Suitable Shearing Rate for Triaxial Testing of Intermediate Soils under Vapor Controlled Medium to High Suction Range: Fid-Bau Portal

Suitable Shearing Rate for Triaxial Testing of Intermediate Soils under Vapor Controlled Medium to High Suction Range

Patil, Ujwalkumar D. / Hoyos, Laureano R. / Puppala, Anand J.

Triaxial testing of unsaturated geomaterials under suction-controlled conditions can be accomplished via either axis-translation technique, typically for matric suction values up to 1500 kPa; or the vapor-equilibrium technique, which allows for control and measurement of total suction at significantly higher values. In either case, empirical assessment of a suitable shearing rate depends essentially upon the nature of volume change and stress–strain response of the test soil during shearing. The main objective of the present work was to empirically assess the appropriate strain rate for drained triaxial testing of intermediate geomaterials in the higher total suction range. To accomplish this goal, a series of suction-controlled conventional triaxial compression (CTC) tests were conducted on statically compacted specimens of silty sand, at five different shearing rates, under a constant, vapor-induced total suction of 300 MPa (300,000 kPa). Total suction was controlled, prior to and during the shearing stage, via a fully automated relative humidity (RH) chamber assembled to a newly implemented, double-walled triaxial apparatus. The critical state based criteria for assessing the appropriate shearing rate at higher total suction values are compared and discussed over a wider range of induced suction states. In addition, observations pertaining to particle breakage and soil dilatancy phenomenon, associated to triaxial shearing at higher total suctions, are also discussed.