One-Way Cyclic Behavior of Saturated Clay in 3D Stress State

The soil stress state is three-dimensional (3D) in many applications, including the case of traffic loading. This aspect has been rarely undertaken in the laboratory. This paper investigates the one-way cyclic behavior of a reconstituted saturated clay based on a true triaxial apparatus, considering the factors of cyclic stress ratio (CSR), coefficient of cyclic intermediate principal stress ($b_{\mathrm{cyc}}$), and overconsolidation ratio (OCR). Emphasis is put on the effects of these factors on the behavior of major principal strain, intermediate principal strain, and resilient modulus in the direction of major principal stress. The results indicate that the development rate of major principal strain is reduced greatly by increasing $b_{\mathrm{cyc}}$, and the direction of intermediate principal strain is changed from negative to positive. The resilient modulus is increased significantly and almost linearly by the increase of $b_{\mathrm{cyc}}$. The relationships of major principal strain, intermediate principal strain, and resilient modulus against CSR all show that one-way cyclic shakedown behavior of saturated clay is independent of OCR and can be determined by $b_{\mathrm{cyc}}$. A specific cyclic stress boundary ratio, i.e., the allowable cyclic stress ratio, which was proposed for soft clays as a reference of deformation control under traffic loading, is determined as 0.347, 0.364, and 0.394 from the tests under $b_{\mathrm{cyc}}=0$, 0.4, and 0.8, respectively.