滑坡冲击铲刮变量的计算方法研究

Study on calculation method of landslide impact and scraping variable

高速远程滑坡运动过程中,冲击铲刮效应不仅增加滑坡的体积与规模,而且会增大滑坡成灾范围,风险预测与判断出现明显误差,导致灾难性事件的发生。目前对于高速滑坡的铲刮深度、铲刮范围和铲刮体积等变量计算往往是采用基于经验的铲刮率算法,其是通过体积增量来反算铲刮变量的数学方法,而实际情况中高速滑坡的冲击铲刮是滑体冲击力和地表可铲刮材料之间的力学屈服破坏作用的结果。本文基于接触力学、弹塑性力学和岩土力学,提出了地表可铲刮层在附加冲击荷载作用下铲刮变量的理论计算方法,认为竖向冲击和切向剪切是滑体冲击铲刮过程的两种主要作用方式。结合实际岩土体材料参数,发现不考虑切向荷载时,铲刮层塑性区主要以竖向破裂区为主,考虑切向荷载时,铲刮层塑性区沿切向迁移,直至塑性边界贯通至地表,符合实际情况,实现了对铲刮变量的定量化计算。

In the dynamic process of a rapid and long runout landslide,the impact and scraping effect not only increases the volume and scale of landslide,but also leads to the increase of landslide disaster scope,leading to obvious errors of risk prediction and judgment and the occurrence of catastrophic events.At present,most of the calculation of variables such as scraping depth,scraping range and scraping volume of high-speed landslide is based on an empirical erosion rate algorithm and the mathematical method of backward calculation of scrap by volume increment.But in reality,the impact and scraping of high-speed landslide is the result of the mechanical yield failure between the impact force of sliding body and the surface scraping material.Based on contact mechanics,elastic-plastic mechanics and geotechnical mechanics,this paper puts forward the calculation method of scraping variable of surface scraping layer under additional impact load,and considers that vertical impact and tangential shear are two main action modes in the process of sliding mass impact and scraping effect.Combined with the actual material parameters of rock and soil mass,this paper finds that the plastic zone of the scraping layer is mainly the vertical fracture zone without considering the tangential load.However,when the tangential load is considered,the plastic zone of the scraping layer migrates along the tangential direction until the plastic boundary penetrates to the surface,which conforms to the actual situation and realizes the quantitative calculation of the scraping variable.