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Which forces must engineers consider when designing a concrete gravity dam?
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Itaipú Dam on the Upper Paraná River, north of Ciudad del Este, Paraguay.
When designing a concrete gravity dam, engineers must account for several critical forces to ensure the structure remains stable and resists overturning or sliding. The three primary forces are:12
- Weight of the dam: The structure is proportioned to resist external forces entirely through its own mass.12
- Thrust of stored water: The horizontal pressure exerted by the reservoir against the upstream face.12
- Foundation pressure: The reaction force exerted by the ground supporting the dam.12
Additionally, engineers must consider several secondary but essential factors:
- Uplift force: Buoyant pressure from water seeping under the dam or into horizontal joints, which can destabilize the structure.12
- Silt and ice thrust: Pressure exerted on the upstream face by deposited silt or surface ice.12
- Inertial forces: Stresses caused by seismic activity.12
To manage these forces, designers often employ systems such as grouting to seal fissured rock, underdrainage to relieve uplift pressure, and spillways to safely manage floodwaters. In some cases, posttensioned steel is used to further strengthen the structure against overturning.12