Regularity and formation mechanism of large-scale abrupt karst collapse in southern China in the first half of 2010

From winter 2009 to spring 2010, southern China suffered from an extensive and lengthy drought. Subsequently, southern China experienced torrential rains a dozen times during the flood season of April-June. The prolonged drought and subsequent intensive rainfall dramatically altered the hydrodynamic conditions of the karst areas, causing hundreds of widely distributed karst collapses, with extensive damage to houses and fields and necessitating the evacuation of many people. Understanding the causes of these collapses will provide a scientific basis for the prediction or prevention of the related risk. Thus, a geologic survey of karst collapses was performed that systematically allowed to analyze the basic geological conditions, groundwater hydrodynamic conditions, overlying strata properties, and environmental and climatic conditions in southern China. The results showed that environmental and climatic changes, especially the drastic changes in rainfall, gave rise to striking changes in karst hydrodynamic conditions that accelerated infiltration, suffosion, dissolution, and transportation rates and also changed the physical and mechanical properties of the strata overlying karst caves. These stressors triggered or facilitated both cave formation and collapse.