The Influence of the basal erosion on kinetic process of loess slope debris flow

Objective The mechanism of mass changes in the debris transportation process is an important topic in the study of fast landslides and debris flows. Basal erosion is recognized as a dynamic interaction between the original moving material and the entrained basal topsoil shearing along its non-slip contact surface. Methods In this study, taking the July 25, 2013 Tianshui group-occurring geohazards as the research object, the erosion rate is introduced, and a three-dimensional dynamic numerical continuum model was established to analyze the response relationship between the motion behavior and the kinetic process of debris flow to the effect of basal erosion. Results The results show that the motion process of debris flow on the slope of Nanyu Village is mainly divided into a rapid acceleration stage, a fluctuation stage, and a rapid deceleration stage. In the rapid acceleration stage, the effect of basal erosion on the debris flow behavior is not significant. During the fluctuation stage, the effect of basal erosion on the kinetic process of debris flow is very evident, and both the erosion volume and the total kinetic energy increase dramatically. This exacerbates the disaster, and the slope's base is severely eroded. In the phase of rapid deceleration, the basal friction dissipates the total kinetic energy, and the erosion volume grows slowly and tends to be stabilized. With the gradual increase in erosion rate, the basal erosion effect is gradually enhanced, and the running time, moving distance, average thickness, erosion volume, and total kinetic energy of the debris flow are increased by an exponential function. The average velocity decreases slightly as an exponential function with high fitting accuracy, which can be used for the qualitative analysis and quantitative calculation of the basal erosion effect on the debris flow. Conclusions The simulation results considering basal erosion are more consistent with the actual situation, and the model with the erosion rate is more suitable for the evaluation and prediction of the disaster intensity of such debris flows and landslides. This study provides theoretical support for the kinetic mechanism and technical guidance for the prevention and control of debris flow.