On the necessity of stochastic material descriptions in the computational analysis of soils

The necessity of considering stochastic imperfections in the numerical analysis of localisation phenomena in soils is demonstrated by means of a biaxial compression test on a viscoplastic material. The material strength, the Young's modulus and the softening modulus are considered to be random fields, for which the most probable realisations which lead to failure are sought through an optimisation algorithm. The influence is studied of the viscosity parameter of the material model on the nature of the most probable localisation pattern. It is shown that large values of the viscosity probably lead to a symmetric, bulging mode, whereas small modes probably lead to a single shear band.