JOG Grouting (Lifting) – Barnet Phase 2

Following the success of the piled raft underpinning scheme concluded in 2015 PAH were appointed by the same insurers and engineers to remediate the block of maisonettes next door. This time however we were approached to lift the entire building by as much as 140mm using an innovative computer controlled grout jacking method alongside specialist sub-contractor Mainmark Engineering.

The JOG Computer Controlled Grouting uses an advanced grout monitoring system with progress reports, allowing for fine-tuning. This helps achieve a high degree of accuracy and minimizes stress on separate sections of the building during the process. The sections that were worked upon were supported and precisely lifted using small, sequenced injections of high-mobility cementitious grout that is very fluid but fast curing.
In total, 70 cementitious grout injections were used beneath the block and beam foundations with a split of 40/30 between external and internal placement. The injection depth was 1.1m and 2.1m, respectively, with a distance of 1.5m between injections.
All six of the primary level control stations on the building were monitored, and upon completion, only 9 of the 240 survey points were outside the NHBS standard tolerance level. A lift of 139mm was achieved at the maximum point.
The project engineer summarized the re-levelling success: ‘the lift positively exceeded the set limits, and the stress on the structure was well below the tolerable levels.’

The lifting part of the project was completed in a remarkably short time and results achieved 17 days from arrival to exiting of the site. Not only that but the upstairs residents were able to continue living in the building whilst works were carried out saving significant sums of money and minimizing inconvenience to residents