doi:10.3850/978-981-08-7619-7_P055

ABSTRACT

Elastic wave-based nondestructive exploration methods have been widely used to characterize subsurface ground that is inherently heterogeneous because the dynamic properties can be correlated with various geotechnical properties. Although the inherent spatial variability of the geotechnical properties affects the stress wave propagation characteristics (e.g. travel-time, amplitude), ground heterogeneity in a range from small to large spatial scales has not been considered a significant factor. Thus, the main goal of this study is to explore the multi-scale effect of heterogeneous particulate/discrete media on the travel-time and wavefront characteristics of elastic waves through stochastic numerical analyses. The effects of the relative correlation lengths and relative propagation distances on the travel-time shift of elastic waves considering various intensities of ground heterogeneity were investigated. Heterogeneous ground fields of stiffness (e.g. the coefficient of variation = 10 ~ 40%) were repeatedly realized in numerical finite difference grids using the turning band method. Monte Carlo simulations were undertaken to simulate wave propagation in heterogeneous particulate media using a FDM numerical approach. The numerical results show that the disturbance of the wavefront becomes more significant with stronger heterogeneity and induces travel-time delays. The relative correlation lengths and propagation distances are systematically related to the travel-time shift.

Keywords: Soil heterogeneity, Elastic wave, Travel-time shift, Wavefront, Finite difference modeling, Monte-Carlo simulation.

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