Field Tests on Ground Vibration Caused by Viaduct Rail Transit under Mountainous Terrain Conditions

Considering the influence of terrain on the vibration attenuation of rail transit,field tests were carried out on the viaduct section of Chongqing Light Rail Line 6 passing through typical slopes and cliffs.The vibration Spectrum characteristics and the attenuation of vibration velocity level in three directions are analyzed,including 0,45,and 90 degrees from the track center line.The results show that the main frequencies of ground vibration caused by trains are distributed around 50 Hz and the frequency distribution at various distance is not affected by terrain.Ground vibration will be amplified greatly when it is transmitted from the pier cap to the surrounding soil.The decrease of vibration is slower along slope and steep cliff than that on the plane,which decays obviously and then slowly on the plane.However,it decays slowly and then quickly on the slope.At the same time,the ground vibration shows fluctuation with distance attenuation.There is a vibration amplification zone near the distance of 13 m in