In deep underground engineering, rock bolt performance depends on complex interactions between installation and loading conditions – such as prestress from pre-tensioning and rock loading rate – and plastic properties of high-strength and high-toughness (HSHT) steels, including yield strength and strain hardening rate (SHR). The present study addresses the insufficient understanding of these interactions by employing an advanced multi-scale crystal plasticity (CP) model that integrates field monitoring data from the Muzhailing highway tunnel in China. This model is used to elucidate the deformation and energy absorption behaviors of two HSHT steel variants – near-persistent reduced-hardening (NPR) steels and twinning-induced plasticity (TWIP) steels – under variable rock loading scenarios. The CP model captures microstructural mechanisms, such as dislocation slip and deformation twinning, revealing that the effective energy absorption rate (EAR) and deformation stability are primarily governed by the rock loading rate, whereas effective strain and energy absorption density (EAD) are significantly influenced by yield strength and average SHR. It is found that EAR is enhanced, yet EAD is reduced, by the pre-tensioning process, with effects being more pronounced in steels exhibiting lower yield strength. At rock loading rates exceeding , elevated prestress triggers deformation relaxation and pronounced fluctuations. Compared to TWIP steels, NPR steels are demonstrated to achieve larger, more stable deformations and superior energy absorption due to their persistently low hardening rate. These insights bridge geotechnical engineering and materials science, offering a theoretical framework and technical guidance for designing advanced rock support systems in deep underground applications.
Wang et al. (Sun,) studied this question.