Geogrids are widely used to enhance the performance of roadways, especially to improve the conditions associated with soft subgrade. However, the results in the literature do not always show the contribution of the geogrid to improve the elastic modulus of the base course layers consistently. This study demonstrates the use of an existing methodology to overcome such inconsistency. The method used in this study is based on sequentially loading the base course surface with three side-by-side lightweight deflectometers (LWD). The findings of this study showed that such an approach enables us to demonstrate the deterioration of the base course when no geogrid is present and the improved behavior with geogrid placed in between the base course and soft subgrade. The study demonstrates the effective use of KenPave analyses and the results from LWD testing to determine modulus improvement factor (MIF) when geogrids are used. Four different geogrids with different characteristics were evaluated and the determined MIF values ranged between 1.39 and 1.64. The findings were used to develop a relationship between the base course thickness and the allowed maximum stress on the base course for different geogrids, where the applied load is limited to keep the base course elastic.
Akmaz et al. (Fri,) studied this question.