隧道软弱围岩的卸荷特征与大变形控制研究

隧道软弱围岩大变形往往表现出时效性的流变变形特征,对此特征提出了一种环状间隔式衬砌与主动性卸载相结合的永久性支护理念。在合理的简化下建立了隧道衬砌段与非衬砌段的隧道力学分析模型,并在围岩常用蠕变模型、Mohr-Coulomb强度准则和非关联塑性流动法则基础上,对支护段围岩进行黏弹塑性求解,得到了围岩的黏弹塑性变形位移解。在参考现有围岩应力释放模型并确定无支护段围岩应力释放系数之后,对无支护隧道段围岩进行求解,得到了围岩的黏弹塑性变形位移表达式,建立了未支护洞段围岩位移与支护洞段围岩压力的关系。算例分析表明,理论分析与实际工程中围岩的应力和位移的变化是相吻合的。

Study on Unloading Characteristics and Large Deformation Control of Soft Rock Surrounding Tunnel

Large deformation of soft rock surrounding tunnel is often characterized as time-based rheological deformation, thus a concept of permanent support combined cyclic spaced lining and initiative unloading was presented. This paper, with reasonable simplification, established a mechanical analysis model of tunnel lining and non-lining sections and, depending on the commonly-used creep model, Mohr-Coulomb strength criterion and non-associated plastic flow rule, found out the viscoelastic plasticity deformation displacement solution of surrounding rock in the supported section. For the surrounding rock in the non-supported section, the solution was found by reference to current stress relief model for surrounding rock and after the stress relief coefficient thereof was specified, so that an expression of viscoelastic-plastic deformation displacement was obtained, by which the relation between the displacement of surrounding rock in the non-supported section and the pressure of surrounding rock in the supported section was established. The calculation example based analysis shows that the surrounding rock has its stress and displacement change consistently in theoretical analysis and practical engineering.