高土石坝动力弹塑性与黏弹性分析方法比较研究

Study on dynamic elastoplastic and viscoelastic analysis methods for high earth-rock dams

为了研究黏弹性方法和弹塑性方法用于分析土石坝动力性状时存在的结果差异,分别以沈珠江动力模型和静、动统一的广义塑性模型为例,同等条件下对比研究2种方法在加速度反应、坝体位移历史、震后残余变形、防渗体应力等方面的差异。研究结果表明:(1)弹塑性方法得到的坝顶区加速度放大系数较黏弹性方法略小,但中下部坝体加速度放大效应更强;(2)由于黏弹性方法坝体位移过程不包含地震残余分量,所以与弹塑性方法计算结果存在较大差异;(3)黏弹性方法采用经验公式估算的坝体残余变形规律与弹塑性方法结果较为一致,但弹塑性方法计算的坝体震缩现象与实际震害更为吻合;(4)黏弹性方法计算的面板破坏型式主要为面板顶部区域的拉伸破坏,而弹塑性方法的计算结果为面板中部区域的受压破坏,这主要是由于黏弹性方法未包含地震残余位移分量导致,其计算的面板动应力失真,弹塑性方法可有效克服黏弹性方法的缺陷。

In order to study the difference between the equivalent viscoelastic method and the elastoplastic method in earth-rock dam dynamic analysis,the Shen?s dynamic model and the generalized plasticity model were compared in several aspects of acceleration response,dam displacement history,residual deformation and slab dynamic stress under the same condition.Results show that,compared with the viscoelastic method,the acceleration amplifications at the top and at the lower middle of the dam calculated by the elastoplastic method are respectively slightly smaller and larger.Because the residual displacement is not considered in the viscoelastic method,the calculation displacement history is largely different from that obtained by the elastoplastic method.The residual deformation calculated by the viscoelastic method is rather consistent with the elastoplastic method,but the dam shrinkage evaluated by the elastoplastic method is more identical to actual earthquake damage.Calculation results by the viscoelastic method show that tensile failure will occur at the top part of the slab during the earthquake,but the results by the elastoplastic method reveal that compressive failure will occur at the middle of the slab.The main reason is that the viscoelastic method does not include the residual displacement component which results in the dynamic stress of the slab distorted.It is indicated that the elastoplastic method can effectively overcome the defects of the viscoelastic method.