Strain distributions for shotcrete failure in hard rock tunnels

Shotcrete linings are a commonly used support system in hard rock tunnel construction, providing flexibility and minimizing construction time. Understanding the strain behaviour of shotcrete under different loading scenarios and interface conditions is vital for optimizing tunnel support design and ensuring long-term structural integrity. In this study, distributed optical fibre sensors were installed in laboratory prepared specimens, in which the lining was subjected to two distinct loading scenarios: a rock load and a distributed load. The specimens in the study consisted of two concrete layers where the substrate slab was either hydro-demolished or ground prior to casting a top fiber reinforce concrete layer. Key findings from the experiments reveal that specimens with rougher substrate surfaces exhibit higher post-failure ductility compared to those with ground surfaces, suggesting superior performance after peak loading.