• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.6
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• pp.69-77
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• 2015

The objective of this study was to evaluate the performance of selected sediment reduction methods to reduce sediment discharges from drain and irrigation of different types (concrete canals, soil canals). This study was carried out to analysis for the suspended sediment concentration and sediment of drain and irrigation by velocity of flow. The results of study were analysised and summerized as follow. Sedimentation characteristics and size of soil sediment from the concrete and soil canals of downstream smaller than upstream. Suspended sediment concentration and flow times from the suggestion canals bigger than open canal. Structural shape of the canal decreases the velocity of flow also affects the suspended sediment concentration and flow times.

• Journal of the Korean Geographical Society
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• v.39 no.1
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• pp.45-55
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• 2004

The paper describes the rainfall-runoff. soil moisture distribution and subsurface flow of 'U-shaped Goll' valley head slope to evaluate quantitatively the interaction between the water circulation system and geomorphic development. The findings are as follows: The fissure and the pipe entrance in front of 'U-shaped Goll' introduce a lot of direct runoff into either the soil pipe or the soil layer to accelerate the erosion of the soil layer, so that they are likely to contribute to the expansion and development of the soil pipe. Most of soil water is to be drained in pipe flow, while some of remaining soil water is to be fed into groundwater. Therefore, low rainfall intensity is thought to let both the groundwater level and the pipe flow react sensitively by the effects of the precedent rainfall even at events: As a result, the soil pipe is said to be an important factor having influence upon the material balance of 'U-shaped Goll' valley head slope. On the other hand, the groundwater shows greater specific flux at the top than at the bottom, and relatively larger specific flux is applied to the top to make 'U-shaped Goll' valley head slope go back to the top.

• Geomechanics and Engineering
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• v.27 no.5
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• pp.433-445
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• 2021

Artificial ground freezing (AGF) is a commonly used geotechnical support technique that can be applied in any soil type and has low environmental impact. Experimental and numerical investigations have been conducted to optimize AGF for application in diverse scenarios. Precise simulation of groundwater flow is crucial to improving the reliability these investigations' results. Previous experimental research has mostly considered horizontal seepage flow, which does not allow accurate calculation of the groundwater flow velocity due to spatial variation of the piezometric head. This study adopted vertical seepage flow-which can maintain a constant cross-sectional area-to eliminate the limitations of using horizontal seepage flow. The closure time is a measure of the time taken for an impermeable layer to begin to form, this being the time for a frozen soil-ice wall to start forming adjacent to the freeze pipes; this is of great importance to applied AGF. This study reports verification of the reliability of our experimental apparatus and measurement system using only water, because temperature data could be measured while freezing was observed visually. Subsequent experimental AFG tests with saturated sandy soil were also performed. From the experimental results, a method of estimating closure time is proposed using the inflection point in the thermal conductivity difference between pore water and pore ice. It is expected that this estimation method will be highly applicable in the field. A further parametric study assessed factors influencing the closure time using a two-dimensional coupled thermo-hydraulic numerical analysis model that can simulate the AGF of saturated sandy soil considering groundwater flow. It shows that the closure time is affected by factors such as hydraulic gradient, unfrozen permeability, particle thermal conductivity, and freezing temperature. Among these factors, changes in the unfrozen permeability and particle thermal conductivity have less effect on the formation of frozen soil-ice walls when the freezing temperature is sufficiently low.

• Environmental Engineering Research
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• v.11 no.5
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• pp.241-249
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• 2006

A mathematical model is described for the prediction of convective upward transport of an organic solvent driven by evaporation at the surface, which is known as the major transport mechanism in the in-situ photolysis of a soil contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin(TCDD). A finite-element model was proposed to incorporate the effects of multiphase flow on the distribution of each fluid, gravity as a driving force, and the use of hysteretic models for more accurate description of k-S-p relations. Extensive numerical calculations were performed to study fluid flow through three types of soils under different water table conditions. Predictions of relative permeability-saturation-pressure (k-S-p) relations and fluids distribution for an illustrative soil indicate that hysteresis effects may be quite substantial. This result emphasizes the need to use hysteretic models in performing flow simulations including reversals of flow paths. Results of additional calculations accounting for hysteresis on the one-dimensional unsaturated soil columns show that gravity affects significantly on the flow of each fluid during gravity drainage, solvent injection, and evaporation, especially for highly permeable soils. The rate and duration of solvent injection also have a profound influence on the fluid saturation profile and the amount of evaporated solvent. Key factors influencing water drainage and solvent evaporation in soils also include hydraulic conductivity and water table configuration.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.454-458
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• 2007

Nonpoint source (NPS) pollution is a serious problem causing the degradation of soil and water quality. Concentrated overland flow is the primary transport mechanism for a large amount of NPS pollutants from hillslope areas to downslope areas in a watershed. In this study, a soil erosion model, nLS model, to identify transitional overland flow regions (i.e., ephemeral gully head areas) was developed using the kinematic wave overland flow theory. Spatial data, including digital elevation models (DEMs), soil, and landcover, were used in the GIS-based model algorithm. The model was calibrated and validated using gully head locations in a large agricultural watershed, which were identified using 1-m aerial photography. The model performance was better than two previous approaches; the overall accuracy of the nLS model was 72 % to 87 % in one calibration subwatershed and the mean overall accuracy was 75 to 89 % in four validation subwatersheds, showing that the model well predicted potential transitional erosion areas at different watersheds. However, the user accuracy in calibration and validation was still low. To improve the user accuracy and study the effects of DEM resolution, finer resolution DEMs may be preferred because DEM grid is strongly sensitive to estimating model parameters. Information gained from this study can improve assessing soil erosion process due to concentrated overland flow as well as analyze the effect of microtopographic landscapes, such as riparian buffer areas, in NPS control.

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.5
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• pp.362-367
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• 2014

This study was performed to test the applicability of the ozone/hydroxy radical reaction system, which applied advanced oxidation processes, to remove total petroleum hydrocarbon (TPH) from the fine soil in washing water of the soil washing process. Removal efficiency was tested on 40 L of washing water in a pilot reaction tank. Fine soil contaminated with $800mg\;kg^{-1}$ TPH was prepared at 5% and 10% suspended solids. Testing conditions included ozone/hydroxy radical flow rates of 40, 80, and $120L\;min^{-1}$, and processing time of 2 to 12 hours. The removal efficiency of petroleum hydrocarbon from water waster by ozone/hydroxy radical was increased with higher flow rates and lower percentages of suspended solids. Optimal efficiency was achieved at $80L\;min^{-1}$ flow rate for 4 hours for the 5% suspended solids, and $120L\;min^{-1}$ for 6 hours for the 10% suspended solids. These results verified the efficiency of hydroxy radical in removing TPH and the applicability of the ozone/hydroxy radical reaction system in the field.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.1
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• pp.43-59
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• 2017

This study presents the prediction methodology of debris flow occurrence areas using the SINMAP model. Former studies used a single calibration region applying some of the soil test results to predict debris flow occurrence in SINMAP model, which couldn't subdivide the soil properties for the target areas. On the other hands, a multi-calibration region using a detailed soil map and soil strength parameters (c, ${\phi}$) for each soil series to make up for limitation of former studies is proposed. In this process, soils with soil erodibility factor (K) are classified into three types: 1) gravel and gravelly soil. 2) sand and sandy soil, and 3) silt and clay. In addition, T/R estimation method using mean elevation of target area instead of T/R method using actual occurrence time is suggested in this study. The suggested method is applied to Seobyeok-1 ri area, Bonghwa-gun where debris flow occurred. As a result of comparison between two T/R estimation method, both T/R estimations are almost equal. Therefore, the suggested methodologies in this study will contribute to set up the national-wide mitigation plan against debris flow occurrence.

• Journal of Coastal Disaster Prevention
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• v.5 no.4
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• pp.173-182
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• 2018

As the research about increasing the efficiency of dredging soil transport, the technology, which reduce the friction between pipe wall and fluid in the pipe and disturbed generating pipe blockage, has been developed. So for the purpose of applying this technology to real construction site, main test has been tried at the real scale test in field. As a test result, this paper will show 30% flow efficiency increasing by permitted electro magnetic force to the pipe. And test result was evaluated as a ultra sonic velocity profiler. To propose the design technique and the execution manual of the high efficiency dredging material transport technic, this research have confirmed flow status changing depending on a soil material kind under electro-magnetic field and analyze the effect of electro-magnetic field which affects to each dredged soil material transportation. For achieving this research, EMF(Electro-Magnetic Field) generator is installed on the dredger(20,000HP) and through monitored flow status, dredging soil flow rate and sampled material specification is confirmed. Also dredger operating condition is measured and dredger power for soil transportation, hydraulic gradient and flow rate are compared, as transportation efficiency is calculated by this parameter, it is possible to check transportation efficiency improvement depending on each dredged soil material under electro-magnetic field. To verify the technique of dredged soil transfer using electromagnetic field, which is the core technique of the high efficiency dredged soil transfer, and the technique of expert system for pipeline transfer and the flow state. This could lead to a verification of transfer efficiency according to the characteristics of the dredged soil (sand, clay, silt) and the transfer distance (5km, 10km, 15km), which is planned to be used for a technology development of pump power reduction and long-distance transfer applying the high efficiency dredged soil transfer technology.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.10 no.5
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• pp.76-86
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• 2007

For the purpose of ground improvement by means of soil flushing systems. Incorporated technique with prefabricated vertical drains have been used for dewatering from fine-grained soils. The laboratory model tests were performed by using the flushing tracer solutions for silty soils and recorded the tracer concentration changes with the elapsed time and flow rates. A mathematical model for prediction of contaminant transport using the PVD technology has been developed. The clean-up times for the predictions on both soil condition indicate more of a sensitivity to the dispersivity parameter than to the extracted flow rate and vertical velocity parameters. Based on the results of the analyses, numerical analysis indicate that the most important factor to the in-situ soil remediation in prefabricated vertical drain system is the effective diameter of contaminated soil.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.1
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• pp.118-125
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• 2011

Conventional erosion function apparatus (EFA) which has been used to measure the hydraulic resistance of soil was improved to consider direction change of the current flow. Using improved apparatus, hydraulic resistance capacities of the artificially composed clayey soil and sandy soil were compared. Test result shows that scour rates which were measured under the bi-directional flow were much higher than those measured under unidirectional flow for both type soils. Scour rate of sandy soil was higher than that of clayey soil. Velocity averaged scour rate of specimen which was consolidated under the relatively large consolidation pressure is higher than that of specimen which is consolidated under small consolidation pressure, which means scour problem under bidirectional flow may be more serious for the deep seabed ground.