Arno Crous obtained his BEng Civil Engineering degree (cum laude) in 2019 at the University of Pretoria (UP). His undergraduate research involved monitoring in situ pore pressures on an active gold tailings dam using tensiometers, designed at the University of Pretoria, that he constructed. This allowed him to monitor the pore pressure response during construction and operation of the tailings dam, as well as due to environmental effects, such as temperature and weather. He also measured in situ shear strength on the active tailings dam to find a correlation between suction and in situ shear strength.

Arno went on to complete his MPhil Civil Engineering degree in 2022 at the Hong Kong University of Science and Technology under the supervision of Professor Charles W.W. Ng. For his MPhil research he identified potential triggers and the associated failure mechanisms of tailings dams. He constructed model gold tailings dams and accelerated the models using the geotechnical centrifuge at UP. Once at the design acceleration, he wetted the slopes using a viscous fluid until failure occurred. He then conducted numerical back-analyses of the centrifuge tests using the Finite Element Method. He identified two potential failure mechanisms. Firstly, a retrogressive flowslide failure was triggered by raising the fluid level with the slope. Owing to the loose state of the soil and large seepage forces, severe sloughing occurred at the toe of the slope. The sloughing soil eventually broke away from the slope, which resulted in localized liquefaction at the toe of the slope. Subsequently a retrogressive failure of the slope was triggered. In his second test, a slide-to-flow failure was also triggered by raising the fluid level. In this test, a conventional drained slip failure was triggered by large seepage forces. This failure transitioned into a flow failure due to the undrained shearing of the soil within the slope. His research on centrifuge and numerical modelling of tailings dam failures is currently in the process of being published.

Arno has a paper published in Computers and Geotechnics with Professor C.W.W. Ng where they studied the static liquefaction mechanisms of loose sand fill slopes. Centrifuge modelling identified that large seepage forces triggered a localized failure near the crest of the slope, which subsequently resulted in the liquefaction failure of the slope. Numerical back-analyses confirmed the trigger and the failure mechanism. In addition, numerical simulations indicated that soil nailing can prevent the static liquefaction of loose fill slopes by preventing the peak shear strength of the slope from being mobilized.

During his MPhil Arno found that modelling tailings dam failures using a geotechnical centrifuge to be challenging. As a result, he will present a conference paper as the lead author at the 10^th International Conference on Physical Modelling in Geotechnics 2022 discussing the lessons learnt modelling tailings dam flow-type failures using a geotechnical centrifuge. This is to aid other researchers working in the same field to prevent them from encountering the same issues.

Arno returned to South Africa in early 2022 after finishing his MPhil degree to complete his PhD Civil Engineering degree at UP. He intends to expand the research he conducted for his MPhil, where he aims  to identify further triggers and failure mechanisms of tailings dams. He is also part of the Anglo American Brittleness Study, where total stress cells, moisture probes and tensiometers are installed in active tailings dams, which aims to monitor the in situ stress state within a tailings dam as it is constructed.

Current Duties

• PhD student
• Research assistant for the Anglo American Brittleness Study
• Tutor and lecture assistant for undergraduate modules (SGM311 and SGM323)

Field of Interest

• Tailings
• Unsaturated soil mechanics
• Physical modelling
• Numerical modelling
• Field monitoring
• Element testing

Research

Ng, C.W.W., Crous, P.A., Zhang, M., & Shakeel, M. (2022). Static liquefaction mechanisms in loose sand fill slopes. Computers and Geotechnics, 141. Paper No. 104525.

Crous, P.A., Ng, C.W.W., & Jacobsz, S.W. (2022). Lessons learnt modelling tailings dam flow-type failure in the centrifuge. Proceedings of the 10^th International Conference on Physical Modelling in Geotechnics 2022, Daejeon, South Korea.

Contact

Email               [email protected]

LinkedIn          Arno Crous