Deformation characteristics of saturated clay in three-dimensional cyclic stress state

Abstract

The dynamic stress field induced by moving loads is three dimensional, involving the cyclic variation of major, intermediate, and minor principal stresses, while so far very limited laboratory studies have been undertaken on the one-way deformation behavior of saturated clays in three-dimensional stress state. In this study, an advanced true triaxial apparatus, which can apply cyclic major and intermediate principal stresses simultaneously, is employed to carry out a total of 65 one-way cyclic tests on both normally and overconsolidated clays. Four values of overconsolidation ratio (OCR), five values of bcyc, which is termed the coefficient of cyclic intermediate principal stress, and a wide range of cyclic stress ratios (CSR) are tested. Emphasis is put on the effects of bcyc and OCR on the characteristics of permanent major and intermediate principal strains. Test results show that the increase of bcyc significantly reduces the accumulation of major principal strain, and linear relationships are observed between the permanent major principal strain and bcyc for test data with the same CSR, OCR, and cycle number. A critical value of bcyc ≈ 0.5, at which the permanent intermediate principal strain changes from tension to compression, is observed for the remolded clay. Furthermore, an empirical model is proposed, allowing the long-term deformation of saturated clays to be predicted in three-dimensional cyclic stress state.