PAVED AND UNPAVED ROADS

Whenever a paved or unpaved road needs to be built on soft or saturated soil, settlement may take place during or after construction, with serious consequences for the life span of the road.
The base layer, made-up from granular material, can sink into the foundation soil, and horizontal and vertical movement capable of forming ruts can occur at the base. To avoid these phenomena, it’s necessary to place one or more layers of reinforcing geogrids having the ability to confine the aggregate and distribute the load. Geosynthetics allow for the reduction in the thickness of the base layer and they increase the service life of the structure whilst utilizing lower grade fill material. The use of a TENAX LBO SAMP geogrid minimizes the horizontal deformation of the aggregate base layer, limiting its deterioration and conserving its thickness. TENAX LBO SAMP geogrids are a mesh structure having apertures in which granular material is confined by interlocking.

Paved road: Road base thickness: 30 mm Subgrade CBR: 1.0	Paved road: 5.000.000 Passages
Altshausen (Germany) Subsoil stabilization with nonwovens and integral geogrid TENAX LBO SAMP
Base reinforcement of the road embankment of the Rome-Fiumicino Airport High Way	The reduced likelihood of deformation in the base layer limits the formation of “fractures” in elements beneath the base itself. In fine-grained sand or clay like soils, it’s advisable to use a finer mesh multi-layer geogrid such as the TENAX MS series. When the grain size characteristics of the aggregate base soil are not suitable to act as a filter of the subgrade, it’s necessary to prevent the possibility that the former, as a consequence of the compression and relaxation cycles to which it is subjected, can migrate into the upper layer. Under these circumstances, the use of a TENAX GT geocomposite, made from a reinforcing TENAX LBO SAMP geogrid laminated to a light nonwoven geotextile and functioning as a separating membrane, has proved effective.

The interlocking between the geogrid and the soil particles is not prevented thanks to the geotextile’s high local deformability in the openings between the geogrid meshes. If the road is to be constructed in an area with a high water table, placing a filtering/draining TENAX TNT geocomposite at the base of the structure provides an excellent means for draining the structure itself, preventing backfill from sinking and contributing to the distribution of load.

Schematic example



The base of a road on soft subgrade will quickly deform, with rutting at the surface and difficulty of movements for the vehicles. Closely spaced layers of TENAX geogrids considerably stiffen the road base, while TENAX geocomposites maintain the separation between the fill and the subgrade while providing positive drainage. TENAX geosynthetics provide the drainage, separation and reinforcement required to stabilize the base of roads on soft subgrade.

Legend: 1. Soft soil 2. Granular fill 3. Soil cracking 4. Deformed profile	5. Asphalt or concrete pavement 6. TENAX bi-oriented geogrids 7. TENAX TENDRAIN, TENAX TN, TENAX GT geocomposites
		The use of TENAX bi-oriented geogrids allows to: 1) Reduce the progressive failure of the flexible paved roads: The road service life can be increased up to a factor of 10 without changing the properties of the road components 2) Reduce the thickness of the aggregate base layer without loosing in performances and structural capacity.

RAILROADS AND AIRPORT RUNWAYS

The rapid passage of trains, the take off and landing of airplanes in very brief intervals of time, apply dynamic loads to the soil resulting in very intense compression and decompression cycles.
The foundation, being thus subjected to fatigue stresses, can undergo fracturing up to the point of collapse. Under these conditions, both very thick layers of aggregate, and frequent and expensive maintenance are required (although these maintenance costs are high, by far the most important cost factor is the reduction in revenue caused by the disruption of services).
One or more bioriented TENAX LBO SAMP or TENAX MS geogrid layers, laid on the base of the railway ballast or airport runway, constrain the aggregate by laterally confining it, and creating the necessary tensile forces. The aggregate’s thickness can therefore be reduced with considerable savings.

Seul (S. Korea): International Airport runway reinforcement with TENAX LBO SAMP geogrids.

TENAX LBO SAMP geogrids are used to confine railways ballast; wide aperture geogrids are available for this purpose. TENAX geogrids’ considerable rigidity and composition guarantees, in fact, a long-term effect as far as both mechanical and chemical resistance are concerned, even when used under very aggressive conditions. When it is necessary to prevent the pumping of fine particles, a TENAX GT geocomposite can be installed at the aggregate interface, or if the goal is to facilitate drainage, a TENAX TNT geocomposite can be used instead.

Yverdon-les-Bains (Switzerland) Installation of TENAX MS 500 over soil with very weak bearing capacity for installation of runway for light aircraft

Slovenia Stabilization of a railway track on severely yielding soils by the use of TENAX geocomposites and geogrids.

Schematic example

The dynamic load provided by the passage of trains quickly produces deformation of the ballast and of the base layers on soft subgrade.

An airport runway on soft soil may undergo premature deformation due to lack of lateral confinement of the aggregate and to pumping of fines from the subgrade.

TENAX geosynthetics allow to obtain a stable railway and firm airport runways

Legend: 1. Soft soil 2. Granular soil 3. Ballast 4. Deformed profile 5. TENAX TENDRAIN or TENAX TNT geocomposites 6. TENAX bi-oriented geogrids 7. Asphalt or concrete pavement 8. TENAX geogrid for asphalt reinforcement