• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.109-119
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• 2017

In this research, it was investigated that whether the upper sand deposited in Nakdong River Estuary Delta region has the role of horizontal drains like sand mat. The results from tests for particle size distribution and permeability of the upper sand deposit did not meet completely the criteria for the horizontal drain material. Thus, numerical analysis has been conducted additionally. Numerical analyses of consolidation of soft soils with upper layer of sand deposit are conducted in both the sand mat with a thickness of 1m and the upper sand deposit with 1, 2, 3, and 4 m of thickness and their results are compared. As the results of numerical analysis, the upper sand deposit with a thickness of 2m or more may play the role of horizontal drains similar to a sand mat. If a PVD is installed, the ability of upper sand deposit as horizontal drains is increased. Form this study, it was concluded that the upper sand deposited in Nakdong River Estuary Delta has the role of horizontal drain.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.558-566
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• 2017

In this study, we developed an electron-emission OH radical generator for waste water treatment. The stability of the circuitry was ensured by implementing stable pulse waves with a MOSFET and reducing the momentary current rise. The OH radical generator uses a high-voltage and low-current discharger. The performance of the device was evaluated experimentally, which showed that it is possible to produce a stable and uniform pulse waveform for the drain current of the power MOSFET, which is connected to the input side of an AC multiplying converter through negative feedback circuitry with CR-snubber architecture. It was also possible to reduce the excitation current of the converter and improve the stability of the oscillation circuit. In addition, the generator can generate hydroxyl radicals stably. The bactericidal activities were also evaluated, and the germicidal power for E. coli, S. aureus, and S. flexneriwas improved by 99.9% or more after 60 minutes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.513-519
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• 2019

Typically, contaminated sediments cause clogging of the drain pipe, which increases the residual water pressure in the drain pipe; this study constructed a system for improving drainage efficiency of tunnels by reducing physical and chemical obstructions through ultrasonic energy generated by a PVDF film. The developed hybrid drainage system utilized a PVDF material film fused with an existing drainage tunnel and maintenance system resulting in the ability to initialize the reverse piezoelectric effect, which was evaluated through an on site application. In order to investigate the maintenance performance of the tunnel drainage system, contaminated sediments were simulated in a drainage pipe to test the effect of ultrasonic conditions on drainage efficiency in the laboratory. As a result of applying the developed portable equipment, the ultrasonic energy was generated for about 20 minutes resulting in a reduction of 74.62% of the contaminated sediments and improving drainage efficiency. From the tunnel, acoustic pressure measurements were taken to calculate the response rate while taking into account the laboratory results. In addition, PVDF film was attached to the transverse and longitudinal side of the drainage pipes where contaminated sediments occur most often in the field tunnel. these calculations show contaminant removal was 90% effective.

• Journal of Bio-Environment Control
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• v.16 no.4
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• pp.322-327
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• 2007

This study was conducted to analysis the chemical properties of Peunggang river and investigate the effect of irrigation sources on the growth of tomato and cucumber. The salt concentration in Peunggang river was high by $3.22{\sim}3.62dS{\cdot}m^{-1}s$ from March to May and lower gradually from April to February of next year, which was also lower in upper stream than in middle or low stream of Peunggang river. The growth such as plant height, fresh weight and dry weight in tomato and cucumber was better in drain water and tap water irrigation than in PR water (Peunggang river) irrigation. Mean fruit weight was highest in the tap water, and that of cucumber was no significance in the treatments. The number of setting fruit was lower in the PR water than in the treatments, and which was no significance between rain water and tap water. The yield of tomato and cucumber was found to be highest by 10,594 and 11,826 kg/10a in tap water, respectively and also lowest in the PR water among the three treatments. The fruit quality, soluble solids of tomato shows a tendency to increase in the PR water as compared with the other treatment, and the rate of blossom-end rote was higher by 13.6% in the PR water. T-N and P content of tomato and cucumber were no significance in the treatments. Ca content was lowest, but Na content highest in the PR water. It was thought that a rain water and tap water as alternative irrigation source of a PR water were proper.

• Journal of Korea Water Resources Association
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• v.52 no.4
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• pp.235-243
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• 2019

Recently, urban inundation was frequently occurred due to the intensive rainfall exceeding marginal capacity of the flood control facility. Furthermore, needs for the underground storage facilities to mitigate urban flood are increasing according to rapidly accelerating urbanization. Thus, in this study, drainage efficiency in drain tunnel connecting to underground storage was investigated from the air-core measurements in the drop shaft against two types of inlet structure. In case of the spiral inlet, the multi-stage structure is introduced at the bottom of the inlet to improve the vortex induction effect at low inflow discharge (multi-stage spiral inlet). The average cross-sectional area of the air-core in the multi-stage spiral inlet is 10% larger than the tangential inlet, and show the highly air emission effect and the highly inflow efficiency at the high inflow discharge. In case of the tangential inlets, the air emission effect decreased after exceeding the maximum inflow discharge, which is required to maintain the inherent performance of the tangential inlet. From the measurements, the empirical formula for the cross-sectional area of the air-core according to locations inside the drop shaft was proposed in order to provide the experimental data available for the inlet model used in experiments.

• Journal of Korea Water Resources Association
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• v.55 no.5
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• pp.345-356
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• 2022

A severe flooding occured at a small urban catchment in Daejeon-si South Korea on July 30, 2020 causing significant loss of property (inundated 78 vehicles and two apartments) and life (one casualty and 56 victims). In this study, a retrospective analysis of the inundation event was implemented using a physically-based urban flood model, H12 with high-resolution data. H12 is an integrated 1-dimensional sewer network and 2-dimensional surface flow model supported by hybrid parallel techniques to efficiently deal with high-resolution data. In addition, we evaluated the impact of the flooding barriers which were installed after the flood disaster. As a result, it was found that the inundation was affected by a combination of multiple components including the shape of the basin, the low terrain of the inundation area located in the downstream part of the basin, and lack of pipe capacity to drain discharge from the upstream during heavy rain. The impact of the flooding barriers was analyzed by modeling with and without barriers on the high-resolution terrain input data. It was evaluated that the flood barriers effectively lower the water depth in the apartment complex. This study demonstrates capability of high-resolution physically-based urban modeling to quantitatively assess the past inundation event and the impact of the reduction measures.

• Korean Journal of Soil Science and Fertilizer
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• v.38 no.3
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• pp.119-126
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• 2005

Soil erosion at Jawoon-Ri in Hongcheon highland is one of serious problems since saprolite piling on farmland has been typically practiced at 2-3 year's intervals. The objective of the case study was to survey management practices such as tillage, application of saprolite, and cultivating crops and to propose best management practices (BMP) to reduce soil loss in Jawoon-Ri, Hongcheon-Gun. Jawoon-Ri is located in the upper stream of Naerinchun. Upland areas of Jawoon 2 and 4Ri were 206.9 and 142.3 hectare, respectively. Estimation of soil loss in this study was based on USLE (Universal soil loss equation). Annual averaged soil losses were 15.6 MT per hectare in Jawoon-2Ri and 9.0 MT per hectare in Jawoon-4Ri, respectively. This case study tried to find methods to reduce soil erosion below tolerant soil loss level which is $11MT\;ha^{-1}\;yr^{-1}$. Estimated soil losses in more than 40% of uplands in Jawoon-2Ri and 4Ri were higher than tolerant soil loss level. Especially, edge of uplands undergone excessive soil erosion by concentrated runoff water. Therefore consolidation of upland edge was included as one of the proposed Best management practices BMP). The proposed BMP in this area were buffer strips, contour and mulching, diversion drain channel, grassed water-way, detour watet-way and cover crops and so on. Amounts for BMP requirements were 7,680 m for buffer strips, 123 ha (35%) for contour and mulching, 201 ha (57%) for diversion drain channel, 13,880 m for grassed water-way, 3,860 m for detour drainage, 8,365 m for sloping side consolidation and 3,492 ha for cover crops, respectively. Application of BMP are urgently needed in uplands which is direct conjunction with stream.

• Journal of Bio-Environment Control
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• v.9 no.1
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• pp.20-26
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• 2000

This study aims at analyzing physical and chemical properties of perlite substrate. Particles of substrate were divided into five categories In size: gravel, very-coarse, coarse, medium and fine grade. Particles of very-coarse and greater grades in perlite substrate occupied 98.5％ of total particles. The air phase of total particles was distributed between 76.8％ and 87.7％ with especially showing that of very-coarse grade was lower than that of coarse or smaller one. However, the liquid and solid phases were vice versa. The cation exchange capacity (CEC) measured was highest in the fine grade. In drainage experiments, the water being drained from the substrate increased with the ratio of drain area, and the 65~70％ of total water reduced within five minutes after irrigation. The drained volume was proportional to the depth of the substrate, which contained about 2mL.cm$^2$：by depth (cm). Due to quick reduction of the water in the substrate, the pF value increased in four minutes after irrigation and showed the highest negative correlation ($R^2$＝0.997) with the moisture content of the substrate. The physical and chemical properties including drainage characteristics analyzed in this study can be, therefore, utilized to control the moisture content of perlite substrate, efficiently.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.386-394
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• 2019

In this study, according to drainage condition (undrained and drained) in ground, the settlement and horizontal displacement of caisson quay wall and apron in Yeongilman port due to excess pore water pressure in ground induced by the magnitude 5.4 earthquake in Pohang on November 15, 2017. In general, seismic response analysis was carried out under undrained drainage condition, but in this study, drain drainage analysis was conducted to estimate displacement during earthquake as well as an additional displacement due to dissipation of excess pore water pressure after earthquake. The result of after earthquake can not be known under undrained drainage condition. Results cleary showed that the behavior of structure and ground was dependent on drainage condition in ground. Especially, based on the drained drainage condition, the additional displacement was clearly detected due to dissipation of excess pore water pressure after earthquake. Which indicates that both results are different to drainage condition in ground, and therefore, drainage condition analysis is necessary to accurately estimate the behavior of ground and structure in seismic response analysis.

• Water for future
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• v.15 no.2
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• pp.11-22
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• 1982

This study is to find out the reasonable drainage system of sewerage in connection with the geographical conditions, the form of city, and the problem of sewerage in and around Seoul. (1) In supplying the sewerage sewer, the separating system is desirable in connection with the problem of sewerage disposal in future. However, in the existing urban district, the conjunction system is used because of the large amount invested according to the diversion of the sewer of the separation system and the influence of the traffic communication. The sewer of the separating system should be used in the case of the fundamental reconstruction of structure as the redevelopment of the urban district or the subway and new-development of area. Therefore, the separating system should be used completely until the goal year. (2) Drainage area was divided for the natural flowing, considering that the 38 streams and topography paly a role of the main stream of drainage. There are the branches, Guyui, Dug-island, Jayang, Hannam, Banpo, Amsa whose divisions are impossible. In these branches, the drain planning was suggested a forced control method by using the exiting pond age and the pumping station. (3) The best available method which improbes the water quality in Han river is as follows. The sewerage is catched and carried to the sewerage disposal plant by establishing the intercept sewer in both or one side of stream. At the same time, the groudwater volume which springs in each stream is drained separatively.