Land subsidence and soil cracks monitoring by surveying on the clayey plain soils in Central Iran (case study: Yazd City)

Abstract

Land subsidence and soil crack has become a global problem and cases of subsidence have been identified in many places around the world. The studied area is clayey plain lands, located in the east of the city of Yazd. In this area, two types of soil crack are created, such as longitudinal and polygonal. To show the land micro movements, as a result of soil diversity after surface wetting and drying intervals, this experiment was done. Direct surveying, soil mechanical and crystal-chemical measurements were essential method of the research. The results showed that all index points were moved in different directions to about 2.3 cm during 11 months. The geochemical and crystal-chemical processes as neoformation of duripan features from amorphous silica in subsurface, where is petrocalsic horizon, have created permanent cracks. The soils according to Soil Taxonomy are Vertisols, and because of aridic soil moisture regime, petrocalcic horizon and duripan have been classified in Leptic Calcitorrerts subgroups. The gilgai formation is the result of soil moisturing and drying alternation in wet and dry months. Because of unstable land in this area, avoiding urban and rural developments is recommended.