How is soil stabilization for road construction done?
Soil stabilization is the modification of the natural soil’s intrinsic properties to improve its load-bearing capacity, shear strength, and overall performance. This procedure employs mechanical, chemical, or biological methods, utilizing materials such as cement, chemical additives, or various agents to enhance soil strength and stability.
The base is an important part of road construction, as it transfers traffic load to the underlying subgrade. The long -term performance of the pavement structures depends on the stability of the underlying soil. Natural soil often lacks essential engineering properties in its natural condition. Thus, soil stabilization is necessary to modify these soils for construction.
What are the benefits of soil stabilization?
1. Increase in bearing capacity with marginal soil:
Soil stabilization strengthens poor-quality soil which supports heavier loads. This negates the need for replacing the soil with expensive high-quality aggregates. Additives like binders function as chemical binding agents, while materials like aggregates improve the particle size distribution. This creates a stronger soil matrix with a better load-bearing capacity.
2. Improved stability:
Stabilized soils are more durable against traffic loads and environmental stress. As a result, pavements last longer, require less maintenance, and help lower overall construction and repair costs.
3. Moisture control:
This reduces shrinking and swelling caused by moisture fluctuations. Stabilization can be obtained by adding drying agents or by modifying the soil’s properties to provide a more balanced and sound foundation.
4. Erosion control:
Unstabilized soils can erode because of factors like wind, rain, and traffic. Stabilization binds soil particles, reducing detachment risks. This helps reduce sedimentation in waterways caused by erosion. This method also serves to reduce sedimentation in water bodies brought about by erosion, a huge advantage for conservation of the environment. Stabilized soils retain their form even during harsh weather, so fewer emergency repairs are required.
5. Extended maintenance cycle:
Soil stabilization enhances the longevity of roads. Stabilized roads are less susceptible to problems such as potholes and cracks, resulting in reduced repairs and savings. With minimized maintenance interruptions, roadways can offer improved service and safety over longer durations. This not only boosts the functional value but also the economic value of the infrastructure.
6. Cost efficiency:
Soil stabilization provides a cost-effective alternative to conventional dig-and-dump methods by reducing the need for extensive excavation and soil replacement. Strengthening the in-place material lowers dependence on imported aggregates, minimizes disposal volumes, and reduces transport requirements—streamlining construction while maintaining performance and efficiency.
7. Environmental impact:
By reducing reliance on raw material transport and excavation, soil stabilization helps cut emissions during construction. The technique also plays a role in erosion control, keeps sediment away from nearby water sources, and reduces dust especially on unpaved roads, supporting better site management.
Clay soil
Clay is a type of soil with fine grains, mainly made up of particles that are less than 2 micrometers in diameter, referred to as clay minerals. Clay possesses high plasticity, which allows it to be shaped when wet, but it turns hard and brittle as it dries.
Clay mineralogy
Clay mineralogy relates to the specific types of clay minerals present in soil. The specific type of clay mineral (kaolinite, illite, smectite) affects how the clay behaves due to variations in its chemical makeup. For instance, smectite clays exhibit higher swelling potential compared to kaolinite clays due to their unique crystal structure.
Cement
Due to its widespread availability and effectiveness across various soil types, cement is a favored option for soil stabilization. To successfully use cement as a stabilizer, it is essential to manage both the cement and water content. The perfect mixture for cement stabilization provides enough water for thorough cement hydration and workability, which is vital for reaching the intended compacted density and strength.
What are the methods of soil stabilization?
Soil stabilization techniques are categorized into three main groups: mechanical, chemical, and biological. Each method offers its advantages and applications depending on the specific soil conditions and requirements of the project.
Mechanical methods:
Mechanical stabilization involves physically altering the soil structure to enhance its properties.
- Compaction: Compaction involves removing air pockets to physically compress the soil. This enhances the soil’s load-bearing ability by decreasing its volume and boosting the internal friction among particles. Typical compaction methods include dynamic compaction (which entails repeatedly dropping a heavy weight) and vibro compaction (which uses vibrations for compaction).
- Blending: Blending is used to improve weak soil by mixing it with material that has a better range of particle sizes. For example, adding well-graded aggregate to uniform soil helps improve how the particles fit together, which increases strength and stability.
- Reinforcement: Geosynthetics or natural/synthetic fibers are often employed to reinforce the soil. When placed within the soil, geosynthetics improve its performance through different mechanisms. Geocells provide confinement to the infill material, which improves the soil’s bearing capacity. Geogrids provide tensile reinforcement, interlocking with soil particles to resist pulling forces and distribute loads more effectively.
Chemical methods:
Introducing chemical additives that react with the soil to modify its properties is termed the chemical stabilization of soil. These additives bind soil particles together, augment strength, and alter water resistance.
- Lime: Lime stabilization is particularly effective for clayey soils with moderate to high plasticity. It changes the soil’s properties by adding lime which triggers a chemical reaction. This technique is most useful when the correct amount of lime is used to stimulate cation exchange.
- Fly ash stabilization: When mixed into soil, pozzolanic fly ash reacts with calcium hydroxide (often provided by adding lime or cement) to form stable, cementitious compounds that bind soil particles and increase strength. Fly ash offers lower costs and can be used in high-moisture soils because of its drying effect.
Biological methods:
The biological stabilization of soil makes use of natural processes to boost soil properties, primarily for erosion control. It involves planting vegetation whose root systems improve long-term soil cohesion and reduce vulnerability to erosion.
What measures does Strata Geosystems take for soil stabilization?
Unstable subgrade soils create major challenges in roadway improvement projects. Strata addresses these issues with geosynthetic solutions like StrataWeb geocells and StrataGrid geogrids. By reinforcing the subgrade, these systems build a stronger, more reliable foundation. This reinforcement also reduces the need for thick base and sub-base layers, leading to noticeable savings in material use and overall construction costs.
StrataWeb geocell features a unique honeycomb-like structure that excels at confining infill material. This reduces movement and lateral spreading, resulting in better load support and slope erosion resistance. StrataWeb is offered in various forms, including deep-textured and perforated variants that improve drainage and increase friction with the fill material. Each unit can be tailored to project-specific needs. A collapsible structure allows easier transport and faster installation on site.
StrataGrid reinforces soil by providing tensile resistance. Its grid structure interlocks with the soil or aggregate, allowing the composite material to withstand pulling forces and better distribute loads. Manufactured from high-tenacity polyester yarns and coated with a UV-stabilized layer, the material is built for long-term exposure. With low creep characteristics, StrataGrid ensures consistent performance in slope stabilization and other reinforced soil structures.
Strata’s soil stabilization solutions have improved projects globally
Innovative soil stabilization in Aamby Valley with StrataWeb® geocells
In the high-rainfall zone- Aamby Valley, it was observed that the eroding soil threatened nearby structures. Conventional retaining wall methods were unsuitable due to limited time. Strata delivered an efficient alternative using StrataWeb geocells to stabilize the soil and support the foundation system. The gravity structure was formed by stacking infilled geocell panels in successive layers. The bottom geocell layers were anchored in their expanded position using steel stakes and then infilled and compacted with a vibratory plate tamper. The geocell structure efficiently reinforced the soil and prevented further erosion. A tiered structure of the wall created a natural-looking ledge that was suitable for the growth of vegetation, while the StrataWeb® system made sure the structure was no longer vulnerable to heavy rainfall.
Technocraft Industries yarn mill roads strengthened with StrataWeb® geocells
In Amravati, India, Technocraft Industries faced a serious obstacle during the construction of the internal road network of their new yarn mill. The expansive soil on the site gave a challenge to build a strong pavement foundation as it was prone to the movement. Strata’s experts recommended the use of Strataweb Geocell to strengthen the foundation to improve the load-bearing capacity of weak soil. Geocells distribute the load over a broader area, reducing the vertical stress on the weak underlying subgrade soil, which in turn can allow for a decrease in the required thickness of overlying pavement layers. It also ensured the longevity of the pavement by strengthening the soil. The ease of installation of StrataWeb, combined with its ability to streamline construction, provided a cost-effective alternative to a traditional 200 mm granular sub-base layer.
Strata Geosystems offers reliable soil stabilization systems designed for long-term use. Modular components help speed up construction, reduce material usage, and lower maintenance over time. Support at Strata is based on engineering insight and matched to the specific needs of each project.