Field evaluation of geocell use in flexible pavements

Wheel rutting in excess of 100 mm occurred within 7 days after reconstruction of a section of Route 30 in Delaware County, Pennsylvania, an urban roadway with high average daily traffic. The road was reconstructed on a weak subgrade, and soil tests produced California bearing ratio values between 1.5 and 6.5 percent. A geocell confinement system was used to stabilize the subgrade and solve this problem. The geocell used was constructed of high-density polyethylene. Each geocell panel was fabricated using 60 strips 3.3 m long and 100 mm thick. The panels were 2.4 m x 6.1 m when expanded and created a honeycomb-patterned cellular confinement system. The geocell system was used in combination with other geosynthetics (geogrid or geotextiles, or both). The findings indicated that the geocell system used in this project performed very favorably: The roadway has not shown any pavement distress (alligator cracking, rutting, etc.) during the 3-year evaluation period. To date, falling weight deflectometer data, initially collected after construction, have since been collected annually for 2 years. Analysis suggests that the geocell, in combination with a geosynthetic layer, provides a significant improvement to the pavement structure capacity when built over a weak subgrade. The resilient modulus of the 150-mm-thick aggregate layer was improved almost twofold. There is a good possibility that this increase was caused by the aggregate confinement resulting from the geocell and the separation provided by another geosynthetic layer.