Equivalent California Bearing Ratios of Multiaxial Geogrid-Stabilized Aggregates over Weak Subgrade

Geosynthetics have been successfully used to stabilize granular aggregate over weak subgrade in recent years. In some actual applications, geosynthetics are first used to stabilize aggregates over weak subgrade as construction platforms to carry construction loads, and then the construction platforms become subgrade in pavement structures. Unfortunately, no commonly accepted method is available to quantify the benefit of construction platforms with geosynthetics in pavement design. This study aimed to quantify this benefit by treating the geosynthetic-stabilized construction platform as an “equivalent subgrade.” The quantification was based on the cyclic plate loading test results of nine test sections of nonstabilized and multiaxial geogrid-stabilized aggregate over weak subgrade and five test sections of homogeneous subgrade with California bearing ratios (CBRs) ranging from 2.9 to 9.5. The permanent deformations of these test sections were recorded and used to estimate the equivalent CBR values of the geogrid-stabilized aggregate over weak subgrade. The test sections that had the same performance (i.e., permanent deformation) under the same number of loading cycles were considered equivalent. The analysis of test results shows that the equivalent CBR values of the nonstabilized and geogrid-stabilized test sections decreased with the increase of the load intensity. The percent of equivalent CBR increase of the granular bases over the weak subgrade due to the inclusion of a geogrid ranged from 30% to 85%.