Why do arch dams require strong rock at their abutments?

Arch dams are thick shell structures that derive their strength from a curved profile, which transfers the immense thrust of water directly to the valley sides or through concrete abutments. Because the structural integrity of an arch dam is entirely dependent on this effective support, the abutments must be capable of resisting these significant forces without shifting.12

If the rock at the abutments is not sound, any movement or deformation can compromise the dam's stability, as the structure's rigidity makes it highly sensitive to such shifts. Consequently, engineers must conduct thorough rock mechanics investigations—utilizing techniques like field testing and theoretical analysis—to ensure that only sites with sound, stable rock are selected for construction.213