There has been a wide effort to develop constitutive models to aid prudent engineers or scientists in understanding materials’ behaviour in rock mechanics. Hoewever, there is still a lot of work to be done when considering time-dependent behaviour that can lead to instabilities and progressive failures which cannot be captures when considered the commonly used constitutive models, usually static. This paper aims to provide more insight into understanding time-dependent behaviour at both the laboratory and excavation scale. Building on the findings this study develops in-depth understanding on capturing the time-dependent behaviour in brittle rock materials proposing a new approach to be adopted when simulating numerically this behaviour highlighting key considerations both at the laboratory and tunnel scale.
Underground space is increasingly considered a sustainable engineering solution accommodating the ongoing and emerging needs of human beings, from transportation and natural resources to storage needs and energy applications (Paraskevopoulou et al., 2022). An ongoing increase in infrastructure development has been observed during the last two centuries. The latter raises the concern that many such infrastructures are approaching or have exceeded their design lifetime. Figure 1 shows the average lifetime of various infrastructures based on design standards such as EUROCODE and British Standards.
The question then arises is what current engineers and scientists should do to either re-purpose these infrastructures and prolong their lifetime or optimise current design practices to accommodate such future challenges. It is evident that many underground infrastructures have exceeded their lifetime and are still in operation. Great examples are the Victorian railway tunnels in the UK (Atkinson et al., 2021) that currently need refurbishment but still planning to be in operation (Smith et al., 2023). Nevertheless, the performance of a geo-structure over time remains, making the time-dependent behaviour of host rocks for underground structures crucial today (Paraskevopoulou, 2021). Consequently, the primary aim of this paper is to give more insight into how brittle rock types perform over time in underground conditions.
