System reliability analysis of jointed bedding rock slopes under seismic loading: Integrating multiple failure modes

Jointed bedding rock slopes are susceptible to multiple failure modes under seismic loading, yet conventional stability assessments relying on a single mode are insufficient and may introduce significant errors, potentially underestimating slope instability risk. This study established a novel system reliability framework, integrating four key failure modes—translational (TM), rotational (RM), upper rotational-lower translational (URLTM), and upper translational-lower rotational (UTLRM)—for seismic stability assessment. Utilizing Monte Carlo simulation, the framework explicitly accounted for inherent randomness and uncertainty in the strength parameters of joint surfaces and rock bridges. System reliability was evaluated using the minimum safety factor (F_S) to identify the dominant failure mode. The analysis reveals that using only a single failure model can introduce maximum errors in F_s exceeding 10%; with increasing c_r (cohesion) and φ_r (internal friction angle), the dominant failure mode changes from RM (not affected by the joint surface) to UTLRM/TM (controlled by the joint surface); as K_c (cohesion weakening coefficient) and K_φ (friction coefficient (tanφ_r) weakening coefficient) increase, failure is more likely at δ/β (joint surface angle/slope angle)=0.40~0.65; seismic action further increases the likelihood of joint-surface-controlled failure, increasing seismic action shifts the dominant failure mode from UTLRM to TM. These results offer direct support for the efficient determination of the dominant failure mode and sliding surface position in stability assessments of jointed bedding rock slopes.