What are the stability requirements for gravity dams?

Gravity dam stability checks: (1) Overturning - factor of safety (resisting moment/overturning moment) > 1.5 for normal, > 1.2 for extreme loads, (2) Sliding - friction resistance plus shear key resistance > driving forces, FOS > 1.5, (3) Stress - maximum compression < allowable (0.3f'c), no tension at heel (or limited tension with drain effectiveness), (4) Base pressure within foundation capacity. Loading conditions include: normal (dead load, water, uplift), unusual (ice, silt), and extreme (earthquake, maximum flood). Uplift reduced by drainage systems.