Predicting the expected time of slope collapse is an important aspect of managing open pit slope stability as it determines the appropriate actions to be taken. It is important to know when to evacuate but is also useful to know well in advance if a particular slope is creeping towards collapse or whether the deformations measured are unlikely to result in collapse. Having this type of information well in advance allows a mine to plan and execute remedial actions, such as schedule changes, slope angle changes and buttresses, that will mitigate economic as well as safety risks. While several methods of analysing slope monitoring data have been published to date, none have been able to establish themselves as the definite answer to any of these questions. This paper evaluates several previously published methods of predicting the time of slope collapse based on the monitoring data collected for slope instabilities that occurred at two of Rio Tinto's Pilbara Iron Ore operations in 2009 and 2010. The methods tested against the data are: CUSUM, inverse velocity and the slope of velocity and time multiplied velocity (SLO) method (Mufundirwa and Fujii, 2008). The paper concludes by evaluating the effectiveness of each of these methods to serve as early warning of impending failure and to predict the onset of collapse. Both instabilities were managed without injury to personnel and no loss of equipment. Predicting the expected time of slope collapse is an important aspect of managing open pit slope stability as it determines the appropriate actions to be taken. It is important to know when to evacuate but is also useful to know well in advance if a particular slope is creeping towards collapse or whether the deformations measured are unlikely to result in collapse. Having this type of information well in advance allows a mine to plan and execute remedial actions, such as unloading of slopes or building of buttresses, that will mitigate economic as well as safety risks. While several methods of analysing slope monitoring data have been published to date, none have been able to establish themselves as the definite answer to any of these questions. This paper evaluates several previously published methods of analysing slope deformation data against two slope instabilities that occurred in the Pilbara. The two slope instabilities occurred at Tom Price's North Deposit (NTD) in 2009 and West Angelas' Centre Pit North (CEPN) in 2010. Both of these slope collapses were managed without harm to personnel or equipment. The basic failure mechanism for both NTD and CEPN was very similar in that failure occurred on a bedding parallel shale band with stability maintained by several metres of Banded Iron Stone (BIF) preventing the shale band from day lighting. In each case the slope instability was triggered by a reduction in the thickness and quality of the BIF buttress. https://papers.acg.uwa.edu.au/p/1308_74_Venter/ An evaluation of the CUSUM and inverse velocity methods of failure prediction based on J. Venter et al. two open pit in...

A planar failure of approximately 600 kT occurred on the north wall of Centre Pit North (CEPN) at West Angelas Mine site in February 2010. The failure impacted a substantial resource of high grade iron ore and left a number of significant geotechnical hazards on and adjacent to the failure surface. These presented a series of challenges which had to be overcome in order to remediate the failure and reclaim the bulk of the buried ore. A number of recovery options were investigated and presented to management. This paper outlines the plan which was adopted, the challenges encountered during its implementation and the risk management and mining procedures used to bring the remediation and recovery to a successful conclusion. A significant fall of ground occurred on the north wall of CEPN at the West Angelas Mine site on the evening of the 3 February 2010. The failure occurred in the Mount Newman Member of the Marra Mamba Iron Formation, which is comprised predominantly of banded iron formation (BIF) with interbedded shale. Bedding dip was roughly parallel to the overall slope angle, except where it flattened towards the pit, on the lower benches. The failure was due to planar sliding on the NS2 shale, which was daylighted in places, towards the toe of the slope. The resultant failure surface is approximately 112 m high, dipping at an average of 42°. The failed rill heap of approximately 600 kT, covered a significant resource of high grade iron ore.

Rio Tinto Iron Ore's (RTIO) Western Australian mine operations comprises 14 mines with a centralised 'Mission Control' Operations Centre (OC) in Perth, and currently delivers 237 Mt/a ore from over 120 individual open pits. Operational challenges in terms of implementation of effective slope monitoring systems with appropriate visibility of system health and alarm notifications needed to be addressed. The geotechnical, management and support teams are site and Perth based, and all require access to geoscience monitoring data.Historically, each site had an independent monitoring and alarming systems. Transparency of monitoring data, health checks and alarming capabilities were limited. The lack of a system to display temporal geotechnical (slope performance), and hydrogeological monitoring data, with 24/7 alarm and system health status had been identified as a 'gap' following a previous slope instability incident at one of the Pilbara Operations.At project inception, the need for a visualisation and management tool which had a multidisciplinary focus and integrating georeferenced geoscience monitoring data with physical models in near real time, was identified. Consequently the Geoscience Monitoring Data System (GMDS) was developed to address three main requirements: Provide a consolidated overview of all geoscience monitoring data and physical models.  Show monitoring system and device health, and alarm status at a high level. Be integrated with existing slope performance and hazard management systems. This tool is in alignment with Rio Tinto's Mine of the Future and RTIO's Operations Centre vision by using technology to reduce costs, increase efficiency and improve health, safety and environmental performance. It provides the functionality to manage diverse instrumentation data in a consistent, standardised approach to support RTIO's geographically spread expansion plans.

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Rio Tinto Iron Ore (RTIO) operates 16 mine operations in the Pilbara region of Western Australia. At each operation, there could be many active pits that pose a challenge for the effective management of geotechnical risks with limited resources. There are many information sources which the geotechnical engineer uses for risk management, including temporal and non-temporal data that may or may not be georeferenced. This information can be in various places, such as proprietary software, network servers or local devices. Consolidating this information can be time-consuming for the engineer and may not include all available data sources. To address this, RTIO developed an in-house tool for aggregating and visualising data, where all geotechnical data can be accessed in a single platform and also included a dashboard to provide visibility of monitoring status and risk profiles across all RTIO Pilbara operations. Sustainability of an in-house developed tool poses business challenges and a decision was made to explore available external options. Although a number of off-the-shelf applications were identified, none met all the RTIO requirements. The best-fit application was ultimately selected with RTIO working with the vendor to incorporate all defined software requirements. This paper discusses RTIO expectations and requirements for the data aggregation and visualisation application, challenges relating to the in-house system development, the evaluation process for a vendor managed option and development of the application functionality with the selected vendor.