Entrainment of debris in rock avalanches: An analysis of a long run-out mechanism
01 Sep 2004-Geological Society of America Bulletin (Geological Society of America)-Vol. 116, Iss: 9, pp 1240-1252
TL;DR: In this paper, the authors describe two recent cases from British Columbia, Canada, where rockslides entrained substrate on a very large scale, influencing the character of the events.
Abstract: Many rock avalanches entrain and liquefy saturated soil from their paths. Evidence for this includes mud displaced from the margins of rock avalanche deposits, substrate material smeared along the base of deposits, extrusion of liquefied soil upward through the deposits, and increases of volume. A hypothesis first suggested in 1881 and since reinforced by several authors suggests that entrainment of substrate material increases mobility. Although the process has been discussed in the literature for more than 100 years, few detailed and quantitative descriptions exist. The main purpose of this paper is to describe two recent cases from British Columbia, Canada, where rockslides entrained substrate on a very large scale, influencing the character of the events. Estimated volume balance curves, based on detailed field mapping, are provided for both cases. Dynamic analyses are carried out using a numerical model and using the same set of rheological parameters. The mechanism of material entrainment and displacement is discussed. The data suggest that rapid rock failures entraining very large quantities of saturated substrate material represent a special type of landslide, transitional between rock avalanche and debris avalanche. Many rock avalanches can thus be seen as end members of a continuum of phenomena involving rock failure followed by interaction with saturated substrate.
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TL;DR: The modified Varnes classification of landslides has 32 landslide types, each of which is backed by a formal definition as mentioned in this paper, and complex landslides are not included as a separate category type, but composite types can be constructed by the user of the classification by combining two or more type names.
Abstract: The goal of this article is to revise several aspects of the well-known classification of landslides, developed by Varnes (1978). The primary recommendation is to modify the definition of landslide-forming materials, to provide compatibility with accepted geotechnical and geological terminology of rocks and soils. Other, less important modifications of the classification system are suggested, resulting from recent developments of the landslide science. The modified Varnes classification of landslides has 32 landslide types, each of which is backed by a formal definition. The definitions should facilitate backward compatibility of the system as well as possible translation to other languages. Complex landslides are not included as a separate category type, but composite types can be constructed by the user of the classification by combining two or more type names, if advantageous.
1,973 citations
Cites background from "Entrainment of debris in rock avala..."
...Hungr and Evans (2004b) documented several cases where rock slides mobilized colluvial debris avalanches of volume comparable to the size of the initial instability and proposed the term rock slide-debris avalanche for such events....
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...The tall vertical head scarp of Mt. Granier is therefore not the base of an active sliding block, but simply an open tension surface....
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...More importantly, weak rock mass under shear stress tends to fail in a ductile manner (Hungr and Evans 2004a)....
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...However, in many cases observed in the field, the rock avalanche debris travels on a cushion of saturated material entrained from the flow path and liquefied by rapid undrained loading under the weight of the rock debris (Hungr and Evans 2004b)....
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...The 1248 rock avalanche at Mt. Granier, in the Savoy Alps, was the deadliest landslide in European history, destroying a regional town with some 5,000 inhabitants....
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TL;DR: A wide-ranging analysis of landslide geometry shows that soil-based landslides are generally less voluminous than landslides that involve the failure of bedrock, and provides refined metrics for estimating the volume of a landslide from the area of the failure as discussed by the authors.
Abstract: Landslide erosion is a primary control of landscape relief. A wide-ranging analysis of landslide geometry shows that soil-based landslides are generally less voluminous than landslides that involve the failure of bedrock, and provides refined metrics for estimating the volume of a landslide from the area of the failure
463 citations
TL;DR: Two microcomputer-based numerical models (Dynamic ANalysis (DAN) and three-dimensional model DAN3D) have been developed and extensively used for analysis of landslide runout, specifically for the purposes of practical landslide hazard and risk assessment.
324 citations
TL;DR: In this paper, the authors describe the entrainment of path material is an important feature of many rapid landslides and the associated increases in volume and changes in flow character can significantly influence mobility.
Abstract: Entrainment of path material is an important feature of many rapid landslides. The associated increases in volume and changes in flow character can significantly influence mobility. A simple materi...
313 citations
Cites background or methods from "Entrainment of debris in rock avala..."
...The 1999 Nomash River landslide In April 1999, during spring snowmelt, a rock slide– debris avalanche occurred in the headwaters of the Nomash River on western Vancouver Island, British Columbia, Canada (Guthrie et al. 2003; Hungr and Evans 2004a)....
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...2 m, agrees with field observations that the landslide covered the floodplain and spread too thinly to dam the river (Hungr and Evans 2004a)....
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...A simple index that quantifies volume change is the “entrainment ratio” (Hungr and Evans 2004a), defined as the ratio between the entrained volume and the initial landslide volume (accounting for expansion of the latter due to fragmentation of the initial failure)....
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...1 m (a maximum erosion depth was not specified in this simulation) corresponds with the field estimate of 8 m (Hungr and Evans 2004a)....
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TL;DR: In this paper, the authors investigated the causes and effects of landslide mobility and its impacts on a disastrous landslide that occurred on 22 March 2014 near Oso, Washington, USA, following a long period of abnormally wet weather.
263 citations
Cites background from "Entrainment of debris in rock avala..."
...…(including the first stage of landsliding on 22 March 2014), long-term volumetric relaxation of glacially unloaded fine-grained sediments at the base of the land- slide, or slow, shear-induced disaggregation of those sediments (cf. Hungr and Evans, 2004; Jibson, 2006; N.R. Iverson et al., 2010)....
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...Events of this type include the Ontake, Japan, debris avalanche of 1984 (Voight and Sousa, 1994), the Nomash River, Canada, landslide of 1999 (Hungr and Evans, 2004), and also the largest subaerial landslide in recorded history: the 2.5 × 109 m3 rockslide/debris avalanche that unleashed a lateral…...
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...At the base of this stratigraphic sequence lies a glaciolacustrine siltand-clay unit, similar to units in British Columbia, Canada, that have been prone to abrupt failure and landsliding (Fletcher et al., 2002; Hungr and Evans, 2004)....
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References
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Book•
01 Jan 1948
TL;DR: In this article, the authors present a survey of the properties of soils and their properties in terms of Hydraulics of Soils, Hydraulic and Mechanical Properties of Soil Exploration Hydraulic, Mechanical, and Hydraulic properties of soil.
Abstract: PHYSICAL PROPERTIES OF SOILS Index Properties of Soils Soil Exploration Hydraulic and Mechanical Properties of Soils THEORETICAL SOIL MECHANICS Hydraulics of Soils Plastic Equilibrium in Soils Settlement and Contact Pressure PROBLEMS OF DESIGN AND CONSTRUCTION Ground Improvement Earth Pressure and Stability of Slopes Foundations Settlement Due to Extraneous Causes Dams and Dam Foundations References Indexes
5,136 citations
Book•
01 Jan 1959
TL;DR: This book discusses the development of Uniform Flow and its applications, as well as the theory and analysis of open channel flow, and the design of channels for Uniform Flow.
Abstract: Chapter 1: Basic PrinciplesChapter 2: Open-Channel Flow and its ClassificationsChapter 3: Open Channels and Their PropertiesChapter 4: Energy and Momentum PrinciplesChapter 5: Critical Flow: Its Computation and ApplicationsChapter 6: Uniform FlowChapter 7: Development of Uniform Flow and Its FormulasChapter 8: Computation of Uniform FlowChapter 9: Design of Channels for Uniform FlowChapter 10: Theoretical Concepts of Boundary LayerChapter 11: Surface RoughnessChapter 12: Velocity Distribution and Instability of Uniform FlowChapter 13: Gradually Varied FlowChapter 14: Theory and AnalysisChapter 15: Methods of ComputationChapter 16: Practical ProblemsChapter 17: Spatially Varied FlowChapter 18: Rapidly Varied FlowChapter 19: Flow Over SpillwaysChapter 20: Hydraulic Jump and its Use as Energy DissipatorChapter 21: Flow in Channels of Non-Linear AlignmentChapter 22: Flow Through Nonprismatic Channel SectionsChapter 23: Unsteady FlowChapter 24: Gradually Varied Unsteady FlowChapter 25: Rapidly Varied Unsteady Flow Flood RoutingAppendices
5,013 citations
TL;DR: In this article, a large number of spherical grains of diameter D = 0.13 cm were sheared in Newtonian fluids of varying viscosity (water and a glycerine-water-alcohol mixture) in the annular space between two concentric drums.
Abstract: Dispersions of solid spherical grains of diameter D = 0.13cm were sheared in Newtonian fluids of varying viscosity (water and a glycerine-water-alcohol mixture) in the annular space between two concentric drums. The density σ of the grains was balanced against the density ρ of the fluid, giving a condition of no differential forces due to radial acceleration. The volume concentration C of the grains was varied between 62 and 13 %. A substantial radial dispersive pressure was found to be exerted between the grains. This was measured as an increase of static pressure in the inner stationary drum which had a deformable periphery. The torque on the inner drum was also measured. The dispersive pressure P was found to be proportional to a shear stress λ attributable to the presence of the grains. The linear grain concentration λ is defined as the ratio grain diameter/mean free dispersion distance and is related to C by λ = 1 ( C 0 / C ) 1 2 − 1 where C 0 is the maximum possible static volume concentration. Both the stresses T and P , as dimensionless groups T σ D 2 /λη 2 , and P σ D 2 /λη 2 , were found to bear single-valued empirical relations to a dimensionless shear strain group λ ½ σ D 2 (d U /d y )lη for all the values of λ C = 57% approx.) where d U /d y is the rate of shearing of the grains over one another, and η the fluid viscosity. This relation gives T α σ ( λ D ) 2 ( dU / dy ) 2 and T ∝ λ 1 2 η d U / dy according as d U /d y is large or small, i.e. according to whether grain inertia or fluid viscosity dominate. An alternative semi-empirical relation F = (1+λ)(1+½λ)ηd U /d y was found for the viscous case, when T is the whole shear stress. The ratio T/P was constant at 0·3 approx, in the inertia region, and at 0.75 approx, in the viscous region. The results are applied to a few hitherto unexplained natural phenomena.
2,445 citations
Journal Article•
TL;DR: In this article, a fairly complete range of slope movement processes are identified and classified according to features that are also to some degree relevant to their recognition, avoidance, control, or correction.
Abstract: A fairly complete range of slope movement processes are identified and classified according to features that are also to some degree relevant to their recognition, avoidance, control, or correction. The classification includes extremely slow distributed movements of both rock and soil (designated as creep in many classifications). The classification also includes the increasingly recognized overturning or toppling failures and spreading movements. Attention is also paid to movements due to freezing and thawing. Among the attributes that have been used as criteria for identification and classification are type of movement, kind of material, rate of movement, geometry of the area of failure and the resulting deposit, age, causes, degree of disruption of the displaced mass, relation or lack of relation of slide geometry to geologic structure, degree of development, geographic location of type examples, and state of activity. A discussion of the causes of sliding slope movements considers, factors that contribute to increased shear stress and factors that contribute low or reduced shear strength.
2,321 citations
TL;DR: In this paper, a new division of landslide materials is proposed, based on genetic and morphological aspects rather than arbitrary grain-size limits, which would allow the terms to be retained with their original meanings while making their application less ambiguous.
Abstract: As a result of the widespread use of the landslide classifications of Varnes (1978), and Hutchinson (1988), certain terms describing common types of flow-like mass movements have become entrenched in the language of engineering geology. Example terms include debris flow, debris avalanche and mudslide. Here, more precise definitions of the terms are proposed, which would allow the terms to be retained with their original meanings while making their application less ambiguous. A new division of landslide materials is proposed, based on genetic and morphological aspects rather than arbitrary grain-size limits. The basic material groups include sorted materials: gravel, sand, silt, and clay, unsorted materials: debris, earth and mud, peat and rock. Definitions are proposed for relatively slow non-liquefied sand or gravel flows, extremely rapid sand, silt or debris flow slides accompanied by liquefaction, clay flow slides involving extra-sensitive clays, peat flows, slow to rapid earth flows in nonsensitive plastic clays, debris flows which occur in steep established channels or gullies, mud flows considered as cohesive debris flows, debris floods involving massive sediment transport at limited discharges, debris avalanches which occur on open hill slopes and rock avalanches formed by large scale failures of bedrock.
984 citations