Evaluation Of The At-Rest Coefficient Of Earth Pressure In Unsaturated Residual Soil With A New Suction-Controlled Device

Data on the at-rest coefficient of earth pressure (K-0) in undisturbed, unsaturated residual soils are rarely found in the literature. This article describes a new suction-controlled system developed for measuring K-0 in residual soil samples, as well as corrections required to get a sensible evaluation of K-0. The K-0 device comprises a rigid chamber containing a 4-in diameter triaxial sample. Suction is controlled using the axis translation technique. The results of tests performed in mature and young residual soils originated from phacoidal gneiss are presented and discussed. The testing interpretation using either Bishop's or Fredund's approaches provide similar results. It is shown that K-0 varies with both suction and net stress and is affected by the degree of weathering of residual soils.