Study On Displacement Modes Of Active Fault And Adaptability Of Fault-crossing Tunnel Structure

In recent years,the infrastructure construction has flourished all over the country,and projects such as transportation,water diversion and energy transportation have been vigorously built throughout the country,and the construction mileage of tunnels has been increasing year by year.As more and more tunnel projects approach or have to cross active faults,due to the fault displacement,the tunnel lining will often be cracked,and the tunnel structure will be damaged.Therefore,it is of great significance to study the displacement mode of the active faults and the support safety of the fault-crossing tunnel and the adaptability of the tunnel lining to the fault displacement to the tunnel project affected by the active fault.In this paper,firstly,the geological and activity characteristics of active faults are summarized.Based on that,the numerical simulation of faults-moving with different types and dip angles is carried out using the typical geological structure of the Yuanmou-Lüzhi River active faults crossed by the Fenghuangshan Tunnel of the Water Diversion Project in central Yunnan.At the same time,the zoning of rock mass mechanical parameters in the fault zone and creep time were taken into account,and the distribution characteristics of fault displacements under different conditions were analyzed.Secondly,the advantages and disadvantages of different shapes of the fault-crossing tunnels are analyzed.The convergence rate and support force of different parts of the tunnel are studied,and the influence of the fault dip angle on the convergence rate and support force of the fault-crossing tunnel is studied.Finally,for the "hinged design" of tunnel lining,the influence of lining section length,joint material parameters,joint width and lining segmentation methods on the mechanical characteristics of lining structure under fault displacement is studied.The study shows: The horizontal and vertical displacement modes of reverse faults,normal faults and strike-slip faults are all "S" type,and the relationship between the displacement modes and fault dip angle is not significant;The gradient of creep displacement is closely related to mechanical properties of rock mass.The displacement modes of fault creep are affected by the zoning of the mechanical properties of fault zone rock masses,and the mode of the displacement is “Z” type when the fracture zone is homogeneous and not the same as the influence zone;Localization problems of normal faults and reverse faults displacement modes are occurred with creep time.The displacement modes of strike-slip faults don’t change with the creep time.The evaluation indexes of the horseshoe tunnel are better than the door shape;the convergence rate of the dome of each dip fault-crossing tunnel is larger than the convergence ratio of the arch waist;under the same support mode,the larger the fault dip angle,the greater the convergence rate of the tunnel vault and the arch waist.The shorter the section length of the lining section,the smaller the lining stress when the fault is displaced;within the scope of this study,the material parameters of the joint have less influence on the lining force when the fault is displaced.The larger the joint width,the larger the tensile stress of the reverse fault-crossing tunnel lining and the smaller the compressive stress.The smaller the tensile stress of the normal fault-crossing tunnel lining,the larger the compressive stress;the smaller the stress of the lining of the strike-slip fault-crossing tunnel.Different lining segmentation methods have great influence on the stress of the lining of the reverse fault-crossing tunnel.The vertical section stress distribution law is better than the inclined section,which has little effect on the lining force of the normal fault-crossing tunnel and the strike-slip fault-crossing tunnel.