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The failure patterns and retrogression distances in sensitive clays induced by river erosion are two significant factors of concern in landslide risk assessment. For the former, empirical criteria, based on past events and numerical results, can hardly produce a unified guideline and explain their complex mechanism. For the latter, the capacity of the river cross section is rarely considered in existing studies, even though the failed soil would deposit on the riverbed and further affect upslope failure extension. The present study proposes an analytical method to quantitatively assess the failure patterns and retrogression distance by combining the shear band propagation method (SBP) with limit analysis on active block failure. A closed‐form active earth pressure (CAEP) and the shape function of the failure surface are proposed with the variational calculus method (VCM), providing a tool to understand the transformation mechanism of the failure patterns. The criteria for initiation failure positions and stages are formulated following the competition results between the induced minimum slope‐parallel force by foot unloading and the proposed CAEP. Further, the terminal retrogression distance is given considering two possible river cross sections. The proposed CAEP solution is validated against Buss's solution and further applied to a parametric study on the failure patterns. Finally, three practical cases are analyzed with the proposed method, and the predictions are shown to agree well with the field observations.

Edge waves generated by subaerial landslide‐tsunamis (SLTs) often have potentially huge amplitudes that can endanger human lives, offshore structures, coastal cities and port facilities around reservoirs. Maximum edge wave run‐up (RuM) is the most important parameter for SLT hazard mitigation in an engineering context. This study aimed to investigate the effects of the hill slope angle α on RuM, the first edge wave run‐up Ru1 and the first edge wave decay in the near field Ru1(r/h) through 84 laboratory experiments, which were conducted in a three‐dimensional river channel with α values varying from 15° to 40°. For smaller α values, we found that RuM increased with the increase in α while for large α values exceeding 30°, RuM decreased with the increase in α. An empirical equation considering the effect of α was proposed for the prediction of RuM in the near field, which was well verified by a real case. Additionally, the first edge wave run‐up decay along the shore is also discussed in this paper. This work could have some favourable implications for the preliminary hazard assessment of SLTs.

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The pronounced discrepancies in triggering intensities and failure modes observed in downhill progressive landslides pose significant challenges to their risk prediction and mitigation. Instead of focusing on an individual triggering event and/or failure mode as done in previous studies, this study systematically explores the instability issues of downhill progressive failure in long slopes. A unified analytical model is proposed to understand these observed discrepancies, in which criteria for the initiation of slope failure corresponding to all possible failure modes are formulated. Accordingly, a simple framework is established that is capable of predicting possible triggering thresholds and failure modes in advance. This would improve the accuracy of landslide hazard assessment, which is often reduced by the unknowns of the failure mechanisms and inaccurate assumptions of stress distribution along the failure surface. Furthermore, three practical cases are analyzed based on the established framework, and the findings are compared with field observations and existing studies, showing good consistency. This work gives an insight into a systematic understanding of the various failure phenomena in downhill progressive landslides and provides a reference for their risk assessment and subsequent decision-making.

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