挤压隧道中围岩与内置高压缩性元件衬砌相互作用机制研究

STUDY ON THE INTERACTION MECHANISM BETWEEN SURROUNDING ROCK AND LINER WITH HIGHLY DEFORMABLE ELEMENTS IN SQUEEZING TUNNELS

  • 摘要: 内置高压缩性元件衬砌作为一种环向让压衬砌,能够通过高压缩性元件的压缩来适应大变形,达到让压的目的。针对挤压大变形隧道中围岩与该种让压衬砌相互作用的力学机制,采用改进的分数阶Burgers蠕变模型表征围岩的时效变形特征,推导了考虑掌子面效应和支护延迟作用下隧道位移及支护压力的解析解,并通过在Lyon-Torino Base隧道中的应用,验证了理论解答的正确性。进一步,基于理论解答,探讨了围岩分数阶阶数、支护时间、高压缩性元件的屈服应力对支护效果的影响。得到主要结论如下:随着围岩本构模型分数阶阶数的增加,围岩的变形能力越强,隧道位移和支护压力也呈现上升的趋势;衬砌的安装时间对支护效果具有重要影响。为保证围岩不产生失稳,支护结构应尽早地安装;另一方面,为确保支护压力处于衬砌结构的承载范围内,应该合理地确定高压缩性元件的长度和个数,以降低支护压力;高压缩性元件的屈服应力对隧道位移和支护压力的影响并不显著,但这不意味着可以盲目地确定高压缩性元件的屈服应力,需根据围岩性质和衬砌特性来确定其合理范围。在该范围内,既能够保证隧道稳定,也能充分发挥高压缩性元件的让压作用。

     

    Abstract: As a type of circumferential yielding supports, liner embedded with highly deformable elements can achieve the release of rock deformations through the compressible deformation of highly deformable elements. The paper aims to investigate the interaction mechanism between surrounding rock and liner with highly deformable elements. In this paper, the improved fractional Burgers model is established to describe the time-dependent behavior of rock, and then the analytical solutions for tunnel displacement and support pressure are derived taking into account the tunnel face advancement effect and the installation delay of support. In addition, the reliability and effectiveness of analytical solutions are well validated by comparing the monitoring data in Lyon-Torino Base tunnel. Furthermore, based on the analytical solutions proposed in this paper, a comprehensive parametric investigation including the influences of fractional order of rock constitutive model, supporting time and yield stress of highly deformable elements is carried out. The main conclusions are made as follows: The deforming ability of surrounding rock becomes stronger as fractional order of Burgers model increases, and the tunnel displacement and support pressure also exhibit an increasing trend; Supporting time has a great influence on tunnel performance. On the one hand, in order to keep rock stability it is recommended to install support structures as early as possible. On the other hand, the optimal number and length of highly deformable elements should be determined for ensuring that the support pressure varies within a range of bearing capacity of liner; The yield stress of highly deformable elements does not pose a significant effect on tunnel displacement and support pressure. However, this does not mean the yield stress of highly deformable elements can be determined randomly. There should be an appropriate range for this yield stress, where the purposes for both the tunnel stability and the release of rock deformation can be achieved.

     

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