Abstract
In near surface geophysics, a multi-channel analysis of surface wave (MASW) method has been increasingly applied for underground infrastructure assessments by measuring shear wave velocity profile. The conventional MASW mostly employs contact sensors like geophones and accelerometers to detect surface vibrations. In this study, noncontact sensors technology such as a laser Doppler vibrometer (LDV) and a microphone were used to measure Rayleigh wave and leaky Rayleigh waves respectively. These noncontact sensors were installed in a scanning platform that was driven by a stepper motor. The scanning MASW system consisted of two excitation sources: an electromechanical shaker and steel-balls to generate frequency sweeping (chirp) signals with frequency from 30 Hz to 500 Hz and high frequency (up to 40 kHz) impulsive signals respectively. The LDV-shaker-MASW was developed for near surface soil shear wave velocity profile exploration and the microphone-steel ball-MASW was built for pavement assessment to extract the dispersion curve. The details of the system and several case studies will be addressed.
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