Access constitutive models with the latest release of PLAXIS3D and PLAXIS2D Featured

With the new release of PLAXIS 2D CONNECT Edition V20 Update 1 (V20.01) and PLAXIS 3D CONNECT Edition V20 Update 1 (V20.01) the PLAXIS installation now comes with all PLAXIS User Defined Soil Models (UDSM), including these newly developed constitutive (soil) models: Masonry; OC-Clay; Hoek and Brown with softening (HBS).

Many rocks exhibit the phenomenon of strain softening under loads. Modeling this softening behavior is therefore very important for rational design involving rocks (e.g. tunnels, mines, excavations). However, numerical solutions often fail to converge when modeling this softening behavior. This new PLAXIS model has built-in features to assure convergence during the softening path. 

Hoek & Brown (HB) failure criterion has been often employed over the past decades in practical engineering applications due to its intrinsic capability to capture the non-linear behaviour of different types of rocks. The former idea of HB (Hoek, 1968; Hoek and Brown, 1980), was to link some concepts of fracture mechanics and the macroscopic response resulting from the non-linear trend of the initial yielding.

This Hoek & Brown model implemented in PLAXIS refers to the formulation proposed by Jiang (2017) which can guarantee at the same time smoothness and convexity of the yield surface and plastic potential. The underlying implementation is further enhanced with the following constitutive features:

• The initial non-associativity with the ability to simulate the non-linear evolution of the dilation in the postpeak regime;
• A softening rule implemented through two different formulations;
• A tension cut-off in the tensile regime of the stress space;
• A rate-dependent version of the HB model is here used to solve the mesh-dependency of the numerical solution when the brittle failure is characterized by a strong concentration of strain in narrow shear bands.

With Hoek & Brown model with softening now available in PLAXIS 2D and PLAXIS 3D users can advance their rock modeling. A 45-page background document for this model is also available. When enabling the Geotechnical SELECT Entitlement [GSE] when starting the PLAXIS application, this model becomes available in the Parameters tab when selecting "User-defined" for the Material model.

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