Temperature-dependent lateral earth pressures in partially saturated backfills

Abstract

Stability analysis of retaining structures supporting variably saturated backfills is a topic of great significance in civil engineering. However, the backfill soil may be exposed to elevated temperature; this may result in changes of the saturation state, thus posing temperature-dependent effective stress, variable suction stress and different hydro-mechanical characteristics to partially saturated soils. In the present work, the significant impact of elevated temperature is incorporated into the soil-water retention curve and suction stress-based effective stress formulations. Accordingly, the lower bound theorems of limit analysis in conjunction with finite element and second-order cone programming are adopted so as to thoroughly examine the impact of elevated temperature on the coefficients of lateral earth pressure acting on a model retaining wall backfilled by two hypothetical partially saturated soils; a granular material (sand) and a cohesive material (clay). The effective stress-based formula for the strength of variably saturated soils is implemented to modify the conventional Mohr–Coulomb yield criterion. In general, it was shown that for unsaturated clay backfills, the active lateral earth pressure decreases while the passive lateral earth pressure increases with increasing the induced temperature; however these influences were observed to be small for the sand backfill.