• Proceedings of the Korea Water Resources Association Conference
• /
• 2011.05a
• /
• pp.419-419
• /
• 2011

이상호우, 사막화, 빙하융해, 생태계 먹이사슬 변화, 이상기온 등 기후변화의 행태는 지구 곳곳에서 다양하게 발발되고 있으며 그로인해 발생되는 인적 물적 피해가 심각하다. 1996년 집중호우에 의한 연천댐체 파괴, 2002년 8월의 낙동강 유역 장기홍수, 2002년 태풍 루사 및 2003년 태풍 매미 등 국내에서는 기후변화 중에서도 주로 이상호우로 인해 발생하는 피해가 많았으며 이들은 주기성이나 특성을 갖지 않아 예측이 어려운 관계로 망양보뢰 식의 후처리에 급급한 실정이었다. 최근 기후변화에 따른 지역별 홍수량, 가뭄량 등에 관한 연구가 가속화되고 있으며, 이와 더불어 해당 기후모델 발현 시 기존 구조물에 미치는 영향에 대한 연구도 필수적이다. 나아가 기존 구조물 뿐 아니라 새로 시공되는 구조물의 설계에서 기후변화에 대한 안정성을 위해 추가적으로 포함해야 할 요소가 있는지에 대한 연구도 필요하다. 본 연구에서는 가상 기후모델에 대해 그 모델이 예측하는 홍수량이 실제 발현되었을 경우를 가정하여, 기존 수공구조물의 안정성에 미치는 영향을 살펴보고 영향인자의 민감도를 분석하고자 한다. 대상 수공구조물은 붕괴 시 영향력이 큰 정도를 기준으로 필댐, 콘크리트차수벽형석괴댐(CFRD), 콘크리트중력식댐, 제방으로 그 범주를 제한 하였으며 대상유역은 한강으로 가정하였다. 구조물의 안정성 검토방법은 각 구조물의 종류에 따라 상이하다. 흙이 주 재료인 제방과 필댐의 경우, 침투(Piping)와 비탈면(Sliding)에 대한 안정성 평가가 이루어지며 CFRD는 댐체와 벽체로 나누어 안정성평가를 하며 댐체 안정성 평가방법은 필댐과 유사하다. 본 연구에서는 하천설계기준(2009)과 댐설계기준(2005)에 따라 각 구조물의 기준안전율을 책정하였으며 점착력, 내부마찰각, 단위중량 등의 물성치는 해당 지역의 토질특성에 따라 여러 문헌을 참고하여 설정하였고 이를 SEEP/W, SLOPE/W 프로그램을 이용하여 구조해석을 실시하였다. 콘크리트중력식댐은 활동, 전도, 지지력에 대해 각각 안정성을 평가하며 MIDAS와 ABAQUS 프로그램을 병행하여 해석하였다. 민감도(Sensitivity)란 안정성에 영향을 미치는 설계인자들의 변화에 따라 안정성이 어떻게 변화하는 지를 말한다. 기후변화에 의한 수공구조물 설계인자 민감도 연구를 통해 기존 설계과정 또는 안정성 검토 시 해당인자의 기여도를 높이거나 새로운 설계인자를 추가하여 미래 상황에 대한 구조물의 위험 정도를 과거대비 상세히 예측할 수 있으며 나아가 적절한 대응 방안 제시에 기여하여 기후변화에 따른 피해를 감소할 수 있을 것이라고 생각된다.

• Journal of Korea Water Resources Association
• /
• v.42 no.5
• /
• pp.397-406
• /
• 2009

River is able to change by various environmental factors. In order to conduct restoration design of abandoned river channels, it is necessary to evaluate the river through the analysis of past and present river channels. River evaluation requires various data, such as geometry, hydraulic and hydrology, but there is a lot of difficulty to understand topographical information of river change on time and space due to a lack of past data by domestic conditions. This study analyzes the changes in past and present river channels and examines the applicability of river channel evaluation through image analysis using aerial photographs and 1918 year's map. Aerial photograph analysis was conducted by applying the image analysis method and GIS analysis method on Cheongmicheon. As a result of this analysis, we have quantitatively identified the form and size of abandoned channels, changes in the vertical-section and cross-section length of rivers, and micro-landform changes. More importantly, we verified that morphological changes in sandbars due to artificial straightening are important data in identifying the state of current river channels. In these results, although image analysis technique has limitations in two-dimensional information from aerial photographs, we were able to evaluate the changes in river channel morphology after artificial maintenance of the river.

• Journal of Wetlands Research
• /
• v.22 no.2
• /
• pp.145-152
• /
• 2020

Highways are characterized by high non-point pollutant emissions due to high traffic volumes and sections that cause abrupt change in driving speed (i.e. rest stations, ticketing office, etc.). Most highways in Korea were constructed with layers that do not allow adequate infiltration. Moreover, non-point pollution reduction facilities were not commonly installed on domestic highways. This study was conducted to evaluate a facility treating highway runoff and develop a cost-effective design for infiltration facilities by using soil amendment techniques. Performing soil amendment increased the hydraulic retention time (HRT) and infiltration rate in the facility by approximately 30% and 20%, respectively. The facility's efficiency of removing non-point pollutants (Total Suspend Soiled (TSS), Chemical Oxygen Demand(COD), Biological Oxygen Demand(BOD), Total Nitrogen (TN) and Total Phosphorus, (TP) were also increased by 20%. Performing soil amendment on areas with low permeability can increase the infiltration rates by improving the storage volume capacity, HRT, and infiltration area. The application of infiltration facilities on areas with low permeability should comply with the guidelines presented in the Ministry of Environment's Standards for installation of non-point pollution reduction facilities. However, soil amendment may be necessary if the soil infiltration rate is less than 13 mm/hr.

• Journal of Korea Water Resources Association
• /
• v.49 no.1
• /
• pp.61-72
• /
• 2016

In Korea, the aquifers at the coastal areas are mostly shallow alluvial unconfined aquifers. To simulate the flow and dispersion in unconfined aquifer, a FDM model has been developed to solve the nonlinear Boussinesq equation. Related analysis and verification have been executed. The iteration method is used to solve the nonlinearity, and the model shows 3-D shape because it is a 2-D y model that consider the undulation of water table and bottom. For the verification of the model, the output of flow module is compared to the 1-D analytic solution of Lee (1989) which have the drawdown or uplift boundary condition, and the two results show almost the same value. and the mass balance of dispersion module shows about 10% error. The developed model can be used for the analysis and design of the flow and dispersion in the unconfined aquifers. The model has been applied to the estuary area of Ssangcheon watershed, and the parameters have been deduced as a result : hydraulic conductivity is 90 m/day, and longitudinal dispersivity is 15 m. And the analysis with these parameters shows that the wells are situated in the influence circle of each others except for No. 7 well. Groundwater discharge to sea is $3700m^3/day$. And the chlorine ion ($cl^-$) concentration at the pumping wells increase at least 1000 mg/L if groundwater dam is not exist, so the groundwater dam plays an important role for the prevention of sea water intrusion.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.38 no.2
• /
• pp.249-259
• /
• 2018

More than half of annual rainfall occurs in summer season in Korea due to its climate condition and geographical location. A frequency analysis is mostly adopted for designing hydraulic structure under the such concentrated rainfall condition. Among the various distributions, univariate Gumbel distribution has been routinely used for rainfall frequency analysis in Korea. However, the distributional changes in extreme rainfall have been globally observed including Korea. More specifically, the univariate Gumbel distribution based rainfall frequency analysis is often fail to describe multimodal behaviors which are mainly influenced by distinct climate conditions during the wet season. In this context, we purposed a Gumbel mixture distribution based rainfall frequency analysis with a Bayesian framework, and further the results were compared to that of the univariate. It was found that the proposed model showed better performance in describing underlying distributions, leading to the lower Bayesian information criterion (BIC) values. The mixed Gumbel distribution was more robust for describing the upper tail of the distribution which playes a crucial role in estimating more reliable estimates of design rainfall uncertainty occurred by peak of upper tail than single Gumbel distribution. Therefore, it can be concluded that the mixed Gumbel distribution is more compatible for extreme frequency analysis rainfall data with two or more peaks on its distribution.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.23 no.6
• /
• pp.482-488
• /
• 2011

Seadike is a coastal structure constructed in the rear region of the foreshore to maximize its usability by preventing direct effect of wave. The expected construction field is determined under the design wave and tidal condition where minor wave overtopping is anticipated. Thus, the location of seadike is generally fixed at the highest site of the surrounding area with seadike crest height controlling the permissible range of wave overtopping volume. But a lot of times, frontal sand beach of the seadike continuously deforms due to incident waves, resulting failure in maintaining its initial slope. The erosion and deposition of the seadike front cause changes in the crest height and volume of wave overtopping and decrease in the setting depth of the seadike, which endangers seadike region as a result. In this study, the relation of local scouring and setting depth of the seadike front in the run-up region is examined by using 2D hydraulic model tests and numerical simulations by modified SBEACH model. As a result, the study learned that if appropriate boundary condition is applied to the modified SBEACH model, it is possible to create practical estimations on the local scouring at the seadike foot when erosive waves flow into the region.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.22 no.5
• /
• pp.295-305
• /
• 2010

Although the rubble mound breakwaters in Korea have been damaged by typhoons almost every year, quantification of erosion of armor block have seldomly been made. In this paper, the damage of armor units is standardized by the relative damage. In the case where the number of damaged units is reported, it is divided by the total number of units to calculate the relative damage. In the case where the rehabilitation cost is reported, the relative damage is calculated by using its relationship with the present value of the past rehabilitation cost. The relative damage is shown to have strong correlations with the typhoon parameters such as nearest central air pressure and maximum wind speed at each site. On the other hand, the existing numerical methods for calculating the cumulative damage are compared with hydraulic model tests. The method of Melby and Kobayashi (1998) is shown to give a reasonable result, and it is used to calculate the relative damage, which is compared with the measured damage. A good agreement is shown for the East Breakwater of Yeosu Harbor, while poor agreement is shown for other breakwaters. The poor agreement may be because waves of larger height than the design height occurred due to strong typhoons associated with climate change so that the relative damage increased during the last several decades.

• Journal of the Korean Geosynthetics Society
• /
• v.13 no.3
• /
• pp.1-10
• /
• 2014

Several types of methods such as resistivity survey, ground penetration radar, etc are used for detection of levee leakage and according to the river design guidelines detection of levee leakage is performed by measuring the hydraulic conductivity of levee soil. But, the former can not verify the leakage point and degree of saturation, the latter is an after treatment method. Movable sensor, which is a high-tech TDR system developed since 2000, can obtain directly the dielectric constant profile covering the whole depth of levee. In this study, laboratory and field model experiments were carried out using movable TDR sensor in order to evaluate the applicability as detection system of levee leakage, As the result, movable TDR system has proven to be 3 times more sensitive to water contents than dry unit weight, and the results conclude that the dielectric constant, water contents and density of the ground proved to have a correlation among them, and the dielectric constant is expected to be a basic data on detection of levee leakage.

• Journal of Korea Water Resources Association
• /
• v.47 no.2
• /
• pp.161-170
• /
• 2014

It is important to estimate an appropriate quantile for design of hydraulic structure. For this purpose, it is necessary to find the appropriate probability distribution which can represent the sample data well. Probability plot correlation coefficient test as one of goodness-of-fit test, is recently developed and has been known as a simple and powerful method. In this study, probability plot correlation coefficient test statistics using the plotting position considering the coefficients of skewness for the GEV distribution is derived, and represented by the regression equation. Monte-Carlo method is also performed to compare the rejection power between each method. As the results, the probability plot correlation coefficient test which is derived in this study is better than the others. In particular, when sample size is small and distribution has the shape parameter, rejection power of probability plot correlation coefficient test considering the coefficients of skewness is bigger than the others.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.43 no.10
• /
• pp.928-935
• /
• 2015

This paper presents low temperature structural tests of a UAV wing which has room temperature-curing adhesive bond. The wing structure is made of carbon fiber reinforced composites, and the skins are bonded to the inner structures (such as ribs and spars) using room temperature-curing adhesive bond. Also, to verify damage tolerance design of the wing structure, barely visible impact damages are intentionally created in the critical areas. The attachment fittings of the wing are fixed in a specially designed chamber which can simulate the low temperature environments of the operating altitudes. The test load is applied by hydraulic actuators which are placed outside the chamber. The structural tests consist of strain survey tests and a durability test for 1-life fatigue load spectrum. During the tests, strains of major parts are measured by strain gauges and FBG sensors. The change of the initial impact damages is also monitored using piezoelectric sensors. The 1-life damage tolerance of the composite structure is verified by the structural tests under the simulated environments.