Excavators (And Specific Survey Control)
Excavators - Survey Duties
Some of the common surveying control for excavators include:
- Dig Crest Pegs
As shown in example #1 below, the crest pegs (which surveyors will place for all different types of machinery) show the machine where to dig to, to achieve a design batter angle and finish the dig at the appropriate design point. If you look at the shovel page, the example provided there shows a small section below the shovel and above the coal. Generally (depending on variables such as steepness of coal seam), the shovel will not uncover the coal and the last bit of material will be left for an excavator to remove. This ensures minimal loss of coal while uncovering it, and it also allows for the coal to be effectively uncovered before being mined. The roof of the coal also needs to be surveyed before it can be mined (see coal reconciliation section and the photo above).
- Dig Toe Pegs
Toe pegs are often used when multiple passes are required (i.e. multiple passes may be required when the overburden between the top level and the coal level is too high for the machinery). They have a few different uses, but perhaps the most useful is for while the machine progresses, the operator can compare where they have already excavated and see where the toe of the dig should have been (and line it in correctly as excavations progress further).
- RL (Reduced Level) Pegs
To achieve a level running surface or to move up and down as according to a design, the operator needs to know how much cut or fill is required it's position. If cut and fill pegs are not used, often RL (reduced level) pegs are a suitable way of letting operators know how high they are, and how they are going compared to design.
- Coal Edge Pegs
When excavating materials covering areas that have already been mined (i.e. as the mine progresses), it could be a waste of resources to remove material (e.g. resulting from a blast) without any coal below it. Coal edge pegs can shown the operator where the edge of the coal should be located below the material so they don't excavate more waste than required. See the dragline section for more information about the use of coal edge pegs.
- Drop-in Pegs
Drop-in pegs are used to tell an excavator operator where to start digging a declining ramp. In conjunction with cut and fill pegs, these pegs are an important start to the creation of a good ramp. It's important for surveyors to monitor and control ramp excavations because if they aren't correctly constructed (e.g. too steep), they could increase the costs of hauling material.
- Clear Line Pegs
Clear line refers to a line outside of a drill pattern design which if cleared, will allow access for overburden drills to drill the pattern. Usually the job of preparing a drill area (drill prep) is suitable for a dozer, but in some circumstances the assistance of excavators may be required.
Example #1: Excavator pegging example, multiple passes
(Click for larger version of image)