Soil stabilization is a term that denotes the physical, mechanical, biological, chemical, or combined method of changing natural soil for a specific purpose.
Soil may need to be stabilized in order to increase its weight-bearing capabilities or improve its tensile strength. Understanding the various types of permanent and temporary soil stabilization methods is essential for improving load-bearing capacities to support building foundations, road pavements, and other engineered structures.
The Importance of Soil Stabilization
Natural soil doesn’t always have the properties necessary to support construction projects. Unless the soil is stable enough to support a road or building, the structure can easily be washed away by flowing water, especially during a flood or torrential rainfall.
Soil that hasn’t been stabilized tends to contain larger particles than stabilized soil. These larger particles allow the soil to sink, which can result in literal sinkholes due to the soil’s inability to bear the weight of traffic.
With stabilized soil, the particles are crushed into smaller sizes, resulting in a compact soil that holds up well to manmade structures.
Types of Soil Stabilization
There are many materials and methods utilized in stabilizing soil, including:
- Bitumen (asphalt).
When electricity is used in soil stabilization, a direct current is sent through the soil in order to drain and discharge water. Draining the soil strengthens it, lowers the soil’s water table, creates an anti-seepage curtain, and provides stability to slopes, allowing construction to take place in slide-prone areas, trenches, pits, and quarries.
Electro-osmosis, however, is only used in soil stabilization when no other method is suitable. That’s because the process requires highly sophisticated and specialized equipment along with a high amount of electricity to achieve the desired result.
Various types of geotextiles are frequently used in soil stabilization efforts. High-quality geotextiles like coir have been used to control soil erosion, support roads, improve drainage, and promote quick vegetation.
If you’re looking for a natural, eco-friendly method to stabilize soil, these versatile, permeable soil stabilization products are effective, low-cost options. Coir is a geosynthetic made from coconut fiber that can be synthesized for specific applications, allowing it to meet a variety of requirements.
Soil Cement Stabilization
Cement is often used as a low-cost means of preparing foundations for parking areas, highways, residential streets, and airport runways. The technique involves mixing soil with cement and water to form a strong soil-cement. Also known as a cement-treated aggregate base or cement-stabilized base, soil-cement can involve any type of soil and gravel rock combination.
Prior to construction, it’s important to perform laboratory tests to establish the soil’s water requirements, cement content, and compaction.
Testing ensures the soil-cement stabilization mixture has enough durability and strength to last. Soil-cement is made in a central mixing plant or on-site depending on the project, but there are always four steps involved:
- Spreading cement.
Curing is important for preventing water evaporation and ensuring maximum strength. In most cases, a light coating of bituminous material is used to prevent moisture loss.
Lime Soil Stabilization
Mixing lime with soil can significantly improve construction sites. When the right amount of lime is added to a reactive soil, the soil stabilizes and gains strength through a process called pozzolanic reaction. This chemical reaction converts a silica-rich soil with no cementing properties into a calcium silicate with excellent cementing properties.
In fact, the pozzolanic reaction was the main reaction involved in creating Roman concrete, which was used to build not only ancient roads but also impressive structures like the Pantheon.
Today, lime continues to be used as a trusted method of stabilizing soil via pozzolanic activity. The key is using a reactive soil along with a good mix design protocol to improve the soil’s strength and long-term durability.
Bituminous Soil Stabilization
Bitumen is a black viscous mixture used mainly in roofing and road surfacing. Most people know it as asphalt. The concept of bituminous stabilization is similar to soil-cement. Essentially, a controlled amount of bituminous material is added to soil and mixed to increase its load-bearing capacity and make it water-resistant.
Bitumen is sticky by nature, which helps it hold the compacted soil particles together. The result is a strong layer that prevents groundwater from being absorbed. As such, bitumen is excellent for waterproofing.
Chemical Soil Stabilization
Chemical soil stabilization involves altering the soil’s properties via chemicals like chrome lignin, polymers, sodium chloride, sodium silicate, calcium chloride, and other chemicals. Chemical reactions can cause the soil’s structure to change, removing space between the particles and making it more compact, leaving no room for air or water to penetrate it.
Polymer soil stabilization is a popular chemical technique for geotechnical engineering, agricultural, and construction projects. Adding various polymers to soil can reinforce roadbeds, reduce erosion, support soil structure, increase soil shear strength, and improve water retention.
Soil Stabilization Equipment
Once you know which soil stabilization method to use, you’ll need to invest in the right equipment. Soil stabilization machines are designed with different approaches in mind, and each technique requires different equipment and machinery to get the job done. While your needs may vary, these are some of the most widely used soil stabilization machines.
On sites where dust may pose an issue, an integrated mixer spreads a controlled amount of lime, cement, or other material directly in front of a mixing drum. The binding agent is immediately mixed with the site’s soil, eliminating dust issues and creating a stabilized soil on the spot.
Spreader units are either self-propelled or tractor-towed, but their purpose is to spread all sorts of dry binding agents. Although they’re often called cement spreaders, they can spread large quantities of fly ash, lime, cement, and similar materials with minimal dust.
Cold planer machines are a low-cost option designed to grind asphalt. Also known as asphalt milling machines, cold planers feature rotating drums that remove and grind surface asphalt. The pavement can then be loaded on a conveyor and removed from the site or mixed with soil.
Reinforcing the soil provides the perfect foundation for a variety of engineering feats. When you choose the proper soil stabilization technique, you can rest assured your construction project will stand the test of time.