Analysis of Internal Stability
Internal stability of a structure is checked assuming two types of a slip surface:
- Plane slip surface
Plane slip surface
- Broken slip surface
Broken slip surface
In both cases, a specific slip surface is examined for a variation of angle ϑ.
When running an optimization analysis the calculation is carried out for all benches with a variation of the angle of slip surface ν changing from 1 up to 89 degrees with a one-degree step.
The analysis checks whether a ratio of resisting and shear (driving) forces acting on a slip surface is greater than the input factor of safety. The following forces are employed:
- component of gravity force parallel to slip surface
- in case of broken slip surface - component of active earth pressure acting on the vertical part of structure and parallel to slip surface (pressure is determined without reduction of input parameters)
- horizontal forces due to earthquake
- soil friction and cohesion along the slip surface
- sum of the forces transmitted by nails