New formula predicts tunnel lining durability, cutting design guesswork
Researchers have derived the first predictive formula linking concrete-to-rock bond strength with structural durability in hard rock tunnels. The finding lets engineers estimate how long tunnel linings will last based on a single easy-to-measure property, potentially reducing costly over-engineering and safety failures in major infrastructure projects.
Originaltitel: On the bond fracture energy of rock-concrete interfaces in hard rock tunnels
<p>In hard rock tunnelling, the bond between the shotcrete (sprayed concrete) lining and the rock substrate is critical for structural safety and long-term performance. With a complete bond, composite action between the shotcrete and rock exists, which reduces cracking and fallout risk. Despite its importance, a predictive function for tensile bond fracture energy as a function of tensile bond strength remains unclear. In this study, experimental data from a range of literature were compiled, standardised, and analysed to investigate this relationship. The dataset includes results from multiple quasistatic direct uniaxial tensile and three-point bending tests across different surface roughness levels, curing conditions, and shotcrete compositions. A statistically significant correlation between tensile bond strength and fracture energy was identified. A linear relationship is proposed, motivated by the observed data distribution, providing a simple function for an initial estimate of the fracture energy when bond strength is known. The model was compared to and agreed with finite element simulations that reproduced experimental data. The proposed function is therefore suitable as an initial estimated input for numerical modelling of rockshotcrete interfaces and for energy-based analytical formulations.</p>