Mechanical behavior and crack evolution mechanism of layered cracked rock samples reinforced by grouting-anchor bolt

Crack defects and layered structures critically affect the stability of rock engineering, and effective reinforcement is essential to maintain structural integrity. In this study, uniaxial compression tests were performed on layered rock-like specimens with different crack lengths using bolt reinforcement and grouting–bolt synergistic reinforcement. Acoustic emission (AE) monitoring and high-speed imaging were employed to analyze mechanical response and crack evolution.Results indicate that peak strength and elastic modulus decrease linearly with increasing crack length for both reinforcement methods. However, grouting–bolt synergistic reinforcement significantly mitigates this degradation and preserves higher bearing capacity under long-crack conditions. Bolt-reinforced specimens tend to develop through-going cracks at crack tips and bedding interfaces. In contrast, the grouting–bolt group exhibits more dispersed crack initiation, increased crack numbers, and delayed crack coalescence.AE analysis shows that the bolt group experiences earlier high-energy events before peak stress, with a rapid rise in cumulative energy and a pronounced decline in the b-value. The grouting–bolt group displays concentrated high-energy events near or after peak stress and a slower b-value reduction, indicating weakened crack localization. Multi-parameter coupling reveals that synergistic reinforcement enhances interfacial load transfer and modifies energy dissipation paths, thereby suppressing long-crack-induced instability.