Study On Mechanical Properties Of Lining Structure Under Aerodynamic Load Of High-speed Train

As the speed of the high-speed train increases,the aerodynamic effect inside the tunnel becomes more significant and the air flow inside the tunnel becomes more intense.As the air is compressed or stretched,aerodynamic pressure will act on the lining,which will have adverse effects on the lining structure in the long term.Due to the characteristics of concrete,there tends to be a lot of existing cracks in the lining structure.Then,the gas pressure acts as a cyclic load on the lining structure,potentially resulting in the fatigue failure of the structure.This study is to exploring the long-term effect of aerodynamic effect on lining structure under the condition of existing cracks as high-speed train passes through tunnel.Firstly,a tunnel-air-train coupling model is established by using FLUENT fluid mechanics analysis software,and the aerodynamic effect of high-speed train passing through high-speed railway tunnel is simulated.The parameters of the model are calibrated reasonably and the reliability of the numerical model is proved.By changing the train speed,the aerodynamic effect in the tunnel under different speed is obtained.It is found that the pressure history curves of different measuring points in the same section have basically the same trend with a little difference in value.Second,taking the high-speed rail tunnel at the depth of 30 m as the research object,using the obtained aerodynamic load,mechanic response of the lining with existing cracks is analyzed when the train is at different speed.It is found that lining structure has been disturbed along the passing of train and the crack tip maximum principal stress variation trend is the same as the aerodynamic load.Then,based on the surrounding rock pressure data of 83 high-speed railway tunnel sections,the distribution of tunnel buried depth and lateral pressure coefficient is analyzed.Taking the 350 km/h high-speed trains as the research object,considering the different buried depth and lateral pressure coefficient,the finite element model is established to simulate the mechanical response of the tunnel lining structure at different depth under aerodynamic pressure.It is found that compared to ground stress,the effects caused by aerodynamic load are less intense.With the increase of the lateral pressure coefficient,the maximum principal stress at the crack tip decreases gradually at arch vault and arch shoulder,and increases at side wall.Next,taking the high-speed railway tunnel at the depth of 30 m and 350 km/h high-speed train as the research object,considering existing cracks of different positions and different lengths,finite element model is established to simulate mechanical response of lining structure.By changing the crack location and length,maximum principal stress and the maximum principal stress amplitude at crack tips are obtained.The maximum principal stress and the maximum principal stress amplitude of the crack tip are used as the criterion for the crack propagation.Taking the high-speed railway tunnel with a depth of 30 m and 350 km/h high-speed train as the research object,the paper analyzes the existing cracks in the lining structure.It is found that the change of crack location,crack number and crack length has a little influence on the maximum principal stress at the crack tip,which can be ignored.Finally,according to the concrete fatigue equation and linear damage theory,the fatigue life of lining structure with existing cracks is analyzed.The history curve of maximum principle stress is partitioned and fatigue damage of different stress level is calculated.It is found that under the long-term effect of aerodynamic pressure,the fatigue life of the lining structure is more than 100 years,which meets the design requirements.This paper involves 117 figures,37 tables and 61 references.