Soil quality can be a problem in construction – but there’s an innovative technique being used to improve weaker soils, and it happens to be more environmentally friendly than standard piling methods.
Developed by Joseph Keller, founder of global geotechnical firm Keller, the technique involves using columns of crushed concrete from other construction projects.
It’s currently being used in a housing development project in Hoofddorp, a small town near Amsterdam, where the soil has a layer of clay at around 13m, preventing ground water ingress.
Project Manager for this 31-unit apartment block, Richard Looij, explained, “The challenge was to improve the soil without letting the water in.
“We initially explored soil compaction, but only around 30-40% of the site was suitable, so we proposed vibro stone columns. This was the best technical and economical solution, but it was also the most sustainable.”
The technique involves using a vibropiling rig, with a vibrating poker fitted, which penetrates the ground to refusal or design depth. The poker is then removed, and crushed concrete is tipped in from the surface. The vibrating poker is then used to compact the recycled concrete.
This method improves the load bearing capacity of the ground and can also provide a drainage path.
It’s the first time the technique has been used for a multi-storey residential block in the Netherlands and using it more widely would help reduce environmental impact in some construction projects.
In this case, the process doesn’t use new materials, and if the building is demolished in the future, the crushed concrete can be dug up and reused. Another environmentally-friendly and economic advantage is that the method doesn’t create spoil to be disposed of in landfill.
On top of these advantages, vibro systems typically generate only 10-25% of the CO2 when compared with a piling system. And using locally-sourced crushed concrete can give a 30% reduction in CO2 compared with newly quarried stone.
This system is also substantially cheaper than piling. Sometimes an environmentally-friendly solution can be more expensive to implement than the traditional method, so it’s good to see a solution that is sustainable both environmentally and economically.
It’s something that can be used on infrastructure and residential projects, and I expect we’ll see this technique used more as a project’s environmental credentials become increasingly important.
In the meantime, if you need an innovative solution to a structural challenge on an upcoming project, please do get in touch.