Insights from the Ballina bypass prediction exercise

Dr Richard Kelly

March 2, 2017

Establishment of a national soft soil field testing facility was a Legacy of the Ballina Bypass Alliance. Prediction of embankment settlement at the design stage of BBA proved to be inaccurate in many cases during construction. Use of the Observational Method during construction allowed actions to be taken that overcame the effects of inaccurate initial predictions, but at a cost. To investigate reasons for inaccurate predictions, the Centre of Excellence for Geotechnical Science and Engineering (CGSE) University of Newcastle node constructed a 3m high embankment over pre-fabricated vertical drains and invited international and Australian academics and practitioners to predict settlement, excess pore pressure and lateral deformations as well as commenting on the uncertainty of their prediction. To facilitate predictions, the CGSE performed a comprehensive site characterisation program along with a high-quality advanced laboratory test program. The prediction symposium was held in Newcastle in September 2016. This presentation summarises the outcomes and lessons learnt of the prediction symposium.