A novel approach to model earth fissure caused by extensive aquifer exploitation
and its application to the Wuxi case, China
S. Ye
School of Earth Sciences and Engineering, Nanjing University, Nanjing, China
Y. Zhang, X. Gong, J. Yu
Key Laboratory of Earth Fissures Geological Disaster,
Ministry of Land and Resources, Geological Survey of Jiangsu Province, Nanjing, China
A. Franceschini, C. Janna, P. Teatini
Dept. of Civil, Environmental and Architectural Engineering,
University of Padova, Padova, Italy
Initially observed in the semiarid basins of southwestern USA, earth fissures due to aquifer
over-exploitation are presently threatening a large number of subsiding basins in various countries
worldwide. Different mechanics have been proposed to explain this process, such as differential
compaction, horizontal movements, and fault reactivation. Numerical modeling and prediction of this major
geohazard caused by overuse of groundwater resources are challenging because of two main requirements:
shifting from the classical continuous to discontinuous geomechanics and incorporating two-dimensional
features (the earth fissures) into large three-dimensional (3-D) modeling domain (the subsiding basin). In
this work, we proposed a novel modeling approach to simulate earth fissure generation and propagation in
3-D complex geological settings. A nested two-scale approach associated with an original nonlinear
elastoplastic finite element/interface element simulator allows modeling the mechanics of earth
discontinuities, in terms of both sliding and opening. The model is applied on a case study in Wuxi, China,
where groundwater pumping between 1985 and 2004 has caused land subsidence larger than 2 m. The
model outcomes highlight that the presence of a shallow (~80 m deep) bedrock ridge crossing the Yangtze
River delta is the key factor triggering the earth fissure development in this area. Bending of the alluvial
deposits around the ridge tip and shear stress due to the uneven piezometric change and asymmetrical
shape of the bedrock have caused the earth fissure to onset at the land surface and propagate downward
to a maximum depth of about 20-30 m. Maximum sliding and opening are computed in the range of
10-40 cm, in agreement with the order of magnitude estimated in the field.
