Centrifuges spin reduced-scale geotechnical models to high acceleration levels to replicate the same profile of stress with depth in the spinning soil sample as in the field, hence achieving similitude between model and field conditions.
As geotechnical behaviour is strongly stress dependent, this is an important condition to get correct, so 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, so 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 and software, electronic and mechanic engineers, with each centrifuge spinning 24/7 on average 270 days a year.
The PACS was developed at the NGCF specifically to meet the complex demands of motion control during centrifuge model testing. It provides the user with the flexibility of connecting most industry standard actuators, servo controlled devices and analogue feedback devices.
runs on a National Instruments 9030 CompactRIO controller
provides the user with four PID Controller channels that can be configured individually in either displacement or force control, and synchronised using a built in waveform and sequence generator
channels can be linked using event limits providing a powerful tool for automating and customising tests
The NGCF-developed DigiDAQ is a complete compact data acquisition system designed to meet the needs of today’s centrifuge testing. It is versatile and robust, making it suitable for use on centrifuges, in the laboratory or in the field.
real-time data acquisition on up to 64 channels
available in either a rack-mounted or miniaturised configuration
performs the full sequence of amplification, conditioning, digitisation and storage on a single circuit board via an independent micro-controller allocated toeach pair of instrumented channels
high-speed simultaneous capture at up to 1 million samples per secon
a Graphical User Interface which provides data logging from sensors connected to the DigiDAQ unit as well as PACS and the Centrifuge Control System
The NGCF designs and manufactures its own soil characterisation tools, including T-bar, cone, ball, piezocone and piezoball penetrometers. This provides researchers with greater flexibility when designing specific centrifuge model tests and better control of the parameters being measured. Over the last few years, the NGCF has developed variations on these penetrometers and additional soil characterisation tools such as hemiball and torroid penetrometers, piezofootings and miniature ball penetrometers to answer specific modelling challenges and to provide additional engineering properties.