微结构特性对饱和黄土动残余变形的影响研究
Effect of microstructure properties on of dynamic residual deformation behavior of saturated loess
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摘要: 通过对黄土高原不同微结构分区的黄土进行微结构电镜扫描试验和饱和状态下的动三轴液化试验,以及相同物性状态下兰州原状与重塑黄土液化的对比试验,得出了饱和黄土结构性对抗液化强度的影响规律,定性定量分析了微结构类型对饱和黄土动残余变形特征的影响关系,并通过分析不同地区黄土的动应力-动残余应变,得出了不同微结构特性黄土动残余变形发展的机制。研究结果表明:饱和黄土的抗液化强度与其结构性有关,重塑过程中由于颗粒重组和颗粒间胶结作用的减弱,导致土体的抗液化强度降低;饱和黄土液化时动残余变形随着振次增加呈指数关系增加,拟合参数主要受控于黄土的密度和塑性指数,动残余变形的增长与微结构特性关系密切,结构强度越高的黄土动残余变形增长越缓慢;不同微结构特性的黄土液化时动残余应变发展机理不同,胶结性较弱的黄土动残余变形可划分为黏弹塑性和塑性阶段,胶结性较强的黄土液化时依次产生黏弹塑性、黏塑性和塑性变形。Abstract: Based on the SEM tests and dynamic triaxial tests on the loess with different microstructures from the Loess Plateau region and the liquefaction tests on undisturbed and disturbed Lanzhou loess with the same property state, the influence rules of structural properties of saturated loess on liquefaction strength are obtained. The relationship between microstructural types and the dynamic residual deformation behavior of saturated loess are qualitatively and quantitatively analyzed. Moreover, the development mechanisms of the dynamic residual deformation of the loess with different microstructures are obtained through analysis of the dynamic stress-dynamic residual strain of the loess in different regions. The results show that the liquefaction strength of saturated loess relates to the micro structure. The liquefaction strength of the soil decreases during the disturbed process because the particle reorganization and the cementation are weakened. The dynamic residual deformation of the saturated loess exponentially increases with the increase of vibration times, and the fitting parameters are mainly controlled by the density and plasticity index of the loess. The increase of dynamic residual deformation closely relates to the microstructural properties, the higher the structural strength, the slower growth the dynamic residual deformation of the loess. The development mechanisms of dynamic residual deformation are different for the loess with different microstructural properties. The dynamic residual deformation of weak cementation loess can be divided into visco-elastoplastic and plastic stages. However, the dynamic residual deformation of stronger cemented loess can be divided into visco-elastoplastic, visco-plasticity and plastic stages successively during liquefaction.