Behavior of geosynthetic-reinforced aggregate platforms over soft subgrades

The purpose of this study was two-fold: (i) to develop a quantitative method for selecting the thickness of geosynthetic-reinforced working platforms so as to limit deflections during construction to a specified level and (ii) to quantify the structural contributions of four different geosynthetic-reinforced granular layers used for working platforms to the overlying pavement structure. A series of tests were conducted in a large-scale model experiment (LSME) and in the field using a falling weight deflectometer (FWD) to achieve these goals. Two select granular materials (breaker run and Grade 2 gravel) and four geosynthetics (a geogrid, a woven geotextile, a non-woven geotextile, and a drainage geocomposite) were used.; An equivalency chart was developed showing the reduction in working platform thickness using geosynthetics for a given deflection under construction loads. The chart shows that the effect of geosynthetic reinforcement is particularly noticeable when a smaller total deflection is required or the section is thinner. Relationships shown in the equivalency chart are based on the LSME tests for the specific geosynthetics used in this study and for a very soft subgrade condition (California bearing ratio ≤1). Therefore, site-specific criteria should be considered when using the chart. However, the methodology developed can be used in other reinforced working platforms and has practical implications for pavement designers.; Analysis of falling weight deflectometer tests conducted over five seasons (October 23, 2000–October 21, 2002) shows that the elastic modulus depends on the type of the geosynthetic reinforcement. Spatial geometric means of the elastic moduli for the geosynthetic-reinforced working platforms range between 118 and 170 MPa, and are comparable to that of a 0.84-m thick layer of unreinforced breaker run. Including the geosynthetic-reinforced working platforms as part of the pavement structure increase the elastic moduli by 20% to 80% and the layer coefficient (a₃) by 10% to 41% depending on the geosynthetic type.