Ground Reaction View

The Ground Reaction View displays the primary results of a RocSupport analysis - the Ground Reaction Curve, the Support Reaction curve, and analysis results (e.g. final tunnel convergence and safety factor).

• The ground reaction curve (GRC) is always displayed in the Ground Reaction View.
• If support has been added, then the support reaction curve is also displayed.
• A tunnel profile icon and tunnel face marker can be displayed.
• A long term ground reaction curve can be displayed if this option has been selected in Project Settings.

The Ground Reaction View can be displayed at any time by selecting the toolbar button, or selecting Ground Reaction from the Analysis menu. The Ground Reaction View is the default view whenever a file is opened, or a new file is created.

Ground Reaction Curve

In an unsupported tunnel, some distance ahead of the tunnel face, the internal pressure on tunnel walls is equal to the in-situ stress. It decreases to zero with distance from the face, opposite to the direction of tunnel advance, as illustrated in Figure 1. The ground reaction curve (GRC) is the relationship between this internal pressure and the deformation of the walls (or tunnel convergence).

Figure 1. Assumed support pressure pi at different positions relative to the advancing tunnel face. Not to scale. Hoek (1999).

Support Reaction Curve

Support reaction curve (SRC) is the relationship between support pressure and strain of the support. The slope of the curve (elastic zone) depends on the maximum support pressure and maximum strain.

Final Convergence and Factor of Safety

The point where both curves intersect determines the mobilized support pressure, and final tunnel convergence. It also determines the factor of safety for the support.

Figure 2. Ground reaction curve and support reaction curve. Final tunnel convergence and factor of safety is listed at the bottom of the plot.

Tunnel Profile Icon

The Tunnel Profile Icon is displayed in the upper right corner of the Ground Reaction View. It can be used to help visualize the distance of support installation from the tunnel face. It can also be used to interactively adjust the location of the support installation. See the Tunnel Profile Icon topic for more information.

Tunnel Face Marker

The Tunnel Face Marker is a vertical dotted line which can be displayed on the Ground Reaction View, which marks the position of the tunnel face relative to the Tunnel Convergence (or Wall Displacement) axis of the plot.

• The Tunnel Face Marker can only be displayed if the method of Support Installation = Distance From Tunnel Face (in the Support Parameters dialog). If the Support Installation is specified directly by Tunnel Convergence or Wall Displacement, then the Tunnel Face Marker option will not be available.
• The display of the Tunnel Face Marker can be turned on or off, by selecting the Show Tunnel Face Marker option from the right-click menu for the Ground Reaction View, or from the Ground Reaction sub-menu of the View menu.

Long Term Ground Reaction Curve

A long term ground reaction curve can also be plotted on the Ground Reaction View. The long term curve is derived by assuming a reduction of rock properties with time. The long term curve option, and the reduction factor is specified in the Project Settings dialog.