Cellular confinement systems (CCS)—also known as geocells—are widely used in construction for erosion control, soil stabilization on flat ground and steep slopes, channel protection, and structural reinforcement for load support and earth retention. Typical cellular confinement systems are geosynthetics made with ultrasonically welded high-density polyethylene (HDPE) strips or novel polymeric alloy (NPA)—and expanded on-site to form a honeycomb-like structure—and filled with sand, soil, rock, gravel or concrete.
History of cellular confinement
Research and development of cellular confinement systems (CCS) began with the U.S. Army Corps of Engineers in 1975 to devise a method for building tactical roads over soft ground. Engineers found that sand-confinement systems performed better than conventional crushed stone sections and they could provide an expedient construction technique for access roads over soft ground, without being adversely affected by wet weather conditions. The US Army Corps of Engineers in Vicksburg, Mississippi (1981) experimented with a number of confining systems, from plastic pipe mats, to slotted aluminum sheets to prefabricated polymeric systems called sand grids and then, cellular confinement systems. Today cellular confinement systems are typically made from strips 50–200 mm wide, ultrasonically welded at intervals along their width. The CCS is folded and shipped to the job site in a collapsed configuration.
Efforts for civilian commercialization of the cellular confinement system by the Presto Products Company, led to the Geoweb®. This cellular confinement system was made from high density polyethylene (HDPE), relatively strong, lightweight and suitable for geosynthetic extruding manufacturing. The cellular confinement system was used for load support, slope erosion control and channel lining and earth retention applications in the United States and Canada in the early 1980s.
Research
Early research (Bathurst and Jarrett, 1988) found that cellular confinement reinforced gravel bases are "equivalent to about twice the thickness of unreinforced gravel bases" and that geocells performed better than single sheet reinforcement schemes (geotextiles and geogrids) and were more effective in reducing lateral spreading of infill under loading than conventional reinforced bases. However, Richardson (2004) (who was onsite at the US Corps of Engineers CCS Vicksburg facility) laments 25 years later on the "near absence of research papers on geocells in all of the geosynthetic national and international conferences."
A comprehensive review of available research literature by Yuu, et al in 2008 concluded that the use of CCS technology in base reinforcement of paved roads, and railways in particular, was limited, due to the lack of design methods, lack of advanced research in the previous two decades and limited understanding of the reinforcement mechanisms. Since then, hundreds of research papers on geocell systems have been published. Extensive research has been conducted on CCS reinforcement for roadway applications to understand the mechanisms and influencing factors of confinement reinforcement, evaluate its effectiveness in improving roadway performance and develop design methods for roadway applications (Han, et al. 2011).
Hedge (2017,) and Hedge, et al (2020) present comprehensive surveys and reviews of latest geocell studies, field testing, state of the art knowledge and present trends and scope of future research directions, validating increased use of geocells in ground reinforcement and infrastructure projects. Han (2013) summarizes comprehensive research conducted at the University of Kansas, including static and cyclic plate loading tests, full-scale moving wheel tests, and numerical modeling on geocell-reinforced base courses with different infill materials and discusses the main research findings from these studies regarding permanent, elastic, and creep deformations, stiffness, bearing capacity, and stress distribution, and the development of design methods for geocell-reinforced bases. These studies showed that base courses reinforced with Novel Polymeric Alloy (NAP) geocells reduced the vertical stresses at the interface between subgrade and base course, reduced permanent and creep deformations, increased elastic deformation, stiffness, and bearing capacity of base courses. Additional literature reviews can be found in Kief et al (2013) and Marto (2013).