User Manual > Truck & Shovel Simulation > Setting up Haul Roads and Accesses > Geometric Design of Haul Roads and Accesses > Creating a Road on Terrain > Using Approximate and Virtual Vertical Alignments

Virtual Vertical Alignments are Vertical Alignments which are completely independent of the topography over significant portions of the length of the road. Typically roads with a Virtual Vertical Alignment will merge with the topography at the end points of the alignment can be very different in the intermediate section. There are many applications for Virtual Vertical Alignments, several common applications include:

•Conceptual designs. When setting for a conceptual design of proposed pit there is considerable work in creating pit shells which incorporate ramps in the excavations and dumps. If several different ramping options are to be considered this compounds the work. Using Virtual Vertical Alignments "blank" pit shells can be established with no ramps and a variety of ramp options can readily be modelled using Virtual Vertical Alignments. Clearly this approach is approximate as it is not account for the volumetric affect of proposed ramps, however it does allow the productivity applications to be rapidly assessed.

•Rapid assessment of cross-pit haulage options in an existing operation. To fully implement a cross pit haulage option is necessary to either construct an in pit Bridge from waste or excavate a ramp in the end wall. Using Virtual Vertical Alignments the horizontal alignment can be drawn wherever the cross pit access is proposed and the vertical alignment placed at the proposed level of the cross pit access. When simulation is performed the trucks speed will be calculated based on the vertical alignment which is consistent with the proposed access.

•Cost benefit analysis of haul road upgrade. If a permanent or semi permanent haul roads has a large dip or rise requiring steep gradients, it may be possible to reduce haul times via a cut and fill operation. Using a Virtual Vertical Alignment the haul time implications of various regrade options can be rapidly assessed. Using the Excavate Road facility to cut and fill volumes can also be rapidly assessed. If the regrade appears feasible it is also possible to simulate and optimise the cut and fill. Cut portion of the regrade is modelled as Staged Excavation and the fill portion modelled as a Stage Dump.

Design of Roads with Virtual Vertical Alignments

The design requirements for Virtual Vertical Alignments varies depending on the Mode of Operation; Main Haul Rods, Excavation Access and Dump Access.

The following topics described the process of creating roads with Virtual Vertical Alignments for the various Modes of Operation.