Aquifer Variation Characteristics of Coal Overlying Strata by Time-lapse Resistivity Monitoring
Du, Wenfeng; Peng, Suping
China University of Mining and Technology(Beijing), China, People's Republic of
The coal mining areas of Western China are facing serious shortage of water resources and fragile ecological environment, high-intensity coal mining results in ground subsidence and overburden destruction, the structure of underground aquifer is destroyed and the groundwater level is lowered. The time-lapse electric prospecting method is applied to dynamically monitor the underground aquifers in different periods of modern coal mining, in order to research the influence of coal mining on overlying aquifer and groundwater. Time-lapse resistivity monitoring carries out multiple 2D electric prospecting for the same stratum at certain time intervals. Time-lapse resistivity monitoring involves many aspects such as data acquisition, processing, interpretation and inversion. The research district is located in Shendong mining district in Western China's Shaanxi Province. 4 times time-lapse resistivity data acquisition is determined, the time node respectively is pre-mining, mining and post-mining as well as post-mining deposition stable period, the duration of this time-lapse data acquisition is 10 months. It can be found through comparing resistivity slices of shallow aquifer during coal mining that before mining, due to a small brook exists in the middle of shallow aquifer, its underlying strata are water saturated and water bearing of other zones is poor, mining activities lead to electric property changes of subsurface aquifers during mining, the resistivity increases a little bit and water bearing deteriorates in general, , resistivity of subsurface aquifer decreases during post-mining deposition stable period and its water-bearing distribution basically recovers to the pre-mining state. when influenced by mining, roof water infiltrates downward and roof resistivity increases. The research result shows that the aquifer variation of overlying strata have self-recovery capability with the development of modern coal mining process，the self-recovery capability gradually strengthens from coal seam roof upward to the near surface，the self-recovery capability of near-surface strata is relatively strong , while the roof of coal seam is most weak.