Cyclic undrained behaviour of silty sand under partial cyclic reversal loading
Cyclic undrained behaviour of sand with different fines content was investigated through stress-controlled cyclic triaxial tests with partial stress reversal. The test results were analysed based on the concept of equivalent granular state parameter, Ψ*. Three different types of behaviour were observed: namely cyclic instability, cyclic mobility and an in-between transition behaviour. Cyclic instability was observed for loose sand-fines mixtures with a positive Ψ*, and can be related to the instability stress ratio of monotonic test with same equivalent granular void ratio, e* as long as instability was controlled by the compression side of the stress space. On the other hand, cyclic mobility was observed for samples had negative Ψ*. However, transition behaviour was observed for samples with Ψ* values close to zero.