• Journal of the Korean GEO-environmental Society
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• v.22 no.2
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• pp.25-33
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• 2021

This study was conducted to understand the deposition characteristics of debris flow and to analyze the reduction effect of debris flow damage by installing a berm. Flume experiments were performed in consideration of various channel slope and volumetric sediment concontration. In order to analyze the reduction effect of debris flow damage by installing a berm, the cases of not installing a berm and the cases of installing a berm were compared. In this study, the runout distance, total travel distance, and mobility ratio were analyzed among the deposition characteristics of debris flow. First, the deposition characteristics of debris flow according to the change of the channel slope were analyzed, and the deposition characteristics of debris flow due to the change of volumetric sediment concentration were analyzed. In addition, the change rate of debris flow deposition characteristics when a berm was installed was calculated based on the case when a berm was not installed. As a result of the experiments, it was confirmed that the channel slope and volumetric sediment concentration had a significant effect on the deposition characteristics of debris flow. In addition, when a berm is installed on the slope, the runout distance and mobility ratio of debris flow are greatly decreased, and the total travel distance is increased. This means that installing a berm delays the movement of debris flow and reduces the potential mobility of debris flow. The results of this study will provide useful information for understanding the deposition characteristics of debris flow. Furthermore, it is expected to help in the design of a berm.

• Journal of Korean Society of Water and Wastewater
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• v.34 no.1
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• pp.45-52
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• 2020

Even though sewers have been conventionally designed to prevent from sediment deposition using a specified minimum velocity or shear stress at a particular depth of flow or with a particular frequency of occurrence, it was appreciated that these methods do not consider the characteristics and concentration of the sediment and the specific hydraulic conditions of the sewer with sediment. In this study, a densimetric Froude number formula was suggested considering particle diameter and volumetric concentration of the sediment as well as flow depth and flowrate, based on several domestic field inspections, which was compared with other formulas proposed by previous investigators. When the sediment concentration was not considered, the calibration coefficient of 0.125-1.5 to the densimetric Froude numbers of this study was needed to obtain the similar ones with previous investigators'. For the densimetric Froude number formula obtained with consideration of sediment concentration, the exponent value of term C_v was almost the same as that of previous results and that of d₅₀/R_h was similar for F_r < 2.2.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.235-245
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• 2021

Recently, the frequency of torrential rain is increasing due to climate change, which causes a large amount of debris flows. The purpose of this study was to understand the flow characteristics of debris flow according to the change in channel slope and volumetric sediment concentration and to analyze the effects of a berm on the flow characteristics of debris flow. The flow characteristics of debris flow, such as flow velocity, flow depth, Froude number, and flow resistance coefficients, were calculated using laboratory tests. The effect of a berm was analyzed by comparing the experimental results of a linear channel with those of a one-stepped channel. The results showed that the channel slope affected the flow velocity and flow depth, and the volumetric sediment concentration affected the flow velocity and flow depth, Froude number, and flow resistance coefficient. Moreover, as a berm was installed, the flow velocity and flow depth decreased by up to 26.1% and 71.2%, respectively. This means that installing a berm reduces the flow velocity, thereby reducing the mobility and kinetic energy. These results provide useful information to understand better the flow characteristics of debris flow and the effectiveness of a berm.

• Korean Journal of Ecology and Environment
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• v.34 no.4 s.96
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• pp.342-348
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• 2001

The present work is to introduce the preliminary experimental results for a primary hydrocyclones process in lake sediment thickening. A few cyclones based on the Rietema standard geometry were prepared. The test particles were sediments from a local lake and waste coal fly ash for a reference test. As a result of the chemical analysis, organic contaminants were abundantly found in smaller particles in overflow. Experimental results showed that the physical characteristics of particles, configuration of the cyclone and operating variables including feed solids concentration and volumetric flow rate could affect the separation efficiency. The limiting feeding velocity for the separation and enrichment of particles was 1.5 m/s, higher separation efficiency, in general, was obtained under the high velocity with the small cyclones.

• Microbiology and Biotechnology Letters
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• v.50 no.4
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• pp.557-562
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• 2022

In this study we evaluated biohydrogen production potential as operational parameters (substrate, salt concentration, and temperature) using eight inoculum sources. While the volumetric biohydrogen production rate was significantly affected by temperature and inoculum sources, substrate and salt concentration did not have a significant effect on the biohydrogen production. Mesophilic temperature (37℃) was also found more appropriate for the hydrogen production than thermophilic temperature (50℃). Rate, while the eight inoculum sources, anaerobic digestion sludge exhibited the fastest biohydrogen production. The maximum production rate from anaerobic digestion sludge was 2,729 and 1,385 ml-H₂·l^-1·d^-1 at mesophilic and thermophilic temperature, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.4
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• pp.1227-1240
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• 2014

Abandoned mines often cause environmental problems, such as alteration of landscape, metal contamination, and landslides due to a heavy rainfall. Geotechnical and rheological tests were performed on waste materials corrected from Imgi waste rock dump, located in Busan Metropolitan City. Debris flow mobility was examined with the help of 1-D BING model which was often simulated in both subaerial and subaqueous environments. To determine flow curve, we used a vane-penetrated rheometer. The shear stress (${\tau}$)-shear rate (${\dot{\gamma}}$) and viscosity(${\eta}$)-shear rate (${\dot{\gamma}}$) relationships were plotted using a shear stress control mode. Well-known rheological models, such as Bingham, bilinear, Herschel-Bulkley, Power-law, and Papanastasiou concepts, were compared to the rheological data. From the test results, we found that the tested waste materials exhibited a typical shear shinning behavior in ${\tau}$-${\dot{\gamma}}$ and and ${\eta}$-${\dot{\gamma}}$ plots, but the Bingham behavior is often observed when the water contents increased. The test results show that experimental data are in good agreement with rheological models in the post-failure stage during shearing. Based on the rheological properties (i.e., Bingham yield stress and viscosity as a function of the volumetric concentration of sediment) of waste materials, initial flowing shape (5 m, 10 m, and 15 m) and yield stress (100 Pa, 200 Pa, 300 Pa, and 500 Pa) were input to simulate the debris flow motion. As a result, the runout distance and front velocity of debris flow are in inverse propositional to yield stress. In particular, when the yield stress is less than 500 Pa, most of failed masses can flow into the stream, resulting in a water contamination.