中文摘要：

针对黄土隧道开挖过程中不同部位（拱顶或拱腰）处围岩表现出的变形及强度各向异性情况,以宝鸡-兰州客运专线王家沟隧道原状黄土为例,着重探讨原状黄土结构强度各向异性问题。分别取王家沟隧道原状黄土水平与竖直方向进行抗剪、无侧限抗压及抗拉强度试验研究,考虑结构性对各向异性的影响,并对王家沟原状黄土进行电镜扫描,从微观结构上分析原状黄土具有各向异性的原因,最后探讨了原位状态下黄土各向异性的发生机制。结果表明：水平与竖直向应变比随围压的增大而减小,随归一化偏差应力的增大先增大后减小,峰值点随归一化偏差应力呈幂函数递增。提出原状黄土结构强度各向异性几何模型,并给出原状黄土各向异性强度参数指标。

英文摘要：

In view of the anisotropy of deformation and strength of surrounding rock at different locations（vault and hance） in loess tunnel,the anisotropy of intact loess with respect to structural strength is empatically discussed.The intact loess is sampled from Wangjiagou tunnel along Baoji-Lanzhou passenger dedicated line.A series of tests including shear test,unconfined compression test,tensile strength test are conducted on the intact loess with sampling directions of vertical and horizontal directions.Considering the influence of structure of loess on its anisotropy,the scanning electron microscope（SEM） test is also performed to analyze the main reasons leading to the anisotropy of intact loess.The results indicate that the strain ratio of horizontal direction to vertical direction decreases with the increasing of confined pressure,but firstly increases and then decreases with the increasing of normalized deviatoric stress;the peak（singularity） increases with normalized deviatoric stresses in the manner of power function.A geometric model of anisotropy of structural strength of intact loess is presented;and related strength parameters are also proposed.