Study on the causes, deformation and failure mechanisms of loess multistage collapse

Loess has typical vertical joint development characteristics, making it prone to develop relief joints under the action of pore water pressure and slope unloading, which frequently cause collapse disasters. Such disasters often exhibit multi-level secondary properties. This study takes the multistage loess collapse disaster in Dongguan Village, Daning County, China, as a case study and combines field investigations with numerical simulation to invert the deformation and failure mechanism of the slope using the gravity amplification induction method. The numerical simulations and field investigation reveal the coexistence of sliding and tilting as the failure mechanism of the multi-fractured slope. The slope failure is observed to begin with weathering cracks at the slope foot, and the front block undergoes sliding failure. Moreover, the rear slope undergoes toppling failure due to the deterioration of the crack bottom by water and the loss of the front support. This is consistent with the field investigations and analysis results. The gravity amplification induction method can overcome the problems arising from the difficulty in quantitatively investigating the loess fractures characteristics in slope failure research, providing a theoretical reference for case studies of slopes with fractures. The results reveal the causes, deformation and failure mechanisms of multistage loess collapse, and introduce an effective numerical method for inverting and predicting the deformation and failure of such collapse phenomena. This study has important theoretical and practical significance for the prediction and prevention of loess collapse.