Bedrock-soil layer slopes (BSLSs) are widely distributed in nature. The existence of the interface between bedrock and soil layer (IBSL) affects the failure modes of the BSLSs, and the seismic action makes the failure modes more complex. In order to accurately evaluate the safety and its corresponding main failure modes of BSLSs under seismic action, a system reliability method combined with the upper bound limit analysis method and Monte Carlo simulation (MCS) is proposed. Four types of failure modes and their corresponding factors of safety (Fs) were calculated by MATLAB program coding and validated with case in existing literature. The results show that overburden layer soil's strength, the IBSL's strength and geometric characteristic, and seismic action have significant effects on BSLSs' system reliability, failure modes and failure ranges. In addition, as the cohesion of the inclination angle of the IBSL and the horizontal seismic action increase, the failure range of the BSLS gradually approaches the IBSL, which means that the damage range becomes larger. However, with the increase of overburden layer soil's friction angle, IBSL's depth and strength, and vertical seismic actions, the failure range gradually approaches the surface of the BSLS, which means that the failure range becomes smaller.

Earthquakes contribute to the failure of anti-dip bedding rock slopes (ABRSs) in seismically active regions. The pseudo-static method is commonly employed to assess the ABRSs stability. However, simplifying seismic effects as static loads often underestimates rock slope stability. The development of a practical stability analysis approach for ABRSs, particularly in slope engineering design, is imperative. This study proposes a stability evaluation model for ABRSs, incorporating the viscoelastic properties of rock, to quantitatively assess the safety factor and failure surface under seismic conditions. The mathematical description of the pseudo-dynamic method, derived in this study, accounts for the viscoelastic properties of ABRSs and integrates the Hoek-Brown failure criterion with the Kelvin-Voigt stress-strain relationship of rocks. Furthermore, to address concurrent translation-rotation failure in ABRSs, upper bound limit analysis is utilized to quantify the safety factor. Through a comparison with existing literature, the proposed method considers the effect of harmonic vibration on the stability of ABRSs. The obtained safety factor is lower than that of the quasi-static method, with the resulting percentage change exceeding 5%. The critical failure surface demonstrates superior positional accuracy compared to the Aydan and Adhikary basal planes, with minimal error observed between the physical model test and the numerical simulation test. The parameter sensitivity analysis reveals that the inclination of ABRSs exhibits the highest sensitivity (Sk) value across the three levels of horizontal seismic coefficient (kh). The study aims to devise an expeditious calculation approach for assessing the stability of ABRSs during seismic events, intending to offer theoretical guidance for their stability analysis. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Vegetation plays an important role in improving slope stability. It is crucial to develop simple and effective methods for assessing the stability of vegetated slopes. Based on upper bound limit analysis, a method was proposed to analyse the stability of a two-dimensional vegetated slope with uniform root architectures under steady transpiration state. The effects of water absorption and reinforcement by vegetation roots on slope stability were considered using this method. Parametric studies were performed to investigate the effects of the soil type, root depth, plant transpiration rate, root tensile strength, slope angle and internal friction angle on slope stability. Several generic stability plots were provided. The results showed that roots significantly improved soil cohesion but slightly affected the internal friction angle. Root systems could provide additional soil cohesion. Horizontally and vertically distributed roots imposed the best mechanical reinforcement effect on the soil. The shear strength increases by 1.78 times. Compared with that of plain soils, the critical state line (CSL) of the root-soil composite moved upwards. The soil type strongly influences the pore water pressure. With increasing plant transpiration rate, root tensile strength and root depth, vegetated slope stability can increase by 58 %. The slope stability decreases by 50 % with increasing slope angle. The stability number (Ns) decreases with increasing internal friction angle. The effects of water absorption and reinforcement by roots on slope stability decrease with increasing desaturation coefficient and saturated permeability coefficient. Compared with that of loess and sand slopes, the reinforcement effect of vegetation roots is more significant for the stability of clay slopes.