Mapping soil arching-induced shear and volumetric strains in dense sands

Abstract

Arching is regarded as a ubiquitous phenomenon in geomaterials where a new stress field is created following partial, induced displacements in the geomaterial. In the past, less attention has been paid to the deformations associated with the arching effect. The Digital Image Correlation (DIC) technique was implemented to map the shear and volumetric strain fields where arching occurred in a dense sand layer placed in a trapdoor apparatus. Model tests were conducted under active and passive arching along with surcharge loading. It was observed that shear bands comprising of two sections with different orientation angles were formed. The orientation angles of the shear bands were associated with the dilation angle of the sand (the deformation related angle of the soil) rather than its internal angle of friction (the stress related angle of the soil). The magnitude of shear strains increased with trapdoor displacement. It was also found that strain localization was associated with dilation. Contraction zones were also detected in the sand layer specifically at the surface and on the trapdoor element. In addition, it was realized the shear bands developed in the passive arching condition possessed greater width and inclination angles compared to bands of the active arching situation. The local surcharge used in the experiments markedly affected the strain localization and volumetric strain patterns and magnitudes.