A method for controlling the expansion and settlement of bottom rock strata through chemical modification
By chemically modifying and expanding the bottom rock strata, and utilizing expansive mineral activators and directional drilling grouting technology, the high cost and low efficiency problems of coal mining subsidence control have been solved, achieving low-cost and high-efficiency subsidence control.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA UNIV OF MINING & TECH
- Filing Date
- 2025-01-07
- Publication Date
- 2026-05-26
AI Technical Summary
Existing methods for controlling coal mining subsidence suffer from high costs and low efficiency, especially in water-scarce or ecologically fragile areas. Backfilling mining technology increases equipment investment and operating costs, and its complex construction also affects mining efficiency.
By chemically modifying the base rock strata to induce expansion, expansive mineral activators, gas expansion agents, and gel-forming agents are used to react and generate expansion in the base rock strata. Chemical agents are then injected into the rock strata through directional drilling and grouting techniques to form an expansion zone that lifts the base rock strata and reduces surface subsidence.
It achieves low-cost and efficient subsidence control, adapts to different rock strata conditions, is simple to operate, has a controllable expansion effect, and reduces surface subsidence and ecological damage.
Smart Images
Figure CN119777874B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of coal mining subsidence control, specifically a method for controlling subsidence through chemical modification and expansion of the bottom rock strata. Background Technology
[0002] With the continuous advancement of coal mining technology and equipment, coal mine production efficiency and capacity have been significantly improved, playing a vital role in ensuring energy security and promoting rapid economic development. However, at the same time, surface subsidence, as one of the direct consequences of coal mining, not only damages land and groundwater resources in mining areas but also affects regional agricultural production and the normal operation of ecosystems. Therefore, how to effectively control and manage surface subsidence and ecological damage while improving coal mining efficiency has become a crucial and urgent problem to be solved in the mining sector.
[0003] Currently, to address issues such as surface subsidence and ecological damage in mining areas, some mines are employing backfill mining technology. During mining, solid, paste, or high-water materials are filled into the goaf behind the working face to form a backfill body that supports the overlying rock strata, effectively controlling surface subsidence and reducing ecological damage. Especially in water-scarce or ecologically fragile areas, backfill mining technology can, to some extent, balance the conflict between resource development and environmental protection. However, this technology also has limitations. For example, it requires the construction of independent backfill pipeline systems in the mining area or on the surface, significantly increasing equipment investment and operating costs, and potentially causing interference between mining and backfilling operations, affecting mining efficiency. Furthermore, the complex preparation, transportation, and injection processes of backfill materials place high demands on the performance of the materials and the supporting equipment, further increasing the difficulty of implementing the technology. Summary of the Invention
[0004] To address the high cost and low efficiency of current subsidence control methods, this invention proposes a subsidence reduction control method based on chemical modification and expansion of the base strata, comprising the following steps:
[0005] S1: Determine the extent of the floor failure zone below the coal seam, and select a rock layer of a certain thickness below the floor failure zone as an isolation protection zone. The isolation protection zone arches upward after the chemically modified expansion zone expands, but does not generate fissures that connect to the upper floor failure zone, or the generated fissures do not connect with the fissures in the floor failure zone. The lower part of the isolation protection zone is a chemically modified expansion zone, and the rock layer in the chemically modified expansion zone can react chemically with the chemical agent to produce expansion.
[0006] S2: Select the chemical agent for expansion based on the mineral composition of the rock strata in the chemically modified expansion zone;
[0007] S3: Construct directional boreholes in the roadways on one or both sides of the working face. The horizontal section of the directional borehole is constructed in the chemically modified expansion zone. The directional borehole is constructed in the direction of the opposite roadway in the width direction of the working face and in the direction of the cut-in in the working face advancing direction. After the construction is completed, the chemically modified expansion zone is fracturing through the directional borehole.
[0008] S4: After the working face has passed a certain horizontal section of a directional borehole and before reaching the borehole opening, chemical agents are injected into the chemically modified expansion zone through directional grouting boreholes.
[0009] Preferably, in step S2, the chemical agent includes an expansive mineral activator, a gas expansive agent, and a gel forming agent; the expansive mineral activator is a sodium-based or calcium-based solution, the gas expansive agent is sodium bicarbonate and acid solution, and the gel forming agent is sodium silicate and calcium chloride solution.
[0010] Preferably, in step S3, the directional drilling is parallel to the width direction of the working face.
[0011] Preferably, in step S4, the hole is sealed when the working face passes the opening of the directional drilling hole.
[0012] The inventive point and beneficial effects of this invention: This invention chemically modifies the underlying rock strata to induce expansion, thereby lifting the underlying rock strata to support the goaf, thus reducing the subsidence of the overlying rock strata and controlling surface subsidence. This invention achieves active expansion through chemical modification, allowing for flexible selection of chemical agents and adjustment of the expansion scheme according to different rock strata conditions. The overall operating cost is low, and the expansion effect is controllable. Attached Figure Description
[0013] Figure 1 This is a schematic cross-sectional view of the subsidence control mechanism of the expansion zone of the bottom rock strata chemically modified in this invention;
[0014] Figure 2 This is a schematic diagram of the directional drilling construction plan for the chemically modified expansion zone of the bottom rock strata in this invention;
[0015] In the diagram: Chemically modified expansion zone-1, isolation and protection zone-2, uniform fracture zone of the base plate-3, fracture expansion zone of the base plate-4, fracture zone-5, chemical agent-6, hydraulic fracturing fracture-7, directional drilling-8, collapse zone-9. Detailed Implementation
[0016] To better understand the technical content of this invention, specific embodiments are described below in conjunction with the accompanying drawings. Various aspects of this invention are described with reference to the accompanying drawings, which illustrate numerous illustrative embodiments. The embodiments of this invention are not limited to those shown in the drawings. It should be understood that this invention is implemented through any of the various concepts and embodiments described above, as well as the concepts and embodiments described in detail below, because the concepts and embodiments disclosed in this invention are not limited to any particular implementation. Furthermore, some aspects of this invention can be used alone or in any suitable combination with other aspects disclosed in this invention.
[0017] To address the high cost and low efficiency issues of current subsidence control methods, such as... Figure 1-2 As shown, this invention proposes a method for controlling the expansion and subsidence reduction of the bottom rock strata through chemical modification; this method is applicable to mining conditions where there are easily chemically modified and expandable rock strata in the coal seam floor; the specific steps include:
[0018] S1: Based on the lithology and thickness of the floor strata, the extent of the floor failure zone below the coal seam is determined. This failure zone includes a floor fracture and expansion zone 4 and a floor uniform fracture zone 3. In the floor fracture and expansion zone 4, the floor strata are fractured in an irregular network pattern, with relatively small fragments. Due to the gaps between the fragments, they exhibit some expansion characteristics. In the floor uniform fracture zone 3, the floor strata exhibit regular longitudinal and transverse fractures, forming relatively large, regular fragments. This failure zone can form water-conducting channels. Below the failure zone, a rock layer of a certain thickness (usually containing multiple rock layers) is selected as an isolation protection zone 2. After the chemically modified expansion zone expands, the isolation protection zone 2 arches upward, but does not generate cracks that connect to the failure zone of the upper base plate, or the generated cracks do not connect with the cracks of the failure zone of the base plate. The lower part of the isolation protection zone 2 is the chemically modified expansion zone 1. The rock layer in the chemically modified expansion zone 1 can react chemically with the chemical agent 6 to produce expansion, such as rock layers containing mineral components such as bentonite, kaolinite, and montmorillonite.
[0019] S2: Based on the mineral composition of the chemically modified expansion zone 1 rock stratum, expansion chemical agent 6 is selected. This chemical agent mainly includes an expansion mineral activator, a gas expansion agent, and a gel forming agent. The expansion mineral activator uses sodium-based and calcium-based solutions (NaCl, CaCl2), which provide exchangeable cations (Na+, CaCl2, Na+, CaCl2, etc.). + Ca 2+ This promotes the expansion of expansive minerals; the gas expansion agent, such as sodium bicarbonate and acid, reacts to release carbon dioxide gas and generate gas expansion; the gel forming agent, such as sodium silicate and calcium chloride solution, reacts to form a gel to fill cracks and accompanied by expansion.
[0020] S3: Construct directional boreholes 8 in the roadways on one or both sides of the working face. The horizontal section of the directional boreholes 8 is constructed in the chemically modified expansion zone 1. The directional boreholes 8 are constructed in the direction of the opposite roadway in the width direction of the working face. Preferably, the directional boreholes are parallel to the width direction of the working face. The directional boreholes 8 are constructed in the direction of the cut-in in the working face advancing direction (i.e., the length direction of the working face). After the construction is completed, the chemically modified expansion zone 1 is fracturing through the directional boreholes 8 to form fracturing fractures 7 in the chemically modified expansion zone 1. The fracturing methods include carbon dioxide blasting, hydraulic fracturing, etc.
[0021] S4: When the working face has passed the horizontal section of a certain directional borehole 8 and before reaching the opening of the directional borehole 8 (e.g. Figure 2 (Solid line position within the working face), chemical agent 6 is injected into the chemically modified expansion zone 1 through directional grouting borehole 8, and the grouting pressure is controlled to ensure that the chemical agent 6 can be evenly distributed and penetrate into the rock strata in the chemically modified expansion zone 1; the chemical agent 6 reacts with the rock strata in the chemically modified expansion zone 1, the volume of the chemically modified expansion zone 1 expands, and the isolation protection zone 2, the uniform fracture zone 3 of the floor and the floor failure zone 4 are lifted; among them, the uniform fracture zone 3 of the floor and the floor failure expansion zone 4 will increase the failure range under the volume expansion of the chemically modified expansion zone 1, and the looseness of the irregular rock blocks in the floor failure expansion zone 4, that is, the degree of fragmentation, will also increase, further filling the goaf space, and together with the volume expansion of the chemically modified expansion zone 1, offsetting part of the space formed by coal seam mining, thereby reducing the equivalent mining height of the coal seam, reducing the height of the caving zone 9 and the fracture zone 5, controlling the subsidence of the overlying strata, and thus reducing surface subsidence.
[0022] This invention is not limited to the preferred embodiments described above. Anyone can derive other methods in various forms under the guidance of this invention. Any technical solution that is the same as or similar to this application falls within the protection scope of this invention.
Claims
1. A method for controlling the expansion and settlement reduction of bottom rock strata through chemical modification, characterized in that, Includes the following steps: S1: Determine the extent of the floor failure zone below the coal seam. The floor failure zone includes a floor fracture expansion zone and a floor uniform fracture zone. In the floor fracture expansion zone, the floor strata are fractured in an irregular network pattern, and the fractured blocks are relatively small. Due to the gaps between the fractured blocks, they have a certain expansion characteristic. In the floor uniform fracture zone, the floor strata have regular longitudinal and transverse fractures, forming relatively large, regular fractured blocks. The floor failure zone can form water-conducting channels. Below the floor failure zone, a rock layer of a certain thickness is selected as an isolation and protection zone. After the chemically modified expansion zone expands, the isolation and protection zone arches upward, but does not generate fractures that connect to the upper floor failure zone, or the generated fractures do not connect with the fractures in the floor failure zone. The lower part of the isolation and protection zone is the chemically modified expansion zone, and the rock layers in the chemically modified expansion zone can react chemically with the chemical agent to produce expansion. S2: Select the chemical agent for expansion based on the mineral composition of the rock strata in the chemically modified expansion zone; S3: Construct directional boreholes in the roadways on one or both sides of the working face. The horizontal section of the directional borehole is constructed in the chemically modified expansion zone. The directional borehole is constructed in the direction of the opposite roadway in the width direction of the working face, and in the direction of the cut-in in the working face advancement direction. The directional borehole is parallel to the width direction of the working face. After construction, the chemically modified expansion zone is fracturing through the directional borehole. S4: After the working face has passed a certain horizontal section of a directional borehole and before reaching the borehole opening, chemical agents are injected into the chemically modified expansion zone through the directional borehole. Under the volume expansion of the chemically modified expansion zone, the uniform fracture zone and the fractured expansion zone of the floor will increase their damage range, and the looseness of the irregular rock blocks in the fractured expansion zone, i.e., the degree of fragmentation, will also increase, filling the entire goaf space. Together with the volume expansion of the chemically modified expansion zone, it will offset part of the space formed by coal seam mining, thereby reducing the equivalent mining height of the coal seam, lowering the height of the caving zone and fracture zone, and thus reducing the subsidence of the overlying strata and controlling surface subsidence.
2. The method for controlling the expansion and subsidence reduction of the bottom rock strata through chemical modification according to claim 1, characterized in that, In step S2, the chemical agents include an expansive mineral activator, a gas expansive agent, and a gel forming agent; the expansive mineral activator is a sodium-based or calcium-based solution, the gas expansive agent is sodium bicarbonate and acid solution, and the gel forming agent is sodium silicate and calcium chloride solution.
3. The method for controlling the expansion and subsidence reduction of the bottom rock strata through chemical modification according to claim 1, characterized in that, In step S4, the hole is sealed when the working face is pushed past the orifice of the directional borehole.