Sigra uses limit state models to assess most slopes. It is found that these give adequate solutions, and that the additional effort in using finite element analysis is seldom justified.
The two dimensional limit state soil slope model is based on a Janbu type solution.
It is supported by a three dimensional version, which is especially useful in determining the zones of the potential failure that are most in need of attention. This version may be used integrally with the Sigra groundwater model for inflow on a slope.
The model may be run on its own or with real time groundwater inputs to yield a real time factor of safety for a slope.
Sigra also has a number of wedge and planar failure models for use on rock slopes.
In addition the company has developed a model to determine the spacing of sub horizontal drains in a slope.