Abstract

The periodic analysis of the dynamic response of a tailings dam during it’s operation and growth it’s necessary to estimate the behavior of the structure (principally, the embankment wall) during the occurrence of a large earthquake. The seismic response of a tailings dam depends upon the geometry and the stiffness of the materials that compose the embankment wall, as well as the input ground motion, among other factors. Another dynamic parameter is the predominant vibration frequency that represents the natural vibration frequency of the earth structure (Verdugo et al., 2017). If an earthquake induces a ground motion with high energy content around the predominant vibration frequency, the embankment wall may resonate, increasing its dynamic displacements, and eventually produce damage, which may compromise the physical stability of the entire tailings deposit. In earthquake engineering, the most common method to determine the amplification function of a soil deposit is the standard spectral ratio (SSR) method, computed as the spectral ratio between the response at the site of interest with respect to the response of a reference point (Steidl et al., 1996). Another method to estimate the amplification function is the single station horizontal-to-vertical H/V spectral ratio (HVSR). It has been proved in soils deposits that the HVSR curves from ambient seismic noise and earthquake records yield similar results, hinting that the HVSR is a relatively constant site characteristic (Fernandez et al., 2019). Since tailings dams build with cycloned sand in Chile have embankment walls with very gentle downstream slopes (H:V varying from 3:1 to 4:1), the use of the HVSR method could be a simple method to estimate its dynamic properties. The use of the method has been tested and validated in natural sloped terrains (Diaz-Segura, 2016). This study is a first attempt to show the possibility to monitor the sub-surface condition of a tailings dam using relatively inexpensive microseismic monitoring stations.