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.
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