Geotechnical engineering input is typically concentrated on the development and operational phases of large-scale mining operations. The primary goal of geotechnical assessments is to optimize mine productivity while ensuring a safe work environment. However, these design decisions can have significant implications for future productivity, mine closure options, and associated costs. This paper will present examples of how geotechnical decisions impact closure planning and propose an approach to incorporate the uncertainty of future closure expectations into the operations design process

Biography

Kim is the Manager of Geotechnical Engineering at Rio Tinto Iron Ore. With nearly 30 years of international experience, Kim has worked in various geotechnical areas, including open pit and underground geomechanics, mine backfill, heavy civil projects such as road, rail, and port investigations, as well as water retention and tailings dams. Kim holds a PhD in Civil Engineering from the University of Toronto.

Every project needs to balance competing interests such as cost, time, performance, community, environment and uncertainty (risk).  Ideally, an optimal balance can be found to suit the project.  Balanced decision making means that there is a range of possible outcomes and a non-zero probability of unexpected behaviour. Ideally, controls are put in place to manage the positive and negative consequences of unexpected behaviour and to provide parties with confidence that risks are well managed. Frameworks for developing geotechnical models across the project life cycle exist and are used to explore how we make decisions, why risks are realised, risk controls and their effectiveness. The discussion is illustrated by examples from case histories. It is concluded that balanced decision making benefits from obtaining high quality data, implementing a live geotechnical model throughout the project life cycle, understanding the simplifications inherent in the model, identifying failure modes, being aware of the limitations of our numerical predictions including bias and scatter, and implementing controls with layers of defence.

Biography

Dr Richard Kelly graduated from the University of Sydney in 1993. He has worked as an academic for 9 years and as a consultant for 22 years.  He largely works on infrastructure projects and specialises in ground improvement, foundations, stability and earthworks. He is a Conjoint Professor of Practice at the University of Newcastle where he collaborates on Bayesian back analysis of embankment settlement, reliability assessments for solar farm foundations and the finer points of soft soil behaviour.  Richard is currently Chief Technical Principal for Geotechnical Engineering and General Manager of Technical Excellence at SMEC Australia.

The need for adequate foundational studies and ground investigation data remains a critical aspect of infrastructure projects. Misrepresentation of actual ground conditions remains one of the leading causes of construction disputes. High profile claims regularly make the news and the blame game starts as to who should bear this risk. 

Some of the most common issues faced by tenderers bidding for a project are inadequate, incomplete or unusable geophysical, geotechnical and environmental datasets. Over the last two decades the potential has been realised for improving data acquisition & ground model outcomes by various digital data acquisition techniques. The improvement of ground modelling and use of can lead to significant reduction of project claim values.

Industry practitioners are increasingly looking at improved site investigation techniques which produce reliable digital data that accurately reflects site conditions. Despite such clear evidence as to the benefits of digital ground models and verifiable ground data coupled with a geotechnical baseline report (GBR), the construction industry continues to operate in silos. While digital data may be collected it is often not shared to those who would most benefit from it. 

There is an industry need to establish a set of protocols for data acquisition and distribution of a project’s ground model. The UK Governments Construction Playbook calls for a model clause saying that all subsurface data (including borehole construction information and any downhole geotechnical and laboratory test data) captured, collected or recorded should be provided as a raw data text file, using the Association of Geotechnical and Geo-environmental Specialists (“AGS”) file format. Proper transparency on the use of ground models and joint verification would go a long way to addressing the incidents of latent conditions claims.

The court cases of Obrascon (2014) and Van Oord (2015) have clearly demonstrated that the tendering contractor cannot simply accept someone else’s interpretation of the available data and say that is all that was foreseeable. Further, these court cases have established that ground investigations are only 100% accurate in the precise locations in which they are carried out, and that it is the role of an experienced contractor to identify and fill in any gaps.

The experienced contractor therefore is increasingly relying on its own interpretation of data points between testing locations. This being the case a high degree of subjectivity may arise which increase the risk of latent conditions claims. Existing contractual frameworks which allow the contractor to fill in the gaps is highly subjective and often falls short of providing clients with adequate protection against latent conditions claims.

The author’s presentation shares thoughts on the past, present and future status of ground data acquisition, ground modelling and latent condition claims and the true notion of the experienced contractor. There will be a focus on the value of procuring good ground data to effectively de-risk a project from the likelihood of a latent condition claim arising.

Biography

David is a Quantity Surveyor with 35 years of international experience dealing with latent condition claims on civil & marine infrastructure projects. David published a book specifically dealing with latent conditions in 2014 as well as publishing articles in the Civil Engineering Surveyor magazine and Terra et Aqua a magazine of the dredging industry.