Design and Performance of a Comprehensive Vibration Monitoring System for Trains Under University of Washington Campus

Seattle Sound Transit’s Link Light Rail extension to Northgate runs under the University of Washington (UW) campus in a twin bore tunnel system. The ground vibration produced by the trains is required to meet stringent vibration limits for 24 buildings. Vibration from each train passby is recorded by 40 vibration monitoring units installed in the tunnels. The monitoring units are designed to trigger warning alarms in case the train vibration levels approach the vibration limits and exceedance alarms if the limits are exceeded. These limits are based on building vibration limits with vibration adjustments based on field testing. Based on the frequency and location of the monitors, the warning alarm settings needed to be adjusted to minimize false alarms from background vibration. This paper presents the design of the monitoring system, the progression of the warning alarm setting adjustments, and the preliminary vibration trends from representative monitors.