Assessment of Building Vulnerability with Varying Distances from Outlet Considering Impact Force of Debris Flow and Building Resistance

Studies have been conducted to understand the physical characteristics of debris flows and quantitatively assess the vulnerability of the buildings nearby to mitigate damage from debris flow disasters. However, there remains a paucity of research on vulnerability assessments that discuss the impact force of debris flow and building resistance within certain sections, where debris flows spread from an outlet. In this regard, the study assesses the vulnerability of buildings to debris flows while considering the distance from an outlet. For this purpose, it selects the two sites of Chuncheon-shi in Gangwon-do and Cheongju-shi in Chungcheongbuk-do in South Korea, which are widely known for having experienced debris flow damage in 2011 and 2017, respectively. For the sites, the study conducts an inverse analysis through debris flow simulation to understand the physical characteristics of debris flows, including flow depth, flow velocity, and impact force. Then, the study assesses vulnerability by estimating the resistance of the materials of the buildings placed in the range where debris flows spread, which allows the calculation of a vulnerability index that a building material may have and the estimation of a safety distance from the outlet for each material of the buildings in the study sites. The result shows that with an increasing distance from the outlet, the flow depth, velocity, and impact force, which represent debris flow properties, tend to decrease. This again results in vulnerability being gradually reduced. The study also suggests that buildings are exposed to the risk of debris flow disasters at a sections 40 to 60 m from an outlet for wood material construction, 70 to 110 m for brick-masonry material construction, and all sections from an outlet for prefabricated material construction. Based on this result, the vulnerability index is estimated for the wood material (0.85), brick-masonry material (0.58), and prefabricated material (0.003).

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The Effects of Upstream Flexible Barrier on the Debris Flow Entrainment and Impact Dynamics on a Terminal Barrier

Canadian Geotechnical Journal ◽

10.1139/cgj-2021-0119 ◽

2021 ◽

Author(s):

Hervé Vicari ◽

C.W.W. Ng ◽

Steinar Nordal ◽

Vikas Thakur ◽

W.A. Roanga K. De Silva ◽

...

Keyword(s):

Debris Flow ◽

Debris Flows ◽

Impact Force ◽

Dynamic Pressure ◽

Pressure Coefficient ◽

Flexible Barrier ◽

Impact Forces ◽

Flexible Barriers ◽

The Impact ◽

Bed Entrainment

The destructive nature of debris flows is mainly caused by flow bulking from entrainment of an erodible channel bed. To arrest these flows, multiple flexible barriers are commonly installed along the predicted flow path. Despite the importance of an erodible bed, its effects are generally ignored when designing barriers. In this study, three unique experiments were carried out in a 28 m-long flume to investigate the impact of a debris flow on both single and dual flexible barriers installed in a channel with a 6 m-long erodible soil bed. Initial debris volumes of 2.5 m3 and 6 m3 were modelled. For the test setting adopted, a small upstream flexible barrier before the erodible bed separates the flow into several surges via overflow. The smaller surges reduce bed entrainment by 70% and impact force on the terminal barrier by 94% compared to the case without an upstream flexible barrier. However, debris overflowing the deformed flexible upstream barrier induces a centrifugal force that results in a dynamic pressure coefficient that is up to 2.2 times higher than those recommended in guidelines. This suggests that although compact upstream flexible barriers can be effective for controlling bed entrainment, they should be carefully designed to withstand higher impact forces.

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Experimental Study of the Debris Flow Slurry Impact and Distribution

Shock and Vibration ◽

10.1155/2018/5460362 ◽

2018 ◽

Vol 2018 ◽

pp. 1-15 ◽

Cited By ~ 1

Author(s):

Haixin Zhao ◽

Lingkan Yao ◽

Yong You ◽

Baoliang Wang ◽

Cong Zhang

Keyword(s):

Debris Flow ◽

Debris Flows ◽

Impact Force ◽

Influence Factors ◽

Flume Experiment ◽

Middle Point ◽

Laboratory Flume ◽

Critical Issues ◽

Maximum Impact Force ◽

The Impact

In this study, we present a new method to calculate debris flow slurry impact and its distribution, which are critical issues for designing countermeasures against debris flows. There is no unified formula at present, and we usually design preventive engineering according to the uniform distribution of the maximum impact force. For conducting a laboratory flume experiment, we arrange sensors at different positions on a dam and analyze the differences on debris flow slurry impact against various densities, channel slopes, and dam front angles. Results show that the force of debris flow on the dam distributes unevenly, and that the impact force is large in the middle and decreases gradually to the both sides. We systematically analyze the influence factors for the calculation of the maximum impact force in the middle point and give the quantitative law of decay from the middle to the sides. We propose a method to calculate the distribution of the debris flow impact force on the whole section and provide a case to illustrate this method.

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Debris Flow Damage Assessment by Considering Debris Flow Direction and Direction Angle of Structure in South Korea

Water ◽

10.3390/w11020328 ◽

2019 ◽

Vol 11 (2) ◽

pp. 328 ◽

Cited By ~ 4

Author(s):

Dong Nam ◽

Man-Il Kim ◽

Dong Kang ◽

Byung Kim

Keyword(s):

South Korea ◽

Debris Flow ◽

Debris Flows ◽

Impact Force ◽

Mountainous Areas ◽

Mountainous Regions ◽

Impact Forces ◽

The Impact

Recently, human and property damages have often occurred due to various reasons—such as landslides, debris flow, and other sediment-related disasters—which are also caused by regional torrential rain resulting from climate change and reckless development of mountainous areas. Debris flows mainly occur in mountainous areas near urban living communities and often cause direct damages. In general, debris flows containing soil, rock fragments, and driftwood temporarily travel down to lower parts along with a mountain torrent. However, debris flows are also often reported to stream down from the point where a slope failure or a landslide occurs in a mountain directly to its lower parts. The impact of those debris flows is one of the main factors that cause serious damage to structures. To mitigate such damage of debris flows, a quantitative assessment of the impact force is thus required. Moreover, technologies to evaluate disaster prevention facilities and structures at disaster-prone regions are needed. This study developed two models to quantitatively analyze the damages caused by debris flows on structures: Type-1 model for calculating the impact force, which reflected the flow characteristics of debris flows and the Type-2 model, which calculated the impact force based on the topographical characteristics of mountainous regions. Using RAMMS a debris flow runoff model, the impact forces assessed through Type-1 and Type-2 models were compared to check reliability. Using the assessed impact forces, the damage ratio of the structures was calculated and the amount of damage caused by debris flows on the structures was ultimately assessed. The results showed that the Type-1 model overestimated the impact force by 10% and the Type-2 model by 4% for Mt. Umyeon in Seoul, compared to the RAMMS model. In addition, the Type-1 model overestimated the impact force by 3% and Type-2 by 2% for Mt. Majeok in Chuncheon, South Korea.

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Relationships between size and velocity for particles within debris flows

Canadian Geotechnical Journal ◽

10.1139/t08-088 ◽

2008 ◽

Vol 45 (12) ◽

pp. 1778-1783 ◽

Cited By ~ 5

Author(s):

Adam B. Prochaska ◽

Paul M. Santi ◽

Jerry D. Higgins

Keyword(s):

Particle Size ◽

Debris Flow ◽

Particle Velocity ◽

Video Analysis ◽

Debris Flows ◽

Impact Force ◽

Analysis Software ◽

Impact Forces ◽

The Impact ◽

Current Guidelines

Estimation of the impact forces from boulders within a debris flow is important for the design of structural mitigation elements. Boulder impact force equations are most sensitive to the inputs of particle size and particle velocity. Current guidelines recommend that a design boulder should have a size equal to the depth of flow and a velocity equal to that of the flow. This study used video analysis software to investigate the velocities of different sized particles within debris flows. Particle velocity generally decreased with increasing particle size, but the rate of decrease was found to be dependent on the abilities of particles to rearrange within debris flows.

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Deriving sediment transport information from debris-flow impact force signals

10.5194/egusphere-egu2020-13054 ◽

2020 ◽

Author(s):

Hui Tang ◽

Yan Yan ◽

Kaiheng Hu

Keyword(s):

Debris Flow ◽

Physical Model ◽

Ground Motion ◽

Debris Flows ◽

Impact Force ◽

Sediment Flux ◽

Seismic Ground Motion ◽

Inversion Model ◽

Force Signal ◽

The Impact

Runoff-generated debris flow has hazardous implications for downstream communities and infrastructure in alpine landscapes. Our understanding of fluid mechanisms of debris flows is very limited, in part, by a lack of direct observations and measurements. Seismic ground motion-based observations provide new constraints on debris flow physics, but it is still not widely applied due to the missing of validated inversion models for interpreting the impact force which generates seismic ground motion. Here we propose a physical model for the high-frequency spectral distribution of impact force signal generated by debris flows. Then we present a new inversion model based on the physical model for the impact force signal and apply this to the devastating debris flows in Dongchuang, China, on 25 August 2004. The amplitude and frequency characteristics of the impact force data can enable the estimation of grain size, sediment concentration, and sediment flux. Results suggest that in-situ data from three sensors could have provided a reconstruction of sediment flux profile in the vertical direction. Meanwhile, an inversion model designed for debris flows impact force would potentially provide hydrodynamics information as well.

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An experimental evaluation of impact force on a fiber bragg grating (FBG)-based device for debris flow warning

10.5194/egusphere-egu2020-134 ◽

2020 ◽

Author(s):

Shaojie Zhang

Keyword(s):

Debris Flow ◽

Fiber Bragg Grating ◽

Debris Flows ◽

Impact Force ◽

Dynamic Strain ◽

Bragg Grating ◽

New Device ◽

Impact Forces ◽

Measured Strain ◽

The Impact

Conventional sensors for debris flow monitoring suffer from several drawbacks including low service life, low reliability in long-distance data transfer, and stability in severe weather conditions. Recently, fiber Bragg grating (FBG)-based sensors have been developed to monitor debris flows. However, they can be easily damaged by the impact forces of boulders within debris flow. This paper presents a new FBG-based device to measure the strain induced by the impact force of debris flow with high reliability and effectiveness. The effects of the impact forces of debris flows have been investigated. Then, the relationship between the strain and the debris flow energy correlating with the damage to building structures has been established. It is shown that this new FBG-based device is capable of monitoring and warning about debris flows. The impact experiment results show that the peak value of dynamic strain on the fixed end of the new device is positively correlated with the external impact force. Using an impact force, we establish a relationship between the measured strain and the potential of a debris flow resulting in damage to structures was established. This follows the general rule that a larger measured strain corresponds to a higher level of debris flow. Using this relationship, we can quantify a dangerous level of debris flow using the monitored strain data. Our new device is capable of monitoring and warning about dangerous debris flows, allowing for more effective debris flow mitigation.

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Numerical study on debris flow in step-pools channel using smoothed particle hydrodynamics method

10.5194/egusphere-egu2020-2813 ◽

2020 ◽

Author(s):

Shuai Li ◽

Xiaoqing Chen ◽

Chong Peng ◽

Jiangang Chen

Keyword(s):

Debris Flow ◽

Smoothed Particle Hydrodynamics ◽

Debris Flows ◽

Impact Force ◽

Numerical Study ◽

Particle Hydrodynamics ◽

Smoothed Particle ◽

Smoothed Particle Hydrodynamics Method ◽

The Impact ◽

Peak Impact Force

Drainage channel with step-pool systems are widely used to control debris flow. However, the blocking of debris flow often gives rise to local damage at the steps and baffles. Hence, the estimation of impact force of debris flow is crucial for design step-pools channel. This paper presents a numerical study on the impact behavior of debris flows using SPH (Smoothed Particle Hydrodynamics) method. Some important parameters, such as the baffle shape (square, triangle, and trapezoid) and the densities of debris flows are considered to examine their influence on the impact force. The results show that the largest peak impact force is obtained at the second last baffle, rather than the first baffle. Moreover, the square baffle gives rise to the largest impact force whereas the triangle baffle bears the smallest one among the three baffles. Generally, the peak impact force increases with increasing the inflow density. However, a threshold density, beyond which the peak impact force will decrease, is suggested by the simulations. Based on the numerical results, an improved expression to predict the impact force considering the inclined angle of baffle is proposed.

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Numerical Simulation of Non-Homogeneous Viscous Debris-Flows Based on the Smoothed Particle Hydrodynamics (SPH) Method

Water ◽

10.3390/w11112314 ◽

2019 ◽

Vol 11 (11) ◽

pp. 2314 ◽

Cited By ~ 4

Author(s):

Shu Wang ◽

Anping Shu ◽

Matteo Rubinato ◽

Mengyao Wang ◽

Jiping Qin

Keyword(s):

Debris Flow ◽

Water Content ◽

Smoothed Particle Hydrodynamics ◽

Debris Flows ◽

Sph Method ◽

Particle Hydrodynamics ◽

Sph Model ◽

Smoothed Particle ◽

The Impact ◽

Kinetic And Potential Energies

Non-homogeneous viscous debris flows are characterized by high density, impact force and destructiveness, and the complexity of the materials they are made of. This has always made these flows challenging to simulate numerically, and to reproduce experimentally debris flow processes. In this study, the formation-movement process of non-homogeneous debris flow under three different soil configurations was simulated numerically by modifying the formulation of collision, friction, and yield stresses for the existing Smoothed Particle Hydrodynamics (SPH) method. The results obtained by applying this modification to the SPH model clearly demonstrated that the configuration where fine and coarse particles are fully mixed, with no specific layering, produces more fluctuations and instability of the debris flow. The kinetic and potential energies of the fluctuating particles calculated for each scenario have been shown to be affected by the water content by focusing on small local areas. Therefore, this study provides a better understanding and new insights regarding intermittent debris flows, and explains the impact of the water content on their formation and movement processes.

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Deciphering the seismic and normal-force fluctuation signatures of debris flows: an experimental assessment of the effects of flow composition and dynamics

10.5194/egusphere-egu21-2565 ◽

2021 ◽

Author(s):

Tjalling de Haas ◽

Amanda Aaberg ◽

Fabian Walter ◽

Zhen Zhang

Keyword(s):

Debris Flow ◽

Size Distribution ◽

Debris Flows ◽

Large Particle ◽

Normal Force ◽

Flow Volume ◽

Flow Depth ◽

Water Fraction ◽

Force Fluctuations ◽

Seismic Vibrations

Debris flows are gravity-driven mass movements that are common natural hazards in mountain regions worldwide. Previous work has shown that measurements of ground vibrations are capable of detecting the timing, speed, and location of landslides and debris flows. A remaining question is whether or not additional flow properties, such as grain-size distribution, flow depth, and impact stress can be inferred reliably from seismic data. Here, we experimentally explore the relation of seismic vibrations and normal-force fluctuations with debris-flow composition and dynamics. We show that seismic vibrations and normal-force fluctuations induced by debris flows are strongly correlated, and that both are strongly affected by debris-flow composition. We find that the effects of the large-particle distribution on seismic vibrations and normal-force fluctuations are substantially more pronounced than the effects of water fraction, clay fraction, and flow volume, especially when normalized by flow depth. We further show that for flows with similar coarse-particle distributions seismic vibrations and normal-force fluctuations can be reasonably-well related to flow depth, even if total flow volume, water fraction, and the size distribution of fines varies. Our experimental results shed light on how changes in large-particle, clay, and water fractions affect the seismic and force-fluctuation signatures of debris flows, and provide important guidelines for their interpretation.

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Alternative approach for works controlling stony debris flows

10.5194/egusphere-egu2020-4738 ◽

2020 ◽

Author(s):

Carlo Gregoretti ◽

Matteo Barbini ◽

Martino Bernard ◽

Mauro Boreggio

Keyword(s):

Debris Flow ◽

Debris Flows ◽

High Elevation ◽

Valley Bottom ◽

Check Dams ◽

Retention Basin ◽

Retention Basins ◽

Solid Liquid ◽

The Impact ◽

The Village

Many sites of the Dolomites are threatened by channelized debris flows: solid-liquid surges initiated by the entrainment of large quantities of sediments into the abundant runoff at the head of channel incised on fans, can dramatically increase their volume along the downstream routing. This is the case of the Rovina di Cancia site where solid-liquid surges forming in the upper part of the basin can increase their volume up and over 50000 m3, seriously impacting the downstream village of Borca di Cadore. The debris-flow channel ends just upstream the village that in the past was hit by four debris flows (three in the recent years) that caused victims and destructions. Control works built until now are not sufficient to protect the village from high magnitude debris flows and a definitive solution calls to be planned. Present works are a flat deposition area, 300 m downstream the initiation area, an open dam under construction downstream it, and &#160;two retention basins at the end of the channel. Between the open dam and the upstream retention basin, there are the rest of eight check-dams made of gabions, built in the 60s and progressively damaged or destroyed by the debris flows occurred after their construction. This series of check-dams limited the entrainment of solid material and the occurrence of localized scours. The initial plan is the substitution of the check-dams with concrete structures and the widening of the dowsntream retention basin through the raising of high elevation embankment downstream it and the following demolition of the actual dyke. Finally, a channel crossing the village and national route on the valley bottom will deliver the fluid phase from the widened basin to the Boite river. All these control works have a very high cost for construction and maintenance and severely impact the village with the presence of a non-negligible residual risk. These drawbacks call for an alternative solution that is searched looking at to the morphology. Downstream of the open dam and on its right side, there is a deep impluvium that ends on a large grass sloping area. The novel solution requires the construction of a channel through the right high bank that deviates the debris flow into the impluvium. The impluvium, widened through the excavation of the surrounding slopes, is closed at the outlet by &#160;an open dam. Downstream the open dam, a channel will lead to a retention basin, where most of storage volume is obtained from the excavation of the grass sloping area, limiting the elevation of the dykes At the end of this basin an open dam will deliver the debris-flow fluid part to a channel passing under the national route and joining the Boite river. Such a solution composed of a deviatory channel, two retention basins (the deep impluvium and that excavated on the sloping grass area) and the channels between and downstream them, has quite a lower costs of construction and maintenance, eliminating the impact on the village because occupying uninhabited areas without interrupting the main roads.

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