Vibrations from Railway Traffic : Computational Modeling and Analysis

Sammanfattning: The population is growing, and an increasing proportion of the population lives in urban areas. As a consequence, human exposure to noise and vibrations is increasing; two major sources being railway and road traffic. Larger and denser cities lead to a higher amount of traffic close to where people work and live. Land close to railways and heavily trafficked roads, previously left unexploited, are now being used for dwellings and offices. Vibrations are often accompanied by noise, to which long-term exposure is known to have serious health effects. Furthermore, some buildings such as hospitals and research facilities contain instruments that are highly sensitive to vibrations, and require proper vibration isolation to ensure safe operation. To address the problems of noise and vibrations, their generation and propagation need to be understood. The vibrations next to a railway track are caused by the forces exerted on the track by the passing train. These forces are the sum of a quasi-static part due to the deadweight of the train, and a dynamic part. The dynamic part is caused by various phenomena resulting in time-dependent train–track interaction forces. The vibrations generated at the track propagate through the underlying and surrounding soil as elastic waves of various types. The mechanical properties of the soil strongly influence the wave propagation and the resulting vibrations registered by a receiver at some distance from the track. For a building structure next to the track, the vibrations inside the building furthermore depend on the mechanical and geometrical properties of the building’s structural elements.In the thesis, numerical models and modeling strategies for predicting ground-borne vibrations from railway tracks have been developed. Various techniques to calculate the wave propagation in the soil have been implemented and used for studying different phenomena, such as the vibrations at the soil surface and in a building next to the track, caused by a train running over an uneven rail. Furthermore, the mitigation of traininduced ground vibrations and so called “critical velocity” effects, i.e. highspeed trains moving faster than the wave speed in the underlying soil, were studied. In addition, models developed in the thesis were utilized to compare the dynamic responses of a heavyweight concrete building and a lightweight wooden building, when excited by ground vibrations induced by a train moving over an uneven rail.