Engineers Australia

Landslide impacts on the South Coast Railway during the 1988-90 El Nino event

Peter C Stone

Abstract

Major landslides occurred along a 25 km length of the railway connecting Sydney and Wollongong, on the south coast of NSW, as a result of significant and long duration rainfall during the El Nino event of the late 1980s. The impacts commenced with the tragic event at Coledale in April 1988, involving a major embankment failure with two fatalities, and culminated in over 100 individual sites being activated along the route. These sites were mainly embankment failures, but also included rock cutting instability, which were identified and treated progressively under a risk priority and safety management system. The repairs, which cost in excess of $70M, were implemented over a number of years, and included an intensive track closure (track possession) of the South Coast Railway during January 1990. The management system was developed, in close association with SRA personnel, with an over-riding early-warning system linked directly to the railway control co-ordinator in Wollongong.

The paper presents an overview of the instability experienced on the South Coast Railway, and its remediation at the time, the links to antecedent rainfall, and the philosophy of the risk management system. A selection of case histories is given, with their associated monitoring, and a listing of back-analysed geotechnical parameters is provided for reference purposes.

The paper serves to document a presentation given to the Sydney Chapter of the Australian Geomechanics Society in June, 1991 and is intended to be factual as at that time.