A dam is a three dimensional structure and despite assumptions, it is not homogeneous and its integrity is in the hands of the constructors.
The factor of safety must relate to the strength, stability and durability with consideration to magnitude of economic and personal loss that would result from its failure.
- The foundations are neither isotropic or truly elastic.
- Concrete and rock are brittle, although elastic theories are applied in stress calculations.
- The dam and foundation will become saturated with varying effects on the materials.
- The dam will be subjected to water load, daily and seasonal temperature cycles.
- It will be subjected to random events such as : Floods, Waves, Seiche Effects, Earthquakes, Ice Formation and other natural phenomena.
The aim of the Engineer must be to reduce the number of uncertainties, both as regards loading on the dam and in the means by which the dam and the foundations withstand such loads. The Engineer must also be satisfied that there is no feasible mechanism that could result in failure.