Cold in Place Rock Crushing and Stabilization of Northern Low ...

Berthelot, Gerbrandt, Safronetz, and Sparks. Page: 1ABSTRACTSaskatchewan Department of Highways and Transportation (SDHT) is responsible for maintainingapproximately 6500 kilometers of northern gravel surfaced roads. Many of these northern gravel roads are built onpoorly graded sand subgrades and may contain protruding bedrock and/or large boulders. Because of this,washboarding, protruding rocks, rutting and potholes are common performance problems of many northern gravelroads. Routine blading of these roads is often ineffective because unstable sand does not maintain its shape andcompaction, protruding bedrock and boulders damage motor grader blades, boulders may become dislodged leavingholes in the road, and dislodged boulders are a safety hazard when windrowed along road side-slopes. Clay cappingand base stabilization have been used to provide a stable wearing surface, cover protruding bedrock and largeboulders, and reduce traffic dust. However, the long-term performance of clay capping and base stabilization can behighly variable and the associated costs can make these conventional solutions untenable. As a result, SDHTinvestigated the use of in-place rock crushing and stabilization/modification for northern gravel roads withsignificant proportion of boulders in the grade using a rotomixer/stabilizer. Based on the findings of this study, inplacerock crushing and stabilization/modification is a technically feasible solution for eliminating protrudingbedrock and boulders contained near the surface. However, in-place crushing of boulders with unconfinedcompressive strengths over 50,000 psi resulted in significant damage to the rotomixer mandrel resulting in anapproximate cost of just under $13,684 CDN per kilometer. in situ rock crushing with subgrade stabilization anddouble seal was found to cost approximately $52,017 CDN per kilometer.