Accumulated Plastic Strain Behavior of Granite Residual Soil under Cycle Loading

In this study, the accumulated plastic strain (APS) of granite residual soil under cyclic loads is investigated by a series of undrained cyclic triaxial tests. Granite residual soil is a special kind of soil that is widely distributed in areas of rapid economic development. Owing to a lack of understanding of the cyclic deformation of granite residual soil, the effects of several essential stress conditions, such as cyclic shear amplitude, initial static deviatoric stress, and effective consolidation stress, are explored and analyzed on the APS growth with loading cycles. The cyclic loads represent the typical traffic load acting on the foundations of subgrade works. Based on the results of tests under various stress conditions, a simple and easily adopted accumulated plastic strain growth (APSG) model is correlated to predict the evolution of APS with loading cycle number. Through comparing the results of separate tests, the APSG model is validated and exhibits its ability to predict the accumulated plastic behavior with satisfactory accuracy. Furthermore, the APS growth with a loading cycle is examined under various stress conditions by the APSG model. The influences of those important stress factors on the APS behavior can be successfully described by two often-used parameters in soil dynamics, that is, cyclic stress ratio and static deviatoric stress ratio, which are involved in the APSGmodel. As a result, the characteristics of plastic deformation of granite residual soil under cyclic loading conditions can be further analyzed by the new model. Although this model is easy to adopt with some accuracy, a more powerfulmodel based on rigorous theory is still needs to be developed in the future. The finding of this study will provide a deeper insight into the cyclic loading behavior of granite residual soils that are often encountered in the subgrade of traffic engineering in China. (C) 2020 American Society of Civil Engineers.