SV波作用下刚性挡土墙地震主动土压力时频域计算方法

TIME-FREQUENCY COMPUTATIONAL METHOD OF SEISMIC ACTIVE EARTH PRESSURE OF RIGID RETAINING WALL SUBJECTED TO SV WAVE

基于弹性波动理论,概化刚性挡土墙的动力分析模型,利用水平分层法,建立单元体的受力平衡微分方程,借助Hilbert-Huang变换,提出地震作用下刚性挡土墙地震主动土压力的时频域计算方法,并通过与振动台试验结果的对比验证该方法的合理性。分析输入波频率对刚性挡土墙墙后填土的临界破裂角、地震主动土压力合力以及作用点的影响,结果表明:随着地震烈度的增大,临界破裂角逐渐减小,地震主动土压力合力逐渐增大,合力作用点位置略有上移;随着输入波频率的增大,临界破裂角和地震主动土压力合力分别呈"倒马鞍型"和"正马鞍形"分布,并且均在输入波频率与刚性挡土墙系统自振频率相近时达到最大,而地震主动土压力合力的作用点则基本上不变;按照现有规范不考虑输入波频率进行刚性挡土墙地震稳定性设计,可能会降低挡墙的地震安全储备。刚性挡土墙地震主动土压力的时频域计算方法不仅能够考虑地震波三要素(峰值、频率以及持时)对挡墙土压力的影响,同时也能够为其他类型支挡结构的抗震时频设计提供一定的参考。

Based on the elastic wave theory,summarizing the dynamic analysis model of rigid retaining wall,the first-order differential equation of the differential volume element is established by horizontal slices analysis method. And then,a time-frequency analysis method of seismic active earth pressure of rigid retaining wall is proposed. The reasonability of this method is verified by the results of shaking table test. The frequency of seismic wave has an predominate effect on critical rupture angle of filling earth,the resultant force of the seismic active earth pressure and the application point of resultant. The results are as follows. With the increase of the peak ground acceleration（PGA）,the critical rupture angle of filling earth decreases,the resultant force of seismic active earth pressure increases,and the application point of the resultant is gradually move up;with the increase of the frequency of input wave,the critical rupture angle and the resultant force of seismic active earth pressure are distributed in the shape of saddle and the handstand saddle;and they achieve the maximum value when the frequency of input wave is the same as the natural frequency of rigid retaining wall;but the application point essentially is unchanged;if the rigid retaining wall is designed according to the rules,the emergency capacity of rigid retaining wall will be reduced. At last,this method not only considers the effect of three factors of the seismic wave（PGA,frequency and duration） on the seismic earth pressure of reinforced retaining wall;but also provides some valuable references for the time frequency seismic design of the other retaining structures.