Propagation Characteristics Of Subway-induced Vibrations

With the continuous advancement of urbanization,the urban land is becoming more and more strained,and the old village renovation project in the city arises at the historic moment.The old reform project is widely supported because it can effectively solve public problems that restrict local development,including the backward villages supporting public facilities,poor public security,poor environmental governance,and hard fire hazards.However,there are still a great number of problems in advancing the process of replacing the old projects.The environmental vibration problem caused by the operation of subway is one of the problems.Pre-planned subway lines usually pass through areas with relatively shallow building foundations such as villages in the city.Therefore,it is necessary to consider whether the pile foundation of super high-rise buildings will increase the environmental vibration response caused by subway vibration and affect the normal life of residents when implementing the old renovation.Field tests and numerical simulation based on 2.5-dimensional FEM-PML finite element substructure method are conducted in this paper,and the propagation characteristics of subway train-induced vibration in the soil layer are studied.The main work of this paper is presented as follows:(1)The soil dynamic parameters of a segment of Guangzhou Metro Line 3 were tested in situ,the principle of seismic refraction method(SR)was studied,and the compression(P)wave velocity of soil layer was obtained.Moreover,the process of using the multi-channel surface wave method(MASW)for extracting the dispersion curve by F-K method and obtaining the shear wave velocity was presented.(2)Field measurement of the vibration caused by the train of Guangzhou Metro Line 3 in the subway tunnel,advanced borehole and the ground surface was carried out.The whole process of the subway vibration propagating from the tunnel to the soil layer at different depths and then to the ground surface was studied,and the propagation characteristics of subway vibration in the soil layer were summarized.(3)Relevant formulas of the 2.5-D finite element and PML boundary are derived,and the governing equations of the 2.5-D FEM-PML coupling element are further derived.(4)The vibration caused by subway train was simulated by the 2.5-dimensional FE-PML substructure method.The soil model was established based on the 2.5-dimensional FEM-PML element deduced above,and the relevant dynamic parameters required by the model were also measured by the above in-situ test.Each train model is equivalent to a 10-DOF model.The track model simplifies the track-soil contact surface to a strip foundation,and establishes the transfer function of the strip foundation response caused by the track displacement.The reliability of the 2.5-dimensional FE-PML substructure method for simulation of the vibration of subway train is demonstrated in comparison to the actual vibration data.