In comparison, there are cases where railway vibration is an increasing concern: (1) underground high speed lines, (2) urban tramways, (3) freight traffic. In these cases it Sildenafil is more common that vibrations will arrive at nearby structures with the amplitude and frequency characteristics to cause negative structural effects. Therefore, vibration propagation/prediction for underground high speed lines, urban tramways and freight trains is the focus of this section.
Underground high speed lines are problematic because noise is confined within the tunnel, however vibration propagates to the surrounding soil and interacts with structures located above the tunnel. Although many railway tunnels are located deep below the earth’s surface, buildings with deep foundations may experience elevated vibration levels. For these cases, S-waves dominate the response at distances close to the tunnel, however as distance increases, P-wave can become destructive. In comparison, for at-grade tracks, Rayleigh surface waves carry the majority of vibration energy.