A method for water storage in sandy sand mining areas

Abstract

This invention belongs to the field of coal mining technology, specifically relating to a water storage method in aeolian sandy aquifer mining areas. This invention innovatively utilizes directional drilling to connect aeolian sandy aquifers in open-area zones with those in non-open-area zones, improving rapid cross-regional water recharge and significantly increasing the total water storage capacity of the entire mining area. To prevent large amounts of water from being discharged through surface springs, coal pillars are used to alter the original seepage path of the aquifers. The subsidence of the coal pillar area is smaller than that of the mining area, blocking or reducing spring discharge and increasing the migration path of groundwater, thereby increasing infiltration. This invention increases the amount of water resources infiltrated from aeolian sandy ...

Description

Technical Field

[0001] This invention belongs to the field of coal mining technology, specifically relating to a water storage method in wind-blown sandy mining areas. Background Technology

[0002] The vast sandy landforms of Northwest my country contain abundant coal resources, but these mining areas lack usable water resources, limiting water supply for production, ecology, and daily life. Therefore, water storage in these sandy mining areas is crucial for the region's social progress and economic development. Traditional methods for addressing this problem include utilizing water storage in goaf areas formed during coal mining, transferring and storing aquifers before mining, and reconstructing aquifers after coal mining. However, these methods still have the following problems:

[0003] 1) Water is stored in the goaf formed by coal mining. Water resources enter the coal mining system and are inevitably polluted to varying degrees, resulting in high costs for water pollution control.

[0004] 2) The main object of aquifer transfer and storage before coal mining is the groundwater overlying the coal seam. The atmospheric precipitation infiltration conditions in sandy landforms are relatively good, but the underlying impermeable soil layer in sandy areas results in a limited supply of water to the underlying aquifer, so the amount transferred and stored is very limited.

[0005] 3) The fracture network generated by coal mining is relatively complex. Under natural conditions, the self-healing time of the aquitard is too long. Artificial reconstruction of the aquitard requires a large amount of grouting and is therefore expensive.

[0006] In addition, when the water storage in sandy sand dunes is large, there is a risk of sudden water inrush and sand collapse. Summary of the Invention

[0007] The purpose of this invention is to overcome the above-mentioned problems existing in the traditional technology and to provide a water storage method for sandy beach mining areas.

[0008] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution:

[0009] A method for water storage in wind-blown sandy mining areas includes the following steps:

[0010] S1. Use geophysical exploration techniques to delineate the skylight areas of loose sand aquifers and weathered bedrock aquifers;

[0011] S2. Conduct a hydrogeological survey of the sandy beach area in the skylight area to determine the spatial location of the sandy beach springs.

[0012] S3. Determine the groundwater recharge direction of the spring points identified in step S2;

[0013] S4. Determine the coal mining height in the skylight area;

[0014] S5. When mining coal seams in the skylight area, the coal mining face is set at the boundary of the skylight area. Hydraulic fracturing technology is used for manual roof cutting. Within the skylight area, the roof is manually cut at intervals of 0.5 to 0.8 times the step distance of the coal mining cycle.

[0015] S6. Directional drilling is carried out underground in the coal mine. The horizontal section of the directional borehole passes through the bottom of the sandy aquifer in the skylight area and connects with the sandy aquifer in the non-skylight area. A valve is installed in the directional borehole located in the skylight area to control the connection status between the boreholes in the skylight area and the non-skylight area.

[0016] S7. Set up water level monitoring points for aquifers in wind-blown sand areas and non-skylight areas;

[0017] S8. During the rainy season, open the valve to allow the non-skylight area to replenish the skylight area until the water level of the aquifer in the non-skylight area monitored by the monitoring point in step S7 is lower than the water level of the aquifer in the skylight area. At this time, close the valve.

[0018] S9. During the non-rainy season, water is extracted from the aquifer supplied by the wind-blown sand in the skylight area and used for production, ecological and domestic water use in the mining area.

[0019] Furthermore, in step S1, the skylight area refers to the pinch-out area of ​​the directly impermeable soil layer beneath the loose sand layer, or the area less than 10 meters deep.

[0020] Furthermore, in step S3, the direction of groundwater recharge at the spring point is determined by a borehole flow velocity and direction instrument.

[0021] Furthermore, in step S4, the water-conducting fracture zone generated by the coal mining height H should extend to a range of 3 to 5 times H below the bottom plate of the weathered bedrock aquifer.

[0022] Furthermore, in step S5, the relationship between the coal mining height and the water-conducting fracture zone height is determined through a predetermined numerical simulation experiment.

[0023] Furthermore, in step S5, the periodic pressure step distance is determined through conventional numerical simulation experiments.

[0024] Furthermore, in step S5, the location 3-5 meters upstream of the spring point serves as the location for reserving coal pillars between different coal mining faces.

[0025] Furthermore, in step S6, permeable perforated pipes are installed in sections of the directional borehole located in the aquifer of the sandy beach, and water-stopping sleeves are installed in the remaining sections.

[0026] The beneficial effects of this invention are:

[0027] 1. This invention considers that the aeolian sandy aquifer has a relatively balanced capacity for receiving atmospheric precipitation and for storing water. Unlike loess, which has difficulty in infiltration, and fissure aquifers, which have insufficient water storage capacity, it is a good sponge-like water storage layer. The skylight area serves as a good channel for the aeolian sandy aquifer to replenish other aquifers. By increasing the replenishment level (through directional drilling, which is equivalent to improving the rapid cross-regional replenishment of water resources), the water storage capacity of the entire mining area is significantly increased. To prevent a large amount of water resources from being discharged through surface springs, coal pillars are left to change the original seepage path of the aeolian sandy aquifer (the settlement of the coal pillar area is smaller than that of the mining area), blocking or reducing the discharge of spring water, increasing the migration path of groundwater, and thus increasing the infiltration rate.

[0028] 2. This invention's infiltration control in skylight areas is based on two principles. Firstly, to prevent large-scale water inflow into the mine through skylight areas, thereby reducing groundwater pollution and the cost of raising water to the surface, the height of the water-conducting fracture zone needs to be controlled. Secondly, skylight areas need to settle sufficiently to allow more water resources to enter the underlying aquifer of the sandy sand aquifer during the rainy season. Therefore, based on the theory of mine pressure and strata control (enhancing the critical strata fracture rotation space), roof cutting is employed to allow for more complete mine settlement.

[0029] 3. This invention utilizes the naturally occurring skylights in sandy areas to guide water, making it simple and easy to implement; it increases the amount of water resources that infiltrate from sandy areas and are converted into other aquifers, effectively alleviating water shortage problems; it prevents large amounts of water from entering mined-out areas, thus improving water quality; it effectively controls the problem of excessive water accumulation in sandy areas, reducing safety risks in coal mining.

[0030] Of course, any product implementing this invention does not necessarily need to achieve all of the above advantages at the same time. Detailed Implementation

[0031] The technical solutions will now be clearly and completely described in conjunction with embodiments of the present invention. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] This invention provides a method for water storage in wind-blown sandy mining areas, comprising the following steps:

[0033] S1. Use geophysical exploration techniques to delineate the window zones of the loose sand aquifer and the weathered bedrock aquifer; the window zone refers to the pinch-out zone of the directly impermeable soil layer beneath the loose sand layer, or the zone less than 10 meters deep.

[0034] S2. Conduct a hydrogeological survey of the sandy beach area in the skylight area to determine the spatial location of the sandy beach springs.

[0035] S3. Determine the direction of groundwater recharge for the springs identified in step S2. This can be determined by measuring the borehole flow velocity and direction using an instrument.

[0036] S4. Determine the coal mining height in the skylight area. The water-conducting fracture zone generated by the coal mining height H should extend to a range of 3 to 5 times H below the bottom plate of the weathered bedrock aquifer. The relationship between the coal mining height and the height of the water-conducting fracture zone is determined through predetermined numerical simulation experiments.

[0037] S5. For coal seams in the skylight area, the mining face is located at the boundary of the skylight area. Hydraulic fracturing technology is used for manual roof cutting. Within the skylight area, the roof is manually cut at intervals of 0.5 to 0.8 times the per-cycle pressure step distance. The per-cycle pressure step distance is determined through conventional numerical simulation experiments. The location 3 to 5 meters upstream of the spring point is used as the coal pillar placement point between different mining faces.

[0038] S6. Directional drilling is carried out underground in the coal mine. The horizontal section of the directional borehole passes through the bottom of the aquifer in the skylight area and connects with the aquifer in the non-skylight area. Permeable pipes are installed in the sections of the directional borehole located in the aquifer, and water-stopping sleeves are installed in the remaining sections. Valves are installed in the directional borehole located in the skylight area to control the connection between the boreholes in the skylight area and the non-skylight area.

[0039] S7. Set up water level monitoring points for aquifers in wind-blown sand areas and non-skylight areas.

[0040] S8. During the rainy season, open the valve to allow the non-skylight area to replenish the skylight area until the water level of the aquifer in the non-skylight area monitored by the monitoring point in step S7 is lower than the water level of the aquifer in the skylight area. At this time, close the valve.

[0041] S9. During the non-rainy season, water is extracted from the aquifer supplied by the wind-blown sand in the skylight area and used for production, ecological and domestic water use in the mining area.

[0042] The specific embodiments of the present invention are as follows:

[0043] Example 1

[0044] This embodiment takes the Mu Us Desert as the research object. A large area of ​​the Mu Us Desert surface is characterized by sandy sand dunes, beneath which lie abundant coal resources. However, the region is relatively water-scarce, and many coal mines have resorted to extensive surface water extraction due to water shortages, leading to increased water resource burdens during the dry season. To alleviate the conflict between coal mining and water resource protection, a coal mine in this region adopted a water storage method for sandy sand dune mining areas. The specific steps are as follows:

[0045] Step 1: Using geophysical exploration techniques (seismic exploration techniques), delineate the window zones of the loose sand aquifer and the weathered bedrock aquifer. The window zone refers to the pinch-out area or area less than 10 meters deep beneath the directly impermeable soil layer of the loose sand layer. A total of 1.8 km was delineated. 2 The skylight area.

[0046] Step Two: Conduct a hydrogeological survey of the sandy beach area in the Tianchuang area to determine the spatial location of the sandy beach springs. A total of 42 springs were identified.

[0047] Step 3: Determine the direction of groundwater recharge for the springs identified in Step 2 by measuring the flow velocity and direction through borehole flow instruments.

[0048] Step 4: Determine the coal mining height n = 2.8 meters in the skylight area. The water-conducting fracture zone generated by the coal mining height n should extend to a range of 4 times 2.8 meters (11.2 meters) below the bottom of the weathered bedrock aquifer. The relationship between the coal mining height and the height of the water-conducting fracture zone is determined through a predetermined numerical simulation experiment.

[0049] Step 5: Mining the coal seam in the skylight area. At the boundary of the skylight area, hydraulic fracturing technology is used for manual roof cutting. Within the skylight area, manual roof cutting is performed at intervals of 0.5 times the fracturing step distance (9 meters) of the mining cycle. The fracturing step distance for the cycle is determined to be 18 meters through conventional numerical simulation experiments. In addition, a coal pillar is reserved 3 meters upstream of the spring point as a location between different mining faces.

[0050] Step Six: Conduct directional drilling underground in the coal mine, with the horizontal section traversing the bottom of the aquifer in the skylight area and connecting with the aquifer in the non-skylight area. A permeable perforated pipe is installed in the aquifer section of the directional borehole, while water-stopping sleeves are installed in other areas. Additionally, valves are installed in the skylight area to control the connection between the boreholes in the skylight and non-skylight areas.

[0051] Step 7: Set up aquifer water level monitoring system in both skylight and non-skylight areas.

[0052] Step 8: During the rainy season, open the directional drilling valve to allow the non-skylight area to supply water to the skylight area until the water level of the aquifer in the non-skylight area monitored in Step 7 is lower than that in the aquifer in the skylight area, then close the valve.

[0053] Step Nine: During the non-rainy season, water is extracted from the aquifers replenished by the wind and sand in the skylight area for use in mining production, ecology, and daily life.

[0054] Monitoring revealed that the increased water supply to the underlying weathered bedrock aquifer during the rainy season caused the water level to rise by 33% compared to previous years, resulting in a significant increase in usable water resources and ensuring the water supply for the mining area.

[0055] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for water storage in wind-blown sandy mining areas, characterized in that, Includes the following steps: S1. Use geophysical exploration techniques to delineate the window areas of the loose sand aquifer and the weathered bedrock aquifer. The window area refers to the pinch-out area of ​​the directly impermeable soil layer under the loose sand layer, or the area less than 10 meters deep. S2. Conduct a hydrogeological survey of the sandy beach area in the skylight area to determine the spatial location of the sandy beach springs. S3. Determine the groundwater recharge direction of the spring points identified in step S2; S4. Determine the coal mining height in the skylight area. The water-conducting fracture zone generated by the coal mining height H should reach a range of 3 to 5 times H below the bottom plate of the weathered bedrock aquifer. The relationship between the coal mining height and the height of the water-conducting fracture zone is determined through a predetermined numerical simulation experiment. S5. When mining coal seams in the skylight area, the coal mining face is set at the boundary of the skylight area. Hydraulic fracturing technology is used for manual roof cutting. Within the skylight area, the roof is manually cut at intervals of 0.5 to 0.8 times the step distance of the coal mining cycle. S6. Directional drilling is carried out underground in the coal mine. The horizontal section of the directional borehole passes through the bottom of the sandy aquifer in the skylight area and connects with the sandy aquifer in the non-skylight area. A valve is installed in the directional borehole located in the skylight area to control the connection status between the boreholes in the skylight area and the non-skylight area. S7. Set up water level monitoring points for aquifers in wind-blown sand areas and non-skylight areas; S8. During the rainy season, open the valve to allow the non-skylight area to replenish the skylight area until the water level of the aquifer in the non-skylight area monitored by the monitoring point in step S7 is lower than the water level of the aquifer in the skylight area. At this time, close the valve. S9. During the non-rainy season, water is extracted from the aquifer supplied by the wind-blown sand in the skylight area and used for production, ecological and domestic water use in the mining area.

2. The water storage method for wind-blown sandy mining areas according to claim 1, characterized in that: In step S3, the direction of groundwater recharge at the spring point is determined by a borehole flow velocity and direction instrument.

3. The water storage method for wind-blown sandy mining areas according to claim 1, characterized in that: In step S5, the periodic pressure step distance is determined through conventional numerical simulation experiments.

4. The water storage method for wind-blown sandy mining areas according to claim 1, characterized in that: In step S5, the location 3-5 meters upstream of the spring point is used as the coal pillar placement point between different coal mining faces.

5. The water storage method for wind-blown sandy mining areas according to claim 1, characterized in that: In step S6, permeable perforated pipes are installed in sections of the directional borehole located in the aquifer of the sandy beach, and water-stopping sleeves are installed in the remaining sections.