GPS BASED STUDY ON REGULARITY AND MECHANISM OF LAND SUBSIDENCE IN JIANGYIN CITY AREA

Based on the data of GPS monitoring and the existing results of leveling, the evolutionary characteristics and regularity of the land subsidence in Jiangyin city were studied systematically and thoroughly. The reasons for the land subsidence were analyzed by integrating the observation data of groundwater activity and slice indicators of land subsidence. It was indicated that land subsidence took place mostly in the south of Jiangyin city, and the subsidence value decreased gradually from the south to the north and east. Land subsidence correlated with the exploitation of groundwater closely in Jiangyin city. It was retardant and irreversible. Land subsidence was controlled mainly by two factors in Jiangyin city. The geological environment with subsidence characteristics was the necessary intrinsic factor, including the discrepancies in the forms of bedrock. The aggradation structure of Quaternary period and hydro-geological conditions, and the super-pumping groundwater is the extrinsic factor. The land subsidence was caused by compression of aquiferous sand strata and concretion of clay soil of roof and bottom plate.