Sand is a naturally occurring, cohesionless, granular material with varying morphology. It has been well studied as a model frictional material, and the strength of the sand ensemble is derived from the inter-granular friction. Facets of sand behaviour, such as the inherent anisotropy and effect of intermediate principal stress, are extremely important to model and predict the constitutivity. A complex stress field is required in order to investigate the effect of intermediate principal stress on the failure behaviour of angular sand. Such stress fields can be replicated in the laboratory using a hollow cylinder torsional (HCT) testing apparatus. A slew of experiments are carried out at a particular density under drained conditions by varying intermediate principal stress ratio `b'. The experimental observations are studied in the framework of classical critical state soil mechanics and the results are analyzed using plasticity theory. The effect of intermediate principal stress ratio on the non-coaxial and failure behaviour is highlighted.