Final answer:
The factor of safety equation for excavation is: Factor of Safety = Ultimate Load / Working Load.
Step-by-step explanation:
The correct equation for the factor of safety for excavation is:
Factor of Safety = Ultimate Load / Working Load
In this equation, the ultimate load refers to the maximum load that the excavation can withstand without failing, while the working load refers to the load that is actually being applied to the excavation. The factor of safety is a measure of how much stronger the excavation is compared to the working load.