地震动参数对地裂缝场地动力响应的影响规律研究

Study on the effects of ground motion parameters on the dynamic response of the ground fissures site

为系统地研究地震动参数对地裂缝场地土体动力响应的影响规律,探究动力放大系数在地裂缝场地土体内部的分布规律,以西安地裂缝为研究对象,开展了地裂缝场地土体振动台物理模型试验和数值模拟分析。研究结果表明:加速度和Arias强度放大系数从模型土底部到顶部逐渐增大,地表放大系数远大于土体底部的;在单向或者多向地震作用下,地裂缝场地上、下盘有不同的动力响应规律,表现出上下盘效应和非一致性,上盘的动力响应更剧烈,影响范围更大;随着地震动强度的增大,上、下盘的动力放大效应均呈减弱趋势,同时上、下两盘的数值差异逐渐减小,上下盘效应也不再显著;地震波输入方向、频谱特性以及强震持时均对地裂缝场地的动力响应有很大影响,但影响规律和程度不尽相同。

To investigate the effects of ground motion parameters on the dynamic response of the ground fissures site during strong earthquakes and to explore the distribution law of dynamic amplification factors in the soil of ground fissures site,a series of shaking table tests and numerical simulations were conducted based on the ground fissures site in Xi′an.The results showed that the acceleration and Arias intensity amplification factors increased with the buried depth,and the factors of ground surface were much greater than those at the bottom of the soil.Under the unidirectional and multidirectional earthquakes,the dynamic response of the ground fissures site had different dynamic response laws,showing"hanging-wall and footwall effect"and inconsistency.The dynamic response of the hanging-wall was more intense and the influence range was larger.With the increase of the horizontal seismic intensity,the dynamic amplification factors of the hanging-wall and footwall decreased.Besides,the discrepancies of dynamic response between the hanging-wall and footwall decreased significantly,which means that the"hanging-wall and footwall effect"is no longer significant.The input direction,spectrum characteristics and strong ground motion duration of seismic wave all had a great influence on the dynamic response of ground fissures site,but both the influence law and degree are different.