强震作用下黄土液化及强度衰减对斜坡失稳的致灾机理

Based on the analysis of loess seismic liquefaction and triggered landslide related collection and investigation data, the formation conditions and the basic characteristics of landslide triggered by loess seismic should be proposed. The dynamic triaxial test under random seismic loading should be carried out to expound the pore water pressure, modulus and strength of loess affected by change of factors, to determine losses liquefaction starting conditions of single factor, and establish loess pore water pressure growth model, constitutive equation and strength attenuation model of loess under random earthquake loads. chosen the typical seismic landslide triggered by loess liquefaction as an example, using the established model to study its dynamic response and stability, and comparatively analysis with conventional calculation result and the actual of landslide, the mechanism of loess liquefaction and strength attenuation contribution on the land failure of slope would be acquired.

通过对黄土地震液化及液化引发斜坡失稳的相关资料收集和现场调研，提出液化型黄土地震滑坡的形成条件和基本特征。开展随机地震荷载作用下黄土的动三轴试验，阐明单因子变化对黄土孔压、模量、强度的影响效应，确定黄土的单因子液化起始条件，建立随机地震荷载作用下黄土的孔压增长模型、本构模量和强度衰减模型。选取典型的液化型黄土地震滑坡作为案例，根据已建立模型进行动力响应和动力稳定性研究，将研究结果与常规计算结果和滑坡实际对比分析，揭示黄土液化和强度衰减对斜坡地震失稳的致灾机理。

本项目对1920年海源地震诱发的黄土滑坡开展了大量的现场调研工作，总结了这些地震滑坡的分布规律、几何特征、地层岩性、破坏方式、运动特征等， 并系统总结了液化型黄土地震滑坡的基本特征。根据汶川地震和高陵地震的地震动记录，分析地震动的频谱衰减规律，结合海原地震的烈度分布特征，获得了海原地震强震区的地震动频谱特征。开展随机地震荷载作用下黄土的动三轴试验，研究随机地震荷载作用下黄土的孔压变化规律和黄土试样在p-q平面上破坏面的发展变化轨迹，得到了地震荷载作用下黄土的孔压增长应变模型和强度衰减规律。开展黄土边坡的物理模型试验和数值模拟工作，研究了黄土边坡的强度理论效应和强度理论参数的取值范围。基于黄土液化和强度衰减的相关认识，对夏家大路典型黄土地震滑坡开展稳定性分析，揭示了强震作用下黄土边坡的液化失稳机制。