Soil liquefaction tests in the ismgeo geotechnical centrifuge

Operational since 1988, the ISMGEO geotechnical centrifuge is a 240 g-ton centrifuge with a nominal radius of 2.2 m. The centrifuge can spin up a model of 400 kg up to 600 g. Since 2010 the centrifuge is equipped with a 1D shaking table able to reproduce real earthquake signals under an acceleration field up to 100 g. The special design of this centrifuge allows keeping the shaking table permanently installed on the rotating arm, while the model is driven on the shaking table during the spin-up phase. Physical models are submitted to 1D seismic shear waves, the typical free-field boundary conditions are reproduced by an equivalent shear beam box recently manufactured for dynamic applications. This paper describes firstly the main features of the facility and of the equivalent shear beam box. Secondly an application example of dynamic tests to simulate soil liquefaction is reported: the model tested reproduced a homogeneous sand column subjected to a real earthquake, properly scaled; specific sensors monitored the seismic excitation within the model, the excess pore pressure development and the soil surface settlements. The results of test presented here show the capability of the centrifuge to reproduce extreme loading conditions such as liquefaction during an earthquake. Many kinds of soil profiles can be tested, combination of ground motions can be applied to the models, the effectiveness of liquefaction mitigation techniques can also be studied.