ABSTRACT
A failure of a 100m high slope took place in July 1989. The potential for further instability along strike was recognised and a monitoring system was installed. In September 1991 extensometers at the toe of the slope indicated movement of the suspect area was taking place. In April 1992 cracks appeared on surface. The monitoring system was expanded and a clear indication of the type and potential mechanisms of failure obtained.
In October 1992 the instrumentation indicated a rapid increase in the rate of movement and a failure of predicted size and location subsequently took place. Continuous safe access to the underground operation at the toe of the slope was maintained throughout the monitoring period and during failure.
After the failure, monitoring was continued in order to identify and maintain safe working conditions.
The comprehensive monitoring system proved successful in recognising the potential for failure over a year before final collapse of the slope and allowed safe management of the operation at all times.
