EVOLUTION MECHANISM OF KARST SINKHOLES IN WUHAN CITY

This paper is based on the analysis of 29 karst sinkholes in Wuhan. Their system structure is determined from three elements, i.e.karst, cover and groundwater. The sinkhole mechanism of rainfall, drilling and pile constructing importing karst system is discussed via field monitoring and numerical simulating. The results are as follows. (1) The geological conditions developing sinkhole include the following three aspects. The cover structure is upper clay and lower sand. The shallow karst is developed. The hydraulic connection between pore water-karst water is good. (2) In natural environment, the cave in cover soil has two developing stage that is from hydraulic corrosion to stress failure. (3) Drilling and pile constructing often trigger sinkhole that is from two aspects of structure changing. The covering soil has high hydraulic gradient at the moment of drill connecting pore water and karst water. The head difference of two groundwater is more than 15m during pile constructing.