Work is now well in hand on the first phase of the Forth Road Bridge scheme. This contract consists of the construction of the foundations for the main piers of the bridge, the driving of wedge-shaped anchorage tunnels of some 200ft in length and the erection of reinforced concrete towers 150ft high.
The bridge will be the largest suspension bridge in Europe and the fourth largest of its kind in the world. It will have a main span of 3,300ft and two side spans of 1,340ft.
When completed, each pier will carry a 500ft steel tower – the main towers of the structure – constructed of prefabricated welded sections which will be assembled in position with large-diameter high-tensile steel bolts.
The value of compressed air is well demonstrated on this contract, says the Consolidated Pneumatic Tool Company, whose plant is at work on the site. At the south pier, compressed air caisson work is required, to a depth of at least 100ft into the river bed, before a solid rock foundation is obtained.