In the 1986 aashto guide for the design of pavement structures, subgrades and granular base layers are evaluated by the resilient modulus test. Inclusion of the resilient modulus test was prompted by the need for a rational evaluation method. Resilient modulus is a measure of a material's deflection behavior. Since pavement life and surface deflection are strongly related, resilient modulus is a fundamental and rational material property that needs to be included in pavement design. The effects of variations in subgrade resilient modulus on various design parameters and on the aashto design thickness are examined. The seasonal variations of subgrade resilient modulus with moisture fluctuation and freezing and thawing are discussed; and methods for selecting a single design resilient modulus are examined. However, resilient modulus does not measure all of the material properties that can influence pavement behavior. Consequently, resilient modulus should not be the only property used in selecting a pavement material or in judging the material's structural contribution to the pavement. This paper appears in transportation research record no. 1196, Pavement evaluation and rehabilitation.
Abstract