Abstract

The dynamic characteristics of a tailings dam embankment, such as the predominant vibration period of the embankment and its shear wave velocity, are relevant for estimating the dynamic performance of the tailings deposit during large earthquakes. This paper reports the deployment of a dense seismological array installed over the 80m height cycloned-sand embankment dam of a tailings deposit located in Central Chile. The network consisted of 28 short-period seismic stations with triaxial 4.5Hz geophones that continuously recorded ambient seismic noise and earthquakes during three weeks. The seismic stations were deployed along the embankment crest, the downstream slope, and the foundation soil. Single-station records were processed using the H/V spectral ratio method to estimate the embankment dam predominant vibration period. In addition, the vertical components of the records from different station pairs were cross-correlated to determine Rayleigh wave dispersion curves, which were inverted with surface wave methods to obtain representative shear wave velocity profiles with depth. The results from the H/V spectral ratios show that the foundation soil is stiffer than the embankment dam, the predominant vibration period of the embankment is about 1sec, and there are slight differences in the vibration period along the crest near the abutments and over the downstream slope. Moreover, results from the cross-correlation of ambient seismic noise shows that the shear wave velocity increases with depth from values near 200 m/s at the surface to values of 400 m/s. In the future, the results from this passive experiment can be combined using ambient seismic noise tomography tools to obtain a 3D shear wave velocity map of the embankment dam, which can me contrasted and complemented with traditional geotechnical data, such as pore water pressure and deformation measurements, to improve the understanding of the dynamic physical stability of tailings deposits.