Analysis Of Ambient Vibration Response Induced By Operation Of Subway Train On Curved Rail Segment With Small Curvature Radius

The torsional effect of the subway train's curved rail segment intensifies the environmental ambient vibration response induced by the train operation.With the example of a curved section of Hangzhou Metro line 1,this thesis establishes a vehicle-track model by using a multi-body dynamics software SIMPACK to calculate the dynamic wheel-rail force when Type B vehicles pass a small radius of curvature of 350m.Through field measurement and numerical simulation,the vibration response of the ground and adjacent low-rise buildings induced by different subway operating conditions are analyzed under clay and sand conditions.Some vibration reduction measures and recommendation are given in regard of controlling train speed,setting isolation trenches,underground continuous walls,and sensitivity of soil parameters,etc.Conclusions are listed as below:1)Compared with the subway train operation in the straight section,the vibration behavior in the curve section is more complicated.At this time,the horizontal effect of the wheel train is not negligible.2)When the train is running,the peak value of the acceleration curve of each measuring point on the ground is in the order of 10-2m/s2,much larger than the background vibration of 10-4m/s2,With the increase of the distance from the measuring point to the centerline of the tunnel,the vibration response of the ground gradually decreases,mainly dominated by low frequency up to 30Hz.3)The vibration of a building caused by the operation of the subway is dominated by low-frequency vibrations within 10 Hz both horizontally and vertically.When the tunnel passes through sand or clay formations,the vertical acceleration does not change much with the increase of floors.The vibration acceleration in the horizontal direction shows a significant raise with the increase of floors.Secondary vibrations in the horizontal direction have a clear amplification effect on high floors.4)Compared with the same working conditions,the vibration response of the ground structure on the sand layer is much larger than that of the clay layer.In the horizontal direction,the peak vibration acceleration under condition of sand is generally 0.0175-0.03m/s2 higher than that of clay.In the vertical direction,the peak acceleration under condition of sand is basically 0.03-0.05m/s2 higher than that of clay.Compared with the horizontal acceleration peak values,the vertical acceleration peak values of the two kinds of soils do not change much with the increase of the floor level.5)Deceleration of the train through the local sensitivity strategy controlled by the ATO system can effectively reduce the vibration response of the building.The vibration reduction effect of underground continuous wall is not ideal as the vibration amplification even appears on a certain floor.Empty trench has better vibration reduction effect,especially for horizontal vibration;The magnitude of the vibration acceleration peak is inversely proportional to the shear modulus,and tends to decrease linearly with the increase of the soil damping ratio.