Study On Analytical Model Of Coupled Vehical & Track And Effect To Environment By Metro Train-Induced Vibrations

Along with the fast growth of the rail transit network, the metro train induced ground-borne vibration is more and more seriously concerned as most of the line pass under through densely inhabited district, especially to nearby residents, sensitive instrumentations, historic buildings and adjacent structures etc.The problem of the vibration generated by urban rail transit can be seen as an integrated system of vehicle-track-tunnel-stratum, which can be studied from the following sub-systems: vehicles, tracks, tunnel linings, soil strata. Thereinto, vehicle-unsprung mass directly influence on contact forces between wheel and rail, which is the main excitation source of vibrations; while tunnel linings and soil strata are the main mediums for vibration propagation. The sub-systems mentioned above are of interacting and intercoupling, which makes this problem to be extremely complicated. Therefore, it is difficult to evaluate and predict the metro train-induced vibration by only one method; good results should be attained by combination of theoretic analysis, field measurement, empirical estimation and numerical simulation efficiently.This Ph.D thesis is supported by the projects of Natural Science Foundation of China named Research on the Environmental Vibration Induced by Urban Rail Transit and its Countermeasure (No:50538010) and Research on the Numerical Prediction Models for Dynamic Responses of Tunnel and Free Field Ground by Running Metro Trains (No:50848046). Firstly, by the methods of theoretic analysis, an analytical model of coupled with vehicle-track is established. Furthermore, according to the field measurement of ground-borne response of metro Line 5 in Beijing, 3D dynamic FE models are created by software MIDAS/GTS, which to validate and verify the veracity and reliability of analytical and numerical models, and to analyze the vibration propagation for the ground-borne vibration; Finally, through the orthogonal test and numerical simulation method, 9 dynamic loads and 3D FE models are established to study the influence on ground-borne vibration of different factors and parameters . The main achievements include:(1) An analytical model system coupled with vehicle & track is established. In this system, the factors of a whole vehicle model, infinite track structure, track irregularity and wheel-rail Hertz contact are all taken into account. In the infinite track structure, based on the periodicity of sleepers, the integral problem in boundless time-space domain has been transferred to a superposition problem with "coupled vehicle and track basic cell" in frequency domain. Moreover, an analytical solution of dynamic response at random receiver point on tracks is derived, which can get from a general theoretical model for dynamic vehicle load of any vehicle speeds, any vehicle types and any track structures. The whole solving process is based on analytical derivation and every physical quantity is represented by matrixes and vectors. The process is finished in wave number-frequency domain, which provides great convenience for analyzing the frequency characteristic of whole dynamic system.(2) A complete software package TMCVT is programmed. Compared with in-situ measurement values, the results calculated by TMCVT are proved to be correct. Thereby, TMCVT can be used to study the problem of dynamic interaction with vehicle and track.(3) The main objective of this paper is to describe the results of in situ measurements about ground-borne vibration that have been performed with three different line status (curve, adjust curve, straight line), two different mitigation measures (simple DTVI2 fastener, Vanguard fastener) at three sites of Beijing metro Line 5 (Songjiazhuang-Liujiayao). Especially the time history and frequency properties of the vibration were been studied. And then, a tunnel-stratum 3D FE model is built and caculated, which ground-borne vibration responses are analyzed and simulated from different viewpoints, including time domain, frequency domain and vibration attenuation regulation. Compared with the in-situ measurement values, the calculated results are proved to be correct and the vehicle-track-tunnel-stratum model is also to be reliable and reasonable.(4) According to the theoretical model and FEM which mentioned above, an orthogonal test table under 4 factors and 3 levels is designed for analyzing different influence factors on the train-induced ground vibration. Nine analytical dynamic forces are applied on the tunnel-stratum FE models to simulate and study the the ground borne vibration. From different points including time domain, frequency domain and vibration attenuation regulation, the dynamic responses on ground surface and the propagation regulation are obtained and analyzed. Furthermore, the influence degree of different parameters (embedded depth of track surface, type of fastener, vehicle speed and tunnel form) to ground-borne vibration has also been presented.