Shovels (Power Shovels) (And Specific Survey Control)
A Shovel, also known as Cable Shovel, Stripping Shovel, Front Shovel, or Electric Mining Shovel are a large machine used for excavating large amounts of material using a cables and a bucket. They are generally electric powered and are predominantly used in open-cut mining applications.
In certain instances, shovels can be used for loading coal if the seam is thick enough; however they are generally most economically efficient if the material being dug is higher than the machine. Hence, if a coal seam is not too thick, an excavator is more suitably used for loading it.
Modern shovels travel on tracks and have the ability to rotate the upper half of the machine in all directions from a stationary position. They generally obtain a higher stripping rate than excavators and are therefore used for large excavation operations.
For more information specifically about shovels, click here.
Some of the common surveying control for shovels 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. Machines such as shovels are often limited to their flexibility when it comes to creating a perfect batter, so we included this consideration in the example (note the cut shape in the example caused by the motion of movement of the shovel).
- 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 as excavations progress). In some circumstances, a shovel may not be able to achieve the design batter due to its limited bucket manoeuvrability, so an excavator may work in tandem with it to clean up batters in front of it on a higher level after it moves onto a subsequent pass. In this circumstance, toe pegs would show the excavator where the batter should end as compared to the crest pegs (multiple sets of dig crest pegs may be required for this activity also, one for a batter achievable by the shovel and another set further back for a batter achievable by the excavator by pulling down leftover material).
- RL (Reduced Level) Pegs
To achieve a level running surface or to move up and down as according to a design, the shovel driver 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.
Example #1: Shovel Survey Control Pegs Example
(Click for larger version of image)