This paper presents experimental studies on a compacted expansive soil, from Nanyang, China for investigating the at-rest lateral earth pressure σL of expansive soils. The key studies include (i) relationships between the σL and the vertical stress σV during soaking and consolidation, (ii) the influences of initial dry density ρd0 and moisture content w0 on the vertical and lateral swelling pressures at no swelling strain (i.e. σV0 and σL0), and (iii) evolution of the σL during five long-term wetting-drying cycles. Experimental results demonstrated that the post-soaking σL-σV relationships are piecewise linear and their slopes in the passive state (σL > σV) and active state (σL < σV) are similar to that of the consolidation σL-σV relationships in the normal- and over-consolidated states, respectively. The soaking σL-σV relationships converge to the consolidation σL-σV relationships at a threshold σV where the interparticle swelling is restrained. The σL0 and σV0 increase monotonically with ρd0; however, they show increasing-then-decreasing trends with the w0. The extent of compaction-induced swelling anisotropy, which is evaluated by σL0/σV0, reduces with an increase in the compaction energy and molding water content. The σL reduces over moisture cycles and the stress relaxation in the σL during soaking is observed. An approach was developed to predict the at-rest soaking σL-σV relationships, which requires conventional consolidation and shear strength properties and one measurement of the σL-σV relationships during soaking. The proposed approach was validated using the results of three different expansive soils available in the literature.

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Keywords: Lateral earth pressure, Expansive soil, Soaking, Vertical stress, Swelling pressure