Modified Monotonic Simple Shear Tests on Silica Sand

Abstract

Two major modifications were made to the Norwegian Geotechnical Institute (NGI) direct simple shear apparatus, and the wire reinforcement was replaced by cell pressure. A circumferential deformation device was developed and mounted around the cylindrical specimen. The soil specimen cross-section area change was corrected, based on the monitored values from radial deformation. The advantage under this configuration is that a truly K 0 condition could be maintained during shearing and the area correction can be applied in data reduction. The monotonic simple shear behavior of silica sand (loose and dense conditions) was investigated and stress states of pure shear and K 0 condition were applied to the specimen. Both stress path and the mobilized shear resistance under different consolidation pressures were also studied. K 0 values and confining stress levels were found to greatly influence both the peak and the residual shear stress mobilization. Based on the testing data, radial changes were relatively small within 10% shear strain, beyond which great radial change would happen. Although all specimens were sheared to their critical states, their stress paths stopped at different locations, thus yielded different critical state lines (CSL). The slope of CSL at K 0 = 0.5 condition was higher than that at pure shear condition.