• Journal of Wetlands Research
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• v.20 no.1
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• pp.63-71
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• 2018

The particle filtration mechanisms in an infiltration trench should be varying due to the different hydraulic conditions during stormwater runoff. The understanding of these variations associated with different filtration mechanisms and their effect on the particle removal efficiency is of vital importance. Therefore, a LID (Low Impact Development) system comprising of an infiltration trench packed with gravel and woodchip was investigated during the monitoring of several independent rainfall events. A typical rainfall event was divided into separate regimes and their corresponding flow conditions as well as filtration mechanisms in the trench were analyzed. According to hydraulic conditions, it was found out that filtration changes between vertical and horizontal flows as well as between unsaturated, saturated, and partially-saturated flows. Particle separation efficiency was high (55-76%) and was mainly governed by physical straining during the unsaturated period. It was then enhanced by diffusion during the saturated period (75-95%). When the trench became partially saturated at the end of the rainfall event, the efficiency decreased which was believed to be due to the existence of a negatively charged air-water interface which limited the removal to positively charged particles.

• Korean Journal of Ecology and Environment
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• v.35 no.4 s.100
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• pp.295-305
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• 2002

Benthic macro- invertebrates were collected in a 200 m reach located in the $3^{rd}$ order Yangjae Stream, a tributary of the Han River, Seoul, from April 1996 to March 1998. Although species richness was relatively low due to organic pollution, community abundance patterns appeared to be different depending upon location of the sampling sites. At the sample sites in the straight zone with high water velocity and large substrates, species richness was high and species relatively less-tolerant to organic pollution was additionally present. At the sample sites in the pool zone with lower velocity and high sedimentation, species richness was low and a few tolerant species to organic pollution were abundantly collected. The principle component analysis indicated that some sample sites in the straight zone appeared to be related to water velocity and shear velocity, and associated with diverse taxa less tolerant to organic pollution. Additionally the sample site transplanted with large substrates was associated wit]h hydraulic characters such as substrate diversity and roughness, and was related to species indicating partial recovery of water. The sample sites located at the pool zone tended to be associated with organic matter that had sedimented on to the substrates and the taxa tolerant to organic pollution, including Oligochaeta and Chironomus.

• Journal of Korea Water Resources Association
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• v.52 no.10
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• pp.719-728
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• 2019

Valve in water distribution network (WDN), that controls the flow in pipes, is used to isolate a segment (a part of WDN) under abnormal water supply conditions (e.g., pipe breakage, water quality failure event). The segment isolation degrades pressure and water serviceability in neighboring area during the water service outage of the segment. Recent hydraulic and water quality failure events reported encouraging WDN valve installation based on various abnormal water supply scenarios. This study introduces a scenario-based optimal valve installation approach to optimize the number of valves, the amount of undelivered water, and a shortest water supply path indicator (i.e., Hydraulic Geodesic Index). The proposed approach is demonstrated in the valve installation of Pescara network, and the optimal valve sets are obtained under multiple scenarios and compared to the existing valve set. Pressure-driven analysis (PDA) scheme is used for a network hydraulic simulation. The optimal valve set derived from the proposed method has 19 fewer valves than the existing valve set in the network and the amount of undelivered water was also lower for the optimal valve set. Reducing the reservoir head requires a greater number of valves to achieve the similar functionality of the WDN with the optimal valve set of the original reservoir head. This study also compared the results of demand-driven analysis (DDA) and the PDA and confirmed that the latter is required for optimal valve installation.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.1
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• pp.75-94
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• 2019

As the present single-layer repository concept requires too large an area for the site of the repository, a multi-layer repository concept has been suggested to improve the disposal density. The effects of the excavation damaged zone around the multi-layer repository constructed in the deep host rock on the temperature distribution in the repository were analyzed. For the thermal analysis of the multi-layer repository, the hydrothermal model was used to consider the resaturation process occurring in the buffer, backfill and rock. The existence of an excavation damaged zone has a significant effect on the temperature distribution in the repository, and the maximum peak temperatures of double-layer and triple-layer repositories can rise to $7^{\circ}C$ and $12^{\circ}C$, respectively depending on the size of the excavation damaged zone and the degree of decrease of the thermal conductivity. The dominant factor affecting the peak temperature in the multi-layer repository is the decrease of thermal conductivity in the excavation damaged zone, and the excavation damaged zone formed around the deposition hole has more significant effects on the peak temperature than does the excavation damaged zone formed around the disposal tunnel.

• The Journal of Engineering Geology
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• v.30 no.4
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• pp.603-615
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• 2020

The design factors of artificial recharge are determined by considering the hydrogeological characteristics of the aquifer. The optimal design factors for artificial recharge were derived after performing the injection tests step by step for each injection type (vertical well, ditch and mixed type), which were built in the test site of the study area. It was analyzed that the difference in the injection effect according to the diameter of the injection well was not large, and the 100 mm well was evaluated as appropriate in consideration of the availability and economy of land use. Since the injection effect was well maintained even in the upper rock, the depth of the injection well was proposed for the alluvial layer and the upper rock layer. On the other hand, in four cases of filter media in the ditch, it was analyzed that the penetration efficiency and the hydraulic interference effect indicated excellent injection performance when a filter medium of 10 to 30 mm diameter was filled in the ditch. In addition, the proper spacing of the injection wells was analyzed as 9~12 m considering the interference efficiency. The interference efficiency attenuation coefficient per 1 m of hole spacing was calculated to be 1.75% in this area. In the future study, the artificial recharge design factors obtained in this stage are applied and verified on site construction and operation. Also it is expected to contribute to securing water in areas where there is always a lack of water.

• Tunnel and Underground Space
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• v.32 no.1
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• pp.59-77
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• 2022

Currently, the design reference temperature of the buffer material for disposing of high-level radioactive waste is less than 100℃, so if the heat dissipation capacity of the buffer material is improved, the spacings of the disposal tunnel and the deposition hole in the repository can be reduced. First of all, this study tries to analyze the criteria for thermal-hydraulic-mechanical performance of the buffer materials and to investigate the researches regarding the enhanced buffer materials with improved thermal conductivity. First, the thermal conductivity should be as high as possible and is affected by dry density, water content, temperature, mineral composition, and bentonite type. the organic content of the buffer material can have a significant effect on the corrosion performance of a canister, so the organic content should be low. In addition, hydraulic conductivity of the buffer material should be less than that of near-field rock and swelling pressure should be appropriate for buffer materials to function properly. For the development of enhanced buffer materials, additives such as sand, graphite, and graphite oxide are typically used, and a thermal conductivity can be greatly improved with a very small amount of graphite addition compared to sand.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.435-450
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• 2022

In step-by-step site selection for geological disposal of high-level radioactive waste, parameters necessary for site selection will be acquired through deep drilling surveys from the basic survey stage. Unlike site investigations of rock mass structures such as tunnels and underground oil storage facilities, those related to the geological disposal of high-level radioactive waste are not only conducted in relatively deep depths, but also require a high level of quality control. In this report, based on the 750 m depth drilling experience conducted to acquire the parameters necessary for deep geological disposal, the methodology for deep drilling and the geology, geophysics, geochemistry, hydrogeology and rock mechanics obtained before, during, and after deep drilling are discussed. The procedures for multidisciplinary geoscientific investigations were briefly described. Regarding in-situ stress, one of the key evaluation parameter in the field of rock engineering, foreign and domestic cases related to the geological disposal of high-level radioactive waste were presented, and variations with depth were presented, and matters to be considered or agonized in acquiring evaluation parameters were mentioned.

• Journal of the Korean Geotechnical Society
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• v.38 no.11
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• pp.107-118
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• 2022

The social need for stable hydrogen storage technologies that respond to the increasing demand for hydrogen energy is increasing. Among them, underground hydrogen storage is recognized as the most economical and reasonable storage method because of its vast hydrogen storage capacity. In Korea, low-depth hydrogen storage using artificial protective structures is being considered. Further, establishing corresponding safety standards and ground stability evaluation is becoming essential. This study evaluated the hydro-mechanical behavior of the ground during a hydrogen gas leak from a low-depth underground hydrogen storage facility through the HM coupled analysis model. The predictive reliability of the simulation model was verified through benchmark experiments. A parameter study was performed using a metamodel to analyze the sensitivity of factors affecting the surface uplift caused by the upward infiltration of high-pressure hydrogen gas. Accordingly, it was confirmed that the elastic modulus of the ground was the largest. The simulation results are considered to be valuable primary data for evaluating the complex analysis of hydrogen gas explosions as well as hydrogen gas leaks in the future.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.213-213
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• 2011

근래 이상기후에 의한 강우량 증대와 도시화에 따른 첨두유출량의 증대 및 도달시간의 단축은 기존의 유수지만으로 도시홍수를 대처하는데 그 한계점에 다다르게 되었다. 1990년대에 들어 각종 우수유출 저감시설의 활용으로 이상의 문제를 해결하고자 하는 노력들이 시작되었으며, 현재 신규개발지에 저류지와 같은 우수유출저감시설 설치를 법제도적으로 의무화 하고 있어, 전국적으로 천여개소의 저류지가 시설되어 있거나 계획 중에 있다. 저류지는 개발로 인해 증가된 첨두유출량을 개발전의 상태로 저감시키기 위하여 임시 또는 상시 저류하거나 저류능력 이상의 유출량에 대해서는 암거방류시설을 통해 하류부의 하천 또는 하도로 방류시키는 역할을 수행하는 수공구조물로서 일반적으로 저류지 계획 및 설계는 첨두유출량 증가분에 대해 초점을 맞추고 있을 뿐 방류시설에 대한 구체적인 설계는 이루어지지 않고 있는 실정이다. 또한 현재 국내에는 저류지 방류시설로 주로 사용되는 암거에 관한 설계규정이나 기법은 미미한 상태로, 한국도로공사(1991)에서 발표한 "도로배수계획"을 이용하고 있으며, 이는 미국 연방도로국(FHWA, 1985)에서 발표한 설계기법을 그대로 인용하고 있다. 즉, 지형 또는 현장 여건에 따라 암거 흐름의 8형식 중 하나의 형식으로 결정하고, 그 형식에 따라 관련도표를 이용한 시산법 또는 도식해법을 적용하여 유입부 상류수위를 산정함으로써 암거설계가 이루어진다. 하지만 이러한 암거설계 방식은 도로 배수암거에 적합한 것으로 저류지 배수암거에 적용하기에는 무리가 있다고 본다. 따라서, 본 연구에서는 저류지의 일반적인 특성상 암거흐름 8형식 중 Class-II군의 암거 상류부 수위가 잠수된 조건 즉, 평상시 저류지가 일정수위 이상의 저류량을 유지하고 있는 상태에서 저류지 암거방류시설의 대표적인 설계인자인 암거직경, 암거경사, 암거경사, 하류단 수위조건의 변화에 따른 상류부 수위변화를 유량별로 분석해 보았다. 방류 암거의 개수를 고려하기 위하여 암거상류부 수위와 암거직경의 관계해석 시 암거단면적을 이용하여 분석하였으며, 각각의 유량별로 상류부 수위와 암거단면적의 관계를 회귀식으로 제시하였다. 암거상류부 수위와 암거경사의 관계를 분석한 결과 암거경사가 5~20%로 변화할 때 암거상류부 수위의 변화는 2~5%정도의 매우 작은 변화를 보임을 확인할 수 있었으며, 암거길이의 경우는 해석 조건의 특성상 상류부 수위에 영향이 전혀 나타나지 않았다. 암거상류부 수위와 암거하류단 수위의 관계에서 암거상류부 수위는 암거하류단 수위가 암거직경과 퇴사위 높이의 합보다 암거하류단의 수위가 높아지는 시점부터 암거하류단 수위에 비례해서 증가되는 결과를 알 수 있었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3B
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• pp.205-209
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• 2011

The low carrying capacity caused by the deposition in a sewer line is one of the main reason of the urban flood. Therefore, an efficient maintenance and management of the storm water drainage system is very important to prevent urban flood. In this research, the sediment transport characteristics through a pressure pipeline were examined with laboratory experiments. Bed-forms in a pipeline, sediment rates, roughness due to sediments were examined. Experimental system consists of flow circulation system with a pump and a sediment feeder at the upstream of the pipeline. Sediments were supplied into a 60 mm-diameter and 8 m-long pipe. Maximum flow rate is $30m^3/hr$, and the sediment feeding rate range is 5 g/s~19 g/s. Governing parameters and estimation equation for sediment transport rate were developed. The mean velocity (U), coefficient of viscosity (${\mu}$), unit width bed load ($q_b$), mean diameter of particle ($d_{50}$), unit weight of sediment in water (${\gamma}^{\prime}_s$) were adopted as the most influencing factors of sediment transport patterns. The prediction equation for sediment transport rate were developed with two dimensionless terms. These two dimensionless terms showed a linear relationship with high correlation coefficient.