Why is ground stabilisation needed?

Ground stabilisation is a colloquial term used to describe ground strengthening or ground improvement.

This is required when the stability of a building becomes affected by changes in the ground that supports its foundations. There are several reasons behind these changes.

The soil can be of a type prone to expansion and contraction, depending on moisture content. This is the case with clay soil. Flowing water from broken drains can wash soil away, this applies to all soil types. Finally, the initial compaction of the soil under the foundations may have been inadequate, or vibrations from passing traffic could gradually weaken the ability of the soil to bear the weight of the foundations. Whatever the cause, unstable ground can mean the structure it supports starts gradually sinking into the ground, an effect commonly referred to as ‘subsidence’.

A building experiencing subsidence with damage to its structure will suffer from internal and external cracks appearing in the walls. Windows and doors become stuck or hard to open, floors may start sinking or become uneven and drainage systems may be affected. If left unchecked, subsidence can severely affect a building and, at the extreme level, can leave it uninhabitable if it a residential dwelling or non-operational if it is a commercial type building.

In a commercial environment, operational downtime can lead to a loss of revenue and have a detrimental impact on the health and safety of employees and customers. The impact can be even greater in the industrial sector or infrastructure projects.

The sooner the signs of subsidence are spotted and subsidence repairs are undertaken, the better. Early intervention using ground improvement techniques can stop further damage to the building and minimise the scale of any losses to the business.

Ground improvement works by using techniques that can strengthen the soil beneath the building to improve its load-bearing capacity. Traditional methods of ground improvement, or underpinning, involve adding materials such as concrete or steel into the ground to stabilise the foundations of the building. Other more modern techniques directly inject supporting materials into the ground.

Mass concrete underpinning requires digging holes under the foundations at carefully chosen intervals. Each section under the foundations is filled with concrete, and only when the concrete is set will the next section be tackled. This ensures that the building above is always adequately supported; however, it makes mass concrete underpinning a slow method of ground improvement and is also only suitable for relatively shallow foundations.

Piling is more appropriate than the mass concrete method when ground strengthening is required for buildings with deeper foundations. Piling requires skilled operatives, using heavy machinery to drive steel pipes deep into the ground to levels where the ground is more stable than the area under the foundations. Using steel or concrete to link the piles together, strong support can be created for the foundations to prevent further subsidence. The piling process is more disruptive and expensive than the mass concrete process.

There are modern techniques of ground improvement that are not as disruptive as either the mass concrete or piling methods. Instead of using steel or concrete and requiring excavations by hand or machinery, they involve the controlled injection of special resins or grouts that strengthen the ground under the foundations. The additives are accurately injected at strategic points and in carefully controlled quantities to ensure that the previously compromised ground will bear the weight of the foundations to arrest the subsidence. The continued controlled resin injection process can also raise the building to the required level. This is all done with minimal disruption and means that, in most cases, commercial premises and business operations can operate as usual during the ground strengthening process.

Mainmark offer two modern ground improvement techniques suitable for commercial, industrial, and infrastructure projects but also residential projects.

Teretek® is a non-invasive and quicker method of ground strengthening through the direct injection of an expanding polyurethane resin mix into the ground. This geopolymer resin injection will fill voids and compact and strengthen the soil to form a stable, long-lasting, environmentally inert material.

The JOG Computer Controlled grouting system is Mainmark’s unique ground improvement system, using a high-mobility cementitious grout inserted through multiple injection points into the ground. Computers allow up to 128 injection ports to be controlled at once, making it possible for the process to strengthen the ground under large and heavy structures.

Both Mainmark ground improvement techniques offer fast, cost effective and non-invasive ways to prevent further subsidence and raise and gradually return buildings to the required level.

If you would like to learn more about modern ground improvement techniques or have concerns that your building may be starting to show the early signs of subsidence and would like to discuss your options, please contact our experienced team will help you get back onto a firm footing.