2.1.3 Soil and Rock

Soil and rock structures show much resemblance with the behavior of concrete and other quasi-brittle materials. Unlike the concrete models, the elements applied in soil and rock analyses are mainly the plane strain, axisymmetric and solid elements. The material models which can be applied for the analysis are the plasticity models, like Mohr-Coulomb and Drucker-Prager, and the multi-directional fixed crack model to describe the tensile behavior. In plane strain and axisymmetric situations, the multi-surface plasticity models can also be applied [§5.1.3].

Ambient influence, for instance from chemical concentration, can be modeled in combination with the plasticity and multi-directional fixed crack models. Faults in rock could be modeled with interface elements where a Coulomb friction model can be used to describe the relation between the traction and the relative displacement [§9.3].

Rock plasticity.

DIANA offers a special model for rock plasticity: the Hoek-Brown model [§5.1.6].

Clay.

For the analysis of clay and clay-like materials, DIANA offers the Cam-clay model [§5.1.4]. This model combines a nonlinear elasticity model with a plasticity model. Furthermore, two special features are available for soil mechanics: the initial stress ratio can be defined [§9.6.2] and short-time loading on saturated soil can be described with the undrained option [§9.6.3].

Sand.

For the analysis of porous media like sand, DIANA offers the Modified Mohr-Coulomb model [§5.1.5]. A major extension compared to the regular Mohr-Coulomb model is an elliptically shaped compression yield surface (cap) with optional hardening.

Simple Soil Models.

Two simple soil models are available: the Hardin-Drnevich model and the Ramberg-Osgood model [§9.6.1].

Liquefaction.

Special models are available to analyze the liquefaction of soil due to earthquakes [§9.7].