In the construction of RCC dams, the mixture is placed and roller compacted with the same commonly available equipment used for asphalt pavement construction. Mass concrete construction remains a semicontinuous and labor-intensive operation of low overall productivity and efficiency. Progressive reductions in cement content and partial replacement of cement with pulverized fuel ash (PFA) have served only to contain the problem. RCC (roller compact concrete) dams: The volume instability of mass concrete due to thermal effects imposes severe limitations on the size and rate of concrete pour, causing disruption and delay because of the need to provide contraction joints and similar design features ( Figure 18). In this study, dam break analysis is performed for a distance of ~ 21 km downstream of the dam. The mean annual rainfall and temperature of the study area are ~ 1200 mm and 16☌, respectively. In the catchment, the main land use is olive groves and rice paddies. The main highway of Tehran-Rasht passes close to these cities. The most important cities and villages downstream of the dam are Aliabad-e-Paein, Roudbar, dolatabad, Ganjeh, Jouben, Tutkabon, and Rostamabad at distances of 0.4, 5.8, 12, 14, 17, 20, and 20 km downstream of the dam, respectively. The dam consists of two glory hole spillways, two lateral spillways, and five gates and is constructed on the Sefid-Roud River (the second largest river in Iran) where the two rivers (Shahroud and Qilzil Ouzan rivers) combine ( Fig. The total volume of output discharge from the dam is estimated as ~ 6000 m 3/s. The dam is Buttress-Gravity-Dam with a wall height of 106 m, crest length of 425 m, crest width of 8 m, and reservoir volume of 1198 million m 3. Sefid-Roud Dam is located in a Giulan province, Iran. Whatever may be the results of the theoretical analyses of forces and stresses on the dam, sufficient reserve strength must be included in the design to meet unknown weaknesses. However, the stresses in the concrete of the dam and in the foundations and abutments can be very high, so that the utmost care needs to be taken in the site investigations and in the design and the construction. Arch concrete dams are among the highest in the world and are inherently stable when the foundations and abutments are solid and watertight. River and flood diversions are usually taken in tunnels through the abutments flood overspill may be passed over a central spillway. A dam of this kind is called a double curvature dam and is especially economical in the use of concrete. There are many variations from the simple uniform arch shape the most economic section is curved both vertically and horizontally and results in the horizontal arches varying in radii with level. Physical models have also been used to measure strains and to give a first approximation to the likely distribution of stresses, and to then act as a check on the mathematical calculations. The modern method is to construct a three-dimensional finite element model of the dam to evaluate stresses under various loadings. The water load at each point was then divided between the ‘cantilevers’ and ‘arches’ so that their deflections at every point matched. The dam was assumed to consist of unit width cantilevers one way and unit width arches the other. Early designs were based on the ‘trial load’ procedure. An arch dam acts in compression and can be much thinner than a gravity dam – e.g. The theory of design is complex, with the dam resisting the water thrust partly by cantilever action from the base and partly by arching action from abutment to abutment. The abutments must therefore be completely sound. The majority of the strength required to resist the water thrust is obtained by arching the dam upstream and transferring the load to the abutments. The principle of design of an arch dam is greatly different from that of a gravity dam. Ratnayaka BSc, DIC, MSc, FIChemE, FCIWEM, in Twort's Water Supply (Seventh Edition), 2017 5.15 Arch Dam Design
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