What are the most common current UK geological risks?
The UK faces a variety of geological hazards due to its diverse geological conditions posing risks to building foundations. Risks which have been identified include:
- Heave and Subsidence in shrinkable cohesive soils also known as shrink-swell,
- Reduced soil strength from groundwater changes and increased pore water pressure,
- Dissolution and hazards related to chalk, limestone, evaporates, and other mining areas,
- Collapse settlements in earthworks and fills,
- Green infrastructure – additional tree planting can increase shrink-swell soils.
What will happen when geological risks are ignored?
Ignoring these risks can lead to unexpected costs arising later in the design or construction programme, difficulties in obtaining necessary approvals or delays on site.
The effects of climate change are expected to increase damages to domestic properties, such as wall cracking, sticking doors and windows, and potential utility disruptions. Many existing buildings, constructed without considering climate-related impacts, may already face unavoidable future disruptions. Costly remedial options, like widespread underpinning of foundations or tree removal, are impractical and unsustainable.
Current planning frameworks require early consideration of all potential hazards to ensure that appropriate measures and materials are used to design structures and foundations to mitigate these risks, although due to the nature of the predicted changes it will be essential, therefore, to modify existing approaches to defining hazard and risk potential in line with future UK climate projections.
What is the solution to geological risks for new developments?
With the growth of new housing developments and commercial structures, it is vital to choose a foundation solution which will counterbalance long-term geological risks. To address the risks posed by climate change and geological hazards, piled raft foundations offer a robust solution for new build developments in the UK.
Piled raft foundations provide several advantages that make them well-suited to withstand the challenges associated with climate change:
Uniform Load Distribution
Piled raft foundations spread and transfer the load of the building to stronger soils and rocks at depth below the site, reducing the risk of differential settlement caused by shrink-swell or soft, shallow soils. By distributing the weight across a broad, continuous slab, the building loads are transferred to the piles more evenly, and piles can be placed anywhere beneath the slab, leading to a more efficient design.
This even distribution and founding at depth help to stabilise the building, preventing uneven settlement that can occur when soils expand and contract due to moisture variations. Consequently, piled raft foundations provide a more stable and durable base for buildings in areas with challenging soil conditions.
Resistance to Soil Movement
Piled raft foundations avoid issues around damage from soil movement, such as subsidence or heave, due to their design’s ability to accommodate minor ground shifts without compromising structural integrity. Unlike traditional shallow foundations that can be affected by uneven soil settlement, piled raft foundations distribute the building’s load evenly across a wide area. Whether the soil experiences slight subsidence due to settlement or upward movement (heave) caused by increased moisture content, piled raft foundations can maintain stability and prevent structural issues, ensuring the long-term durability of the building.
Durability in Variable Conditions
Piled raft foundations are more durable in areas with variable soil conditions, including those affected by increased pore water pressure or the dissolution of soluble rocks like chalk and limestone.
Piled raft foundations are more durable in areas with variable soil conditions because they can be designed to take into account the risk issues. Shallow bearing foundation options to accommodate such risks quickly become very expensive. Reinforcement in the design of piled rafts further enhances their strength and resilience to various stresses.
Adaptability to Green Infrastructure
Piled raft foundations can be designed to coexist with green infrastructure, such as urban tree planting, by allowing for adjustments in the layout and accommodating future tree growth without risking structural damage. By incorporating design adjustments like root barriers and planned root pathways around the foundation, these measures direct tree roots away from the solid slab, preventing interference and minimising the risk of structural damage.
Conclusion – A strategic choice
In conclusion, piled raft foundations are a strategic choice for new build developments to enhance resilience against the diverse and evolving geological hazards in the UK. By incorporating these foundations, developers can better safeguard buildings against the impacts of climate change, ensuring longevity and structural stability in the face of future environmental challenges.
