Study On The Vibration Characteristics Of Rock Metro And Its Applications

In recent years, with China's sustained economic development and living standards rising, how to ease the traffic pressure and imply energy saving has become an important part of urban development planning.Considering rail transportation is convenient, rapid and environmental friendly, which has been rapid development in many large cities in China, but the resulting vibration along the railway has become increasingly prominent, and has attracted people's attention.The vast majority of metro are constructed in the soil conditions, but the metro constructed in Chongqing and Qingdao are in a large area of rock conditions, which are embedded in a larger stiffness rock with the slow vibration attenuation and further impact, so it is vitally important to study the track vibration.Furthermore,it will bring about obvious economic and social benefits. According to the Qingdao subway situation, the main research work of this paper is as follows:First, for ease of discussing the vibration behavior of subway track structure and simulation for the vibration force between wheel and rail, based on previous studies, the current used train, tract and train - tract coupling vertical vibration model are analyzed, ans its differential equations are derived;Second, a track beam model is established through the finite element simulation software ANSYS12.0, as a result, the influent length of its static is obtained about 4.2m, and thus track structure stiffness formula is derived. Take a single freedom degree system for example, the dynamic tract stiffness equation is derived, and the formula shows that: dynamic track stiffness is a variable value, which is related to natural frequency, damping of the structure and frequency,action time of external load. The vibration isolation system is analyzed based on single freedom degree equation, and the system shows that vibration control should be done from three aspects,including the mass, stiffness and damping;Third, with weak, thin overlying and the lower weathered hard rock environment in Qingdao, a tunnel– ground finite element model is established by ANSYS12.0 to study the vibration propagation law in rock layers, and the results show that: vibration attenuation law generally associated with subway in earth layers underground, but the vibration strengthen areas is about 35m far from the tunnel center. This distance and the ground monitoring points'vibration are much larger. Moreover, three vibration strengthening band appears: 10~20Hz,35~45Hz and 70~80Hz; Finaly, the main damping track structure at home and abroad ( Cologne-egg fastener, Vanguard fastener, elastic short sleeper solid bed and floating slab four types etc.) are calculated by stiffness,and its real economic applicable indicators are compared, which provides a principle for Qingdao subway damping track structure selection and the programs comparison. The paper finaly proposes that an integrated approach should be done and the appropriate damping level should be made by damping section and categories of building.