In tunnel engineering, the term ‘‘drainage’’ encompasses multiple stages and strategies. What is the general name given to the methods used for removing water before, during, and after excavation?

Introduction / Context:
Managing groundwater and seepage is central to safe and economical tunnelling. Water affects face stability, support selection, liner durability, and construction logistics. Different phases of a project require different drainage approaches, from pre-excavation measures to long-term operational systems.

Given Data / Assumptions:

• Three terms are listed: foredrainage, dewatering, and permanent drainage.
• Question asks for the general name applied to these methods in the tunnelling context.
• We interpret the intent as recognizing that all listed terms fall under the broader practice of tunnel drainage.

Concept / Approach:

Foredrainage involves ahead-of-face measures (e.g., probe drilling, pre-grouting, relief wells) to reduce inflows before excavation. Dewatering refers to active removal of water during construction (e.g., well points, sump pumps). Permanent drainage includes installed systems (inverts, side drains, membranes) that handle water during the structure’s service life. All are components of tunnel drainage engineering.

Step-by-Step Solution:

Verification / Alternative check:

Method statements for wet ground commonly integrate all three: pre-grouting (foredrainage), sump pumping (dewatering), and final liner drainage (permanent), confirming the holistic categorization.

Why Other Options Are Wrong:

• Any single method alone is incomplete for the life-cycle of a tunnel.
• 'None of these' is false because these are standard drainage classifications.

Common Pitfalls:

• Relying solely on construction dewatering without planning permanent systems.
• Skipping foredrainage in high-pressure aquifers, risking face instability.

Final Answer:

All of the above.