Overview

Australia’s underground infrastructure pipeline is expanding rapidly, from metro and road tunnels to caverns for pumped hydro energy storage and subsurface storage facilities. As we push deeper and into more complex ground, reliable estimation of in-situ stress becomes increasingly important for safe, economical excavation design. Yet the conventional ways of measuring stress – overcoring and hydraulic fracturing – are expensive, slow, and often difficult to carry out reliably, especially in weak or complex ground. Meanwhile, the drilling and geophysical logging programs we already run on most projects generate large volumes of borehole data. Much of this data goes underused.

This presentation shows how borehole breakout data, the localised failures that form on a borehole wall when stress concentrations exceed the rock’s strength, can tell us more than just the direction of stress. By analysing breakout geometry, we can also estimate the magnitude of horizontal stresses. The method draws on laboratory testing, 3D breakout geometry extraction, numerical modelling, and machine-learning techniques that estimate rock strength from geophysical logs. This research has been incorporated into BBSET.NET, a free web-based tool that enables practitioners to estimate stress from routine borehole observations.

Key takeaways include: Breakout geometry indicating stress magnitudes, not just orientation. Routine borehole logging data holds untapped value for stress estimation. BBSET.NET utilisation as a practical, accessible tool for project teams.

This event is free for all ATS Members

Learning outcomes

In this event, you will understand:

• using borehole breakouts to estimate underground stress direction and magnitude, getting more value from routine borehole and geophysical logging data
• digital tools and BBSET.NET for practical stress estimation.

Program

• 5.30 pm AEST: Guest arrivals and registrations
• 6.00 pm AEST: Presentation begins
• 6.45 pm AEST: Q/A begins
• 7.00 pm AEST: Event concludes

About the speaker

Joung Oh

Associate Professor – UNSW School of Minerals and Energy Resources Engineering

Dr Joung Oh is an Associate Professor in the School of Minerals and Energy Resources Engineering at UNSW Sydney. He has over 20 years of experience in geotechnical and mining engineering, spanning both industry and academia in the US and Australia.  After completing his PhD, Joung worked as a research associate and licensed Professional Engineer (PE) on projects including rock slope failure analysis, ground movement assessment in urban areas, and underground cavern stability evaluation. From 2009, he served as a senior geotechnical and tunnel engineer at Parsons Brinckerhoff (now WSP), contributing to major tunnel and infrastructure projects in Manhattan and internationally. Since joining UNSW in 2013, Joung has led numerous industry- and government-funded research projects and provided consultancy to mining companies. He currently supervises 11 PhD candidates and has guided 19 postgraduate students to completion. He has authored over 100 journal articles and conference papers and chairs the School’s Teaching and Learning Committee.