A dynamic model for rapid startup of high-speed landslides based on the mechanism of friction-induced thermal pressurization considering vaporization

Abstract

The friction-induced thermal pressurization mechanism in the shear band is an important reason for the transition of motion state of landslides from creeping to high-speed sliding during their initial startup phase. In this paper, a dynamic model for the startup phase of high-speed landslides with thermo-hydro-vapor-mechanical (THVM) coupling in shear band is established and applied to the Vaiont landslide for case study. The model consists of three governing equations: the equation of motion controls the motion of the overlying slide mass, the heat equation controls the heat or temperature change in the shear band at the bottom, and the pore pressure equation controls the change of excess pore pressure in the shear band. The main variables of these equations interact with each other. In addition to the thermal expansion pressurization of pore water, vaporizing pressurization is systematically considered for the first time in this model. The analysis results of the model applied to the Vaiont landslide show that, at 10 s, the excess pore pressure in the shear band is up to 4.5 MPa, the maximum temperature is 295 °C, and the velocity of each block is in the range of 24~31 m/s. The evolution of excess pore pressure in the shear band is divided into four stages which have been discussed in detail. The THVM model established in this paper can reflect the physical mechanism of thermal pressurization inside the shear band of high-speed landslides during their startup process to a certain extent, and it could also explain why some landslides quickly turn to catastrophic high-speed sliding after they start.