The effect of ambient humidity on the stiffness and strength of a hyper-compacted silty clay for earth building

Abstract

The effect of pore suction and water content on the engineering properties of partially saturated soils has been extensively studied by geotechnical researchers. It is well known that unsaturated soils become stiffer, stronger and less permeable as suction increases and saturation decreases. The results from these studies are however not directly applicable to the analysis of earth buildings, which are made of coarser soils compacted to a much denser state. The present paper investigates the mechanical behaviour of a low porosity earth building material equalised at different degrees of saturation. Cylindrical samples were statically compacted to a high pressure of 100 MPa at the optimum water content. This resulted in a dry density of about 2.3 g/cm3, corre-sponding to a porosity of between 13% and 14%, which is uncommonly low for standard geotechnical materials. After compaction, the samples were equalised at different humidity levels inside a climatic chamber before being subjected to triaxial tests under different confinement. Results from these tests enabled the definition of the material stiffness and strength envelopes at different levels of ambient humidity.