Fundamental considerations on the numerical investigation of shear band phenomena in saturated and non-saturated frictional porous materials

Shear band phenomena, as for instance the well-known base failure and slope failure problems of geotechnical engineering, occur as a result of local concentrations of plastic strains in small bands of finite width. The mechanical reason for this behaviour lies in the basic properties of frictional materials, where, in the brittle regime, the plastic dilatation yields local softening effects. However, it is well known that the numerical description of shear band phenomena, e. g. in the framework of the finite element method, leads to an ill-posed problem, where, in particular, both the direction of the shear band and the shear band width itself strongly depend on the discretization, especially, on the mesh size. In the present contribution, two natural reguilarization mechanisms for liquid-saturated and empty granular porous materials are discussed. These mechanisms are (1) the inclusion of independent degrees of freedom in the sense of the Cosserat brothers and (2) the inclusion of the pore-fluid viscosity in the saturated case. It will be shown by the numerical example of the slope failure problem thatmicropolarity is the much stronger regularization tool than is fluid viscosity.     «

Shear band phenomena, as for instance the well-known base failure and slope failure problems of geotechnical engineering, occur as a result of local concentrations of plastic strains in small bands of finite width. The mechanical reason for this behaviour lies in the basic properties of frictional materials, where, in the brittle regime, the plastic dilatation yields local softening effects. However, it is well known that the numerical description of shear band phenomena, e. g. in the framework...     »