Study On Construction Stability And Risk Management Of Tuanyueshan Tunnel Crossing Fault Fracture Zone

As one of the common engineering geological conditions in tunnel construction,fault fracture zone is prone to deformation and failure such as floor uplift,primary branch failure and secondary lining cracking due to rock mass fracture,poor self-stability of surrounding rock,inaccurate predicted position and poor supporting effect.For this reason,this paper takes the fault fracture zone appearing in the tuanyueshan tunnel project of lunan high-speed railway as the background,comprehensively USES numerical simulation,field measurement and BIM visualization technology to conduct in-depth research on the construction technology of Tuan Yueshan tunnel crossing the fault(Tuan Yueshan fault and Ni Shan fault).The main research work and results are as follows:(1)compared and analyzed the advantages and disadvantages of each method,combined with the geological conditions of the Tuan Yueshan fault and the Ni Shan fault zone,the construction method combining the step method and the three-step method was proposed,and the corresponding support scheme was made.(2)By means of numerical simulation,the influence rules of construction of Tuan Yueshan and Ni Shan fault zones are obtained.The study shows that the surface subsidence increases significantly when passing through the fault zone,and the maximum subsidence is 3.81 mm and 7.10 mm respectively.The plastic zone of the tunnel in and out of the fault zone varies greatly,and the plastic zone at the fault zone is more obvious,and the location is mainly in the arch waist.As for the stress of the supporting structure,the stress in the fault area is relatively large,the compressive stressis mainly concentrated in the arch waist,the tensile stress is mainly distributed in the arch foot and arch roof area,and the bending moment of the pipe shed is mainly affected by the up-step excavation.(3)Combined with the construction of Tuan Yueshan fault and Ni Shan fault zone,the construction law of the crossing fault zone is further studied,and the relevant construction countermeasures and Suggestions are given.The results show that during the construction of the fault zone,the deformation of the surrounding rock is affected by the excavation steps,the settlement of the arch is mainly the excavation of the upper steps,and the convergence of the arch waist is mainly the excavation of the middle steps.The stress change of the fault on the primary support of the arch waist was the largest,followed by the arch foot,and the impact of the arch and the arch bottom was the smallest,indicating that the fault had the largest impact on the primary support of the surrounding rock at both ends,and the influence of the fault on the core was smaller.In order to prevent cracking or collapse due to excessive initial support stress at the fracture layer,the countermeasures of increasing the thickness of the pipe shed or increasing the density of the pipe shed to increase the stress on the pipe shed were given.(4)Through the analysis of the construction monitoring data of Tuan Yueshan mountain and Ni Shan mountain,the actual deformation law of the fault zone is obtained.The analysis shows that the maximum value of arch settlement and arch waist convergence,deformation rate and axial force variation of steel arch are within reasonable control range during the construction of fault zone,and the proposed construction method and support scheme can well complete the crossing of fault zone.Secondly,the field monitoring data and numerical simulation results were compared and analyzed,and the causes of the gap between them were analyzed.(5)Combining with tunnel construction in fault zone,the digital platform architecture and dynamic risk management system for mountain tunnel construction are proposed based on BIM technology.Firstly,BIM technology is applied to carry out BIM visual modeling for Tuan Yueshan tunnel Tuan Yueshan fault and visual construction simulation.Secondly,set up the mountain tunnel construction of the digital platform based on BIM technology architecture,and based on the digital managementplatform,set up,including risk monitoring,risk identification,risk assessment,a set of dynamic risk management system,to provide guarantee for group in mountain tunnel construction,and can provide certain reference for other tunnel construction digital management and reference.