Identifying fatigue damage of mudded intercalations based on dynamic triaxial test

Abstract

Fatigue damage caused by cyclic dynamic loading may deteriorate strength parameters of mudded intercalations. This research work aimed at defining a new fatigue damage variable expression and revealing the fatigue damage evolution laws of mudded intercalations by conducting dynamic triaxial tests. The specimens were collected in China and remodeled. The test results indicated that the dynamic stress-strain curves of mudded intercalations represented obvious strain-hardening characteristics. The new fatigue damage variable expression was formulated according to Ramberg-Osgood strain-hardening law applied to a three-direction stress state. The fatigue damage evolution laws of mudded intercalations could be described by a low-cycle damage evolution model and could be aligned with dynamic strength failure laws. The fatigue damage deepened with an increase in the cyclic ratio. The fatigue damage evolution rate was correlated with the clay mineral composition and percent of clay size particles (strongly), water content (moderately positive), confining pressure (weakly positive), and the cyclic ratio (initially, negative and then, positive).