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Machine Control (Open-cut Mine Surveying Duties)

Day to day activities of a mine surveyor include machine control. Machine control refers to setting out designs and providing advice to operators to ensure the excavation process is completed appropriately to the engineering design. Depending on the equipment available, external variables and technical issues, set out in a surface operation generally refers to placing pegs with colour-coded flagging tape with the use of RTK GPS or total stations.

So what operating machines do we control? Almost everything.

In order for machines such as excavators or shovels to dig coal, surveyors need to put pegs in for them to dig from. This process isn't quite as simple as placing a peg on a line derived from coordinates produced on a plan as the pegs need to be placed in at a battered angle. Basically, we need to place pegs at a projected position so that if a machine digs from them at the design batter angle, they will end up where we want them to be. As different machines are able to achieve different batter angles then calculations have to be completed according to the design batter angle.

Example #1: Dig to Coal at 45°

In the example above, the 'design point' gives the location that we would want the machine to land on coal. However machines don't dig at vertical angles and it is not safe to do this. Therefore a batter angle is provided, in this case 45°, and the survey peg has to be projected at this angle. The idea is that the machine will dig at 45° from where the peg is placed and end up on the coal at the position we want it to be. It should be noted that the dig between the peg and the design point may require multiple passes, and therefore pegs placed at each stage (see next example).


Example #2: Dig to Coal at 63°, Multiple Passes


The above diagram gives a more realistic representation on the dig process to get to the design point. Generally multiple passes will be required and usually pegs at each stage will assist operators in maintaining the correct batter angle. Skilled operators are able to maintain the correct batter from the first peg without requiring pegs at each pass. If batters are not kept consistent, then the pegs won't line up perfectly as depicted by the diagram above and will either be out in the flat area if the batter is too steep, or will be too difficult to re-peg if the batter is not steep enough (because the pegs will be on the batter).
The amount of offset put on a peg from the design line is based on a simple calculation involving the design batter angle and the difference in height you are above the design point (for example, if the current elevation is 10m above the design point and a 63° projection is required, then the offset from the design line will be 0.51*Δ Height = 5.1m). Some GPS rovers have the added ability of automatically calculating this offset on the fly according to the angle inputted so that it doesn't have to be done manually at each peg.


Example #3: Shovel dig crest pegs


(Click picture for larger version)


Machine control isn't limited to pegging batters, surveyors also peg drill prep limits for dozer operators to prepare drill areas accessible by drills, as well as ramps, maintenance pads, roads, and grade control for various operations. RL (reduced level) pegs are also provided regularly to assist machine operators in ensuring they are digging to the correct or optimum level as depicted by a design. Pegging design batters is a normal surveying operation, regardless of the mineral being mined or the machine doing the digging. It is a standard duty across any mine or surveying operation requiring excavations to design levels. Surveyors are also required to peg drill patterns so that drill operators know where to drill, however at some mines drills are fitted with GPS and do not require pegs for guidance.

Mining Machinery - Specific Survey Control

Some of the control (pegging operations) required by surveyors with regards to specific machinery can be located in the following pages:
Draglines
Excavators
Shovels
Front End Loaders
Track & Wheel Dozers
Dump Trucks

Open-cut Mine Surveying Duties