Strength Factor

The Strength Factor option will plot the contours of the 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. All three principal stresses have an influence on the strength factor.

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.

In EX3, only materials with:

• Mohr-Coulomb
• Generalized Hoek-Brown
• Hoek-Brown

As the strength type are supported.

Calculating Strength Factor Results

It should be noted that Strength factor results are calculated after all other results and are not used in the main computation. As a result, strength definitions can be modified, and EX3 will automatically update the results accordingly to view the new strength factor results without performing other calculations

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.