracks in the water injection expansion zone, and then the water injection pressure is reduced and the water injection volume is controlled to reach the water absorption limit of the water injection expansion zone.

[0009] Preferably, in step S1, the water injection expansion zone is selected from a rock layer rich in clay minerals.

[0010] Preferably, in step S2, the directional drilling is parallel to the width direction of the working surface.

[0011] The inventive point and beneficial effect of the present invention: Based on the characteristics of the water-absorbing and swelling rock layer outside the bottom plate damage zone, the present invention designs it into a water-absorbing and swelling zone, then constructs directional drilling and fracturing the water-absorbing and swelling zone, forms conductive cracks in the water-absorbing and swelling zone, and then injects water to expand the rock layer in the water-absorbing and swelling zone so that the water-absorbing and swelling zone and the bottom plate rock layer above it form an anti-arch effect, thereby supporting the overlying rock layer and achieving the effect of slowing down the subsidence. Compared with the traditional method, this method does not need to use a large amount of filling materials, and only achieves the expansion effect through water injection. The water injection expansion will not cause secondary pollution to the environment, and the anti-arch structure can significantly enhance the bearing capacity of the bottom plate and reduce the surface subsidence rate, which is in line with the concept of green mining in modern mines. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of the mechanism of water injection expansion and reverse arching of the bottom rock layer to slow down mining subsidence;

[0013] Figure 2 It is a schematic plan view of the directional drilling construction in the present invention for slowing down mining subsidence by water injection expansion and reverse arching of the bottom rock layer;

[0014] In the figure: water injection expansion zone-1, isolation protection zone-2, bottom plate uniform fracture zone-3, bottom plate crushing expansion zone-4, fracture zone-5, collapse zone-6, directional drilling-7, fracture-8, drilling packer-9. DETAILED DESCRIPTION

[0015] In order to better understand the technical content of the present invention, specific embodiments are cited and described as follows in conjunction with the accompanying drawings. In the present invention, various aspects of the present invention are described with reference to the accompanying drawings, in which many illustrative embodiments are shown. The embodiments of the present invention are not limited to those described in the accompanying drawings. It should be understood that the present invention is implemented by any of the various concepts and embodiments introduced above, as well as the concepts and implementations described in detail below, because the concepts and embodiments disclosed in the present invention are not limited to any implementation. In addition, some aspects disclosed in the present invention can be used alone or in any appropriate combination with other aspects disclosed in the present invention.

[0016] like Figure 1-2 In order to solve the problems of high cost and low efficiency in the subsidence control methods in the prior art, the present invention proposes a method for slowing mining subsidence by water injection and expansion of the bottom rock layer, which is suitable for the situation where there is a rock layer that is easy to absorb water and expand in the bottom of the coal seam; the specific steps include:

[0017] S1: Based on the lithology and thickness of the floor rock formation, determine the range of the floor damage zone below the coal seam. The floor damage zone includes a floor crushing and expansion zone 4 and a floor uniform fracture zone 3. The floor rock formation in the floor crushing and expansion zone 4 is broken in an irregular network, and the broken blocks are relatively small. Since there are gaps between the broken blocks, there are certain expansion characteristics. The floor rock formation in the floor uniform fracture zone 3 is broken in a regular manner with regular and relatively large broken blocks. The floor damage zone can form a water channel. Select a certain thickness of rock below the floor damage zone. The isolation protection zone 2 is a layer (usually including multiple rock layers) as an isolation protection zone 2, which is arched after the water injection expansion zone 1 expands, but does not generate cracks that connect to the upper bottom plate damage zone, or the generated cracks are not connected to the cracks in the bottom plate damage zone; the lower part of the isolation protection zone 2 is the water injection expansion zone 1, and the rock layer in the water injection expansion zone 1 can have the property of swelling when exposed to water. The rock layer adjacent to the isolation protection zone 2 and the water injection expansion zone is selected from a rock layer that does not swell when exposed to water, and the water injection expansion zone 1 is generally selected from a rock layer rich in clay minerals (montmorillonite, illite, etc.);

[0018] S2: constructing a directional drill hole 7 in the tunnels on one side or both sides of the working face, wherein the horizontal section of the directional drill hole 7 is constructed in the water injection expansion zone 1, and the directional drill hole 7 is constructed in the direction of the opposite tunnel in the width direction of the working face. The directional drill hole 7 is preferably parallel to the width direction of the working face, and the directional drill hole 7 is constructed in the direction of the eye cutting in the advancing direction of the working face (i.e., the length direction of the working face);

[0019] S3: Install a packer 9 at the orifice of the directional drill hole 7 to seal the rock formations corresponding to the bottom plate damage zone and the isolation protection zone 2 to prevent water from penetrating into non-target layers through the directional drill hole 7 during water injection;

[0020] S4: When the working face passes through a horizontal section of a directional drilling hole 7 and before reaching the opening of the directional drilling hole 7 (such as Figure 2 The solid line position in the middle working face), a high-pressure pump is used to first inject an appropriate amount of water into the directional borehole 7 at high pressure to form a fissure 8 in the water injection expansion zone 1, and then the water injection pressure is reduced and the water injection amount is controlled to reach the water absorption limit of the rock formation in the water injection expansion zone 1; after the water injection, the rock formation in the water injection expansion zone 1 undergoes a water absorption and expansion effect, and the volume of the water injection expansion zone 1 expands, lifting the isolation protection zone 2, the bottom plate uniform fracture zone 3 and the bottom plate damage zone 4; among them, the bottom plate uniform fracture zone 3 and the bottom plate crushing and expansion zone 4 will increase the damage range under the volume expansion of the water injection expansion zone 1, and the looseness of the irregular rock blocks in the bottom plate crushing and expansion zone 4, that is, the degree of crushing and expansion, will also increase, further enriching the goaf space, and together with the volume expansion of the water injection expansion zone 1, offset the space formed by part of the coal seam mining, thereby reducing the equivalent mining height of the coal seam, reducing the height of the collapse zone 6 and the fracture zone 5, and controlling the sinking of the overlying rock strata to a certain extent, thereby reducing the surface subsidence.

[0021] 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 slowing mining subsidence by water injection expansion and arching of bottom rock strata, characterized in that: The steps include: S1: Determine the range of the floor damage zone below the coal seam, select a rock layer of a certain thickness below the floor damage zone as an isolation protection zone, the isolation protection zone will be arched after the water injection expansion zone expands, but no cracks will be generated to connect to the upper floor damage zone, or the generated cracks will not be connected to the cracks in the floor damage zone; the lower part of the isolation protection zone is a water injection expansion zone, the rock layer in the water injection expansion zone can have the property of swelling when exposed to water, and the rock layer adjacent to the isolation protection zone and the water injection expansion zone is selected to be a rock layer that does not swell when exposed to water; S2: construct directional drilling holes in the tunnels on one side or both sides of the working face, wherein the horizontal section of the directional drilling holes is constructed in the water injection expansion zone, the directional drilling holes are constructed in the direction of the opposite tunnel in the width direction of the working face, and the directional drilling holes are constructed in the direction of the eye cutting in the advancing direction of the working face; S3: Install a packer at the orifice of the directional drilling hole to seal the rock formations corresponding to the bottom plate damage zone and the isolation protection zone; S4: After the working face passes through a horizontal section of a directional borehole and before reaching the orifice of the directional borehole, high-pressure water is first injected into the directional borehole to form cracks in the water injection expansion zone, and then the water injection pressure is reduced and the water injection volume is controlled to reach the water absorption limit of the water injection expansion zone.

2. The method for slowing mining subsidence by water injection expansion and reverse arching of bottom rock strata according to claim 1 is characterized in that: In step S1, the water injection expansion zone selects a rock layer rich in clay minerals.

3. The method for slowing mining subsidence by water injection expansion and reverse arching of bottom rock strata according to claim 1 is characterized in that: In step S2, the directional drilling is parallel to the width direction of the working surface.

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