Excess pore water pressure generation in saturated sandy soils subjected to various cyclic stress paths

Abstract

Excess pore water pressure (EPWP) plays an essential role in determining the cyclic undrained behavior of saturated sandy soils. The influence of cyclic stress paths on the EPWP generation in saturated sandy soils has emerged as an interesting issue in recent years. By using a hollow cylinder torsional shear apparatus, this paper presents the results of a systematic experimental study on the isotropically consolidated undrained responses of saturated coral sand under the 90° jump rotation of cyclic principal stresses with various orientations. Laboratory cyclic tests showed that the patterns of EPWP generation in saturated coral sand exhibits three modes that are related to the patterns of cyclic loading and levels of cyclic stress. Moreover, the unit cyclic stress ratio (USR) defined by Chen et al. (2020) can be used as an index for distinguishing among the three modes of EPWP generation under varying cyclic loadings. Furthermore, a unique form of the relationships exists among the EPWP ratio (ru), USR, and cycle ratio (N/NL) for all cyclic loading paths considered. Following this, we propose a model for the generation of ru as a function of the USR and N/NL for application. The wide applicability of this model is validated by using independent experimental data on four siliceous sandy soils in this study and from the literature.