Functions and Applications of Geotextiles and Other Geosynthetics in Roads

Geosynthetics have been used since the 1970s to improve the performance of unpaved roads on soft ground. Since the 1980s, geosynthetics (mostly geotextiles and geogrids) have been used to minimize reflective cracks in asphalt overlays and improve the performance of basic aggregate layers.

(1)Different geosynthesis functions clearly correspond to different geosynthesis attributes

(2)Geosynthetics applications correspond to geosynthetics. Each geosynthesis application may involve a single geosynthesis function or a combination of such functions implemented through mechanical or hydraulic mechanisms, thereby ultimately enhancing road performance.

The various functions that geosynthetics can achieve include:
Separation – Geosynthetic materials are placed between two different materials to maintain the integrity and functionality of the two materials. It may also involve providing long-term stress relief. Key design attributes that perform this function include those used to characterize the viability of geosynthetics during installation.
 

Filtration – Geosynthetics (most of them are geotextiles) allow liquid to flow through its plane while retaining fine particles on its upstream side. The key design attributes to achieve this function include geosynthetic permittivity and geosynthetics pore size distribution measurements.
 

Strengthening – Geosynthetics produce tensile forces, designed to maintain or improve the stability of geosynthetics in the soil. The key design characteristic for this function is the tensile strength of geosynthetics.

Stiffening – Geosynthetics produce tensile forces, designed to control deformation in soil-geosynthetics composites. The key design attributes to achieve this function include those used to quantify the increased stiffness due to soil-soil geosynthesis.
 

Drainage – Geosynthetics allow liquid to flow in its structural plane. The key design attribute to quantify this function is the transmittance of geosynthetics.

Protection-Geosynthetics provide cushioning above or below other materials (such as geomembrane) to minimize damage during placement of the covering material.

Reflective cracks are usually formed in a new flexible pavement covering just above the existing cracks in the old paved road.

Geosynthetics can play a role in asphalt overlays:
By generating tension near the crack tip, the strain in the asphalt material is reduced to prevent triggering new cracks. Using polymer meshes, steel meshes or glass meshes has already achieved this reinforcement.

By providing a layer that allows horizontal displacement, potentially large movements can occur without cracks without failure. This mechanism is called a stress-relieving interlayer, usually involving asphalt-impregnated nonwoven geotextiles, and can be characterized as controlled degumming.

By providing a hydraulic barrier function, even after cracks in the road surface reappear, the underlying road surface layer can be made waterproof. The mechanism also involves the use of asphalt-impregnated nonwoven geotextiles.

Pollution may occur due to the following reasons:
(1) After the local bearing capacity fails under the stress caused by the wheel, the aggrgaete penetrates into the weak subgrade;
(2) Fine-grained soil penetrates into the aggregate due to pumping or weakening of the roadbed. Pore ​​water pressure is too large. Subgrade pollution leads to insufficient structural support, which usually leads to premature destruction of the roadway. Geosynthetics placed between the aggregate and the roadbed can effectively isolate the roadbed and the base aggregate by preventing mixing.

Even a small amount of fine powder contaminated the particle layer may have a negative impact on its structural response, including reduced shear strength, reduced hydraulic conductivity and increased frost sensitivity. Eventually, a mixture containing basic aggregates contaminated with fine-grained soil will basically behave as fine-grained soil itself. Therefore, contamination effectively results in a reduced base layer thickness and ultimately a reduced service life.

Geosynthetics separators are relatively inexpensive to use and can save a lot of costs over the design life of the roadway. In different types of geosynthetics, geotextiles are often used to achieve the separation function.