| The high-speed landslide debris flow interacts strongly with the base material along the runoff path.In this process,it shears and destroys the base material and carries it forward together.This phenomenon is called "shovel scraping effect".The existence of shoveling effect significantly changes the dynamic characteristics of the original sliding mass,resulting in a significant increase in the volume of sliding mass in the process of high-speed migration,increasing the difficulty of landslide debris flow disaster prevention and control.In practical engineering,the process of shoveling and scraping of landslide debris flow is complex and sudden,and there are many influencing factors,and limited by monitoring technology,so it is difficult to study in situ.In order to reveal the influence law and mechanism of"shovel scraping effect" and its related influencing factors,based on the mechanism of debris flow shovel scraping base course,this paper introduces the concentration suspension model to describe the dynamic characteristics of soil mass in the mixing area,so as to establish the HBP model considering the base course entrainment and solve it with the SPH method;two small-scale constant gravity models are simulated with the open-source SPH software dualsphysicv4.4 The validity of the model is verified by the model test.On this basis,the formation process and mechanism of "scraper effect" are analyzed.Then,the influence of landslide debris flow and the change of physical and mechanical parameters of the base on the movement law of sliding mass,the failure form of the base and the shoveling effect are systematically discussed.The mechanism of various influencing factors is preliminarily revealed from the perspective of constitutive equation and energy conservation.The numerical calculation results show that:(1)The shoveling and scraping effect of landslide debris flow on the base can be divided into the erosion effect of downward erosion of the base and the ploughing effect of forward extrusion of the base.The erosion effect refers to the effect that the landslide debris flow scrapes the base material and moves together in the process parallel to the base movement.Ploughing effect refers to the effect of plastic flow caused by the landslide debris flow pushing the base material forward.At the same time,numerical experiments show that ploughing effect is the main reason for the increase of the actual influence range of dry debris flow.(2)The physical and mechanical parameters of the base material have a great influence on the shoveling effect and the dynamic characteristics of the sliding mass.The erosion depth and the base uplift range caused by the debris flow increase with the base thickness and converge to a certain limit value.The increase of internal friction angle,cohesion and dynamic viscosity of base material can reduce the erosion depth of debris flow on the base,while only the increase of cohesion can significantly reduce the uplift range of base caused by shovel scraping.(3)The erosion depth and base uplift range caused by debris flow increase with base thickness and converge to a certain limit value,When the thickness of the base course is not enough,the influence range of scraping depth and debris flow increases with the increase of the thickness of the base course,while when the thickness of the base course is enough,the maximum erosion depth of debris flow is only related to the movement energy of debris flow reaching the base course.(4)The influence of the change of the physical parameters of the sliding mass on the shoveling effect is more complex.Within the reasonable range of the physical and mechanical parameters of the soil mass,increasing the mechanical parameters of the sliding mass will increase the plowing effect.However,due to the large reduction of the flow range of the debris flow,the uplift range of the base course will decrease in different degrees.Increasing the internal friction angle and cohesion of the sliding mass will help to reduce the base course The scraping depth of the material,while increasing the dynamic viscosity of the sliding body will make the scraping depth decrease first and then increase. |
