The control of the old (abandoned course of) Yellow River fault zone in Xuzhou on the karst collapse

The urban area of Xuzhou has had serious karst collapse geological hazards which are widely distributed in the old Yellow River fault zone. There exists obvious regularity that the karst collapses are caused by excessive groundwater exploitation, and the fault zone is enriched with groundwater. The research shows that the karst is developed well in the old Yellow River fault zone and there are upward opening karst caves and fissure. The fault zone has linked up aquifers of different ages and thus has formed fierce runoff belt or enrichment belt of groundwater. The graben fault zone constituted negative landforms which formed the late Pleistocene and Holocene paleochannels. The paleochannels become "permeable-only covering layer" and "permeable-aquiclude covering layer" which made the sandy soil of the Yellow River flood sediments directly cover the karst aquifers. Then they provided important hydrodynamic conditions for the karst collapse which was caused by excessive groundwater exploitation. Therefore the extensional-shear fault zone and the accompanying fractures have controlled the formation conditions of karst collapses, especially karst development, karst hydrogeological structure and enrichment regularity of groundwater.