Numerical modelling of the long runout character of 2015 Shenzhen landslide with a general two-phase mass flow model

High fluid content or pore-fluid pressure is generally the main reason for the triggering and high mobility of landslides. A catastrophic landslide occurred at Hongao construction waste dumpsite in the Guangming New District of Shenzhen, China, on Dec 20, 2015. Due to the high water content of soil in the source area, this landslide propagated over an extremely long travel distance, with maximum length and width of the affected area 1100 m and 630 m, respectively. High water content pesents a great challenge to numerical methods. In order to simultaneously include the evolution of the solid and fluid components in the mixture, a general two-phase mass flow model of Pudasaini (J Geophys Res 117: F03010, 2012) has been employed in our simulations. The complex interactions between the solid and fluid phases, including buoyancy, the virtual mass force, generalized drag and enhanced non-Newtonian viscous stress, are considered in this two-phase flow model. These are essential aspects in the motion of landslides consisting of viscous fluid and solid particles. Based on the actual geology and engineering conditions, runout characteristics of the Shenzhen landslide were analyzed numerically. The principal reasons for the long runout character and the inundation are discussed based on the physics-based model and high-resolution numerical results.