Numerical Simulation On Land Subsidence Of Shanghai

Land subsidence of Shanghai was first detected in 1921. Since 1980s, with the rapid development of social economy, especially the intensive construction, the disasters brought from land subsidence in Shanghai have been becoming more and more serious.Based on an intensive review of current research achviements on the studies on land subsidence in the world, especially the shortcomings of numerical models for land subsidence, a water-soil fully coupled FEM model was developed after analysis of the long-term monitoring data of Shanghai land subsidence, and numerical simulations were perfomed in this paper.Comparions between numerical results and observing data show that, the FEM programme developed in this papar could effectively simulate the land subsidenc in the simulation areas with a good agreement between the numerical results and the observing data. Meanwhile, conclusions were deduced that the 1st soft clay layer, the 4th hard clay layer and the 4th aquifer are the major layers of the subsidence in the simulation areas. Pumping of the groundwater and intensive construction in this area are the two main reasons to landsubsidence.Some innovations were achieved in this paper. Firstly, based on a profound overview of all the numerical models used for simulations of Tianjin and Shanghai land subsidence, a water-soil fully coupled FEM model was developed in this paper which can overcome the shortcomings of the quasi-three dimensional flow model as well as two-step coupling method. Secondly, based on investigations on the deformation characteristic of the 1st soft clay layer, the 4th hard clay layer and the 4th aquifer, the suggestion of an elastoplastic constitutive model should be employed instead of a plastic model for the simulation of the deformaion was made in this paper, finally, a sub-loading t_ij constitutive model was choosed for the first time for land subsidence simulation because of its advantages in describing the three-dimension stress-strain behaviors of soil and being also adapt to overconsolidated soil. In one word, all the efforts made in this paper greatly improved the veracity of the constitutive model, which can simulate three-dimensional behaviors of soil.