高地震烈度区水电站地下厂房结构震损机理分析

中国水电站多位于西南高地震区.针对地下厂房结构的震损机理问题,以距汶川8.0级地震震中最近的映秀湾水电站和渔子溪水电站为分析对象,对水电站建筑物进行了震后实地调查,建立了映秀湾水电站洞周围岩和厂房结构的整体有限元模型,采用波动场应力法,对地下厂房结构在震时的结构稳定性进行了计算分析.根据实地调查结论和数值计算成果,对地下厂房结构的震损机理进行分析.实地震损调查表明,地下结构的震损形式多为表层脱落和闭合裂缝,破坏程度要明显轻于地面建筑.数值计算所反映的震损规律与实际调查中得到的结论基本吻合,则可从数值分析的角度进一步研究震损机理,认为产生震损的外因是沿一定角度入射的地震波,内因是地下厂房结构空间分布的不均匀性,而地下厂房结构赋存于洞周岩体则是地下结构震损与地面建筑具有本质区别的原因.

Analysis of seismic damage mechanism of underground powerhouse structures of hydropower plants in high seismic intensity region

The hydropower plants in China are mostly located in southwest region where the seismic intensity is high. Aiming at the issue of seismic damage mechanism of underground powerhouse, Yingxiuwan and Yuzixi hydropower plants which were nearest to the epicenter of Wenchuan M8.0 earthquake were taken as the objects of analysis. Firstly, the post-earthquake in-situ investigation was conducted on the structures of the two hydropower plants. Then, the finite element mesh, which simulated both surrounding rock and powerhouse structures of Yingxiuwan plant, was established. The wave field method was employed to perform numerical calculation on the structural stability of underground caverns under seismic effect. Finally, based on the numerical results and in-situ investigation conclusions, the seismic damage mechanism of underground powerhouse structures was expounded. The in-situ investigation results showed that the seismic damages of underground structures were mostly surface shedding and closed cracks. The damage degree of underground structures was much smaller than that of ground structures. The seismic damage laws revealed by numerical calculation basically agreed with the investigation findings. This indicated that the seismic damage mechanism could be analyzed by using numerical results. It was therefore concluded that the incident angle of seismic wave was the external cause of seismic damage; the nonuniformity of spatial distribution of powerhouse concrete was the internal cause; the existence of rock mass surrounding the underground powerhouse accounted for the fundamental difference between underground and ground seismic damages.