tonnels

Tonnels is the French plural form of tonnel, a term used in French for tunnel. In English, the corresponding word is tunnel. Tunnels are passages that run underground or underwater and are constructed to enable transportation, drainage, utilities, or mining, often spanning long distances where surface routes are impractical.

Common types include road tunnels (for vehicles), rail tunnels (for trains), water and utility tunnels (carrying water mains, sewer lines, or cables), and mining or adit tunnels. Pedestrian and cycle tunnels also exist, often in urban environments or around transit hubs.

Construction methods include cut-and-cover for shallow tunnels, bored tunnels using tunnel boring machines for longer routes, and immersed tunnels where segments are sunk and joined underwater. Construction requires dealing with groundwater, rock and soil conditions, and ensuring ventilation, lighting, monitoring, and safety systems; fire protection and emergency egress are critical components.

Notable examples include the Channel Tunnel, which connects Great Britain and France, and the Gotthard Base Tunnel in Switzerland, one of the world’s longest and deepest rail tunnels. Older and urban examples include the Severn Tunnel in the United Kingdom and numerous metro tunnels in cities such as Paris and London.