水工隧洞混凝土衬砌地震动响应过程分析

Seismic Response Process Analysis of Concrete Lining in Hydraulic Tunnel

地震作用下水工隧洞混凝土衬砌结构的动态响应是工程设计和安全评估的重要内容,建立科学合理的混凝土动力本构模型以及内水与衬砌动力耦合作用分析方法是衬砌结构抗震研究的关键环节。基于应变空间静力损伤本构的基本思路,对3维应力状态下混凝土静态拉、压损伤变量进行定义和求解;在此基础上,考虑静、动态荷载作用下混凝土本构关系曲线的相似性特点,建立了适宜编程的混凝土动态损伤本构模型。基于单相固体介质和流体介质动力分析的显式有限元法,结合耦合界面的边界条件,建立了水工隧洞内水与衬砌耦合作用的动力显式有限元分析模型,该方法可以直接进行逐步积分,无需联立方程组求解,大大简化了计算过程,可以方便地用于分析多种介质的波动传播问题。针对某水电站引水隧洞工程进行了实例分析,计算结果表明:1)各部位混凝土衬砌处于同步震动状态,但腰拱部位位移明显小于顶拱和底拱部位;2)地震作用下混凝土衬砌迅速进入损伤开裂状态,腰拱部位衬砌应力增加明显,损伤破坏严重;3)开裂破坏区由腰拱逐渐向两端扩展,与内水直接作用的内层衬砌结构是抗震设计的薄弱环节。该模型能够合理地反映水工隧洞混凝土衬砌的地震动响应特性,并为水工隧洞抗震设计提供了一种有效的分析方法。

Dynamic response of concrete lining structure in hydraulic tunnel under seismic load is of great importance for engineering design and safety assessment,and it is the key link to establish a scientific and reasonable dynamic constitutive model and a coupling analysis method of inner water and lining for the seismic research of lining structure. In light of the basic idea of static damage constitutive in strain space,the static tension and compression damage variables for concrete under three-dimensional stress state were defined and solved. According to the similarity principle of constitutive relation curves of concrete under static and dynamic loading,a dynamic damage constitutive model of concrete suitable for programming was developed. Based on the explicit finite element method for analyzing the dynamic response of single-phase solid and fluid medium,combining with the boundary condition at coupling interface,a dynamic explicit finite element analysis model considering the coupling interaction of lining and inner water was presented. This method could directly integrate,solve without simultaneous equations,and greatly simplify the calculation process. Moreover,it could be easily used to analyze wave propagation problems with a variety of mediums. Taking some diversion tunnel as an engineering example,the calculation results show： 1） various parts of concrete lining are in a synchronous vibration state,but the displacement of haunch is obviously less than the vault and inverted arch; 2） the maximum principal stress quickly increases,and exceeds the tensile strength,in which the haunch is remarkably influenced,leading to great stress increment and serious damage; 3） the cracking zones gradually extend from the haunch to each side,and the inner lining directly interacting with fluid is the weak link of seismic design. This model could reasonably reflect the seismic response characteristics of concrete lining in hydraulic tunnel,and an effective analysis method was provided for the aseismic design of hydraulic tunnel.