The Grain-Size Distribution of Rock-Avalanche Deposits: Implications for Natural Dam Stability

Dunning, Stuart; Armitage, Peter

doi:10.1007/978-3-642-04764-0_19

Cited by 63 publications

(72 citation statements)

References 19 publications

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“…Turcotte (1986) added that the fragmentation is often a scale invariant process, and the preexisting zones or planes of weakness where failure occurs exist on all scales. Crosta et al (2007) collecting data for the deposit of a rock avalanche indicated that its size distribution is characterized by a fractal dimension that was found consistent with other rock avalanche deposits (Dunning, 2006). Perfect (1997) discussed the use of the fractal theory and presented alternative models to analyze fragmentation in rock and soils.…”

Section: Characterizing the Fragmentation Degreementioning

confidence: 99%

A fractal fragmentation model for rockfalls

2016

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(150-250 words)The impact-induced rock mass fragmentation in a rockfall is analyzed by comparing the In Situ Block Size Distribution (IBSD) of the rock mass detached from the cliff face and the resultant Rockfall Block Size Distribution (RBSD) of the rockfall fragments on the slope. The analysis of several inventoried rockfall events suggests that the volumes of the rockfall fragments can be characterized by a power law distribution. We propose the application of a three-parameter Rockfall Fractal Fragmentation Model (RFFM) for the transformation of the IBSD into the RBSD. A Discrete Fracture Network model is used to simulate the discontinuity pattern of the detached rock mass and to generate the IBSD. Each block of the IBSD of the detached rock mass is an initiator. A survival rate is included to express the proportion of the unbroken blocks after the impact on the ground surface. The model was calibrated using the volume distribution of a rockfall event in Vilanova de Banat in the Cadí Sierra, Eastern Pyrenees, Spain. The RBSD was obtained directly in the field, by measuring the rock blocks fragments deposited on the slope. The IBSD and the RBSD were fitted by exponential and power-law functions, respectively. The results show that the proposed fractal model can successfully generate the RBSD from the IBSD and indicate the model parameter values for the case study.

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Section: Characterizing the Fragmentation Degreementioning

confidence: 99%

A fractal fragmentation model for rockfalls

2016

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“…Most landslide dams are highly heterogeneous along depth and along the run-out direction (Dunning, 2006;Crosta et al, 2007;Chang et al, 2009;Evans at al., 2007), which is a crucial factor in determining the failure time and outflow hydrograph (Costa and Schuster, 1988;Casagli et al, 2003). The capability of existing models to consider the variations in soil erodibility along depth has yet to be improved.…”

Section: Introductionmentioning

confidence: 99%

Simulation of the erosion process of landslide dams due to overtopping considering variations in soil erodibility along depth

Chang

Zhang

2010

Nat. Hazards Earth Syst. Sci.

180

103

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Abstract.A landslide dam typically comprises freshly deposited heterogeneous, unconsolidated or poorly consolidated earth materials and is vulnerable to overtopping breaching. A physically-based breach model is presented to simulate the breaching process of such landslide dams. The new model can predict the breach evolution, the erosion rate, and the outflow hydrograph. A spreadsheet is developed to numerically implement the model. The erosion processes of Tangjiashan Landslide Dam and Xiaogangjian Landslide Dam induced by the 2008 Wenchuan earthquake are analyzed using the new model. The erodibility of the two landslide dams varies significantly along depth. The predicted key breaching parameters (i.e., final breach size, failure time, and peak outflow rate) considering the variations in the soil erodibility along depth agree well with the observed values. Further sensitivity analysis indicates that the soil erodibility affects the breaching process of a landslide dam significantly. Higher soil erodibility will lead to a larger breach, a shorter failure time and a larger peak outflow rate. The erosion rate of the breach channel in the depth direction decreases with increasing erosion resistance of the landslide deposits. In the two case studies, the key breaching parameters cannot be properly predicted if constant soil erodibility parameters along depth are assumed.

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“…Landslide dams are generally composed of fragmented materials which have a wide range of sediment sizes (Costa and Schuster 1988;Schuster 1995;Davies and McSaveney 2011;Dunning and Armitage 2011). Reproducing field prototypes of landslide dams in a flume is challenging, especially with respect to downsizing the impoundment materials to laboratory-scale experiments.…”

Section: Methodsmentioning

confidence: 99%

“…Nevertheless, the study of sedimentological characteristics of natural river blockages is imperative for natural hazard assessment studies, as they have a major influence on the overall strength of dams, and control the rate of breach development (Fread 1988;Casagli et al 2003). Grain size distribution analysis has been used to study the internal structure of some landslide dams (Crosta et al 2006;Duman 2009;Dunning and Armitage 2011;Shugar and Clague 2011;Wang et al 2013). Field and laboratory analysis of textural characteristics of several landslide dam materials show that they are mostly poorly to very poorly sorted, matrix-or clast-supported, finely skewed, brecciated, stratified to massive sediments, are usually armored with angular boulders, and are sutured with a matrix of very fine materials (Weidinger 2006;Capra 2007Capra , 2011.…”

Section: Introductionmentioning

confidence: 99%

Hydromechanical constraints on piping failure of landslide dams: an experimental investigation

Okeke

Wang

2016

Geoenviron Disasters

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Background: Understanding the internal structure and material properties of landslide dams is essential for evaluating their potential failure mechanisms, especially by seepage and piping. Recent research has shown that the behaviour of landslide dams depends on the internal composition of the impoundment. We here present an experimental investigation of the hydromechanical constraints of landslide dam failure by piping. Experiments were conducted in a 2 m × 0.45 × 0.45 m flume, with a flume bed slope of 5°. Uniform dams of height 0.25 m were built with either mixed or homogeneous silica sands. Uniform-sized pebbles encased in a plastic mesh were used to initiate internal erosion. Two laser displacement sensors were used to monitor the behaviour of the dams during the internal erosion process while a linear displacement transducer and a water-level probe were deployed to monitor the onset of internal erosion and the hydrological trend of the upstream lake. Results: Five major phases of the breach evolution process were observed: pipe evolution, pipe enlargement, crest settlement, hydraulic fracturing and progressive sloughing. Two major failure modes were observed: seepage and piping-induced collapse. Majority of the dams composed of homogeneous material failed by seepage and downstream slope saturation, whereas dams built with mixed material failed by piping. Conclusions: We found that an increase in soil density and homogeneity of the dam materials reduced the potential to form a continuous piping hole through the dams. Furthermore, the potential for piping and progression of the piping hole through the dams increased with an increase in the percentage of fines and a decrease in hydraulic conductivity. The rate of pipe enlargement is related to the erodibility of the soil, which itself is inversely proportional to the soil density. This study provides new insights into the governing conditions and breach evolution mechanisms of landslide dams, as triggered by seepage and piping.

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The Grain-Size Distribution of Rock-Avalanche Deposits: Implications for Natural Dam Stability

Cited by 63 publications

References 19 publications

A fractal fragmentation model for rockfalls

A fractal fragmentation model for rockfalls

Simulation of the erosion process of landslide dams due to overtopping considering variations in soil erodibility along depth

Hydromechanical constraints on piping failure of landslide dams: an experimental investigation

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