The Shaft

The sinking of the Shaft

You might imagine that the obvious way to build a shaft leading down into a tunnel would be to dig a massive hole and then line its walls with brick. However, the problem is shoring the sides of the shaft. So, Marc Brunel had the brickwork of the shaft first built as a tower, which was then sunk into the ground under its own weight as the earth was removed below it!.

A small building was set on top of the tower on which a steam-engine was assembled to pump away the water (which the tower encountered as it sank into the marshy Rotherhithe ground) and to bring up buckets of spoil from the bottom. The tower was 42 foot high and 50 feet across, and built on top of a 25 ton iron hoop. Its wall consisted of an inner and an outer surface of bricks three feet apart and the cavity between them was filled with cement and rubble.

The Shaft above ground