Study On Vibration Reduction Of Rubber Pad Floating Slab Track Structure

With the rapid development of the construction of subway, the vibration problem caused by the subway, including impacts on the surrounding sensitive buildings and nearby residents has become the focus of researches.The paper, using the theoretical analysis and numerical simulation, studies the vibration caused by subway mainly by two aspects of research, including the generation of the vibration source, the spread impact of the vibration on the surrounding environment. The vibration loads and surface transient dynamic response caused by Qingdao Metro Line3rubber pad floating slab track bed structure are studied. The main achievements include:1) The theoretical model coupled with vehicle and track is established. There are10degrees of freedom in vehicle system model, including the ups and downs and nodding movement of the body and two bogies, the ups and downs of the four wheels. The vehicle, bogies and wheels are treated as rigid body; the rail and floating slab are simplified as finite-length Euler beams, which are supported by discrete continuous springs. The theory of wheel-rail contact is Hertz contact model.2) The differential equations of system motion are established. These equations are solved by Newmark step-by-step integration method. The effects of rubber pad stiffness and damping on the ground reaction force and the wheel-rail contact force under the United States five irregularity spectra excitation are studied. The effects of stiffness and damping on both the process and the amplitude frequency characteristics of the ground reaction force and the wheel-rail contact force are given. The results shows that the wheel-rail contact force increase and the ground reaction force decrease, the frequency range of the wheel-rail contact force have little change, the frequency range of the ground reaction force decrease with the stiffness increasing. The rubber pad damping have little effect on the ground reaction force and the wheel-rail contact force, while the damping is too small, the ground reaction force has a beating vibration.3) The finite model coupled with vehicle and track is established by ANSYS. The system natural frequency and natural mode shapes are studied by modal analysis in ANSYS, the results show that when the natural frequency is less than lOHz, the modal characteristics mainly reflect the rigid body vibration of the body system, when the natural frequency is more than10Hz, the modal characteristics mainly reflect the coupled vibration of the wheel and track. The effects of the rubber pad stiffness and damping to the vehicle ups-downs and ground reaction force are studied using harmonic response analysis in ANSYS, the results show that the ground reaction force decreases and the vehicle vibration increases with the rubber pad stiffness decreasing, the ground reaction force and vehicle vibration decrease with the rubber pad damping increasing, but when the damping is too large, as the damping increasing, the ground reaction force gradually increases. The studies show when the rubber pad surface stiffness is0.015-0.02N/mm3and surface damping is0.6-0.8MN·s/m3are appropriate.4) The2D finite model of tunnel structure and soil is established considering the some geological condition of Qingdao Metro Line3. The effects of the rubber pad’s stiffness and horizontal distance on vertical vibration and horizontal vibration are studied by transient analysis in ANSYS. The results show that the amplitude of vertical and horizontal vibrations decreases, the frequency range of vertical vibration decreases, the frequency range of horizontal vibration has little change, with the horizontal distance increases. The vertical and horizontal vibrations are both accord with the EIA (Environmental Influence Appraise). The horizontal vibration and vertical vibration acceleration decrease with the decreases of rubber pad’s stiffness.