| The construction of transportation networks has expanded the scope of highways and railways,with the central and western mountainous regions becoming the primary areas for construction.As an important component of transportation routes,the number of tunnels being constructed has been increasing year by year,often facing complex engineering geological conditions.The construction of mountain tunnels is usually mainly carried out by blasting and tunneling machine methods.However,blasting methods have problems such as over excavation,damage to surrounding rock,high vibration,and high dust concentration.TBM method is gradually being widely adopted due to its advantages of low cost,high construction efficiency,and small disturbance.Based on the Dujiangyan Irrigation Project Siguniang Mountain Mountain Rail Transit Project,this paper takes the Balang Mountain Tunnel 1 as the research object.The tunnel passes through the Wolong Ecological Protection Zone in Sichuan,with a high sensitivity to the ecological environment.Choosing the TBM method for construction has significant advantages.The maximum longitudinal slope of the tunnel reaches 12%,which is rare in domestic engineering projects.The line passes through many strata,among which it is inevitable to pass through soft and hard composite strata with different relative positions,and the depth of the overlying strata of the tunnel at different positions on the line will also change.Based on this,this article adopts a combination of similarity model testing and numerical simulation to study the TBM crossing of large longitudinal slope composite strata.The specific research content is as follows:(1)On the basis of the rock parameter range given in the geological report,samples were taken from the surrounding rock of the tunnel on site,and accurate parameter measurements were conducted on the soft and hard rocks of the composite formation through indoor uniaxial compression,triaxial compression,Brazilian splitting tests,etc.The differences in physical properties of the soft and hard rocks are studied,providing reliable parameters for similar physical model tests and numerical simulations.(2)Based on the similarity principle and model test conditions,the similarity ratio of the model that meets the test conditions was studied.Quartz sand,barite powder,gypsum and Vaseline are selected as the surrounding rock materials,and gypsum is used as the lining materials.The mix ratio test of tunnel surrounding rock and lining materials is carried out,and the mix ratio of composite stratum and segment lining materials is studied.(3)Based on the principle of similarity model testing,a self-made model test box and a micro excavation device were used to conduct TBM large longitudinal slope tunnel crossing composite strata experiments.The deformation and pressure of surrounding rock and internal force of lining at different inclinations in soft and hard composite strata were studied.(4)The numerical simulation software FLAC 3D was used to establish the models of different dip and inclination of composite rock stratum,and the influence of different dip and inclination of rock stratum on the response of surrounding rock and support structural mechanics was studied.By co MParison,the consistency and accuracy of similar physical model experiments and numerical simulation results were verified.(5)Based on the actual complex working conditions and limited test conditions of the project,and according to the consistency of the results of model test and numerical simulation,the numerical simulation software was further used to study the different slopes and burial depths of the tunnel.The deformation and pressure distribution of surrounding rock along the longitudinal,transverse and radial directions of the tunnel and the stress distribution of the lining structure under various working conditions are analyzed. |
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