Considerations for the Implementation of a Train Vibration Monitoring System in Subway Tunnels

The Northgate Link extension of the Sound Transit Link Light Rail system starts at the southern end of the University of Washington (UW) Seattle campus and extends northward beneath the campus in twin-bore tunnels. To address UW concerns that train-generated ground vibration may negatively affect sensitive research, Sound Transit agreed to install a vibration monitoring system in the tunnels and use the measured tunnel vibration to identify any trains that generate vibration that might exceed negotiated limits. Prior to train operations, the relationships between the third octave vibration measured by the monitors within the tunnel and in the sensitive facilities were estimated using a shaker as a vibration source. This paper describes the verification phase of the project, where vibration from test-train operations was used to refine the estimates based on the shaker data.