Evaluation of single oedometer test to measure the collapsibility of soils in Golestan province

From an engineering geological point of view, collapsible soils are of the problematic soils. Due to this distribution of loess soils through the Golestan province, physical and mechanical properties of loess soils from north, center and south of Golestan province were studied and collapsible coefficient has been determined. Results show that measured collapsible coefficient by standard single oedometer test method for soil samples with more than17% calcite, are lower than real collapsible coefficient. The decrease of collapsibility coefficient is due to the speed of cement solution and saturation of water within the mold of consolidation container by calcium ions. It should be noted that, rapid saturation of water within the mold of consolidation container, prevents of destruction of cement bounds between the soil particles. Therefore, based on the results of this research, it has suggested to changes the water of mold every 6 hour and the testing time to be continue for 7 days. In this condition, the fresh water can breaks the bounding between the soil grains and leads to fully destroy of soil structure. Based on the results of this research for loess soils of Golestan province, in order to avoid of hazards of non-real estimation of collapsibility coefficient in hydraulic Structures, a modified single oedometer test has been suggested.