有限高度海底流滑体冲击桩基的数值模拟

Numerical Simulation of Impact on Pile Foundations by Finite-Height Submarine Slide Mass

海底滑坡长距离流滑过程中,对桩基础的冲击会威胁上部结构的安全。用幂律流体表征流滑体的特性,在雷诺数为0.1~120范围内,采用有限体积法,在三维数值模型中模拟流滑体对桩基础的冲击。考虑流滑体自由表面和自重,推导了新的包含拖曳力项、承载力项和自重项的冲击力表达式,并分析了三项在对冲击力的影响,结果表明:流滑体高度与桩体直径的比值是影响自重项的主要因素,当桩径为0.5 m时,在比值大于20的范围内,流滑体自重对冲击力的影响可以忽略,可通过拖曳力与承载力项之和估算冲击力;在比值小于15的范围内,需考虑自重对冲击力的影响,当比值为4或5时,自重项的贡献最大,并给出了自重系数表达式。

In the process of long distance flow of submarine landslide,the impact on pile foundations will threaten the safety of upper structures.The slide mass formed after the landslide was described by the power law fluid with Reynolds numbers ranged from 0.1 to 120.The finite volume method was used to simulate the impact of slide mass on the pile with three dimensional model.Considering the effects of free surfaces and self-weight of the slide mass,the impact force expression was given,including the items of drag force,bearing capacity and self-weight.The results showed the ratio of the height of the slide mass to the pile diameter was the main factor affecting the self-weight item,while diameter of the pile was 0.5 m,in the range of the ratio larger than 20,the influence of self-weight could be ignored,impact forces could be predicted by the sum of the drag force and the bearing capacity,and the dimensionless coefficients were given;in the range of the ratio less than 15,self-weight should be considered with the expression of self-weight coefficients,and the contribution of self-weight was the largest while the ratio was 4 or 5.