Estimating the Stand-Up Time of Unsupported Vertical Trenches in Vadose Zone

Abstract

Stability of trenches in vadose zone primarily depends on matric suction distribution with depth. The depth of ground water table, type of soils, and local climate conditions such as rainfall are major contributing factors to the matric suction distribution, and thus the stability of unsupported trenches. Trench failures are labelled as the cause of many work-related injuries and deaths in the construction industry. Hence, the design of unsupported trenches should be done with utmost caution. The focus of this study is directed towards investigating the influence of rainfall infiltration on the stand-up time of unsupported vertical trenches excavated in unsaturated coarse- and fine-grained soils. For this, a series of numerical analyses were carried out to estimate stand-up time of unsupported vertical trenches considering possible practical scenarios such as various rainfall intensities and groundwater table depths, impermeable membranes on the ground surface, and tension cracks. The commercial geotechnical modelling software, GeoStudio was used in this study to simulate excavation, redistribution of pore-water pressure due to excavation, rainfall infiltration, and slope stability analysis.