Effect of connected buffer structure on micro-pressure waves in 400 km/h high-speed railway tunnel
With the further increase of the running speed of high-speed trains,the amplitude of the micro-pressure wave(MPW)at the tunnel exit increases dramatically,and the strong blasting noise affects both the surrounding environment and the normal life of nearby residents.The mitigation effect of a connected buffer structure consisting of parallel headings and cross passages on MPWs in 400 km/h high speed railway tunnel was investigated.Firstly,a 400 km/h moving model test was conducted to verify the accuracy of the calculation method.Secondly,the RNG k-ε turbulence model and sliding mesh method were used to analyze the effects of the distance between the location of the connected buffer structure and the tunnel entrance D and the length of the connected buffer structure L on MPWs.The results show that the mitigation rate of the MPW gradually increases with the increase of the D and reaches the optimum at D=25 m,and the MPW amplitude decreases by about 34.4%.As the L increases,the MPW amplitude increases slowly.When L=30 m,the MPW amplitude at 20 m of the tunnel exit is 91 Pa,and the mitigation rate is 37.1%.The combination of the connected structure and the buffer structure with a hole at the top of the expanded section on the existing 350 km/h high-speed rail line can reduce the MPW amplitude at 20 m from the tunnel exit to 47.3 Pa,with a mitigation rate of about 67.3%.The connected buffer structure studied in this paper makes reasonable use of the parallel heading left over from the tunnel construction,which can significantly reduce MPWs and protect the tunnel surroundings in guaranteeing almost constant construction costs.
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