Global foundational engineers and environmental experts must overcome expansive clay as it proves to be a vicious fighter against building foundations.
In wet and humid climates, bentonites, vermiculites, chlorites and more expand, causing cracks in basements and sagging slopes in perfect flooring.
Can geotechnical professionals continue to build on clay soils when so much is at stake for a structure’s longevity? Explore how the industry is combatting the challenges expansive clay poses.
Site Investigation and Soil Classification
Before construction begins, a thorough site investigation and soil analysis can alert builders of clay-dense plots. Results will alert any other soil integrity concerns that may jeopardize the project. For example, the site must not contain aspects that encourage high moisture conditions, so measures must be in place to prevent erratic shifts when construction is complete.
Geotechnical drilling is often the most reliable testing procedure for identifying soil characteristics. Planners will know the concentration of expansive soils and what types are present, providing insight and permeability and plasticity after lab testing, drilling or soil maps are finalized.
It may not be possible to uproot the clay entirely, but the foundation’s materials may consider swelling potential more thoughtfully. They could also remove some percentage of the shallow expansive clay with fill material to make it less malleable. These soil packs act as barriers.
Sampling soil notifies foundational engineers what materials to use, so what are the appropriate strategies for stopping drywall splitting and unexpected shifts? They must collaborate with civil engineers as their project managers, environmental specialists for impact and urban planners for zoning and legalities, if applicable. Choosing the right design by considering all viewpoints is critical because of each style’s depth potential and soil containment capabilities, such as:
- Reinforced concrete: With several formations to explore, including waffle mat and slab-on-grade, concrete’s heft and thickness provide veritable defences against vertical expansion. Many are optimized for shallow depths, making them easy to install.
- Deep pile foundations: Focuses on diving into deeper layers of bedrock to distribute building weight, relying on their stronger nature to alleviate surface burdens.
- Raft foundations: Achieves more equivalent weight transfer in the building’s footprint instead of localizing it in one spot. Soil that is less encumbered is more likely to swell.
Other recent innovations, like metakaolin from Kaolin clay, could be an eco-friendly alternative to more carbon-intensive materials like concrete. Studies show its potential for reducing the shrinking and swelling of expansive soil samples and mixing it with additives like fly ash to improve its stabilization qualities.
Another environmentally considerate option in research is recycled concrete. Trials explored its employment to stabilize expansive clay over 10 years with notable success.
This is a broad umbrella for a medley of solutions, including integrating subsurface drainage systems and preventing water from infiltrating all aspects of the building — not just the foundation. Builders should consider the climate and surrounding ecological fixtures impacting the soil’s water retention. Regarding all exterior openings will keep the building secure in the event of a natural disaster, intense heat wave or torrential downpour.
For example, yearly snowmelt might come in short bursts but could cause lasting damage, especially if the structure is near a water body. This is where peripherals like geosynthetic mats and liners come in handy. Retaining walls is another option if terracing.
Considering the plot’s slope grading and surrounding vegetation are a few ways to maximize on environmental protection that may already exist on the property. The area may be naturally attuned to diverting water away from a building’s foundation, or engineers could rework the area to do so.
Soil Stabilization Techniques
Choosing adequate foundation materials or supplementing soil are a few options, but mechanical and chemical stabilizers are out there to lessen stressors from expansive clay.
Mechanical stabilizers focus on enhancing the soil’s load-bearing potential. Added pressure prevents it from expanding. Techniques include mixing the soil with fillers and compacting it to give it less room to change volume. Some may add more infrastructure, like steel bars, to make it even more robust.
Chemical methods rely on injecting additives to change the soil’s behaviour. Other options exist, as seen with how fly ash improves metakaolin, like lime kiln dust. Experts are studying anionic polyacrylamide additives, which could help everything from buildings to pavement from seasonal moisture fluctuations.
Monitoring and Maintenance
Most preventive measures are before or during construction, but what about after? Maintenance and oversight are essential to stopping expansive clay. Changes may occur gradually over the years or shortly after project completion if weather and precipitation become erratic.
One tool assisting with this is settlement plates, which are in-ground devices tracking soil movement. Automated systems take measurements and collect data for constant observation. It alerts experts when to execute inspections. Other tools include:
- Magnetic extensometers
- Wire piezometers
They determine slope changes, settlement heaving and pore water pressure at varying elevations to deliver a comprehensive perspective on soil activity over time.
Defeating Soil Expansion Challenges
Foundational engineers have the tools and resources to stop expansive clay from becoming catastrophic to buildings. A bout of rain should not destroy a home or office building from the ground up, so these methods eliminate fears. It allows foundational engineers to work on lands with diverse soil compositions while maintaining project quality and client satisfaction.
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