Accumulated Deformation of Sand in One-Way Cyclic Loading under Undrained Conditions

Abstract

The problem of development of the deformations in natural slopes, slopes of embankments and dams and quay walls is influenced by the presence of initial shear stress in the soil. Therefore, in this paper an experimental study focuses on accumulation of residual deformation in soil subjected to static shear stress and cyclic stress components under undrained conditions. Furthermore, in such structures during earthquake shaking forces acting in the shear plane are generally one-way cyclic loading without reversing its direction (torsional stress loading only on positive or negative side). Series of torsional shear tests on hollow cylindrical specimens of Toyoura sand with relative density of 40% and 60%, and isotropic stress condition under effective pressure of 98kPa, 196kPa and 294kPa were made in order to investigate the incremental shear strain per cycle during cyclic loading. The influence of confining pressure, isotropic conditions, cyclic stress ratio and void ratio on the accumulation of shear strain are studied.

The experimental results shows a linear relationship between accumulated shear stress and the number of cycles when they are plotted in logarithmic scale. The experimental data shows that shear strain increment during one cycle is dependent on the level of accumulated shear strain. Moreover, the shear strain increment during one cycle when unloading is constant and not depends on the level of accumulated shear strain. Based on these findings and by using the experimental data a relatively simple model for prediction of accumulated deformation of sand can be proposed.