Experimental and analytical investigation of the dynamic behavior of granular base course materials used for China's high-speed railways subjected to freeze-thaw cycles

With the rapid development of high-speed railways (HSRs) in seasonally frozen regions in China in recent years, there is an increasing need for better understanding of how the construction materials behave. In particular, the dynamic behavior of granular base course materials used for China's HSRs subjected to combined actions of cyclic loading and freeze-thaw (F-T) cycles has attracted much attention. In this study, a series of cyclic triaxial tests were performed to investigate the characteristics of granular base course materials. A number of factors including effect of F-T cycles were considered in these tests. As such, representative test results of dynamic shear stress amplitude ( τ ¯ d ), dynamic shear modulus (Gd), and damping ratio (λ) are presented and discussed. Based on the Hardin-Drnevich model, a fitting equation for determining maximum dynamic shear modulus (Gd,max) is proposed. Then, a unified normalized dynamic shear modulus (Gd/Gd,max) curve is drawn and well validated by the test results. Furthermore, equations for λ are expressed in terms of an exponential function of Gd/Gd,max. The test results show that the Gd/Gd,max curves are not completely consistent with previous studies. Overall, this study provides further insights into the dynamic behavior of granular base course materials subjected to F-T cycles.