CONSTITUTIVE EQUATION FOR PERMANENT STRAIN OF SAND SUBJECTED TO CYCLIC LOADING.

This paper presents a constitutive equation for predicting accumulated permanent strain of sand subgrade material after any number of repetitions of load. The parameters needed as input to the equation are obtained from a static triaxial test. To develop the equation, duplicate samples were tested by using both static triaxial apparatus and a closed-loop electrohydraulically actuated triaxial system. The dynamic test results were normalized with respect to parameters obtained from the corresponding static triaxial test. Based on the findings, a constitutive equation for permanent strain was developed for flexible pavement design and rehabilitation.