基于多点地震动输入条件下的土质边坡地震反应分析

地震工程中地震反应分析一般都假设研究目标与外部介质接触面各个点上地震动参数是完全一致的,即单点输入。但地震波能量、振幅等在传播过程中存在一定的衰减和散射现象,故边坡与外部介质接触面不同输入点上的运动不完全一致,在大尺度范围内考虑单点输入的情况与实际有一定的偏差,故需要进行多点输入方面的研究工作。以二维土质边坡模型为例,分别进行单点输入和多点输入,考虑其土层地震反应、塑性区分布、安全系数等特征,分析比较其异同,从而更好的为边坡抗震设计提供借鉴。结果表明,在土层地震反应分析方面,对同一监测点,多点输入下的加速度输出峰值、速度输出峰值均大于单点输入下的峰值,峰值出现的时间也早于单点;在塑性分布区方面,多点效应表现为发生了更明显的拉剪破坏现象;在安全系数方面,每一时刻多点输入下的安全系数均小于单点输入下的安全系数,相差约7%。综上所述,在大尺度范围内,考虑多点输入比单点输入更为合理和符合实际情况,故在抗震设计时应该考虑多点输入。

Analysis on the Seismic Response of Soil Slope Based on the Multi-point Ground Motion Input Method

In general, the seismic response analysis in earthquake engineering assumes that the vibration parameters at the interface between the target and the external media are exactly the same, that is, single point input. However, the seismic wave energy, amplitude attenuation and scattering phenomenon exist during seismic wave propagation, so the movements at different input points of the interface are not completely consistent. The single point input method in large scale has some deviation comparing with the reality. Thus, researches on multi point input are needed to cope with this condition. Taking a 2D soil slope model as an example, results between single input and multi input were compared. The similarities and differences of the seismic response of soil layer, plastic zone and safety factor between the two methods were analyzed in detail. Suggestions were put forward for reference in seismic design of slope. The results show that, in the aspect of soil seismic response analysis, the peak acceleration and velocity responses of multi-point input are both larger than those of single point input at the same monitoring point. The time to reach peak value is also shorter. A more obvious tensile-shear failure phenomenon was found for multi-point input according to plastic zone analysis. The factor of safety obtained by multi-point input is about 7% larger than that of single point input at each time. As mentioned above,seismic response analysis of slope considering multi-point input is more reasonable and practical in large scale. Therefore, multi-point input should be considered in earthquake resistance design.