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流变岩体中让压支护作用下隧道力学行为研究

INVESTIGATION ON THE MECHANICAL BEHAVIOR OF TUNNEL SUPPORTED BY YIELDING SUPPORTS IN RHEOLOGICAL ROCKS

  • 摘要: 高地应力深埋软岩隧道大变形问题已成为隧道工程建设领域的突出难题. 根据高地应力深埋软岩隧道的变形特征, 基于"围岩能量吸收、变形释放"的让压支护是解决软岩隧道大变形问题的有效方法. 针对流变岩体中深埋圆形隧道在让压支护作用下的力学响应问题, 通过引入分数阶微积分理论, 采用Abel黏壶元件建立了改进的分数阶Burgers蠕变模型来表征围岩的时效变形. 此外, 通过在让压支护不同变形阶段引入刚度修正系数, 克服了传统支护未能考虑围岩变形释放的问题. 据此, 本文推导了在考虑支护延迟安装影响下, 不同变形阶段围岩与让压支护相互作用的解析解. 为了验证理论研究的正确性, 对一算例进行了不同解答及工程结果的比对, 吻合较好. 最后, 参数研究结果表明: 围岩与让压支护间的相互作用受蠕变本构模型分数阶阶数影响较大. 隧道的位移或支护压力与让压位移、支护刚度修正系数间存在线性比例关系, 但由于刚度修正系数仅保持在较小的变化范围内, 隧道的位移或支护压力变化并不显著.

     

    Abstract: Large deformation problem in soft rocks tunnels at great depth has become a great challenging task for many rock engineers. According to the deformation characteristics of soft rocks under high pressure, yielding supports following the principle of deformation release are able to accommodate rock deformations without being damaged, having been proved to be a feasible and effective solution to deal with such problem. The main purpose of this paper is to theoretically investigate the mechanical response of a deep circular tunnel excavated in rheological rock masses, where yielding supports are applied. Based on the fractional derivative theory the improved fractional Burgers creep model by adopting the Abel viscous element is established to describe the time-dependent deformations of geomaterials. In addition, the correction coefficients of supporting stiffness in different deformation stages are proposed aiming at solving the problem that the traditional supports are unable to take the rock deformation release into account. According to those, this paper derives the analytical solutions for stresses and displacements around the tunnel in different deformation stages, considering the installation delay of support structures. Furthermore, in order to validate the effectiveness and reliability of the theoretical analyses, a well agreement between different solutions and field results can be obtained. Finally, the parametric investigation demonstrates that tunnel displacement and support pressure are greatly influenced by the fractional order of Burgers model representing the deformability of rocks. There exists a linear relationship between tunnel displacement or support pressure and yielding displacement. This linear relationship can also be found between tunnel displacement or support pressure and the correction coefficient of support stiffness. If this correction coefficient ranges in a low level, the change of tunnel displacement or support pressure is not remarkable. This paper may provide a new trail to quickly evaluate the time-dependent deformations of tunnels with yielding supports.

     

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