AG Berry, Arup, UK. This paper was first published in GE’s November 2009 issue.
Base cleaning is common for bearing piles, allowing the end-bearing capacity of the bored pile to be included in the design. However, the base cleaning of diaphragm wall panels is not common in the UK. This paper describes the author’s experience of a diaphragm panel wall base cleaning process that was developed for a load-bearing retaining wall for a large basement in east London. The extra vertical capacity achieved by the clean base allowed end-bearing to be taken into account in addition to skin friction, providing substantial savings in the number of foundation piles required.
The base-cleaning process developed consists of two stages. The first comprises scraping away ridges in the panel base left behind by the clamshell excavation bucket. Successful removal of the ridges is verified by means of a weight attached to a measuring tape wide enough to sit on top of any ridges.