Active earth pressure in unsupported vertical trenches in vadose zone

ABSTRACT: Accurate calculation of active earth pressure is vital in analyzing the stability of unsupported trenches. In conventional soil mechanics, active earth pressure can be calculated using the earth pressure theories proposed by Rankine or Coulomb. However, typically, unsupported trenches are excavated into soils that are in a state of unsaturated conditions. In this case, the field conditions such as type of soil, matric suction profile, and rainfall events should be considered in calculating the active earth pressure. The infiltration of rainfall into unsupported trenches excavated in the vadose zone can result in sudden failure, which poses a serious risk to the lives of field workers. Therefore, it is of utmost importance to estimate the behaviours of unsupported trenches under rainfall events to ensure the safety of field workers within unsupported trenches. In the present study, a series of numerical analyses were carried out to estimate the variation of active earth pressure and the optimal location of shoring and load that would maximize the stability of an unsupported vertical trench considering rainfall infiltration by extending the conventional Rankine earth pressure theory. Analyses are carried out for multiple levels of groundwater table and rainfall intensities.