强震过程非饱和黄土孔压响应规律及液化评判方法研究

Loess is characterized as water sensitivity and dynamic vulnerability. Hence, the liquefaction potential of the unsaturated loess during earthquake should be considered. Nevertheless, the study of dynamic liquefaction behavior of the unsaturated loess is limited. Hence, the Dangjiacha loess landslide induced by Haiyuan earthquake, China was chose in this study. First, the in-situ liquefaction features of the unsaturated loess were investigated. Then, typical loess samples were taken in the field for physical properties, mineral composition and microstructure analysis. Meanwhile, the unsaturated loess water retention tests and static triaxial tests were performed to analyze soil-water characteristics and critical states under different matric suction conditions. And then, the effects of void ratio, matric suction, consolidation stress, and dynamic loading type on sample liquefaction were studied by conducting the dynamic liquefaction tests on the unsaturated loess samples. Finally, from the physical progress and mechanical mechanism point of view, the response of loss microstructure vulnerability and pore pressure to strong earthquake was revealed. Meanwhile, the synergetic responses of soil-water-air on strong earthquake and the mechanical mechanism of liquefaction were analyzed. Additionally, a dynamic residual deformation model of unsaturated loess under vibration condition was proposed, and the criterion of liquefaction for unsaturated loess is put forward.These results could be used to the mitigation of earthquake-induced liquefaction hazards in the loess area.

黄土具有很强的水敏性和动力易损性，强震作用下高含水量黄土的液化问题不容忽视。然而，目前对于非饱和黄土动力液化特性的研究尚不够系统和深入。基于此，本项目首先以海原地震诱发的党家岔滑坡为地质原型，开展非饱和黄土动力液化的地质证据调查，选取典型黄土样品，在分析其物理性质、物质组成与微观结构特征的基础上，研究其水分特征曲线及不同基质吸力下临界状态特征；然后通过一系列非饱和黄土动三轴剪切试验，分析初始孔隙比、初始基质吸力、固结应力及动荷载类型等因素对动残余变形的影响规律；最后从非饱和黄土动力液化物理过程和力学机制的角度，揭示强震过程中非饱和黄土孔隙结构损伤、动残余变形、孔隙比及孔压变化规律，研究强震过程中固-水-气三相介质动力响应特性，建立振动条件下非饱和土的液化模型，提出适用于非饱和黄土的动力液化评判方法。项目研究成果对于黄土地区地震液化地质灾害防控具有重要意义。

黄土具有很强的水敏性和动力易损性，强震作用下高含水量黄土的液化问题不容忽视。然而，目前对于非饱和黄土动力液化特性的研究尚不够系统和深入。基于此，本项目首先以海原地震诱发的党家岔滑坡为地质原型，开展非饱和黄土动力液化的地质证据调查，选取典型黄土样品，在分析其物理性质、物质组成与微观结构特征的基础上，研究其水分特征曲线及不同基质吸力下临界状态特征；然后通过一系列非饱和黄土动三轴剪切试验，分析初始孔隙比、初始基质吸力、固结应力及动荷载类型等因素对动残余变形的影响规律；最后从非饱和黄土动力液化物理过程和力学机制的角度，揭示强震过程中非饱和黄土孔隙结构损伤、动残余变形、孔隙比及孔压变化规律，研究强震过程中固-水-气三相介质动力响应特性，通过对临界孔隙比增量 Δecyclic与动荷载产生的孔隙比 e0-eliq实际增量的比较，发现 Δeliq > e0-ecyclic时，黄土不可能流态化破坏，而Δeliq ≤ eo-ecyclic时，黄土发生流滑的可能性较高，基于Boyle-Charles定律建立了振动条件下非饱和土的液化模型，提出了适用于非饱和黄土的动力液化评判方法。本研究对于进一步认识振动条件下非饱和黄土边坡流态化破坏的形成机理，以及地震影响下黄土地区地质灾害的防控具有重要的理论价值和现实意义。