Investigating the trend of changes in horizontal and vertical shrinkage and mechanical properties of land subsidence and crack prone soils (Case study: Clay plain lands of East Yazd)

In the last two decades, the land subsidence, especially in fine-grain plains, cracks emerged in YazdArdakan plain, it is called soil crack. One of the important assumptions in relation to emergence of this phenomenon, withdrawal of water from underground aquifers and decrease the hydro dynamic pressure and dense sediment. This phenomenon happens in fine-grained sediment and caused damage to building structures, roads, masts. the case study is clay plain lands without desert pavement in East of Yazd. For sampling, 12 samples were taken from three points were selected which one of them in the vicinity of crack and two other points were within 100 meters of side of crack in each point, four profiles were drilled from zero to 120 cm depth. On samples some experiments such as the indicators of changing bulk modulus were measured in different moistures in galvanized metal cube boxes with dimensions of 20 cm, some experiments were done such as Atterberg limit tests, divergence and failure limit. The results showed that liquid limit of the crack’s territory is near to 29 percent and moisture limit of crack is close to 4 percent. the most vertical and horizontal shrinkage in crack soils were 11 and 6 percent respectively. In other words, in per meter depth of sediment, 11 cm subsidence in areas with moisture less than 4 percent is not unexpected. With regard to the specific circumstances of the area, is proposed structural projects, gas lines, water pipes and bridges is not done in these areas.