摘要：The gypseous soil is a soil which has enough gypsum content to change or affect its engineeringproperties. Gypseous soils are usually stiff in their dry state due to the cementing action provided by gypsumbut great loss of strength and pronounced increase in compressibility occur when gypsum is dissolved bypartial or full saturation. This problem becomes more severe when the water flows through such soils causingloss of mass due to the leaching of gypsum. The soil used in this research is disturbed natural gypseous soilhaving three different percentages of gypsum; 55, 30 and 18%. Nine model tests were conducted to investigatethe variation of suction, settlement and total vertical stress with time, also, study the effect of wetting on thevolume change of unsaturated gypseous soil. The soil container used had with inner dimensions of (length700×width 700×height 600 mm). A square footing of (100 mm) sides was used. Models in loose, medium anddense soils were prepared. Watermark monitor data logger model 900M was used to record the soil suction inkPa. The saturation process involved the complete saturation until the suction sensors readingsapproach to zero. The saturation process was established by allowing the water to infiltrate through the soilin upward-direction (from bottom to top of the model) with steady flow and head of 2 m. It was concluded thatfor soil with different gypsum contents, the air entry value decreases with the increase of the dry unit weightwhile the residual suction decreases slightly with the increase in dry unit weight. After reaching about 14.8kN/m3, the residual suction starts to increase with the increase of dry unit weight. The residual water contentdecreases with the increase of gypseous content and soil density for all conducted tests.
关键词：Gyspseous soil;collapsible;unsaturated;soil water characteristic curve;dry unit weight;soildensity;gypseous content
