Cellular Confinement - Recent Developments in Cellular Confinement Technology

Recent Developments in Cellular Confinement Technology

Despite the effectiveness of the geocell technology, particularly in slope and channel applications, its use in base reinforcement of paved roads and railways was limited due to the lack of design methods, lack of advanced research in the last two decades and limited understanding of the reinforcement mechanisms (Yuu, et al. 2008).) Recent research in the last few years on geocell reinforcement for roadway applications - reflected by some 40 published papers - has been conducted at the University of Kansas as well as at other leading research institutes around the world, to understand the mechanisms and influencing factors of geocell reinforcement, evaluate its effectiveness in improving roadway performance, and develop design methods for roadway applications (Han, et al. 2011).

Research was conducted on HPDE geocells as well as geocells manufactured from a novel polymeric alloy (NPA), called Neoloy®, developed by PRS. NPA is a composite polymeric alloy based on nano-fibers (polyester and nylon) in a polyolefin matrix. The NPA combines the desired properties of polyethylene and polyester, thus enabling a more effective use of geocells in new critical applications, such as reinforcement for earth retention, load support in pavements and railroads and more (Leshchinsky, et al., 2009). While HDPE is the commonly used material for geocells, leading researchers have questioned its suitability for long term applications (Leshchinsky, et al., 2009). This concern is backed up by “facts on the ground” as HDPE geocells are rarely used in critical applications, such as in the base layer of major highways and railways, subject to long-term heavy static and dynamic loading.

Laboratory plate loading tests on geocells showed that the performance of geocell-reinforced bases depends on the elastic modulus of the geocell. The geocell with a higher elastic modulus had a higher bearing capacity and stiffness of the reinforced base. Geocells made from NPA were found significantly better in ultimate bearing capacity, stiffness, and reinforcement relative to geocells made from HDPE (Pokharel, et al., 2009). NPA geocells showed better creep resistance and better retention of stiffness and creep resistance particularly at elevated temperatures, verified by plate load testing, numerical modeling and full scale trafficking tests (Pokharel, et al. 2011). Research demonstrated that NPA geocells have a lower thermal expansion coefficient and creep reduction factor, and higher tensile stiffness and strength than HDPE geocells.(Thakur, et al., 2010); and NPA increased the bearing capacity and reduced settlement of compacted sand base courses significantly more than geocells fabricated from HDPE (Pokharel, 2011, et al.).

Laboratory studies, full-scale moving wheel tests, and field demonstrations (cosponsored by US DOT Department of Transportation as well as state DOTs) have demonstrated clear benefits of NPA (novel polymeric alloy) geocell reinforcement in terms of increased stiffness and bearing capacity, wider stress distribution, reduced permanent deformation, and prolonged roadway life, while the design methods developed and calibrated in this research can help engineers design future roadway applications using geocells (Han, et al. 2011). This close cooperation and iterative research and development process between private industry and academia was cited by the editor of Geosynthetics magazine, as: “an example of how product development for the geosynthetics industry can be done effectively… and can further advance the geosynthetics industry into the 21st century with much success.”