Publication Abstract

Proceedings - Fourth International Conference - Piling and Deep Foundations, 1991, Stresa, Italy, (DFI)

22 Farmers Avenue Road Crossing, Castle Mall Development, Norwich
D. Twine; Ove Arup & Partners, London, UK R.H. Wright: Fairclough Piling & Marine, UK

The Castle Mall Development involves the construction of a shopping center, mostly underground, on a 2.5 hectare site in the center of Norwich, England. The roof of the structure will support parkland and two main roads. These road crossings lay on the critical path of the project program which dictated that they be constructed using the top-down method. This paper presents the design and construction of the 1.8m diameter, 32 to 50m long pile foundations supporting 17m steel columns and column loads of up to 8600kN for one of the crossings. Several innovative approaches to building on Upper Chalk containing 20m deep loosely filled or voided solution features are described. Firstly, an effective stress method of pile design in chalk was developed. This resulted in piles, which were approximately half the length obtained from design methods current in 1989. It also enabled any reduction in pile capacity due to the 18m excavation to be evaluated. Secondly, the decision to construct the piles using the oscillated casing system provided the means to overcome the problems associated with solution features. Where solution features were encountered below basement level, the casing was advanced up to 28m below ground level to just below the base of the solution feature and left permanently in place. Full details are presented of the ground conditions, pile design and construction of the adopted piling method.

 article #463; publication #37 (IC-1991-IT)