Regional land subsidence model embodying complex deformation

Large regions of land subsidence usually present very complicated historical deformation characteristics of sedimentary layers. A regional land subsidence model based on the modified Merchant model is developed and proposed to describe the visco-elastic-plastic deformation. Regional land subsidence models describing elastic, visco-elastic and elastic-plastic deformations can be derived from the one based on the modified Merchant model by setting proper values of the parameters involved. A new numerical method, the multi-scale finite-element method, is used to model regional land subsidence problems. Land subsidence in Shanghai from 1986 to 1998 is simulated as a case study for the model proposed in this paper. The results show that the model is capable of describing land subsidence with complex deformation characteristics, and can represent the mechanism of land subsidence caused by excessive groundwater withdrawal relatively well. The method is shown to be a good numerical method that significantly reduces computing effort and obtains accurate results.