Experiments on Stability of Tetrapods on Rear Slope of Rubble Mound Structures under Wave Overtopping Condition

In this study, hydraulic model tests were performed to investigate the stability of armor units at harbor side slope for rubble mound structures. The Korean design standard for harbor and fishery port suggested the design figures that showed the ratio of the armor weight for each location of rubble mound structures and it could be known that the same weight ratio was needed to the sea side and harbor side (within 0.5H from the minimum design water level) slope of rubble mound structures. The super structures were commonly applied to the design process of rubble mound structures in Korea and the investigation of the effects of super structures would be needed. The stability number (Nod = 0.5) was applied (van der Meer, 1999) and it showed that the armor (tetrapod) weight ratio for harbor side slope of rubble mound structures needed 0.8 times of that for sea side slope.

Risk analysis of construction diversion scheme

The determination of diversion risk in the construction of water conservancy and hydropower projects is a key problem related to the guarantee of project safety, saving project investment, giving full play to benefits in advance and facilitating construction. According to the design data, considering the influence of the uncertain factors such as hydrology and hydraulics, this paper analyses the relationship between the elevation of the upstream cofferdam and the upstream design water level, uses the Monte Carlo method to simulate the construction flood process and the discharge capacity of the diversion buildings, makes statistical analysis and determines the risk corresponding to the upstream water level distribution of the cofferdam and the water retaining height of the cofferdam, and establishes the calculation model of the construction diversion risk.

STUDY OF DESIGN WATER LEVEL ELEVATIONS IN HOTSPOTS OF HORMOZGAN COASTLINE

In this paper, design water level elevations due to wave, tide, wind and barometric pressure are calculated in hotspots including the ports of Kong, Lengeh, Shahid Rajaiee, Kuhmobarak, Sirik and Khuran. The effect of global water level rise is also considered. This modelling is performed utilizing MIKE21 developed by DHI Water and Environment. In order to calculate wave and tide setup, comprehensive and exhaustive studies of wave propagation and tidal levels modelling, which have been performed in last parts of Monitoring and Modeling Project of Coastal Zones of Hormozgan, are used. Also, wind-induced water level variations model is developed to calculate wind setup in various return periods. The results of the study present values of setup due to above mentioned phenomena which can be used in marine structures designs.

The Full Probabilistic Design Method of the Storm Surge Barrier Near the Port of Rotterdam, The Netherlands

After the storm surge disaster in 1953, which caused more than 1800 casualties in the Southwestern part of The Netherlands, a large dyke-strengthening and coastline-shortening programme was agreed upon and laid down by law. Work on the first projects commenced in the early sixties of the last century and the last phase of the programme was planned to start in 1990 and comprised of the dyke-strengthening programme in the Rhine Delta upstream from Rotterdam. This large project encountered growing public resistance as the required safety standards were established at the expense of both social and cultural values as well as ecological values. A feasibility study was started to ensure the required safety requirements of a storm surge barrier. The outcome was positive and the project was started in 1990 and was completed in 1996. In 1987, six contractors were invited to tender for the design and construction of a storm surge barrier, with only four “demand” specifications: (1) Reduction of the design water level in Rotterdam by 1.6 metres. (2) Reduction of the design water level 25 km (15 miles) upstream by 0.6 meter. (3) Lifetime of 100 years. (4) No obstacles to navigation. This set of requirements pertained to failure criteria. Based on this set of requirements, a full probabilistic method was adopted for the design of the storm surge barrier. A breakdown was made, starting from the basic probabilities of failure. The breakdown was based on failure trees with parallel and serial connected components and elements. In that way the design engineers were provided with centrally distributed failure criteria. This full probabilistic method, however, did not appeared to be adequate for several reasons. After a few months the full probabilistic design method was changed into a semi probabilistic method. Nevertheless, for the assessment of the load cases, a probabilistic approach was used, but for the design work on components and elements a traditional method introducing partial safety factors was used. Throughout the design period it was very difficult to prove that the actual designed system as well as, the designed sub systems and designed components met with the basic failure requirements. In order to avoid discussions, the designers embraced higher limits for their dimensioning calculations, resulting in a safer and more reliable storm surge barrier than was initially required.