The NGCF currently operates the only geotechnical centrifuge facility in Australia and runs an impressive three geotechnical centrifuges: a 3.6 m diameter fixed beam centrifuge, a 1.2 m drum centrifuge and a new 10 m diameter centrifuge. This makes the NGCF the only geotechnical modelling facility in the world with three centrifuges operating on a daily basis.
Centrifuges spin reduced-scale geotechnical models to high acceleration levels to replicate the same stresses in soil samples as those found in the field, hence achieving similarity between model and field conditions. As geotechnical behaviour is strongly stress dependent, this is an important similarity to get correct such that meaningful observations and measurements can be made on the centrifuge model. Scaling laws are then used to interpret the centrifuge model results at field scale, such that the centrifuge results can be used as an input in geotechnical design, or to demonstrate geotechnical behaviour and mechanisms that can then be reflected in analytical or numerical approaches.
The centrifuge facility at the NGCF is supported by a team of operators, software, electronic and mechanic engineers and operates on average 275 days a year.
The 3.6m diameter beam centrifuge was manufactured by Actidyn in France and commissioned in 1989. It is a 40 g-tonne centrifuge, able to spin 200 kg at an acceleration of 200 g. The centrifuge can accommodate soil samples up to 1300 mm long and 390 mm wide, representing a soil surface that is up to 260 m by 78 m at 200 g. The beam centrifuge is equipped with state-of-the-art UWA developed data acquisition and motion control systems. Two-dimensional actuators can sit on the soil sample package, enabling a wide range of motion to be applied to the geotechnical model. This motion may be in both load and displacement control and can replicate complex and realistic environmental loading.
The Broadbent Drum Centrifuge was commissioned in 1997. It has a diameter of 1.2 m and a maximum acceleration level of 350 g. The soils sample is contained within a channel that is 300 mm high, 200 mm deep, giving an available testing length of 2.5 m. The centrifuge features an independent tool table allowing for 360 degree access to the sample, and on which sits a two-dimensional actuator, effectively providing motion along all three spatial axes. The data acquisition and motion control systems are identical to those on the beam centrifuge allowing models to be used indiscriminately between the two centrifuges.
C72 beam Centrifuge (Commissioned 2016)
The Actidyn C72 centrifuge is a large beam centrifuge with a platform radius of 5 m. It is a 240 g-tonne centrifuge, capable of spinning 2400 kg at 100 g. The soil sample is 1 m long, 1 m wide and up to 600 mm deep, which represents a volume nearly 10 times greater than the sample in the smaller beam centrifuge. The centrifuge also features in-flight automatic balancing, and state-of-the art optic fibre transmission for data and video. The facility will also feature new capabilities with an on-board four-dimensional robotic system enabling linear motion along the x, y, and z axis, and rotation about the z axis, in addition to an in-flight tool changing mechanism.