基于多目标优化的黏土心墙坝变形协调分析

Deformation compatibility analysis of clay core wall dams based on multi-objective optimization theory

为了研究黏土心墙坝的变形协调性质,提出了大主应力、心墙应力水平、坝体最大沉降、心墙沉降变化率和振动密实时间这5个参数作为评价指标,并以某黏土心墙坝为例开展了三维有限元计算,结合所提出的评价指标和评价方法对坝体变形协调性质进行了具体分析,主要结论如下:(1)各评价指标与坝壳料相对密度D_r之间存在显著的函数关系,对各函数进行归一化处理可得到各指标的功效函数,设定各功效函数的权重,通过加权平均的方法得到评价最优坝壳料D_r的目标函数;(2)不考虑施工成本时,通过各单个指标所确定的最优坝壳料D_r差异较大,范围为0.49~1.0;基于多目标最优化目标函数确定的最优坝壳料D_r范围为0.78~0.81,较为合理且满足设计规范;(3)384 m高程考虑施工成本时,若采用等权重分配方案,最优坝壳料相对密度D_r为0.783,需振动历时90 s。所提出的多目标优化分析方法对坝体建造有指导意义。

This paper describes five indexes for evaluating the deformation compatibility of clay core wall dams,i.e.,major principal stress,stress level of core wall,maximum settlement of dam body,settlement rate of core wall,and vibration time for compaction.We use these indexes and 3D finite element analysis to examine the deformation compatibility of a core rockfill dam,and come to the conclusions as follows:(1)Functional relationship between each index and the relative density D_r of dam shell material can be summarized by a fitted equation;For each index,an effect function can be obtained using a normalization method.An objective function is obtained by assigning a weight factor to each effect function,and the weighted average value can be used to determine D_r of the optimal dam shell material.(2)Without construction cost taken into account,the D_r obtained by each single index may vary greatly in a wide range of 0.49 to 1.0,while it is reduced to 0.78-0.81 if determined using multi-objective optimization,a reasonable range that meets the design specification.(3)With construction cost considered for a construction elevation of 384 m,D_r of 0.783 is determined for an equal-weight scheme requiring a vibration duration of 90 s.The multi-objective optimization method is beneficial for dam construction.