The influence of wetting and drying paths on the shear strength of a silty clayey compacted soil

Abstract

The vast majority of geotechnical projects are designed in saturated condition, aiming safety. However, when some conditions might be achieved, designing in unsaturated conditions may end up being economically interesting, while still safe. Therefore, this study aims at evaluating the shear strength behaviour of a silty clayey soil, with optimum moisture content of 16% and dry unit weight of 16,5 kN/m3 from south Brazil. From direct shear tests, performed in saturate and unsaturated conditions, with three different starting moisture conditions – 14%, 16% and 18%, and the same unit weight, this paper shows the influence of the wetting and drying paths on this material and its contribution to evaluate shear strength. The results showed that a variation of ±2% around the optimum, in drying and wetting paths, can significantly influence the behaviour of the studied material. The wetting process caused a small variation in comparison with the optimum, while the drying process resulted in increased shear resistance for all the analyzed samples. With this study, it was possible to obtain a better understanding of the behaviour of an unsaturated soil from south Brazil, when evaluating tradeoffs in project’s safety and economics.