EFFECT OF PRIOR CYCLIC LOADING ON TRIAXIAL MONOTONIC EXPERIMENTS

Abstract

Drained triaxial monotonic test is one of the most frequently used experiments in geotechnical engineering, mostly because its results are starting points for many research topics. This paper presents triaxial drained monotonic experiments on natural sand borrowed from the terraces of river Vardar, that passes through Skopje. This Skopje sand is highly uniform sand with only 2% fines, and a uniformity coefficient Cu = 2 with mean grain size of d50 = 0.17mm. It can be found at multiple places along the riverbank of Vardar River at different depths. Since this is an urban area, such sandy layers can be exposed to different sources of dynamic loads (traffic from roads, railways, factories, etc.) Knowing the fact that cyclic preloading has effects on the soil strength characteristics, these effects were investigated in the case of prior cyclic loading on consolidated drained triaxial compression monotonic test. The specimens were prepared using wet-tamping method at high range of different initial relative densities, then confined at three levels of initial effective stress p0 = 50, 100 and 200kPa before shearing. The effect of the number of cycles and their amplitudes are also investigated not only on the curves of deviatoric stress q and volumetric strain ev versus axial strain e1 but additionally on the dependency curves that display the influence of the initial density IDO and initial effective pressure p0 on the peak friction angle fp, Young’s modulus E50, axial strain at peak ep and dilatancy angle y. The results indicate interesting outcomes concerning the physical behaviour of the investigated sand.