Introduction / Context:
Efficient and safe drill-and-blast tunnelling follows a repeatable cycle at the face. The order of profiling, drilling, blasting, ventilation, safety checks, and mucking is critical to minimize delays and incidents. This question tests the correct sequencing around blasting events in rocky terrain.
Given Data / Assumptions:
- (1) Removing foul gases after a blast.
- (2) Marking the tunnel profile (setting out the cut and trimmers).
- (3) Setting up equipment and drilling the blast holes.
- (4) Checking misfires after blasting and ventilation.
- (5) Mucking—removing broken rock.
Concept / Approach:
The cycle begins with layout (marking profile) followed by drilling. After blasting, ventilation clears fumes; then a careful misfire check ensures no live explosives remain before mucking. Skipping or reordering these steps risks overbreak, rework, or accidents.
Step-by-Step Solution:
First, mark the face to the designed profile (Step 2).Second, set up and drill per the marked pattern (Step 3).After blast, remove gases with forced ventilation (Step 1).Then, perform misfire checks per safety protocols (Step 4).Finally, muck out the blasted rock (Step 5).
Verification / Alternative check:
Standard tunnelling cycles list “profile → drill → blast & ventilate → check → muck → support,” matching the selected order up to the mucking stage.
Why Other Options Are Wrong:
Any sequence that places mucking before misfire checks or ventilation is unsafe.Starting with gas removal or misfire checks before blasting is illogical.
Common Pitfalls:
Rushing to muck without adequate gas clearance or misfire inspection.
Final Answer:
2 3 1 4 5
Discussion & Comments