When we say we’re standing on “solid ground,” it assumes that the earth beneath our feet is always going to be the same. However, that’s not always the case. What appears to be unchanging and dependable may be a lot more volatile than we think. Contractors can learn this the hard way, building on top of soil that becomes less capable of supporting all the added weight than it was in the first place. This results in buckling asphalt, cracked concrete foundations, and a lot of expensive and complicated rework.
The culprit in most of these instances is expansive soil, which can shrink and swell depending on their moisture content. Any builder committed to delivering successful and cost-effective projects needs to understand how to spot expansive soils and how to deal with them. At Rock Solid Stabilization & Reclamation, Inc., we’ve helped countless contractors overcome the challenges of working with expansive soil, so we present this guide to help you with your next project.
What Makes Soil Expansive?
Clay content is the single-biggest factor in making soils expansive. Soils that contain a lot of clay minerals have greater shrink-swell characteristics than other types of soil. As these expansive clay soils absorb moisture, they can swell and grow in volume. On the other end of the spectrum, they also contract as moisture evaporates.
How Do Expansive Soils Impact Construction?
The shrink-swell potential of soil can have tremendous effects on anything built on top of it, and none of them are good. Without proper mitigation techniques for expansive soils, the characteristics of the soil will change as moisture levels change. This can lead to problems including:
- Cracked concrete caused by additional pressure from swelling soils
- Foundations settling as expansive soils shrink as they dry
- Asphalt roadways and hardtop surfaces buckling and developing potholes
- Interior walls bowing as the foundation is lifted up by expanding soil
Ways to Spot Expansive Soils
Although it’s recommended to have soil tested under laboratory conditions to determine its exact swelling potential, there are some visible warning signs of expansive soils that builders should watch for when conducting initial site inspections. Some of the most common physical indicators of expansive soil with high clay content include:
- Deep cracks that form during hot, dry weather
- Soil can be formed into a ball
- When dry, the surface has a popcorn-like texture
- A sticky and soft consistency when wet
Field testing is an important first step when evaluating the plasticity and shrink-swell potential of soils on a construction site. However, lab testing is still necessary. Samples of soil from the site are tested using proven techniques such as Atterberg limits tests to evaluate its moisture content as well as the amount of clay minerals present in the soil. This provides builders with the most information about what they’re up against and helps them determine the most appropriate steps to take next.
Methods for Tackling Expansive Soils
If expansive clay soils are detected on the jobsite, the next step is for the engineer and builder to consider the best strategies for stabilizing them. There are several techniques that can be used to change the physical properties of expansive soils so they become far less unpredictable and more capable of supporting the finished structure. The most commonly employed of these methods include:
- Chemical Stabilization: Adding chemical compounds such as quicklime, fly ash, cement, or lime kiln dust can change the qualities of the soil enough to bring stability. These help dry out the soil while also strengthening the bonds between particles so the resulting ground is stronger and won’t shrink or swell.
- Mechanical Stabilization: In some cases, compacting natural soils may be enough to prevent shrinking and swelling from affecting the resulting structure it supports. In other cases, it may be advantageous to mix a different type of soil into the soil on the site or use geosynthetic materials to hold the soil in place.
- Drainage: Grading and/or the installation of drainage systems can provide protection against the negative impact of expansive soils in some instances. This keeps water from settling in places where expansive soils are, which prevents them from absorbing it and swelling.
Working with Rock Solid to Mitigate Expansive Soils
Rock Solid Stabilization & Reclamation, Inc, works closely with builders and contractors to ensure proper site conditions so their work is always on solid ground. Our team of experts understands the risks of working with expansive soils better than anyone and using our expertise we can choose the stabilization strategy that makes the most sense for the situation. Whether your next site needs chemical or mechanical stabilization, we employ the most advanced and effective techniques for achieving the most stable subgrade.
Thanks to our extensive knowledge and commitment to innovation, we have the skills necessary to find the most efficient and cost-effective solutions to your project’s requirements. If you want to learn more about everything we can do to help you fight expansive soils and achieve long-term stability, reach out and connect with a member of our team today to discuss your project and what we can do for you.