UBCSAND3D Model

The Plaxis Liquefaction Model (UBC3D-PLM) is a full 3D implementation of the UBCSAND model by P. Byrne et.al. Initially started as a User Defined Soil Model back in 2010, since the release of PLAXIS 3D 2017 and PLAXIS 2D 2018 this model is now part of the standard material library for Bentley Geotechnical SELECT Entitlement [GSE] (former PLAXIS-VIP) subscribers. More information is found in the Material Models manuals.

Model history

Update March 2018

Available as standard material model since 2D 2018.00 for PLAXIS Dynamics users with Bentley Geotechnical SELECT Entitlement [GSE] (former PLAXIS-VIP) (now GSE)

Update September 2017 

Available as standard material model since PLAXIS 3D 2017.00 for PLAXIS Dynamics users with Bentley's Geotechnical SELECT Entitlement [GSE] activated.

Update January 2016 - Version of October 2016
Known issue ID: SW-10967 (Solved)

An issue with internal iterative procedures that could cause a frozen calculation process has been solved:
Inside the UBC Sand user defined soil model, there are some internal iterative procedures to deal with local (numerical) accuracy. However, in some cases, these internal iterative procedures could start diverging. Now since this is an internal procedure inside the user-defined soil model (UDSM) DLL, there will be no new communication from the UDSM to the calculation progress screen, and so the calculation gives the impression that it is frozen. In the calculation progress screen, you would see a large global error (i.e. > 1) at that moment and the calculation would not converge.

This issue with the diverging internal iterative procedures has been resolved with the version from December 2016 (v2016.0.0.0).

Update June 2013 - version 2013.150.150.0
Based on recent user feedback we improved the robustness of the model significantly.
The model description and formulation is not changed, neither the behavior of the model in a stress point (Plaxis SoilTest facility) where the strain increments are relatively small. However, the improved performance and behavior of the model can be seen in numerical models run with PLAXIS like the finite element validation example in the report (Dynamic Centrifuge, Chapter 2.3).

Note that the model is still under development and validation and a final release will be available as soon as this process comes to a final stage.

Update January 2013
A new updated version of the UBC3D-PLM model (UBCSAND 3D) implemented as a User Defined Model for Plaxis 2D and 3D. The updated formulation is in accordance with the 904aR version of the 2D UBCSAND as published recently by Beaty and Byrne (2012).
Moreover, the robustness of the model is significantly improved and more accurate results are achieved in boundary value problems. The speed of calculation in several cases where the new model is tested is dramatically improved.

The new model includes:

• An updated densification rule which is valid for stress paths which do not start from the isotropic axis. Higher accuracy achieved when anisotropic consolidation is considered.
• An updated rule for modelling the post-liquefaction behaviour in loose sands and the cyclic mobility in dense sands.
• An improved formulation which gives higher accuracy in boundary value problems and significantly improves the speed of calculation.

Note that the model is still under development and validation and a final release will be available as soon as this process comes to a final stage.

Update June 2012
Plaxis improved the PLAXIS UBCSAND-3D soil model to give higher accuracy in cyclic loading. More specifically, the new update predicts more accurately the evolution of the excess pore pressures with the use of a soil densification rule for cyclic loading and two yield surfaces for primary and secondary loading respectively. Moreover, the post liquefaction behaviour can be approximated after an extensive calibration of the input parameters with the proper element tests.
Plaxis is working on a full 3D implementation of the latest UBCSAND formulation (904aR; Beaty & Byrne, 2011). This version is expected to be released end 2012 / early 2013.

Update November 2011
Plaxis has extended the original UBCSAND model into a full 3D formulation and has made this available as a user-defined soil model (UDSM) to our users under the conditions of the Bentley Geotechnical SELECT Entitlement [GSE] (former PLAXIS-VIP) support. It is known that the version of the PLAXIS UBCSAND-3D model (October 2011) exaggerates the development of excess pore pressure upon cyclic loading, which leads to earlier liquefaction than what is observed for sands in reality. This will at least result in a conservative conclusion with respect to stability.