~ Exploring the risks of ground instability and providing effective solutions for airports ~
In 2019, TUI faced weekly losses of over $3.4mil due to grounded planes. For airports, unplanned downtime poses huge financial risks and invites public fury. Ground instability under terminals, aprons, taxiways, and runways creates costly delays and safety hazards. Here Richard Holmes, director of infrastructure at geotechnical contractor Geobear, explores the risks posed by subsidence, its impact on airport operations, and how understanding and managing underlying ground conditions can help mitigate these issues.
Airports face persistent challenges with ground stability. Issues like subsidence, water ingress, and heavy traffic can lead to movements of up to 75mm in Pavement Quality Concrete (PQC) slabs in high-use areas like taxiways, aprons, and slot drains. This can cause cracking and misalignment, creating safety and operational risks that demand urgent repairs.
Subsidence, caused by voids or weakened ground beneath PQC slabs, destabilises these critical areas. Water ingress worsens the situation by softening the ground beneath, further accelerating instability and the risk of slab failure.
Heavy traffic from aircraft and service vehicles compounds the issue by creating a “pumping” effect, forcing water and soil particles up onto the pavement surface through unsealed or failing pavement joints. This creates a three-fold issue: destabilising the ground resulting in rocking slabs, increasing the likelihood of step misalignments, and contaminates the pavement surface with soil slurry.
Prompt, effective ground improvement is crucial but conventional techniques, like full slab replacement, are slow, invasive, and less sustainable. For example, apron repairs for a 40 square meter area can take up to three shifts to complete, followed by a 24 hour curing period to achieve the required load-bearing strength. This limits airports’ operational capacity and puts critical infrastructure out of action.
Another problem encountered at airports is stabilisation of terminal floors, car parks and other structures. Traditional methods to stabilise these involve minipiling utilising air or water flush and cementitious grout. While these methods address the problem they require drill rig access, temporary working platforms, curing times for the grout and complex scheduling.
Restricting this work to overnight windows minimises interference in regular operations but extends project durations, delaying maintenance and other crucial tasks. Additionally, the reliance on traditional methods can pose logistical challenges.
Both approaches are not only time-consuming, but costly, as they reduce usable space and impact revenue streams from high-footfall areas such as retail and parking.
Geobear’s geopolymer solution offers a faster, less invasive alternative. Technicians drill small holes and inject the material beneath PQC slabs and terminal floors. The material fills voids, binds soils to stabilise ground, and works to lift and realign pavements quickly and with no curing time.
The geopolymer’s rapid cure time allows treated areas like runways, taxiways, slot drains, and terminal floors to return to full service immediately following completion. There is minimal disruption, reducing revenue loss by keeping critical space operational. The non-invasive injection unit is compact and easily mobilised, eliminating the need for access, temporary works and heavy machinery thus simplifying logistics.
How geopolymers stabilised Leeds Bradford Airport
A successful application of this solution took place at Leeds Bradford Airport, where voiding beneath PQC slabs caused pavement instability. Geobear’s team developed a bespoke engineering plan for the site, treating 13 slabs on the airfield over four nightshifts, with a curing time of 20 minutes per slab.
This quick turnaround allowed the runway to return to service in time for the next operating day, unlike traditional concrete repairs which would have required a week to reach load-bearing capacity.
The benefits extend well beyond immediate repairs. Geobear’s solution offers a 60-year design life, projected to save Leeds Bradford Airport over £1mil in maintenance costs over ten years for a typical 50-slab area.
Additionally, in line with the aviation industry’s focus on sustainability, geopolymer injection can reduce carbon emissions by 62 per cent compared to traditional approaches like full slab replacement, as verified by Carbon Footprint Ltd.
In an industry where unplanned downtime can cost millions, addressing ground instability is essential. By offering a fast, less disruptive solution to subsidence and water ingress, Geobear helps airports remain operational with less downtime.
To learn more about how proactive stabilisation can protect your airport infrastructure, visit geobear.co.uk/airports or speak to a member of the team at 0800 084 3503.
