Influence of dilatancy on shear band characteristics of granular backfills

This study investigates the evolution of strain localisation and resulting failure surfaces within cohesionless backfills. For this purpose, 1g small scale model experiments are performed simulating the lateral translation of rigid retaining walls to active state using Akpinar sand. The physical model test set-up has transparent sidewalls that allow observation of soil deformations and progressive failure. Images captured at successive stages of the test are analysed using particle image velocimetry (PIV) in order to visualise the formation of shear bands. Test set-up is equipped with several pressure transducers which are used to measure the stresses within the model backfill. A well-known empirical equation is used to calculate peak dilatancy and friction angles of the backfill using the measured density and stress magnitudes. Thus, it was possible to examine the influences of dilatancy and strength characteristics of the granular backfill on localisation and shear band formation. Moreover, the evolution of shear bands with the movements of the model wall is examined and two new methods for the determination of shear band thickness are proposed. Finally, it is concluded that there is a strong correlation between shear band characteristics and the dilative properties of granular soils.