Long-Term Ground Reaction
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 check box in the General tab of the Project Settings and enter a % reduction factor. his is the percentage by which the rock mass properties will be reduced, in order to determine the properties for the long term ground reaction curve. Depending on the solution method selected and the input option selected (i.e. cohesion or compressive strength), the reduction factor is applied to the peak cohesion, unconfined compressive strength of the rock mass, Young’s modulus of the rock mass, and unconfined compressive strength of intact rock. Residual values of the above variables are also factored.
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.