Kief, O., and Rajagopal, K. (2008) “3D Cellular Confinement System Contribution to Structural Pavement Reinforcement.” Geosynthetics India ’08, Hyderabad, India
The sustainable advantages of 3D Neoloy Geocells in an economy like India are described, field test results are reviewed, a reinforcement factor of 5x is back-calculated and the reinforcement mechanism described.
This study, presented at Geosynthetics India, demonstrates that reinforcement with NPA (Neoloy® – Novel Polymeric Alloy) Geocells can significantly reduce road repair, rehabilitation, maintenance and reliance on raw materials. In situ testing was conducted by the Clausthal University of Technology in Germany on two rehabilitated sections of pavement, one reinforced by Neoloy. The results were further validated by back calculation. They found that Neoloy reduces vertical stress by 50%, increases finite beaming capacity by a factor of 2.5x and improves the structural soundness of the pavement by a factor of 5x. Consequently, Neoloy can reduce pavement thickness, while extending its life cycle.
Challenge – Sustainable, affordable pavement construction
A study by Rajagopal, Krishnaswamy and Madhavi Latha in 1999 found that 3D cellular solutions similar to Neoloy can utilize fine grains like sand, unlike 2D planar methods. Nonetheless, in India where innovative techniques are acutely needed to minimize the use of raw materials in road construction, a lack of standardized design and testing methods has limited the use of geocells.
Validation – In situ testing
A field test was conducted by the Institute of Geotechnical Engineering and Mine Surveying at the Clausthal University of Technology in Germany.
- Phase One compared the vertical stress on two sections of Road K27 in Lower Saxony in need of rehabilitation – A Neoloy reinforced sample and a control sample. 6 dynamic earth pressure cells were installed to measure underground stress, which was applied at 3 identical points on each sample, by incremental loading of a 300mm diameter plate.
- Phase Two was a back calculation of the structural value of the Neoloy layer, with the aid of Elastic Stress Analysis.
- Phase Three was conducted following the rehabilitation of the gravel base course and the new asphalt pavement. A vehicle crossing test was carried out with a heavy truck crossing at different speeds. Stresses were measured by earth pressure cells.
Results – Reduced stress, increased bearing capacity
The tests demonstrated that Neoloy distributes loads over a wide area, significantly increasing strength and stiffness. In particular, the following results were recorded:
- Neoloy reduced vertical stress by 50%, as the geocells create a semi-rigid mattress, distributing stress over a wide area
- Neoloy increased finite bearing capacity of the subgrade layer by a factor of 2.5x
- During the vehicle crossing test, stresses were 23-28% lower in the Neoloy reinforced section
- Neoloy improved the pavement’s structural soundness by a factor of 5x
Benefits – Longer pavement life, lower costs, fewer raw materials
The study validated that that Neoloy is an excellent solution for the rehabilitation of distressed roads, bringing the following benefits:
- Longer pavement life, reducing maintenance costs
- Reduced labour costs, due to reduced need for excavation, hauling and infill
- Reduced thickness of structural support elements, reducing construction costs
- Fewer raw materials required