1 Abstract

Understanding how rocks deform over time can lead to elimination of conservatisms in regards to excavation-design, especially, in the case of nuclear waste repositories where the lifetime of these projects exceeds one million years. Such projects are designed to be constructed in good quality rocks, which can behave in a brittle manner. It is commonly assumed that brittle rocks are unlikely to exhibit time-dependent deformations. In this study it is proven that not only can brittle rocks deform over time with different rates but also the expected failure time is dependent on the visco-elastic parameters of the specific rock specimen.

2 Introduction on time-dependent behaviour of rocks

In the literature (Singh 1975, Aydan et al. 1993, Malan et al. 1997, Hargos et al. 2008, Brantut et al. 2013, Paraskevopoulou et al. 2016, Paraskevopoulou 2016) time-dependency of rock under load has been widely discussed. However, in practice, there is often a miscomprehension and misinterpretation of the different time-dependent phenomena, and the mechanisms involved. The main time-dependent phenomena are defined and summarized in Fig. 1.

Fig. 1 illustrates examples of failures in geotechnical engineering due to these phenomena (column on the left), their main behavioural characteristics with time (middle column), and a description of the process involved (right column) are shown. This paper focuses on investigating the time-dependent behaviour of brittle rocks under a constant (controlled) stress-state by performing a series of uniaxial static load (creep) tests on two types of limestone.

This content is only available via PDF.
You can access this article if you purchase or spend a download.