Sydney Chapter

2013 – AGS Sydney Young Geotechnical Professional’s Night

Dane Lidgard, Ben Caruana, and Andrew McIntyre

The Young Geotechnical Professionals’ Night is an opportunity to see three selected presentations by young geotechnical professionals discussing interesting and challenging aspects of their work. After the presentations, you will have a chance to catch up with friends and the presenters over drinks and finger food, and see additional posters prepared by YGP’s. The following presentations will be given during the evening.

Dane Lidgard (Aurecon) – Strengthening of an Embankment on a Constrained Site

The development of the Sydney Light Rail Inner West Extension (SLRIWE) along the existing Rozelle Goods Line corridor in Sydney’s inner west has required the use of innovative embankment stabilisation techniques to improve the stability of an existing rail embankment to comply with current design standards. The combination of several factors, including large sensitive embankments constructed in the late 1800s, a constrained site in an urban environment and variable geotechnical conditions often containing layers of low-strength material meant that innovative approaches to this task were required, with a number of different retention systems being developed. This paper describes the stabilisation techniques that were adopted to address this problem in one area of the SLRIWE project, which was the site of a previous embankment slip in the mid-1970s.

Ben Caruana (Golder Associates) – Leachate Barrier Design for an Abandoned Adit at the Woodlawn Bio-Reactor

The Woodlawn Bioreactor near Tarago, NSW collects waste from Sydney for landfill with methane collected as a by- product of the decomposing waste. The bioreactor has been established within the former zinc, copper and lead open pit mine void that cease operation in 1998. As part of the mining activity the two adits were also constructed to give access to minerals away from the pit. The two portals for the adits were constructed on the pit wall face and are referred to as the southern portal and northern adits. As part of the development approval consent for the Woodlawn bioreactor, the two adits were required to be sealed to prevent future landfill leachate seepage. The leachate barrier system is required to have a performance of a 900 mm thick re-compacted clay liner with in-situ coefficient of permeability of less than 10-9 metres per second. This paper discusses the barrier design developed for the southern adit. Some of these design considerations include safety in design and construction, the performance of rock fill distributing stress away from the barrier, the bearing capacity of the rock and potential seepage paths.

Andrew McIntyre (University of New South Wales) – The Shear Strength of Fibre Reinforced Clay

This paper presents a theoretical model that evaluates the increase in shear strength of clay due to the addition of discrete, randomly oriented nylon fibre reinforcement. The model is based on a simple Mohr-Coulomb failure criterion for saturated undrained conditions. A series of 27 direct shear tests were conducted on kaolinite reinforced with 8mm long fibres at fibre contents of 0%, 1%, 2% and 4%, subject to confining stresses of 25kPa, 50kPa and 100kPa. A series of 6 fibre pullout tests were also conducted to evaluate the fibre-soil interaction factor. In general, a good agreement between the theoretical model and the experimental results has been obtained.

Engineers Australia members participating in AGS technical sessions can record attendance on their personal CPD logs. Members should refer to Engineers Australia CPD policy for details on CPD types, requirements and auditing guidelines.