Volume 35, Issue 2 (March 2012)
Time-Lapse Monitoring of Fabric Changes in Granular Materials by Coda Wave Interferometry
The determination of wave velocities in soils captures an important role for small-strain parameter in constitutive modeling as well as in monitoring processes of the state. The wave velocity differs substantially with the porosity, surrounding pressure, degree of saturation and other parameters in soils. In particular when the environmental conditions are non-stationary. For studying the change of state parameters in granular materials, the identification of the velocity evolution can be a challenge in particular if the perturbations are small. We discuss the application of a new seismic method for geotechnical experiments—the Coda wave interferometry. The method is used to detect the wave velocities change related to small soil perturbations. Whereas the perturbations are caused by small changes in stress and void ratio. Different material, well-known sands and artificial glass beads are analysed in this experimental study by conventional volume measurements and seismic methods to detect the stress and porosity changes. The wave excitation and recording was done by piezoceramic bender elements. In result of the tests, the coda wave interferometry emphasized its large potential for the time-lapse monitoring of soils.