Damage and healing properties of rock salt: Long-term cyclic loading tests and numerical back analysis

Abstract

The Chair for waste disposal technologies and geomechanics has analysed the effects of mechanical cyclic loading of rock salt by laboratory testing. The tests were characterized by cyclic loading at stress conditions above the stress level where dilation will occur and stress conditions below the dilation stress level. The duration of the cyclic loading was 250 days to analyse in detail the damage induced creep behaviour and healing behaviour of rock salt by long term cyclic and constant loading at different stress levels. At first, this paper presents in detail the loading history and the observed creep behaviour, volume damage and ultrasonic wave velocity during the long term cyclic tests. This was done to validate, with a back analysis, the ability of the constitutive model Lux-Wolters to image the measuring results observed from the tests, a short description of the constitutive model Lux-Wolters is given thereafter. A comparison between the measured data obtained from the cyclic loading tests and the computed data obtained from a numerical back analysis of the tests indicates clearly that the Lux-Wolters model is able to image the load bearing behaviour of rock salt considering cyclic and constant loading above as well as below the damage stress level. That is, transient and stationary damage free creep behaviour, damage induced creep behaviour as well as healing induced creep behaviour could be computed using one unique set of parameters for the total loading history. © Springer-Verlag Berlin Heidelberg 2013.