In urban areas characterized by a dense accumulation of buildings, railways are often constructed close to buildings and vice versa. This poses the problem of ground vibration from running trains propagating into buildings, causing their members to vibrate and emit noise (solid-borne sound). To accurately estimate vibration in buildings, it is especially important to quantitatively evaluate the damping effect of vibration propagating from the ground to building foundations. To achieve this, it is necessary to analyze the complicated dynamic interaction between the ground and buildings. Even using super-computers, the time-consuming nature of such calculation has so far made it difficult to estimate the phenomenon of vibration between the ground and buildings.
The RTRI implemented vibration tests on a pile foundation model and a silicon-simulated ground model of pile foundation buildings existing in quantity in urban areas. The tests enabled quantitative clarification of the input loss phenomenon in which piles restrict ground movement, thus leveling the displacement of the surrounding ground. They also clarified the radiation damping phenomenon in which vibration that enters buildings from the ground returns to the ground through piles. As a result, the RTRI clarified the mechanism of vibration propagation from the ground to buildings.
These findings clarified the feasibility of analyzing the above dynamic interaction using a simplified model to separate the ground from the building superstructure and piles. The RTRI subsequently proposed a simple technique to estimate vibration using a computer (Fig. 1). Comparison was also made between the measured and estimated values of vibration in buildings close to tunnels, viaducts or the like, and it was confirmed that the proposed technique has a sufficient level of precision for practical purposes (Fig. 2).
This method can be used for environmental impact assessment in constructing railways or implementing large-scale remodeling work and to estimate the vibration in buildings to be constructed close to railway tracks.