What is bed stabilization and for what purpose is it performed?

As mentioned in the introduction, bed stabilization is a process that improves the geotechnical parameters of soil, the speed of project execution, and increases the operational lifespan of soil. This method is widely used for improving soft and loose soils, expansive soils, compressible or collapsible soils, and embankments, and it greatly aids in the economical and safe execution of various projects, including road construction, subgrade for railways, and stabilization of riverbeds and embankment layers.

Some of the most important goals of soil bed reinforcement include effective use of soil, improvement of soft and low-strength soils, increased strength, resistance, and durability of soil, reduction of soil permeability, reduction of soil moisture, prevention of soil erosion, reduction of pavement layer thickness, rehabilitation of worn-out surfaces with various materials, reduction of dust, savings in material and energy consumption, and acceleration of execution operations.

What materials are used in bed stabilization?

The materials used for bed stabilization include the following:

Lime

One of the materials used in soil stabilization is lime. The most common types of lime include:

Quicklime (CaO)

Hydrated lime (Ca (OH) 2)

Dolomitic quicklime (CaO+MgO)

Dolomitic hydrated lime ((Mg(OH)2 or Ca (OH)2

The stabilizing power of quicklime is greater than that of hydrated lime and is usually applied to beds with fine-grained soils such as clay. For better effect, lime is added to the soil in slurry form; because adding powdered lime to the soil does not have a significant impact on increasing its strength.

Portland cement

Portland cement is another material used for stabilizing soil beds. This material is a more suitable option for sandy and silty soils, and generally for soils with less than two percent organic matter. In soils where the plasticity range is greater than 30, lime is first used to reduce plasticity properties, followed by cement for stabilization. Soil stabilization with cement has a mechanism similar to that of lime stabilization. Before starting the stabilization process, the soil is plowed using a tractor or other equipment to break it down and soften it, separating large rock particles from it.

Bitumen

Bitumen, as a natural organic binder, is obtained from the distillation of oil or the refining of crude oil and is another material used in soil bed stabilization. The mechanism of using bitumen is completely different from that of lime and cement. Bitumen, as a neutral material, has high adhesive properties and binds soil particles together. Coarse-grained and sandy soils require a higher dosage of bitumen for stabilization. This material reacts with individual soil particles, increasing their strength and adhesion.

Geosynthetic products

Various types of these products, including geotextiles, geogrids, and geomembranes, are widely used in soil stabilization. Each of these polymeric materials has its own specific characteristics. Geotextiles are used as permeable fabrics for separation, filtration, reinforcement of strength, and improvement of soil drainage.

Geogrids are used as a synthetic and grid-like material for subgrade and stabilization of roads. Geocomposites are also created from the combination of several synthetic materials and utilize the advantages of the materials used in their composition in the soil stabilization process.

Bed reinforcement

What role do geosynthetics play in bed stabilization?

Geosynthetic products play a very important and vital role in the stabilization of roads, highways, rivers, embankment layers, and railway lines. These products significantly enhance tensile strength and improve soil by acting as separators, filters, and reinforcers in geotechnical engineering. They not only have a reinforcing effect but also have a significant impact on reducing the thickness of the surface layer.

Some of the most important advantages of geosynthetics and their role in stabilizing various beds include:

Faster installation and higher execution speed

More cost-effective compared to other stabilization and reinforcement methods

Resistance to ultraviolet radiation

Resistance to biological factors and environmental impacts

Reinforcement of weak soils

Reduction of the need for backfilling and excavation

Resistance to corrosion and erosion

Increased speed of stabilization project execution

Prevention of cracking and subsidence of asphalt road beds

Increased load-bearing capacity and shear resistance of soil

Significant reduction in the thickness of pavement layers

Assistance in reinforcing muddy and loose beds

Uniform distribution of stresses in the pavement

Reduction of costs related to equipment and labor

Easy transport and installation of geosynthetics

Elimination of the need for bed reinforcement with lime

Stabilization of riverbeds and how it is done

Rivers are one of the most important environmental resources that flow over long distances. The riverbeds are seriously affected by high water velocity, high elevation, steep slopes, and human activities such as farmers' encroachments on the riverbed and destruction of surrounding lands, uncontrolled expansion of agricultural lands, construction of rural roads in the main riverbeds, etc.

Stabilization and sustainability of riverbeds are carried out through methods such as constructing structures along the river, creating protective covers using stone and concrete, building wooden, concrete, or steel piers at the river mouth, and stabilizing the riverbed using geosynthetics such as geotextiles.

The use of geotextiles as the best method to prevent the degradation of riverbeds has various advantages. The very powerful filtration property of this product can prevent the passage of destructive particles and their collision with existing protective structures along the rivers. This capability has a significant impact on reducing the erosion of protective structures along the riverbed.

Some of the most important advantages of geotextiles include reducing soil erosion, improving soil strength, enhancing the quality of the riverbed stabilization project, not causing damage to the environment, resistance to tearing, quick and easy implementation, saving time and costs, etc.

Stabilization of riverbeds

Stabilization of embankment layers

In flood-prone areas, various types of embankments, including natural embankments, artificial embankments, temporary embankments, and permanent embankments, are used to reduce flood risk. The surface of all embankments is higher than the ground level. Natural embankments are made of several layers of soil such as silt and sediment. Artificial embankments are constructed using wood, metal, plastic, soil, and stone. Permanent embankments are also made with bricks, stones, and cement. If a permanent embankment breaks and is damaged, a temporary embankment is used to cope with flooding.

In general, the layers of embankments play a very important role in preventing flooding; therefore, maintaining them and reinforcing their beds is of great importance. To reinforce and stabilize embankment layers, geosynthetics such as geotextiles are used. This synthetic fabric made of polyester or polypropylene helps control erosion of the embankment, drain the soil, and improve its properties, having a significant impact on flood control.

Stabilization of railway lines

One of the most important and vital elements in rail transport systems is the bed of railway lines. This bed plays a very influential role in increasing the safety and stability of railway transport networks. Stabilization of railway beds is one of the most important necessities; because over time, due to the pressures caused by the passage of trains and changing environmental conditions, problems arise in rail transport and railway lines.

By taking actions such as repairing and maintaining the rails, maintaining the ballast as the subgrade under the rails, repairing and maintaining bridges and platforms, using embankments made with stone materials, using reinforced base materials such as resilient soil, cement, and asphalt, and using geosynthetics, the infrastructure of the railway has improved. Geosynthetics such as geomembranes, geotextiles, and geogrids stabilize and reinforce the railway bed by reinforcing the soil, preventing soil sedimentation, controlling water flow, stabilizing cracks and damages, increasing strength and stability, and eliminating the need for backfilling and excavation.

The stages of reinforcing railway lines include:

Condition assessment

Designing and determining the type and method of using geogrids

Preparation

Cleaning and tidying the railway bed

Compacting the railway bed after installing the geogrid

Installing cover and using suitable stabilizers

Inspection and testing of railway lines

Conclusion

In this article from the Farnam Baspar website, we discussed the process of bed stabilization, the importance and role of geosynthetics in it, and explained that materials such as lime, Portland cement, bitumen, and geosynthetic products are used for this process. Among these materials, geosynthetics are more widely used due to their advantages such as quick installation, high execution speed, lower costs compared to other methods, resistance to biological factors, high resistance to corrosion and erosion, easy transport, etc. Additionally, we provided explanations regarding the stabilization of riverbeds, embankment layers, and railway beds. We sincerely thank you for staying with Farnam Baspar until the end.

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