Geosynthetic solutions for expansive soils

An ongoing challenge for geotechnical engineers is addressing the impact of expansive soils on our infrastructure.

Expansive soils are clay soils that due to their mineral composition (montmorillonite, bentonite and others) attract and absorb water causing them to expand in volume as more water is absorbed. In dry conditions these materials, which might have expanded in the past, dry and consequently shrink in volume causing surface cracks and uneven settlement.    

As the availability of water changes over time these materials go through shrink and swell cycles that cause volume change. This can cause damage and safety concerns to infrastructure like roads, utilities, buildings and bridges. The expansion of this material can also generate stress on less flexible structures causing structural distress. In roads, drivers may encounter what some might describe as a “rollercoaster ride” due to the differential swelling along the road. Structures may experience cracks in foundation walls and misaligned elements like windows and doors.  

There are four general solutions that mitigate the impact of expansive soils. 

1. If the depth of the material is shallow and lateral extent small, a reasonable solution would be to remove it and replace it with more stable material. This solution quickly becomes expensive but in the right location can eliminate the risk from the expansive soils.    
2. Since the change in moisture is the cause of most of the issues described, introducing a moisture barrier or a geomembrane along the edge of the element being protected is another solution. This can be a cost-effective solution but also has some considerations such as vertical movement of groundwater as well as installation challenges at depth.
3. Chemical stabilization includes mixing chemical additives such as lime, cement, fly ash, or other commercially available products. These additives change the ability of the clay to absorb water. This solution can treat large areas efficiently and is one of the most common solutions for projects with a large footprint such as miles of roads. There are some environmental, constructability and long-term performance considerations that need to be addressed.
4. Geosynthetics, particularly geogrids and geotextiles, can also be used to distribute loads to the subgrade in addition to resist the tensile stresses generated during shrink swell cycles. 

The impact of expansive soils is a complex problem that continues to cause severe damage to infrastructure. All the solutions described above have demonstrated benefits but also come with considerations for the specific application and location. As land usage continues to place new construction in more challenging conditions the use of geosynthetics continues to emerge as an efficient option to address the impact of expansive soils.

There is a wide range of available geosynthetic products that can be used to address this complex issue. The following are examples of various product types and corresponding applications.

• Geomembranes – provide a barrier controlling the flow in and out of the work area.
• Geotextiles – provide separation and filtration to prevent migration of soil particles causing the deterioration of select fill properties.  
• Geogrids – provide tensile resistance, lateral restrain, and reinforcement of the select fill. These effects increase overall stiffness, improving confinement which reduces cracking of the section.  
• Geocomposites and some geotextiles – Can function as a capillary break. A capillary break provides a vertical barrier by interrupting the wicking of moisture from deeper layers. These geosynthetics also provide a path for water away from the expansive soils.  

Geosynthetics provides an adaptable solution which can improve constructability, reduce time, and cost. Geosynthetics can also improve the sustainability of the project by reducing excavation and the need for imported materials as well as the impact caused by chemical stabilization. As with all engineering solutions, there is never one approach.  Although geosynthetics work well in many cases they may also be used in combination with other solutions. Project engineers need to evaluate the suitability for the specific site conditions and design criteria. 

For additional information:

• Roodi, G. H., & Zornberg, J. G. (2020). Long-Term Field Evaluation of a Geosynthetic-Stabilized Roadway Founded on Expansive Clays. Journal of Geotechnical and Geoenvironmental Engineering, 146(4), 05020001. https://doi.org/10.1061/(ASCE)GT.1943-5606.0002206
• Zornberg, J. G. and Roodi, G. H. (2021). Use of geosynthetics to mitigate problems associated with expansive clay subgrades. Geosynthetics International, 28(3), 279–302. https://doi.org/10.1680/jgein.20.00043
• Wang, X., Zhang, L., & Liu, Y. (2025). Influence of geogrid reinforcement on the cracking characteristics of expansive soils during evaporation. Geotextiles and Geomembranes, 53(2), 102–115

Daniel E. Alzamora, P.E., is a contributing editor for Geosynthetics and has spent more than three decades in the geosynthetics industry in both the public and private sectors.