Potential low frequency ground vibration (<6.3 Hz) impacts from underground LRT operations

Vibration sensitive research activities at the laboratories of the University of Washington (UW) Physics and Astronomy Building (PAB) were a critical issue for the design of the Sound Transit Link Light Rail LRT system in Seattle, Washington. A study was conducted to measure and predict low frequency ground vibration generated by the LRT operations. The Universityʹs concern was an on-going research experiment in gravity, which had sensitivity to vibration below 6.3 Hz. The experiment was located on an independent concrete slab in an area cut-out from the building foundation with no connection to the building structure. Another concern was the planned future construction of a Life Sciences Center with vibration sensitive test equipment. This paper presents the results of a study to estimate the ground displacement at these buildings using empirical measured data of a similar deep tunnel transit system and finite difference modelling analysis.