Lateral residual stress effect on the swelling pressure of compacted expansive soil and microscopic mechanism

In pipeline engineering in expansive soil areas, swelling pressure is frequently determined by laboratory tests as an essential design parameter. During the processes of filling and rolling, lateral residual stress exists in the soil, which significantly influences the swelling pressure. In this study, a series of expansion and residual stress tests is conducted on compacted expansive soil s with different initial dry densities and moisture contents. The variation rules of the swelling pressure for different specimen preparation methods are compared. The effects of the initial conditions on the lateral residual stress are analyzed. The range of initial conditions for the influence of lateral residual stress on swelling pressure is investigated. In addition, based on the Mercury Intrusion Porosimetry (MIP), the change rule of the soil microstructure under different initial conditions is obtained. A microcosmic mechanism for the lateral residual stress acting on the vertical swelling pressure is proposed. The results demonstrate that the lateral residual stress increases with increasing dry density and decreases with increasing moisture content. Based on the variation range of the initial specimen condition, the influence of the lateral residual stress on the swelling pressure can be distinguished using slash (\({\omega }_{0}\text{=}112.5{\rho }_{0}-157.75\)). When the lateral residual stress exceeds the range of approximately 130–170 kPa, the swelling pressure is influenced, and the greater the lateral residual stress, the greater the effect.