Aseismic multi-fissure modelling in unfaulted heavily pumped basins: Mechanisms and applications
Y. Li, S. Ye
School of Earth Sciences and Engineering, Nanjing University, Nanjing, China
P. Teatini, A. Franceschini, M. Frigo, C. Zoccarato
Dept. of Civil, Environmental and Architectural Engineering,
University of Padova, Padova, Italy
J. Yu
Key Laboratory of Earth Fissures Geological
Disaster, Geological Survey of Jiangsu Province, Nanjing, China
Aseismic earth fissures are among the most dangerous by-products of excessive
groundwater exploitation in many subsiding sedimentary basins. Improving our understanding of
the mechanisms of earth fissuring is important for land planning and risk management. We employ
an advanced finite-element interface-element modeling approach to understand the generation and
propagation of multiple fissures in unfaulted basins. Almost parallel earth fissures at a relative short
distance (on the order of tens of meters) generally develop above impermeable and/or incompressible
ridges buried by the compacting sedimentary units. Initially, we investigate the effect of the ridge slope
on a simplified geological setting sketched from the Luke salt dome, Arizona. Then, we apply the model
to the hydrogeologic setting at Guangming village, Wuxi, China. In both analyses, the model simulates
the formation of multifissures above the ridge, as observed at the sites. The earth fissures initiate at
land surface and propagate downward. They are caused by the combination of tensile stress (bending
condition) and shear stress (shearing conditions) accumulation around and above the tip and the slopes
of the ridge, respectively. The steeper the ridge, the more concentrated stress zone develops above the
ridge tip, favoring the formation of fissures with significant opening and small or null offset. The opposite
facilitates a widening of the stress accumulation area, with less-deep fissures characterized by larger
sliding and smaller opening. At Guangming, the model suggests that fissures propagate down to 20-50-m
depth, with maximum opening and sliding of about 50 cm.
