Deformation Of Layered Soft Rock Tunnel Further Study On Classification Standard For Large

The asymmetric deformation mechanism and grading criteria of laminated soft rock tunnels have been the focus of many scholars’ research.In this thesis,the classification criteria and deformation mechanism for large deformation tunnel deepening in laminated soft rock tunnel are studied in the context of Ganqing tunnel project of Xicheng Railway.The laminae are considered as homogeneous planes and the yield strength of the rock mass is integrated with the maximum principal stress and the normal angle of the laminae,and the secondary development is carried out in FLAC3 D platform using C language.The mechanism of large deformation in laminated soft rock tunnels was investigated from four aspects: laminar surface production,horizontal lateral pressure coefficient,laminar surface elastic modulus,and ground stress level.It is found that the all-over nodal intrinsic model used in FLAC3 D for studying laminated rock is poorly applicable.The developed TI-IS intrinsic model is validated by writing it in C language,changing the definition methods of internal friction angle and cohesion,and conducting elastic phase,plastic phase,and uniaxial compression simulations,and the results prove that the developed intrinsic model is more applicable to laminated rock and can more realistically The results demonstrate that the developed model is more applicable to laminated rock and can reflect more realistically the various phenomena during the excavation of laminated soft rock tunnels.Numerical simulations of the excavation process of laminated soft rock tunnels were carried out in FLAC3 D using the TI-IS principal structure model to study the mechanism of large deformation in laminated soft rock tunnels,and the main factors and patterns of tunnel deformation were obtained.(1)The influence of dip angle on laminated soft rock tunnel: the maximum deformation position of the arch wall changes with the increase of dip angle from the shoulder to the foot of the arch to the side wall to the wall,i.e.the maximum deformation position shifts down along the surrounding rock with the increase of dip angle.In the same tendency of different dip angle of the working conditions,the deformation of the largest amount of working conditions,dip angle concentrated in30 °to 60 °.(2)The influence of inclination on laminated soft rock tunnel: the maximum deformation position of the arch wall with the inclination angle decreases when the inclination angle is small,the maximum deformation position of the arch wall with the inclination angle decreases more obviously when the inclination angle is larger,that is,the increase of the inclination angle will increase the role of the inclination angle on the tunnel.(3)the rise of lateral pressure coefficient leads to the rise of the initial stress in the horizontal direction,making the excavation unloading effect is obvious,the impact of laminate surface yield on the deformation with the rise of the lateral pressure coefficient gradually become larger,that is,the same laminate surface yield conditions,with the increase of the lateral pressure coefficient,the maximum deformation position down the arch wall.(4)When the inclination of laminate surface is 90°,the effect of weak plane is obvious,and the maximum deformation position is located at the side wall.In other inclination angles,the increase of homogeneous plane modulus of elasticity makes the effect of laminar surface production stifled,i.e.,the larger the modulus of elasticity of homogeneous surface,the maximum deformation position moves along the cavity wall from the sidewall to the arch shoulder direction,and the convergence value of tunnel horizontal direction becomes smaller.(5)In the case of 45°and 60°dip angle,the maximum deformation position moves along the cavity wall from the shoulder to the side wall with the increase of the ground stress level in the same dip angle,i.e.the increase of the ground stress level makes the laminar surface yield to further enhance the tunnel effect.However,in the inclination angle of 30 °,the effect of increasing the ground stress level on the laminar surface profile is not significantly increased.The extrusive rock code indicates the level of large deformation during the construction phase based on the relative deformation,but does not specify which form of support it is based on.In this thesis,the classification method for large deformation in laminated soft rock tunnels is modified by using class V rock as standard support and referring to the code.It provides a reference for the industry to deal with and understand the large deformation of laminated soft rock tunnels.