间断式横缝设计及其对大坝地震响应的影响

Design of discontinuous transverse joint and its effects on the seismic response of concrete dams

介绍强震区高碾压混凝土重力坝横缝的创新性设计及其对大坝地震响应的影响。为提高大坝的整体稳定性,对坝体每一碾压浇筑层,横缝的切缝深度仅切割2/3浇筑层厚度,并在切缝中填充无纺布,使横缝具有弱连接诱导缝的性质,达到既能满足温控要求,又可增强大坝的整体性。开发了反映横缝法向开合非线性和径向滑移动接触模型,采用非线性指数型动接触本构模型模拟了横缝的张开、闭合的非线性力学行为,运用摩尔库伦定律模拟了横缝的切向非线性特性。对在建的金安桥碾压混凝土重力坝3条横缝、10条横缝的情形分别进行了地震响应分析。结果表明,间断式横缝有效地提高了大坝的整体性,大坝横河向位移响应明显减小;金安桥大坝靠左右岸坝段的横缝的张开度明显大于中间坝段横缝的开度值,相应的张开-闭合频率也远高于中间坝段的横缝。所提设计方案已用于实际工程,实践表明具有较好的效果,可推广用于类似碾压混凝土大坝的施工设计。

An innovative design of transverse joint of high RCC gravity dam in high-intensity earthquake region and its effects on the seismic response of the dam are presented in the paper.To improve the whole stability of the dam,the cutting depth is only 2 /3 of the lift thickness for each rolled concrete layer,and the cutting joints are filled with non-woven fabrics so as to possess the features of weak-link induced joints.Thus,the transverse joints not only meet the temperature control requirements,but also improve the integrity of dam.A nonlinear exponential dynamic contact model of normal opening-closing and a nonlinear radial slide model based on Mohr-Coulomb law are developed for the contact of transverse joints.By using these models,a seismic analysis of the Jin-anqiao RCC gravity dam under construction is carried out for the schemes of 3 joints and 10 joints,respectively.The results show that the new design of transverse joints improves the dam integrity effectively and reduces the displacements in across river direction considerably.The joint openings near the left and right banks of this dam are considerably greater than that of the middle section;the corresponding opening-closing frequency is much higher than that of the middle section.The joint design has been adopted in practice,and the applications show a good effect of the proposed joints.It could be applied to the similar RCC dams.