Modelling landslide liquefaction, mobility bifurcation and the dynamics of the 2014 Oso disaster

Iverson, Richard M.; George, David Lloyd

doi:10.1680/jgeot.15.lm.004

Cited by 123 publications

(97 citation statements)

References 35 publications

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“…(Figure 2a of Johnson et al [2016] is a plot of H cm /L cm .) We agree with that an actual friction reduction mechanism is needed to explain the high mobility of large runout landslides, and this is supported by detailed observations showing that some long runout slides have H cm /L cm < 0.15 Iverson and George, 2016], much lower than static rock friction of μ ≈ 0.5 À 0.7 [Jaeger et al, 2009].…”

Section: H/l H CM /L Cm and The Low Friction Of Large Landslidessupporting

confidence: 89%

Reply to comment by Iverson on “The reduction of friction in long runout landslides as an emergent phenomenon”

2016

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Here we address the comments by Iverson (2016) on our recent work concerning the reduction of friction in long runout landslides. Iverson (2016) questions the veracity of our models and suggests that high basal pore fluid pressure is the dominant mechanism reducing friction in long runout landslides. The main goal of our work was to elucidate the mechanism responsible for the apparent reduction of friction and long runout occurring in the landslide simulations of Campbell et al. (1995), which did not include an interstitial fluid. We found that the apparent reduction of friction in large slides could be explained by acoustic waves causing sliding to preferentially occur at pressures below the expected overburden, a mechanism reminiscent of acoustic fluidization. Such a mechanism is required to explain the long runout of dry landslides such as those on the Moon and other airless or waterless bodies. While our models provide no estimates of the effect of fluids on landslide runout, we have demonstrated a mechanism that increases runout distances that does not involve fluids.

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Section: H/l H CM /L Cm and The Low Friction Of Large Landslidessupporting

confidence: 89%

Reply to comment by Iverson on “The reduction of friction in long runout landslides as an emergent phenomenon”

2016

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“…On the other hand, a loosely packed assembly contracts in response to shearing. These processes play a dramatic role in the dynamics of fluidized granular flows, from their initial destabilization to their final deposition (Andreini et al 2013;Iverson et al 2010;George and Iverson 2011;Montserrat et al 2012;Rondon et al 2011;Iverson and George 2016).…”

Section: Introductionmentioning

confidence: 99%

A two-phase two-layer model for fluidized granular flows with dilatancy effects

et al. 2016

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We propose a two-phase two-thin-layer model for fluidized debris flows that takes into account dilatancy effects, based on the closure relation proposed by Roux and Radjai (1998). This relation implies that the occurrence of dilation or contraction of the granular material depends on whether the solid volume fraction is respectively higher or lower than a critical value. When dilation occurs, the fluid is sucked into the granular material, the pore pressure decreases and the friction force on the granular phase increases. On the contrary, in the case of contraction, the fluid is expelled from the mixture, the pore pressure increases and the friction force diminishes. To account for this transfer of fluid into and out of the mixture, a two-layer model is proposed with a fluid layer on top of the two-phase mixture layer. Mass and momentum conservation are satisfied for the two phases, and mass and momentum are transferred between the two layers. A thin-layer approximation is used to derive average equations, with accurate asymptotic expansions. Special attention is paid to the drag friction terms that are responsible for the transfer of momentum between the two phases and for the appearance of an excess pore pressure with respect to the hydrostatic pressure. For an appropriate form of dilatancy law we obtain a depth-averaged model with a dissipative energy balance in accordance with the corresponding 3D initial system.

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“…Moreover, use of unsmoothed DEM topography may have its greatest advantages in finite‐volume computations that employ adaptive mesh refinement to facilitate efficient numerical simulations in large domains, which may include billions of DEM cells (LeVeque et al, ). In such cases use of unsmoothed DEM data eliminates the need to recompute base topography as the computational grid evolves (e.g., George et al, ; Iverson & George, ).…”

Section: Introductionmentioning

confidence: 99%

Basal Stress Equations for Granular Debris Masses on Smooth or Discretized Slopes

Iverson

George

2019

JGR Earth Surface

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Knowledge of basal stresses is essential for analyzing slope stability and modeling the dynamics and erosive potential of debris flows and avalanches. Here we derive and test new algebraic formulas for calculating the shear stress τ and normal stress σ at the base of variable‐thickness granular debris masses in states of static or dynamic equilibrium on slopes. The formulas include a lateral pressure coefficient κ, but use of a fixed value κ = 0.7 yields predictions of σ that on average err by less than 3% and of τ that on average err by less than 13% in matching basal stresses measured in six large‐scale experiments involving wet debris masses with varying geometries and compositions. Much larger prediction errors result from use of infinite‐slope or shallow‐debris approximations. Specialized versions of the new formulas apply if basal topography is discretized and represented by a “staircase” function in a digital elevation model. Use of these formulas to assess static limiting equilibrium conditions shows that the apparent basal Coulomb friction angle ϕtread of debris that engages friction acting on the horizontal surfaces (or “treads”) of a staircase sloping at an angle θ is generally described by tanϕtread = tan (ϕ − θ)+κ tan θ, where ϕ is the true basal friction angle of the same debris in contact with a uniformly sloping bed. Differences between the values of ϕ and ϕtread can greatly influence the results of numerical simulations that use unsmoothed digital elevation model topography to calculate the stability or dynamics of debris masses on slopes.

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Modelling landslide liquefaction, mobility bifurcation and the dynamics of the 2014 Oso disaster

Cited by 123 publications

References 35 publications

Reply to comment by Iverson on “The reduction of friction in long runout landslides as an emergent phenomenon”

Reply to comment by Iverson on “The reduction of friction in long runout landslides as an emergent phenomenon”

A two-phase two-layer model for fluidized granular flows with dilatancy effects

Basal Stress Equations for Granular Debris Masses on Smooth or Discretized Slopes

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