Post-localisation analysis of drained and undrained dense sand with a nonlocal critical state model

Mesh-sensitivity of post-localisation analysis is an inherent drawback of continuum based finite element methods. Out of many available regularisation techniques, the nonlocal method has proved to provide viable solutions. It can be implemented at the constitutive level without adjusting equilibrium equations. This study aims to apply the nonlocal theory to critical state based Nor-Sand model and evaluate its applicability to simulate drained and undrained biaxial compression tests of dense sand. The nonlocal averaging of void ratio leads to the regularisation of the state parameter. Mesh independent load-displacement curves of dense sand are obtained during both softening and at the critical state. Hence the nonlocal theory is capable of adequately regularising the post-peak dilation for both fully drained and globally undrained analysis. Along with scaling, it can be used to obtain a physically realistic force-displacement response during the shear localisation analysis of granular materials without the need for extreme mesh refinement. Finally, limitations of the nonlocal regularisation are discussed with a parametric study.