| High-speed railways are developing rapidly in our country.Due to terrain constraints,many high-speed railway tunnels had to be built to meet the requirements of high-speed trains.High-speed trains will cause violent pressure fluctuations when passing through the tunnel,which will have a strong aerodynamic impact on the lining structure and ancillary facilities of the tunnel.Under the action of pressure waves,micro-cracks in the tunnel support structure will gradually develop into macro-cracks,and then block falling will occur under the triggering action of aerodynamic or vibration effects,which will bury hidden dangers for the safe operation of high-speed trains in the tunnel and seriously affect the structure.The durability.At the same time,the pressure wave will also cause aerodynamic fatigue damage to the fixed equipment in the tunnel,thereby shortening the service life of the equipment,and in serious cases,it will threaten the safety of train operation.In this paper,a one-dimensional unsteady compressible unequal entropic flow model and a generalized Riemann variable characteristic line method are used,combined with the current situation of high-speed railway departments planning to increase train operating speed,and the aerodynamic load distribution characteristics,aerodynamic load maximum values and differences in high-speed railway tunnels are developed.The analysis of the influence of factors on the aerodynamic load and other aspects reveals the characteristics of the aerodynamic load changes in the tunnel and the law of amplitude changes,which has reference value for improving the structural construction in the tunnel and the strength of auxiliary facilities.The research conclusions are as follows:(1)Pressure waves are induced when the train enters the tunnel.The pressure wave propagates towards the exit end of the tunnel at the local speed of sound and reflects back to the abnormal wave.These pressure waves are repeatedly reflected and superimposed in the tunnel to form a complex pressure wave system,and continue to propagate after the train leaves the tunnel.The pressure wave will gradually attenuate due to the friction between the tunnel wall and the rails.These factors finally formed pressure waves at different measuring points in the tunnel.The decay time of the aerodynamic load in the tunnel increases as the length of the tunnel increases.(2)According to the length,the tunnels are divided into three types: short tunnel,medium-long tunnel and long tunnel.In combination with actual engineering applications,the typical lengths of 500 m,1500m and 7000 m among the short,medium and long tunnels are selected for research.Five typical measuring points are set in the tunnel,including the measuring point near the entrance of the tunnel,the central measuring point of the tunnel,the measuring point near the exit of the tunnel,the inner measuring point of the tunnel entrance and the inner measuring point of the tunnel exit.The influence characteristics of tunnel length,train speed and train marshalling length on the aerodynamic load of typical measuring points in the tunnel are studied respectively.Research shows that for the measuring points near the entrance of the tunnel,the central measuring point of the tunnel,and the measuring point near the exit of the tunnel,the pressure time history curve changes at different measuring points in the same tunnel are roughly the same when the train passes through the tunnel.The pressure at the measuring point near the entrance of the tunnel rises first.The pressure at the measuring point near the exit of the tunnel begins to decay periodically;for the measuring point at the entrance of the tunnel and the measuring point at the exit of the tunnel,when the train passes through the tunnel,the pressure at the measuring point at the entrance and exit of the same tunnel changes drastically,and the pressure time history The curve presents many line segments that resemble vertical lines.After the train leaves the tunnel,the pressure attenuation amplitude of the measuring point inside the tunnel exit is greater than the amplitude of the measuring point inside the tunnel entrance.(3)In short tunnels,medium-long tunnels and long tunnels,taking the typical tunnel length as an example,a measuring point is arranged every 10 m,20m and 50 m in the tunnel from the entrance of the tunnel,and the measurement points at each measuring point in the tunnel are recorded.Pressure change data.Calculate the maximum pressure values of all measuring points in the tunnel in the data file,obtain the maximum positive and negative pressure values and maximum pressure peak-to-peak values of each measuring point in the tunnel,and study the maximum positive and negative pressure values and maximum pressure peaks of each measuring point in the tunnel The distribution of peaks along the length of the tunnel,and the influence characteristics of tunnel length,train speed and train marshalling length on the distribution of the maximum value of each measuring point in the tunnel.Research shows that the maximum positive pressure value of each measuring point in the tunnel increases first and then decreases as the distance between the measuring point and the tunnel entrance increases.The maximum negative pressure value and maximum pressure peak-to-peak value of each measuring point in the tunnel fluctuates with the increase of the distance between the measuring point and the entrance of the tunnel,and both obtain the maximum value near the central measuring point of the tunnel,and then start to decrease.(4)In short tunnels,medium-long tunnels and long tunnels,with the tunnel length interval of 10 m,20m and 50 m,calculate and count the maximum pressure of each measuring point in the tunnel under different tunnel lengths,and then measure the pressure of each tunnel in the tunnel.Take the maximum value of the point pressure to get the maximum value in the tunnel.Research the characteristics of the influence of tunnel length,train speed and train marshalling length on the maximum value distribution in the tunnel.Studies have shown that in the short tunnel section,the maximum positive and negative pressure values and maximum pressure peak-to-peak values of tunnels of different lengths increase with the increase of the tunnel length;in the medium and long tunnel section,the maximum positive pressure values of tunnels of different lengths First increase with the increase of the tunnel length,and then remain unchanged;the maximum negative pressure value and maximum pressure peak-to-peak value of the tunnels of different lengths first increase and then decrease with the increase of the tunnel length;in the long tunnel section Inside,the maximum positive pressure value of tunnels of different lengths remains unchanged with the increase of tunnel length,and the maximum negative pressure value and maximum pressure peak-to-peak value of tunnels of different lengths decrease with the increase of tunnel length.This paper systematically studied the basic characteristics and changes of the tunnel pressure wave and the tunnel aerodynamic load under the condition of a single train passing by a high-speed railway at a speed of 400 kilometers per hour,which made up for the current domestic research on the aerodynamic load of a 400 kilometers tunnel.It is the tunnel lining structure.It provides a basis for the determination of loads for aerodynamic fatigue design of fixed equipment in the cave,and the research results have practical engineering application value. |
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