- 2079 Jestha · 2 marks
Short note: Underground excavation process
Short answer
The process includes portal preparation, excavation by drill-and-blast or TBM, mucking, immediate rock support (bolts, shotcrete, steel ribs), geological mapping and convergence monitoring, and final lining. Major geological problems are squeezing, rock burst, water inflow and overbreak.
Write a short note on the underground excavation process.
Underground excavation is the construction of tunnels, caverns and shafts below ground.
Process:
- Investigation and design of the alignment, shape and support, based on rock mass classification.
- Portal construction: slope cutting, support and drainage at the entrance.
- Excavation:
- Drill and blast: drilling holes, charging them with explosives, blasting and ventilating.
- Mechanised: roadheaders in soft to medium rock; tunnel boring machines (TBM) in a wide range of rock, including hard rock.
- Full-face or top-heading-and-bench method, chosen according to rock quality.
- Mucking: removing the broken rock.
- Support: rock bolts, shotcrete, wire mesh and steel ribs; installed immediately in poor rock.
- Geological mapping and monitoring of convergence.
- Drainage and ventilation, then the final concrete lining.
Geological problems: squeezing, rock burst, water inflow, overbreak and faults.
✓ Answer checked by Claude Opus 5.5 (high effort)
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