Analytical and numerical investigations on the one-dimensional permanent deformations of granular materials under repeated deviatoric loading

This work proposes a theoretical framework for the permanent deformation calculation of unsaturated granular materials. The approach is based on the separation of the Soil Water Retention Curve (SWRC) into three linear phases. This representation makes unique the wetting and drying paths with a newly defined normalized suction s/s*. The same unique curves of permanent deformations with the normalized suction value are then developed. The proposed approach is initially applied to reproduce the experimental permanent deformation of two granular materials with different water contents on the wetting and drying paths. The effect of the deviatoric stress on the permanent deformations is also considered in the multi-stage loading tests. The good correspondence between the predicted and experimental results confirms the good capacity of the proposed approach. Finally, the proposed approach is injected in a finite difference code to model the tests performed on the two aforementioned granular materials. The numerical simulations show that both modeling concepts with variable and non-variable suction profile predict well the experimental results of the single-stage and multi-stage tests. The maximum deflection of a typical pavement is also estimated at the different hydraulic states, giving more credits to the proposed approach.

Automated summary

This study proposes a theoretical framework for calculating the permanent deformation of unsaturated granular materials. By separating the Soil Water Retention Curve into three linear phases and developing unique curves based on normalized suction values, the proposed approach successfully replicates experimental results. The effect of deviatoric stress on permanent deformation is also considered, and the approach is applied in a finite difference code for simulation.