Study On Vibration Measurement And Numerical Simulation Of A Test Section Of A Subway Viscoelastic Damping Track Bed

The problem of environmental vibration induced by subway operation is becoming more and more prominent.Viscoelastic damping track bed is a new method to reduce vibration.It is of certain value to study the vibration measurement and numerical simulation of subway projects using viscoelastic damped ballast bed.This paper uses a combination of field measurement and numerical simulation,to apply the two test sections of the viscoelastic damper bed(damping section A and damping section B,damping layer thicknesses are 3mm and 5mm respectively)and their corresponding common track bed sections(named blank section A and blank section B respectively Paragraph)is the research object.On the basis of the study on the conventional and dynamic mechanical properties of the viscoelastic damping material qtech-118 used in the two test sections(hereinafter referred to as T118 material),the field construction of viscoelastic damping track bed was carried out,and the vibration reduction effects of viscoelastic damping track bed in the two test sections were compared through the vibration measurement.Finally,ANSYS simulation software was used to preliminarily explore the influence of thickness change of damping layer on damping performance of viscoelastic dampeing track bed,and the attenuation characteristics of ground Z vibration level were analyzed as a supplement and verification to field test.First,the research on the general properties of T118 materials shows that the drying time,tensile strength,elongation at break,tear strength,adhesion properties,solid content and hardness of the material meet the requirements of engineering applications.The research on the dynamic mechanical properties of T118 material shows that temperature has a great influence on the storage modulus,loss modulus and loss factor of the material,but the frequency is not significant.In the temperature range of-15～40℃(The subway operating environment temperature),the material loss factor 0.12～0.54.Second,the construction process of the viscoelastic damping track bed is formulated,which mainly includes the cleaning of the base layer,painting of special primer,spraying of T118 material,inspection and repair,erection of rails,and pouring of concrete track bed.Because the damping performance of T118 material is greatly affected by temperature,field vibration tests were performed on the two test sections of the viscoelastic damping track bed and their corresponding normal passage bed sections in winter and summer,respectively.Third,the field vibration data of two test sections and the corresponding ordinary section of the track bed with viscoelastic damping are compared and analyzed.The results show that compared with the blank A section,the maximum peak value and effective value of the vibration acceleration in the damping A section decreased by 4.3%～20.5% and 4.1%～8.0%,respectively.The vibration level in the frequency range of 1～50Hz decreased by 0.41～6.38 d B,and the Z vibration level decreased by 1.21～3.88 d B.Compared with blank section B,the maximum peak value of vibration acceleration in damped section B decreased by 4.2%～18.7%,the effective value decreased by 3.6%～8.8%,and the maximum vibration level decreased by 5.29 d B in the frequency range of 1～63Hz,Z vibration level decreased by 1.15～ 4.22 d B,And the vibration difference between the two test sections and the corresponding ordinary bed section is greater in summer than in winter.Therefore,it can be shown that the application of viscoelastic damping ballast bed has certain damping effect,and the damping effect in summer is better than that in winter.Finally,a three-dimensional finite element model of the track bed-bridge-soil layer is established based on the engineering parameters of the damping section A,and the influence of the thickness of the damping layer on the vibration is analyzed.The results show that as the thickness of the damping layer increases,the damping performance of the viscoelastic damping track bed Lifting,comprehensive consideration of vibration reduction effect and engineering cost,5mm is the optimal thickness of the damping layer in the experimental section of the research project.The analysis of the ground vibration attenuation law shows that the soil within 10～40m from the centerline of the line attenuates the ground vibration faster,while the soil outside 40 m will slow down the attenuation of the ground vibration.