Investigation of effective factors in the phenomenon of land subsidence in the western area of Tehran province

The phenomenon of subsidence is one of the geological hazards, which is mostly created and aggravated by human and natural activities such as long-term extraction of underground sources of water, oil and gas or the extraction of minerals from mines and the dissolution of subsurface formations and the collapse of karst. turns Shahryar plain is one of the forbidden and critical plains of the country, which is also active in terms of industry and agriculture, this plain has been affected by land subsidence for the past several years. In this research, in order to analyze, investigate and predict the subsidence rate, the poroelasticity flow module was used in COMSOL software, which can determine the changes in the thickness of the soil sedimentary layer due to groundwater loss and also in the coming years. He nosed.

In this research, by coupling Darcy's law and changing the soil skeleton by COMSOL software, it was tried to calculate the subsidence in 22 selected points of the study area during the years 2003-2019 and after verifying and obtaining a high agreement with real data and images. Radar interferometry estimated the amount of subsidence until 2031.

The general result of finite element numerical modeling showed that the subsidence rate of the area during the year 2031 was estimated at 12.8 cm and at critical points 20.98 cm. Therefore, the maximum settlement caused by the drop in the underground water level in the early years appeared at a higher rate in the upper layer of the aquifer, which over time after filling the voids between the soil particles and due to the hydraulic connection between the layers It is observed at a slower rate than in the past in the upper layers of the aquifer surface and the ground surface. Therefore, changes in the groundwater level, soil type and distance from the fault have also been among the factors affecting the subsidence pattern and rate.