复杂应力条件下饱和黄土动力变形特性研究

Dynamic deformation of saturated loess under complex stress condition is one of key and outsanding research problems in the geotechnical earthquake engineering field. Both of substances and thoughts in this research, moreover, are new and innovative. This application mainly focuses on dynamic deformation behavior of saturated loess under complex stress condition during seismic action. Based on the cyclic torsional shear test with considering the effect of principal stress rotation, intermediate principal stress and consolidation deviator stresses ratio, analyze the dynamic strain characteristics of saturated loess under complex stress condition, and discuss the basic physical process and the mechanism on the development of dynamic strain. In addition, combined influence of physical behavior, dynamic loading behavior and consolidation condition on dynamic deformation behavior of saturated loess under complex stress condition will be analyzed based on some adjuvant tests such as SEM test and static triaxial test. The critical influence parameters of dynamic residual strain of saturated loess will be summarized and a theoretic model of deformation under complex stress condition will be established. Moreover, combine with the pore water pressure behavior during cyclic torsional shear test, the responding mechanism of pore water pressure under deformation control will be discussed. Theoretic model of pore water pressure based the characteristics of residual strain under complex stress condition will be deduced. The rationality and applicability of the two theoretical models, furthermore, will be verified carefully by laboratory data of cyclic torsional shear test. For the special kind of soil, saturated loess, the expected results of this research application will be helpful to understand its dynamic deformation characteristics and to obtain a model with better rationality and applicability on dynamic deformation and pore water pressure behavior. In summary, this application has an obvious significance at the aspects of science and practice to develop the understanding on relative scientific problems in the research field of geotechnical earthquake engineering.

复杂应力条件下饱和黄土动力变形特性是岩土地震工程领域仍未解决的重要科学问题。本项申请以地震作用时的复杂应力条件下饱和黄土动力变形特性为出发点，在考虑主应力轴旋转、中主应力变化和固结偏应力比影响的循环扭剪试验的基础上，通过分析复杂应力条件下饱和黄土动应变的发展特征，探讨动应变发展的基本物理过程与实际力学机制，在此基础上系统分析物性条件和动力加载特性的影响，归纳影响动残余应变的关键参量，建立复杂应力条件下饱和黄土动残余变形的理论估算模型。并结合孔隙水压力发展特征，深入探讨变形控制作用下的孔隙水压力响应机制，推导出以复杂应力条件下残余应变特征为关键参量的饱和黄土孔隙水压力发展模型。基于实际试验结果，对上述两个理论估算模型的适用性和合理性进行检验。本项申请立足国内外岩土工程与地震工程交叉领域热点关注的科学难题，研究内容和思路皆具创新性，预期结果具有科学和应用方面的重要意义。

我国黄土高原是世界上黄土分布面积最广、厚度最大、成因类型最复杂的地区，同时该区域地处强震多发地带，历史强震多次造成山河改观，超过140万人死亡，财产损失不计其数。黄土具有强烈的水敏性和地震易损性特征，饱和状态下的工程性质与非饱和状态下具有显著的差异，特别是其在遇水饱和后的软化特性使动力作用下的灾变风险大大增加，从而使地震作用下饱和黄土的动力特性和灾变行为逐渐受到关注。然而，国内外有关饱和黄土动力变形特性和灾变机理方面的研究对于物性指标和应力条件的影响以及变形关键影响参量的考虑存在不足，对于孔隙水压力与变形的相互关系研究尚显薄弱，相关的研究工作亟待开展。. 本项研究以地震作用时复杂应力条件下饱和黄土动力变形特性为出发点，通过不同地区饱和原状黄土试样的空心圆柱循环扭剪试验和动三轴试验，研究了复杂应力条件下饱和黄土的动应变发展特征，提出了复杂应力条件下饱和黄土液化的动应变发展的物理过程和力学机制，分析了主要物性指标、主应力轴旋转角、中主应力系数、固结偏应力比、动荷载频率、幅值和荷载类型等因素对饱和黄土动残余变形的影响，归纳总结了饱和黄土液化时动残余应变的主要影响因素和关键影响参量，得到了复杂应力条件下饱和黄土动残余应变的理论估算模型，分析了复杂应力条件下饱和黄土液化的动孔隙水压力特征，提出了循环扭剪液化时变形控制作用下的孔隙水压力响应机制，建立了动应变控制作用下饱和黄土孔隙水压力发展模型，并综合考虑土性条件和荷载条件，探讨了循环荷载作用下饱和黄土液化的机制。. 项目研究成果丰富和发展了黄土动力学中有关饱和黄土的动力特性及灾变行为理论，对进一步认识饱和黄土地震液化灾害特征和机制提供了科学依据，其在黄土地区工程建设和国土规划中推广应用，可为黄土高原强震区国家“一带一路”建设的实施提供重要的御灾保障，并可为黄土地区地震灾害防御技术的进步起到积极的推动作用。