2nd Croatian Conference on Earthquake Engineering 2CroCEE

Drained triaxial monotonic experiments represent one of the basic and most used experiments in geotechnical engineering, mostly because results from these experiments represent a starting point for any new research topic. In the case of the experiments in this paper, natural sand borrowed from the terraces of river Vardar in the region of city Skopje is used. The natural sand presents highly uniform sand with only 2% fines, a uniformity coefficient Cu = 2 and mean grain size of d50 = 0.17mm. It can be found at multiple places along the riverbank in different depths and can be expected to be loaded from various sources often dynamic loading caused by roads, railways, etc. Knowing that cyclic preloading can cause significant changes in the strength characteristics of soil, these changes 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 is also investigated not only on the curves of deviatoric stress q and volumetric strain versus axial strain but additionally on the dependency curves that display the influence of the initial density and initial effective pressure on the peak friction angle, Young’s modulus, axial strain at peak and dilatancy angle. The results indicate interesting outcomes concerning the physical behaviour of the investigated sand.