• Title/Summary/Keyword: Tidal Current Environment

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Effect of Wet Curing Duration on Long-Term Performance of Concrete in Tidal Zone of Marine Environment

  • Khanzadeh-Moradllo, Mehdi;Meshkini, Mohammad H.;Eslamdoost, Ehsan;Sadati, Seyedhamed;Shekarchi, Mohammad
    • International Journal of Concrete Structures and Materials
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    • v.9 no.4
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    • pp.487-498
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    • 2015
  • A proper initial curing is a very simple and inexpensive alternative to improve concrete cover quality and accordingly extend the service life of reinforced concrete structures exposed to aggressive species. A current study investigates the effect of wet curing duration on chloride penetration in plain and blended cement concretes which subjected to tidal exposure condition in south of Iran for 5 years. The results show that wet curing extension preserves concrete against high rate of chloride penetration at early ages and decreases the difference between initial and long-term diffusion coefficients due to improvement of concrete cover quality. But, as the length of exposure period to marine environment increased the effects of initial wet curing became less pronounced. Furthermore, a relationship is developed between wet curing time and diffusion coefficient at early ages and the effect of curing length on time-to-corrosion initiation of concrete is addressed.

Tidal depositional processes and late Quaternary (Holocene and pre Holocene) stratigraphy in the western coasts of Korea (한국 서해안 조수 퇴적과정과 제4기 후기(현세와 선현세) 층서)

  • 박용안
    • The Korean Journal of Quaternary Research
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    • v.9 no.1
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    • pp.33-42
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    • 1995
  • 우리나라의 서해(West Sea)는 일명 황해(Yellow Sea)라고 일컬어지는 약 40여 m의 평균 수심을 갖는 대륙붕 해저지형 분지에 의하여 지배되는 전형적 육연해이다, 그런데 이 바다는 중심부(황해의 중심부)를 기준으로 하여 중국 대륙의 산동반도에서 양가강 하구에 이르는 서부 해안을 가지며 북부에는 발해만의 해안이 있고 동부에는 서해(황해) 특유의 넓 은 조수환경(tidal environment)과 조수해안이 발달한다. 그러나 남쪽으로는 북서태평양과 연결된다. 한국 서해안이 평균 4m 이상의 조차(tidal range)를 나타내는 조간대 조수환경이 며 조간대 해저지형(intertidal morphology)이 전형적인 퇴적층(체)에 의하여 지배되는 여러 가지 특징을 나타낸다. 서해안 조수환경은 네델란드, 독일 또는 지배되는 여러 가지 특징을 나타낸다. 서해안 조수환경은 네델란드 독일 또는 미국의 경우와 같이 연구가 잘되어 세계 적으로 널리 알려진 소위 barrier island system and tidal depositional environments와는 크 게 다른 퇴적과정과 환경이다. 경기도 남양만의 조수 환경의 경우, 조간대 해저지형 요소인 조류로(tidal channel)와 조간대 정규해저(intertidal zone proper)에 관한 동력적 퇴적과정 연 구결과 조간대 특유의 lateral sedimentation 과 vertical sedimentation 2가지 퇴적과정중 후 자의 퇴적과정이 우세한 것으로 밝혀졌고 이러한 퇴적과정의 진행이 매우 안정한 지속성을 가지는 것이 특징이다, 이러한 퇴적과정의 조간대 퇴적물의 쇄설 입자는 약 20% 미만의 모 래(sand) 입자 50~70%의 실트(silt) 와 점토(clay) 입자가 20~30%에 달하는 입자조직 (grain texture)의 퇴적상을 나타낸다. 결과적으로 조간대의 동력적인 조수수괴의 수위(level of tidal water)는 평균 만조선과 평균 저조선으로 한정되며 이것은 퇴적과정과 퇴적작용의 조정(control) 요인으로 조간대 퇴적상의 발달과 분포에 큰 영향을 미친다, 예를들면 남양만 등의 대부분의 서해안 조간대 표층 퇴적상(녁\ulcorner미 sedimentary faci-es)은 만조선에서 간조 선에 가까울수록 조립화현상(coarsening trend)을 나타낸다. 이러한 퇴적상 변화는 저조선에 서 만조선으로의 조간대 지형과 주조수로의 지형.수력학적 특성이 다음과 같기 때문이다. a) a general decrease in width b) a general decrease in depth c) a general decrease in maximum and average current velocities d) a general increase in contents of suspended mud e) a general decrease in grain size of the bottom sand and an increasing abundance of muddy deposits. 우리나라 서해안 조간대 퇴적층(체)의 수직 층서(vertical stratigraphy)는 지난 3여년동안의 수십개의 vibracoring(주상시추)에 의하여 매우 흥미롭고 중요하게 밝혀지고 있는바 이것은 현세(Holocene)와 선현세(preHolocene: 11000 years BP)의 오랜시간 경과에 따른 조수환경 변화의 수직퇴적 과정과 기후 해수면 변화의 현상에 원인이 있다고 해석된다.(박용안 외, 1992-1995)결과적으로 서해안 조수퇴적체(층)의 분지주변(basim margin)진화과정이 밝혀지 고 있다.

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Study on Performance Variation According to the Arrangements of Adjacent Vertical-Axis Turbines for Tidal Current Energy Conversion (인접한 조류발전용 수직축 터빈의 배치방식에 따른 성능 변화)

  • Lee, Jeong-Ki;Hyun, Beom-Soo
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.19 no.2
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    • pp.151-158
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    • 2016
  • Tidal farm is a multi-arrayed turbine system for utilizing tidal stream energy. For horizontal-axis turbine(HAT) system, it is recommended that each unit has to be deployed far apart in order to avoid hydrodynamic interference among turbines, as proposed by the European Marine Energy Centre(EMEC). But there is no rule for the arrangement of vertical-axis turbine(VAT) yet. Moreover it has been reported that a proper arrangement of adjacent turbines can enhance the overall efficiency even greater than an arrangement without mutual interference effect. This paper suggests the layout of VATs showing the better performances, which turned out to be quite different from HATs' arrangement. Numerical calculations were performed to investigate the performance variation in terms of the rotational direction as well as the distance between turbines. It has been shown that the best combination of rotational direction and distance between turbines can increase its performance higher about 9.2% than that of two independently operated turbines. It is likely that such improvement is due to the increased velocity between adjacent turbines. For diagonally arranged turbines, the maximum normalized mean power coefficient was obtained to be higher about 5.6% than that of two independent turbines. It is expected that the present results can be utilized for conceptual design of tidal farm to harness the tidal stream energy.

Characteristics of Suspended Solids Movement in the Sand Recalmation of Breakwater (방파제 모래치환공사시 부유토사의 거동 특성)

  • Maeng, Jun-Ho;Lee, Ji-Wang;Kim, Byung-Jun;Ko, Jung-Yong;Yang, Gwon-Yeol
    • Journal of Environmental Impact Assessment
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    • v.9 no.2
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    • pp.127-142
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    • 2000
  • This research was performed for analyzing the transport of suspended solids during the harbor construction. In behalf of the research, we have analyzes the characteristics of suspended solids movement in sand reclamation of breakwater according to age of tide and tidal period at the construction spot of Pusan new harbor. In the process of sand reclamation, soil was dumped by a dumping device which direct soil from the barge to the bottom of the sea. According to the results from this research, suspended solid concentration was very high in the range of 5m from the dumping point right after the dumping. However these suspended solids settled very quickly and the solids concentration was very beyond 10m from the dumping point. It is deduced that the movement of solids dumped from barge has the tendencies as following; 1) Most of the dumped solids precipitated quickly after the dumping 2) The rest of the suspended solids are diffused slowly toward the bottom of the water being figured smoothing curve 3) The diffusion movement of suspended solids tend to proceed toward the shore line in a parallel motion with tidal current at the sea-bottom That is to say, most of the suspended solids precipitated very quickly even though highly concentrated solids produced at the bottom of the solids which did not precipitated spread with the tidal current horizontally along the bottom of the sea.

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Analysis of Marine Accident based on Impact of Tidal Stream and Vessel Tracking in VTS Are (VTS 관제 구역 내 조류의 영향과 항적 이동에 따른 해양 사고 분석 방법)

  • Kim, Joo-Sung;Jeong, Jung-Sik;Kang, Seung-Ho;Lim, Se-Wook
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2018.05a
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    • pp.246-247
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    • 2018
  • Since the routes within VTS areas include harbour limit of major ports, there are sections where the traffic volume increases and the routes are normally narrow according to the geographical conditions. In the case of ports and VTS areas located on the west coast of Korea, it is affected by strong current due to large tidal differences. In this paper, we propose a method to produce useful information according to the change of navigation environment by analyzing the characteristics of ship's movement according to tidal stream or current. The SVR seaway model, support vector regression, and grid search were conducted in order to extract models.

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A Plan of Spatial Data Modeling for Tidal Power Energy Development (조력에너지 개발을 위한 공간데이터 모델링 방안)

  • Oh, Jung-Hee;Choi, Hyun-Woo;Park, Jin-Soon;Lee, Kwang-Soo
    • Journal of the Korean Association of Geographic Information Studies
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    • v.14 no.3
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    • pp.22-35
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    • 2011
  • Incheon Bay has a suitable condition for tidal power generation due to the high tidal range by topographical effect. Therefore a study on the technology development for tidal energy utilization has been promoted since 2006. It is needed to deduce optimal alternatives to determine the suitable location of facilities for tidal power generation and to reduce the environmental damage from development. In order to carry out efficiently this mission, spatial information system is essential to manage and use various spacial elements related to the development and conservation. In this study, for the development of tidal energy, spatial data could be defined as three kinds of dataset. Fundamental dataset is defined as spatial data such as tide, tidal current, wave, erosion and sedimentation. Framework dataset is composed of topographical map, facility map and bathymetry. The reference dataset is composed of marine ecology and environment having the characteristics of thematic map. This study is mainly aimed at establishing methodology of conceptual spatial data modeling classifying as essential data model and optional data model through the definition of the components of spatial data.

Geochemical Indicators for the Recovery of Sediment Quality after the Abandonment of Oyster Crassostrea gigas Farming in South Korea (굴(Crassostrea gigas)양식 중단 이후 퇴적물 질 회복에 관한 지화학적 지표 탐색)

  • Sim, Bo-Ram;Kim, Hyung Chul;Kang, Sungchan;Lee, Dae-In;Hong, SokJin;Lee, Sang Heon;Kim, Yejin
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.53 no.5
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    • pp.773-783
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    • 2020
  • In order to evaluate the recovery of fishing ground environment after the cessation of aquaculture farming, we examined the variation in sediment quality over time using different geochemical factors and investigated whether these factors are indicators of sediment quality recovery. The study area was an oyster Crassostrea gigas, farm in Tongyeong, Geyongsangnam-do, South Korea, where aquaculture activities had been carried out for 20 years, and the changes in water and sediment environment were monitored for 14 months after the abandonment of the farm. The mean water depth was 14 m, with a tidal range of 3 m, and seawater current velocity ranged from 4.7 to 7.0 cm/s. After the abandonment of the farm, total organic carbon and total nitrogen concentrations in the surface sediments decreased significantly over time compared to those in the control site; in particular, immediately after farm abandonment, acid-volatile sulfide concentrations decreased relatively rapidly. Carbohydrate and protein concentrations in the sediments showed no significant changes; however, lipid concentrations markedly decreased. Further studies on other aquaculture taxa and various aquaculture areas are needed to establish new policies for environmental management of fishing grounds, such as relocation of fishing grounds and determination of optimal fallowing periods.

Simulation for Forecasting the Location of Drifting Objects at Sea Using SARMAP (SARMAP을 이용한 해상표류물체 위치예측 시뮬레이션)

  • Kim, Jung-Il;Lee, Han-Na;Kim, Kwang-Soo
    • Proceedings of KOSOMES biannual meeting
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    • 2007.05a
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    • pp.195-201
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    • 2007
  • In order to forecast the location of drifting objects at sea around Mokpo, Korea, the simulations were conducted with the input data of natural factors such as direction and force of wind and tidal current using SARMAP which is one of useful simulation tools for search and rescue at sea. Comparing the observed data with the calculated data of tidal currents used in SARMAP, the calculated tidal currents of SARMAP were in good agreement with the observed tidal currents. With regard to the case of marine casualties which occurred at sea around Daeheuksan-Do in July, 2006, the difference between the location of drifting body simulated by SAR model of Mokpo District Coast Guard and the location simulated by SARMAP was found to be about 20 nautical miles.

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Numerical Simulation for Net-water Flux of the Cross-sectional area in the Nakdong River Estuary (낙동강 하구역내 사주간의 단면유량플럭스 수치모의)

  • Yoon, Han-Sam;Lee, In-Cheol;Ryu, Cheong-Ro
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.8 no.4
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    • pp.186-192
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    • 2005
  • We investigated the deposition characteristics and mass transport flux estimation of the Nakdong estuary, Korea. To understand the effects of the tidal current circulation that influences estuary terrain changes, we used a 2D numerical model to map seawater circulation under three different situations, with the level of river flow being set as none or flood. The net-water flux of the cross-sectional area between sandbars (known as dung) was estimated. From our review of previous research, we know that the development of local sandbars shifted from the west to the east side of the estuary after the construction of the Nakdong River dike. Current development is occurring mostly at the Bakhap-dung near Tadea. The seawater circulation pattern over this large-scale area of tidal na is brings changes related to the quantity of the outflow from the Nakdong River. Based on the calculated results for the net-water flux of the cross-sectional area, we see very strong accumulation in local waters around Jangjiado, Bakhapdung, and Tadae under flood river flow conditions, but accumulation in local waters around Jinudo under the other states of flow. Consequently, in the Nakdong estuary, the main sensitive regions that are affected by changes in the flow of river discharge are the local waters around Jangiado, Bakhapdung, Tadae, and Jinudo.

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A landform change of barrier islands around the Nakdong River Estuary (낙동강 하구의 연안사주 지형변화)

  • Ban, Yong-Boo
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2009.06a
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    • pp.452-455
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    • 2009
  • The Nakdong Delta can be identified by two different geomorphic units. The first one is the upper delta. This is mostly composed of inter-distributary islands that are largely influenced by fluvial processes and attributed to the development of these islands along the river. The other one is the lower delta which is mostly composed of beach ridges. Barrier islands are largely effected by wave processes promoted by the development almost at a right angle to the river. Influenced by the longshore current which flows to the same direction, barrier islands located in the Nakdong river estuary are developing from east to west direction. As a result, the eastern end of the barrier islands are growing toward the north-west direction effected by tidal current which moves toward the same direction. Barrier islands include the Sinho Island, the Jinwoo Island, the Daema deung, the Janga Island, the Baghap deung, the Sae deung, and the Chulsae deung(Doyeo deung). They have orderly emerged from the sea since 1861. Since 2008, a new Deung, a sand dune growing under sea, has been developing rapidly from Chulsae deung to the Dadaepo beach. It made the sailing of small fisher boats impossible. Tidal currents transported a lot of sand and silt around the barrier islands. The landscape of Nakdong river estuary where many barrier islands are distributed will change rapidly affecting land environment.

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