TRIAXIAL TESTING OF DRY, COHESIVE POWDER AND ITS APPLICATION TO A MODIFIED CAM-CLAY CONSTITUTIVE MODEL

Triaxial tests were performed on wheat flour to determine the constitu tive parameters for a modified Cam-clay model. This elastoplastic mode l consists of three critical-state parameters: lambda, kappa, and M. A dditionally, there are two parameters representing the initial conditi ons of a material: e0 and p(c). All critical-state parameters were det ermined directly from four different triaxial tests: drained compressi on, undrained compression, constant mean effective stress and hydrosta tic compression. The material parameters for the tested wheat flour, f ollowing standard statistical techniques, were: lambda = 0.13, kappa = 0.022 and M = 2.1. The model was tested by comparing model-calculated deformation under triaxial loading conditions identical to those used to determine the parameters. The comparisons between the modified Cam -clay model calculated values and measured values showed that drained triaxial compression tests and constant mean effective stress tests we re within the 95% confidence interval. The investigation proved that ( 1) standard triaxial tests and constitutive models can be successfully applied to dry, cohesive powders, and (2) constitutive parameters def ined in soils models can be determined for dry powders by modifying th e parameter determination procedure.