结构缝对高碾压混凝土拱坝地震破坏机理影响的试验研究

为探究结构缝的存在对碾压混凝土拱坝地震破坏机理的影响,在地震模拟系统上进行了拱坝模型动力破坏试验。模型的建立基于弹性力-重力准则,不考虑库水以及坝体-地基相互作用。采用一种新型压电传感器测量模型内部的动态应力,并主动监测模型内部微裂纹的发生和发展过程。横缝的模拟考虑了键槽的影响,诱导缝的模拟基于断裂力学理论。选择模型基频对应的谐波逐级加载来研究拱坝在地震动超载作用下的反应。试验表明,拱坝顶拱的端部与拱冠的破坏均较严重,试验中横缝与诱导缝的先后张开分别释放了拱向端部应力与冠部应力,从而引导了裂纹开裂方向,减轻坝体破坏。通过实际震害与物理模拟的对比验证了试验结果的可靠性,显示本文的物理模拟技术有助于研究结构缝对拱坝地震破坏机理和最终失效模式的影响,可为碾压混凝土拱坝的抗震设计提供科学依据。

Experimental study of the impact of structural joints on seismic failure mechanism of large Roller Compacted Concrete arch dam

In order to study the impact of structural joints on failure mechanism of Roller Compacted Con-crete (RCC) arch dam, a dynamic rupture test was carried out on earthquake disaster simulation systems. The establishment of the model was based on elasticity-gravity similarity law, neglecting the reservoir and the dam-foundation interaction. A new kind of piezoelectric (PZT) sensors were set inside the model dam to measure the dynamic stress, detect the emergence and development of the micro cracks. The simulation of contraction joints took the effect of key grooves into consideration,while the simulation of induced joints was based on fracture mechanics. Sine waves corresponding to fundamental frequency loaded on the dam progressively to observe the responses of arch dam under overloading. The results showed severe damage on both ends of arch and the top of arch crown. The opening of contraction joints and induced joints released the stress on corresponding position, and then guided the development of cracks and mitigated the damage of the dam. The reliability of the dam was verified by actual earthquake hazard. The physical simulation technology is helpful to understand the effect of joints on seismic failure mechanism and provide some use-ful information for the seismic design of RCC arch dams.