EXPERIMENTAL INVESTIGATIONS IN NONLINEAR VISCOUS BEHAVIOR OF SUBGRADE SOILS UNDER TRAFFIC-INDUCED LOADING

Abstract

This paper concerns experimental investigations of elastic nonlinearity of subgrade soils under vehicle-induced repeated loading. Two groups of soil samples (A8 and HA) were used to conduct triaxial shear tests with repeated loading. Investigations in this paper have included three aspects. First, a new nonlinear elastic model is introduced. In this model, shear modulus or resilient modulus is assumed to be a function of the recoverable strain and the number of repetition. The new model has distinguished itself from those introduced by other investigators, especially in studies of the shear and resilient modulus. Second, the shear modulus or resilient modulus introduced in this paper not only allows one to study how shear and resilient modulus change with recoverable strain but also gives an opportunity to investigate effect of repetitions on the resilient modulus. An introduced function relates the shear modulus to the effect of repeated loading. Introducing such a function actually opens a door to for one to conduct further investigations in behavior of material fatigue and creeping because such a model is featured as a nonlinear relation of stress-strain or stress-strain-time. Third, three consecutive parameters are calibrated through results gained from triaxial tests performed in the laboratory. It is found that when two parameters are negligibly small, this model reduced to a linear elastic model. A nonlinear relation between normalized deviatoric stress and recoverable strain is discussed. Effect of shear stress level on the elastic nonlinearity has been studied as well.