Influence of Support Conditions on Roller-Integrated Machine Drive Power Measurements for Granular Base

Abstract

A controlled field study was conducted to evaluate the influence of underlying layer support conditions on roller-integrated machine drive power (MDP) measurements. Multiple layers of granular base material were placed over a section of wet/soft subgrade and a section of concrete base for comparison. The material was compacted in layers using a 12-ton vibratory padfoot roller. MDP and in-situ spot test measurements were obtained on each layer and the results were statistically analyzed. Results indicate that compaction layer MDP measurements are strongly dependent on stiffness and heterogeneity of the supporting layer. If relatively stable and homogenous support conditions exist, the effect is not statistically detectable. Although the compaction layer properties (as measured by in-situ test measurements) are relatively uniform, the MDP measurements tend to capture the variability of the underlying layers. Post-construction tests by carefully excavating the compaction layers showed significant improvement in stiffness of the granular base layers compared to the initial compaction layer measurements. The reason is attributed to possible densification of underlying layers during compaction of the layers above and an increase in lateral stresses during compaction.