Prediction of creep behaviour from stress relaxation behaviour of a sand under triaxial compression

Abstract

Creep behaviour of granular materials is related to the viscosity of material. The viscous properties can be evaluated by stepwise changing the strain rate and performing sustained loading during monotonic loading (ML) at a constant strain rate and also by ML tests at different constant values of strain rate. This study, uses the experimental and analysis results from a previous study for determining the appropriate parameters for simulations of long-term creep and stress relaxation. The creep behaviour can be predicted by stress relaxation behaviour, which is performed for a much shorter period. The non-linear three-component (NTC) model was used to simulate time histories of creep strain and stress relaxation. The simulated creep duration and stress relaxation duration are equal to 10 years/stage. Systematic relationships between the elapsed times and the irreversible strain increments in sustained loading (SL) and stress relaxation (SR) simulation necessary to reach the same irreversible strain rate were developed. There are two sets of relation for analysing the predicted long-term time history of creep strain from a short-term time history of stress relaxation. The first set is the relationship between time for creep and time for stress relaxation. It can convert the time for stress relaxation to the time for creep at the same irreversible strain rate. The second set is the relationship for the irreversible strain. The time histories of creep, which were predicted from stress relaxation behaviour tend to increase with an increase of stress ratio. Moreover, the prediction in this framework was well simulated.