Tunnels, which are artificial underground passages, are constructed for which of the following purposes in civil engineering and infrastructure?

Introduction / Context:
Tunnels are engineered underground conduits that enable transportation and utility services to pass through obstacles such as mountains, urban congestion, or water bodies. Understanding the range of applications highlights why tunnelling is a core discipline within civil engineering and urban infrastructure planning.

Given Data / Assumptions:

• Tunnels serve multiple transport modes and utility networks.
• They offer protected, grade-separated routes and corridors.
• Selection depends on topography, environment, and urban constraints.

Concept / Approach:
By placing infrastructure below ground, tunnels reduce surface disruption, shorten routes, and enhance resilience. For highways and railways, tunnels provide direct alignments with minimal grades. In utilities, tunnels convey sewage (gravity or pressure) and raw/treated water, protecting networks from surface hazards and minimizing right-of-way conflicts. Multi-utility tunnels can co-locate services, simplifying maintenance and future expansions.

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