David Reid, Andy Fourie, Riccardo Fanni, Cristina Vulpe, Alexandra Halliday
Recent failures of a number of tailings storage facilities (TSFs) has highlighted the need for better
governance and operational management of these structures. One means to improve their safety is clearly better and more focussed monitoring. Significant efforts are underway in this area, with a number of technologies being deployed. In particular, the monitoring of deformations through a variety of means (direct, satellite inferred) is increasingly being applied. While deformation monitoring to warn against failure has a long history in geotechnical engineering, some aspects of the rapid triggering and resulting flow of some TSFs may not be amenable to deformation monitoring, in the sense that actionable warning of an impending failure is not assured.
To examine this issue, a series of numerical models of an idealised TSF are carried out. This idealised TSF is brought to failure by means of a rising phreatic surface – often referred to as the constant shear drained (CSD) stress path. Deformations of the outer slope and crest of the numerical model – i.e. those that could be monitored for a real TSF – are tracked and analyses for the models carried out. It is seen that under CSD loading distinct deformation patterns indicative of impending failure are not always clear. Rather, minimal deformations and indeed swelling of the crest is seen leading to failure. The importance of recognising the minimal pre-failure deformation patterns that may manifest with a rising phreatic surface is noted.
— OR —
Now showing 1-12 of 37 3483:
Thomas Ridgway, Nic Polmear, Hugh Tassell
All industries, inclusive of the dams and tailings industry use some form of monitoring and reporting to confirm items or services are functioning properly or correct. In engineering, we seek to use both manual and automated systems to both qualifiably and quantifiably define the suitability of a process or structure/item. As the dams industry continues to evolve with technology and with ongoing developments in stewardship expectations for both water dams and tailings dams the industry is beginning to move into automation of their instrumentation systems. This process has recently been undertaken at a mine in NSW with the development of both a near real-time survey monitoring and visualisation system as well as a monthly photographic assessment system. This paper will set out the process undertaken to assess the surveillance monitoring requirements for the mine, details of the design, implementation of a near real-time monitoring system and the difficulties associated with the work.
Meizhiwen Zheng, Nimal Gamage
This study used MIKE 21 to replicate the Cooma tank failure by varying modelling input parameters. This study explores the mechanism by which flood water can damage buildings and investigated different damage category assessment method to predict building damages.
Richard M Robinson, Siraj Perera, Gaye Francis
SFAIRP (so far as is reasonably practicable) is the ‘modern’ definition of ‘safe’. Shrouded in the legal
concept of the ‘safety case’, it is actually the judicial form of the principle of reciprocity – the golden rule – do unto others, incorporated into the common law by the Brisbane born English law lord, Lord Atkin in 1932.
In dam safety terms, it asks the question; “If you lived downstream of a dam, how would you expect the dam to be designed, operated and maintained in order for it to be considered safe?”
The answer is that it now requires a public demonstration that all reasonably practicable precautions are in place in a way that satisfies the will of our parliaments and our sovereign’s courts, otherwise known as a SFAIRP safety case.
Christopher Dann, Chad Martin, Garry Fyfe, Nigel Rutherford
This paper presents a case study on remedial works that were undertaken at Lock and Weir One
along the River Murray, that to our knowledge are the first of their kind in Australia.
The weir structure’s left abutment is comprised of a stepped concrete structure founded on timber
piles, with timber sheet piles extending beneath the structure to cut off seepage through underlying
alluvium. A piping incident occurred at the left abutment in late 2014 and a filter blanket was
installed as an emergency response measure. A detailed review of historic construction documents
showed that there was a “missing” timber sheet pile upstream of the piping boil. Geotechnical
investigations, including piezometer installation confirmed the missing timber sheet pile was the
likely cause of the piping incident. A piping risk assessment showed the residual risk of further piping
was reasonably high.
A range of remedial works was considered as permanent risk reduction works. However, these
solutions required extensive temporary works to expose the missing timber sheet pile including a
cofferdam to access the defect and partial demolition of a recently constructed fishway structure.
An alternate Secant ‘Grout Column’ solution was developed that comprised targeted drilling and
backfill grouting to close the gap where the sheet pile was not installed and to grout an inferred void
under the abutment structure. This solution was successful at reducing seepage through the
abutment structure, as indicated by monitoring piezometers.
Rachel Jensen, Adam Broit, Chriselyn Kavanagh
Downstream emergency response is a critical driver in the consequences and potential life loss associated with dam flooding and failure. This response is highly varied between stakeholders, communities and the nature of the flooding or dam threat. As assessments on dam failure consequence and potential loss of life become increasingly important in understanding holistic dam risk, they are also becoming increasingly complex.
As part of a portfolio wide Comprehensive Risk Assessments, Sunwater have undertaken workshops with a wide range of stakeholders to better understand downstream emergency response and the warning timeline. The workshops have been aimed at facilitating better downstream stakeholder engagement, obtaining key data for consequence assessments and developing consistency in assumptions for potential life loss.
This paper presents the standardised methodology undertaken for warning time workshops, the outcomes for a range of downstream stakeholders and correlations between stakeholder groups which influence warning time response. These outcomes may be used by practitioners in the absence of catchment specific warning time data and provide a counterpoint to international standard warning time assumptions.