저장시설의 순간 전량 방출 시 방류벽의 월파 효과에 대한 수치모델링

민동석,박천탁,정승호 한국화학공학회 2019 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.57 No.7

As the industry develops in Korea, the use of hazardous chemicals is increasing rapidly and chemical accidents are increasing accordingly. Most of the chemical accidents are caused by leaks of hazardous chemicals, but there are also accidents in which all the substances are released instantaneously due to sudden high temperature/pressure or defection of the storage tanks. This is called catastrophic failure and its frequency is very low, but consequence is very huge when it occurs. In Korea, there were 15 casualties including three deaths due to catastrophic rupture of water tank in 2013, and 64 instances of failures from 1919 to 2004 worldwide. In case of catastrophic failure, it would be able to overflow outside the bund that reduces the evaporation rate and following consequence. This incident is called overtopping. Overseas, some researchers have been studying the amount of external overflow depending on bund conditions in the event of such an accident. Based on the previous research, this study identified overtopping fraction by condition of bund in accordance with Korea Chemicals Controls Act Using CFD simulation. As a result, as the height increases and the distance to the facility decreases while meeting the minimum standard of the bund capacity, the overtopping effect has decreased. In addition, by identifying the effects of overtopping according to atmospheric conditions, types of materials and shapes of bunds, this study proposes the design of the bund considering the effect of overtopping caused by catastrophic failure with different bund conditions. 국내 산업이 발전함에 따라 유해화학물질의 사용이 급속도로 증가하고 있고, 이에 따른 화학사고 역시 증가하고 있다. 대부분의 화학사고는 저장시설에서 화학물질의 누출로 인해 발생하지만, 갑작스러운 고온·고압으로 인해 저장시설이파열됨으로써 내부의 물질이 순간적으로 방출되는 사고 역시 발생하고 있다. 이것을 catastrophic failure라고 부르며 그빈도는 매우 낮지만, 발생했을 때 피해 규모는 매우 크다. 국내에서는 2013년 울산의 한 현장에서 물탱크의 파열로 인해 3명의 사망자를 포함한 15명의 사상자가 발생하였고, 전 세계적으로 1919년부터 2004년까지 저장시설의 순간 전량 방출 사고가 64건 발생하였다. 저장시설에서 위험물질이 누출될 경우 외부로의 확산을 방지하는 방류벽이 존재하지만, 저장시설의 파괴로 물질이 순간적으로 방출되는 경우 내부 물질이 방류벽 바깥으로 넘치는 현상이 발생한다. 이를 월파 현상 또는 overtopping 이라 한다. 해외에서는 저장시설의 순간 전량 방출 사고에 따른 overtopping 효과를 실험을 통해 연구해왔다. 본 연구에서는 선행연구를 바탕으로 전산유체역학(CFD) 시뮬레이션을 이용하여 국내 규정을준수하는 방류벽의 설계 조건별 overtopping 효과를 확인해 보았다. 그 결과, 방류벽 용량의 최소기준을 만족한 상태에서 높이가 높아지고 설비와의 거리가 가까워짐에 따라 내부 물질이 방류벽 외부로 빠져나가는 현상은 줄어들었다. 추가로 대기조건 및 물질의 종류, 방류벽 형상에 따른 overtopping의 효과를 확인함으로써, 순간 전량 방출 사고의 피해를 고려한 방류벽의 설계 방향 및 저감 대책을 제시하고자 한다.

Mapping Risk of Levee Overtopping Using LiDAR Data: A Case Study in Nakdong River Basins, South Korea

정윤재 대한토목학회 2015 KSCE Journal of Civil Engineering Vol.19 No.2

Overtopping occurs when the flood water’s level is greater than the levee’s height. Mapping risk of levee overtopping is efficientfor assessing levee stability, generating flood hazard maps and planning flooding management. This paper proposes a methodologyfor mapping the risk of levee overtopping using the topographic Light Detection and Ranging (LiDAR) data taken in Nakdong RiverBasins, South Korea. The procedure is as follows: A slope map is generated from the LiDAR data, then the levee crown polygonsand the riverside levee boundaries are extracted from the slope map by using the levee crown detection method. The levee crownsegments with the risk of overtopping are identified using the values of the average height of the levee crown polygon, the designedflood level, and the freeboard. Next, different-colored levee boundaries are generated to show the risk of overtopping on each leveecrown segment. Finally, the areas with the height lower than the designed flood level are shown on the levee crown surfaces as thered points. In this research, the risk of overtopping on the two levees (Jungsan Levee and Daesan Levee) parallel to the NakdongRiver’s mainstream are assessed by using the proposed methodology. This research shows that Jungsan Levee do not have the risk ofovertopping, while Daesan Levee has the risk of overtopping.

Development of Wave Overtopping–Overflow Transition Model Based on Full-scale Experiments

Hajime Mase,Sooyoul Kim,Makoto Hasegawa,Jae-Hoon Jeong,윤종성 한국해양공학회 2020 韓國海洋工學會誌 Vol.34 No.2

When high waves and storm surge strike simultaneously, the characteristics of the fluid field change drastically from overtopping according to the wave runup height to overflow through a transition state that combines overtopping and overflows. However, an estimation model or evaluation method has not yet been established because there is not enough engineering data. This study developed a wave overtopping-overflow transition model based on a full-scale experiment involving wave overtopping and overflow transition, which appropriately reproduced the effect of waves or the temporal change in inundation flow. Using this model to perform a calculation for the wave overtopping and overflow transition process under typical circumstances, this study determined the wave runup height and features of the inundation flow under time series changes as an example.

부유식 차수 구조물을 활용한 월파 능동제어 시스템[AWOC] 개발

조용준 (사)한국연안방재학회 2022 한국연안방재학회지 Vol.9 No.3

In this study, an active overtopping control system [AWOC] that could effectively supress the flooding caused by storm surge was presented, and numerical simulations to verify the overtopping control effect of AWOC were also carried out using OlaFlow, an OpenFoam-based toolbox. In the AWOC, the floating structure that works as the overtopping controller is submerged in a mild sea, and when exposed to a storm, it rises when the sea level are getting increased due to a storm surge, and as a result, would effectively supress the wave-induced overtopping. Due to these characteristics, the AWOC has the advantage of controlling overtopping at the minimum opportunity cost to preserve the beautiful beach landscape. In the numerical simulation, the motion of a floating structure that rises or descends coupled with the sea level during a storm surge or harsh waves was described by solving the structure motion equation using the water pressure acting on it as an external force. In doing so, Dynamic Mesh was used for the sake of more accurate numerical simulation, in which the computational mesh is updated whenever floating structure moves. Numerical result shows that even though overtopping flow becomes more energetic compared to that in the rubble-mound breaker due to the emhanced reflection after the deployment of AWOC, AWOC could effectively control the enhanced overtopping. It is also shown that an obliquely descending flow from the first quadrant to the third quadrant is formed in the front of AWOC due to the offshore-directed flow commencing from the floating structure of AWOC.

월류에 의한 저수지 제체의 붕괴 거동

이달원(Dal-Won Lee),노재진(Jae-Jin Noh) 충남대학교 농업과학연구소 2012 농업과학연구 Vol.39 No.3

In this study, an experiment with large-scale model was performed according to raising embankment in order to investigate the behaviour of failure due to overtopping. The pore water pressure, earth pressure and settlement by high water level, a rapid drawdown and overtopping were compared and analyzed. Also, seepage analysis and slope stability analysis were performed for steady state and transient conditions. The pore water pressure and earth pressure for inclined core type showed high value at the base of the core, but they showed no infiltration by leakage. The pore water pressure and earth pressure by overtopping increased at the upstream slope and core, it is considered a useful data that can accurately estimate the possibility of failure of the reservoir. The behavior of failure due to overtopping was gradually enlarged towards the downstream slope from reservoir crest, and the inclined core after the raising embankment was influenced significantly to prevent the reservoir failure. The pore water pressure distribution for steady state and transient condition showed positive (+) pore water pressure on the upstream slope, it was gradually changed negative (-) pore water pressure on the downstream slope. The pore water pressure by overtopping showed a larger than the high water level at the downstream slope, it was likely to be the piping phenomenon because the hydraulic gradients showed largely at the inclined core and reservoir crest. The safety factor showed high at the steady state, and transient conditions did not show differences depending on the rapid drawdown.

노후화된 균일형 저수지 제체의 월류모형실험과 3차원 침투특성

이영학,이태호,이달원 한국농공학회 2019 한국농공학회논문집 Vol.61 No.2

In this study, an overtopping model experiments and three dimensional seepage characteristics at the deteriorated homogeneous reservoirs wereperformed to investigate the behavior of failure for embankment and spillway transitional zone due to overtopping. The failure pattern, pore waterpressure, earth pressure and settlement by overtopping were compared and analyzed. The pattern of the failure by overtopping was gradually enlargedtowards reservoirs crest from the spillway transition zone at initial stage. In the rapid stage and peak stage, the width and depth of failure graduallyincreased, and the pattern of the failure appeared irregular and several direction of the erosion. In the early stage, the pore water pressure at spillwaytransitional zone was more affected as its variation and failure width increased. In the peak stage, the pore water pressure was significantly increasedin all locations due to the influence of seepage. The earth pressure increased gradually according to overtopping stage. The pore pressure by thenumerical analysis was larger than the experimental value, and the analysis was more likely to increase steadily without any apparent variation. Thehorizontal and vertical displacements were the largest at the toe of slope and at the top of the dam crest, respectively. The results of this displacementdistribution can be applied as a basis for determining the position of reinforcement at the downstream slope and the crest. The collapse in theovertopping stage began with erosion of the most vulnerable parts of the dam crest, and the embankment was completely collapsed as the overtoppingstage increased.

농업용 저수지 월류시 제체와 여수토 접속부의 붕괴거동

노재진,이달원,Noh, Jae Jin,Lee, Dal Won 한국농공학회 2014 한국농공학회논문집 Vol.56 No.1

In this study, an experiment with large-scale model was performed according to raising the embankment in order to investigate the behavior of failure for embankment and spillway transitional zone due to overtopping. The pore water pressure, earth pressure, settlement and failure pattern by a rapid drawdown and overtopping were compared and analyzed. The pore water pressure and earth pressure at spillway transitional zone by overtopping increased a rapidly with the expansion of seepage erosion, but the crest showed a smally change due to effect of the inclined core type. And it is considered an useful data that can accurately estimate the possibility of failure of the reservoirs. A settlement at overtopping decreased a rapidly due to failure of crest. The relative settlement difference due to change of the water level at the upstream and downstream slope cause increase largely crack of crest. The behavior of failure by overtopping was gradually enlarged towards reservoirs crest from the bottom of the spillway transition zone, the inclined core after the raising the embankment was influenced significantly to prevent the seepage erosion.

Riprap으로 보강된 농업용 저수지 제체의 붕괴거동

이달원,노재진,Lee, Dal Won,Noh, Jae Jin 한국농공학회 2014 한국농공학회논문집 Vol.56 No.6

In this study, the large scale test was performed to investigate the behavior of failure on the embankment and spillway transitional zone by overtopping. The pore water pressure, earth pressure, settlement and failure behaviors according to several reinforcing method were compared and analyzed. The pore water pressure showed a small change in the spillway transition zone and core, indicating that the riprap and geotextile efficiently reinforced the embankment, but non-reinforcement showed a largely change in pore water pressure. The earth pressure by riprap and geotextile at upstream slope and bottom core increased rapidly with the infiltration of the pore water by overtopping. And the earth pressure at crest showed a smally change due to effect of the inclined core. A settlement by riprap showed a small change and the geotextile decreased a rapidly due to failure of crest. The width of failure by riprap at intermediate stage (50 min) showed a largely due to sliding of crest. But, the width and depth of the seepage erosion after the intermediate overtopping period (100 min) were very small due to the effect of riprap than geotextile and non-reinforcement which delayed failure. It has the effect that protect reservoir embankment from erosion in the central part. The pore water pressure at the spillway transition zone due to overtopping increased a rapidly in the case of non-reinforcement, but the reinforced methods by geotextile and riprap showed a smally change. Therefore, the reinforced method by riprap and geotextile was a very effective method to protect permanently and the emergency an embankment due to overtopping, respectively.

방파제의 월파에 의한 항내 정온도 변화 연구

이상화(Sang-Hwa Lee),장은철(Eun-Cheul Jang) 동아대학교 해양자원연구소 2007 동아대학교 해양자원연구소 연구논문집 Vol.19 No.-

  Wave overtopping has been studied under the view of its reducing capability of the various wave dissipating structures.<BR>  Therefore, researches for the effect of harbour tranquility caused wave overtopping are insufficient. In this study, it was analyzed the effect of harbor tranquility by wave overtopping of breakwater concerning design wave through a three dimensional hydraulic model test. The averaged significant wave height is distributed as 2.16m in permitted wave overtopping, 1.63m in not permitted. The decreased wave height is shown as 50㎝ and 24% of desigh wave height in not permitted wave overtopping.

Centrifugal Model Test on the Failure Mechanism of Barrier Dam Overtopping

Tianlong Zhao,Shengshui Chen,Changjing Fu,Qiming Zhong 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.4

In order to study the failure mechanism of barrier dam overtopping, centrifugal model tests of dam failure were conducted in this research. A calculation method of rectangular weir flow in the centrifugal field was derived. The process and mechanism of barrier dam overtopping were intensively analyzed. They were further verified by the breach flow curve and the development curve of the breach top width acquired from model tests. Results showed that the barrier dam breach developed during the entire process of overtopping in the width direction. The development of the barrier dam breach in the depth direction, however, ceased at an earlier time on account of the large particles accumulated in the downstream slope. Moreover, coarsening in the downstream slope could be clearly observed in the last stage of overtopping. Thus, it was concluded that the bottom part of the barrier dam could survive after dam breaching and that a full dam failure is relatively rare for a barrier dam. Furthermore, the size of the remaining breach would be less than that of a homogeneous earth dam under the same conditions.