基于速度脉冲地震动的边坡地震位移统一预测模型

Empirical predictive model for seismic displacement of slopes under velocity pulse-like ground motions

采用基于小波变换的多向地震动速度脉冲特性鉴定方法,从NGA数据库及汶川地震动记录中提取出了196条速度脉冲地震动数据;基于Newmark非耦合滑动模型,考虑土体非线性特征。通过计算速度脉冲地震动作用下不同强度(ky)及初始自振周期(Ts)边坡模型的地震位移,对比分析了边坡地震位移与速度脉冲地震动参数之间的相关性,并建立了适用于近断层速度脉冲地震动的边坡地震位移统一预测模型。结果表明:既有边坡地震位移预测模型低估了近断层速度脉冲地震动引起的位移值,而用于预测近断层非脉冲地震动引起的边坡地震位移离散较小;近断层速度脉冲地震动引起的边坡地震位移与其速度脉冲特性密切相关,地震位移与速度脉冲地震动参数(峰值速度PGV)相关性最好;采用1.5倍边坡自振周期对应的加速度反应谱(Sa(1.5Ts))和PGV分别代表速度脉冲地震动的频谱成分及速度脉冲特征,能够综合反映速度脉冲地震动对边坡地震位移的影响;建立了基于边坡参数(ky,Ts)和脉冲地震动参数(PGV,Sa(1.5Ts))的边坡地震位移预测模型,为考虑近断层地震动速度脉冲特性影响的边坡地震位移概率灾害分析提供了基础。

Based on the procedure to identify the velocity pulse for multi-component ground motions, 196 ground motions from NGA database and Wenchuan Earthquake are selected as pulse-like ground motions. The newmark decoupled model considering the nonlinear properties of soils is used to calculate the seismic displacement of slopes with different parameters （ky, Ts） subjected to near-fault pulse-like ground motions, and the efficiency of different pulse-like ground motion parameters for predicting the displacement is also investigated. A seismic displacement model for the slopes under near-fault pulse-like ground motions is developed. The results indicate that the existing empirical models for seismic displacement of slopes significantly underestimate the displacement value induced by near-fault pulse-like ground motions, while they can be used to predict the seismic displacement caused by near-fault non-pulse ground motions. A close relationship between the seismic displacement and the velocity pulse characteristics for the pulse-like ground motions is shown, and the peak ground velocity （PGV） is the most efficient parameter in terms of the seismic displacement. The spectral acceleration at a degrade period equals to 1.STs （Sa（l.5Ts）） and PGV can represent the frequency content and velocity pulse characteristics of the pulse-like ground motions, respectively. Thus, an empirical predictive model for seismic displacements is developed using the vector intensity measures of Sa（1.5Ts） and PGV, which can be used in probabilistic seismic hazard analysis for the seismic displacement including the effects ofnear-fault pulse-like characteristics.