Impact of specimen preparation techniques on the Interpretation of the unsaturated shear strength of granular soils

ABSTRACT: Natural or man-made granular deposits are often unsaturated in practice where the presence of suction may contribute to their shear strength. The unsaturated shear strength of granular materials can be evaluated in the laboratory in conjunction with soil-water-retention (SWR) tests. However, before performing a test, specimen preparation techniques often alter the particle configuration which may consequently have an impact on the interpretation of the achieved results. The objective of this paper is to examine the impact of moist tamping and hydraulic deposition techniques on the interpretation of unsaturated shear strength for granular materials. To do so, a series of unsaturated drained triaxial tests are carried out on glacial till specimens from Quebec prepared with the mentioned techniques at different confining pressure. To complement the shear tests, drying soil-water retention curves of the glacial till are also obtained using the same specimen preparation techniques. The results showed that specimen preparation techniques could affect the shearing behaviour of granular soils. Ignoring a uniform test protocol for laboratory measurements corresponding to the granular deposit formation might affect the interpretation of the unsaturated shear strength since their behaviour is dependent on the physical properties of particles such as the particle shape and fabric isotropy.