Open Cut » Overburden Removal
This report describes the recent developments of the Slope Stability Radar (SSR). It covers the engineering development and testing of the early production standard, or beta prototype, as required by this project. This work followed the successful proof of-concept model demonstrated under a previous ACARP project (C6015). The technology developed under these projects is now becoming available to the coal mining industry through a commercial leasing service provided by GroundProbe Pty Ltd, a new company specialising in sensor technologies for the mining industry.
The SSR is a state of the art development for monitoring slope movement. The technology is quite different from all other methodologies currently used by the mining industry. It offers unprecedented sub millimetre precision and broad area coverage of wall movements from a stationary platform positioned 50 to 450 metres back from the wall. The SSR provides a comprehensive and continuously updated picture of the slope movements as they develop. This translates into greater productivity in the sense of lower risk associated with recovery of coal. It also enables direct recovery of areas where under conventional monitoring conditions would be quarantined on grounds of excessive risk.
The SSR is mounted on a trailer for rapid deployment and can be set up to start monitoring wall movement within approximately one hour. The system measures radar reflections from across the whole rock surface allowing the spatial distribution and time evolution of wall movement to be displayed. This is accomplished without the necessity of mounting reflectors on the wall as commonly required for laser based systems. The radar can monitor through 320 degrees horizontally, and 60 to +60 degrees vertically from the horizon level. The radar waves penetrate through rain, dust and haze to give reliable measurements every 15 minutes and continuous operation for many weeks. The measurement technique is tolerant of vibrations and overcomes the need for a highly stable footing required by traditional surveying systems, making it easy to move from one location to another. The system is self powered and designed for minimal maintenance.
Radar displacement images, co registered with digital photography images, are transferred from the radar site to the mine office via a radio telemetry link. Custom written software provides mine managers and geotechnical engineers with a complete picture of slope movements over defined time intervals. The time history of the movement of any selected points or regions on the slope can also be displayed. Also provided is the ability to set movement thresholds that will trigger alarms at the radar site or mine office. This interface and the associated concept of operations were defined with the assistance of a workshop involving key representatives from mines and geotechnical consultants.
This report contains the results of field trials conducted at Callide, Tarong, and Hunter Valley Operations, plus an independent geotechnical consultant report. The radar has proven its ability to monitor the stability of highwalls and lowwall spoil piles in safety critical applications at these mines. During the course of all these tests the radar detected pre cursor movements of three separate lowwall failures. As a consequence, the respective mines were able to reschedule their operations in time to prevent a serious incident.