SALT Workshop

1. Joint project on constitutive models: Conclusions from phases I – III
and introduction of project WEIMOS
Andreas Hampel
Hampel Consulting, Mainz, Germany
7th US/German Workshop on
Salt Repository Research, Design, and Operation
Washington, DC
September 7-9, 2016
Abstract
Well-tested constitutive models and calculation procedures are required for reliable numerical
simulations performed for the design, stability analysis, and evaluation of the long-term behavior
of underground repositories for radioactive wastes in rock salt. A main goal of the calculations is
to check and prove the long-term integrity of the geological barrier.
In three joint projects between 2004 and 2016, constitutive models for the thermo-mechanical
behavior of rock salt were tested and compared by the following partners: From Germany:
Bundesanstalt für Geowissenschaften und Rohstoffe, Hannover (BGR, project I); Dr. Andreas
Hampel, Scientific Consultant, Mainz; Institut für Gebirgsmechanik GmbH (IfG), Leipzig;
Karlsruher Institut für Technologie (KIT); Leibniz Universität Hannover (LUH); Technische
Universität Clausthal (TUC); Technische Universität Braunschweig (TUBS, project III); from
the United States: Sandia National Laboratories, Albuquerque and Carlsbad, NM, (project III).
In these studies, numerous recalculations of systematic laboratory tests and simulations of
selected underground structures were performed in order to check the ability of the involved
models to describe reliably the deformation phenomena in rock salt – transient and steady-state
creep, evolution of damage and dilatancy (volumetric strains), creep failure and short-term
strength, post-failure behavior and residual strength – and their dependences of in-situ relevant
boundary conditions – stresses, temperatures, and deformation rates – in a wide range.
The partners performed the calculations successfully and the results were in good agreement
with each other and with experimental results from the laboratory and from in-situ
measurements. This demonstrates the applicability of the involved models and confirms that the
partners do have appropriate tools for model calculations.
The studies have also revealed needs for the further development of the models in four topics:
 Deformation behavior at small deviatoric stresses
 Influence of temperature and stress state on the damage reduction
 Deformation behavior resulting from tensile stresses
 Influence of inhomogeneities (layer boundaries, interfaces) on deformation
These subjects are explored experimentally and theoretically in the new joint project WEIMOS
(English title: “Joint project: Further development and qualification of the rock mechanical
modeling for a HLW disposal in rock salt”, period: April 1st, 2016 – March 31st, 2019) of the
partners Dr. Hampel, IfG Leipzig, LU Hannover, TU Braunschweig, TU Clausthal, and Sandia
National Laboratories.