It is observed in simulations of excavation projects using the Hardening Soil model (or HS small model) that the soil below the bottom of the excavation behaves less stiff than in reality. The reason is that the stiffness of soil is stress dependent and excavation releases the stress on top, however, in reality the stiffness will not reduce so much due to the pre-consolidation stress. Therefore, in the GHS model (generalized hardening soil model) the stress dependency formulation of the Hardening Soil small model has been altered in order to account for the pre-consolidation stress. The Generalized Hardening Soil model (GHS) is a more modular version of the original Hardening Soil small model. It has several switches which allow the users to change the configurations of strain and stress dependency.
In order to obtain the model, send your request to sales@plaxis.com. Support on the use of the generalized hardening soil model is only provided for this DLL under the conditions of the PLAXIS VIP support service and Article 10 of the End-User Licence Agreement.
Status May 2016
Known issue ID: 5362
In the implementation for the Generalized Hardening Soil (GHS) model version 2014.223.0.0 (March 2014) the internal parameter determination is only stored for one material dataset at the beginning of a calculation phase. This means that when having more than one material dataset using the Generalized Hardening Soil model, these internal parameters for the stiffness behaviour will only use the parameters from one material dataset, and this gives incorrect behaviour for all the other material datasets using the GHS model.
We are working on a solution for this. For the time being, users are strongly advised not to define more than one GHS material dataset in the model until we release the fixed user defined soil model files.