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- Title
Interplay Between Friction and Cohesion: A Spectrum of Retrogressive Slope Failure.
- Authors
Wang, Bin; Wang, Di; Hicks, Michael A.; Feng, Xia‐Ting
- Abstract
Retrogressive failures occur in slopes consisting of sensitive materials such as snow or quick clay. They can be triggered by a small disturbance at the slope toe, but can cause propagated failure spreading miles away. Understanding the physical mechanism and predicting the retrogressive failure process are particularly important. Previous studies have discussed the failure criteria, the soil properties or the method of numerical modeling of retrogressive slope failure. However, little attention has been paid to the microscopic failure mechanism, especially relating to various possible failure patterns. In this study, multiscale modeling is incorporated to study the physical mechanism of different retrogressive failure patterns, including earth flow, flowslide and spread failure, within a unified framework. Utilizing multiscale analysis, we found that earth flow failure is related to the shear failure of granular materials. In contrast, the development of macroscopic shear bands is accompanied by tensile failure. As shear and tension failures are typical failure mechanisms of frictional and cohesive materials, it is deduced that friction and cohesion effects play key roles in different retrogressive failure patterns. Therefore, the distributions of attractive and repulsive contact forces are explored and a novel parameter η is proposed to quantify the interplay between friction and cohesion. Further analysis proves that η can capture the effect of friction and cohesion and distinguish different retrogressive failure patterns. Finally, a spectrum of retrogressive failures for a granular slope is established, in which the failure mechanism is explained by the changeable dominant effect, that is, frictional or cohesive in soil. Plain Language Summary: Slope failure is a common geo‐hazard that occurs in nature and engineering. For example, a sensitive clay consisted soil slope can easily propagate for miles, leading to catastrophic damage to human lives and properties. Previous researchers mainly study the slope failure processes/mechanisms on the scale of soil blocks, lacking observations at the soil particle scales. In this research, a hierarchical multiscale modeling is proposed, which enables the simulation of both the retrogressive slope failure process and interactions between soil particles. The mechanisms of various retrogressive failure patterns are thereby explored, including earth flow, flowslide, and spread failure. The earth flow tends to fail near the surface by shearing, where the shear strength is mainly determined by the friction between particles. The flowslide fails in a retrogressive pattern, shown as bulks of soils moving after bulks. The soil in shear bands fails under stretching mainly, where the strength is determined by the cohesion between particles. The spread failure is more complex, combining the influences of friction and cohesion. The friction effect controls the bottom of slopes, contributing to the translational shear band and spread failure of slopes. A spectrum to classify different failure patterns is established at the end. Key Points: Hierarchical multiscale modeling is carried out to explore the mechanism of various retrogressive failure modes in granular slopesThe interplay between friction and cohesion near the slope surface determines the development of earth flow or flowslide failure patternThe friction effect controls the bottom of slopes and contributes to the translational shear band and the spread failure of slopes
- Subjects
COHESION; EARTHFLOWS; MULTISCALE modeling; CLAY soils; GRANULAR materials; SOIL particles; FRICTION
- Publication
Journal of Geophysical Research. Solid Earth, 2023, Vol 128, Issue 2, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2022JB026008