scholarly journals Large‐Scale Experiments on Breaching Flow Slides and the Associated Turbidity Current

2020 ◽  
Vol 125 (10) ◽  
Author(s):  
Said Alhaddad ◽  
Robert Jan Labeur ◽  
Wim Uijttewaal
Keyword(s):  
Large Scale ◽  
Turbidity Current ◽  
Flow Slides

scholarly journals Modeling of Breaching-Generated Turbidity Currents Using Large Eddy Simulation

2020 ◽  
Vol 8 (9) ◽  
pp. 728
Author(s):  
Said Alhaddad ◽  
Lynyrd de Wit ◽  
Robert Jan Labeur ◽  
Wim Uijttewaal
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Large Eddy Simulation ◽  
Flow Characteristics ◽  
Turbidity Current ◽  
Turbidity Currents ◽  
Eddy Simulation ◽  
Failure Evolution ◽  
Large Eddy ◽  
Flow Slides

Breaching flow slides result in a turbidity current running over and directly interacting with the eroding, submarine slope surface, thereby promoting further sediment erosion. The investigation and understanding of this current are crucial, as it is the main parameter influencing the failure evolution and fate of sediment during the breaching phenomenon. In contrast to previous numerical studies dealing with this specific type of turbidity currents, we present a 3D numerical model that simulates the flow structure and hydrodynamics of breaching-generated turbidity currents. The turbulent behavior in the model is captured by large eddy simulation (LES). We present a set of numerical simulations that reproduce particular, previously published experimental results. Through these simulations, we show the validity, applicability, and advantage of the proposed numerical model for the investigation of the flow characteristics. The principal characteristics of the turbidity current are reproduced well, apart from the layer thickness. We also propose a breaching erosion model and validate it using the same series of experimental data. Quite good agreement is observed between the experimental data and the computed erosion rates. The numerical results confirm that breaching-generated turbidity currents are self-accelerating and indicate that they evolve in a self-similar manner.

Flow slide prediction method: influence of slope geometry

1998 ◽  
Vol 35 (1) ◽  
pp. 43-54 ◽  
Author(s):  
T P Stoutjesdijk ◽  
M B de Groot ◽  
J Lindenberg
Keyword(s):  
Large Scale ◽  
Prediction Method ◽  
Slope Instability ◽  
Initial Stresses ◽  
Triaxial Tests ◽  
Gradual Change ◽  
Loose Sand ◽  
Flow Slide ◽  
Flow Slides ◽  
Constitutive Properties

A quasi-two-dimensional method is presented for predicting liquefaction flow slides in a slope with saturated loose sand. The initial stresses at the start of the actual flow slide process are predicted assuming completely drained conditions during the gradual change in slope geometry caused by erosion or sedimentation. The condition for a flow slide is considered to be the presence of at least one sand element in a metastable stress state, i.e., a state in which the undrained response to any quick change in load, however small it may be, consists of a sudden large increase in pore pressure. The metastability of any sand element is predicted as a function of its constitutive properties, its location in the slope, and the slope geometry. The constitutive properties are derived from dry triaxial tests and basically describe the liquefiability (brittleness) of the sand. The metastability criterion for a soil element in a slope is different from that under triaxial loading. Flow slides observed in large-scale tests occurred at the conditions predicted with the model.Key words: loose sand, flow slides, liquefaction, collapse, slope instability.

A review of the classification of landslides of the flow type

2001 ◽  
Vol 7 (3) ◽  
pp. 221-238 ◽  
Author(s):  
Oldrich Hungr ◽  
S. G. Evans ◽  
M. J. Bovis ◽  
J. N. Hutchinson
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Large Scale ◽  
Debris Avalanche ◽  
Basic Material ◽  
Morphological Aspects ◽  
Flow Slides ◽  
Size Limits ◽  
Plastic Clays ◽  
Earth Flows

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.

Large-scale current-induced erosion and deposition in the path of the 1929 Grand Banks turbidity current

Sedimentology ◽  
1990 ◽  
Vol 37 (4) ◽  
pp. 613-629 ◽  
Author(s):  
JOHN E. HUGHES CLARKE ◽  
ALEXANDER N. SHOR ◽  
DAVID J. W. PIPER ◽  
LARRY A. MAYER
Keyword(s):  
Large Scale ◽  
Turbidity Current ◽  
Erosion And Deposition ◽  
Grand Banks

scholarly journals Breaching Flow Slides and the Associated Turbidity Current

2020 ◽  
Vol 8 (2) ◽  
pp. 67 ◽  
Author(s):  
Said Alhaddad ◽  
Robert Jan Labeur ◽  
Wim Uijttewaal
Keyword(s):  
Erosion Rate ◽  
Experimental Studies ◽  
Turbidity Current ◽  
Equation Model ◽  
Coupled Processes ◽  
Turbidity Currents ◽  
Flow Measurements ◽  
Sand Erosion ◽  
Erosion Models ◽  
Flow Slides

This paper starts with surveying the state-of-the-art knowledge of breaching flow slides, with an emphasis on the relevant fluid mechanics. The governing physical processes of breaching flow slides are explained. The paper highlights the important roles of the associated turbidity current and the frequent surficial slides in increasing the erosion rate of sediment. It also identifies the weaknesses of the current breaching erosion models. Then, the three-equation model of Parker et al. is utilised to describe the coupled processes of breaching and turbidity currents. For comparison’s sake, the existing breaching erosion models are considered: Breusers, Mastbergen and Van Den Berg, and Van Rhee. The sand erosion rate and hydrodynamics of the current vary substantially between the erosion models. Crucially, these erosion models do not account for the surficial slides, nor have they been validated due to the scarcity of data on the associated turbidity current. This paper motivates further experimental studies, including detailed flow measurements, to develop an advanced erosion model. This will improve the fidelity of numerical simulations.

scholarly journals Large-scale physical modelling of static liquefaction in gentle submarine slopes

Landslides ◽  
2021 ◽  
Author(s):  
Arash Maghsoudloo ◽  
Amin Askarinejad ◽  
Richard R. de Jager ◽  
Frans Molenkamp ◽  
Michael A. Hicks
Keyword(s):  
Large Scale ◽  
Numerical Models ◽  
Physical Modelling ◽  
Soil Mass ◽  
University Of Technology ◽  
Static Liquefaction ◽  
Physical Model Tests ◽  
Flow Slides ◽  
Soil Instability ◽  
Soil Responses

AbstractPlanning a monitoring campaign for a natural submarine slope prone to static liquefaction is a challenging task due to the sudden nature of flow slides. Therefore, gaining a better insight by monitoring the changes in pore pressure and acceleration of the soil mass, prior to and at the onset of static liquefaction, of submerged model slopes in the laboratory, helps in quantifying the minimum required triggering levels and ultimately the development of effective margins of safety for this specific failure mechanism. This study presents a set of physical model tests of submarine flow slides in the large-scale GeoTank (GT) of Delft University of Technology, in which a tilting mechanism was employed to trigger static liquefaction in loosely packed sand layers. Novel sensors were developed to locally monitor the hydro-mechanical soil responses acting as precursors of the onset of instability. The measurements indicated that soil instability can initiate at overly gentle slope angles (6–10°) and generate significant excess pore water pressures that intensify the deformations to form a flow slide. Moreover, it was observed that the onset of instability and its propagation are highly dependent on the rate of shear stress change and the state of the soil. The obtained data can be used for the future validation of numerical models for submarine flow slides.

A model for the runout analysis of rapid flow slides, debris flows, and avalanches

1995 ◽  
Vol 32 (4) ◽  
pp. 610-623 ◽  
Author(s):  
Oldrich Hungr
Keyword(s):  
Debris Flows ◽  
Large Scale ◽  
Mine Waste ◽  
Equations Of Motion ◽  
Basal Layer ◽  
Slide Mass ◽  
Debris Avalanches ◽  
Lagrangian Solution ◽  
Flow Slides ◽  
Waste Flow

Runout analyses are used for risk assessment and design of remedial measures against rapid landslides such as debris flows, debris avalanches, rockslide avalanches, large-scale liquefaction failures, and slides of fill and mining waste. A continuum model has been developed to simulate the characteristics of these phenomena. The model is based on a Lagrangian solution of the equations of motion and allows the selection of a variety of material rheologies, which can vary along the slide path or within the slide mass. It also allows for the internal rigidity of relatively coherent slide debris moving on a thin liquefied basal layer. The effects of lateral confinement are accounted for in a simplified manner. The model is shown to compare favourably with results of controlled laboratory experiments and other analytical tools for several different materials and problem configurations. Examples of the practical use of the model to predict the runout of coal mine waste flow slides and flows of liquefied granular tailings are presented. Key words : landslides, dynamic analysis, runout prediction, debris flows, debris avalanches, flow slides.

scholarly journals Watching the Beach Steadily Disappearing – the Evolution of Understanding of Retrogressive Breach Failures

2019 ◽  
Author(s):  
Dick R. Mastbergen ◽  
Konrad Beinssen ◽  
Yves Nédélec
Keyword(s):  
Large Scale ◽  
Active Phase ◽  
Small Scale ◽  
Tidal Channels ◽  
Defense Strategies ◽  
Video Footage ◽  
Flume Tests ◽  
Flow Slides ◽  
Large Scale Field ◽  
Coastal Flow

Retrogressive breach failures or coastal flow slides occur naturally in the shoreface in fine sands near dynamic tidal channels or rivers. They sometimes retrogress into beaches, shoal margins and river banks where they can threaten infrastructure and cause severe coastal erosion and flood risk. Ever since the first reports were published in the Netherlands over a century ago, attempts have been made to understand the geo-mechanical mechanism of flow slides. In this paper we have established that events, observed during the active phase, are characterized by a slow and steady retrogression into the shoreline, often continuing for many hours. This can be explained by the breaching mechanism, as elaborated in this paper. Recently, further evidence has become available in the form of video footage of active events in Australia and elsewhere, often publicly posted on the internet. All these observations justify the new term ‘retrogressive breach failure’ (RBF event). The mechanism has been confirmed in small-scale flume tests and in a large-scale field experiment. With a better understanding of the geo-mechanical mechanism, current protection methods can be better understood and new defense strategies can be envisaged. In writing this paper, we hope that the coastal science and engineering communities will better recognize and understand these intriguing natural events.

Some comments about observations and image processing of comet 29P/Schwassmann-Wachmann 1

1999 ◽  
Vol 173 ◽  
pp. 243-248
Author(s):  
D. Kubáček ◽  
A. Galád ◽  
A. Pravda
Keyword(s):  
Image Processing ◽  
Large Scale ◽  
Harvard College ◽  
Oak Ridge ◽  
Large Scale Structures ◽  
Short Period Comet ◽  
Short Period ◽  
Scale Structures ◽  
Harvard College Observatory ◽  
Period Comet

AbstractUnusual short-period comet 29P/Schwassmann-Wachmann 1 inspired many observers to explain its unpredictable outbursts. In this paper large scale structures and features from the inner part of the coma in time periods around outbursts are studied. CCD images were taken at Whipple Observatory, Mt. Hopkins, in 1989 and at Astronomical Observatory, Modra, from 1995 to 1998. Photographic plates of the comet were taken at Harvard College Observatory, Oak Ridge, from 1974 to 1982. The latter were digitized at first to apply the same techniques of image processing for optimizing the visibility of features in the coma during outbursts. Outbursts and coma structures show various shapes.

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