عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Land subsidence is one of natural hazards which is involved with most of plains in Iran and leads to damages of urban area, roads, bridges, power transmission lines, agriculture lands, wells and piezometers. Generally, regional subsidence is depended to human activities such as extractionof groundwater and geological conditions which can induce considerable damages to economical basis of the area if it be occurred. In the last few decades, the rapid development of agriculture and the increase in the need for water has led to overexploitation of groundwater in the Semnan plain. In this paper, the occurrences pattern of regional subsidence phenomenon in the south and south-east of the Semnan plain and also the zoning of this region in terms of the susceptibly of land subsidence have been discussed. In this research at the first step data of 18 piezometers for 24 years period (May 1993-2017) were used to provide iso-potential lines of drawdown groundwater table and unite hydrograph of the plain. Furthermore, for the determination of type and thickness of the subsurface layers some data including piezoelectric log, geoelectric studies and geological map were used. Then, using the drawdown groundwater level map and the subsurface layers conditions map, a subsidence susceptibility map of the Semnan plain was prepared. The results showed that during the period of 1993-2018 continuous extractionof groundwater caused a drop of 18.9 meters of groundwater level and provided conditions for consolidation of clayey layers and land subsidence. The subsidence hazard zonation map indicates that the area with a high potential of subsidence in this plain is located in the northeastern part of the plain and in the south-southwest of the Semnan industrial park.