Vibration Mitigation Recommendations for Richmond Airport-Vancouver Rapid Transit Project
Vancouver TransLink / SNC-Lavalin
The Canada Line, Sky Train’s newest line, opened in August 2009. ATS was responsible for evaluating potential impacts from groundborne vibration and recommending mitigation measures. The approximately 10 km section from the Frazier River to the Waterfront Station passes by or under a number of multi-family and single-family residences. The entire section is either cut-and-cover or bored tunnel subway. ATS performed borehole propagation tests at 10 locations along the alignment that were selected to be representative of specific geologic conditions. A number of the tests included measurements inside residences to reduce the uncertainty that results when outdoor-to-indoor vibration attenuation and floor amplification must be estimated.
The testing showed potential for vibration impact at a number of locations along the alignment. However, because of the detailed testing, the uncertainty in the predictions could be minimized, which allowed using “safety factors” that were lower than are often used in similar situations. The conclusion of the ATS analysis was that all vibration impacts could be eliminated through the use of high-resilience direct fixation fasteners. Following the ATS recommendations, SNC-Lavalin installed “egg” resilient fasteners on approximately 6.5km of track that is as close as 15m to residences. No problems with ground-borne vibration were reported in the first year of revenue service suggesting that more expensive mitigation measures such as floating slabs would not have provided any benefits.