Investigating the Coupling Effect of Loading Rate and Initial Shear Stress on Landslide and Soil Liquefaction within an energy-based framework

The coupling effect of loading rate and initial shear stress on landslide and liquefaction-induced flow slide is a major concern in engineering geology, and it has been extensively investigated from the perspective of stress or strain criteria. Initial static shear stress is generated in sloping ground conditions and increases the complexity of the stress state of soil, making the assessment of loading rate effects more challenging. This paper presents a systematic experimental study on Leighton Buzzard sand, aiming to interpret major concerns on loading rate and initial shear stress effects within an energy-based framework. The cumulative dissipated energy per unit volume is used to characterize the shear strength of sand in designed monotonic tests and the cyclic mobility of sand in liquefaction tests. Monotonic test results show that increasing loading rates significantly results in higher soil strength, while the cumulative dissipated energy at peak stress is independent of loading rates. For cyclic tests, oval-shaped shear stress paths with various frequencies are employed to simulate the stress condition commonly induced by seismic events. The cumulative dissipated energy for triggering flow failure or liquefaction can be predicted by a multi-factors model, and the model is governed by relative density and initial stress states. This energy-based method, utilizing the distinct pore pressure (pp)-cumulative energy (W) relationship, offers a unified and coherent framework for comprehending the complex interactions between loading rate and initial shear stress in soil strength determination while also providing a means to quantify these effects in practical engineering.