Efficient utilisation of site-won materials is the key component for successful delivery of any earthworks scope. Materials and construction methods need to be fit-for-purpose, providing long term performance confidence for use in earthworks design. The Coffs Harbour Bypass project presents a unique materials management challenge with over 1 million m^3 of material in cuttings requiring blasting within high strength siliceous metamorphic geology (argillite). To meet the earthworks specification for embankment construction this quantity would need to be crushed and processed, placing significant strain on the delivery program and cost.

A project-based method specification was developed to suit the site geology and unprocessed blast condition, providing an efficient mass haul, while ensuring performance requirements can be met over the design life. Laboratory testing, compaction trials and routine engineering geology assessment of the source cuts show that an unprocessed rock fill material can be produced that exhibits a well graded particle size distribution with high strength and durability properties. Analysis of these attributes shows that the contract performance criteria including stiffness and post construction settlement can be met.

Biography

Andrew is an Engineering Geologist with over 30 years of experience in geotechnical testing, consulting, and contracting roles.  This includes extensive geotechnical involvement in over 150km of The Pacific Highway Upgrade as well as other projects involving airports, mining, rail, dams, tunnels, residential and commercial developments.  His key engineering geology interests are earthworks design, slope stability and material resource assessment.  Andrew is currently the Geotechnical Manager for the Coffs Harbour By Pass project.

The New Lambton Landslide occurred during an extreme rainfall event on the night of 22 May 2025. The landslide extended approximately 175 m east–west and 95 m north–south and affected a large residential area between Russell Road, Baker Street, Victoria Street and Portland Place in New Lambton. The landslide caused significant damage to residential properties and public infrastructure and resulted in the evacuation of 16 residential properties.

The presentation provides a background to the nature of the landslide and presents the results of a geotechnical investigation and site monitoring.

The failure mechanism has been identified to be complex, but essentially translational, along a deep shear zone around clay seams associated with the Dudley Coal Seam.

Notable features of the landslide site are the relatively moderate overall slope (~14°), with the site vulnerability to instability arising from a combination of factors, including adverse dip of the regional strata, the presence of jointed, permeable conglomerate over the shear zone, and the presence of clay seams of low shear strength within the subsurface profile.

Biography

Mark Allman completed a PhD at the University of Sydney in 1989 and worked in research and academia in the period to 1999. Mark joined RCA Australia in 2000 and is currently Principal Geotechnical Engineer and Managing Director. He has wide experience in geotechnical engineering and practice within the Hunter Valley and Northern NSW regions.

Expansive soils make geotechnical construction challenging because they can swell, shrink, crack, and deform, often leading to early structural problems. Seasonal wetting and drying cycles worsen these issues, causing uneven settlement. For rail tracks, this can increase the risk of excessive differential settlement. As a result, infrastructure built on expansive soils often requires expensive maintenance, costing rail asset owners billions of dollars each year.

This study investigates coalwash (CW) – expansive soil mixtures to evaluate their suitability as sub‑structure fill materials for rail tracks. A series of consolidated–undrained monotonic and cyclic triaxial tests were performed on mixtures containing 0% to 30% CW to understand their mechanical behaviour. The results show that adding CW reduces soil plasticity, shrinkage, and swelling pressure. It also improves undrained shear strength, resilient modulus, energy dissipation, and the number of cycles the material can withstand before failure. In addition, CW increases the shear modulus of the soil, especially under higher cyclic stresses. An empirical model is proposed to predict the mechanical response of CW–soil mixtures using explicit equations. The model accurately captures the stress–strain behaviour and excess pore pressure development of the mixtures.

Biography

Professor Cholachat Rujikiatkamjorn is an internationally recognised expert in geotechnical engineering and rail infrastructure. His research integrates laboratory testing, field monitoring, and numerical modelling, with a strong focus on sustainable ground improvement and recycled materials. He is a Professor at the University of Technology Sydney (UTS).

This presentation introduces the Kriging method and its applications in geotechnical engineering. Spatial correlation and random field theory are first presented to establish the theoretical foundation of the Kriging method. The implementation of the Kriging method is then discussed. Finally, several engineering applications are presented to demonstrate its benefits.

Biography

Jinsong Huang is a professor at the Priority Research Centre for Geotechnical Science and Engineering, the University of Newcastle. His research interests include risk assessment in geotechnical engineering and computational geomechanics. He has published over 200 journal papers on the risk assessment of slope stability and landslides, the modelling of spatial variability, stress integration techniques for elastoplastic models, the contact dynamics of granular media, the analysis of hydraulic fracturing and the predictive maintenance of railway tracks.

This presentation describes a novel approach to improve the performance of rail tracks through the implementation of a recycled rubber-tyre energy absorbing layer (2REAL) and recycled rubber energy-absorbing grids (REAG). The proposed infilled tyre cell system provides effective confinement to the track substructure, thereby improving its stability and load-bearing capacity. The confinement provided by the tyre cell assembly prevents undue dilation of the granular assembly and increases the load carrying capacity of the track. Additionally, the recycled rubber grids, featuring square apertures fabricated using a waterjet cutting technique, offer significant energy absorption during the passage of trains, and promote enhanced particle interlocking within the granular layers. In tandem, these rubber components contribute to improved track resilience including flood protection, extended lifespan of track, and better structural performance at high axle loads of freight trains.

Multi-stage cyclic loading was carried out using large-scale cubical triaxial apparatus to simulate freight trains with axle loads ranging from 20 to 35 tonnes, at loading frequencies of 10 and 15 Hz. Test results show that the presence of a tyre-cell capping layer beneath the ballast contributed to a reduction in lateral track displacement by providing additional support to the ballast layer. Stress distribution analysis indicated that tyre-cell reinforcement increased the stiffness of the load-bearing stratum by up to 15%, while simultaneously reducing the load transmitted to the underlying layers by up to 20%. Compared to a traditional capping layer, the 2REAL assembly showed a reduction of 40.1% and 28.3% in the breakage index for the crushed latite basalt and spent ballast (i.e. recycled from ballast tips) infilling the tyre cells, respectively. The test data also showed that REAGs reduced lateral displacement, settlement, and ballast breakage, as well as enhancing the resilient track modulus (M_RT) and energy dissipation per load cycle (E_d) of the track.

For performance validation of REAG and 2REAL concepts under real-world conditions, a fully instrumented track section was constructed at Chullora (Western Sydney), Australia. Field testing demonstrated that the installation of REAG beneath the ballast layer reduced track settlement by 18.3% and decreased vertical stresses by up to 27% at the sleeper–ballast and ballast–capping interfaces. Compared with a traditional ballasted track system, the 2REAL configuration significantly reduced stress transfer to the subgrade, thereby mitigating excessive deformation following initial settlement. In summary, these findings indicate that the 2REAL system lowers the risk of subgrade failure and offers a sustainable and practical solution for railway lines constructed over weak subgrade soils.

The AGS data format allows for the transfer of geotechnical data between project stakeholders. Although the format has been around for many years, the AG Society’s 2021 AGS4AU localisation has increased the usefulness of the format in the Australian context, and AGS data format deliverables are now mandated by many contracts. However, many in the industry are unfamiliar with what goes into an AGS file and have little practical guidance on what makes an “acceptable” AGS file. This knowledge gap can lead to acceptance of valueless or non-conforming data sets, or expenditure of unnecessary effort when producing data – both of which are obstacles to adoption of geotechnical data sharing.

Targeted at the non-geodata geek, this presentation will provide an overview of what goes into an AGS file and provide some examples of the value of their contents. It will provide a basic framework for evaluating their contents, and criteria by which project collaborators can assess the quality of the data received.

Biography

Tim has nearly 15 years’ of geotechnical consulting experience including managing and performing geotechnical site investigation works for projects of varying sizes throughout Australia and internationally.  In his current role with Macquarie Geotechnical Tim governs the company’s geotechnical data generation practices including design, training, and supervision of data recording practices to suit client specific, AS 1726, and AGS4AU requirements, as well as collaborating with end users to identify and implement new digital engineering opportunities enabled by the data we produce.

This presentation is a “warts and all” discussion and explanation of some very significant recent advances in CPT testing of soft soils, tailings, and other gooey stuff. Failing to accept and adopt these advances almost certainly leads to poorer quality geotechnical data.

Some of these changes are paradigm-shifting; challenging, over-riding and over-hauling ideas that seemed cemented in geotechnical knowledge, until they recently weren’t.

Biography

Allan is a very experienced Brisbane-based geotechnical engineer, recently granted Honorary Life Membership of Australian Geomechanics Society. His mini-CV is below:

• 38 years in consulting, on major and minor projects; known for championing the practice of uncertainty management and reduction in geotechnical engineering.
• In 1999, he conceived and founded the in situ testing company IGS; motto “Reducing Geotechnical Uncertainty”; and ran this for 20 years.
• Nowadays consulting again; still involved in IGS where/when requested; training and mentoring of staff and clients; and developing/improving in situ techniques.

Allan knows a lot about in situ testing and sampling and will do his utmost to make the discussion interesting and enjoyable.

The automation of numerical analysis in geotechnical engineering offers a transformative approach to achieving sustainable and environmentally friendly designs. This methodology addresses critical challenges such as resource optimisation, cost-effectiveness, and environmental impact by streamlining design processes and enhancing efficiency. This presentation explores how automation can assist to reduce material waste, facilitate energy and time savings, and improve risk management while fostering multidisciplinary collaboration. Real-world case studies demonstrate the tangible benefits of these automated workflows, including significant reductions in design time and costs, as well as the delivery of optimised geotechnical solutions. Automation’s scalability enables the efficient handling of time-consuming analyses across varying scenarios, allowing for tailored, sustainable designs that adapt to diverse conditions, including those influenced by future climate change. Furthermore, the collaborative decision-making supported by automated systems ensures holistic and environmentally conscious outcomes. This presentation highlights the potential of automated numerical analysis to drive innovation and sustainability in geotechnical engineering, paving the way for optimised resource utilisation and reduced environmental footprints.

Biography

Ali is a Senior Associate Geotechnical Engineer with over 20 years of experience spanning both academia and industry. His expertise covers a broad range of geotechnical disciplines, including numerical modelling, soil–structure interaction, ground improvement, deep excavations, retaining structures, slope stability, and the application of AI in geotechnical practice.

He leads the Design Team at JK Geotechnics and serves as a member of the AGS Board of Directors. Ali also chairs the AGS Digital Transformation Working Party and represents Australia on the ISSMGE Technical Committee for Numerical Methods (TC103).

Level 1 controlled fill to AS3798-2007 Guidelines on earthworks for commercial and residential developments is a process, which if followed closely, produces compacted fill able to support complying development on high level footings. However, there are sufficient developments before the courts year after year contesting Level 1 controlled fill reports to make it clear that this process standard has its limitations and flaws.

If an experienced Geotechnician is not present and attentive at all times during fill placement, the fill cannot be assessed as Level 1, as materials, moisture, layer thickness and roller coverage cannot be verified, and so nuclear densometer tests (NDM) carried out to the specified frequency cannot be assessed to be representative of the fill placed. This is key as there can be significant areas where there could be three to five or more layers of fill without nearby results and with compromised observations.

Inexperience, lack of expertise, inattentiveness and commercial pressure are the bane of Level 1 reporting. With limited critical review of submitted Level 1 reports, approval authorities (notably local councils) accept complying and compromised Level 1 reports without being aware.

This paper presents two case studies demonstrating alternative, data driven approaches to produce controlled fill in accordance with engineering principles, one placing part reliance on AS3798-2007 and the other arguably full reliance on the critical elements of AS3798-2007.

The first case study involves remediation of uncontrolled fill and retrospective validation at a former quarry proposed for commercial and industrial warehouse development. The second case study outlines an alternative methodology for active fill placement to achieve AS3798 Level 1 controlled fill during residential land development.

Both case studies utilise Dynamic Probing Super Heavy (DPSH – Grizzly) instrumented penetrometer tests, impact rolling, laboratory index and moisture content tests and limited conventional NDT. For the second case study covering active fill placement, alternative use of a portable handheld Panda variable energy dynamic penetrometer is also considered.

Biography

Robin Power has spent his career pushing boundaries – and encouraging others to do the same. A strategist, educator, and advocate, he brings fresh thinking to civil construction challenges, combining practical experience, theoretical knowledge, and business acumen blended with his manufacturing engineer background.

For over 15 years, Robin has partnered with consultants, asset owners, government agencies, contractors, and researchers across Australia, New Zealand, and the Pacific to implement modern in situ testing and ground improvement methods that boost construction productivity, reduce costs, improve quality, minimise risk, and lower environmental impact.

Robin also champions sustainability as founding chair of Ground Level Alliance.

Mining is a major economic activity in Australia, supporting a wide range of operational and technical roles across the sector. As global demand for minerals continues to rise, the industry faces increasing pressure to optimise tailings‑management practices and improve water recovery, particularly in regions where water scarcity is a significant constraint. At the same time, several high‑profile tailings storage facility (TSF) failures worldwide have intensified scrutiny on the sector, affecting social licence to operate and reinforcing the need for safer, lower‑impact residue‑management solutions. Despite these drivers, the adoption of filtered tailings in Australia remains limited, with conventional slurry systems still dominating current practice.

Internationally, filtered tailings facilities are increasingly recognised as a lower‑risk alternative due to their reduced runout potential and improved water‑recovery efficiency. This presentation draws on global operational experience to examine the geotechnical features that govern the behaviour, stability, and performance of filtered tailings stacks, highlighting their importance from the perspectives of residue management, environmental protection, and impact‑risk reduction. Dewatering tailings to high solids content produces a dense, unsaturated material with higher shear strength, lower compressibility, and reduced pore‑pressure generation, enabling the construction of compacted, trafficable landforms with controlled lift geometry and predictable settlement behaviour.

The unsaturated nature of filtered tailings also greatly reduces the potential for flow‑type failures, lowering both the probability and consequence of environmental impact. These attributes demonstrate how filtered tailings can support safer, more sustainable, and climate‑resilient mine‑waste storage aligned with modern expectations for safety, environmental performance, and long‑term closure outcomes.

Biography

Dr. Gino Vizcarra is a Principal Engineer at Knight Piésold in Brisbane, specialising in tailings and mine waste management, with over 15 years of project experience spanning ten countries. He holds a PhD in Geotechnical Engineering from the Pontifical Catholic University of Rio de Janeiro (PUC‑Rio) in Brazil and has held senior technical roles with major mining companies, including Vale S.A. and Freeport‑McMoRan. His professional focus includes tailings geotechnics, filtered tailings applications, TSF design, and operational risk management across the facility lifecycle.

Dr. Vizcarra has also served as a Soil Mechanics lecturer and geotechnics researcher at the Catholic University of San Pablo in Arequipa, Peru, actively bridging industry practice with academic development. He contributes regularly to industry conferences and technical forums and serves as an advisor to the Peruvian Technical Committee on Tailings and Mine Waste (CT‑200).

Rock slope instabilities, ranging from progressive rockslides to sudden rockfalls, present serious hazards to nearby populations and infrastructure. These failures are commonly governed by the properties of pre-existing discontinuities, such as joints, bedding planes, and faults. Consequently, the identification and characterisation of discontinuities, together with subsequent stability assessments, are fundamental to effective rock slope risk management. A large sandstone column (> 400 m³) located at the northern end of the coastal cliff at South Newcastle Beach is a pertinent case study. Following an episode of intense rainfall (> 240 mm), substantial displacement (0.7 m) was recorded between the column crest and the surrounding rock mass, leading to the temporary closure of the adjacent pedestrian pathway and the initiation of detailed investigations. In view of the presence of major discontinuities behind the column, three-dimensional kinematic analyses were undertaken to assess whether the column exhibited kinematic instability potential prior to the observed movement. High-resolution three-dimensional mesh models derived from photogrammetric drone surveys of the cliff face facilitated detailed geostructural mapping and subsequent 3D kinematic analysis.

Biography

Abigail Watman is a current PhD researcher within the Centre for Geotechnical Science and Engineering (CGSE) at the University of Newcastle. Her research focusses on the application of predictive analytics techniques to rockfall hazard assessment; leveraging expert geotechnical knowledge, proximity remote sensing techniques, and statistical learning approaches. She has shared her work at several national and international conferences, including at the Rocscience International Conference (RIC2025) where she was awarded first prize in the RIC Best Student Paper contest for her work entitled ‘Monitoring and Prediction of Coastal Rockfall Hazard: An Application of RocSlope3 in Newcastle (Australia)’. Abigail earned a Bachelor of Civil Engineering Honours (Class I)/Bachelor of Mathematics (Distinction) from the University of Newcastle in 2022, also receiving a College Medal from the College of Engineering, Science and Environment (CESE). She has been an active member of the AGS Newcastle Chapter committee since 2024 and on the WIAGS subcommittee since 2025.

Dry creeks are commonly constructed as part of mine rehabilitation works to safely allow flow of surface runoff during storm and flood events and establish drainage pathways across reformed landforms. When such channels are constructed within deep backfilled mine voids, their performance is affected by the time dependent settlement of the underlying spoil. Despite this, settlement is not always addressed quantitatively in rehabilitation design, and long‑term settlement predictions for dry creek landforms are rarely documented. Additionally, conventional 1D consolidation theories are not well suited to this problem, where large‑strain behavior and self‑weight creep dominate. This limitation presents challenges for practitioners seeking to readily and reliably predict long‑term settlements.

This study presents a settlement assessment undertaken for a proposed dry creek constructed over a backfilled open‑cut coal mine void located in Muswellbrook, NSW where spoil depths along the creek centerline reach approximately 155 m. The purpose of the assessment was to predict long‑term post‑construction settlement to allow the mine to inform for long‑term planning, inspection, and maintenance requirements.

Settlement estimates were predicted using deep fill settlement frameworks presented in literature and comprise assessment of immediate, creep, and collapse settlements. Settlement predictions were undertaken using a combined analytical and numerical approach. Surface settlement survey data for similar spoil materials previously used by the mine on different projects was available and showed settlements in the order of 0.2% of fill height. Analytical estimates and survey monitoring data were used to benchmark the parameters used in numerical analysis undertaken in PLAXIS 2D (using the soft soil creep model) to simulate staged spoil placement and predict the settlements.

The results indicated that predicted long term settlements using analytical methods are expected to be approximately 0.1% of the fill height. Settlement predictions derived from PLAXIS 2D showed settlements in the order of between 0.2% and 3.3% of the fill height. When benchmarked against analytical method results and survey data, the settlement magnitude of 0.2% of fill height was considered to be representative of actual behavior. Accordingly, the model parameters provided reasonable and comparative settlement estimates for further numerical analysis when ground improvement was applied to near surface. The results from numerical analyses showed insignificant improvement in settlements with ground improvement but was justified for use as it effectively reduces surface deformation and potential collapse settlements.

Biography

Osman is a Geotechnical Engineer at WSP Australia. He has contributed to a wide range of major infrastructure, mining, urban development, and railway projects across Australia and New Zealand. His experience spans across site investigations, geotechnical analysis and design, and construction phase support. Osman’s interests lie in soil–structure interaction and numerical modelling for complex geotechnical problems.

This short presentation will outline some recent advances in the use of Bayesian inference when undertaking back analysis for embankments built on soft soils. A common geotechnical design for treating problematic soft ground is the use of embankments to preload the ground. To confirm that the embankment performance meets the prescribed design criteria, consolidation behaviour is routinely monitored through field instrumentation. This process of observational calibration and validation relies on back analysis where model parameters are refined based on measured field behaviour. Traditionally, back analysis has been performed by manually adjusting key parameters to fit a settlement curve or by using semi-empirical graphical methods. A novel method of back analysis for embankments built over deep soft soil deposits has been developed using Bayesian updating which can incorporate multiple sources of monitoring data directly to update key geotechnical parameters. By using Bayesian updating, the uncertainty around the adopted geotechnical parameters and subsequent settlement prediction can be systematically considered and reduced as more data becomes available.

Biography

Merrick is an Associate Geotechnical Engineer with Beca in Newcastle and a research candidate at the University of Newcastle. His research work focuses on stochastic back analysis and numerical modelling of embankments built on soft soils incorporating Bayesian inference. He is particularly interested in advancing numerical methods to better quantify geotechnical uncertainty.

Small-scale rockfalls of 100 m³ or less are the most common geological hazard on steep rock slopes, and these rockfalls present significant risk to transportation corridors adjacent to rock slopes. Monitoring through remote sensing techniques has been used to track rockfall occurrence on slopes over time and develop site-specific risk assessments, with the end goal of forecasting rockfalls for targeted mitigation efforts.

Rockfalls often display detectable pre-failure deformation, which has been used in limited cases to identify and mitigate potential rockfalls before failure. However, no consistent method yet exists to detect incipient small-scale rockfalls. In this study, we propose an algorithm to identify possible incipient rockfalls from rock slope point cloud monitoring data and test the effectiveness of the algorithm on two sites using previously developed rockfall databases. Rock slope point cloud data was collected over time at the two sites using terrestrial laser scanning and used as input data to the algorithm. First, change was calculated between the base point cloud and each subsequent point cloud. Points with a change value below a given threshold, corresponding to low positive deformation or any magnitude of negative deformation, were removed. The remaining points were clustered and clusters with a number of points below a threshold, corresponding to small areas of possible deformation, were removed. Finally, clusters that occurred in the same location multiple times across different monitoring dates, representing continuous positive deformation over time, were recorded for the purpose of manual evaluation. These point cloud clusters were compared to the known rockfalls that occurred at the sites, and a sensitivity analysis was conducted to determine the effect of algorithm parameters on recall and the number of false positive clusters created.

It was determined that all 7 rockfalls greater than 1 m³ at the two sites were able to be detected prior to failure for some parameter combinations. We postulate that this method has the potential to be used to forecast future rockfalls at multiple sites with a wide variety of geological characteristics.

Biography

Ellie is a PhD Candidate at Colorado School of Mines in Golden, Colorado, USA, and a member of the American Rock Mechanics Association. Her work focuses on rockfall forecasting on steep rock slopes adjacent to transportation corridors using point cloud monitoring data.