| Under the combined action of construction disturbances,hydrogeology,construction defects,and other factors,shield tunnels operating in soft soil areas inevitably produce uneven settlement diseases.Tunnel settlement can cause deformation of lining segments,which is transmitted to the track structure through interlayer interaction,leading to changes in the geometric shape and stress of the track structure.When trains pass by,the interaction between wheels and rails is intensified,affecting driving stability and comfort.In severe cases,it may endanger driving safety.Therefore,it is of great significance to study the influence of uneven settlement of shield tunnels on the mechanical characteristics of vehicle-track systems.Based on track calculation theory and finite element method,a static model of track-tunnel lining is established.Using a static analysis model,the displacement and stress changes of the track structure under two types of settlement diseases,longitudinal uneven settlement and segment dislocation,were studied,fully taking into account the interlayer contact characteristics between the track bed and the lining.The research results show that:(1)The longitudinal uneven settlement of shield tunnels has a significant impact on the deformation of the track structure.The track structure undergoes a following deformation under the action of dead load and settlement,and as the settlement waveform changes,the track structure and tunnel lining experience a void phenomenon.Under the condition of a wavelength of 15 m,when the settlement amplitude exceeds 15 mm,the void is obvious.The maximum longitudinal stress of the track structure increases with the increase of settlement amplitude,first increases and then decreases with the increase of settlement wavelength.Longitudinal uneven settlement has a significant impact on the longitudinal tensile stress of the track structure.Excessive longitudinal tensile stress can cause damage to the monolithic track bed,leading to various track diseases.(2)Shield tunnel segment misalignment has a significant impact on rail surface displacement,and the deformation ratio between the peak rail surface displacement and segment misalignment basically varies by 1:1.The maximum longitudinal tensile stress of the track structure increases linearly with the increase of the amount of dislocation.When the amount of dislocation exceeds 10 mm,the maximum longitudinal tensile stress of the track bed exceeds the design value of the concrete tensile strength,which can cause the track bed to crack.Based on the vehicle-track coupling theory,a dynamic analysis model of vehicle-tracktunnel lining is established.Considering the superimposed effect of additional irregularities caused by settlement and random track irregularities,the dynamic effects of uneven settlement of shield tunnels on the vehicle-track system under different working conditions are analyzed.The research results show that:(1)When the longitudinal uneven settlement center is located at the end of the track bed,the impact on the dynamic response of the vehicle-track system is greater.The dynamic response of the vehicle-track system increases with the increase of the settlement amplitude and driving speed,and first increases and then decreases with the increase of the settlement wavelength.In summary,under the action of vehicle dynamic loads,changes in the settlement waveform have a significant impact on the vertical acceleration of the vehicle body,the vertical force of the wheel track,and the wheel load reduction rate,while they have a small impact on the lateral acceleration of the vehicle body,the lateral force of the wheel track,and the derailment coefficient.According to the evaluation indicators of driving safety and stability,when the settlement wavelength is taken as 10 m,the settlement amount should be less than 30mm;When the settlement wavelength is 15 m,the settlement amount should be less than25mm;When the settlement wavelength is taken as 20 m,25m,and 30 m,the settlement amount should be less than 20 mm.(2)The amount of segment misalignment has a significant impact on vehicle safety and comfort.When the amount of segment misalignment reaches 15 mm,the vertical acceleration of the vehicle body has exceeded the limit,and the wheel load reduction rate has exceeded the safety limit.On this basis,the impact of driving speed on vehicle safety and stability when the amount of segment misalignment is 15 mm is further discussed.From the calculation,it can be seen that when the amount of segment misalignment is 15 mm,the driving speed that meets the vehicle safety requirements is 40 km/h. |
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