饱和层状沉积河谷非线性随机地震响应与空间多点地震动模拟研究

In view of the significant influence of sedimentary valleys on earthquake ground motion and the non-linearity of sedimentary soils under strong earthquakes, and a large number of towns and important engineering structures (dams, bridges, etc.) at home and abroad are located in the valley site, it is necessary to scientifically reveal the sedimentary valley non-linear amplification effect and its internal spatial variation of ground motion characteristics. To this end, the basic law of sedimentary valley nonlinear seismic response by random wave analysis is researched in the project for non-linear random seismic response of saturated layered alluvial valleys, by considering the seismic wave scattering effect, coherent effect and traveling wave effect and using the coupling method of finite element method with indirect boundary integral equation of saturated two-phase media, equivalent linear method with frequency correlation and Monte Carlo method. Base on a large number of parameter analysis, the effect of geometry and material properties randomness on the valley vibration amplification and internal spatial variation are revealed. A reasonable and reliable spatial correlation multi-point ground motion simulation method is studied by considering the site nonlinearity, scattering effect, coherence effect and traveling wave effect. The project can provide reliable ground motion parameters for seismic fortification of large-scale engineering structure in complex valley and scientific basis for seismic zoning and seismic safety evaluation. The work has important scientific significance and significant social value.

鉴于沉积河谷对地震动的显著影响且沉积土在强震作用下非线性不容忽视，而国内外有大量城镇及重要工程结构（大坝、桥梁等）位于河谷场地之中，因此亟需对沉积河谷非线性地震动放大效应及其内部地震动空间变化特征予以科学揭示。项目针对饱和层状沉积河谷非线性随机地震响应，采用饱和两相介质有限元-间接边界积分方程耦合法、频率相关的等效线性化法及蒙特卡罗方法，从随机波动角度研究饱和层状沉积河谷非线性地震响应基本规律；通过大量参数分析，揭示河谷几何及材料特性随机性对河谷非线性地震动放大效应的影响规律和沉积内部地震动空间变化特征；综合考虑场地非线性、地震波散射效应、相干效应及行波效应，研究一种合理可靠的空间相关多点地震动模拟方法。项目可为实际复杂河谷场地大型工程结构抗震设防提供可靠的地震动参数，为地震小区划、地震安全性评价等工作提供科学依据，具有重要科学意义。

国内外有大量城镇及重要工程结构（大坝、桥梁等）位于沉积河谷场地之中，而河谷对地震动具有显著影响且沉积土的饱和特性和在强震作用下的非线性不容忽视。为科学评估沉积河谷非线性地震动放大效应和揭示其内部地震动空间变化特征，系统开展了饱和沉积河谷非线性随机地震响应研究。结合Biot饱和理论和有限元-间接边界元（FEM-IBEM）耦合方法，实现饱和沉积河谷非线性动力响应计算；针对复杂场地多点地震动构造难题，结合合理的相干函数和谱密度函数，基于谱表示法提出一种非线性沉积河谷空间相关多点地震动模拟方法并进行验证。利用蒙特卡罗方法随机模拟产生饱和沉积河谷介质样本和断面形状样本，计算在随机输入下不同样本情况河谷地震响应；通过对大量随机结果的统计分析，揭示了饱和沉积河谷介质随机性和断面形状随机性对河谷地震动放大效应的影响规律。进行了随机边界下的饱和沉积河谷场地的地震动模拟，将计算反应谱与设计反应谱对比，验证了模拟方法的准确性和有效性；综合利用计算反应谱的谱值、平台值和特征周期，研究了考虑边界随机性的沉积谷地模拟地震动影响。发展了一种考虑场地条件的反应谱估计插值方法。研究成果可为复杂场地空间多点地震动模拟提供新的思路和方法，为沉积河谷区域地震区划、城市规划、建筑抗震设防及安全评估等提供理论依据。项目迄今已发表重要期刊论文5篇，其中SCI检索4篇，EI检索1篇。培养硕士生3名。