Study Of Isolation Measurements For Environmental Vibration Induced By Elevated High-speed Railway

The cause and characteristics and harm of environmental vibration, which is induced by elevated high-speed railway, are briefly introduced in this paper, and the environmental vibration control research methods and research contents are briefly introduced. Based on the former research work, the developing status in China and abroad for the measures for vibration reduction are summarized.The environmental vibration induced by high-speed trains running on the elevated bridges is analyzed by numerical simulation method. The system is divided into two sub system models:train-bridge-pier upper model and foundation-soil sub model, the two sub model are connected by the reactions of piers at bottom. The reactions can be acquired by the upper model. Then they are applied on the foundation-soil model as external forces. The characteristics of surrounding soil can be calculated by the software of FEM.In the upper model, the train is simulated as moving load series; In the software, the girder and pier are simulated by the Beam188elements, in which the section shape can be defined by the users. In order to simulate the plane model of the four-span beam, the pier is split into two parts, the size and stiffness of each part is half of the original pier. Using this model, the reaction curves of piers at bottom are obtained.In the lower model, the piles and the surrounding soil are simulated by the Solid45elements. All degrees-of-freedoms of coincide nodes on the piles and soil are coupled. Fixed boundary is adopted at the bottom of soil, and three-dimensional viscoelastic artificial boundaries are employed for the rest of soil profile. The reactions on the bottom of piers are applied to the lower model as external forces. When the solution is done, the responses of nodes on ground can be acquired. Afterwards, various barriers are added in the soil model, including empty ditch, single row piles, EWIB and HWIB, then the vibration isolation effect of these barriers can be known.The no isolation measures analysis results show that the basic frequencies of nodes on ground are mainly in the low frequency region. The ground responses decrease with the distance to piers. The analysis results of isolation measures show that all of them have certain effect of vibration isolation, the responses on the ground is reduced obviously, among which the empty ditch is relatively the best. The application of empty ditch to practical project shows that it can effectively reduce the vibration response.