Pavement geotextile

Narejo DB. Opening size recommendations for separation geotextiles nsed in pavements. Geotextiles and Geomembranes 2003 21 257-64. 

Separation. In this function, the geotextile serves to separate two dissimilar materials (Fig. 3), eg, two different soils, landfill material and the native soil, stone material and subgrade sod, old and new pavement, foundation sods and various types of wads, or one of many other similar situations. In some instances, it is difficult to distinguish between the separation and stabilization functions because in both situations the geotextde is serving as a separator. However, in stabilization some additional phenomena occur. 

Moisture Barrier. When impregnated with an asphaltic emulsion, geotextiles become impermeable and can then be used as moisture barriers. The primary appHcation for this type of geotextile is in pavement rehabiHtation (Fig. 8). 

Although with the use of geotextiles, and even more with the use of geogrids, a reduction in the thickness of the unbound layers is possible, there is no pavement design methodology that caters for that. Determination of the resulting thickness reduction with the use of geotextiles and related materials is conducted, when needed, separately. 

The use of geotextiles in conjunction with the bitumen layer sprayed also functions as an interlayer water barrier to the ingress of surface water and thus prevents or delays the deterioration of the pavement. 

CEN EN 15381.2008. Geotextiles and geotextile-related products - Characteristics required for use in pavements and asphalt overlays. Brussels CEN. 

The improvement in the performance of a pavement attributable to the inclusion of geotextiles comes mainly from their separation and reinforcing functions. This can be assessed in terms of either an improved system performance (e.g. reduction in deformation or increase in traffic passes before failure) or reduced aggregate thickness requirements (where reductions of the order 25-50% are feasible for low-strength subgrade conditions with suitable geotextiles). 

Ameri, M., Shahi, J., Khani, H. S. (2012). A mathematical model for determination of stmctural value of geotextile in pavements. International Journal of Civil Engineering, 11(1), 61-66. 

Garber, S., Rasmussen, R. (2010). Nonwoven geotextile interlayers in concrete pavements. Transportation Research Record Journal of the Transportation Board No. 2152 (pp. 11-15). 

Levy, T. (1990). The use of polypropylene nonwoven geotextiles impregnated with bituminous binder in road pavement. Journal of Coated Fabrics, 20, 82—87. 

The significant requirements for a suitable geotextile dynamic filter in road pavements are permeability, pore size, thickness, structure incompressibility, tensile strength, and resistance to deformations. PP meets these requirements, so 65-70% of geotextiles are made of it. 

Geotextile fabrics can be manufactured with a suitable stmcture to enable liquid or gas to flow within the plane of the fabric. The fluid s in-plane transmission property of a geotextile is also known as its transmissivity. Examples are beneath railroad ballast, to dissipate seepage water from exposed soil or rock surfaces, and drainage of pavement layers. 

Compacted soils and aggregates generally have good compressive modulus but poor tensile modulus and hence can be readily separated when subjected to high tensile loads. Geotextiles with fibres of suitable tensile moduli can effectively be used as reinforcing tension elements when embedded in compacted soils and aggregates. Some major uses are over soft soil unpaved roads, mnways, railroads and landfills, to stabilize a temporary bunds slope, as closure systems over unstable landfills, ash ponds and to reinforce asphalt pavement layers. 

The Munshirhat—R pur Road is a rural road in Howrah, India, which was to be widened to improve traffic. In 2000, jute geotextile was laid on the extended portion of the road. The subgrade CBR was stroigfliened by the use of jute geotextiles and achieved a CBR value of 6% from 3.5% with a noticeable reduction in liquid and plastic limits. No road distress is visible and the travel surface of the pavement is absolutely smooth. 

---