Foundations for a new housing development in Walsall comprising 412 housing plots. The site was a former residential estate which had been demolished to make way for the new homes.
Roger Bullivant Limited (RB) developed a programme utilising two foundation techniques – ground improvement vibro stone columns and displacement piling; a top feed vibro stone column rig, and the quiet hammer rig system were used.
A total of 5122 stone columns were installed equating to 412 housing plots to depths ranging from 1.2m – 2.1m. The scheme was designed to provide a total bearing capacity of 125kN/m2 below the foundations. Stone columns were installed to refusal, each with a diameter of approximately 480mm.
Vibro stone columns help densify and stabilise the majority of the site while the pre-cast displacement piling technique created supports within the ashy black clays and gravely fill regions of the site. The pre-cast displacement piles amounted to a total of 466. These were installed to a depth of 10m and achieved a designed maximum safe working load of 350kN. Two pile sizes were used 200mm2 and 250mm2.