DEBRIS-FLOW MOBILIZATION FROM LANDSLIDES

TLDR

Landslides mobilize into debris flows through Coulomb failure, pore‑pressure‑induced liquefaction, and conversion of translational energy into granular temperature, processes that can act independently or synergistically and were previously modeled with fixed debris rheologies. This review focuses on models where debris behavior evolves with changing pore pressures and granular temperatures. One‑dimensional infinite‑slope models quantify how pore pressures and granular temperatures drive the transition from Coulomb failure to liquefaction. Multidimensional experiments reveal additional complexities and show that field debris‑flow mobilization can occur via at least two distinct modes.

Abstract

▪ Abstract Field observations, laboratory experiments, and theoretical analyses indicate that landslides mobilize to form debris flows by three processes: (a) widespread Coulomb failure within a sloping soil, rock, or sediment mass, (b) partial or complete liquefaction of the mass by high pore-fluid pressures, and (c) conversion of landslide translational energy to internal vibrational energy (i.e. granular temperature). These processes can operate independently, but in many circumstances they appear to operate simultaneously and synergistically. Early work on debris-flow mobilization described a similar interplay of processes but relied on mechanical models in which debris behavior was assumed to be fixed and governed by a Bingham or Bagnold rheology. In contrast, this review emphasizes models in which debris behavior evolves in response to changing pore pressures and granular temperatures. One-dimensional infinite-slope models provide insight by quantifying how pore pressures and granular temperatures can influence the transition from Coulomb failure to liquefaction. Analyses of multidimensional experiments reveal complications ignored in one-dimensional models and demonstrate that debris-flow mobilization may occur by at least two distinct modes in the field.