GGU-RETAIN: Utilisation factor (buoyancy) using partial safety factors

Using the partial safety factor concept the following must be verified:

• Ak = the characteristic hydrostatic buoyant force acting on the lower surface of the
  complete structure, the soil layer in question or the excavation structure
• γg,dst = partial factor for destabilising permanent actions in the
  UPL (EC 7) limit state
• Gk,stb = lower characteristic value of stabilising permanent actions
• γg,stb = partial factor for stabilising permanent actions in the
  UPL (EC 7) limit state
• layer 1 (i = 1) is the uppermost layer

The so-called utilisation factor µ can also be calculated from this relationship.

• µN = utilisation factor of layer N

Utilisation factors ≤ 1.0 mean that sufficient safety is given.