Effective stress change and post-earthquake settlement properties of granular materials subjected to multi-directional cyclic simple shear

In order to investigate the effect of cyclic shear direction on the properties of saturated granular materials, such as effective vertical stress reduction and post-earthquake settlement, several series of multi-directional cyclic simple shear tests under constant volume conditions are performed on Toyoura sand and granulated blast furnace slag (GBFS), as an alternative material. The GBFS has particular properties such as light weight, high shear strength and high permeability, and it is considered to be one of the most promising materials in geotechnical engineering. From the test results, it is clarified that the shear strain amplitude has a significant effect on the changes in the effective stress of granular materials. However, at higher levels of shear strain amplitude, the cyclic shear direction has little influence on the effective stress reduction. It is found that the vertical strain, after the cyclic shearing of the GBFS samples, was lower than that of the Toyoura sand under the same test conditions. Finally, to evaluate the changes in effective stress under uni-directional and multi-directional cyclic simple shear conditions, an estimation method is represented by a function of cumulative shear strain G* and resultant shear strain Γ. The validity of this proposed model is confirmed by comparing the experimental and the calculated data obtained under multi-directional cyclic simple shear conditions.