考虑级配参数空间变异性的堆石坝随机有限元分析

Stochastic Finite Element Analysis of Rockfill Dam Considering Spatial Variability of Gradation Parameters

为研究堆石料级配参数的空间变异性对堆石坝坝体有限元计算结果的影响,以某面板堆石坝工程为例,结合施工填筑检测资料,基于Cholesky分解法实现堆石料分形维数的对数正态随机场模拟,结合考虑级配效应的堆石坝有限元分析方法对坝体力学响应进行研究,并与坝料分区采用单一级配假定的确定性有限元计算结果进行比较。结果表明:堆石料级配曲线基本满足分形分布,分形维数D可较好地表征堆石料级配特性。当随机模拟至200次时,坝体各响应值达到统计稳定,且堆石料级配的分形维数满足对数正态分布时,计算出的坝体应力变形基本满足正态分布。与坝料各分区参数采用单一级配假定的确定性有限元相比,随机性有限元的变形和应力均偏大,计算结果偏于安全,两者相对误差在2%~7%,如果不考虑堆石料级配参数的空间变异性,会在一定程度上低估坝体变形和应力。

In order to study the influence of spatial variability of rockfill gradation parameters on finite element calculation results of dam,taking a rockfill dam project as an example and combined with the construction and filling testing data,the log-normal random field simulation of the fractal dimension of rockfill material is realized based on the Cholesky decomposition method.The mechanical response of dam body is studied with the finite element analysis method of rockfill dam considering the gradation effect,and the calculation results are compared with the deterministic finite element calculation results assuming the dam material partition using a single gradation.The results show that:(a)the rockfill gradation curve basically satisfies the fractal distribution,and the fractal dimension D can better characterize the rockfill gradation characteristics;(b)when the random simulation reaches 200 times,each response value of dam body reaches statistical stability,and when the fractal dimension of rockfill gradation satisfies the log-normal distribution,the calculated stress and deformation of dam body basically satisfy the normal distribution;and(c)compared with the deterministic finite element that uses a single gradation assumption for the parameters of each partition of dam material,the deformation and stress of random finite element method are larger,and the relative error between the two methods is 2%-7%,that shows the calculation results of proposed method relatively safe.If the spatial variability of rockfill gradation parameters is not considered,the deformation and stress of dam body may be underestimated.