Soil Stabilisation meets the challenge of saturated soils

One of the wettest Januarys on record has meant that the construction industry is having to deal with some of the most challenging ground conditions for years. Contractors are increasingly turning to soil stabilisation to help dry out saturated soils to enable project work to continue reports Britpave, the infrastructure industry association.

The Met Office has confirmed that last month was one of the wettest on record due to a series of Atlantic low-pressure systems. Northern Ireland and England were particularly wet with 70 per cent and 50 per cent more rain respectively. With few days of drier conditions, the ground has become saturated resulting in construction projects having to stop operations.

The use of soil stabilisation offers a solution. Soil stabilisation is a well-established civil engineering technique that treats and strengthens poor or unsuitable soils using cementitious binding materials. It is particularly useful in helping to dry saturated soils.

When quick lime is added to a wet soil, the soil rapidly becomes drier and slaked lime is produced. This is a highly exothermic reaction, which, together with the chemical combining of water with quick lime, significantly reduces the moisture content of the soil. In addition, a further change happens where the clay undergoes a ‘cation exchange’ whereby the soil becomes less clay-like and more sand like. This further adds to the drying process.

“Soil stabilisation binders are used to improve unsuitable soils that are soft and wet with low shear strength and low bearing capacity. Once treated with the binders these soils will be fit for use as general/structural fill or even as sub-base material for pavement and foundation construction,” explained Stefan Stansfield, Chair of the Britpave Soil Stabilisation Task Group. He added: “Furthermore, the treatment is carried out in-situ. The treated soils may be retained and used on site as opposed to being taken away via multiple lorry trips and dumped at tips.” However, Stansfield warned of the importance of following good industry practice: “Soil stabilisation is more than simply rotovating binders into soil. It requires the proper ground investigation, soil sampling and laboratory trials to determine the right binder mix, good site quality control, use of appropriate plan and good on-site working practices. Done correctly, soil stabilisation offers an engineered solutions for a wide range of construction projects.”

With Met Office long range forecast for February predicting a series of frontal systems from the North Atlantic bringing yet more rain, the ability of soil stabilisation to dry out and increase the strength of soggy ground is likely to be increasingly valued.