基于修正邓肯-张模型的沥青混凝土坝体应力变形分析

Analysis of Stress and deformation of Dams Filled with Bituminous Concrete Based on a Modified Duncan-Chang Model

邓肯-张模型在平面应变状态和轴对称状态下的计算结果存在差异。为科学合理地评估沥青混凝土坝体在施工过程中的应力与变形规律,依据平面应变状态和轴对称状态下内摩擦角的参数转换关系,通过将轴对称状态的参数值修正为平面应力状态的参数值对邓肯-张模型进行修正,用修正后的模型进行分析。以沥青混凝土心墙坝为例,分析坝体心墙、过渡层和堆石区应力与变形在两种状态下的差异。结果表明,心墙大主应力沿高度方向分布呈底部剧降、中部缓降和顶部增大,靠近上下游侧的大小主应力分布特征相似,差异不显著;中心轴的主应力分布显著小于两侧,内部存在应力梯度,但未产生显著性的水平位移。在坝体中下部,平面应变的大主应力大于轴对称,前者的水平位移小于后者。在心墙坝填筑竣工后,心墙和过渡层大、小主应力变化较为剧烈,平面应变状态下计算出的主应力大于轴对称状态下计算出的主应力,在上下游堆石区内主应力变化较为平滑。

There is an inconsistency in the calculation results of the Duncan-Chang model under the conditions of plane strain and axial symmetry.To scientifically and reasonably investigate the rule of stress and deformation of dams filled with bituminous concrete in the process of construction,the Duncan-Chang model was modified by replacing the parameters under the condition of axial symmetry with those under the condition of plane strain,based on the conversion relationship of parameters of internal friction angles under those two conditions.With that modified model,this paper studied the dam with a bituminous concrete core,analyzing how different the stress and deformation of its core,transition layer and rock-fill zone were under the two conditions.It has been found that the max principal stress along the height of the dam shows a sharp decrease at the bottom,a slow decline in the middle,and an increase at the top,while the max and the min principal stresses near the upstream and downstream areas are similar to each other;the principal stress of the central axis is significantly smaller than that on both sides,and there is a stress gradient inside without noticeable horizontal displacement.In the middle and the lower parts of the dam,the max principal stress under the plane strain is larger than that under the axial symmetry,while the horizontal displacement of the former is smaller than that of the latter.When the bituminous concrete filling is completed,both the max and min principal stresses in the core and the transition layer show dramatic changes,with the principal stress obtained under plane strain being larger than that under axial symmetry.In addition,the principal stress of the rock-fill zone near the upstream and downstream changes steadily.