Vibration isolation of over-track buildings in a metro depot by using trackside wave barriers

Abstract

More and more cities consider to build superstructures over metro depots to comprehensively exploit the air space. However, metro train operations into and out of depots can generate excessive vibration and noise within the over-track buildings, which hampers the performance of vibration sensitive equipment and adversely affects the living quality of building occupants. This paper explores a systematic numerical investigation on the use of trackside wave barriers to isolate vibration transmission from the track into over-track buildings. A numerical model composed of a train-track dynamics sub-model and a track-soil-building finite element sub-model was developed to study the vibration isolation efficiency of various wave barriers including trenches and concrete walls. Utilizing this model, which was validated by previous field measurement results, parametric studies were further conducted to investigate the vibration isolation sensitivities of geometrical (depth, width and distance) and infilling material properties of trenches. Results showed that the open trenches performed best in building vibration isolation, and its isolation efficiency depended on the normalized depth. Geofoam trenches, i.e. soft material infilled trenches, were proved to be more effective than lightweight aggregate concrete trenches, i.e. hard material infilled trenches, in the dominant frequency range of 16–40 Hz. Concrete walls offered even worse vibration isolation performance than the hard material infilled trenches. These results can be used as a guideline in designing the geometry of wave barriers or the infilling materials of trenches in metro depots with over-track buildings.