扩大基础和垫座对高拱坝地震动响应的影响研究

Influence of expanded foundation and cushion on ground motion response of high arch dams

中国的高拱坝多位于西南部地震多发且地形地质条件复杂的地区,在地震作用下极易造成坝体局部开裂和整体失稳。以金沙江下游白鹤滩拱坝为研究对象,探讨扩大基础和垫座对坝顶和拱冠梁最大位移、横缝开度、坝体损伤体积比等地震动响应的影响特点。分析结果表明扩大基础和垫座具有如下优点:使拱坝左右两侧的体型更趋于对称,对减小坝顶和拱冠梁的位移响应有利。以增大边缝开度为代价而使坝体中部横缝开度显著减小,且使横缝张开趋于均匀,对充分发挥止水片密封效果有利;能够明显减小坝体的损伤体积比;其中,扩大基础对坝体位移和损伤体积比的减弱效果明显优于垫座。但是,随着地震动强度增加,扩大基础和垫座对位移响应约束能力逐渐减弱。研究结果证明了扩大基础和垫座对增强拱坝抗震能力的有效性,可为类似高拱坝工程建设提供有益参考。

Most of the high arch dams in China are located in the southwest region where earthquakes occur frequently and the topographical and geological conditions are complex.Under earthquake action,the dam body is very prone to local cracking and even overall instability.Taking the Baihetan arch dam located in the lower reaches of Jinsha River as the research object,we discussed the influence of expanded foundation and cushion on the seismic responses such as maximum displacement of dam crest and crown cantilever,transverse joints'opening,dam damage volume ratio.The results showed that expanded foundation and cushion made the shape of the arch dam more symmetrical,which was beneficial to reducing the displacement response of the dam crest and crown cantilever.At the cost of increasing the transverse joints'opening on both sides,the transverse joints'opening in the middle of the dam body was significantly reduced,and all of the transverse joints'opening tended to be uniform,which was beneficial to give full play to the sealing effect of the waterstop;it can obviously reduce the damage volume ratio of the dam body.The effect of expanded foundation on reducing dam displacement and damage volume ratio is obviously better than the cushion.However,with the increase of ground motion intensity,the restraint capacity of expanded foundation and cushion to displacement response gradually weakens.This paper proves the effectiveness of expanded foundation and cushion in enhancing the seismic capacity of arch dams,which can provide useful reference for similar projects.