In the Support Parameters dialog, the Support Installation options allow the user to define the point at which the support is installed, relative to the advancing tunnel face. This determines the origin of the support reaction curve on the rock-support interaction plot. There are three options for defining the Support Installation in RocSupport:
By defining the distance at which the support is installed from the advancing tunnel face. This value of distance is used in conjunction with a Longitudinal Deformation Profile to determine a value of tunnel convergence that corresponds to the specified distance.
The tunnel convergence can be specified directly.
The tunnel wall displacement can be specified directly.
Distance from Tunnel Face
If Support Installation = Distance from Tunnel Face, then you must enter the distance from the tunnel face at which the support is installed. The Distance from Tunnel Face is used in conjunction with a Longitudinal Deformation Profile function to determine a value of Tunnel Convergence at the point of Support Installation.
The default Longitudinal Deformation Profile (LDP) function which is used in RocSupport is shown in the figure below (Hoek, 1999).
If you do not wish to use the default LDP, the user can create their own customized deformation profile by selecting the Advanced button in the Support Parameters dialog. For details see the Longitudinal Deformation Profile topic.
NOTE: the Distance from Face can also be adjusted interactively and graphically, using the Tunnel Profile Icon displayed in the Ground Reaction View.
Tunnel wall displacement as a function of distance from face. From Hoek (1999).
Tunnel Convergence / Wall Displacement
The Support Installation can be specified directly as a value of Tunnel Convergence or Tunnel Wall Displacement, by selecting the second or third Support Installation options, and entering a value of convergence or displacement.
When either of these options are used, a Longitudinal Deformation Profile function is not required or used in the analysis.
NOTE: when Support Installation is specified directly by Tunnel Convergence or Tunnel Wall Displacement, the Tunnel Profile Icon and the Tunnel Face Marker options will not be available. These options are only applicable if the method of Support Installation = Distance from Face.