Resilient Response of Tennessee Subgrades. Volume 1. Laboratory Testing, Modelingand Alternative Test Method

摘要

The flexible pavement design procedures presented in the 1986 AASHTO Guide forDesign of Pavement Structures require the specification of mechanical properties for the asphaltic concrete, base course, and soil subgrade. The stiffness of the soil subgrade is represented by the resilient modulus, M(sub r) which replaces the empirical soil support value used in the earlier Design Guides. Although mechanistic design methods employing M(sub r) offer many advantages over empirical methods, a value for M(sub r) must be specified for each subgrade material encountered on a pavement project. Unfortunately, the laboratory determination of M(sub r) is too complex and time consuming to be applicable on a production basis. Therefore, alternative methods for the determination or estimation of M(sub r) are appropriate, and are in fact suggested in the AASHTO Guide. To permit the estimation of the response of Tennessee subgrades with a minimum of laboratory testing, two rational procedures based on index and classification data were developed. Standard index test data on samples obtained from throughout the state were tabulated in a Design Handbook with resilient modulus (M(sub r) test) response. A statistical model was developed the permit the direct calculation of resilient response. In addition, an Alternative Test Method (ATM) for the resilient modulus test was developed, and a protype device constructed and tested. Results from the ATM, which is based on a standard proctor sample, are compared with the response obtained from traditional resilient modulus tests conducted on triaxial specimens. The preliminary results suggest that the ATM can provide estimates of resilient modulus suitable for most design applications.