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| EXPERIMENTAL STUDY OF VARIATION OF MEDIA PROPERTIES MONITORING USING MULTIPLE SCATTERING WAVES |
| SONG Lili，GE Hongkui，GUO Zhiwei，WANG Xiaoqiong |
| (Key Laboratory of Seismic Observation and Geophysical Imaging，Institute of Geophysics，China Earthquake Administration，Beijing 100081，China) |
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Abstract Comparing with directly arriving waves，multiple-scattering coda waves are highly sensitive to physical properties and stress variation of medium. In this paper，a test system is established and experimental studies of scattering waves on concrete and rock samples are carried out. The coda wave formation mechanism and influence factor are analyzed. The coda wave interferometry(CWI) by cross-correlation of coda waves and the data processing method are also discussed. The formations of scattering wave and coda wave are significantly influenced by the rock scatters concentration and size，ultrasonic polarization direction and frequency. The accuracy and sensitivity of velocity changes by CWI are an order of magnitude higher than P-wave and S-wave velocities. It is crucial to this high precision technology that the repeatability and stability of measurement system，high signal-to-noise ratios of coda waveforms and cross-correlation analysis time window selection. The stress dependence of wave velocities for the concrete samples is attained. The coda wave velocities of all the samples increase with the increasing stress，which is same to directly arriving waves. The sensitivity of coda wave velocity changes decreases with the increasing of Young?s modulus. In this experiment，CWI is also used for monitoring the building pillar?s velocity change with environment humidity and water saturation process in a concrete sample. It is shown that CWI is a high precision monitoring means to monitor the variation of media properties.
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Received: 18 July 2011
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2012, Vol. 31 
