多地形地貌单元复合场地三维地震动模拟研究

The earthquake ground motion simulation of complex site is an important research topic, possessing a clear engineering application background. However, systematic and thorough research is desperately needed on the multi-geomorphic composite site which is more realistic in the engineering practice. Considering this key scientific issue, the project first develops an indirect boundary element method (IBEM) for seismic wave field simulation of the three-dimensional (3D) layered half-space with multiple domains, based on the single-layer potential theory and Huygens principle, and by fully exploring the advantages of the full-space and half-space Green's functions in constructing the scattering wave fields in closed and open half-space domains, respectively. Then, aiming at the three typical composite sites including the basin-mountain coupled site, mountain-valley coupled site and multi-mountain site, study on the regulations and mechanisms of the 3D seismic response of the three composite sites is performed. By taking the Weihe River Basin coupled with the Ordos plateau and Qinling Mountains on its two sides as example, study on the prediction of the earthquake ground motion of the realistic composite site is also carried out. Through the detailed parametric analysis, the project reveals the mechanism of seismic interaction among topographical units and the compound effects on the seismic ground motions, clarifies the influence law of adjacent topographies on ground motion parameters as well as their spatial distribution characteristics, and quantitatively evaluates the differences of seismic response between the different kinds of composite sites and their corresponding single topographical sites. The research provides a new method for solving elastic wave propagating problems in a multi-domain half-space, and offers a theoretical basis for the seismic design of important engineering structures, seismic zoning, urban planning and other related works in the multi-geomorphic composite site.

复杂场地地震动模拟是重要的研究课题，有着明确的工程应用背景，然而目前在更为符合实际的多地形地貌单元复合场地方面尚需深入系统研究。针对这一关键科学问题，项目首先基于单层位势理论和惠更斯原理，充分发挥全空间和层状半空间格林函数在分别构造闭合域和开口半空间域内散射波场方面优势，发展一种三维层状半空间中多域地震波场模拟的间接边界元方法。进而针对盆山耦合、高山峡谷和群山三种典型复合场地开展三维地震反应的规律机理研究，并以渭河盆地及两侧鄂尔多斯台地和秦岭山脉实际场地为例进行地震动的模拟预测研究。通过详细参数分析，揭示地形单元间的地震相互作用机理及其对地震动的复合影响，阐明相邻地形对地震动参数及其空间分布特征的影响规律，定量评估各类复合场地与相应单一地形场地地震反应的差异。研究成果可为半空间多域弹性波动问题求解提供新的思路方法，为地形地貌复杂区域的重大工程抗震设防、地震区划和震害预测等工作提供理论依据。

复杂场地地震动模拟是重要的研究课题，有着明确的工程应用背景，然而目前在更为符合实际的多地形地貌单元复合场地方面尚需深入系统研究。选取典型复合场地（盆山耦合、高山峡谷和群山场地等）以及实际复合场地为研究对象，系统深入地开展多地形地貌单元复合场地地震动模拟研究，具有重要的理论意义和工程应用价值。.基于以上研究背景，项目首先建立了一套以均布荷载动力格林函数为基本解的多域间接边界元方法（Multi-domain IBEM），进而系统深入地开展了多地形地貌单元复合场地地震动模拟研究。取得的研究成果包括，基于层状弹性（饱和）半空间精确动力刚度矩阵，推导了层状弹性（饱和）半空间中系列埋置均布荷载动力格林函数；进而基于单层位势理论和惠更斯原理，借助推导出的半空间动力函数和经典的全空间动力格林函数，充分发挥两者在分别构造闭合域和开口半空间域内散射波场方面优势，建立了层状弹性（饱和）半空间中多域地震波场模拟的2D、2.5D和3D Multi-domain IBEM；进而以典型复合场地（盆山耦合、高山峡谷和群山复合场地）为研究对象，系统研究了复合场地对地震波散射的频域和时域解答。.研究结论包括：相邻地形之间存在显著的动力相互作用，对波的散射有着明显的影响；盆山耦合地形周围山体的存在会对斜入射地震波产生“屏障效应”，山体的遮挡效果与山体的高度和入射波的频率有关，山体越高或者入射波频率越低，遮挡效果越明显；球面波作用下，沉积盆地和凸起山体内部会聚集大量地震能量，在盆地和山体内部和地表形成明显的局部“聚焦效应”。项目力求揭示多地形地貌单元复合场地对入射地震波的散射机理，评估各类复合场地与单一地形场地地震反应的差异，确定复杂地形对地震动参数及其空间分布特征的影响规律。项目研究成果可以为地形地貌复杂地区重大工程抗震设计、地震危险性分析、地震区划等工作提供部分理论依据，具有一定的科学意义和社会效益。