Influence of soil-water characteristic curve on the safe height and stand-up time of unsupported vertical trenches in unsaturated soils

ABSTRACT Geotechnical projects are typically initiated with an unsupported vertical trench (UVT) in unsaturated soils. In this case, it is fundamental to consider the contribution of soil suction toward the shear strength and hydraulic conductivity of soils when analyzing the stability of UVTs. The soil–water characteristic curve (SWCC) is a vital tool for estimating the variations of shear strength and hydraulic conductivity of soils with soil suction. In this study, numerical analyses were conducted to investigate the influence of SWCC on the safe height and stand-up time of UVTs in sandy and glacial till materials. SWCCs were established using three SWCC fitting models based on experimental data. The analysis results demonstrate that it is essential to understand the critical differences between the SWCCs obtained using different fitting models and their influence on the safe height and stand-up time of UVTs, rather than simply comparing the estimates.