Modeling of land subsidence due to groundwater overexploitation using elastoplastic Mohr-Coulomb model in Arak plain, Iran

Land subsidence due to groundwater overexploitation has been considered among the natural hazards for the last decades. Accordingly, a growing global concern has been forwarded towards this issue regarding its measurement, prediction, and prevention. In addition to measurement techniques, mathematical and numerical methods could be used for subsidence modelling and its prediction via appropriate software tools and modelling frameworks. As a part of the global trend, groundwater overexploitation and the subsequent land subsidence has lately become a major environmental threat in Iran. In this paper, the land subsidence across Arak plain, a relatively vast plain located in central Iran, caused by groundwater level drop is calculated using Mohr-Coulomb elastoplastic model, which is a structural soil modelling framework. Also, a modified finite element method is applied via PLAXIS 2D commercial software for acquiring further insight and verifying the results from the Mohr-Coulomb model. Accordingly, five borehole stations were considered across the Arak plain, namely Gavkhaneh, Ebrahimabad, Safarabad, Amanabad, and MojedabadKohneh and the mentioned model is applied at each borehole. It was revealed that the axial strain across the plain has reached extreme negative value of -0.190 in 2014, which shows severe soil compaction. Also, the volumetric strain rate reached a minimum value of -0.083 in 2014. The acquired results from the applied Mohr-Coulomb model showed a subsidence average value of 26.6 cm for 17.85 m of groundwater level drop during 1991-2014. Also, the lowest aggregated subsidence value until 2014 was observed at Safarabad station being 0.2 cm, while its maximum value was observed at Gavkhaneh station being 88.75 cm. These was a 9.20% of difference between the average value acquired by Mohr-Coulomb model and FEM, which, considering the uncertainty in measured input data verifies the reliability of the model. The research findings prove the capability of the Mohr-Coulomb model in modelling land subsidence.