Study Of Scraping Effect Based On Seismic Landslide Debris Flow

The high-speed long-range landslide debris flow will have an obvious scraping effect with the slope（or ground）in the process of movement,resulting in an increase in the volume of the landslide,which in turn will lead to the expansion of its disaster scope,causing great damage to the local ecological environment,and bringing huge property losses to the local people,resulting in serious threats to life and safety.This paper focuses on the subject of seismic debris flow,and takes the engineering example of“5.12”Wenjiagou landslide debris flow as the research object,designs indoor physical model experiments and numerical simulation experiments of seismic debris flow,discusses and analyses the influence of different seismic acceleration,different slide gradation and different substrate material properties on the scraping effect of seismic landslide debris flow and the mechanism of action,and describes quantitatively The effects of three factors,namely seismic acceleration,slide gradation and substrate material,on the erosion and pearling processes of seismic landslide debris flow are quantified and the energy evolution and energy transfer laws of the debris flow scraping process of seismic landslides are analysed based on energy balance.By studying the time course changes of the impact force and the impact force time effect of the debris flow scraping process,the influence of seismic acceleration,slip body gradation and substrate material on the evolution of the impact force is investigated to explain the scraping effect of debris flow from a mechanical point of view,and then a transient scraping mechanics model between the slip body and the substrate layer of the landslide debris flow is established based on the impact mechanics theory.The above series of studies are intended to provide some theoretical guidance for disaster prevention and control of the scouring effect of seismic debris flows.The main research conclusions are as follows:（1）The process of shovel scraping effect between the slide and the basement layer is mainly manifested by erosion and pear ploughing.The characteristic values are mainly erosion depth h₁,pear ploughing height h₂,erosion length L₁and pear ploughing length L₂.According to the study on the quantification of seismic landslide debris flow,it is found that the effect of seismic acceleration is the largest,the slide grade is the second largest and the basement layer material has the least effect.（2）The scraping process of seismic landslide debris flow is summarised into six main stages:seismic disturbance,high shear out,ramp acceleration,impact erosion,shear push over,and debris accumulation.（3）The transformation mechanism of landslide debris flow under the seismic action of scraping is explored based on the transformation of energy,and the energy evolution law of particles under each factor is analysed.The results show that:as the seismic acceleration increases,the time for the slide to scrape the basal layer increases,and the total energy conversion efficiency increases;as the content of large particles in the slide increases,the time for the slide to scrape the basal layer shortens,and the energy conversion efficiency per unit time increases;as the surface energy of the basal layer material increases,i.e.the viscosity of the basal layer increases,the time for the slide to scrape the basal layer increases,and the total energy conversion efficiency decreases and Energy dissipation increases.（4）As the seismic acceleration increases,the scraping time increases,and the normal and tangential forces at the peak increase gradually;as the content of large particles in the slip increases,the scraping time also increases gradually,and the normal and tangential forces at the peak also increase gradually;as the surface energy of the substrate increases,i.e.the viscosity of the substrate increases,the scraping time also increases gradually,but the normal force at the peak increases gradually,and the tangential force gradually decreases.（5）Based on the equilibrium principle of mechanics,a highly accurate transient scraping mechanics model was constructed for the peak moment of the transient scraping force during the scraping action between the seismic-acting subsurface particles and the substrate layer particles.