Strength Factor

The Strength Factor option will plot contours of strength factor around the excavation(s).

The strength factor is calculated by dividing the rock strength (based on your failure criteria) by the induced stress at every point in the mesh. All three principal stresses have an influence on the strength factor (Sigma 1, Sigma 3 and Sigma 3), so the strength factor in RS3 can be considered 3-dimensional.

In the case of Elastic materials, the strength factor can be less than unity, since overstressing is allowed. In the case of Plastic materials, the strength factor is always greater than or equal to unity.

The following document gives the equations used to calculate Strength Factor in RS3, and also the calculation of the Number of Load steps: Strength Factor Equations .

Tension

When Tension is indicated in the strength factor contours, this means that Sigma 3 is less than the calculated negative stress (Tension) cutoff for the failure criterion in use.