Difficulty: Easy
Correct Answer: All the above.
Explanation:
Introduction / Context:Water management is a defining feature of tunnel durability. Even small inflows can degrade trackbeds, pavements, or utilities and promote lining damage. Designers therefore combine multiple permanent drainage tactics to intercept, convey, and reduce inflow throughout the life of the tunnel.
Given Data / Assumptions:
Concept / Approach:Longitudinal drains collect seepage along the sidewalls or invert and take it to sumps. Continuous open drains provide redundancy and access. Concrete or segmental linings reduce seepage and protect the structure. Grouting seals discontinuities in the surrounding ground. Used together, these measures minimize pore-pressure buildup and protect the tunnel envelope and track/roadbed.
Step-by-Step Solution:
Provide longitudinal/invert drains with adequate gradient to sump/pump rooms.Detail open channels or perforated pipes with clean-out points.Use linings with waterstops; add drainage layers/geotextiles as needed.Apply pre- or post-excavation grouting to cut off significant inflows.Verification / Alternative check:
Reduced inflows at inspection points and dry operating conditions validate the combined drainage scheme.Why Other Options Are Wrong:
Each single option is effective, but best practice employs them in combination; hence “All the above.”Common Pitfalls:
Relying solely on lining without drainage; hydrostatic pressure can still damage the structure.Final Answer:
All the above.
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