In 2007, during a planned water level raise at the Giant Mine, which had recently been placed into care and maintenance, a large movement of fill occurred in a series of connected vertically stacked cut-and-fill stopes. The movement mobilised over 170,000 metric tonnes of previously placed unconsolidated rock and sand fill and left a 70,000 m 3 void separated from arsenic trioxide storage vaults, by a thin sill pillar. Review of historical mine plans and investigations onsite suggested that timber sill mats and bulkheads which had likely destabilised when the area became variably saturated during flooding, created a connection between remnant voids in the upper and lower mining horizons resulting in the void. Furthermore, it was determined that if the water level was changed again, with either a rise or drawdown that the rock and fill within the stope below the void could once again be mobilised, further reducing the stability of the void. The mine is to be remediated and closed and a permanent solution to stabilising this void, which is approximately 85 to 125 m below ground surface, was required. Given the lack of future underground access and a desire by the project proponent to reduce long-term monitoring and care requirements, a unique solution was required. While stabilising mine voids during active production mining or during mine closure activities, practitioners would typically utilise a cemented mine waste product such as cemented rockfill (CRF), cemented paste backfill (CPB) or cemented sand fill. Because of the potential for the previously placed sand and rockfill in the void to move deeper into the mine void and possibly destabilise the workings, a manufactured sill pillar that would stay in place should the material below it move was required. In this case, it was determined that the void span was sufficiently large that these types of materials would not be self-supporting should such a movement occur. Therefore, a self-consolidating concrete (SCC), also known as self-levelling concrete was used to manufacture a 16,600 m 3 (70 x 24 x 10 m) monolithic concrete sill pillar to be installed.

Records of manual scaling, ground-support checks and ground-support installations are commonly kept in handwritten daily logbooks, as required by mining regulations in Canadian jurisdictions and elsewhere. This process can be fraught with challenges in a large mature underground mine that has been subjected to changing ground-control approaches over its history. Accurate records of ground-support as-builts and of completed maintenance and rehabilitation are needed to show compliance with ground-control management-plan requirements. By combining the power of a database, three-dimensional (3D) visualisation software and simple scripting language driven by ground-support design criteria, the daily logbook can be uploaded to a system that helps the mine confirm ground-support compliance with its ground-control plans and provides a basis upon which to estimate material requirements and ground-support installation duration. The individual mine's ground-support standards can be entered into the database, along with the mine geometry information and local geology, and when compared with records of installed ground support and maintenance records, can be used to digitally check on compliance in a spatial manner. When combined with modern mine design software, all data can then be viewed in 3D or on two-dimensional plan maps to assess where ground-support maintenance, rehabilitation or upgrades are required as well as where periodic check scaling is required. As ground support is installed and the ground-support system maintained, the database can be updated, and a workflow can be followed to visualise where work is required. Maintaining a record of ground-support information with such a tool can be simple and cost-effective and an efficient way to show compliance with a ground-control management system. This paper describes a case study of the application of such a system to a large mature future underground hard-rock gold mine that is to be rehabilitated to allow gradual closure of the property.