This architectural drawing is Section of tunnel with detailing and dimensions. A hillside tunnel entrance is called a portal; tunnels may also be started from the bottom of a vertical shaft or from the end of a horizontal tunnel driven principally for construction access and called an edit. Due to the arching effect, which is a fundamental phenomenon in tunnel construction, the vertical and lateral pressure on a tunnel lining will be reduced from the over-burden weight in soil. Long, prefabricated tube sections, made of steel or concrete and sealed to keep out water, are floated to the site and sunk in the prepared trench. Then divers connect the sections and remove the seals. Any excess water is pumped out, and the entire tunnel is covered with backfill. For more details and information download the drawing file.
