THE INCREMENTAL NONLINEARITY OBSERVED IN NUMERICAL TESTS OF GRANULAR MEDIA

Abstract eng:
Recently, incrementally nonlinear constitutive models have been proposed for granular media by several researchers. It seems that such generalization of constitutive relationship is the key to grasping true behaviors of granular media. However, it is very difficult to do rigorous evaluation of the validity of these models, because of the limitations inherent in available experimental measures. On the other hand, numerical simulations in terms of suitable discrete element methods have a capability to solve this problem. This paper demonstrates the incremental nonlinearity observed in numerical tests conducted by a discrete element method proposed by the author. Through a series of true tri-axial stress-probe tests, it is found that the direction of plastic strain increment changes with the component of stress increment that is orthogonal to the current stress and the yield surface normal. The result suggests that the plastic deformation is accompanied by multiple shear mechanisms. The stability in the incremental relationship between stress and strain is also discussed based on the calculated results of second-order work.

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