Optimization Study On The Initial Of Railway Tunnel

The south central railway channel in Shanxi province is the first railway whose design axle loadis 30 tons in our country.Taking the Xi Tieche No.2 tunnel of this railway channel for background, tunnel supporting parameters was studied. Firstly, based on theanalysisof monitoring data, the existing supporting parameters were assessed using displacement class managementand the calculationparameters of finite element were optimized.Secondly, the deformation tendency of surrounding rock of unexcavated section was forecasted using finite element, then, the present supporting parameters were assessedand, combined geological predication,the rationalization proposal for the optimization of support scheme was put forward. Based on the analysis of site monitoring data and finite elementsimulation, the following conclusions were got.(1) The application of displacement class management in the construction of Xi Tieche No. 2 tunnel was feasible.Displacement class management could be used for the safety management of tunnel construction and assessment of support effect, and it also could be used for the direction of construction.(2) Although there was deviation between finite elementsimulation and monitoring data, the results of finite elementsimulation was reliable. The deformation of unexcavated tunnel could be forecasted by numerical analysis.(3) Based on the results analysis of finite element, the supporting parametersof Xi Tieche No.2 tunnel were weak fromDK 1079+280 to DK1079+200. So the supporting parameters of the section need to be designed again to meet the strength requirement of primary support.(4)The strengthof supporting parametersof New Austrian tunnelling method had a direct influence on the deformation after the tunnel excavated, and primary support played an important role in control of tunneldeformation, and reasonable supporting parameters could control the deformation of surrounding rock and guarantee the safety of tunnel. Through the finite elementsimulation, it could be concluded that under moderately weathered limestone condition, the 116 section steel should be used and the spacing between section steels was 1.2m. The length of the bolt was 3.0m and the spacing between bolts along longitudinal direction and toroidal direction was 1.2m. The thickness of sprayed concrete of buttress was 18cm and the thickness of sprayed concrete of inverted arch was 10cm. The use of aforementionedprimary supportparameters could effectively control the deformation of surrounding rock and the second level management of displacement could be realized. With the setting of advanced small pipe, normal construction could be realized. The use of aforementionedprimary supportparameters had good economic benefits and no support material was wasted.