Modelling the scale effect of granular media for strength and bearing capacity

This paper investigates a method of analysis for the scale effect on shear strength of sands – a fundamental problem of considerable importance to soil mechanics. The phenomena of scale effect for direct shear box tests and footing bearing capacity tests are briefly described and the available analytical methods are discussed. First, the couple-stress theory is reviewed and its extension to a Drucker–Prager type is illustrated. Subsequently, material constants are discussed. Attention is then focused on the internal length of sand, which is shown to be the key parameter for scale effect for granular soil. Then, the predicted results are compared with experimental results on two sands. The main observations of the comparison for the scale effect are sketched and its limitations are discussed.