Dynamic Behaviors of Overconsolidated Clay under Cyclic Confining Pressure

Abstract

Cyclic triaxial tests are commonly used to evaluate the mechanical characteristics of subgrade soil under cyclic loads. Most cyclic triaxial tests were conducted on normally consolidated clays, however, some of the subgrade soils are overconsolidated clays. Moreover, both confining pressure and deviator stress are cyclically varying in the stress field induced by traffic loading. Recognizing that, the mechanical behaviors of overconsolidated clays under cyclic triaxial tests with cyclic confining pressure, are the main focus of the investigation. The impacts of both cyclic confining pressure and overconsolidation ratio (OCR) were investigated. Results show that as both OCR and cyclic confining pressure are increased, the accumulated axial strain decreases to a greater extent. Furthermore, the minimum excess pore water pressure decreases with an increase of OCR, while maximum excess pore water pressure remains approximately constant when the OCR exceeds 2.0. As the cyclic confining pressure is increased, so are the maximum and minimum excess pore water pressures. The variations in hysteresis loops with cyclic confining pressures are negligible, while the influence of OCR is greater. Nevertheless, as both OCR and cyclic confining pressure increase, the damping ratio decreases. Based on that, the variations in normalized damping ratio versus accumulated axial strain can be represented by an empirical formula. The proposed formula is not only suitable for normally consolidated clays, but also for overconsolidated clays in cyclic triaxial tests with cyclic confining pressure.