From Wednesday to Friday last week, Peter Smale and Hamish Cattell from our Christchurch office, along with Markham Phillips, Clayton Freeman and Justin Lo from our Nelson team, represented DO at the 2025 New Zealand Geotechnical Society Symposium in Auckland.
Centred on the theme Geotechnical Horizons: Innovations and Challenges, the symposium brought together industry leaders and specialists to explore the latest innovations, trends and challenges shaping the future of geotechnical engineering in New Zealand and globally.
Our team contributed to the conversation by presenting papers, sharing insights and showcasing posters that highlighted their expertise and ongoing work across the field. Here’s a look at what they presented.
Authored by Peter Smale, Elliot Duke & Bjorn Raasch – presented by Peter.
The east coast of Canterbury is characterised by extensive loess deposits, a wind-blown silt that can pose challenges in geotechnical engineering.
Loess soils can be hard, have a high bearing capacity, support vertical cuts, and be stable under high seismic loads. Loess can also be soft and erodible, leading to instability and erosion issues, so how do we tell the good from the bad?
How do we identify problematic loess soil from stable loess slopes, and how do we maintain stability when working with loess soils in Canterbury?
This paper explored approaches to identifying and assessing loess variability, highlighting the importance of ensuring the appropriate loess properties are used in design. It also emphasised that site-specific investigation, including assessment of in-situ soil properties and soil moisture regimes, is required to understand the nature of loess soils and identify the appropriate engineering parameters for design. As well as how multilayered analysis should be considered by geotechnical designers.
Authored by Justin Lo, G. H. Browne & Chris Sandoval – presented by Justin.
Westport is a small town in the seismically active area of the West Coast of New Zealand with a high average rainfall and propensity to flooding.
Layers of well-cemented iron pans up to 200 mm thick have been observed in the Holocene aeolian deposits and late Pleistocene alluvial deposits surrounding Westport, creating elevated perched groundwater levels in the future development area. The iron pan layers typically underlie thick layers of moist to wet silty sands (alluvium or dune deposits) and organic silty clay (uncontrolled fill), conditions potentially prone to liquefaction.
This paper focused on our existing geotechnical investigations in Westport and information supplied by the New Zealand Geotechnical Database to improve understanding and awareness of the geotechnical considerations of iron pan layers in urban development.
Authored by Clayton Freeman, Markham Phillips and Chris Sandoval.
During the August 2022 Nelson rain event, a common hazard was inundation from falling debris or debris flows originating from upslope areas, often beyond individual property boundaries. Handrails designed for fall protection were often found to be only partial effective at temporarily retaining small-scale debris, such as slip debris and rockfall.
At the conference, the team presented a poster summarising their observations from this severe rain event. They discussed current standards of practice and shared insights on key considerations when designing debris barriers in urban environments.
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Davis Ogilvie (DO) is a multidisciplinary consultancy that provides comprehensive engineering, surveying and planning services, as well as specialist expertise in civil, geotechnical and structural engineering and environmental sciences.
With a legacy of over 90 years, we have a wealth of local knowledge and experience, with South Island offices in Christchurch, Nelson, Greymouth, and Timaru.
If you have any questions about these presentations, please feel free to contact the team or one of our offices.
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