Three dimensional numerical modeling of land subsidence in Shanghai
S. Ye, Y. Luo, J. Wu
School of Earth Sciences and Engineering, Nanjing University, Nanjing, China
P. Teatini
Dept. of Civil, Environmental and Architectural Engineering,
University of Padova, Padova, Italy
H. Wang, X. Jiao
Key Laboratory of Land Subsidence Monitoring and Prevention,
Ministry of Land and Resources, Shanghai Institute of Geological
Survey, Shangha, China
Shanghai city has been suffering land subsidence caused by overly exploitation of ground water since
1921, which is a serious problem for this coastal city with altitude of 2.2-4.8 m above mean sea level. The largest
cumulative land subsidence amounted to 2.6 m in the downtown area. Measures to decrease the ground water
exploitation, change the pumping aquifers, and increase aquifer artificial recharge have been used to mitigate
land subsidence since 1961. It is necessary to develop a proper numerical model to simulate and predict land
subsidence. In this study, a decoupled three-dimensional (3-D) finite element land subsidence model including a
3-D ground water flow model and a 3-D geo-mechanical model was developed to simulate the 3-D deformation
of the aquifer systems in the center area of Shanghai. The area of downtown Shanghai is 660 km2, with 10
million inhabitants, dense high buildings, and 11 metro lines. The simulation spans the period from 1979 to
1995. Two different assumptions have been tested on the side boundary, i.e., precluding the three components
of the displacement, or assuming a free-displacement condition. The distribution of calculated land subsidence
and horizontal displacements in different aquifers was analyzed. The computed vertical displacement fitted well
with the available observations. It has been verified that the two different assumptions on the lateral boundaries
in the geo-mechanical model caused different results just limited on nodes close to boundary. The developed 3-D
land subsidence model is reasonable and can be used to simulate and predict 3-D movement of aquifer systems
in the center area of Shanghai, which could provide scientific support to local government in controlling land
subsidence and differential movements of the land surface.
