地震作用下地裂缝场地地震动参数试验研究

为研究地裂缝场地地表动力响应规律，以西安f4地裂缝场地为工程背景，采用剪切型模型箱，进行振动台模型试验。分析了地裂缝场地在地震作用下的破坏特征和动力响应，得到了地表地震动参数变化规律。试验结果表明：地震作用下，地裂缝场地的主裂缝在地表开裂、扩展，并在裂缝区产生与其45°相交的次生裂缝，次生裂缝的数量随着地震强度增大而增多；地表地震动参数峰值均表现出上、下盘效应，均在上盘裂缝处最大，逐渐向两侧递减；随着输入地震强度增大，地表加速度及Arias强度放大系数逐渐减小；上盘加速度变化频率较快，且上、下盘两侧加速度峰值存在相位差，但两侧位移及速度时程波形基本一致。该研究成果可为跨地裂缝结构抗震设计提供重要参考。

Model test on ground motion parameters of site with fissures under seismic loading

In order to study the dynamic response of ground fissure sites, based on a 13-layer shear model box, the shaking table test was used to simulate the dynamic response of the f4 ground fissure site in Xi’'an. The failure characteristics and dynamic response of the ground fissure site under different seismic waves were studied. The peak change laws of ground motion parameters were obtained. The test results showed that the main fissure gradually cracked and expanded on the surface, and the secondary fissures were developed at 45 degree joining the main fissure as the dynamic test continued. Moreover, the number of secondary fissures increased with the increase of input seismic intensity. The response of ground motion parameters at the ground fissure site had hanging-wall/ footwall effect. The ground motion peak of the hanging-wall reached the maximal value at the fissure on hanging-wall side and the peak gradually decreased from the main fissure to the two sides. Beyond that, the seismic intensity increasing weakened the site amplification effect. In addition, the changing frequency of acceleration at the hanging-wall site was faster than that at the footwall site. Meanwhile, there was a phase difference between the peak acceleration response on the hanging-wall and that on the footwall. However, the velocity and displacement time history curves of two sides were basically consistent. The research results are an important reference for seismic design of structure passing through the ground fissures.