THE INFLUENCE OF SEISMIC LOAD IN SLAB AND EMBANKMENT OF CONCRETE FACE ROCKFILL DAM

Abstract

The objective of this study is to carry out the following: 1. To analyze the behavior of slab and embankment of concrete face rockfill dam under static load condition considering variation of slopes and dam heights. 2. To analyze the behavior of slab and embankment of concrete face rockfill dam under dynamic load condition using variation of peak accelerations at base of CFRD. 3. Conclusions are drawn concerning desirable slopes for concrete face rockfill dams under static load condition and under variation of seismic load. Concrete face rockfill dam of height 50 m and 100 m, located in a narrow valley with slope of wall at 1V:1H, have been used for the analyses purpose. The-typical section is shown in Figure 5.1. For both the height, the bottom width is fixed at 20 m. The dam has a water tight impervious layer placed on the upstream slope with a "cushion" layer of finer processed rockfill between the concrete face plate and the rockfill to provide uniform support for the face plate. Poorer quality rockfill has been used as secondary rockfill with zones of free draining rock incorporated to allow discharge of leakage. Should this occurs, as the rockfill is free draining, pore pressure do not develop in the dam and the upstream and the downstream slopes are commonly at the angle of repose of the rockfill_ hence the slopes or the angle of repose of upstream and downstream dam faces are varied from 1V:1.30H; 1V:1.35H; 1V:1.40H; 1V:1.45H and 1V:1.50H to study the effect of slope on the behavior of dam under static and dynamic load condition. Free board is kept as 5 m. The soil foundation for dam is included in analysis up to depth of 15 m. The dams usually are situated in irregular shapes of valley but to reduce the size of the problem, the valley profile has been assumed symmetrical about the centre line of the valley and, therefore, only a half of the dam has been considered in the analyses....