Mechanism of rockburst in deep-buried tunnels with prefabricated structural planes of different inclinations

To investigate the influence of structural plane dip angles on the rockburst mechanism in deep-buried tunnels, limestone samples from a deep mine in Yunnan, China, were prepared into cubic specimens (100 mm×100 mm×100 mm) with a central hole (ϕ=50 mm) to simulate underground tunnel. Prefabricated fissures were introduced in limestone samples to replicate structural planes. A high-speed camera system was employed to monitor the initiation and evolution processes of rockburst in specimens with varying inclination angles of structural plane. Additionally, compression tests on these specimens were simulated using PFC software to analyze the failure modes and stress-strain characteristics of tunnel structures under different inclination angles of structural plane. The results show that structural planes alter the transfer paths of stress and energy within the surrounding rock, leading to localized stress concentration in adjacent rock mass and triggering premature rockburst. Structural planes significantly amplify rockburst intensity, with intense shear ejection as the dominant failure mode of limestone surrounding rock. The degree of surrounding rock damage varies with the inclination angle of structural planes. Minimal damage occurs with the inclination angles of 0° and 180°, while the most severe damage is observed at an inclination angle of 90°. Furthermore, the inclination angle of structural planes exerts a pronounced influence on the stress characteristics of circular tunnels. Based on experimental data, the stress characteristic parameter of circular tunnels (σ_αmax/σ_c) was quantified in terms of inclination angle of structural plane.