Slot Ramp Centre Line

To minimise costs, many shallow open pit mines are accessed from a slot ramp instead of a spiral ramp (which suits a deeper mine). A slot ramp descends into the pit through a steadily-deepening trench. It differs from a spiral ramp in the following ways:

  • Because it runs along the bottom of a large "trench", the ramp is always at the toe and has no crest lines. As it extends lower, the original surface appears higher and higher above it;
  • The track of the slot ramp is not controlled by the shape of the pit; instead it is able to take any practical shape, and is often curved to match existing surface haul roads;
  • The ramp appears to widen slightly as it approaches each berm crossing, so that at the berm crossing, its total width is ramp + left berm + right berm.

As the mine becomes deeper, the slot ramp is often converted to a traditional spiral ramp.

To create a new slot ramp:

  1. Verify the berm and batter parameters set for the walls of the pit in the Input Data.

    2. The berm, batter, and expansion settings of the pit will be used to:

    • control the descent of the ramp
    • adjust the width of the trench at each berm crossing
  1. Select a pit string and on On the Mining | Pit Design tab, in the Pit Road group: Click Slot Ramp Centre Line to create a new slot ramp.

    2. Alternatively, Right click on a pit string and select New Pit String > Slot Ramp Centre Line from the right-click menu.

    A list of recently-loaded form sets (if any) are available for selection on the drop-down menu. Select Other to load a less recent form set.

  1. In the Slot Ramp Properties form, define the Width and the Gradient of the ramp you want to build:

  1. After you dismiss the Slot Ramp Properties form, the cursor changes to a crosshair cursor. Use the mouse to digitise a centre line that intersects the pit string at the slot ramp entrance.

    2. It is important to ensure that the slot ramp centre line is long enough to build the slot ramp.

  1. On the Mining | Pit Design tab, in the Generate Pit Contours group: Click the Project String tool to use the batter height and slope to project the selected string. If a slot ramp centre-line has been digitised and is selected, then this tool can be used to generate a slot ramp.

    2. When projecting the pit string, the ramp is built to the next level and the projected string is built around the slot ramp taking into account slope restrictions.

  1. After building the bench with the slot ramp, you will need to make some corrections around the slot ramp entrance.