Caissons and shafts

This chapter deals with the construction of shafts and caissons using pre-cast segmental linings together with the use of sprayed concrete lining in shaft sinking operations.

Caissons in the marine environment are not covered in this chapter. Construction methods used, including generally available types of shaft linings, other materials and construction plant commonly used are all discussed, and a brief description is given of specialist processes that can be used to provide ground stability when required. Comments on design considerations for the construction of shafts and caissons using pre-cast segments are also included.

Shaft sinking in the UK is generally carried out using circular pre-cast segmental linings, which were originally developed after the Second World War as an alternative to the original and more expensive cast-iron linings. They are typically used to provide access for tunnelling operations, where they can then be converted to permanent access chambers. More recently, they have become increasingly used to form storage chambers, pumping stations and so on, where they can offer a cost-effective solution to more expensive alternatives such as in situ construction within a piled cofferdam. The advantages are that the permanent works materials are, in effect, used as the temporary works during construction and also that the construction ‘footprint’ is kept to a minimum (an important consideration in urban areas).