In road infrastructure, platform, and embankment projects, the presence of soft soils poses one of the main geotechnical challenges during construction. Traditionally, when a subgrade has low bearing capacity or is saturated, the most common solution has been to excavate and replace the material.

However, this alternative involves high construction costs, longer construction times, the need to dispose of excavated material, and greater environmental impacts. Furthermore, in many projects, completely replacing the soil is neither technically nor economically feasible, especially when there are high water tables or large thicknesses of compressible material.

Currently, there are improvement methods that make it possible to stabilize soft soils without having to completely replace the material, notably the use of reinforcing geosynthetics, particularly high-modulus woven geotextiles made of high-tenacity polyester (PET).

Why are soft soils a problem?

Soft soils are characterized by the following:

  • Low support capacity
  • High compressibility
  • High susceptibility to deformation

Under construction or traffic loads, these conditions can cause excessive deformation, rutting, and failure of the work platform.

The problem worsens in the presence of water or high water tables, since the increase in pore pressure reduces the effective stress in the soil and further decreases its shear strength.

How do high-modulus geotextiles work?

The woven geotextiles High-modulus geogrids function as reinforcing elements installed between the subbase and the granular layer, improving the system's mechanical and hydraulic performance.

In particular, geotextiles made from high-tenacity polyester (PET) G5 multifilament offer high tensile strength, rapid response to deformation, and low creep, allowing the subgrade to be stabilized from the earliest stages of construction.

In addition, its weft-insertion woven structure maintains stable hydraulic properties even under confinement, promoting moisture control and the dissipation of pore pressures.

Soft Soil Stabilization Mechanisms

1. Improving Support Capacity

The geotextile alters the stress distribution within the soil-granular system, confining the failure surface within the granular layer, which has greater shear strength than the soft subgrade.

As a result, the system's load-bearing capacity increases, and the deformations transmitted to the foundation soil are reduced.

2. Tensioned membrane effect

When the subgrade deforms under load, the geotextile develops tensile stresses that generate an upward vertical component capable of relieving part of the loads acting on the soft soil.

This mechanism improves stress distribution and reduces excessive deformation during construction and service.

3. Separation of materials

When the geotextile is installed between the subgrade and the granular material, it acts as a separation layer, preventing contamination of the granular layer due to the migration of fine particles.

This preserves the mechanical and hydraulic properties of each material, improving the structure's performance and stability.

Fortex Geotextil de alto módulo

Figure 1. Installation of high-modulus PET geotextile for stabilizing soft soils and improving the bearing capacity of the subgrade.

Why use high-modulus PET geotextiles?

The performance of a geotextile reinforcement depends directly on its stress–strain behavior and long-term stability.

The Geotextiles made from high-tenacity polyester (PET) offer:

  • High modulus of elongation
  • High tensile strength
  • Low plastic deformation (low creep)
  • Excellent performance during lockdown
  • Long-term hydraulic stability
  • High chemical and mechanical durability

These properties ensure that the reinforcement and separation functions are maintained even under critical load and saturation conditions.

Benefits of Stabilization with Geotextiles

The use of high-modulus geotextiles in soft soils allows for:

  • Improve the bearing capacity of the subgrade
  • Reduce warping and indentations
  • Create stable work platforms
  • Reducing contamination of granular materials
  • Improve the hydraulic conditions of the system
  • Optimize construction timelines
  • Reduce excavation and cost overruns associated with material replacement

In addition, they represent a technically efficient and more environmentally sustainable solution compared to traditional excavation and replacement methods.

Conclusion

The stabilization of soft soils does not necessarily require the complete replacement of the subgrade material. Currently, geosynthetic reinforcements—especially high-modulus woven geotextiles made from high-tenacity polyester (PET)—can significantly improve the mechanical and hydraulic performance of the system.

Thanks to mechanisms such as improved load-bearing capacity, the tensioned membrane effect, and separation between materials, these geotextiles increase the stability of the subgrade and reduce deformation even under saturated conditions.

When combined with subdrainage systems, they provide an efficient, durable, and technically reliable solution for stabilizing soft soils in modern civil engineering projects.