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Design of RCC Dams
Published in Nathalie Schauner, Icold Committee on Concrete Dams, 2020
In the economic feasibility evaluation of a dam, the volume of construction materials is a particularly important consideration. A gravity dam is an inefficient structure with respect to concrete volume, with much of the mass experiencing levels of stress at only a fraction of the concrete strength. Accordingly, where the site topography and geology allow, benefit in dam design can be realised in taking advantage of 3-dimensional load transfer to reduce the required volume of concrete. Unlike the gravity dam, for which RCC has now effectively globally replaced CVC as the optimal solution in all but exceptional circumstances, not all arch dam sites will be more suited to an RCC arch than a CVC arch. The topographical factors that increase the efficiency of an arch structure, typically a low crest length/height ratio and a narrow valley bottom, will tend to compromise the full achievement of the efficiencies associated with RCC, favouring vertical, rather than horizontal construction. Additional requirements for an arch, such as consolidation grouting on steep abutments, post-cooling and joint grouting, further compromise the time advantages of RCC construction. Accordingly, an optimum RCC arch can often involve a simpler, heavier section, which does not require post-cooling, or joint grouting before impoundment. As a consequence, RCC arch dams are typically more efficient solutions at sites best suited to an arch-gravity conFiguration (or a “thick arch”), in temperate climates and when constructed using low stress-relaxation creep RCC. All RCC arch dams to date have been constructed using HCRCC.
Hydromechanical analysis of gravity dam foundations
Published in António S. Cardoso, José L. Borges, Pedro A. Costa, António T. Gomes, José C. Marques, Castorina S. Vieira, Numerical Methods in Geotechnical Engineering IX, 2018
N. Monteiro Azevedo, M.L.B. Farinha, G. Mendonça, I. Cismasiu
A gravity dam, like other gravity structures, is designed so that the forces acting on the dam are primarily resisted by the dam’s self-weight (USACE 1983). The main loads in gravity dams are the self-weight and water pressures (hydraulic pressures and uplift). The typical cross section of a gravity dam is a triangle with a base-to-height ratio of 0.8, and thus the dam/foundation interface is very large. Uplift pressures at the base of the dam and hydraulic pressures play an important role, as they reduce the stabilizing effect of the structure weight. Such hydraulic pressures can occur in rock mass discontinuities or even in the dam body, if there is any deficiency in lift joints, or fissures in contact with the reservoir.
Hydromechanical analysis of gravity dam foundations
Published in António S. Cardoso, José L. Borges, Pedro A. Costa, António T. Gomes, José C. Marques, Castorina S. Vieira, Numerical Methods in Geotechnical Engineering IX, 2018
N. Monteiro Azevedo, M.L.B. Farinha, G. Mendonga, I. Cismasiu
A gravity dam, like other gravity structures, is designed so that the forces acting on the dam are primarily resisted by the dam’s self-weight (USACE 1983). The main loads in gravity dams are the self-weight and water pressures (hydraulic pressures and uplift). The typical cross section of a gravity dam is a triangle with a base-to-height ratio of 0.8, and thus the dam/foundation interface is very large. Uplift pressures at the base of the dam and hydraulic pressures play an important role, as they reduce the stabilizing effect of the structure weight. Such hydraulic pressures can occur in rock mass discontinuities or even in the dam body, if there is any deficiency in lift joints, or fissures in contact with the reservoir.
Comparison of homogenous and random fields of tensile strength effects on the nonlinear dynamical response of Guandi concrete gravity dams under strong earthquake waves
Published in Structure and Infrastructure Engineering, 2021
Xiang Lu, Liang Pei, Jiankang Chen, Zhenyu Wu, Zefa Li
Concrete gravity dams are critical components of a nation’s infrastructure and have been widely used in the world due to their simple structure, safety and reliability, and strong adaptability to geological conditions. In recent years, lots of concrete gravity dams have been or are being built in seismically active regions. In addition, different degrees of damage and cracking in concrete gravity dams have been produced under strong earthquakes (Chopra & Chakrabarti, 1972). The presence of damage or cracking impairs the durability and operational performance of concrete gravity dams. Therefore, the seismic safety of dams, especially dams in the alpine and gorge region with complicated geological conditions, is a critical problem that must be solved (Chen, 2009; Chen, Zhang, Xiao, & He, 2020; Wieland, 2010). Concrete gravity dams often exhibit strong nonlinear behaviours during an earthquake. The randomness of earthquake ground motions and material parameters affects the dams’ nonlinear dynamical response. Therefore, it is necessary to study the effect of randomness, especially damage and cracking, on the seismic response of gravity dams.
Influence of the Mechanical Properties of Masonry in the Structural Behavior of Gravity Dams
Published in International Journal of Architectural Heritage, 2022
Mostly, the structural assessment of gravity dams is performed by means of a gravity approach, where the resultant of all forces acting on the dam must lie in the third middle of the base. For both dams, the own weight plus the hydrostatic pressure considered as a triangular load (up to the crown of the dam) and the silt up to two-thirds of the total height of the dam were applied. The current conditions of the dams show that they have a large amount of silt, mainly for the lack of maintenance, which on average reaches two-thirds of the height of the dam. However, the influence of the height of the silt falls outside the scope of this work.
Industrial Heritage Assessment and Guidelines for the Architectural Conservation of Hydroelectric Plants
Published in International Journal of Architectural Heritage, 2021
The most crucial and distinctive element of a hydroelectric plant is the dam. Dams are constructed using various methods and materials, depending on the hydrologic properties, topography, geology, climate and seismicity of the surrounding, the availability of the materials and economic conditions. The three main categories are fill dams, masonry dams and concrete dams. Fill dams (earth-fill and rock-fill dams) are embankments constructed of compacted natural materials (earth or rock), and they rely mainly on their weight to counterbalance the thrust of water. Because of their wide-based triangular geometry, they are usually preferred in landscapes where the ground conditions are weak or heterogeneous and where the water level is low. There are cases where the upstream face of the embankment is covered with concrete slabs in order to provide impermeability. Masonry dams are structures built out of cut-stone or brick. Concrete dams are generally constructed of unreinforced blocks of concrete with flexible seals at the joints. Different types of masonry dams and concrete dams, according to their construction techniques, are gravity dams, buttress dams and arch dams. Gravity dams are structures which depend on their weights in order to resist the power of water acting on them. Therefore, they require strong ground conditions and well-designed foundations. Buttress dams also work with the same principle, except for the fact that in a buttress dam, the concrete slab is thinner and it is supported by a series of buttresses on the downstream side. Arch dams are curved structures with the top of the arch facing upstream so that the pressure of water compresses the structure which transfers the load to the sides of the valley through its abutments and to its foundation. Arch dams are constructed at narrow valleys where the sides of the canyon are stable and stiff. In many cases, arch dams are double-curvature structures, curved on horizontal and vertical planes similar to a section of a sphere (Figure 5). There are also cases — such as arch-gravity dams — where a combination of techniques is implemented.