Housing Development

Flanshaw Lane, Wakefield

This site was initially presented to us by the consulting engineers, enquiring whether we could treat any of the proposed house plots with vibro stone columns as opposed to driven piling. The majority of the site had competent ground at shallow depths and so traditional strip footings could be used.

The challenge of this site was the infilled quarry that lay beneath around 50 proposed plots. The plots sitting wholly in the quarry area were treated with partial depth treatment to maximum depths of 8m with the foundations above fortified into semi-rafts. This ensured the plot foundations acted as a single unit with uniform resulting settlements beneath the foundations.

Some of the proposed plots were sited over the existing highwall of the quarry, presenting an issue to us with regards to predicted unacceptable high differential settlements. We worked very closely with the house builder, consulting engineers, groundworkers and the site investigation company to present a feasible solution for the plots in question. Beneath these plots, the existing bedrock was dug out to specified depths allowing us to model settlements on either side of the plots to ensure they were within 5mm of each other. Due to this site being unusual, all proposals were submitted to the NHBC upfront to ensure approvals were obtained in advance of our works being carried out on site.

The remediation took place on site, with constant live feedback from the parties involved confirming differences to our understanding of the quarry location. With this in mind, our settlement design calculations and proposed column layout drawings were frequently updated and revised to reflect the reality of the ground conditions present. Over 1300 stone columns were installed over nearly four weeks on site, including utilising a pre-auger rig in areas to ensure the columns were installed to their required depths.