Pavement subgrade resilient modulus design values for Michigan's seasonal changes

677046718Final report.PDFTech ReportRC-15312002-0532Soil testsPavement designModulus of resilienceSubgrade materialsMichiganMichigan. Dept. of Transportation. Construction and Technology DivisionBaladi, GilbertDawson, TylerSessions, ColinMichigan State University. Dept. of Civil and Environmental EngineeringNTL-HIGHWAY/ROAD TRANSPORTATION-Construction and MaintenanceNTL-HIGHWAY/ROAD TRANSPORTATION-DesignNTL-HIGHWAY/ROAD TRANSPORTATION-Soils and GeologyUS Transportation CollectionThe resilient modulus (MR) of roadbed soil plays an integral role in the design of pavement systems. Currently, thevarious regions of the Michigan Department of Transportation (MDOT) use different procedures to determine theMR values. Most of these procedures are applicable to the new Mechanistic-Empirical Pavement Design Guide (MEPDG) level 3 design only and the 1993 AASHTO design guide. Therefore, a consistent, uniform, andimplementable procedure that meets the requirements of the M-E PDG for level 1, 2, and 3 designs and the 1993AASHTO Design Guide was developed.In this study, the State of Michigan was divided into fifteen clusters where the physical and engineeringcharacteristics of the soils were similar. The clusters were then divided into ninety nine areas to narrow down theranges of the engineering and physical characteristics of the soils. Disturbed roadbed soil samples were collectedfrom seventy five areas, and twelve undisturbed soil samples (Shelby tubes) were collected from areas with CL andSC roadbed soils. The soil samples were subjected to simple tests (moisture content, grain size distribution, andAtterberg limits when applicable), and cyclic load triaxial tests to determine the soils resilient modulus values.Predictive correlation equations were developed to estimate the MR values of the roadbed soil based on the resultsof the simple tests.Deflection data from Falling Weight Deflectometer (FWD) tests conducted throughout the state were obtained fromMDOT. The deflection database consisted of hundreds of previous FWD tests that were conducted on variousprojects over the last 20+ years and eighty FWD tests conducted as part of this study. All FWD data files withsufficient data were analyzed to backcalculate the roadbed soil MR values. Comparison between the laboratory andthe backcalculated MR values indicated that the two values are almost equal when the stress boundaries used in thelaboratory tests matched those of the FWD tests.The report includes the recommended MR design values are provided on state map and in table format