Direct shear tests on reinforced sand

New data are presented from internal measurements in direct shear tests on sand. An interpretation is given for the plane strain angle of friction and the angle of dilation of sand in a direct shear test. The direct shear angle of friction deduced from the conventional analysis is shown to under-estimate the frictional shearing resistance of sand by about 20%. Results are presented from direct shear tests on reinforced samples and these are fitted by a limit equilibrium analysis in which all the parameters are independently measured. Plastic incremental strains cause dilation in dense sand and dominate the deformation with increasing stress ratio. The rate of increase of the reinforcement force in shearing sand is shown to depend on the angle of dilation. The maximum bond angle of friction between sand and the rough surface of reinforcement is also determined by plastic deformation in the sand. A theoretical analysis for the bond is supported by the test results which show that the maximum bond angle of f...