Energy dissipation in monotonic and cyclic simple shear tests considering initial static shear stress

Flow liquefaction and flow slide of soils are two fundamental concerns in current geotechnical engineering. Previous studies mainly focused on level ground conditions where soils were consolidated under isotropic or K₀ conditions. However, in geotechnical engineering, sloping conditions are more unfavorable for geostructure because of the inherent initial shear stress induced by the self-weight of slope soils. In this study, a series of monotonic and cyclic bidirectional tests are conducted on Leighton Buzzard sand (Fraction B) to investigate the effects of initial shear stress on soil behavior. This study employs an energy-based method to interpret the test results by establishing a correlation between energy dissipation and soil behavior. The monotonic tests show that the energy dissipation for initiating strain-softening behavior is highly dependent on the level of initial shear stress but independent of the initial shear stress direction. The cyclic tests show that both the magnitude and direction of initial shear stress can affect the liquefaction resistance and cumulative energy. Through the energy-based method, this research provides new insights into evaluating soil strength in sloping ground conditions.