Steady state-creep of rock salt Improved Approaches for Lab Determination and Modeling to describe transient,stationary and accelerated creep, dilatancy and healing

摘要

Actual problems in geotechnical design, e.g. of underground openings for radioactive waste repositories or high-pressure gas storages, require sophisticated constitutive models and consistent parameters for rock salt that facilitate reliable prognosis of stress-dependent deformation and associated damage from the initial excavation to long times. Fortunately in the long term the response of salt masses is governed by its steady state creep behavior. However, because in experiments the time necessary to reach true steady creep rates can last time periods of some few days to years, depending mainly on temperature, an innovative but simple creep testing approach is suggested. A series of multi-step tests with loading and un-loading cycles allow a more reliable estimate of stationary creep rates in a reasonable time schedule. In completion, the advanced strain-hardening approach of Günther/Salzer is used which describes all relevant deformation properties of rock salt, e.g. creep and damage induced rock failure, comprehensively within the scope of an unified creep approach. The capability of the combination of improved creep testing procedures and accompanied modelling is demonstrated by recalculating multi-step creep at different loading and temperature conditions. Thus reliable extrapolations relevant to in-situ creep rates (10~(-9) to 10~(-13) s~(-1)) become possible.