Effect of Strain Measurements on Resilient Modulus of Sands

The 1986 AASHTO Guide for Design of Pavement Structures and several other mechanistic design approaches use resilient modulus (M_r) as a fundamental property to characterize highway materials. Precise measurement of resilient deformations during laboratory repeated load tests is the key element in obtaining proper and accurate resilient modulus values. An extensive experimental program was initiated at Louisiana Transportation Research Center to develop a testing and interpretation procedure for estimating the resilient modulus of Louisiana soils. This paper presents the results conducted on a locally available blasting sand. A statistically designed experimental factorial was used to evaluate the repeatability and the influence of measurement systems as well as AASHTO procedures. Two types of in-cell measurement systems, one relative to top and bottom platens and the other within the mid-third of the specimen length were used. Also, two different test procedures, AASHTO T-292 and T-294 were examined. Results of this study indicate that the test results are repeatable and the measurement systems and AASHTO procedures do influence the resilient modulus results. Correlations between M_r and bulk stress were also developed using θ model.