How can you avoid foundation failure on expansive soils?

1 Identify expansive soils

The first step to avoid foundation failure on expansive soils is to identify them before starting any construction project. Expansive soils are typically clayey soils that have high plasticity and low permeability. They can be found in various regions and climates, but are more common in arid and semi-arid areas. You can use soil maps, geotechnical investigations, laboratory tests, and field observations to determine the presence and extent of expansive soils on your site.

2 Design suitable foundations

The second step to avoid foundation failure on expansive soils is to design suitable foundations that can accommodate the soil movements and minimize the stress on the structure. Depending on the soil characteristics, the structural load, and the site conditions, there are different types of foundations that can be used. Deep foundations, such as piles, piers, or caissons, transfer the load to a stable soil layer below the expansive soil zone. Shallow foundations, like mat or raft foundations, spread the load over a large area and reduce differential settlement. Voided foundations, like suspended slab or waffle slab foundations, create a gap between the soil and structure and allow for expansion and contraction. Isolated foundations, such as pad or strip foundations, are separated from adjacent foundations and structures by joints or flexible connections. When properly designed, these foundations can help ensure that your structure is secure.

3 Implement soil improvement techniques

The third step to avoid foundation failure on expansive soils is to implement soil improvement techniques that can reduce the swelling potential and increase the strength and stability of the soil. These techniques include moisture control, such as drainage, irrigation, or vapor barriers, to maintain a constant moisture content; compaction, like mechanical or dynamic compaction, to increase the density and decrease the void ratio; stabilization, like chemical or cementitious stabilization, to bind the soil particles and reduce plasticity and swelling; and reinforcement, such as geosynthetics or soil nails, to enhance the tensile and shear resistance.

4 Monitor and maintain the foundation

The fourth step to avoid foundation failure on expansive soils is to monitor and maintain the foundation during and after construction. You can use various instruments, such as settlement plates, inclinometers, or strain gauges, to measure the soil movements and the foundation deformations. You can also inspect the foundation regularly for any signs of distress, such as cracks, tilts, or leaks. You can perform preventive or corrective actions, such as repairing, grouting, or underpinning, to restore the integrity and functionality of the foundation.

5 Follow design codes and guidelines

The fifth step to avoid foundation failure on expansive soils is to follow the design codes and guidelines that are applicable to your project. These recommendations and specifications can be found in sources such as the American Society of Civil Engineers (ASCE) with their ASCE 32-01: Design and Construction of Frost-Protected Shallow Foundations, the International Building Code (IBC) 2018: Chapter 18: Soils and Foundations, the National Building Code of Canada (NBCC) 2015: Part 4: Structural Design, and the Australian Standard (AS) 2870-2011: Residential Slabs and Footings. Following these codes and guidelines will help ensure your project is designed, constructed, and maintained properly.

6 Consult with experts

The sixth step to avoid foundation failure on expansive soils is to consult with experts who have experience and knowledge in dealing with expansive soils. You can seek advice from geotechnical engineers, structural engineers, or foundation contractors who can help you with the soil investigation, the foundation design, the soil improvement, the foundation monitoring, and the foundation maintenance. You can also learn from the best practices and case studies of other projects that have successfully handled expansive soils.

7 Here’s what else to consider

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