Because IUCM uses a continuous Mohr–Coulomb approximation of the Hoek–Brown failure envelop, the shear strength reduction (SSR) mechanism can follow the conventional method for Factor of Safety (FoS) calculations in which the cohesive strength and friction angle are downgraded. The following modifications are made during each SSR trial:
- Cohesion ( c), friction angle (φ) and tensile strength (t) are downgraded for each zone in the model regardless of the state that they are (peak or residual), using these questions respectively:
- If anisotropic material exists, the above equations are used to downgrade the peak and residual ubiquitous joint properties (c, φ and t).
- If explicit faults are included in the model (2D interfaces), the interface properties are also downgraded following the same equations.
After each SSR trial, a DXF file of the failed volumes is exported. The failure criterion can be controlled by the user and is based on a displacement and velocity criteria. These DXF files can then be used to visualise the FoS of different parts of the pit in 3D as shown in Figure 6.
