scholarly journals Analysis of the load exerted by debris flows on filter barriers: Comparison between numerical results and field measurements

2020 ◽  
Vol 118 ◽  
pp. 103311 ◽  
Author(s):  
Alessandro Leonardi ◽  
Marina Pirulli
Keyword(s):  
Debris Flows ◽  
Field Measurements ◽  
Numerical Results

scholarly journals Numerical simulation of drifting snow: erosion and deposition models

1998 ◽  
Vol 26 ◽  
pp. 191-196 ◽  
Author(s):  
Mohamed Naaim ◽  
Florence Naaim-Bouvet ◽  
Hugo Martinez
Keyword(s):  
Mass Exchange ◽  
Field Measurements ◽  
Numerical Results ◽  
Back Reaction ◽  
Erosion And Deposition ◽  
Deposition Model ◽  
Drifting Snow ◽  
Snow Fence ◽  
Flow Turbulence ◽  
Deposition Models

Earlier works on numerical modelling are analysed. Anderson and Haff (1991) proposed a model using the “splash” function which was defined for cohesionless sand. The Uematsu and others (1989, 1991) and Liston and others (1993,1994) approaches are based on fluid-mechanics conservation laws where the snow is transported and diffused by the air flow. These models consider the saltation layer as a boundary condition.For the flow, and for the suspension, we adopt the same model as that of Uematsu and Liston. For mass exchange between the flow and snow surface, we have developed an erosion–deposition model where mass exchange is defined in relation to flow turbulence, threshold-friction velocity and snow concentration. Our snow-erosion model was calibrated using Takeuchi's(1980) field measurements. The deposition model was tested by comparing numerical results with wind-tunnel ones, for sawdust-accumulation windward and leeward of a solid snow fence with a bottom gap. The numerical results obtained are close to the experimental results. The main results of the various sensitivity experiments are: the leeward accumulation is very sensitive to the ratio (u*/u*t) (it appears for (u*/u*t) close to 1 and disappears for (u*/u*t) > 1.2), the global accumulation produced by the fence increases as (u*/u*t) decreases and the back reaction of particles on turbulence extends slightly the windward accumulation.

scholarly journals Inundation, flow dynamics, and damage in the 9 January 2018 Montecito debris-flow event, California, USA: Opportunities and challenges for post-wildfire risk assessment

Geosphere ◽  
2019 ◽  
Vol 15 (4) ◽  
pp. 1140-1163 ◽  
Author(s):  
J.W. Kean ◽  
D.M. Staley ◽  
J.T. Lancaster ◽  
F.K. Rengers ◽  
B.J. Swanson ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Field Measurements ◽  
Economic Loss ◽  
Flow Dynamics ◽  
Dynamic Constraints ◽  
Fire Debris ◽  
Velocity Information ◽  
Intense Burst ◽  
Comprehensive Framework

Abstract Shortly before the beginning of the 2017–2018 winter rainy season, one of the largest fires in California (USA) history (Thomas fire) substantially increased the susceptibility of steep slopes in Santa Barbara and Ventura Counties to debris flows. On 9 January 2018, before the fire was fully contained, an intense burst of rain fell on the portion of the burn area above Montecito, California. The rainfall and associated runoff triggered a series of debris flows that mobilized ∼680,000 m3 of sediment (including boulders >6 m in diameter) at velocities up to 4 m/s down coalescing urbanized alluvial fans. The resulting destruction (including 23 fatalities, at least 167 injuries, and 408 damaged homes) underscores the need for improved understanding of debris-flow runout in the built environment, and the need for a comprehensive framework to assess the potential loss from debris flows following wildfire. We present observations of the inundation, debris-flow dynamics, and damage from the event. The data include field measurements of flow depth and deposit characteristics made within the first 12 days after the event (before ephemeral features of the deposits were lost to recovery operations); an inventory of building damage; estimates of flow velocity; information on flow timing; soil-hydrologic properties; and post-event imagery and lidar. Together, these data provide rare spatial and dynamic constraints for testing debris-flow runout models, which are needed for advancing post-fire debris-flow hazard assessments. Our analysis also outlines a framework for translating the results of these models into estimates of economic loss based on an adaptation of the U.S. Federal Emergency Management Agency’s Hazus model for tsunamis.

Predicting deposition of debris flows in mountain channels

1990 ◽  
Vol 27 (4) ◽  
pp. 409-417 ◽  
Author(s):  
Lee E. Benda ◽  
Terrance W. Cundy
Keyword(s):  
Pacific Northwest ◽  
Debris Flows ◽  
Field Measurements ◽  
Coast Range ◽  
Oregon Coast Range ◽  
Oregon Coast ◽  
Aerial Photos ◽  
The Pacific ◽  
Channel Slope ◽  
Junction Angle

An empirical model for predicting deposition of coarse-textured debris flows in confined mountain channels is developed based on field measurements of 14 debris flows in the Pacific Northwest, U.S.A. The model uses two criteria for deposition: channel slope (less than 3.5°) and tributary junction angle (greater than 70°). The model is tested by predicting travel distances of 15 debris flows in the Oregon Coast Range and six debris flows in the Washington Cascades, U.S.A. The model is further tested on 44 debris flows in two lithological types in the Oregon Coast Range using aerial photos and topographic maps; on these flows only the approximate travel distance is known. The model can be used by resource professionals to identify the potential for impacts from debris flows. Key words: debris flow, deposition, travel, erosion.

The Numerical Analysis and Field Measurements of the Shield Tunnel Passing through the Pipeline Groups

2012 ◽  
Vol 226-228 ◽  
pp. 1488-1494
Author(s):  
Guan Shui Liu ◽  
Lian Wei Sun ◽  
Bo Wang ◽  
Shi Ming Wu ◽  
Cheng Po Hong ◽  
...  
Keyword(s):  
Finite Element ◽  
Numerical Analysis ◽  
Numerical Model ◽  
Water Pressure ◽  
Large Diameter ◽  
Field Measurements ◽  
Numerical Results ◽  
Shield Tunnel ◽  
Sewer Pipes

In this work, research was carried out based on the shield tunnel of metro line 1 in Hangzhou. The construction of this tunnel beneath the sewage pipelines, which have large diameter with water pressure. The project studied in this treatise is relatively rare in China in terms of sewer pipes, the number of sewers, spacing between shield and sewers and the crossing times. A numerical model was established to analyze the construction of metro across the sewage pipelines with water pressure, taking the interactions between tunnel, pipelines and soil into account. The stress of pipelines, settlement of pipelines and ground during the crossing process were calculated. The finite element results were compared with measured results to verify the reliability of numerical results. Some meaningful results were achieved.

Debris flows: some physical characteristics and behaviour

1993 ◽  
Vol 30 (1) ◽  
pp. 71-81 ◽  
Author(s):  
R. J. Fannin ◽  
T. P. Rollerson
Keyword(s):  
Debris Flows ◽  
Slope Angle ◽  
Field Measurements ◽  
Cohesive Soil ◽  
Study Data ◽  
Physical Characteristics ◽  
Infinite Slope ◽  
Queen Charlotte Islands ◽  
Morphological Criteria ◽  
Field Drainage

Field observations on 449 debris flows in the Queen Charlotte Islands, British Columbia, are summarized. Movement of debris is classified according to seven characteristic types designated for the purposes of the study. Data on the physical characteristics of the events are presented. An analysis of the data is made with reference to event initiation, yield, and deposition using both mechanistic and morphological criteria. For those events which initiate on an open slope, the infinite slope model is used to establish a relationship between field drainage class and slope angle, for assumed frictional and cohesive soil strength parameters. The field drainage classes are directly related to the postulated location of the groundwater surface within the depth of the rupture plane. Deposition of channelized events is found to be influenced by the ratio of channel width to channel gradient, with the onset of deposition expected when the ratio exceeds unity. Five classes of depositional area are proposed. The magnitude of debris material deposited by an event is described by a channel debris yield rate which shows considerable variation with each event type. The conclusions of this study are based on postevent field measurements of deposited and eroded debris material. A limitation of the study arises from the difficulty of accurately describing an event some years after it has taken place. Key words : slope stability, debris flow, infinite slope analysis, debris yield.

scholarly journals Meteorological factors driving glacial till variation and the associated periglacial debris flows in Tianmo Valley, south-eastern Tibetan Plateau

2017 ◽  
Vol 17 (3) ◽  
pp. 345-356 ◽  
Author(s):  
Mingfeng Deng ◽  
Ningsheng Chen ◽  
Mei Liu
Keyword(s):  
Tibetan Plateau ◽  
Debris Flow ◽  
Air Temperature ◽  
Debris Flows ◽  
Large Scale ◽  
Field Measurements ◽  
Glacial Till ◽  
Eastern Tibetan Plateau ◽  
South Eastern ◽  
Air Temperatures

Abstract. Meteorological studies have indicated that high alpine environments are strongly affected by climate warming, and periglacial debris flows are frequent in deglaciated regions. The combination of rainfall and air temperature controls the initiation of periglacial debris flows, and the addition of meltwater due to higher air temperatures enhances the complexity of the triggering mechanism compared to that of storm-induced debris flows. On the south-eastern Tibetan Plateau, where temperate glaciers are widely distributed, numerous periglacial debris flows have occurred over the past 100 years, but none occurred in the Tianmo watershed until 2007. In 2007 and 2010, three large-scale debris flows occurred in the Tianmo Valley. In this study, these three debris flow events were chosen to analyse the impacts of the annual meteorological conditions, including the antecedent air temperature and meteorological triggers. The remote sensing images and field measurements of the adjacent glacier suggested that sharp glacier retreats occurred in the 1 to 2 years preceding the events, which coincided with spikes in the mean annual air temperature. Glacial till changes providing enough active sediment driven by a prolonged increase in the air temperature are a prerequisite of periglacial debris flows. Different factors can trigger periglacial debris flows, and they may include high-intensity rainfall, as in the first and third debris flows, or continuous, long-term increases in air temperature, as in the second debris flow event.

scholarly journals Numerical Modeling of Infrasound Energy Radiation by Debris Flow Events

2021 ◽  
Author(s):  
M. Coco ◽  
E. Marchetti ◽  
O. Morandi
Keyword(s):  
Numerical Modeling ◽  
Debris Flow ◽  
Early Warning ◽  
Debris Flows ◽  
Flow Characteristics ◽  
Early Warning Systems ◽  
Numerical Results ◽  
Warning Systems ◽  
Simulation Code ◽  
Energy Radiation

AbstractDebris flows constitute a severe natural hazard in Alpine regions. Studies are performed to understand the event predictability and to identify early warning systems and procedures. These are based both on sensors deployed along the channels or on the amplitude of seismic and infrasound waves radiated by the flow and recorded far away. Despite being very promising, infrasound cannot be used to infer the source characteristics due to the lack of a physical model of the infrasound energy radiated by debris flows. Here the simulation of water flow along a simple channel is presented, experiencing the fall from a dam, performed within the open source simulation code OpenFOAM. The pressure perturbation within the atmosphere produced by the flow is extracted and the infrasound signature of the events as a function of the flow characteristics is defined. Numerical results suggest that infrasound is radiated immediately downstream of the dam with amplitude and period that scale with dam height and water level. Modeled infrasound waveform is interpreted as being produced mostly by waves at the water free surface developing downstream of the dam. Despite the effect of sediments is not considered in this first study and will be implemented in future investigations, numerical results obtained with this simple model are in general agreement with experimental results obtained from array analysis of infrasound data recorded at Illgraben, Switzerland. Results highlight how numerical modeling can provide critical information to define a source mechanism of infrasound energy radiation by debris-flow, that is required also to improve early warning systems.

scholarly journals Field Measurements of Debris Flows in the Mizunashi and Nakao Rivers on Mt Unzen-Hugen Dake.

1999 ◽  
pp. 49-65 ◽  
Author(s):  
Muneo HIRANO ◽  
Haruyuki HASHIMOTO ◽  
Michinari KOUNO ◽  
Kunihiko ONDA ◽  
Kichan PARK
Keyword(s):  
Debris Flows ◽  
Field Measurements

Numerical Simulation of Debris Flows

2009 ◽  
Author(s):  
Ko-Fei Liu ◽  
Ming-Chun Huang
Keyword(s):  
Debris Flows ◽  
Plug Flow ◽  
Field Measurements ◽  
Bottom Layer ◽  
Field Application ◽  
Constitutive Law ◽  
Central Difference ◽  
Order Scheme ◽  
Complicated Geometry ◽  
Numerical Program

A numerical program developed for field application is presented in this paper. We use the generalized Julien and Lan (1991) rheological model to simulate debris flows. Due to the derivative discontinuous nature of the constitutive law, flow is separated into plug region and bottom region (with stress greater than yield stress). The program solves the plug flow layer solution first and then corrects the solution with the bottom layer approximation. Numerical scheme with upwind method and central difference in space and Adam-Bashforth 3rd order scheme in time is used for both layers. The scheme is tested against analytical solutions and laboratory experiments with very good results. Application to a field case with more complicated geometry, also achieves good agreement with error less than 5% compared with field measurements. Final example demonstrates how this numerical program is used in a preliminary design.

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