Mine Development and Surveying
This domain covers how an orebody is reached and controlled geometrically: access method selection, shaft sinking and drifting, the drilling-and-blasting cycle that drives development headings, and the surveying that fixes alignment, grade and volume. Questions mix definition recall (which explosive in wet ground) with calculation (powder factor, curve data, traverse closure).
Access and development
- Access options are shaft, incline or drift, adit, and decline; selection depends on depth, dip, surface topography, production rate and capital available.
- Shaft sinking is a drill-and-blast cycle with kibble hoisting and a scaffold stage; water-bearing strata force special methods such as cementation, ground freezing or caisson sinking.
- In drifting, the cut holes (burn cut or V-cut) create the free face, relievers enlarge it, easers and trimmers shape the profile; pull per round governs advance.
Drilling and blasting
- Powder factor (kg/m^3 or kg/t) fixes total charge; burden and spacing scale with hole diameter and explosive strength; stemming confines gas.
- ANFO is cheap but not water-resistant; emulsions and slurries suit wet holes. Initiation runs from safety fuse through electric detonators to NONEL shock tube and electronic delay systems.
- Controlled blasting variants: pre-splitting, smooth blasting and cushion blasting, distinguished by charge concentration and whether the fracture plane is created before or after the main blast.
Worked example
A circular curve has radius R = 300 m and deflection angle 40 degrees. Tangent length T = R tan(deflection/2) = 300 x tan 20 = 300 x 0.36397 = 109.19 m. Curve length L = pi x R x deflection/180 = 3.1416 x 300 x 40/180 = 209.44 m. Chainage of the tangent point equals chainage of intersection minus T; pegs are then set out by deflection angle per chord, delta (minutes) = 1718.9 x chord/R.
Traps
- Using the full deflection angle instead of half of it in the tangent formula.
- Confusing an adit (horizontal, daylights on a hillside) with a drift or decline.
- Quoting powder factor per hole rather than per cubic metre or tonne of rock broken.