The Use of Geocells in Road Constructions Over Soft Soil: Vertical Stress and Falling Weight Deflectometer Measurements
Large-scale tests demonstrated that Neoloy® Geocells increase bearing capacity, reduce vertical stress over soft soils
Large-scale model static load tests in test box and two in-situ field test asphalt road constructions were carried out to evaluate the influence of a geocell layer on the load deformation behavior of the soil.
- Geocells increase bearing capacity of infill soil x 1.1-1.7x.
- Vertical stresses were reduced in soft subgrade by ~30% and deflections on the surface were reduced by ~ 25% .
- The performance of 40 cm Neoloy reinforced layer with medium grade infill was equal to a 70 cm unreinforced high quality aggregate layer.
Geocells consist of a series of interconnected single cells that are manufactured from different types of polymers. The geocells are expanded at the construction site and filled with soil. The cell walls completely encase the infill material and provide all-round confinement to the soil. During vertical loading, hoop stresses within the cell walls and earth resistance in the adjacent cells are mobilized which increases the stiffness and the load-deformation behaviour of the soil. Thus the soil-geocell layers acts as a stiff mat and distribute the vertical traffic loads over a much larger area of the subgrade soil. Large scale static load tests were carried out to evaluate the influence of a geocell layer on the load-deformation behaviour of the soil. The test results show that a geocell layer increases the bearing capacity of the infill materials up to three times compared to an unreinforced soil. The vertical stresses on the soft subgrade, measured by eight earth pressure cells, where also reduced about 30 percent. To verify the results of model tests in-situ field test where carried out within different road constructions. Earth pressure cells where installed on the subgrade to measure the influence of the geocell layers on the stress distribution. After finishing the road construction vehicle crossing tests with a 40-ton truck were carried out while the stresses on the subgrade where measured. Compared to an unreinforced test section the stresses beneath the geocell layer were reduced by about 30 percent. In addition to vertical stress measurements, falling weight deflectometer (FWD) measurements were conducted in reinforced and unreinforced test sections. The results show that the deflections measured in geocell reinforced test section were significantly smaller than in the unreinforced section. Back calculated layer modules were significantly higher in the geocell reinforced section compared to an unreinforced section.