Resilient Modulus Properties of New Jersey Subgrade Soils

008140562000Final Report September 1997-September 2000PDFTech ReportFHWA NJ 2000-01CalibrationModulus of resiliencePavement layersSoil testsSubgrade (Pavements)GeotechnologyHighwaysI42: Soil MechanicsNew JerseyUnited StatesUnited States. Federal Highway AdministrationPapp, Walter J.Maher, AliBennert, ThomasGucunski, NenadNew Jersey. Dept. of Transportation. Division of Research and TechnologyRutgers University. Center for Advanced Infrastructure and TransportationMueser Rutledge Consulting EngineersUnited States. Federal Highway AdministrationUS Transportation CollectionTo effectively and economically design pavement systems, subgrade response must be evaluated. Understanding the importance of subgrade soil response to various loading conditions, the American Association of State Highway and Transportation Officials (AASHTO) and the Strategic Highway Research Program (SHRP) established and refined a Standard Test Method for Determining the Resilient Modulus of Soils and Aggregate Materials. Mechanistic design methods for flexible pavements require the specification of subgrade resilient modulus. The resilient modulus is measured under laboratory conditions that should reflect the conditions the subgrades are subjected to in the field. In this study, a laboratory-testing program was developed to determine the resilient modulus of typical New Jersey subgrade soils. A total of eight soils were tested at different molded water contents to determine their sensitivity to moisture content and cyclic stress ratio. Repeated loading or pumping of the pavement system may induce excess pore water pressure within the subgrade layer thereby reducing the resilient modulus, leading to the premature failure of the pavement. A sensitivity analysis was conducted using an elastic layer computer program to demonstrate the effect of subgrade stiffness on the design thickness of the asphalt layer. As expected, the subgrade stiffness has a dramatic effect on the eventual thickness of the asphalt layer. Laboratory results were used to calibrate a statistical model for effectively predicting the resilient modulus of subgrade soils at various moisture contents and stress ratios. This model will prove to be a valuable tool for pavement engineers to effectively and economically design a pavement system.81