主-余震序列作用下隧道结构增量损伤研究

Research on Incremental Damages of Tunnel Structures Subjected to Seismic Loadings with Mainshock-aftershock Sequences

强震作用后通常伴随多次余震,而余震作用可能会进一步加剧结构损坏或倒塌的风险。以强震区不同地层条件下的隧道结构为对象,对比分析了主-余震序列作用下软土地层和岩石地层中隧道结构非线性动力响应的差异性,并基于定义的余震地震动强度指标,探究了余震对隧道结构增量损伤的影响规律。首先,从COSMOS强震数据库中选取了6组真实的主余震序列记录,选定5个主震-余震峰值加速度的比值作为控制指标,从而构建了30条主震-余震序列作为输入地震动;其次,建立了地层-结构有限元动力分析模型,分别对软土和岩石地层中的隧道结构开展非线性动力时程分析,依据定义的隧道衬砌损伤体积比指标,计算得到了主震-余震序列作用下隧道结构的增量损伤指数;最后,分析了不同地层条件对隧道结构增量损伤的影响规律,并讨论了地表峰值加速度(PGA)和Arias强度(Ia)与余震引起的结构增量损伤之间的相关性。结果表明:余震引起的增量损伤随着主余震相对强度比的增大而增大;当地层条件分别为软土和岩石地层而隧道结构形式不变时,软土地层中的隧道结构在主震-余震序列作用下的增量损伤会更大;余震引起的增量损伤与Ia的相关性比PGA更强,因此采用余震的Ia能够更好地预测隧道结构在余震作用下产生的损伤程度。

Tunnels can be further damaged in the aftershocks of a strong earthquake thereby increasing the risk of structural damage or collapse before repairs can be made.This study investigated the non-linear dynamic response and incremental damage of a circular tunnel in soft soil and rocky stratum under the effect of main aftershocks.Six sets of real mainshock-aftershock sequences were selected from COSMOS Virtual Data Center.Additionally,30 main aftershock sequences were constructed by adjusting the amplitude based on the peak acceleration of main shock and mainshock-aftershock peak ground acceleration ratio.Two-dimensional finite element models were established to analyze the nonlinear dynamic time history of tunnels in soft soil and rock.The global damage evaluation index of the structure was determined by the lining damage volume ratio,and the correlation between the mainshock-aftershock intensity ratio and incremental damage caused by aftershocks was analyzed.Both peak ground acceleration and Arias intensity were used as the mainshock and aftershock intensity parameters.The results indicate that the magnitude of incremental damage caused by the aftershocks increase with relative strength ratio of the main aftershock.The incremental damage of the tunnel in soft soil under the main-aftershock sequence is greater than that of the tunnel in rock stratum.The correlation between the Arias intensity and incremental damage of the aftershock is higher than PGA,and the Arias intensity of aftershocks can well predict the structural damage caused by the aftershocks.