Study On Deformation Characteristics Of Surrounding Rock And Mechanical Response Of Supporting Structure In Deeply-buried Circular Tunnel

The complex deformation characteristics of surrounding rock will appear during the deep tunnel excavation.The mechanical condition and response of supporting structure have great influence on the engineering safety.Therefore,it is important to analyze the interaction between surrounding rock and supporting structure.This dissertation aims at obtaining the deformation of surrounding rock and the mechanical response of supporting structure in the tunnel engineering,and adopts the theoretical analysis and numerical simulation to study the interaction mechanism between surrounding rock and supporting structure in deeply-buried circular tunnel.The main contents include the followings:（1）The theoretical analysis is based on the convergence-confinement method,including longitudinal displacement profile,ground reaction curve and support characteristic curve.A new solution of longitudinal displacement profile with better applicability is proposed.Based on this,a new analytical procedure for calculating the rock-support interaction results is obtained.Furthermore,the effect of support stiffness and supporting time is discussed quantitatively.The results show that,it can avoid excessive support pressure by postponing supporting time and selecting the concrete support with small elastic modulus and thickness.（2）The fictitious support pressure is utilized to quantify the spatial constraint effect.Firstly,the initial deformation of surrounding rock and the fictitious support pressure are obtained analytically;Secondly,the final support pressure and the final deformation of surrounding rock are calculated numerically.Then,the effect of in-situ stress,rock mass quality and supporting time on the above four parameters is discussed.Furthermore,the influence of grouting reinforcement and bolt support on surrounding rock is studied.The results show that,the self-bearing ability of hard rock is high and that of soft rock is low.Grouting reinforcement and bolt support are effective measures to limit the deformation of soft rock.（3）The numerical simulation method is adopted to study the deformation characteristics of surrounding rock in homogeneous and composite rock layers under the non-hydrostatic stress field,and the interaction between rock and liner under different stress release rates.The results show that,the maximum displacement point of tunnel in homogeneous rock layer is related to the lateral stress coefficient,the vertical stress and the stress release rate,and the evolution of liner mechanical response is complicated.In composite rock layer,the maximum displacement of tunnel occurs near the normal direction of hard-soft rock interface,and the maximum and minimum pressure point of liner are near the soft-hard rock interface.（4）The analytical and numerical methods are adopted to study the whole process of TBM excavation in deeply-buried tunnel.Firstly,the interaction mechanism between rock and TBM is expounded by the theoretical analysis.The squeezing level of surrounding rock is evaluated and the pressure on the TBM shield is calculated.Afterwards,a three-dimensional TBM excavation model is established through FLAC^3D.The influence of lithological parameters,tunnel diameter and backfill layer thickness on the deformation of surrounding rock and the mechanical response of support are studied.The results show that,the bending moment of the liner is the largest in composite rock layer,the middle in soft rock,and the smallest in hard rock.The larger the tunnel diameter is,the larger the moment of liner is.In comparison with liner,the change of thickness of the backfill layer has minor effect on the deformation of surrounding rock.