Bearing capacity of unsaturated expansive soils

It is difficult to determine the bearing capacity of a foundation in unsaturated expansive soil, although this is most important. The bearing capacity of unsaturated expansive soil is related to the drying and wetting environment. Swelling pressure occurs when the soil volume change is constrained as an expansive soil is inundated. The expansive lateral pressure, induced by the swelling pressure is similar to the passive earth pressure. By considering the effect of the expansive lateral pressure in Terzaghi's bearing capacity formula, the bearing capacity of unsaturated expansive soil is derived. Because it is very difficult to measure suction in situ, the bearing capacity is expressed using the expansive lateral pressure offers a feasible approach to calculate the bearing capacity of a foundation in unsaturated expansive soil, when suction is not measured. Plate load tests to measure the bearing capacity in situ were performed for the foundation in natural soil and saturated soil immersed by water. The verification of the bearing capacity formulae presented in this paper is conducted by comparing the predicted results with the results of the plate load tests on unsaturated expansive soils in Handan and Bingxia, China.