A VAST new ornamental glasshouse is being built for the Royal Horticultural Society on a lakeside site at Wisley, near Guildford in Surrey.
The site for the 5,000m 2 structure is underlain by waterlogged, loose to very loose sands and soft clays overlying terrace gravels. The project includes formation of a new lake.
Main contractor Kingcombe Aquacare appointed Keller Ground Engineering to vibro compact the up to 4m thick layers of loose sand and soft clays. This provided a safe bearing pressure of 150kN/m 2 beneath the foundations.
Keller used its new semi-automated vibro stone column rig to carry out the work. The company says it is able to set compaction levels in advance. Using the bottom feed process, the machine delivers stone in layers which are compacted in predetermined, short lifts.
Keller engineer Derek Taylor says this form of staged compaction is essential to ensure weaker critical layers are compacted along with the generally loose soil.
The whole process is recorded on an in-cab computer and hard copies of the column construction details are printed out immediately.
'Stone column quality is not just improved with the new rig, we can also install them faster, ' Taylor says.