Land stabilization, or soil stabilization, encompasses a range of techniques used to improve the physical and chemical properties of soil. The goal is to enhance the soil’s ability to support weight, resist erosion, and prevent movement for any construction or traffic.
Chemical Stabilization:
. This involves adding chemicals like lime, cement, or polymers to the soil to bind soil particles together and increase strength.
Mechanical Stabilization:
. This includes techniques like compaction, where soil is compressed to increase its density and stability, or the use of geotextiles to reinforce soil.
Vegetative Stabilization:
. Planting vegetation, such as grass, shrubs, or trees, can help stabilize soil through their root systems, preventing erosion and runoff.
Soil Nailing:
. This involves inserting steel bars into the slope to reinforce the soil mass.
Riprap:
. Using large rocks to stabilize slopes and prevent erosion.
Benefits of Land Stabilization:
Increased stability: Soil stabilization ensures that the soil can bear the weight of structures and prevent movement.
Reduced erosion: It helps prevent soil loss due to wind and water, protecting land and water resources.
Improved safety: By preventing landslides and slope failures, land stabilization enhances safety in construction and development areas.
Environmental protection: It helps protect water quality by reducing sediment runoff and preventing pollution.
The instructions for the stabilization are stated in the Geotechnical or Soils Report and it is a guidance of the mixture or proportion of the material needed.
Lime and Cement Soil Stabilization
Lime or cement soil stabilization are one of the most popular means of soil stabilization. This soil stabilization method is done by mixing lime or cement into the soil in order to increase its strength and resiliency. The percentage of lime or cement that gets mixed into the soil varies depending on the native soil’s characteristics. Often, the higher the plasticity, the more lime or cement will be mixed in. Commonly, lime and cement are grouped together since they are very similar, both being used as a binder.
Lime occurs naturally, while cement is synthetic, or manmade. Although, treating the soil with cement or lime is one of the most popular means of soil stabilization, it is most prevalent in paved roads and parking lots.
Lime or cement soil stabilization works by binding all of the soil’s particles together, which results in an increase of the soil’s strength. Since this process calls for adding cement or lime to the soil, practically all soil types are compatible with this type of soil stabilization. While most soil types are compatible with lime and cement soil stabilization, the soil must be analyzed to ensure that the proper additive amount is being used. If a low amount of additive is used, then the soil will not reach the desired strength. If a higher amount is used, then the soil could shrink or begin to crack.
One of the major benefits of lime or cement is the ability to use it on soil that is above optimum moisture. When using a powder form of lime or cement in conjunction with a moist soil above optimum moisture, the soil will be dried quickly, allowing you to compact the soil properly. While the powder method is desirable for applications with very wet soil, it does unfortunately have plenty of health concerns due to the powder being so fine. This poses a safety risk to the workers.
During the application of lime or cement to the soil, you will need to mix it thoroughly. It is important to keep the soil’s moisture content as close to optimum moisture as possible. Upon mixing the soil and lime or cement, the next step is to compact the soil as tightly as possible. Once the soil has been compacted, the soil will begin to cure and will continue for approximately 28 days.
Advantages
Permanent, long lasting
Tried and trued
Compatible with most soil types
Very strong soil
Decreases soil’s moisture content
Disadvantages
Expensive
Potential health concerns
Only for paved roads
Requires extensive soil testing before application
Fly Ash Soil Stabilization
Fly ash soil stabilization is similar to lime or cement stabilization in principle but differs based on the product being used. Fly ash is a byproduct of coal from coal-fired power plants. Traditionally, the byproduct is stored in landfills or ponds, but fly ash can also be used as a bonding agent to increase the soil’s strength. Just as cement and lime stabilization are primarily used for soil stabilization as the subbase to paved roads, fly ash’s primary use is to treat the subbase of paved roads. Because fly ash is a dry additive, one large benefit is using fly ash in soil regularly above optimum moisture. The powder will absorb the moisture and lower the soil’s moisture content.
There are two main types of fly ash, Class F and Class C. Class C fly ash is cementitious and pozzolanic by nature. Once the fly ash is wet, it will harden because of the cementitious nature, while the pozzolanic supplies a silica aspect. Class F Fly ash is only pozzolanic in nature, which means that it will not harden on its own; it will need an activator such as gypsum or calcium hydroxide. The types of fly ash are dependent on which coals the fly ash is derived from, this will vary by location and region.
Typically, fly ash reduces soil stabilization costs compared to lime or cement soil stabilization. Fly ash is essentially a waste product from a different manufacturing process. A large advantage to fly ash is the fact that it is a dry additive, which is extremely helpful and beneficial for high moisture soils. Being a dry additive is also a disadvantage in the fact that the additive can be labor intensive to apply as well as a health concern to workers since the powder possesses an inhalation risk. The cure time is another factor to weigh in when using fly ash. While this can vary depending on the fly ash and soil, the cure time is usually slower than a cement or lime treated soil would be.
Using fly ash as a means of soil stabilization varies in popularity around the world, depending on the location. As the coal-fired power plants decrease in popularity and production, the amount of fly ash that is produced will decrease substantially. This means that in the future, fly ash will be hard to obtain.
Advantages
Permanent, long lasting
Compatible with most soil types
Various types for different uses
More cost effective than cement or lime
Usable with high moisture soils
Disadvantages
Health concerns
Labor intensive
Availability based on coal-fired power plants