Written by: Bryan Wedin, P.E., Chief Design Engineer
Road construction is booming, and this trend is expected to remain strong due to high demand and the Infrastructure Investment and Jobs Act (IIJA), which includes investments across many sectors, including public infrastructure.
Along with this boom, the road construction industry has been dealing with inflation-related cost increases and limited availability of construction materials. The industry has been impacted by supply-chain interruptions and shortages for many roadway materials including lime, cement, and even aggregate. These materials are typically used for roadway base construction, which means road construction projects that use these materials may be subject to delays. Due to these shortages and delays, on-site material or sand-filled GEOWEB® geocells can provide a cost-effective, readily available substitute for base materials–especially where native subgrade conditions consist of weak or soft soils.
GEOWEB® Geocells for Roadway Base Stabilization
The GEOWEB geocells have been used for load support and foundation applications worldwide for more than 40 years. Developed in collaboration with the U.S. Army Corps of Engineers (USACE) in the late 1970s, Presto co-invented the technology now known as geocells or a cellular confinement system (CCS). The early applications of geocells consisted primarily of stabilized, expedient sand roads for military vehicles. In the early 1990s, the U.S. Army deployed over 6 million square feet of the geocellular system to stabilize the shifting desert sands and provide mobility for troops and military vehicles. At the time, the system was dubbed Sandgrid due to its readily available sand infill.
Both the USACE and Desert Storm forces found a solution for building fast access roads across sand landscapes. By utilizing the principle of soil confinement to enhance soil strength, the GEOWEB System turns sand into a load-supporting composite structure that can support heavy-loaded vehicles under repeated load cycles. Since then, the GEOWEB System has also been adopted by State and Federal roadway authorities for domestic road construction across the United States.
Presto Geosystems has endeavored to improve and innovate geocell technology, creating the modern-day GEOWEB® Soil Stabilization System. The GEOWEB geocells are made of 100% high-density virgin polyethylene (HDPE) and do not contain any recycled material, fillers, or exotic polymers—all of which can negatively affect performance. Complete with a full line of accessories for ease of installation and long-term performance, the GEOWEB Soil Stabilization System is the most advanced geocell technology in the industry.
Sand-Filled GEOWEB Geocells for Soil Stabilization
Geocells are three-dimensional honeycomb-like structures made of ultrasonically welded strips of HDPE that confine infill material over a specified cell depth and diameter. Through confinement, the GEOWEB system distributes loads laterally and controls shearing, as well as lateral and vertical infill movement.
Compared to planar geosynthetic products such as geogrids—which commonly rely on expensive imported high-quality aggregate—geocells are highly versatile and can be filled with a variety of commonly available and economical infill materials, including sand.
In many cases, geocells allow for the beneficial reuse of on-site materials, eliminating the need to purchase expensive aggregate or imported structural fill. These advantages not only offer the potential for savings in overall construction costs but also contribute to a significant reduction in carbon emissions due to less aggregate/fill processing, transportation, and handling.
The illustration below provides a comparison of four structurally equivalent aggregate sections over a subgrade with a CBR of 0.5%.
As shown, the unreinforced aggregate option would require more than 36 inches of aggregate to achieve minimal stability, and the planar geosynthetic option (geogrid + geotextile) would require 26 inches of aggregate. In contrast, the GEOWEB geocells reduce the total section thickness to only 15 inches, and where suitable on-site material is available, it is possible to limit imported aggregate to just the wearing course.
The GEOWEB geocells dramatically increase the shear resistance of the infill, which allows the use of lower-quality fill to carry concentrated loads that would otherwise require crushed aggregate to prevent localized, near-surface shear failure. The cellular structure also distributes concentrated loads to surrounding cells, thus reducing the stress on the subgrade directly beneath the load and the required total thickness of the structure.
Let Our Engineers Run Design Calculations on Your Next Project. See the Cost Savings For Yourself!
Presto Geosystems’ engineering team works closely with you to provide free project evaluations and on-site installation support. The team at Presto Geosystems is here to provide engineering support from the preliminary stages through construction. Use our free online tools to keep your projects moving forward. The project evaluation will deliver a technically sound, cost-effective solution based on four decades of accredited research and project experience. Please contact our knowledgeable staff and network of qualified distributors to discuss your project needs today.
Sustainable vegetation in channels can be achieved with the GEOWEB TRM system. Applications that benefit include roadside ditches, stormwater channels, shoreline embankments, dams, spillways, and pond overflow systems. The GEOWEB/TRM system is a more sustainable—and environmentally friendly solution than rip rap for these common applications.
We have a great team here at Presto Geosystems, so we thought it would be fun to share a bit more about each member through a new blog series. For our inaugural Meet the Presto Geosystems Team blog post, we are thrilled to introduce José Pablo George—Presto Geosystem’s International Business Manager (BDM).
In the United Kingdom, Network Rail encountered extremely soft soils with low shear strengths during track modifications to the North West Electrification Programme. Due to soft subgrade conditions, conventional track design methods resulted in cross-sections as thick as 1 meter. Poor soil conditions along the track route required a soil stabilization solution to improve undertrack stiffness and provide a more cost-effective solution. The Network Rail Track Bed Investigation (TBI) team elected to evaluate an alternative solution using geocells to reduce required cross-section thicknesses. The GEOWEB Soil Stabilization System has been used under track in the United Kingdom since the 1980s; however, very limited information was collected at that time to document the resulting improvement in performance. Therefore, the TBI team used in-house numerical modelling to validate the design approach, and results indicated that a geocell-stabilized track performed as well as the conventional full-thickness cross-section. Based on this information, combined with the demonstrated long term stabilization of the above-referenced early installations, the TBI team elected to use the alternate track bed design incorporating GEOWEB Geocells. The North West Electrification Programme subsequently approved the use of geocells on a number of sections with the goal of reducing construction depth, in turn, reducing costs associated with track enhancement and long term maintenance.
After installing the GEOWEB Soil Stabilization System on the North West Electrification Programme in 2017, track quality improved significantly. The reduction in the required track bed construction (40% reduction in granular fill material), reduced the cost of track enhancement by approximately 22% (Wehbi, et al., 2018). Network Rail also realized the benefit in the ability to use granular fill or course sand as ideal infill materials. Network Rail’s experience using geocells has shown substantial construction cost savings and benefits to the structural integrity of the track bed (Wehbi, et al., 2018). Network Rail has also monitored Willesden North on the London North East and Newham Bog on the London North West in addition to the Northern West Electrification Programme, which show similar results and benefits.
The use of the GEOWEB 3D slope cover system best addresses critical details when designing or remediating geomembrane covers. With the aging infrastructure of dams, impoundments, and landfills, design engineers are looking for innovative and cost-effective solutions to build and repair new and existing facilities. The adaptability of the 3D system provides geomembrane protection while contributing to an easier and faster installation process.
Measure the performance of the GEOWEB (GW) material combined with a turf reinforcement mat (TRM) (integrated system) with topsoil infill and vegetation under varying shear stresses and flow rates to quantify both hydraulic forces and
The Research Facility
Exposed to the extreme flows, and despite ordinary topsoil infill and typical TRM staple patterns, the system showed no measurable soil loss. It was observed that the vegetation had decreased stem and blade count during the total testing timeframe, however at a decreasing rate of loss for each incremental test.
The results of this integrated system testing can be applied to highway drainage ditches, spillways, dam, and pond overflow systems and other vegetated channels exposed to high shear forces and intermittent, longer-duration velocities. This system replaces rip rap with a less expensive, low maintenance, aesthetically pleasing green solution.
With geocells, it is not uncommon to see an overall reduction in the required thickness of the base layer or leveling course in a load support application by 50% or more, along with an overall improvement in allowable bearing capacity. This applies to foundations as well as permanent or temporary site features, such as access roads or construction platforms.
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