AbstractIn this study, the coefficient of lateral earth pressure at rest (K0) for sand subject to freezing and thawing was investigated, focusing on the effect of pore water volume. Unfrozen (UF), frozen (FR), and thawed (TH) conditions were all addressed and considered in the investigation. Experimental testing programs were established and conducted to characterize the values of K0 for different degrees of saturation (Sr) and relative densities. The effects of freezing and thawing on K0 were significant for the fully saturated condition of Sr=100%, whereas they were negligible for partially saturated or unsaturated conditions. For FR condition, the values of K0 were low during the early loading stage and increased gradually as σv′ increased due to the breakage of pore ice. The lower K0 values for FR condition were more significant for higher Sr. After thawing, a net volume increase was observed for Sr=100%, thereby an increase in K0 took place. This phenomenon was suggested as an important aspect for the stability of retaining structures during thawing periods. The computerized tomography images and the shear wave velocities for UF and TH conditions confirmed the effect of Sr on K0. A K0 estimation method considering the effect of freezing and thawing was proposed, showing an improved prediction of K0.