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Dams
Published in Mohammad Albaji, Introduction to Water Engineering, Hydrology, and Irrigation, 2022
A cofferdam is a (usually temporary) barrier constructed to exclude water from an area that is normally submerged. Made commonly of wood, concrete, or steel sheet piling, cofferdams are used to allow construction on the foundation of permanent dams, bridges, and similar structures. When the project is completed, the cofferdam may be demolished or removed. See also causeway and retaining wall. Common uses for cofferdams include construction and repair of offshore oil platforms. In such cases, the cofferdam is fabricated from sheet steel and welded into place under water. Air is pumped into the space, displacing the water allowing a dry work environment below the surface. Upon completion, the cofferdam is usually deconstructed unless the area requires continuous maintenance (Figure 3.10).
Introduction to Civil Engineering
Published in P.K. Jayasree, K Balan, V Rani, Practical Civil Engineering, 2021
P.K. Jayasree, K Balan, V Rani
There are different types of dams classified based on function and construction material. Based on the material of construction, dams are categorized as earthen dam, masonry dam, and concrete dam. Based on the function of dams, they are categorized as storage dam, flood control dam, diversion dam, and coffer dam. A storage dam is constructed for water storage. The stored water may be used for drinking, irrigation, or hydroelectric power generation. A flood control dam is constructed for the temporary storage of flood water and then to discharge it gently so that the downstream side is shielded against the destructive effects of floods. A diversion dam is constructed to divert water from a river to a channel for irrigation. A cofferdam is a temporary structure constructed to divert water so that a safe construction area can be prepared during the construction of bridges and other underwater constructions.
Safety by design – the new intake at John Hart generating station project
Published in Jean-Pierre Tournier, Tony Bennett, Johanne Bibeau, Sustainable and Safe Dams Around the World, 2019
A.V. Maiorov, A. Kartawidjaja, K. Gdela
The cofferdam was designed and constructed using interlocking hollow steel pipe piles driven into bedrock and a steel bracing system installed at the top of the pile wall, above the water level. The structure created a temporary dry enclosed area, allowing adequate space for construction activities associated with building the maintenance gate structure upstream of block 2. The cofferdam was equipped with 2 sealing cells at both ends, adjacent to blocks 1 and 3 and connecting to the dam, to prevent water leakage at the interfaces. Design of the bracing system considered construction access requirements and was optimized without compromising construction safety and ensuring structural stability of the cofferdam and the adjacent earth fill dam. Finite element (FE) based structural analyses were used to design the cofferdam and the bracing system for all anticipated construction stages. These analyses also allowed the designers to benchmark deformation measurements for safety monitoring during dewatering and the construction period. An example of the FE analysis of the cofferdam model is shown in Figure 5.
Mechanical properties of film-bag sand cofferdam: theoretical analysis and numerical study
Published in Journal of Asian Architecture and Building Engineering, 2023
Bo Feng, Chun-Yuan Zhang, Xing-Jin Wang, Yong-Jiu Qian
With the gradual exploration of the marine environment, China’s marine engineering construction has been gradually strengthened, and the construction technology in various marine environments has been continuously developed, among which the land-blowing technology has also been developed significantly. In the construction of coastal ports, submarine tunnels, cross-sea bridges, and other projects, it is often necessary to build temporary enclosure structures before the main project construction. The sand-blown cofferdams are widely used in the construction of temporary cofferdams in near-shore harbors and wharves of rivers, lakes, and seas due to their advantages of convenient construction, less pollution, high mechanization, and easy dismantling (Kang et al. 2020). According to the filling materials, the traditional cofferdams can be divided into earth and stone, wooden cage, sheet pile lattice, reinforced concrete, timber sheet pile as well as pile wall frame structure cofferdams (Xue et al. 2019; Wang, Liang, and Peng 2020).
Design of large geotextile mat cofferdam over deep soft clay
Published in Marine Georesources & Geotechnology, 2023
Xiaoliang Wang, Xiaowen Zhou, Mi Zhou, Yuxia Hu
After obtaining the limiting fill height of the cofferdam, it is important to evaluate the factor of safety of a cofferdam where its design fill height is less than the limiting fill height. Based on the work by Dawson, Roth, and Drescher (1999) Griffiths and Lane (1999), and Dong et al. (2023), the shear strength reduction finite element method has been widely exploited and applied in 2-D plane strain analysis to predict the factor of safety for slope stability. With the shear strength reduction technique, the shear strength is decreased by reducing the values of the two parameters (Zhang et al. 2015), cr = c/Fs, tanφr = tanφ/Fs, where cr is the reduced cohesion, φr is the reduced friction angle, and Fs is the factor of safety. In this study, the linear reduction of a field parameter which related to the reduced shear strength and frictional angle were used to simulate the strength reduction effect, then the simulation will stop at a certain value of the field parameter (or step time) due to nonconvergence. The factor of safety can be obtained by interpolating the field parameter on step time.