Experimental and numerical investigations on the seismic behaviour of a tailings storage facility in Italy

Abstract

In this study, a methodology is proposed to experimentally and numerically examine the seismic behaviour of a tailings dam located in Central Italy, with a special focus on liquefaction hazard. The mechanical behaviour of the materials was thoroughly investigated with advanced laboratory tests. To obtain high-quality undisturbed samples, an innovative and economical methodology using liquid hydrogen was introduced. Based on the results from laboratory tests, advanced constitutive models were calibrated to perform numerical simulations through Finite Element Modelling (FEM). Seven seismic signals were used as input motions. To evaluate the influence of the constitutive soil models on the results, the analyses were repeated by using two different models for the basin material. One model is framed in critical state theory, and the other in multi-yield plasticity. Acceleration time histories, displacements, and decrease in effective stresses were calculated and compared at several selected representative control nodes.

Acceleration time histories revealed a strong interaction between the behaviour of the basin and the embankment. Significant amplification of motion was observed at the surface of the basin and the embankment compared to locations at the basin bottom or near the embankment toe, because of topographical and stratigraphic effects. For all seismic signals and both constitutive models, the horizontal displacements reached maximum values of a few centimetres, whereas the vertical displacements were approximately one order of magnitude greater. The complete loss of effective stress was obtained with all signals and for both constitutive models, although the extent and location of this phenomenon varied. For both models, the loss of effective stress occurred predominantly near the surface of the settling basin. Considering the magnitude of both displacements and effective stress reductions, the results of this study, though preliminary, reveal critical stability conditions for the structure under seismic loading, highlighting a substantial risk of seismic liquefaction. These findings emphasize the importance of comprehensive hazard assessment to reduce the potential for tailings dam failures and their associated consequences.