Abstract

Maps of fracture surfaces forming in fresh, deep road cuts through loess depict in detail the initiation and propagation of tensile fractures and the internal interrelations with shear fracturing and resultant mass caving. Failure progresses in three dimensions as a series of slabs. Each failure increment begins with a new tensile fracture within the recently excavated slope. The tensile fracture usually propagates in coordination with a shear fracture below, which frees the newly forming slab. These large-scale examples of fracturing uniquely illustrate progressive failure under the load of large masses. The quantitative details and general similarity to corresponding features in rock establish that the same kinematics apply over a great range of scales and even into strong materials. Loess failures appear, accordingly, to be useful not only for conceptualizing the process in engineering but also for comparing it with similar processes in geology and geomorphology.

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