深部软弱流变地层中隧道围岩与“让压变形”支护系统间相互作用关系研究

Deep-buried soft rock mass generally has a significant rheological property, and the traditional support of tunnel cannot withstand the strong rheological deformation of surrounding rock due to its high stiffness. However, the novel yield-deformable support system, which has a certain stiffness and compressibility, can control the large deformation of tunnel in soft rock. Therefore, it is of great importance to study the interaction mechanism between surrounding rock and yield-deformable support system for tunneling in deep soft rock. Based on the numerical simulation, the present project firstly aims to study the deformation performance and equivalent stiffness of yield-deformable support with the two types of radial and circumferential deformations, and establish their mechanical analysis models. Then, the analytical solutions of the interaction between surrounding rock and yield-deformable support system are deduced, where the influences of tunnel face advancing and rock rheology are taken into consideration. Also, based on field monitoring, the solutions are verified, and the time-effect law of surrounding rock and yield-deformable support is explored from a practical point of view. Meanwhile, to investigate the deformations and failure modes of tunnels with the yield-deformable support system, the model tests for non-circular tunnels and under the hydrostatic stress field are conducted. Finally, the convergence-confinement method for the tunnels in deep-buried soft rheological ground is established and the calculation method for determination of supporting pressures between liners of this support system is proposed. The conclusions of the present project provide some useful guidance for designing and constructing tunnels with the yield-deformable support system in the deep-buried soft rock.

深部软弱岩体一般具有较强的流变性，传统的隧道刚性支护无法抵抗围岩的强流变变形，而新型“让压变形”支护具有一定刚度和可压缩性，其能有效地控制软岩隧道的大变形。因此，对深部软弱流变地层中隧道围岩与“让压变形”支护体系间的相互作用机制研究具有重要意义。本项目首先基于数值模拟，研究“让压变形”支护结构的整体变形性能和等效支护刚度，建立“让压变形”支护体系的力学模型。基于该模型，推导出在开挖面推进和岩体流变双重影响下隧道围岩与“让压变形”支护体系的作用解答；同时，基于现场监测对该解答进行验证，并从实际角度探究围岩与“让压变形”支护的时效作用规律；之后，利用物理模型试验对非圆形和非等压场下“让压变形”支护隧道的变形和破坏模式进行分析。最后，建立起深部流变软岩隧道的收敛约束法，并提出“让压变形”支护体系内围岩压力分担的计算方法。研究结果为深部软岩隧道“让压变形”支护体系的施工和支护设计提供指导。

本项目围绕“‘深部软弱流变地层让压变形支护体系与围岩时效作用关系”这一关键科学问题，首先借助声发射（AE）、P波波速、SEM以及低场核磁共振（NMR）技术，系统研究了深部软弱流变地层围岩在卸荷蠕变过程中内部微观裂纹和孔隙演化特征，揭示了不同蠕变荷载和蠕变阶段下典型软岩的脆性蠕变机制，并在基础上基于翼裂纹扩展理论提出了可精准刻画软岩在常规三轴加载下的弹塑性损伤（包括峰后软化）和卸荷蠕变损伤（蠕变三阶段）的行为弹塑性-蠕变损伤模型；其次，基于微分概念，从理论角度提出了可表征让压屈服单元受荷三阶段特征的等效刚度模型，同时建立了考虑喷射混凝土龄期硬化过程和让压屈服单元三阶段行为的“让压变形”支护体系的力学分析模型；最后，基于黏弹性、黏弹塑性理论，提出了同时考虑围岩流变力学性和隧道纵向开挖过程的让压支护隧道时效解，揭示了深部软弱流变地层中“让压变形”支护体系与围岩间的时效作用机制，并提出该支护体系内围岩压力分担的计算方法。