Water Disasters And Impact On Phreatic Water Table By Full-mechanized Top-coal Caving In Desert Bottomland

Jurassic coal field in Northern Shaanxi is one of the largest proven coalfield in China. Its abundant reserve, perfect coal quality, simple geological and mining conditions make it a key area of our country’s coal industry strategic shift westwards. However, the area is located in the border region of Maowusu desert and the loess plateau, water resource is scarce and the ecological environment is fragile, Quaternary Salawusu group unconfined aquifer is the important water source to maintain the supergene ecological environment, residents, industrial and agricultural development. Over the years, coal mining damaged the stability of aquiclude overlying coal seam, caused groundwater leakage and mine water inrush and increased ecological environment deterioration. Therefore, water disasters in the process of coal mining and the impact on the ecological environment must be taken into account.The paper takes Jinjitan coal mine, which is located in south-eastern periphery of Maowusu desert, as the study area. The hydrogeological characteristics were analyzed, overlying strata structure and engineering geological petrofabric were classified. Analyzed measured data of height of water flowing fractured zone under regional Jurassic coal seam mining, found that there were greater differences with the calculation of the empirical formula in current specification, and a non-linear formula which can be apply to predicting the height of water flowing fractured zone in the study area was established. Consider engineering geological parameters dynamic variation of coal seam roof under the large-scale mining. The dynamic process of roof deformation and destruction of fully mechanized top-coal caving the Jurassic coal seam was simulated and analyzed using RFPA software. The deformation and destruction characteristics of fracture developing in weathered zone and soil was analyzed. The results show that inhibition of weathered zone is not obvious, soil can restrain the development of fracture, the plastic characteristic and the original crack can dissipate energy, inhibited the development of fracture; water flowing fractured zone can be effectively controlled under the soil, then estimated the height of water flowing fractured zone of full-mechanized caving mining face. On this basis, water inflow of coal face was estimated, calculated the groundwater level decline after mining, and evaluated the influence of mining on the supergene eco-environment. Some suggestions on prevention and control of water disasters were put forward. Research results of mine has general guiding significance for coal mines in the northwestern desert to prevent and control water disasters, it benefits ecological environment protection.