Infiltration of rainwater into a tension crack and its impact on the stability of unsupported vertical trenches in unsaturated soils

Abstract

The development of a tension crack behind the crest of an unsupported trench creates a path for infiltration of rainwater. This phenomenon accelerates the failure of an unsupported trench reducing the soil's shear strength due to decreased matric suction.

A series of numerical analyses were carried out using SLOPE/W and SEEP/W software to investigate the influence of hydraulic conductivity function of tension crack on the stand-up time of unsupported vertical trenches, considering groundwater table levels (1m, 3m and 5m) and rainfall intensities (0.11, 0.36, 1.08, 3.60 and 10.8 mm/hr). It was assumed that the trenches were excavated into Indian Head till. Seepage through a tension crack was simulated by using four different approaches available in the literature.

Two case studies that used to validate the research approaches demonstrated that the stability of a UVT with a tension crack during a rainfall event can be assessed by simulating the tension crack as a void space.