A gravity dam resists both ______.

A gravity dam resists both ______.

• A. Lateral thrust and vertical stress
• B. Vertical thrust and lateral stress
• C. Forward thrust from the water and strain from its own weight
• D. Horizontal pressure of water and overturning by its own weight

Answer: (D)

Gravity dams stay stable because their own weight provides the resisting force against the water’s push. The water exerts hydrostatic pressure on the dam face, pushing horizontally (that’s the lateral thrust). To keep from tipping over, the dam relies on the weight acting downward to create a stabilizing moment about the base, counteracting the overturning moment produced by the water pressure. In other words, the dam is designed to withstand the horizontal pressure of the water and to resist overturning with its substantial weight. The vertical stresses that come from the dam’s weight are a consequence of its mass, not the primary resisting mechanism in this context. The idea that a gravity dam resists horizontal water pressure and overturning by its own weight best fits how these structures achieve stability.

Gravity dams stay stable because their own weight provides the resisting force against the water’s push. The water exerts hydrostatic pressure on the dam face, pushing horizontally (that’s the lateral thrust). To keep from tipping over, the dam relies on the weight acting downward to create a stabilizing moment about the base, counteracting the overturning moment produced by the water pressure. In other words, the dam is designed to withstand the horizontal pressure of the water and to resist overturning with its substantial weight. The vertical stresses that come from the dam’s weight are a consequence of its mass, not the primary resisting mechanism in this context. The idea that a gravity dam resists horizontal water pressure and overturning by its own weight best fits how these structures achieve stability.