Shield tunnelling through densely populated urban areas inevitably disturbs the surrounding soil, potentially posing significant safety risks to nearby buildings and structures. The constitutive models currently employed in numerical simulations for tunnel engineering are predominantly confined to the assumptions of isotropy and coaxiality, making it challenging to adequately capture the complexity of the mechanical response of the soil surrounding the tunnel. Based on the proposed non-coaxial and anisotropic elastoplastic Mohr-Coulomb yield criterion, this study carries out numerical simulation analyses of soil disturbance induced by urban shield tunnelling. Herein, the anisotropic parameters n and β jointly determine the shape of the anisotropic yield surface. The results demonstrate that rotation of the principal stress axes is observed in most areas of the soil surrounding the tunnel face, with the phenomenon being particularly pronounced at the crown and the invert of the tunnel. As the anisotropic parameter n decreases, the maximum surface settlement above the tunnel axis increases. The influence of anisotropy on higher-stress unloading coefficients is significant, resulting in the development of a wider plastic zone around the tunnel. As the coefficient of lateral earth pressure at rest K0 increases, the maximum surface settlement gradually reduces. Under the influence of anisotropic parameter β or non-coaxial parameter k, the maximum surface settlement exhibits an approximately linear relationship with K0. However, the anisotropic parameter n has a significant influence on the trend of the maximum surface settlement with respect to K0, which leads to a non-linear relationship. Neglecting the effects of soil anisotropy, non-coaxiality, and the coefficient of lateral earth pressure at rest may lead to design schemes that are potentially unsafe. The results of this research can provide engineers with design bases for construction parameters and soil disturbance control while shield tunnelling in sandy pebble soil.

中文翻译：

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考虑非同轴性和各向异性的城市盾构在砂卵石土中掘进诱发的土体扰动


在人口稠密的城市地区进行盾构隧道掘进，不可避免地会扰乱周围的土壤，可能对附近的建筑物和构筑物构成重大安全风险。目前隧道工程数值模拟中采用的本构模型主要局限于各向同性和同轴性的假设，因此很难充分捕捉隧道周围土壤机械响应的复杂性。基于所提出的非同轴和各向异性弹塑性 Mohr-Coulomb 屈服准则，该文对城市盾构隧道施工引起的土体扰动进行了数值模拟分析。在此，各向异性参数 n 和 β 共同决定了各向异性屈服面的形状。结果表明，在隧道掌子面周围的大部分土壤区域都观察到主应力轴的旋转，这种现象在隧道的拱部和倒置处尤为明显。随着各向异性参数 n 的减小，隧道轴线上方的最大表面沉降增加。各向异性对较高应力卸载系数的影响很大，导致隧道周围形成更宽的塑性区。随着静止时侧向土压力系数 K0 的增加，最大地表沉降逐渐减小。在各向异性参数 β 或非同轴参数 k 的影响下，最大表面沉降与 K0 呈近似线性关系。然而，各向异性参数 n 对最大表面沉降相对于 K0 的趋势有显著影响，这导致了非线性关系。 忽视土壤各向异性、非同轴度和静止时侧向土压力系数的影响可能会导致设计方案可能不安全。研究结果可为工程师在砂卵石土中进行盾构隧道施工时的施工参数和土体扰动控制提供设计依据。