Unsaturated Geomechanical and Physicochemical Characterisation of Soils Used for Adobe Blocks

A mechanical and physicochemical characterisation of soil used for adobe block production is presented in this paper, considering a geomechanical framework. The main research objectives were to apply the partially saturated soil mechanics theory and obtain some of the soil's physicochemical characteristics. The soil used in this research was extracted from Putaendo, Chile, as it is representative of the vernacular building of that region. The soil was classified as silty sand, of low plasticity. Further inspection showed a 7% content of organic matter. The unsaturated shear strength of the soil was obtained using a conventional shear box test, coupled with the soil–water characteristic curve (which was obtained using the filter paper technique) to estimate suction values. The soil–water characteristic curve had a similar shape as for other sands previously reported in the literature, but with a higher air entry and residual values. Results show that shear strength increases for drier soil samples, reaching an asymptotic value after the air entry suction of the soil. It is concluded that shear box tests without suction control can be used to estimate the unsaturated strength of soils and that the organic matter in soils can influence its cohesive strength, although further research on this aspect is required.