Optimizing Design of Access Roads for Resource Extraction Operations (Chart)

By definition, mining and resource extraction consist of moving material from one place (the extraction point) to another (the market).  Getting the material out of the ground is the hardest part of the process, and also the area where moving technology forward can pay the biggest dividends.  As a result, most effort and discussion focuses on how to add efficiency to the extraction process.But there is also a lot to be gained by examining the technology for accessing sites and transporting material after it is extracted.  Access roads can have a significant impact on construction and operational costs.  These roads are typically unpaved, and must be properly designed for the loads that are imposed by mining operations.  The use of geogrids for the mechanical stabilization of aggregate layers in access roads can significantly improve the performance of these roads while reducing their construction cost.

For those running a mining or other resource extraction project, I have put together a quick chart that I hope will help you have a targeted conversation with a geotechnical professionals who can address your needs.

What you may be experiencing/trying to accomplish

Notes before speaking with your geotechnical engineer

Access to new drilling/mining areas is hampered by poor quality soils Conventional practice would call for thicker and thicker aggregate sections to build a road section with adequate strength to support the design loading.  Geosynthetics can often deliver a better solution.  Geotextiles can provide separation of aggregate from fine-grained subgrade soils, which can extend the life of the road.  Geogrids also offer separation (when used with properly selected aggregates), but they provide much larger benefits by stabilizing the aggregate layer(s) to strengthen the section.  This allows the design to be optimized to the conditions, with a much thinner section delivering the same performance.
Weather is impacting my construction schedule. It can be difficult or impossible to build adequate roads in wet weather, and while you’re idle, the rain is making subgrade conditions worse.  In many cases, using geogrid can allow construction during poor weather, keeping your project moving.
Maintenance costs are going up. Building access roads with geogrid can benefit your operations and maintenance budgets in multiple ways.  Roads built with geogrids last longer, reducing your resurfacing costs.  In addition, they provide a smoother riding surface, which can allow higher vehicle speed limits and improve fuel economy.  And that smoother surface can also lengthen maintenance intervals on equipment due to reduced wear and tear.
Need to reduce construction costs. The ability to optimize the design of access roads using geogrid can often deliver significant savings in construction costs.  A 30 percent reduction in the cost of building access roads is not unreasonable in many cases, based on a reduction in the thickness of the required section to meet design requirements.  Make sure your geotechnical engineer is experienced in the use of geosynthetics and up to date on current geogrid technology – it can make a big difference to your project’s bottom line.

As always, I welcome your comments and feedback.There is a lot riding on access roads, and the roads must be properly designed for the loads that are imposed by your operations.  While they’re not the largest line item in your budget, optimizing their design does offer an opportunity to significantly and positively impact construction and operational costs.  I hope this information helps you initiate a conversation that will make your project more successful.

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Bryan
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Bryan Gee is the Product Manager for Tensar International Corporation, responsible for managing Tensar’s portfolio of products and systems, including those for roadways such as Tensar® TriAx® Geogrid, the GlasGrid® Pavement Reinforcement System and GlasPaveTM Waterproofing Paving Mat, Spectra® System and Dimension® System. Prior to his appointment, Gee worked as Tensar’s Southeast Region Sales Manager. He has 26 years of experience working in engineering and energy fields, including 15 years as a consulting engineer. Gee is a licensed professional engineer and has served as the engineer of record on more than 50 projects. He received a B.S.E. in Civil and Environmental Engineering from Duke University as well as an M.S. in Civil and Environmental Engineering from Duke University. He has published and presented numerous papers on geosynthetics and other engineering topics.