Experimental Study On The Judgment Of Terrain Bias Tunneling And The Stability Analysis Of Econdary Lining

Due to the numerous mountains and the large range of terrain height in China,the demand for infrastructure is increasing.Because the continuous construction of highways,tunnel engineering is widely used to overcome height differences.There are many researches on tunnel design and construction,but few studies on tunnels under complex conditions,such as terrain bias tunnels.The asymmetric load acting on the lining structure is the standard for determining the bias tunnel.At present,the criteria for the determination of highway bias tunnels are the same as those for railway tunnels.However,highway tunnels are different in structure design and span from railway tunnels,which lead to error.The article is based on the Huitougou Tunnel in Hegang-Dalian Expressway,study the determination of terrain bias tunnel and stability of secondary lining under different bias degrees.(1)Making a tunnel model based on similar principles,apply pressure to the tunnel model using 8 sets of jacks to simulate different terrain bias conditions.Monitoring the surrounding rock pressure under different bias conditions,the pressure between the primary lining and the secondary lining.The bias coefficient is defined by the radial stress of the surrounding rock at the symmetrical position of the tunnel.The bias voltage is an indicator of the degree of tunnel bias.According to the bias coefficient varies with tunnel depth and ground slope angle,simulating the change of plastic zone under different tunnel depth and ground slope angle and making the table of terrain bias tunnel bias degree determination.(2)The load structure method is used to analyze the stability and deformation of the two liners under different bias degrees.Analyzing the stability of it and we can conclude that slightly biased and little serious biased units can meet design requirements,unstable units exist in secondary lining under severe bias conditions,which are mainly exist in the vault and deep buried side arches.The horizontal maximum displacement and the vertical maximum displacement become larger as the degree of bias increases,the vertical maximum displacement occurs in the dome,andthe horizontal maximum displacement occurs in the deep buried side arch.(3)Analyzing the stability and deformation of different thicknesses secondary lining under the case of severe bias,concluding the relationship between the safety factor of the second lining increases with the increase of the thickness of the second lining,the maximum value of the horizontal displacement and the maximum value of the vertical displacement become smaller as the thickness of the second lining increases.Using finite element calculate the secondary lining reinforcement which meet the constraints and design requirements.Establishing a comprehensive cost objective function and finding the economical and safe design method of different secondary lining thickness under severe bias conditions.