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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。
Aiming at the deformation and strength anisotropy of surrounding rock in different parts (vault or arch waist) during excavation of loess tunnel, this paper takes the original loess of Wangjiagou tunnel in Baoji-Lanzhou Passenger Dedicated Railway as an example to study the structural strength Anisotropy problem. Taking Wangjiagou tunnel as the original loess horizontal and vertical direction for the shear test, unconfined compressive strength and tensile strength test and study, considering the structural anisotropy, and the original Wangjiagou loess scanning electron microscopy The reason of the anisotropy of intact loess is analyzed structurally, and finally the mechanism of the anisotropy of loess in situ is discussed. The results show that the ratio of horizontal to vertical strain decreases with the increase of confining pressure, increases first and then decreases with the increase of normalized deviation stress, and the peak point increases exponentially with normalized deviation stress. The anisotropy geometry model of undisturbed loess structure is proposed, and the anisotropy intensity parameter index of undisturbed loess is given.