1. Strengthen hydrogeological exploration
The compass of the entire coal mine during the hydrogeological exploration before the well was built, but due to the arbitrary change of the drilling depth or the reduction of the number of boreholes in some coal mines, there are certain limitations in the field data collection and data processing, which ultimately leads to the detailed hydrogeological data of these coal mines. The degree and reliability are low, especially in some geological data, the impact of relevant surface water and karst water on mining is not fully evaluated, even the hydrogeological boundary is unclear, and the mine water inflow prediction has large errors and other factors will give mine safety. Production brings great hidden dangers. Therefore, strengthening the hydrogeological exploration before the construction of the well is a must for the safety of the coal mine, especially for mines with complex geological structures.
2. Ground prevention methods and measures
There are three main types of ground prevention and control measures for mine water disasters: trench drainage, blocked passages, and river remediation.
Trenching and flood discharge is mainly for mines located in the plains of the foothills and piedmont plains. In the rainy season, floods are often encountered in flooded wellheads and industrial squares, or along coal seams, aquifer outcrops and fissures, which increase the amount of water in the mine. Generally, drainage ditch should be built in the direction of vertical water above the mining area to intercept mountain torrents and shallow groundwater. The drainage ditch is arranged along the topographic contours and maintains the proper slope to drain the water out of the affected area.
The blocked passage is for the ground collapse pits, cracks, caves, etc. in the mining area, which may become the channel for filling the mine. It is filled with clay and cement. For larger collapse pits and cracks, the lower part is filled with gravel, and the upper part is covered with clay and compacted. Above the ground, it penetrates with a waterproof flow.
River remediation, when there are rivers in the mining area, and threaten the production of the mine, take measures such as river diversion or paving the river bottom to prevent or reduce the infiltration of river water, thus affecting the amount of water in the mine.
3. Downhole prevention methods and measures
Coal mine underground water damage prevention measures are mainly combined with geological exploration data and underground inspection work, using drilling water before mining, waterproof gates, waterproof walls or grouting to block water sources, drainage and dewatering and other methods.
When the underground tunneling is close to the cave, the water-bearing fault, and the water-rich aquifer, close to the fault that may be connected with the rivers and lakes, the water-rich aquifer, and the large amount of accumulated water, close to the flooded roadway or the waterlogged goaf. When the situation is equal, the water must be explored in advance to respond to the water damage.
Measures such as building waterproof gates, waterproof walls, and grouting are generally used to block water sources. In mines with complex hydrogeology or water inrush, water gates must be installed at both ends of the wellsite. Waterproof walls are generally used to block water-filled working faces or mining sites, old empty areas, and roadways that communicate with surface water bodies. The grouting is used to block the water, and the cement slurry is injected into the rock fissure hole to block the water source. The key to determining the success or failure of grouting is to determine the location of water blocking, select the grouting material, and determine the construction method.
Drainage and dewatering methods include surface drilling and drainage, downhole drilling and dewatering, and use of roadway to drain. According to the groundwater level, water quantity and recharge conditions, the dewatering interval and sequence are determined, the drainage flow is controlled, the roadway is reinforced before drainage, and the water pressure and permeable experiment are carried out before the formal drainage. The problem should be dealt with in time.
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