Relationship between Jurassic ancient channel sand body and coal mining water inrush in the north of Yulin area

In the Yushen-Shenfu mining area with seemingly simple hydrogeological conditions，some coal mining water inrush accidents occur from time to time. The water inrush of some coal mines ranks first in the Ordos Basin. It is difficult to explain these phenomena by the water filled aquifer generally considered in the past. Based on the research on the uranium reservoir（paleochannel sandstone）at the bottom of the Zhiluo formation in the past 20 years，combined with the spatial configuration relationship between the paleochannel sand body of the Zhiluo formation and the minable coal seam of the Yan’an formation，as well as the basic conditions for the formation and development of sandstonetype uranium deposits，especially the correlation analysis among the concealed outcrop of paleochannel of the Zhiluo Formation and surface spring groups（belts）and coal mining water inrush，it is considered that the paleochannel of the Zhiluo formation may be the main water source of mine water inrush in the YushenShenfu mining area. The main conclusions are as follows:① the paleochannel sand body of the Zhiluo formation has a regional distribution scale. The worldclass Dongsheng uranium ore field formed in its upstream proves that the paleochannel of the Zhiluo formation is a set of regional aquifer，because the aquifer is a necessary condition for the formation，development and future exploitation of sandstonetype uranium deposit.② Above the concealed outcrop of the paleochannel of the Zhiluo formation，spring groups and spring belts with extraordinary water yield are intensively developed. The closer they are to the paleochannel of the Zhiluo formation，the greater their water yield，indicating that the paleochannel of the Zhiluo formation is an important aquifer，which provides the main water source for the spring belt of the Yushen Shenfu mining area.③ The paleochannel aquifer of the Zhiluo formation constitutes the direct roof of coal measures of the Yan’an formation. Coal mining proves that the paleochannel aquifer of the Zhiluo formation has an obvious hydraulic connection with coal mine water inrush. The coal mine located near the latent outcrop of the paleochannel is prone to water inrush accidents，while the water inrush of the coal mine away from the ancient river channel is rare，and the water inrush of coal mining is positively correlated with the sandstone thickness of the paleochannel.④ From the perspective of spatial configuration and coupling relationship of key hydrogeological parameters and coal mining time domain，the genetic mechanism model of the water inrush of coal mining in the Yushen Shenfu mining area is constructed. The model expounds the formation，development and evolution mechanism of spring belt，reveals the formation mechanism of the water inrush of coal mining，and provides basic geological“early warning” information for future water disaster prevention，water conservation coal mining，coal uranium concurrent mining，etc.