基于结构稳定理论的深埋隧道收敛约束设计方法研究

Research of convergence-confinement design method for deep buried tunnels based on structural stability theory

传统的深埋隧道稳定性计算理论及支护结构设计方法不适应复杂地质条件下软岩大变形带来的重大挑战,亟待突破。首先阐明挤压大变形隧道失稳机制以及围岩与支护结构相互作用机制;基于弹塑性理论得出围岩弹性–塑性交界面应力与围岩塑性区半径,确定围岩稳定分析范围;基于能量法,将塑性区围岩与支护结构视为各自独立结构,引入围岩–支护接触面应力与变形连续条件,分别建立围岩、支护结构稳定性分析总能量方程,采用势能驻值原理和瑞利里兹法进行解析计算,得出围岩稳定曲线和支护特征曲线,并通过图示法分析评判支护结构的合理性;探究围岩与支护结构相关参数及地震力对稳定性的影响规律,并结合实际工程验证本文方法的准确性与实用性,最后展望进一步研究中的前沿问题。结果表明:提出符合新奥法施工原则、现代隧道工程理念和失稳机制的基于结构稳定理论的深埋隧道收敛约束设计方法,实现变形控制设计;初始地应力取40MPa时,围岩支护作用占比为91.4%,表明围岩是保持隧道稳定的主要支护力量;围岩弹性模量、内摩擦角、锚杆支护强度、地震应力对深埋隧道稳定性影响显著;结合木寨岭隧道支护结构设计分析,验证所提出的收敛约束设计方法具有较好的工程适用性。研究成果为提出深埋隧道支护结构设计方法提供了全新的思路。

The traditional stability calculation theory and support structure design methods of deep buried tunnels are not suitable for the significant challenges posed by large deformations of soft rock under complex geological conditions.There is an urgent need for breakthroughs in this field.Firstly,the instability mechanism of squeezed large deformation tunnels and the interaction mechanism between surrounding rock and support structures are elucidated.Based on the elastoplastic theory,the stress at the elastic-plastic interface of the surrounding rock and the plastic zone radius of the rock are determined to establish the scope of stability analysis for the surrounding rock.Based on the energy method,the surrounding rock in the plastic zone and support structure are regarded as independent structures.The stress and deformation continuity conditions at the rock-support interface are introduced,and total energy equations for the stability analysis of the surrounding rock and the support structure are separately established.The stationary principle of potential energy and Rayleigh-Ritz method are used for analytical calculations to obtain the stability curve of the surrounding rock and the characteristic curve of the support structure.The rationality of the support structure is analyzed and evaluated by the graphic method.The influence of related parameters of the surrounding rock and the support structure and seismic forces on stability is investigated.The accuracy and practicality of the proposed method are verified through practical engineering applications.Finally,the frontier problems in further research are prospected.The results show that a deep buried tunnel convergence constraint design method based on structural stability theory is proposed,which conforms to NATM principles,modern tunnel engineering concepts and instability mechanism.This method achieves deformation control design.When the initial ground stress is 40 MPa,the contribution of the surrounding rock support is 91.4%,indicating that the surrounding rock is the main supporting force to maintain the stability of the tunnel.The elastic modulus of surrounding rock,internal friction angle,the strength of rock bolting,and seismic stress have significant effects on the stability of deep buried tunnels.Combined with the support structure design analysis of Muzhailing tunnel,the convergence constraint design method proposed is proved to have good engineering applicability.The research findings provide a new perspective for the design of support structures for deep buried tunnels.