Use of Numerical Models to Determine the Effectiveness of Anti-Vibration Systems for Railways.

Vibration from trains can cause annoyance and also concern about possible damage to property. It is a major issue in the environmental impact assessment of new railways and where new traffic is to be added on existing railways. Track designed to control vibration has been implemented on a number of railways. These designs are effective solutions for vibration at frequencies at the low end of the audible range. Such vibration causes re-radiated noise in buildings and is especially associated with trains in tunnels. However, at present there are no proven, effective solutions for vibration from heavy freight trains. This occurs at lower frequencies (down to about 4 Hz) and can be felt. In an attempt to deal with frequency vibration, experimental track has been built containing continuous slabs of concrete. This has shown encouraging results in tests but it is not clear how generally applicable these improvements would be, or even whether the test results were valid. To clarify these matters it is necessary to develop theoretical models. To date, a number of two- and three-dimensional models have been developed at British Rail Research. These are used to investigate the expected performance of different track constructions covering the cases of both re-radiated noise and low-frequency vibration. Experimental work is being carried out in parallel to validate the theoretical approach and to provide data on appropriate material parameters for the ground.