Toronto Transit Commission
Since 1994, the Toronto Transit Commission (TTC) has contracted Aercoustics’ as their main sound and vibration consultant. Aercoustics has been retained to perform studies throughout the entire TTC transit system, including subway, streetcar, and bus operations. One of the major types of studies conducted since this time and still on-going are the vibration studies carried out throughout the subway corridor, to evaluate subway vibrations travelling through the soil.
Subway vibrations in the ground are affected by three factors: soil conditions, local track conditions, and train wheel conditions. The measurement system and analysis procedure is required to investigate these factors. Studies have included evaluating the effectiveness of: rail grinding, switching fasteners and fastener isolation pads to determine how the vibration levels were affected.
Part of the solution was to develop a multi-channel vibration measurement system. Over the years, our instrumentation and analysis techniques have evolved from using a basic 2 channel system on the surface up to a 16 channel system allowing us to better quantify the vibration levels on the surface and underground simultaneously. Futhermore, custom in-house software has been developed to perform the analysis to evaluate the impacting factors. Also in order to determine how poor wheel conditions affected the measured levels, a wheel flat detection system was developed. This wheel flat detection system allows us to identify trains with poor wheel conditions so that the measured data can be filtered to remove or include the effect of these wheels. Currently, this system is only being used as an analysis technique, but long term plans are to develop a prototype which can assist the TTC in proactive maintenance of the wheels.
The study shows how local track and wheel conditions affect soil vibrations based on site specific captured data. The effect of rail grinding to reduce track corrugation is also presented.