Inland Branch - Technical Site visit: University of Pretoria Centrifuge Laboratory
More than 20 Inland Branch members attended a special technical site visit recently at the University of Pretoria’s Centrifuge Laboratory, located at its Hatfield campus.
Professor Elsabé Kearsley (Head of Civil Engineering) and Professor SW Jacobsz were both on hand to welcome the visitors, after which Prof Jacobsz proceeded to describe to the audience the background to the introduction of a Geotechnical Centrifuge Laboratory at the University and the current research work that is being carried out using this unique facility.
The centrifuge is used to subject small scale models to high accelerations, thereby creating the correct stress distribution in the model. This is necessary to ensure realistic behaviour. The centrifuge enables geotechnical and concrete problems to be studied by means of physical modelling.
The 150 G-ton Actidyn C67-4 centrifuge is capable of accelerating payload of up to 1 ton to 150G. The effective centrifuge radius is 3 metres, and an automatic balancing system keeps the machine in perfect balance during tests.
The centrifuge is fitted with a Digidaq system for data acquisition and complemented by an HBM Quantum systems (24 channels). This sufficient for all data acquisitioning, including several cameras on the centrifuge.
The centrifuge control system is entirely computer-based and the control room is located adjacent to the centrifuge enclosure. This houses the control computer, two high-end personal computers used for data acquisitioning and processing, a large monitor and a small discussion area.
From a safety point of view, extensive measures have been taken. The machine is housed in a heavily reinforced concrete chamber. The walls have been designed to absorb an impact resulting from the release of a model package of 1 ton at 150G. The chamber is fitted with a light stainless steel door which is shielded from the Centrifuge Laboratory and adjacent laboratories with another reinforced safety wall, padded with impact absorbing foam concrete.
|Members making a thorough inspection of the Centrifuge|
Professor Jacobsz then moved on to describe some of the research work, much of it concrete-based, that is currently being carried out using the facilities of the centrifuge. This included:
- Dolomitic sink holes
- Ultra-thin continuously reinforced concrete pavements (UTCRCP)
- Settlement of opencast mining backfill
- Segmental concrete block retaining walls
- Modelling of cave mining
- Soil structure interaction of strip footings
- Soil Culvert Interaction.
The Department of Civil Engineering at the University is fortunate to employ a team of highly skilled technicians to provide the necessary technical support with the development, construction and testing of centrifuge models.
In conclusion, Professor Jacobsz indicated that there were numerous research possibilities with physical modelling and the University would welcome any industry collaboration in reaping the benefits of this technology.
Members inspected the centrifuge and were then treated to a practical demonstration with the testing of a scaled model of a culvert profile.
Inland Branch Chairman, Roelof Jacobs, thanked the University for allowing Concrete Society members to visit the Centrifuge Laboratory and for the very informative and interesting presentation and demonstration.
He also thanked Lafarge South Africa for their sponsorship of the whole event.