This paper is the result of geological hazard investigation engineering.

Objective The change mechanism of mudflow mass in the motion process is an important research topic in the fast landslides and mudflows. During shearing, basal erosion is recognized as a dynamic interaction between the original moving material and the entrained basal topsoil along the contact surface.

Methods In the current study, massive geohazards occurred in Tianshui on July 25, 2013 were selected as the research objects. The erosion rate was first introduced, and then the dynamic numerical model of basal erosion based on three-dimensional continuous medium was established to analyze the response relationship between the motion behavior and the dynamic process of mudflow on the basal erosion.

Results The results show that the motion process of mudflow on the slope of Nanyu Village is mainly divided into a rapid acceleration stage, a fluctuation stage, and a rapid deceleration stage. During the rapid acceleration stage, the effect of basal erosion on the mudflow motion behavior is slight. During the fluctuation stage, the effect of basal erosion on the dynamic process of mudflow is significant, and the erosion volume and the total dynamic energy increase dramatically. This exacerbates the intensity and scope of disaster, and the slope toe is severely eroded. During the rapid deceleration stage, the basal friction quickly dissipates the total dynamic energy, and the erosion volume grows slowly and tends to be stabilized. With the gradual increase in erosion rate, the basal erosion effect gradually enhances, and the running time, moving distance, average thickness, erosion volume, and total dynamic energy of the mudflow increase by an exponential function. The average velocity decreases slightly as an exponential function with high fitting accuracy, which can be used for the qualitative analyses and quantitative calculations of the basal erosion effect on the mudflow.

Conclusions The numerical results are more consistent with the actual cases considering the basal erosion. The numerical model is more suitable for the evaluation and prediction of the disaster intensity of such mudflows and landslides. The findings provide theoretical support for the dynamic mechanism and technical guidance for the prevention and control of mudflow disasters.