Vol. 41 No.4 December 2010

20th Professor Chin Fung Kee Lecture

Dam Engineering: State of the Art and Practice, Observed Behavior and Future Challenges

by Prof. Dr. In. Pedro Seco e Pinto

Presented at the Auditorium Tan Sri Prof. Chin Fung Kee

ABSTRACT: It is important to analyze embankment dams behavior from the past lessons learned. It is noticed that modern embankment dams withstand the design earthquake without significant damages. In spite of this situation it is important to prevent the occurrence of incidents and accidents of embankment dams for static and seismic scenarios and so a deep understanding of the triggering factors is needed.

Well documented case histories from many parts of the world related with embankment dams behaviour, under static and seismic actions, were carefully selected and are discussed. The background of embankment dam engineering history is presented.

Based in the governed factors attention is given to the requirements for materials characterization.

The design and the analysis of dam stability under static and seismic conditions are addressed. The reservoir triggered earthquakes and the causative factors are discussed. Dam monitoring and inspections of dams are presented. Ageing effects and rehabilitation of dams are analysed.

The risks associated with dam projects are discussed. The benefits and concerns of dams are presented. It is important to develop new ways of thinking.

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Citation on Tan Sri Datuk Ir. Professor Dr. Chin Fung Kee
Biodata of Prof. Dr. In. Pedro Seco e Pinto
Abstract

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Dam Engineering: State of the Art and Practice, Observed Behavior and Future Challenges by Prof. Dr. In. Pedro Seco e Pinto

Vol. 41 No.4 December 2010

Response of Porous Seabed to Dynamic Loadings

D-S Jeng, X L Zhou, X D Luo, J H Wang, J Zhang and F P Gao

ABSTRACT: The evaluation of the seabed response, including pore pressure, effective stresses and shear stresses, is particularly important for coastal geotechnical engineers involved in the design of foundation around marine structures. This paper consists of two components. The first component focuses on analytical approximation for the seabed response, in which a new analytical solution for the seabed response due to combined wave and current loading is presented. Both transient and residual mechanisms are considered. Based on the new analytical solution, the effects of currents on the seabed response are examined and a modified J-S curve is presented. The second component will present an integrated model for ocean waves propagating over a submerged coastal structure. In the new model, Navier-Stoke equations, Biot’s poro-elastic theory, and structural mechanics theory are solved for wave propagation, seabed response and structure deformation, respectively. The new feature of this model is to integrate wave, soil and structure modes into one model within COMSOL Multiphysics environments. In this part, we first present the model of ocean wave generation over a porous seabed. Then we further consider two coastal engineering problems: (1) ocean waves propagating over a submerged breakwater on a porous seabed; and (2) waves over a deformable structure on a porous seabed, which can be applied to wave energy converter.

KEYWORDS: Response, Porous Seabed, Dynamic Loadings

DOI: 10.14456/seagj.2010.5

Vol. 41 No.4 December 2010

Engineering Protocols for the Assessment of the Net Moisture Flux at the Ground Surface

D. G. Fredlund, H. Q. Vu, J. Stianson

ABSTRACT: The assessment of moisture flux boundary conditions at the ground surface has proved to be important for the analysis of “real world” geotechnical engineering problem. There are several components that must be quantified in order to determine the net moisture flux entering the soil at the ground surface including: precipitation, runoff, actual evaporation and transpiration. Preferred methodologies are becoming apparent for calculating each of the components that lead to the calculation of the net moisture flux at the ground surface. The purpose of this paper is to set out general engineering protocols for the assessment of the net moisture flux at the ground surface. Examples are presented to illustrate the applications of moisture flux at the ground surface for geotechnical engineering problem; the examples include: i.) movement of slabs built on grade or at shallow depths below ground surface, ii.) triggering of slope instability as a results of water infiltration, and iii.) design and performance of soil cover systems.

KEYWORDS: Engineering Protocols, Assessment, Net Moisture Flux, Ground Surface

DOI: 10.14456/seagj.2010.1

Vol. 41 No.4 December 2010

Erosion, Slope Stability, Prediction of Future Recession in Actively Eroding Slopes

Tuncer B. Edil

ABSTRACT: Evolving slopes are those slopes subject to active erosion processes such that their morphology, thus their stability, is changing rapidly i.e., in human-time scale rather than geological-time scale. There may be several erosion processes but the most influential ones are related to the interactions with an external body of water such as wave action on coastal cliffs and bluffs (defined as steep slopes due to active erosion) such as along the shorelines of oceans, lakes, and reservoirs. The cost-effective solutions often are a combination of both stabilization and management approaches to minimize the impact. These concepts are presented based on the author‟s 35 years of experience observing and dealing with the bluffs along the shorelines of the Great Lakes (specifically Lakes Michigan and Superior). These lakes are subject to large lake level fluctuations and high waves, thus significant wave erosion takes place reshaping the bluffs and often leading to landslides. The state of knowledge with respect to shore erosion and associated bluff stability issues is presented including the available methods of predicting rate of erosion and determining bluff stability along with the controlling factors. The approaches to mitigating coastal recession are described. Finally, the environmental and ecological impact of coastal structures, which is gaining significant attention recently, is highlighted.

KEYWORDS: Erosion, Slope Stability, Prediction, Future Recession, Actively Eroding Slopes

DOI: 10.14456/seagj.2010.2

Vol. 41 No.4 December 2010

Living with Landslide Risk

S. Lacasse, F. Nadim and B. Kalsnes

ABSTRACT: Landslides represent a major threat to human life, property and constructed facilities, infrastructure and the environment in most mountainous and hilly regions of the world. Statistics from the Centre for Research on the Epidemiology of Disasters (CRED) show that landslides are responsible for at least 17% of all fatalities from natural hazards worldwide. The socio-economic impact of landslides is underestimated because landslides are usually not separated from other natural hazard triggers, such as extreme precipitation, earthquakes or floods. Many lives could have been saved if more had been known about the risks and risk mitigation measures had been implemented. The paper summarizes key aspects in the assessment of geological hazard and risk and exemplifies these with the risk associated with landslides and use appropriate risk mitigation strategies. Reducing the impact of landslide with mitigation measures is both an economical and social necessity.

KEYWORDS: Living, Landslide Risk

DOI: 10.14456/seagj.2010.4

Vol. 41 No.4 December 2010

Foundation Design of the Incheon Bridge

Sung-Min Cho

ABSTRACT: The Incheon Bridge, the longest bridge of Korea which was opened to the traffic in 2009, is an integration of several special featured bridges and the major part of the bridge consists of cable-stayed spans to cross the Yellow Sea. All the foundations consist of drilled shafts, large diameter bored pile foundations which were penetrated into the bedrock under the seabed. A single pile-bent type foundation system was selected as well as the pile-cap type foundations. New design scheme according to the LRFD (load & resistance factor design) specification was implemented for the project. The estimation of bearing capacity and settlement of rock socketted drilled shafts was carried out based on the understanding of the site condition, the ground properties and pile load test results. The results of the load tests were thoroughly analyzed by a number of experts to determine the resistance factor, giving a unique opportunity to improve the current LRFD concept in Korea. Geotextile tubes to block seawater were made to construct the foundation at the foreshore site whose tidal difference between ebb and flow was so large. Rip-raps which were designed by physical modeling and analysis are spread around the pile to prevent the scouring of the foundation. Circular dolphin structures made of the flat sheet piled wall and in-filled aggregates surround the piers near the navigation channel to protect the bridge against the collision with aberrant vessels. The structural design of the dolphin as a ship impact protection system was performed with numerical analyses of which constitutional model was verified by the physical model experiment using the geo-centrifugal testing equipment.

KEYWORDS: Foundation, Pile, Drilled shaft, Incheon Bridge, Geotextile Tube, Ship-Impact Protection

DOI: 10.14456/seagj.2010.3