Prediction of creep strain from stress relaxation of sand in shear

The creep (CP) strain and stress relaxation (SR) of a clean sand, KMUTT sand, exhibiting non-Isotach viscous properties were evaluated by consolidated-drained triaxial compression (CDTC) tests on air-dried specimens. The test results are analysed based on the nonlinear three-component (NTC) model. Consistent simple empirical equations were derived to predict the elapsed time and the irreversible strain when a given irreversible strain rate takes place during CP loading from those at the same irreversible strain rate during SR loading. Noting that short-term SR tests are much simpler to perform than long-term CP tests, particularly when using an ordinary displacement-controlled axial loading device, a simple empirical method consisting of these empirical equations was formulated to predict creep strain for a relatively long period from SR behaviour for a relatively short period. The creep strains predicted by this empirical method are well comparable with the test results and also with those simulated by the NTC model. It is argued that prediction by the empirical method is relevant in case it is not practical to perform the NTC model simulation.