泥石流块石冲击下新型钢管混凝土桩林坝“品”单元动力响应分析

Dynamic response analysis of “trefoil”-shap unit of concrete-filled steel tubular piles under impact of big stone in debris flow

泥石流所含块石的冲击是造成拦挡结构破坏的主要因素。钢管混凝土桩林能够有效拦截泥石流块石,减轻它的破坏作用。选取了钢管混凝土桩林的典型"品"字形三桩结构单元,利用ANSYS/LS-DYNA软件对其两个典型部位进行了块石冲击下的动力响应模拟和分析。结果表明:三桩结构不同部位的冲击力时程曲线呈现出显著差异,受冲击部位的约束越强,即局部刚度越强,则冲击力峰值越大,且冲击力峰值随着冲击速度、混凝土强度等级以及桩截面套箍系数的增大而增大,而三桩结构顶部节点处冲击力峰值随着桩心距的增大而减小;受冲击部位背面的残余变形与冲击速度近似成二次关系,与冲击能量成线性关系;结构的受冲击部位、支座部位以及桩梁连接处的响应较大,设计时应予以加强。

The impact of big stone in debris flow is often the major factor for the block structure damage. As a new block structure,the concrete-filled steel tubular piles can intercept stone effectively so as to reduce the impact damage of debris flow. Based on the finite element program ANSYS / LS-DYNA,the model of the typical ＂trefoil＂-shaped unit of concrete-filled steel tubular piles is established,and the dynamic response of its two positions is simulated and analyzed under the impact of stones. Results show that the impact force time curves of different positions have obvious differences,if the stronger the constrain of impacted position,namely the local stiffness is,the larger the peak impact force is,and the peak impact force increases with the velocity,concrete strength grade or confinement index improved,but decreases with the distance of pile center added. The residual deformation of impacted position back is similar to the impact energy and square of velocity. The impacted position,bearing positions and pile-beam connections have big response under impact load,and they should be strengthened when designed.