Cyclic response of Ottawa sand under different test conditions: Cyclic triaxial, unidirectional and bidirectional direct simple shear

Cyclic direct simple shear (CDSS) and cyclic triaxial (CTX) tests are the most commonly used methods to determine cyclic strength of soils. Cyclic resistance ratio determined from CTX tests is generally corrected to be comparable to that of CDSS test results and the field stress condition for level ground. In this study, CRR values are determined for Ottawa sand using three testing methods: CTX, unidirectional and bidirectional CDSS. CTX specimens were saturated and isotropically consolidated. CDSS specimens were dry and consolidated under presumed K-0 condition and shearing phase was conducted at constant volume. The correction factor (C-r) determined using the results from three different methods is compared with published values. The effect of bidirectional loading on C-r was found to be more complex than a simple 10% reduction coefficient suggested in the literature and warrants further investigation.