scholarly journals Debris Flow Behavioral Characteristic Based on Rheological Properties: A Case Study on Mt. Hwangnyeong and Mt. Umyeon

2020 ◽  
Vol 20 (4) ◽  
pp. 75-85
Author(s):  
Hyeong-Jin Kim ◽  
Yun-Tae Kim
Keyword(s):  
Debris Flow ◽  
Rheological Properties ◽  
Yield Stress ◽  
Flow Behavior ◽  
Front Velocity ◽  
Small Scale ◽  
Flume Experiments ◽  
Fine Content ◽  
Runout Distance ◽  
Rate Of Increase

Debris flow, one of the major natural disasters in Korea, usually occurs because of heavy rainfall during the rainy season. Recently in Korea, rainfall, as well as the frequency of debris flow, has continually increased as a result of climate change. Therefore, it is necessary to study the characteristics of the debris flow behavior for hazard mitigation and damage assessment. In this study, vane-type rheometer tests were conducted to estimate the rheological properties (viscosity, yield stress) of two soil samples collected from Mt. Hwangnyeong and Mt. Umyeon Several series of small-scale flume experiments were also performed to evaluate the characteristics of the debris flow behaviors (flow velocity, runout distance, and deposition volume) of these two sites. The results of the experiments show that front velocity, runout distance, and deposition volume of the debris flow gradually decrease with increase in viscosity and yield stress. Especially in the case of the Mt. Hwangnyeong sample, which has a high fine content, experimental results showed that the rate of increase in front velocity, runout distance, and deposition volume tended to high as viscosity and yield stress decreased compared to Mt. Umyeon.

A Study of Debris Flow Behaviors According to Rheometer Properties: Focused on the Hwangnyeong Mt. and Umyeon Mt.

2020 ◽  
Author(s):  
Hyeong-Jin Kim ◽  
Dae-Ho Yun ◽  
Yun-Tae Kim
Keyword(s):  
Debris Flow ◽  
Rheological Properties ◽  
Yield Stress ◽  
Flow Behavior ◽  
Front Velocity ◽  
Experimental Results ◽  
Small Scale ◽  
Water Mixture ◽  
Runout Distance ◽  
Two Samples

<p>A debris flow, a mass movement of soil and water mixture, is generally occurred by heavy rainfall during the rainy season in Korea. Because of climate change, the amount and frequency of rainfall has continually increased these days. Populated areas located in debris flow-prone mountainous areas are commonly subject to debris flow hazards. For this reason, it is necessary to analyze the characteristics of the debris flow behavior for the hazard mitigation. In this study, for two samples from Hwangnyeong Mt. and Umyeon Mt. in Korea, the vane-type rheometer test were performed to estimate the rheological property such as viscosity and yield stress and small-scale flume experiment was carried out to evaluate the characteristics of debris flow behaviors such as front velocity, runout distance and deposition volume. From the experimental results, rheological properties decrease with decreasing volumetric sediment concentration, and debris flow behavior gradually increased with decreasing rheological properties in the experiment. Additionally, in case of Hwangnyeong Mt. which has a high silt and clay fraction, the experimental results show that the amount of the front velocity, runout distance and deposition volume tend to increase higher than Umyeon Mt. as viscosity and yield stress decreased.</p>

scholarly journals Rheological properties of loose sands subjected to upward flow

2017 ◽  
Vol 54 (5) ◽  
pp. 664-673 ◽  
Author(s):  
Hyo Sub Kang ◽  
Yun Tae Kim
Keyword(s):  
Shear Rate ◽  
Debris Flow ◽  
Rheological Properties ◽  
Yield Stress ◽  
Flow Behavior ◽  
Fluid Pressure ◽  
Hydraulic Gradient ◽  
Flow Index ◽  
Loose Sand ◽  
Upward Flow

The objective of this study was to investigate the rheological properties of loose sands subjected to upward flow by using a vane-type rheometer that controlled upward flow in the loose sand specimens. Various hydraulic gradients (i.e., i = 0–2.0) were applied to loose sands. The rheological properties of the loose sands, such as yield stress and viscosity, were determined based on the Bingham and Herschel–Bulkley models. The experimental results showed that the flow behavior of loose sand samples exhibited a shear thickening when the Herschel–Bulkley model was applied (i.e., nondimensional flow index n > 1) and exhibited a Bingham-like within a limited shear rate range (i.e., 1∼30 1/s). The latter is clearly shown for a relatively high shear rate. As the hydraulic gradient was increased, the flow characteristics were close to the Bingham fluid. Yield stress showed a tendency to decrease linearly as hydraulic gradient was increased. However, the viscosity of the loose sands maintained a constant value irrespective of hydraulic gradient. The test results indicated that the pore fluid pressure resulting from upward flow in a soil sample affects yield stress, which contributes to the initiation of debris flow mobilization. As a result, it was possible to estimate the rheological properties of soil at the condition of liquefaction (critical hydraulic gradient), or initial occurrence of debris flow.

scholarly journals Effect of Ground Conditions and Mesh Size of Net-type Barrier on Debris Flow Behavior

2021 ◽  
Vol 21 (1) ◽  
pp. 101-110
Author(s):  
Hyeong-Jin Kim ◽  
Ji-Sung Lee ◽  
Yun-Tae Kim
Keyword(s):  
Experimental Study ◽  
Debris Flow ◽  
Debris Flows ◽  
Heavy Rainfall ◽  
Flow Behavior ◽  
Mesh Size ◽  
Front Velocity ◽  
Fine Content ◽  
Mountain Valley ◽  
Ground Conditions

Debris flow is a type of landslide that occurs mainly in mountain valley areas during heavy rainfall. Various types of barriers have been installed in South Korea to reduce the damage caused by debris flows. However, there is no reasonable design standard when installing the barrier, and an experimental study for the performance evaluation of barriers is insufficient. In this study, the performance of the net-type barrier was evaluated by analyzing the effect of the ground conditions and mesh size of the net-type barrier on the debris flow behavior by reducing the front velocity and deposition volume. As a result, for areas with less fine content, the efficiency of the net-type barrier increased as the mesh size of the net-type barrier decreased. Accordingly, the ground conditions and mesh size of the net-type barrier significantly influence the performance of the net-type barrier. The damage caused by debris flow can be sufficiently reduced through the reasonable design of a net-type barrier.

Variation of uplift pressure of debris flow on the dam bottom

2020 ◽  
Author(s):  
Xingzhang Chen ◽  
Hui Chen
Keyword(s):  
Debris Flow ◽  
Time Lag ◽  
Temporal Variations ◽  
Flow Density ◽  
Flume Experiments ◽  
Fine Content ◽  
Dam Foundation ◽  
Uplift Pressure ◽  
Average Value ◽  
The Stability

<p>Abstract: Uplift pressure is crucial for the stability of debris flow dam because of its reducing the effective pressure on the dam foundation and the anti-slide force of the dam. This study investigates the spatial and temporal variations of the uplift pressures during the debris flow impact processes, through a series of flume experiments. Before the debris flow impacting on the dam, the uplift pressure keeps stable due to the steady water level, and then it decreases slightly at the instant of debris flow impacting on the dam which lasts for no more than 1 s, and then increases sharply within a time lag no more than 2 s, and then decreases sharply soon afterwards. The maximal increasing ratio is 6.4 and the average value is 3, comparing with the uplift pressure before the impacting. The peak pressure occurs before the dam and decreases with the distance from the dam with a nearly linear tendency. The increment of uplift pressure also presents a similar tendency with the distance from the dam. In addition, the uplift pressure is found to be strongly influenced by the permeability of debris flow deposits, especially by the fine content of grain composition, and by the properties of the flow, such as the flow density, runoff volume and hydraulic gradient, and the pressure rises in a nearly linear form with the properties.</p><p>Keywords: debris flow, uplift pressure, check dam, flume experiments</p>

scholarly journals Comparison of measurement methods of the front velocity of small-scale debris flows

2015 ◽  
Vol 46 (4) ◽  
pp. 129 ◽  
Author(s):  
Francesco Bettella ◽  
Gian Battista Bischetti ◽  
Vincenzo D'Agostino ◽  
Simone Virginio Marai ◽  
Enrico Ferrari ◽  
...  
Keyword(s):  
Debris Flow ◽  
High Speed ◽  
Video Camera ◽  
Significant Loss ◽  
Front Velocity ◽  
Small Scale ◽  
Mean Flow ◽  
Digital Video Camera ◽  
Transport Zone ◽  
Kinematic Behaviour

Debris flow is a gravity-driven process, which is characterized by a travelling dense surge including large boulders, and it is followed by a more fluid tail. These characteristics make difficult the measurement of the mean flow velocity by means of common hydraulic techniques. Different methods can be used at real scale and small-scale to measure the front velocity but a dedicate comparison between available methods is still lacking. This research aims to compare the front velocity measurements in the transport zone of a miniature debris flow using three devices: i) a common digital video camera (29 frames per second); ii) a high speed thermo camera (60 fps); and iii) a laser photoelectric sensors system. The statistical analysis of data has highlighted no significant differences exist between front velocities obtained by means of the video camera and the thermo camera, whereas photocells data statistically differ from those achieved via the other systems. Some lack of data recorded by photocell was documented, while the thermo camera technique did not show significant loss of information being also helpful to detect the kinematic behaviour of single particles. Finally, the tests confirmed the influence of the solid volumetric concentration in the debris-flow mechanics, which promotes, <em>ceteris</em> <em>paribus</em>, the debris-flow slowing down.

scholarly journals EDDA 1.0: integrated simulation of debris flow erosion, deposition and property changes

2015 ◽  
Vol 8 (3) ◽  
pp. 829-844 ◽  
Author(s):  
H. X. Chen ◽  
L. M. Zhang
Keyword(s):  
Debris Flow ◽  
Yield Stress ◽  
Water Flow ◽  
Large Scale ◽  
Limit Equilibrium ◽  
Flow Density ◽  
Catchment Scale ◽  
Flow Process ◽  
Runout Distance ◽  
Property Changes

Abstract. Debris flow material properties change during the initiation, transportation and deposition processes, which influences the runout characteristics of the debris flow. A quasi-three-dimensional depth-integrated numerical model, EDDA (Erosion–Deposition Debris flow Analysis), is presented in this paper to simulate debris flow erosion, deposition and induced material property changes. The model considers changes in debris flow density, yield stress and dynamic viscosity during the flow process. The yield stress of the debris flow mixture determined at limit equilibrium using the Mohr–Coulomb equation is applicable to clear water flow, hyper-concentrated flow and fully developed debris flow. To assure numerical stability and computational efficiency at the same time, an adaptive time stepping algorithm is developed to solve the governing differential equations. Four numerical tests are conducted to validate the model. The first two tests involve a one-dimensional debris flow with constant properties and a two-dimensional dam-break water flow. The last two tests involve erosion and deposition, and the movement of multi-directional debris flows. The changes in debris flow mass and properties due to either erosion or deposition are shown to affect the runout characteristics significantly. The model is also applied to simulate a large-scale debris flow in Xiaojiagou Ravine to test the performance of the model in catchment-scale simulations. The results suggest that the model estimates well the volume, inundated area, and runout distance of the debris flow. The model is intended for use as a module in a real-time debris flow warning system.

scholarly journals MACROMOLECULAR AND AROMATIC CHARACTER INFLUENCE OF SBR ON THE RHEOLOGICAL PROPERTIES OF WELL CEMENT SLURRIES

2018 ◽  
Vol 1 (1) ◽  
pp. 21-27
Author(s):  
Mostafa Aboelkheira ◽  
Celeste Siqueira ◽  
Fernando Souza Jr. ◽  
Romildo Toledo
Keyword(s):  
Rheological Properties ◽  
Yield Stress ◽  
Flow Behavior ◽  
Free Water ◽  
Plastic Viscosity ◽  
Hydration Process ◽  
Cement Particle ◽  
Newtonian Flow ◽  
Aromatic Character ◽  
Well Cement

Ensuring the rheological properties of the latex-based cement slurries in steam EOR is indispensable. Ca(OH)2 is produced after cement/water reaction and the macromolecules tend to disturb the hydration process, after the latex demulsification, by covering the cement particle. The free water decreases due to the high hydrophilicity of demulsified SBR, where final gel values increased up to 67%. The slump diameter was decreased exponentially by increasing the latex content limiting the workability. SBR-modified slurries presented a Pseudoplastic non-Newtonian flow behavior and the plastic viscosity decreases gradually, while the yield stress values registered a progressive increment by adding SBR till 10%.

Debris flow impact on a flexible barrier: laboratory flume experiments and force-based mechanical model validation

2021 ◽  
Vol 106 (1) ◽  
pp. 735-756
Author(s):  
R. Brighenti ◽  
L. Spaggiari ◽  
A. Segalini ◽  
R. Savi ◽  
G. Capparelli
Keyword(s):  
Debris Flow ◽  
Model Validation ◽  
Mechanical Model ◽  
Flume Experiments ◽  
Flexible Barrier ◽  
Laboratory Flume

scholarly journals Influence of biopolymers on the rheological properties of seafloor sediments and the runout behavior of submarine debris flows

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jun Kameda ◽  
Hamada Yohei
Keyword(s):  
Rheological Properties ◽  
Debris Flows ◽  
Extracellular Polymeric Substances ◽  
Flow Behavior ◽  
Mass Movement ◽  
Rheological Parameters ◽  
Natural Environments ◽  
Natural Systems ◽  
Chemical Conditions ◽  
Seafloor Sediments

AbstractSubmarine debris flows are mass movement processes on the seafloor, and are geohazards for seafloor infrastructure such as pipelines, communication cables, and submarine structures. Understanding the generation and run-out behavior of submarine debris flows is thus critical for assessing the risk of such geohazards. The rheological properties of seafloor sediments are governed by factors including sediment composition, grain size, water content, and physico-chemical conditions. In addition, extracellular polymeric substances (EPS) generated by microorganisms can affect rheological properties in natural systems. Here we show that a small quantity of EPS (~ 0.1 wt%) can potentially increase slope stability and decrease the mobility of submarine debris flows by increasing the internal cohesion of seafloor sediment. Our experiments demonstrated that the flow behavior of sediment suspensions mixed with an analogue material of EPS (xanthan gum) can be described by a Herschel–Bulkley model, with the rheological parameters being modified progressively, but not monotonously, with increasing EPS content. Numerical modeling of debris flows demonstrated that the run-out distance markedly decreases if even 0.1 wt% of EPS is added. The addition of EPS can also enhance the resistivity of sediment to fluidization triggered by cyclic loading, by means of formation of an EPS network that binds sediment particles. These findings suggest that the presence of EPS in natural environments reduces the likelihood of submarine geohazards.

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