FIELD AND LABORATORY EVALUATION OF THE MECHANICAL BEHAVIOR OF UNBOUND GRANULAR MATERIALS IN PAVEMENTS

Abstract

Laboratory and full-scale pavement studies were conducted as a part of an overall program to evaluate the engineering properties and performance of eight gradings of unbound granular roadbase materials. A repeated load triaxial testing program was conducted in conjunction with shear box and permeability tests on unbound mixes with grading curves ranging between the two extremes of the envelope currently used as a specification in the United Kingdom. After analyzing the laboratory results, full-scale trials were conducted using eight experimental gradings. The pavement test strip was divided into eight 22-m bays. Dynamic cone penetrometer, density, and moisture content measurements were performed on the subgrade, capping layer, and roadbase material. The performance of each bay under heavy traffic was monitored for 6 months. The rut depth profile was recorded using an automatic computerized rut profiler, and deflection measurements were recorded weekly by the deflectograph. Falling weight deflectometer testing was conducted three times. The objective of the research was to identify a material that would allow free drainage and hence reduce pumping and excess pore water pressure but maintain a high in situ stiffness with good resistance to permanent deformation.