Studies of geocell reinforcement mechanisms, numerical modeling and field trials by researchers included the calibration of existing design methodologies for 3D Neoloy®-based PRS-Neoweb™ geocells.

  • For unstable subgrades, the Giroud and Han (2004) method for design with geosynthetics was modified for PRS-Neoweb-reinforced bases (Han, 2011).
  • For roads with a stable base and subgrade, the design method for incorporating PRS-Neoweb uses the elastic behavior of pavement structures and follows the Mechanistic-Empirical design procedure.

The modified methods utilize the Modulus Improvement Factor (MIF) in the calculations to define the increased modulus of a PRS-Neoweb reinforced base layer.

Modification of Design Methodology for Unpaved Roads

The Giroud and Han (2004) design methodology for geosynthetic (geotextile and geogrid) reinforcement of unpaved roads was modified for reinforcement with PRS-Neoweb (high-strength) geocells. The modifications include changing geogrid dependent parameters (such as aperture modulus) to geocell dependent parameters. These were, calibrated by the laboratory cyclic plate loading tests and full-scale moving wheel tests on PRS-Neoweb geocell-reinforced granular bases over weak subgrade.

Layered Elastic Model for Paved Roads

Road design with PRS-Neoweb geocells is based on the mechanistic-empirical design method for flexible pavements using the layer elastic model. A mechanistic model of each pavement layer is created including its thickness, elastic modulus and Poisson’s ratio. Then the typical load configuration is applied using one of the commercially available layered-elastic analysis programs for pavements. The Layered Elastic Model utilizes the following parameters:

  • CBR
  • ESAL’s
  • PRS-Neoweb MIF
  • Validation using fatigue and rutting criteria

The design methodology is based on replacing an unreinforced pavement design with a design based on PRS-Neoweb reinforcement. The improved performance of the pavement structure due to the PRS-Neoweb reinforcement (typically the base layer) is expressed by the Modulus Improvement Factor.

The basic advantages of a mechanistic-empirical pavement design method over a purely empirical one are:

Benefits

  • It can be used for both existing pavement rehabilitation and new pavement construction
  • It accommodates changing load types
  • It can better characterize materials allowing for:
    • Better utilization of available materials
    • Accommodation of new materials
    • An improved definition of existing layer properties
  • It uses material properties that relate better to actual pavement performance
  • It provides more reliable performance predictions
  • It better defines the role of construction
  • It accommodates environmental and aging effects on materials