考虑堆石料空间变异性的土石坝地震反应随机有限元分析

探讨了一种将随机场模拟技术与有限元方法相结合的随机有限元法在土石坝地震反应分析中的应用途径。采用局部平均细分法模拟堆石料物理力学性质随机场,使得能够考虑堆石料的空间变异性。提出尽量利用建立材料物理性质与力学性质关系的计算模型,以降低获取材料力学性质统计特性信息的成本。以一实际工程为例,采用该随机有限元法计算了堆石料的干密度、孔隙比、不均匀系数、平均粒径、Duncan–Chang E–B模型模量系数以及初始摩擦角具有不确定性时土石坝的随机地震响应及永久变形。结果表明:筑坝堆石料的不确定性会使大坝响应及永久变形发生一定程度的离散;忽略材料的不确定性可能导致低估大坝的地震反应;表征大坝地震反应的各性能指标并不一定都符合正态或对数正态分布。

Seismic response of rockfill dams considering spatial variability of rockfill materials via random finite element method

The random finite element method (RFEM), which incorporates simulation techniques of random fields with the finite element method, is proposed to analyze the seismic response of rockfill dams. In order to consider the spatial variability of dam materials, a Local Averaged Subdivision method is used to simulate the random physical and mechanical property fields. Moreover, to lower the cost of obtaining statistical information of mechanical properties of materials, it is suggested to adopt constitutive equations which connect mechanical properties with physical ones. Then, the random seismic response and deformation of a real rockfill dam is simulated via RFEM, in which the dry density, void ratio, median grain size, uniformity coefficient, initial internal friction angle and shear modulus coefficient of the rockfill materials are modelled as random fields. The simulated results show that: (1) The randomness of dam materials will induce unneglectable dispersion in the performance of dams; (2) It is very likely that the response of dams will be underestimated if the randomness of dam materials is overlooked; (3) Some dynamic performance indicators may follow neither the normal nor the lognormal distribution.