Loess contains predominately silt-sized quartz grains bonded by various cementation agents, which is of significant interest to understanding the mechanical properties of lightly cemented soils, such as tailings sand. Loess is problematic upon wetting as its metastable structure can rapidly transform from a cemented solid body to a fluidized material. The large-strain behaviours of intact and reconstituted specimens are compared in light of the results of a series of isotopically consolidated undrained (CIU) tests which shows state-dependent flow instability due to the effect of structure. A constitutive understanding is gained using the NorSand model by comparing the computed undrained behaviours of intact and reconstituted loess at the same state parameter. Additionally, the small-strain stiffness reflected by the wave velocities of intact specimens is considerably higher than that of the decemented specimens, indicating strong cementation-controlled small-strain behaviours. These results confirm the strong effect of structure on flow instability. The experimental data of the centrifuge modelling on loess flowslide induced by the increasing phreatic surface is discussed to further analyze the failure process, emphasizing the effect of changing slope geometry and pore-water pressure on the flow initiation. The drained-to-undrained transition in the loading path of loess is simulated and indicates a rapid reduction in strength under such a transition for loess, thereby the triggering mechanism of loess flowslides.
Dr. Liu is an Assistant Professor in the Department of Civil and Environmental Engineering at the University of Alberta. Dr. Liu received an M.Eng. degree in civil engineering for undergraduate studies at the University of Bristol in the U.K. in 2011. He received an M.S. degree in civil engineering in 2016, an M.S. degree in computational science and engineering in 2019, and a Ph.D. degree in civil engineering in 2019 from the Georgia Institute of Technology in the U.S. A core focus in his research has been the analyses of natural and human-induced disasters. His research is centered on developing more resilient, intelligent, and sustainable civil engineering solutions by analyzing and mitigating landslides and evaluating and improving the design and performance of resilient infrastructures for post-disaster mitigation and community reconstruction. Dr. Liu serves as the co-chair of the Virtual Reconnaissance Program for the Geotechnical Extreme Events Reconnaissance (GEER) Association, an NSF-sponsored organization that responds to natural and human-induced geotechnical disasters worldwide.