Study On The Prediction Of Metro Train-induced Vibrations Based On Sensitivity Of Environmental Influence And Design Stage-Accompanied Evaluation System

ABSTRACT:In recent years, with the development of urban rail transit network, more and more attentions have been paid to the subway train-induced vibrations and their influences on residents, historic buildings and precision instruments nearby. Moreover, some vibration-sensitive objects have already been bottlenecks which restrict the planning and construction of the whole subway line. Therefore it is especially important to predict vibration responses accurately and evaluate their influences correctly before the subway is open to operate. At present, however, there are many problems for the evaluation of environmental influences to vibration-sensitive objects and for the vibration mitigation design. For instance, there is no integrated theoretical system, and the means are single. It is lack of prediction&evaluation system accompanied with design stages. Furthermore, metro global mitigation is wrongly simplified as track mitigation only.In order to solve these problems mentioned above, in this thesis, the core concept of sensitivity of metro train-induced vibration and its environmental influence (sensitivity for short) is originally proposed. Based on this core concept, the Design Stage-Accompanied Environmental Evaluation System (defined as DSA-EE System) for metro train-induced vibration is also firstly put forward. By definition of concept of sensitivity, two interaction variables vibration bearing capability and vibration disturbance intensity become unified. Based on the detail review of existing evaluation methods, prediction methods, propagation laws of metro train-induced vibrations at home and abroad, some prediction methods in the DSA-EE System is proposed. In addition, by analyzing the sensitivity for residents, historic buildings and sensitive instruments, some valuable conclusions have been drawn. Relative problems in the DSA-EE System are discussed, and by measurement researches and numerical calculations, prediction steps and methods are improved as well.In this thesis, by analyzing the sensitivity for residents, historic buildings and sensitive instruments as a core content, and by predicting and evaluating the subway train-induced vibrations and their influences as a main clue, six aspects of innovative researches have been performed with the help of criteria study, theoretical analysis, measurement analysis and numerical calculation. Finally, the achievements obtained are as follows: (1) The concept of sensitivity and its mathematical definition, calculation method, classification and its matrix form are originally proposed, which provides a theoretical foundation for metro global mitigation and DSA-EE.(2) Based on the calculation and analysis of sensitivity, DSA-EE System for metro train-induced vibrations is proposed, which integrates the advantages of different vibration prediction methods.(3) A new classification of vibration control is suggested for historic buildings against traffic-induced micro vibrations. Based on the existing research results in National Code GB/T50452-2008, a vibration limit degradation method for historic buildings is proposed, in which the factors of repair, strengthening and protection for historic buildings are considered.(4) By analyzing a large number of site measurement data of metro train-induced vibrations, the results of preliminary sensitivity estimation are obtained.(5) By numerical simulation, train loads for five different kinds of tracks are obtained.(6) The representation methods for sensitivity matrix and track-form selection matrix are proposed, in which the factors of vibration criteria, soil layers, track-forms, tunnel depth, and horizontal distance are considered. With the help of numerical simulation, the results of sensitivity matrix and track-form selection matrix for residents, historic buildings and sensitive instruments are obtained.(7) The analytical model of a vertical harmonic load applying on a layered half-space is built. By this model, the causes of formation and laws of ground vibration amplification zones especially caused by simple frequency are studied in detail.(8) A new vibration prediction method that combined field tests and numerical simulation is proposed, which helps to predict the response in buildings quantitatively. From both theorical aspect and maneuverability aspect, in different analytical domain and with different statistical forms, transform method of physical quantities and their errors are discussed in detail.