Pipelines in landslide-prone areas are highly susceptible to damage or rupture under soil movement, posing severe threats to social stability and national security. However, research on pipeline failure mechanisms across different landslide types remains insufficient. Therefore, this study employs large-scale indoor model tests to investigate the interaction mechanisms between pipelines and soil (pipeline-soil interaction) in translational landslide zones through comparative experiments. The results indicate that: (1) The failure process of translational landslides is characterized by initial sliding at the slope crest under loading, which progressively drives the lower soil mass, ultimately resulting in global slope instability. The sliding mass displacement exhibits a top-to-bottom reduction pattern. (2) Pipelines traversing slopes laterally significantly enhance slope stability by providing measurable anti-sliding resistance. (3) Pipeline displacement under sliding mass action occurs in the downslope direction, yet its trajectory deviates from the sliding mass movement. (4) Strain analysis reveals that the pipeline experiences peak strain in the middle region of the sliding mass and at the sliding-non-sliding interface, with the middle region being the primary location for initial yielding and fracture. This study advances the understanding of pipeline-sliding mass interaction mechanisms in translational landslides and offers critical insights for improving pipeline safety and reliability.

The rotational-translational loess landslides are widely distributed in northwest China, usually posing threats to the surrounding residents and infrastructure. These loess landslides are characterized by the formation of multiple slip surfaces during the run-out process, and the mechanisms of this phenomenon in loess landslides have not been sufficiently investigated. Therefore, in this paper, we integrated the elastic-plastic strain softening constitutive law into the original DualSPHysics code to extend its application in simulating rotational-translational loess landslides. Two benchmark cases are studied to validate the model, the failure process of a cohesive soil slope without strain softening and that of a sensitive clay slope with strain softening. The results illustrate that our model can effectively predict large deformation. Then, the run-out process of the Caijiapo landslide in northwest China is analyzed by the modified model to investigate its failure mechanism. The results illustrate that the failure pattern of the Caijiapo loess landslide is very different from the typical retrogressive failure of clay landslides. The main slip surface of the Caijiapo landslide is controlled by the pre-existing structural plane. The second and third slip surfaces of this landslide are formed inside the sliding mass due to stress redistribution during the run-out process. Three scarps are formed in the landslide deposit because of the formation of multiple slip surfaces. This deposition morphology can be well reproduced by the SPH model taking strain softening into account, while the results using an SPH model without considering strain softening cannot capture this essential deformation characteristic.