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Using Geosynthetics in Roadway Design – Smart. Choice.

Using Geosynthetics in Roadway Design – Smart. Choice.

The economic conditions we are currently experiencing has created a situation that provides opportunities for many industries and institutions. Institutions from Ministries of Highways and local municipalities, to private owners have created mandates to explore new systems to streamline their businesses and this extends to commerce within the construction marketplace.

Over the past 30 years, civil engineering projects have utilized geosynthetics to optimize the design and/or increase the longevity of particular systems. This includes roadway design by enhancing subgrade stabilization and more recently optimizing the trafficked structure, be it a paved or unpaved roadway.

It is common knowledge that road structures fail prematurely due to many unfavourable factors including subgrade conditions, environmental factors, traffic patterns, water infiltration and inadequate drainage, lateral displacement and weakening of base course aggregate. The unfavorable effects of these aspects can become extremely time consuming and costly to fix irrespective of regular maintenance; therefore, significant strategies are required for long-term maintenance or rehabilitation. However, such remedies are often temporary or unsuccessful because they only treat the symptom, rather than the cause of the problem.

To safeguard against these unfavourable factors, technological systems have been developed with the use of geosynthetics. However, they should be specified during the initial design stage for them to provide optimum performance during and post construction. Within roadway design, geosynthetics are commonly used for separation, filtration, drainage, stabilization, reinforcement and crack mitigation. Invariably their use in these applications improve the performance of roadway structures by extending their longevity.

In addition to improving structural performance, geosynthetics offer many other advantages including:

  • Economic: the structural strength provided by geosynthetics allows for the installation of thinner aggregate base course sections, reduced asphalt thickness, and improved performance, thus costing less up front as well as over the long-term lifespan of the road. There is also cost-savings realized in the installation labour and transportation of aggregate.

  • Social, political and environmental benefits: by reducing the reliance on natural and non-renewable resources, we reduce the damaging effects of harmful greenhouse gas emissions associated with the mining, processing and transportation of aggregate materials. Geosynthetics offer innovative solutions to the construction industry for building greener roads, akin to LEED certification, thus lowering the environmental impact.

  • Safety: using geosynthetics minimizes the aggregate mining and transportation requirements, decreasing the number of truck loads travelling long distances across our provinces to site. Installation is also simpler and requires less equipment than conventional construction methods to build the trafficked structure.

  • Time: expedited construction timelines occur with geosynthetics usage because they require less excavation and compaction for subgrade stabilization, are lightweight and easy to install, are usually in stock and ship quickly, and can be installed during short construction seasons or during short bouts of good weather conditions.

  • Engineered quality and performance advantage:  geosynthetics are engineered in controlled environments and extensively tested to ensure performance and product quality. Adversely, soil and aggregate generally vary significantly across a construction site or region and are subject to deviations in weather, handling and compaction.

Ultimately, geosynthetics offer unique value propositions that knowledgeable suppliers, in partnership with owners and their consultants, can convey through superior technical design support that speaks to an optimum economic solution. In addition to offering technical design support, Nilex Inc. has a proprietary and validated Innovation Calculator to calculate the cost savings, total CO2 emissions savings, as well as number of truck hauls saved by implementing their engineered geosynthetic products in any road construction design, versus conventional road construction methods.

Knowing what product to implement for such a unique value proposition is fundamental to the roadway design process. Geotextiles, whether woven or nonwoven, should primarily be utilized to separate the subgrade from the aggregate, whereas geogrids (Triaxial or Biaxial) are used to reinforce the aggregate and improve confinement, thus improving structure longevity. Together; these geosynthetic materials spread stress from the wheel loads to the weak subgrade by maximizing the load distribution. Specifically, if geogrids are used they restrain lateral movement of the aggregate, in turn improving the road’s stiffness and performance.

Interlayer asphalt geosynthetic products can reduce maintenance costs and extend the roadway lifespan by providing reinforcement between the levelling and surface course of the pavement to resist the migration of cracks as well as preventing surface water infiltration by forming a moisture barrier and stress/strain absorption layer, improving the pavement’s resistance to reflective and fatigue cracking.

The use of geosynthetics reaches into other areas of engineered systems, including Mechanically Stabilized Earth (MSE) walls and slopes, erosion and sediment control, water management and containment applications. Contact Nilex Inc. to find out about the advantages of geosynthetics in these applications, as well as roadway design.

Karan (KJ) Jalota is a professional engineer who has specialized in geotechnical engineering for the past 15 years. He is experienced in evaluating the effects of soil-structure interaction for both public and private owners.


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