Movement Mechanism Of Turning-type Landslide Debris Flow In Valley Topography

Turning-type landslide-debris flow often occur in valley topography,which direction of initial motion and extension direction of valley downstream are not in a straight line.Sliding bodies is not completely blocked by the slope on both sides of the valley and stop moving along the open area of the valley downstream with a relatively remote distance.The research on the movement mechanism of turning-type landslide debris flow is not only helpful to improve the understanding of the landslide phenomenon,but also helpful for the prediction of potential threat area and the assessment of landslide disaster intensity.In this paper,the analysis of landslide data and investigation of landslide site,model test and numerical simulation are used to study the movement mechanism of turning-type landslide debris flow including the site characteristics,movement and accumulation characteristics and the action mechanism of terrain factors on motion parameters.Based on the literature survey and the landslide field investigation,this paper summarizes the site characteristics of the turning-type rock avalanche in gully and the site types are classified into three categories.The analysis of macroscopic movement characteristics of turning-type landslide shows that the movement parameters of turning-type landslide debris flow are mainly controlled by the Landslide scale?V?and landslide drop of slippery area?H₁?,and the influence of the slope angle of acceleration area???,the slope angle of deceleration area???and deflection angle???on motion parameters can not be ignored.At the same time,an empirical prediction model of movement distance is proposed.Indoor model tests were conducted to study the effect of deflection effect on the characteristics of landslide movement and accumulation.The research shows that the deflection effect mainly affects the mass-front velocity,movement distance,accumulation mode and accumulation thickness distribution of landslide debris flow.Based on the model test,the numerical model of landslide-debris flow is established,and the reliability of the numerical model is verified by comparing with the model test conclusion,and the influence of deflection angle on the movement velocity and particle distribution of the landslide debris flow is further analyzed.Finally,the mechanism of the effect of terrain factors on landslide motion parameters is studied based on the numerical model of debris flow.The results show that the significant topographic factors of the distance after deflection and the velocity difference before and after deflection are the slope angle of acceleration area and the slope angle of deceleration area respectively,and the nonlinear relationship model between the motion parameters and the significant topographic factors of the turning-type landslide debris flow is obtained.