Strength/volume change behaviour of compacted silty sand using a novel double-walled suction-controlled triaxial system

In recent decades, the state-of-the-art of understanding of unsaturated soil behaviour has been considerably enhanced by incorporating novel and advanced features to conventional triaxial testing equipment. This paper aims to investigate the influence of matric suction on the shear strength and volume change behaviour of compacted silty sand using a novel, fully automated, double-walled triaxial system. The axis translation technique has been used to induce constant suction states in the specimens. A series of suction-controlled Consolidated Drained (CD) tests on statically compacted silty sand specimens was conducted at different suctions and varying confining pressures. The influence of the applied matric suction on peak shear strength, post-peak stress-strain behaviour and the ability to attain the critical state line in p-q space is studied. The experimental results indicate that, apart from an increase in the shear strength, there is an upward shift in the critical state line of compacted silty sand as compared to that obtained under saturated conditions. The relationship between shear strength and matric suction is also described. The results also confirm the suitability and effectiveness of the novel apparatus in testing unsaturated soils under suction controlled conditions via the axis-translation technique.