西安Q_3黄土固有各向异性特性研究

Inherent anisotropy of Q_3 loess in Xi'an

【目的】分析西安Q3黄土固有的各向异性特性,为黄土结构性及其各向异性特性的关系研究提供依据。【方法】分别从竖向裂隙向(δ=90°)、卸荷边坡走向(α=0°)和边坡倾向(α=90°)3个方向制取陕西西安Q3黄土试样,通过原状黄土、重塑黄土及饱和黄土无侧限抗压试验和三轴固结排水试验,研究其强度和变形参数在不同围压和不同方向的差异,测试其强度、构度以及灵敏性,分析破坏应力、抗剪强度及切线模量等各向异性特性。【结果】西安Q3黄土垂直向的初始结构特性明显强于水平正交的两个方向,差距可达150%,而水平正交两个方向差异不大;破坏应力和抗剪强度规律相似,其差异具体体现在黏聚力方面,而摩擦角的差异性不大,且原状黄土抗剪强度与构度指标有较好的线性关系;垂直向的初始切线模量与水平正交两个方向存在较大差异,垂直向δ=90°与水平向α=90°初始切线模量之比平均约为1.81。【结论】外荷作用下黄土内部颗粒重组,黄土初始结构特性有所改变,应重视黄土地基工程中各向异性的存在。

【Objective】The structure of loess has been widely concerned,but the understanding of the anisotropic properties closely related to the structure is not comprehensive.This study investigated the inherent anisotropy of Q3 loess in Xi’an to provide basis for further studies.【Method】This paper prepared Shaanxi Q3 loess samples from the vertical fissureδ=90°,unloading slope to the directionα=0°and slope tendencyα=90°.Through the development of undisturbed loess,remolded loess and saturated loess unconfined compression test and triaxial consolidation drainage test,the differences of the strength and deformation parameters under different confining pressures and directions were studied.The strength,structure and sensitivity of the difference were determined and anisotropic properties including breaking stress,shear strength and deformation modulus index were analyzed.【Result】The anisotropy of the mechanical properties of Q3 loess in Xi’an was significant,and the initial structural characteristics of the vertical direction were significantly stronger than the horizontal and orthogonal directions with difference of 150%.The difference between horizontal and orthogonal directions was not significant.The damage stress and shear strength were similar and the difference was embodied in the cohesion not the friction angle.The shear strength of the original loess had a good linear relationship with the index.The initial tangent modulus of the vertical direction was higher than the horizontal directions with big difference.The average tangent modulus ratio of verticalδ=90°to horizontalα=90°was about 1.81.【Conclusion】Loess generated particulate recombinant under outside load,and the initial structure of loess was changed.Therefore,we should pay attention to the existence of anisotropy in loess foundation engineering.