To characterize the seismic wave field associated with hard rock tunneling and associated activities, 14 seismic stations were deployed in and near a tunnel being bored by a tunnel boring machine (TBM) for a water project near Boston. The 5.15 m tunnel is being bored through granitic and metamorphic rocks at a depth of about 125 m. Seismographs were deployed for about 1 week during August of 1999, and recorded about 40 hours of TBM activity. The deployment consisted of both short-period and broadband instruments, and an array of aperture 60 m was deployed at the second-closest broadband site. During one 8-hour work shift, a short-period and broadband sensor pair were deployed inside the tunnel, about 35 m behind the TBM.
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|Map & Cross-section of Tunnel
Courtesy of GeoEnvironmental, Inc. & Metrowest, 1995
|Tunnel Boring Machine||Map of Deployment|
Signal and Noise Spectra |
TBM Signal Attentuation
Frequency-Wavenumber Analysis of the Mini-Array | Acoustic Resonances | Conclusions