Page 51 - University of Pretoria RESEARCH REVIEW 2018

Geotechnical
centrifuge
engineering SW Jacobsz, Department of
Civil Engineering
Everything that civil engineers build ultimately stands
on soil or rock. While rock normally provides excellent foundations, many types of problem soils occur posing challenges to engineers.
The research interests of Professor SW Jacobsz and his laboratory cover a range of projects in the field of geotechnical engineering, focusing on unsaturated soil mechanics. The research facility at their disposal is the University’s 150 g-ton geotechnical centrifuge which enables physical models of geotechnical problems to be studied at full-scale stresses. The centrifuge can accelerate models weighing as much as 1 ton to 150 times the Earth’s gravity.
The modelling capabilities offered by the centrifuge has attracted international collaboration with the Universities of Durham, Cambridge, Khartoum and Dar es Salaam to develop guidelines for the design of wind turbine foundations on expansive soils.
The WindAfrica project is funded by the Engineering and Physical Sciences Research Council of the United Kingdom Global Challenges Fund. Due to high average wind-speeds large
parts of Africa are suitable for wind energy generation, but many such areas (e.g. in Sudan and Tanzania) are underlain by deep expansive soils. The large ground movements associated with seasonal moisture fluctuations in such soils pose particular challenges for the construction of sturdy wind- turbine foundations with very strict permissible movement tolerances. The collaboration includes the construction of a series of heavily instrumented large-scale prototype foundations, which will be load-tested in an expansive clay profile near Steelpoort, Limpopo Province.
The behaviour of these foundations under various loading and wetting scenarios are currently being modelled using small-scale physical models in the geotechnical centrifuge at UP to determine critical load
cases to be simulated on the large- scale foundations in the field. This work is complemented by numerical modelling at Durham University, supported by soil testing at the University of Cambridge to quantify the input parameters required by the numerical models.
Another major research interest of Professor Jacobsz and his laboratory involves subsoil cavity propagation leading to sinkhole formation.
This is of particular significance
in the Gauteng province where approximately 25% of its area is underlain by sinkhole-prone dolomite bedrock. Related to the sinkhole studies is a project to model cave mining in collaboration with the University of Western Australia.
In 2018, co-authored publications that addressed some of the findings of the research group were published in Geotextiles and Geomembranes, Granular Matter and in Computers and Geotechnics.
A recent spin-off from the work on unsaturated soil mechanics was
the development of low-cost, high- capacity tensiometers capable of measuring pore water suctions exceeding a Mega-Pascal. One of the highlights in 2018 was the filing of a provisional patent on work related to pipeline leak detection using fibre optic ground strain measurement.
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