Experimental Setup to Measure the Development of Shear Bands in Transparent Sand

ABSTRACT A triaxial setup was developed to quantify the development of shear bands in transparent specimens. Transparent sand was prepared by index-matching fused quartz with a mixture of mineral oils. Latex membranes were found to be incompatible with the oil used in the transparent soil technique. Consequently, a custom, transparent, silicone triaxial membrane was developed for the triaxial testing. Water-saturated fused quartz tested with the custom membranes had an equivalent stress-strain response to those tested with latex membranes. Dense triaxial specimens prepared from a uniformly graded fused quartz, saturated with mineral oil, were tested at three different confining stresses. The displacement on two laser-illuminated sections through the specimens was measured using digital image correlation. From these displacement fields strain fields were developed that were used to orient the shear bands in 3-D. Subsequently, the inclination, orientation, and width of the shear bands were calculated. Consistent with the bulging mode of failure observed, a family of conjugate shear bands, rather than a discrete slip, was measured in each specimen. The shear bands were between 8.6 · D50 − 11.5 · D50 wide for the particle size and range of confining stresses evaluated in this study. Finally, the shear band inclination was found to increase with an increase in confining stress.