The Solution Method is used to compute the Ground Reaction Curve in RocSupport. In the Project Settings dialog, you may select from two different Solution Methods:
Duncan Fama solution Duncan Fama (1993)
Carranza-Torres solution Carranza-Torres (2004).
Both are closed-form solutions, but with slightly different approaches and assumptions. The Duncan Fama solution is based on the Mohr-Coulomb failure criterion of the rock mass, while the Carranza-Torres solution is based on the Hoek-Brown criterion. The latter also takes dilation and residual strength properties into consideration. See the references for details.
The required rock mass data is different for both solutions. Therefore, if you switch from one Solution Method to another, the program will re-display the Tunnel and Rock Parameters dialog, to ensure that the appropriate data is entered.