Freezing type slope leaning mining method for water-containing slope

Abstract

The invention discloses a water-bearing side slope freezing type wall-leaning mining method. The method comprises the steps of underground water layer exploration, freezing circulation system construction, wall-leaning mining after freezing, freezing relieving, underground water system recovery and the like. According to the invention, multiple types of wells are matched with the freezing communication network, so that underground water can be effectively frozen; cold energy transmission materials are completed through underground water in the area, local materials are used, and the implementation cost is reduced; a waterproof retaining wall is formed after freezing, so that relative dryness of the slope can be ensured, and the stability is improved; after the freezing effect is relieved, the underground water recovers to run through, and permanent interference on underground water circulation in the area is avoided; the semi-sealed well wall prevents high-salinity water from reversely permeating to underground water on one side deviating from the pit bottom, and mineral pollution to the underground water can be effectively avoided in cooperation with monitoring dilution; the method is implemented in an extremely small range of a strip mine mining area, mine production arrangement is not affected, and potential safety hazards do not exist after dumping coverage; the implementation process does not affect the mine production order.

Description

Technical Field

[0001] This invention relates to a side-mounted mining method, specifically a frozen side-mounted mining method for water-bearing slopes. Background Technology

[0002] Coal undercut on open-pit mine slopes is a significant factor affecting resource recovery rates. A larger slope angle results in less coal undercut and a higher resource recovery rate. The slope angle is primarily determined by the properties of the strata materials. With similar rock and soil properties, higher water content in the strata leads to lower stability, forcing a slower slope angle and increasing the amount of coal undercut. Currently, when mining strata with high water content in open-pit mines, two methods are commonly used: one is pre-drainage, which involves drilling vertical wells as drainage wells within a certain range outside the outer edge of the slope to continuously extract groundwater from the strata, ensuring the dryness of the slope soil and rock and facilitating mining safety. The effectiveness of this method is highly correlated with the deployment density of drainage wells and the pumping power, and it cannot achieve absolute slope dryness. The control precision of water level and moisture content within the slope is poor, and there are dangers during side-mounted mining operations. Secondly, a waterproof retaining wall can be constructed by excavating or grouting inside the slope in advance to block the seepage channels of groundwater before mining. This method can keep the slope relatively dry by blocking the recharge, but it requires a large amount of excavation or grouting drilling, which has a long construction period, large investment, and causes great damage to the slope. Moreover, the groundwater system in the area cannot be restored after mining, which seriously affects the groundwater ecosystem of the mining area. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a frozen-side mining method for water-bearing slopes, which achieves relative dryness of the slope, high slope stability, minimal damage to the slope, and allows groundwater to be restored after mining, thereby reducing the impact on the groundwater ecosystem of the mining area.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for frozen side-mounted mining of water-bearing slopes, comprising the following steps: Groundwater exploration: One of the 3rd to 8th steps above the coal seam is designated as the exploration step. Exploration holes are drilled on the platform surface of the exploration step to investigate the groundwater situation in the slope and determine the location and height of the groundwater layer. During the approach process, the lowest step that does not require approach is designated as the critical step. Constructing a refrigeration cycle system: After enlarging the exploration boreholes, they are used as high-pressure water injection wells. High-pressure water injection pipes are installed in the high-pressure water injection wells. Part of the well wall and well cover of the high-pressure water injection well are sealed, and the remaining part of the well wall is semi-sealed. The high-pressure water injection wells are set up continuously at intervals along the direction of the open-pit mine. Drill holes downwards on the surface of the critical step platform and deploy pumps inside to form low-pressure pumping wells; the low-pressure pumping wells and high-pressure injection wells are arranged side by side in a one-to-one correspondence; drill holes in the unsealed well wall of the high-pressure injection wells to connect the low-pressure pumping wells corresponding to the high-pressure injection wells and the low-pressure pumping wells adjacent to the low-pressure pumping wells corresponding to the high-pressure injection wells, forming a connected network. Frozen and then extracted using a support structure: Groundwater is pumped to the surface through low-pressure pumping wells, concentrated to obtain high-grade mineral water, and then cooled to below 0°C. It is then injected into high-pressure injection wells. The high-grade mineral water flows along the interconnected network. Due to the pressure of the high pressure, it also flows in the gaps between the high-pressure injection wells and the low-pressure pumping wells. During the flow, the coldness carried by the high-grade mineral water is gradually released, reducing the temperature of the groundwater and the surrounding rocks until they eventually freeze. The unfrozen high-grade mineral water will collect in each low-pressure pumping well, be pumped out by pumps, and participate in the next cycle. After freezing, starting from the bottom of the pit, the stripping steps above the coal seam are excavated and side-mounted mining is carried out; Defreezing and restoring the groundwater system: After the slope is mined along the side, the open-pit mine's spoil heap will advance and cover the bottom of the slope. At this point, the area that has already been mined along the side will stop freezing. As the spoil heap continues to advance and completely covers the slope, the freezing effect will gradually dissipate, and the groundwater will be restored to flow.

[0005] Furthermore, the step above the exploration step serves as a monitoring step. A hole is drilled downwards on the surface of this platform, and a groundwater mineralization monitoring instrument and a pump are deployed inside to form a monitoring dilution well. Every two monitoring dilution wells correspond to one high-pressure water injection well, and the monitoring dilution wells are located on the central axis of the line connecting two adjacent high-pressure water injection wells.

[0006] Furthermore, during the implementation of the back-side mining, a monitoring dilution well is activated, and the mineral content concentration of the groundwater in the area is monitored in real time using a mineralization monitoring instrument. When the concentration exceeds three times the original concentration of the groundwater in the area, a pump is started to remove the high-mineral water from the reverse seepage.

[0007] Furthermore, the high-pressure water injection well has a diameter of 300mm-600mm and a depth of 2-3m below the boundary of the ultra-deep groundwater layer; the low-pressure pumping well has a diameter of 200mm-400mm and a depth of 2-3m below the boundary of the ultra-deep groundwater layer.

[0008] Furthermore, the high-pressure water injection well is sealed from the wellhead down to the well wall 2-3m below the surface of the groundwater layer.

[0009] Furthermore, the remaining portion of the well wall is partially sealed, meaning only the half of the well wall facing away from the bottom of the pit is sealed.

[0010] Furthermore, the high-quality mineral water is pumped to the surface and then cooled to between -3°C and -5°C.

[0011] Compared with existing technologies, this invention, with its multi-type wells and frozen interconnected network, can effectively freeze groundwater; the cold energy transfer material relies on local groundwater, reducing implementation costs through on-site material sourcing; the waterproof retaining wall formed after freezing ensures relative dryness of the slope, improving slope stability; after the freezing effect is thawed, groundwater reconnects, avoiding permanent interference with the groundwater cycle in the area; the semi-sealed well wall prevents high-mineralized water from seeping back into the groundwater on the side away from the pit bottom, and combined with monitoring and dilution, effectively avoids mineral contamination of the groundwater; the invention is implemented within a very small area of ​​the open-pit mining area, without affecting mine production arrangements, and poses no safety hazards after the spoil heap is covered; the implementation process of this invention is integrated with the open-pit mining production process, without affecting the mine's production order; the semi-high seepage barrier retaining wall can delay the time it takes for water to enter the spoil heap from the slope, ensuring the safety of the spoil heap slope, without affecting the water system connectivity. Attached Figure Description

[0012] Figure 1 This is a cross-sectional view of the present invention; Figure 2 This is a schematic diagram showing the positional relationship between the high-pressure water injection well, the low-pressure water pumping well, and the monitoring dilution well in this invention; Figure 3 This is a top view of the present invention; Figure 4 This is a schematic diagram of a seepage barrier retaining wall structure; In the diagram: 1-slope; 2-coal seam; 3-exploration bench; 4-groundwater layer; 5-critical bench; 6-high-pressure water injection well; 7-open-pit mine advance direction; 8-spoil dump; 9-working side; 10-low-pressure pumping well; 11-connecting network; 12-monitoring bench; 13-monitoring dilution well; 14-pit bottom; 15-seepage barrier wall. Detailed Implementation

[0013] The invention will now be further described with reference to the accompanying drawings.

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] like Figures 1 to 3As shown, the present invention provides a technical solution that is particularly suitable for open-pit mining in areas with low temperatures in the north; it includes four steps: groundwater exploration, construction of a freezing circulation system, mining along the side after freezing, and defreezing to restore the groundwater system.

[0016] Groundwater exploration: Exploration step 3 is designated as one of the 3rd to 8th steps above coal seam 2 below slope 1, where the side slope requires mining. The lithology of exploration step 3 should be as similar as possible to that of groundwater layer 4, ensuring that it does not cross the interface between loose and rock layers. Exploration holes are drilled vertically downwards on the platform surface of exploration step 3 to investigate the groundwater situation within slope 1 and determine the location and height of groundwater layer 4. The greater the thickness of coal seam 2, the higher exploration step 3 should be selected; the smaller the angle of the water-bearing slope 1, the higher exploration step 3 should be selected. During side slope mining, the lowest step that does not need to be mined is designated as critical step 5. When groundwater layer 4 is located at a high position, the first step above groundwater layer 4 is designated as critical step 5. Simultaneously, exploration step 3 must be at least one step higher than critical step 5 and no more than four steps higher, primarily to provide operational space for subsequent processes. The data selection here is positively correlated with the groundwater volume of slope 1.

[0017] Constructing a refrigeration cycle system: After enlarging the exploration borehole and treating the ultra-deep groundwater layer 4, it is used as a high-pressure water injection well 6. The diameter of the high-pressure water injection well 6 is 300mm-600mm, and its depth is 2-3m below the lower boundary of the ultra-deep groundwater layer 4. A high-pressure water injection pipe is installed in the high-pressure water injection well 6. The well wall and well cover of the high-pressure water injection well 6 from the wellhead down to 2-3m from the upper surface of the groundwater layer 4 are sealed. The remaining part of the well wall is partially sealed, that is, only the half of the well wall facing away from the bottom of the pit 14 is sealed. The high-pressure water injection well 6 is set continuously at intervals along the open-pit mine advance direction 7, and the spacing is 1-3 times the thickness of the aquifer. The specific data is positively correlated with the degree of rock fissure development in the groundwater layer 4. The high-pressure water injection well 6 extends from the spoil heap 8 to the working side 9 and is laid out as the working side 9 extends.

[0018] On the surface of the critical step 5 platform, drill vertically downwards with a diameter of 200mm-400mm, 2-3m below the lower boundary of the ultra-deep groundwater layer 4. Deploy pumps inside to form low-pressure pumping wells 10. The low-pressure pumping wells 10 are positioned side-by-side with the high-pressure injection wells 6, one low-pressure pumping well 10 corresponding to one high-pressure injection well 6. Since the high-pressure injection wells 6 require sealing, resulting in higher investment costs, to consider cost, one high-pressure injection well 6 can correspond to two low-pressure pumping wells 10. Figure 2 and Figure 3As shown, holes with a diameter of less than 300mm are drilled in the unsealed well wall of the high-pressure water injection well 6, and connected to the low-pressure pumping well 10 corresponding to the high-pressure water injection well 6, the low-pressure pumping well 10 corresponding to the high-pressure water injection well 6, and the adjacent low-pressure pumping well 10, forming a connected network 11.

[0019] The step above exploration step 3 is designated as monitoring step 12. A vertical borehole with a diameter of 200mm-400mm is drilled on the surface of this platform to the lower boundary of the ultra-deep groundwater layer 4, 2-3m below. A groundwater mineralization monitoring instrument and a pump are deployed inside to form a monitoring dilution well 13. Every two monitoring dilution wells 13 correspond to one high-pressure water injection well 6, and the monitoring dilution well 13 is located on the central axis of the line connecting two adjacent high-pressure water injection wells 6.

[0020] Frozen and then extracted using a support structure: Because of constant contact with minerals, the groundwater in the mining area is generally highly mineralized. After the groundwater is pumped to the surface through the low-pressure pumping well 10, it is concentrated to further increase the mineral content in the groundwater, thereby lowering the freezing point of the water and obtaining high-mineral water, which is then used as a cold energy transfer medium. The high-mineral water is then cooled to between -3°C and -5°C and injected into the high-pressure injection well 6 through the high-pressure injection pipe. The high-mineral water mainly flows along the connecting network 11. At the same time, due to the pressure of the high pressure, the high-mineral water also flows in the groundwater gaps between the high-pressure injection well 6 and the low-pressure pumping well 10. During the flow, the cold energy carried by the high-mineral water is gradually released, lowering the temperature of the groundwater and the surrounding rocks and eventually freezing them, forming a waterproof barrier similar to that mentioned in the background art. The unfrozen high-mineral water will collect in each low-pressure pumping well 10, be pumped out by the pump, and participate in the next cycle.

[0021] The frozen, waterproof retaining wall prevents groundwater from further seeping into slope 1, keeping slope 1 dry and improving its stability, thus providing stability support for the side-side mining. After freezing, starting from the bottom of the pit 14, the stripping benches of coal seam 2 and above are excavated to implement side-side mining; the side-side mining starts from one side of the spoil heap 8 and extends towards the working side 9. The frozen length of slope 1 must be 1.5 times the length of the side-side mining area to ensure the stability of slope 1.

[0022] Because the high-mineralized water is injected under pressure, even though the semi-sealed well wall at the bottom of the high-pressure injection well 6 can prevent the high-mineralized water from seeping back into the groundwater on the side away from the pit bottom 14 to some extent, it cannot completely prevent it. To solve this problem, during the back-side mining process after freezing, the monitoring dilution well 13 is activated. The mineral content concentration of the groundwater in this area is monitored in real time using a mineralization monitoring instrument. When the concentration exceeds three times the original concentration of the groundwater in this area, the pump is activated to promptly remove the back-seeping high-mineralized water and avoid groundwater pollution.

[0023] During the exploration phase, the water pressure under natural groundwater conditions is analyzed. During the freezing cycle, the water pressure in the high-pressure injection well 6 is controlled to be no greater than 1.2 times the natural water pressure (or no greater than 1.0 times when the natural water pressure is high). This prevents the injected high-mineral water from seeping into the natural water body, allowing only mineral diffusion within the water. The water pressure in the low-pressure pumping well 10 is controlled to be less than 0.5 times the injection well pressure, guiding the water flow.

[0024] like Figure 4 As shown, after the slope is mined, a semi-high seepage barrier wall 15 is constructed using clay from the mining area. Its height is equivalent to 1 / 2 to 2 / 3 of the height of the groundwater layer 4. A larger value is used when the water volume in the water layer is high. The purpose is to block groundwater in the initial stage after the slope is mined. When the water level rises to a certain level, it overflows the seepage barrier wall 15, achieving water system connectivity. This design delays the time it takes for water to enter the spoil heap 8 from the slope 1, ensuring the safety of the spoil heap 8 slope, without affecting the water system connectivity.

[0025] Defreezing and restoring the groundwater system: After the side-mounted mining is completed, the open-pit mine spoil heap 8 advances to cover the bottom of slope 1. At this time, the area where the side-mounted mining has been completed stops freezing, and the relevant equipment is removed. After the spoil heap 8 continues to advance and completely covers the slope, the freezing effect will naturally and gradually dissipate, and the groundwater will be restored to connectivity, thus avoiding permanent interference with the groundwater cycle in the area.

[0026] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0027] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any minor modifications, equivalent substitutions, and improvements made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for mining water-bearing slopes by freezing and backing, characterized in that, Includes the following steps: One of the steps from the 3rd to the 8th steps above the coal seam (2) is designated as the exploration step (3). Exploration holes are drilled on the platform surface of the exploration step (3) to investigate the groundwater situation in the slope (1) and determine the location and height of the groundwater layer (4). During the process of leaning against the slope, the bottommost step that does not need to lean against the slope is designated as the critical step (5). After the exploration hole is enlarged, it is used as a high-pressure water injection well (6). A high-pressure water injection pipe is installed in the high-pressure water injection well (6). Part of the well wall and well cover of the high-pressure water injection well (6) are sealed, and the remaining part of the well wall is semi-sealed. The high-pressure water injection well (6) is set up continuously at intervals along the direction of the open-pit mine advance (7). Drill holes downward on the surface of the critical step (5) platform and deploy pumps inside to form low-pressure pumping wells (10); the low-pressure pumping wells (10) and high-pressure injection wells (6) are arranged side by side in a one-to-one correspondence. Drill holes on the unsealed well wall of the high-pressure injection well (6) to connect the low-pressure pumping well (10) corresponding to the high-pressure injection well (6) and the low-pressure pumping well (10) adjacent to the low-pressure pumping well (10) corresponding to the high-pressure injection well (6) to form a connecting network (11). Groundwater is pumped to the surface through low-pressure pumping wells (10) to concentrate and obtain high-mineral water, which is then cooled to below 0°C and injected into high-pressure injection wells (6). The high-mineral water flows along the connecting network (11). Due to the pressure of the high pressure, it also flows in the groundwater gap between the high-pressure injection wells (6) and the low-pressure pumping wells (10). During the flow, the cold energy carried by the high-mineral water is gradually released, which reduces the temperature of the groundwater and the surrounding rocks and eventually freezes. The unfrozen high-mineral water will be collected in each low-pressure pumping well (10), pumped out by a pump to form and participate in the next cycle. After freezing, starting from the bottom of the pit (14), the stripping steps of the coal seam (2) and above are excavated and side-mounted mining is carried out; After the side-mounted mining is completed, the open-pit mine spoil heap (8) advances to cover the bottom of the slope (1). At this time, the area that has been mined along the side-mounted mining stop freezing. After the spoil heap (8) continues to advance and completely covers the slope (1), the freezing effect will gradually be relieved and the groundwater will be restored to flow.

2. The method for frozen side-mounted mining of water-bearing slopes according to claim 1, characterized in that, The step above the exploration step (3) is used as the monitoring step (12). A hole is drilled downward on the surface of the platform, and a groundwater mineralization monitoring instrument and a pump are deployed inside to form a monitoring dilution well (13). Every two monitoring dilution wells (13) correspond to one high-pressure water injection well (6), and the monitoring dilution well (13) is located on the central axis of the line connecting two adjacent high-pressure water injection wells (6).

3. The method for frozen side-mounted mining of water-bearing slopes according to claim 2, characterized in that, When the mining is carried out, the monitoring dilution well (13) is activated, and the mineral content concentration of the groundwater in the area is monitored in real time by the mineralization monitoring instrument. When the concentration exceeds three times the original concentration of the groundwater in the area, the pump is started to pump away the high mineral water from the reverse infiltration.

4. The method for frozen side-mounted mining of water-bearing slopes according to claim 1, characterized in that, The high-pressure water injection well (6) has a diameter of 300mm-600mm and a depth of 2-3m below the boundary of the ultra-deep groundwater layer (4); the low-pressure pumping well (10) has a diameter of 200mm-400mm and a depth of 2-3m below the boundary of the ultra-deep groundwater layer (4).

5. The method for frozen side-mounted mining of water-bearing slopes according to claim 1, characterized in that, The high-pressure water injection well (6) is sealed from the wellhead down to the well wall 2-3m away from the upper surface of the groundwater layer (4).

6. The method for frozen side-mounted mining of water-bearing slopes according to claim 5, characterized in that, The remaining part of the well wall is partially sealed, meaning only the half of the well wall facing away from the bottom of the pit (14) is sealed.

7. The method for frozen side-mounted mining of water-bearing slopes according to claim 5, characterized in that, The high-quality mineral water is pumped to the surface and then cooled to between -3°C and -5°C.

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