| When a high-speed train enters a tunnel,the air between the train and the tunnel is severely compressed,forming a reciprocating air pressure wave inside the tunnel.The initial compression wave propagates to the tunnel entrance and generates a micro pressure wave.With the continuous improvement of train operation speed,the aerodynamic effect of micro pressure waves at the tunnel entrance becomes increasingly significant.In severe cases,resonance can form in light structures(such as doors,windows,etc.)and human cavities near the tunnel entrance,endangering building safety and the physical and mental health of residents.It is crucial for the design of high-speed railway tunnels to reveal the propagation characteristics of tunnel pressure waves and the variation pattern of micro pressure wave amplitude under the influence of factors such as tunnel clearance area and portal connection section,and to clarify the common relief structure types and the relief effect of auxiliary tunnels in long tunnels on tunnel aerodynamic effects.This article focuses on the aerodynamic effects of high-speed railway tunnels at speeds ranging from 250 km/h to 350 km/h,and conducts a series of numerical simulation and actual vehicle testing research on the propagation characteristics and mitigation measures of pressure waves and micro pressure waves inside the tunnel.The propagation characteristics of air pressure waves in tunnels and micro pressure waves at the entrance of high-speed railways at speeds ranging from 250 km/h to 350 km/h were analyzed.The influence rules of factors such as tunnel clearance area and entrance connection section on the initial compression wave pressure peak,pressure gradient peak,and micro pressure wave amplitude at the entrance were revealed.Subsequently,based on the research and analysis of domestic and international relief structure types and micro pressure wave relief measures,the common relief structure types at tunnel entrances and the relief effect of auxiliary tunnels in long tunnels on tunnel aerodynamic effects were studied.(1)A quantitative study was conducted on the influence of different tunnel clearance areas on the amplitude of tunnel pressure waves and micro pressure waves under the speed conditions of 250 km/h～350 km/h on high-speed railways.When the train passes through tunnels with different headroom areas at the same speed,the relationship between the peak value of head wave pressure and the tunnel headroom area at 50 m of the tunnel entrance measurement point is a 1.2 power Power function,and the relationship between the peak value of head wave pressure gradient and the tunnel headroom area is a 1.5power Power function.The amplitude of the micro pressure wave is limited compared to the peak amplitude of the first wave pressure gradient at the tunnel exit.When the train speed is 250 km/h,the tunnel clearance area ranges from 92 m~2Reduce to 60 meters~2At that time,the peak increase in pressure gradient inside the tunnel was 85.2%,and the increase in micro pressure wave at the entrance was 23%.When the train speed is 300km/h,the tunnel clearance area changes from 100 meters~2Reduce to 80 meters~2At that time,the peak increase in pressure gradient inside the tunnel was 39.4%,and the increase in micro pressure wave at the entrance was 11.8%.When the train speed is 350 km/h,the tunnel clearance area changes from 100 meters~2Reduce to 80 meters~2At that time,the peak increase in pressure gradient inside the tunnel was 40.0%,and the increase in micro pressure wave at the entrance was 13.7%.(2)Combined with Yamamoto micro pressure wave calculation model and numerical simulation method,the influence of the spatial Solid angle of the tunnel portal junction on the amplitude of micro pressure wave was quantitatively studied.When the height of the embankment connection section is 0 m～20 m,the Solid angleΩ(20 m)of the embankment space changes from 1.57πto 1.73π,and the micro pressure wave at the tunnel entrance 20 m decreases by 12.7%.When the height of the cutting connection section is 0 m～20 m,the cutting space Solid angleΩ(20 m)changes from 1.57πto 1.42π,and the amplitude of micro pressure wave at 20 m of the tunnel portal is 23.5%.When the height of the bridge connecting section is 0 m～50 m,the Solid angle of the bridge space changes from 1.57πto 2.00π,and the amplitude of the micro pressure wave at 20m of the tunnel portal decreases by 22.6%.(3)Clarified the relief effect of common relief structures at tunnel entrances on the amplitude of micro pressure waves under different speed conditions.Research has found that the position of the opening has a significant impact on the relief effect of micro pressure waves.For the type of relief structure tested in the article,when the opening rates of the inlet and outlet relief structures are consistent(both opening rates are 9.0%),the relief rate of the top opening relief structure on the amplitude of micro pressure waves is 1.42 times that of the side opening relief structure.When the opening position is at the top,extending the length of the relief structure has a more significant relief effect on the micro pressure wave at the opening.The relief structure with a test length of 38 meters(opening rate of 9.0%)has a relief rate of 77.1%on the amplitude of the micro pressure wave.(4)Based on on-site vehicle tests,the influence of auxiliary tunnels in long tunnels on the aerodynamic effect of the tunnel was revealed.Under the Ballastless track slab,when the tunnel length exceeds 1.5 km,it is necessary to consider the"intensification"effect of the tunnel length on the micro pressure wave.After dimensionless processing of the data,the relationship between the amplitude of micro pressure waves and train speed and tunnel length is~*1.065(1~*~*.When the propagation distance is about11.0 km,the peak pressure gradient reaches its maximum value.When the auxiliary tunnel is located before the peak pressure gradient of the first wave reaches its maximum value,the auxiliary tunnel can effectively reduce the peak pressure gradient of the first wave and the amplitude of the micro pressure wave;On the contrary,when the auxiliary tunnel is located at the position where the peak pressure gradient of the first wave reaches its maximum value,the relief effect of the auxiliary tunnel is very limited.For the long tunnel tested in the paper,the maximum relief rate of the auxiliary tunnel on the peak pressure gradient of the first wave is 27.5%. |
