Question 13 of 27

Question 3.2 key cut and deadheading (3 marks)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

3.2.1 Key cut. The key cut is the FIRST, narrow trench cut down through the overburden along the advancing edge of the current cut, dug before the main width of the bench is stripped — it establishes the working floor level and provides the dragline its first void to begin casting material into, and it defines the boundary/alignment the rest of the cut will follow. Carried out by the dragline itself digging a single-bucket-width trench the full depth of overburden along the strike; its importance is that an incorrectly-aligned or incorrectly-graded key cut propagates a geometry error through the entire subsequent cut, since every later pass casts relative to it.

3.2.2 Deadheading. Deadheading is moving the dragline (walking) from one position to the next WITHOUT digging — a non-productive repositioning move, e.g. walking back to the start of a new cut, or walking around an obstacle. It is carried out using the machine’s own walking mechanism (a slow, shuffling tub-lift-and-shift cycle for a walking dragline, typically well under 1 km/h). Its importance is purely economic: deadheading time is 100% non-productive (no material moved) so mine planning tries to minimise the frequency and distance of deadheading moves by sequencing cuts to keep the machine progressing steadily along one bench rather than jumping between disconnected areas.