Mechanistic Investigation of Granular Base and Subbase Materials A Saskatchewan Case Study

Saskatchewan Highways and Transportation commonly specify three types of subbase course and three types of base course materials for conventional road building. These specifications are primarily based on grain size and were developed years ago at a time of lower variation in pit run quality. Today, Saskatchewan Highways and Transportation are experiencing reduced pit run availability and increased variability in pit run quality, especially with respect to fines content. This is resulting in higher pit wastage and with the increased opportunity for undesirable material, there is a higher risk for varied performance in the field. At the same time, traffic loadings have exceeded the original safety margin incorporated into the empirical based granular specifications used today. This study investigated a mechanistic characterization protocol of typical Saskatchewan Highways and Transportation specified granular materials to quantify any significant difference that exist may in the mechanistic behaviour as a function of fines content, moisture content and cement modification. Samples were characterized using unconfined compressive strength and dynamic frequency sweep analysis to characterize the relative elastic and inelastic bulk behaviour of the various granular materials. Based on the findings of this research, significant variability in the mechanical behaviour of typical Saskatchewan specified granular materials was observed across varied fines content and cement treatment under typical Saskatchewan field state conditions.