An isolation case study of a vertical caisson wall directly adjacent to an underground rail vibration source

Abstract

A large concrete tower planned for construction was proposed at a site immediately adjacent to underground rail. The underground rail passenger trains pass frequently at a rate of once per 2-4 min 18–20 h per day. Excavation began and a caisson wall was constructed facing the underground vibration source. Preliminary measurements were made by placing an accelerometer on the East facing caisson wall. Attenuation was required in the 20-63 Hz frequency range. An isolation layer (GenieMat DM) was added to the caisson wall. The presentation will illustrate how this was done in combination with water proofing of the foundation and other onsite complexities. Large steel tie-backs are used to hold the caisson wall in place and these were treated to prevent any direct path for vibration. Upon completion of construction, measurements are taken and the level differences are presented. Attenuation exceeded the design and building code criteria at all one-third octave bands of concern.