ESTIMATION OF MATERIAL PARAMETER FOR A NON LINEAR KELVIN MODEL

Abstract

The present study is concerned with the estimation of material parameters (a, b, N and i70 ) for non linear Kelvin model representing visco elastic behaviour. Material parameters are calculated for hydrostatic stress and deviatoric stress condition both. For estimation of these parameters triaxial test are performed at constant stress condition. Triaxial test is carried out total stress and hydrostatic stress condition. For hydrostatic stress condition volume changes were noted with respect to time till the changes in volume become negligible. The volumetric strains were computed by dividing the volume change by the original volume of sample. The strain vs time plot was made for the hydrostatic stress condition, considering one third of the volumetric strain as axial strain. For total stress condition the vertical displacement and volume changes of sample were observed with respect to time. Axial strain for total stress condition is directly found by dividing the vertical displacement with original length of sample. The deviatoric strains were computed by substracting one third of the volumetric strains (from hydrostatic stress condition) from the axial strains obtained under total stress condition and the strain vs. time curve for deviatoric stress condition also plotted. Constant a and b have unique value for each stress condition but constant N and i7„ have different value for each stress level. Constant N and 77o are calculated for each stress level and a relation between stress and N and rho is established. For validation of result settlement calculated by Kelvin model is compared with settlement calculated by consolidation method. In Kelvin model non linear approach is taken therefore it gives better result for settlement than ordinary consolidation test.