Explanation Gravity Dams ● It is a masonry structure that increases stability against all applied loads by its weight alone. ● It is a permanent type of dam. ● It is mostly straight in plan and approximately triangular in cross-section. ● The thickness of the dam provides resistance to sliding.
Forces acting on a gravity dam:
1. Dead load or self-weight of the dam ● Includes weight of concrete and accessories like piers, gates, bridges, etc. ● It is the main stabilizing force. ● Acts vertically downwards. 2. Water pressure ● Major external force. ● When the dam is horizontal, acts horizontally and intensity varies with depth. 3. Uplift pressure ● Occurs due to internal hydraulic pressure in pores, cracks within the body of the dam. ● Assumed to vary linearlyfrom full reservoir pressure at upstream face to zero or tailwater pressure at downstream face. 4. Earthquake forces ● Generates due to earthquake waves in the earth's crust. ● These waves impart accelerations and cause movement of the foundation of the dam. 5. Silt Pressure ● Occurs when dams are constructed across the river carrying sediments. 6. Ice pressure ● Important in cold countries where ice formed on the water surface of the reservoir subjected to expansion and contraction. 7. Wave pressure ● Due to the generation of waves on the surface by blowing winds. Note: All the forces due to water, wave, uplift, etc. are resisted by the weight of the dam