Assessment of zones prone to sinkhole using ground penetrating radar and soil properties in Central Iran

Abstract

Land subsidence and sinkhole, natural and anthropogenic events, occur globally especially in arid and semi-arid regions. The major problem of this phenomenon is over exploitation of ground water. Identification of important factors in the soils as soil properties were prone to sinkholes detection of subsurface holes as soil texture essentially. For detecting subsurface layers were used Ground Penetrating Radar (GPR) in the study area. The study area is Abarkooh alluvial plain of about 250 km2 is part of the Eghlid-Abarkooh watershed. For assessment potential zones prone to sinkhole, eight routs were determined in two different regions for the measurement of GPR and soil chemical, physical and mechanical properties. In GPR sections around the sinkholes, there were some breaks in subsoil layers and found subsurface cavities and on the side of the mountain slopes, the subsoil layers were uniform and there was no sign of breaks in subsoil layers and cavities. Regarding soil characteristics, soil texture near sinkholes was silt loam, sandy loam and loamy sand and on the side of mountain slope was Skeletal sandy loam, Skeletal loamy sand and Skeletal sand because of the existence of gravel on the slopes of the mountain. For evaluating soil parameters in two selected regions, some differences were observed such as Ca2+/Mg2+ in lime, COLE and Atterberg limits. Mg2+ in lime is more than to Ca2+ near sinkholes and the limes of the soils were dolomitic type and unstable. The amount of COLE and Atterberg limits as divergence index were high near sinkholes but on the side of mountain slopes were low. An increase in Mg2+ in lime, COLE and Atterberg limits near sinkholes proved the activity of clays and their movement underground and the GPR results confirmed the clay activity as breaks in stratigraphy traces to depth of 5 m and these soils are prone to sinkhole phenomenon. It has been concluded that GPR and Soil properties is the best way to determine areas that prone to sinkhole and also to detect the safe area for construction and contracting works. It is suggested that land conservation be introduced as the best alternative near sinkholes and redrawing the plan of urban development, construction of electric tower and railway from lowlands to the piedmonts as detected the safe area.