Mechanisms for earth fissure formation due to groundwater extraction in the Su-Xi-Chang area, China

Excessive groundwater withdrawal has caused many earth fissures in the cities of Suzhou, Wuxi, and Changzhou (i.e., the Su-Xi-Chang area or “SXC area”) in Jiangsu Province, China. The appearance of these fissures is closely associated with groundwater withdrawal both temporally and spatially. Based on field investigations, three models of the earth fissures in the SXC area were conceptualized. The changes in and distributions of normal and shear stress in hydrostratigraphic units due to groundwater extraction were analyzed numerically for each conceptualized model. Results from these numerical simulations indicated that geological conditions play a crucial role in the occurrence and distribution of earth fissures. Earth fissures are much more likely to initiate in areas where the depth of the bedrock below the ground surface is small, the thickness of the exploited aquifer unit changes abruptly, and the surface of the bedrock undulates dramatically. Earth fissures are also likely to occur in the vicinity of a distant restricted boundary. In addition, very stiff topsoil is more prone to cracking, and the locations of discharge wells also influence the occurrence of earth fissures.