Authors : Mohammed Y. Fattah, Ahmed A.H. Al-Obaidi and Mohammed Kh.A. Al-Dorry
Abstract: The gypseous soil is a soil which has enough gypsum content to change or affect its engineering properties. Gypseous soils are usually stiff in their dry state due to the cementing action provided by gypsum but great loss of strength and pronounced increase in compressibility occur when gypsum is dissolved by partial or full saturation. This problem becomes more severe when the water flows through such soils causing loss of mass due to the leaching of gypsum. The soil used in this research is disturbed natural gypseous soil having three different percentages of gypsum; 55, 30 and 18%. Nine model tests were conducted to investigate the variation of suction, settlement and total vertical stress with time, also, study the effect of wetting on the volume change of unsaturated gypseous soil. The soil container used had with inner dimensions of (length 700×width 700×height 600 mm). A square footing of (100 mm) sides was used. Models in loose, medium and dense soils were prepared. Watermark monitor data logger model 900M was used to record the soil suction in kPa. The saturation process involved the complete saturation until the suction sensors readings approach to zero. The saturation process was established by allowing the water to infiltrate through the soil in upward-direction (from bottom to top of the model) with steady flow and head of 2 m. It was concluded that for soil with different gypsum contents, the air entry value decreases with the increase of the dry unit weight while the residual suction decreases slightly with the increase in dry unit weight. After reaching about 14.8 kN/m3, the residual suction starts to increase with the increase of dry unit weight. The residual water content decreases with the increase of gypseous content and soil density for all conducted tests.
Mohammed Y. Fattah, Ahmed A.H. Al-Obaidi and Mohammed Kh.A. Al-Dorry, 2018. Determination of the Soil Water Characteristic Curve for Unsaturated Gypseous Soil from Model Tests. Research Journal of Applied Sciences, 13: 544-551.