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Reinforced soil

Reinforced soil: techniques, applications, and benefits in civil engineering

Reinforced soil or soil reinforcement is a topic of major importance in civil engineering and provides modern advancements to enhance soil mechanical behavior by giving additional internal structures.

What is meant by reinforced soil?

Reinforced soil is the composite material of natural soil and man-made fibrous materials. These soils being less prone to deformation, withstand external loads and environmental factors. This method has gained prominence due to its cost-effectiveness and adaptability, finding applications in diverse infrastructure projects including bridges, road embankments, and retaining walls.

Key components of soil reinforcements

Reinforced soil consists of two main ingredients, that is, the soil and the reinforcing materials. Geosynthetics, metals trips and sheets, natural materials, and composite reinforcements are the widely used reinforcing elements. They enhance the stability and tensile strength of the soil.

Geosynthetics

Geosynthetics like geogrids, geotextiles, geomembranes etc help improve the soil strength. It is of great importance to distribute loads, decrease soil movements, prevent erosion and enhance the whole structural capability.

Soil types and properties

Soil characteristics and properties play a critical role in the selection of optimal soil stability strategies. Soil is usually divided into four groups (Sand, clay, silt, and gravel). The degree of soil reinforcement efficiency depends very much on the properties of soil like particle size, moisture content and shear strength.

Methods of soil reinforcement

Mechanical reinforcement techniques

Mechanical methods are common for reinforcing soil in construction.

  • Geogrid reinforcement: Geogrids, which are often composed of polymer materials, improve the tensile strength of soil. It is used to strengthen the weak soils, build retaining structures through providing low creep.
  • Soil nailing and its applications: In soil nailing, slender reinforcing bars called nails are inserted into pre-drilled holes in the soil for the purposes of reinforcing slopes, excavation works, and already built infrastructure.
  • Reinforced earth walls: Reinforced earth wall structures are a contemporary substitute for conventional strengthening walls. These walls are constructed by applying compacted earth fill with reinforcing materials to form a composite structure providing long-term strength

Chemical reinforcement methods

  • Soil-cement stabilization: Soil cement stabilization is a construction method of integrating soil with cement to produce a dense, compacted layer. It is adapted for use in applications such as pavement, embankment, and foundation support. It is widely used in low PI, coarse-grained soils.
  • Soil-lime stabilization techniques: Lime stabilization is the inclusion of lime to soils which is particularly useful in soils with a high clay content. Lime treated soil can develop long term, permanent strength in reactive soils resulting in soil stabilization.
  • Other chemical additives for soil enhancement: Sometimes, chemical ad mixtures such as fly ash and calcium chloride are introduced in the soil to improve strength and water resistance.

Methods of soil reinforcement

The interaction between soil and reinforcement materials plays a key role in strengthening structures.

Interaction between soil and reinforcement materials

When soil and reinforcements work together, they significantly improve shear strength.

  • Shear strength improvement: Soils resistance to deformation under the sheer internal load increases with the introduction of materials that interact with soil particles and hence the ground becomes more stable.
  • Load distribution mechanisms: Reinforced soil spreads the load over a wider area and avoids concentration of stresses which can lead to heavy load and hence better performance in a geosynthetic reinforced soil

Factors influencing reinforcement effectiveness

The primary soil type operative in soil reinforcement is just one of the many parameters that determine the reinforcement soil’s successful performance. Geosynthetics with high tensile strength and high elongation capabilities can stretch under load preventing rupture of the structures. The proper compaction of the soil is also critical to ensure effective load transfer.

Applications of reinforced soil in civil engineering

1. Retaining structures and walls

Reinforced soil has a common application in the construction of retaining walls that support the slopes and control erosion.

  • Mechanically stabilized earth (MSE) walls: In MSE walls, the backfill is reinforced with adequate soil to form a flexible and high-strength structure which is prefabricated for use in highways, bridges and large infrastructural projects. MSE walls are popular due to their nominal cost, ability to withstand significant settlement and differential movements without failure.
  • Reinforced slopes and embankments: Reinforced slopes provide stability on sloped surfaces. Compacted earth structures, particularly road and railway embankments, are made of reinforced soil that helps in controlling shifting and erosion.
Reinforced soil structure for landfills with StrataSlopeTM system
Reinforced soil structure for landfills with StrataSlopeTM system

2. Pavement construction and stabilization

Soil construction has been effectively utilized in the construction of roads and pavements to enhance load distribution and load bearing capacity.

  • Benefits of reinforced soil in road construction: Infrastructure development which employs reinforced soil in the road construction stabilises the structure while minimizing maintenance requirements and extends the lifespan of the road.
  • Use in airport runways and taxiways: Reinforced soil also provides good support for the heavy loads found in airport runways and taxiways.

3. Foundation support and stabilization

Reinforced soil ensures stable foundations for various structures, even in challenging soils.

  • Deep foundation systems using reinforced soil: Deep foundations are critical for increasing the load bearing capacity of large structures, thereby reinforcement using geosynthetics prevents tilting by confining the soils.
  • Stabilising weak soils for heavy structures: Weak soils need reinforcement to bear the weight of heavy structures, by providing additional tensile strength and limiting the lateral displacement of the soil.

Advantages of using reinforced soil

Reinforced soil offers several advantages that make it a preferred choice in civil engineering.

  • Enhanced stability and load-bearing capacity: Reinforced soil enhances stability to such an extent that structures can be constructed to carry very heavy loads.
  • Cost-effectiveness and construction efficiency: This is because expensive materials and contingent works are not required which reduces the project costs and the construction periods.
  • Environmental benefits of using geosynthetics: The use of geosynthetics in reinforced soil applications reduces ecological impact in several civil engineering projects by minimizing the consumption of raw materials, carbon footprint reduction, waste minimization, and soil erosion reduction
  • Flexibility in design and application: Reinforced soil finds use in all kinds of projects from pavements to huge structure construction  offering a reliable and convenient solution.

Reinforced soil changes the construction of buildings by guaranteeing strength, durability, and effectiveness of construction work in all difficult conditions.

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