A Novel Approach to Model Earth Fissure Caused by Extensive Aquifer Exploitation and its Application to the Wuxi Case, China

Abstract

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.

3D groundwater flow and deformation modelling of Madrid aquifer

“…Equation (4) holds when the soil deformation is mainly vertical. This condition always holds for aquifers and reservoirs experiencing pore pressure change except where faults/fractures/geologic discontinuities can be responsible for significant horizontal strain (e.g., Ye et al, 2018). Therefore, it is fully warranted for the TDAM aquifer.…”

A Parametric Numerical Analysis of Factors Controlling Ground Ruptures Caused by Groundwater Pumping

“…Ground rupture, with fracture opening (Earth fissure; Figure a) or small to large vertical offset (faulting; Figure b), is a geomechanical process that may be associated with groundwater pumping from unconsolidated sedimentary aquifer systems. Apart from a few occurrences, for example those in Suzhou‐Wuxi‐Changzhou area, Yangtze River delta, China (Ye et al, ; Zhang et al, ), ground ruptures associated with groundwater pumping generally develop in arid or semiarid basins. The largest densities of ground ruptures are located in Arizona, USA (Conway, ; Jachens & Holzer, ), central Mexico (Carreón‐Freyre, ; Carreón‐Freyre et al, ; Teatini et al, ), northern China (Li et al, ; Peng et al, ), and Iran (Ziaie et al, ), where the average annual precipitation is 200, 500, 550, and 300 mm, respectively.…”

Analogue model of ground ruptures due to groundwater pumping in an aquifer above a bedrock ridge

“…b. Wuxi in Jiangsu province, China (Ye et al, 2016(Ye et al, , 2018, where ground fractures have a banded distribution whose orientation is aligned with the bedrock ridges buried by the Yangtze alluvial deposits. In this case a band of fractures developed with normal fault geometry predominantly dipping northwest.…”

“…In this case a band of fractures developed with normal fault geometry predominantly dipping northwest. The geometry of this fracture is probably controlled by the asymmetric thickness of the compressible sediments between the two sides of the ridge (larger at the western side; Ye et al, 2018).…”