The RocSupport Solution Method computes the Ground Reaction Curve based on initial assumed material properties and loading conditions. To account for long term tunnel behaviour (e.g. rock mass property deterioration, re-establishment of groundwater regimes, creep, etc.), a strength reduction factor can be applied to obtain a long term Ground Reaction Curve (Hoek, 2003).
To plot the Long Term Ground Reaction curve, select the Plot Long Term Curve checkbox in Project Settings and enter a % reduction factor. The reduction factor will be applied to the rock properties as follows:
For the Duncan Fama Solution Method, the reduction factor is applied to the Compressive Strength of the rock mass, and to the Young’s Modulus.
For the Carranza-Torres Solution Method, the reduction factor is applied to the Compressive Strength of the intact rock, and to the Young’s modulus.
When the Plot Long Term Curve option is selected, the Ground Reaction view will display both the short term and long term ground reaction curves. Analysis results (e.g. safety factor, tunnel convergence) will be available for both the short term and the long term curves.