Effect of time-based soaking on shear strength parameters of sand soils

Upon wetting of the gypseous soils, the apparent cementation by the gypsum is lost gradually leading to the collapse phenomena. Cracking and settlement of buildings are incidents. This paper investigates the effect of the time-based soaking process on the shear strength parameters of the sand soil. The soil samples are from site near the faculty of engineering at the university of Kufa in Al-Najaf, Iraq. The soaking durations on the soil samples are one week, two weeks and four weeks. These samples are tested in the shear box with different normal stress then the results of these samples are compared with result of reference sample (non-soaked sample). The results compared with available reported data and performing a probability analysis of the soaked results. The results show a decreasing in shear strength parameter (  ) with increasing soaking duration. The decreasing ratios are -3.83% and -12.68% related to the reference value (natural) for 2-weeks and 4-weeks respectively. According to probability analysis, the safety index equal to 1.73 for  -mean-value equal to  after 4weeks soaking (minimum value).