The Deep Foundations Institute (DFI) promotes a webinar series, ‘IT$ Money’, which stands for Increased Testing Saves Money. In this series, DFI highlights, every other month, 3 case studies during a 30-minute presentation each, followed by another 30 minutes of Q&A. The whole concept is that additional testing (whether foundation testing, soil investigations, or concept testing) can develop a cheaper execution plan, has a shorter execution schedule and reduces risk.
Dr Mothersille was invited to speak at this webinar and used the rock anchor investigation tests carried out during the construction of post-tensioned anchors at Hazelmere dam as the case study. Dr Mothersille explained that in his 30 plus years’ experience, Hazelmere dam stands out as one of the best examples showing how an asset owner’s commitment to a substantial anchor test programme resulted in significant benefits for the project in terms of reduction in anchor execution costs and geotechnical risk mitigation.
The test programme involved installing and testing four sacrificial trial anchors comprising 61No., 15.7mm diameter prestressing stands with an overall length of approximately 40m. These trial anchors were installed in the stilling basin, and the fixed anchors targeted the founding stratum layers of the proposed production anchors. In addition, the specialist anchor contractor was required to fabricate and install a full-scale anchor through the non-overspill crest of the dam. This 80m long trial anchor was called the dress rehearsal anchor, and provided an opportunity for the specialist anchor contractor could demonstrate the execution of a complete corrosion protected anchor system. Provision was made that in the event of poor performance of the dress rehearsal anchor, a replacement anchor could be installed adjacent to it. Fortunately, this was not required, and the dress rehearsal anchor satisfied the acceptance criteria stipulated in the specification. The data produced from the test programme was digitised, managed and analysed in real-time using the cloud-based software AnchorTestTM. This innovative tool proved invaluable by providing authorised parties access to the digitised performance data and convenient storage of records in the Cloud. Dr Mothersille was joined by fellow speakers Patrick Ijnsen (Netherlands) and Dustin Walkenhorst (Canada). Notable mentions are due to Gerald Verbeek (Host for the event) and Carol Planitzer (Administrative Assistant, DFI).
IT$ Money Webinar Speakers (left to right) Dustin Walkenhorst, Patrick Ijnsen and Devon Mothersille
Screenshot taken during the online Q&A session
61No. strand sacrificial trial anchor installed at Hazelmere dam, South Africa