In steep-gradient tunnels, a wooden bulkhead (used to control muck movement) is provided with how many openings to manage passage and controlled discharge?

Introduction / Context:
On steep grades, muck tends to rush downhill after blasting, creating safety hazards and operational difficulties. A wooden bulkhead is installed to regulate flow, protect workers and equipment, and allow controlled loading into cars or conveyors. Its configuration typically includes openings that balance containment with operational throughput.

Given Data / Assumptions:

• Tunnel grade is steep enough to require a bulkhead for muck control.
• Openings are necessary for track/pass-through and controlled muck discharge.
• We seek the standard number of openings.

Concept / Approach:

A practical wooden bulkhead has two openings: one larger opening for passage of equipment/track or controlled chute loading, and a second for regulated discharge or ventilation/inspection. This dual-opening arrangement allows operations while maintaining a barrier that prevents uncontrolled run of muck.

Step-by-Step Solution:

Verification / Alternative check:

Construction manuals depict bulkheads with separate pass doors/chutes; a single aperture is usually insufficient, and no openings would make operations impractical, corroborating the two-opening convention.

Why Other Options Are Wrong:

• One opening: Limits control and access.
• Three or four openings: Atypical and may weaken the bulkhead.
• No opening: Operationally unfeasible.

Common Pitfalls:

• Over-sizing openings, reducing containment effectiveness.
• Neglecting reinforcement of openings against impact loads.

Final Answer:

Two openings are provided