The Rio Tinto Centre for Underground Mine Construction (RTC-UMC) at CEMI was created to undertake research in support of Rio Tinto’s Mine of the Future™ programme with focus on underground mining infrastructure and footprint reliability. This state-of-the-art research and knowledge centre plays a role in the development and implementation of innovative step-change research and technology development for underground mines, designed to minimize delays and create value through speed and geo-risk mitigation. Rio Tinto designates a significant portion of funding for shared programmes, as part of its annual budget allocation with CEMI. This funding, which can benefit from potential government (Ontario & Canadian) leveraging programmes, is intended to engage other companies in R&D projects that are of relevance to Rio Tinto. Research aims at overcoming key challenges in mine construction and mechanized excavation, and addresses the challenges related to introducing new technologies to perform in highly stressed and naturally variable ground.
ENHANCED FOOTPRINT RELIABILITY
In 2015, RTC-UMC continued its focus on delivering value to Rio Tinto and its operations through “enhanced footprint reliability”, which implies less unforeseen rehabilitation, fewer losses of drawpoints, and thus fewer delays in ore recovery. This will help to ramp-up projects with less uncertainty while introducing more flexibility into the production schedules. Improved support design has been the focus of work since being identified as a key factor in speeding up development, while reducing ongoing rehabilitation costs. The work
program, initiated in mid-2014, recognizes that in order to improve support of the footprint (extraction level), one needs to anticipate both the demand on, and deformation response of extraction level pillars.
To date this year, a combination of experimental (lab), in-situ, and numerical studies (Figure 1) were carried out to substantially improve knowledge of, and enhance predictive techniques for extraction level demand/response and support performance. The ultimate goal being, to provide improved support design guidelines tailored to extraction level development in deep, massive rock. To achieve these goals, RTC-UMC worked with partners in Rio Tinto, academia and consulting in Canada, Chile and the USA.
On the pillar demand side, RTC-UMC worked with MIRARCO and Rio Tinto staff to implement a pillar monitoring study at two mines. The aim of the study is to quantify the impact of draw control strategy on pillar loads and deformation using borehole stress meters and
25 extensometers, which were installed in both the minor and major apexes of pillars located in areas of active draw. The Centre will start to work with Rio Tinto staff on analysis and interpretation, now that data from the installation has become available.
In parallel with these in-situ studies, a number of lab studies employing scaled physical models were carried out at the University of Chile in order to pursue a more systematic investigation of pillar loads as a function of draw strategy. The studies, concluded in June, reached a number of practical conclusions regarding the potential maximum and minimum loads that might be experienced (relative to average cave load) and provided preliminary recommendations for draw control in order to avoid load concentrations.
On the pillar response side, RTC-UMC continues working with Itasca, the University of British Columbia and the University of Toronto to further develop Bonded Block Modelling (BBM), as a state-of-the-art tool for the prediction of explicit spalling, bulking and ground
support performance in extraction levels. This work presents a significant challenge as it demands three dimensional analysis (due to the significant geometric controls on pillar performance at extraction drift/draw drift intersections) and requires careful consideration of the highly localized straining of support elements at discrete fractures that are both opening and shearing.
A number of key advances were achieved. The plan is to put this technology in the hands of Rio Tinto staff by the end of 2015, so that it can be tested, validated and applied within ground support studies across a number of projects and operations.
BEST PRACTICES GUIDELINES
Building on the procedure developed in 2014, the Centre continues to work with Rio Tinto in refining the Best Practices for logging, testing and strength characterization of rock masses. In 2015, the Centre will deliver a companion document covering Best Practices
for ground support design, with special consideration of the spalling ground conditions and large deformations that characterize deep extraction levels in higher quality rock. The results of in-situ studies by MIRARCO (field testing of hybrid bolts) and numerical studies at Simon Fraser University (optimizing support in burst-prone ground) will provide data to assist in the development of these guidelines.
The Centre will also deliver a report in 2016 that documents the outcomes of the first 5 years of RTC-UMC and provides a road map for the future, building on the successes of the Centre to date.
Collaborating organizations include Itasca U.S.; Golder Associates; SRK Consulting; Aker Wirth; Atlas Copco; MIRARCO; Laurentian University; Queen’s University; Universities of Arizona and Toronto; University of British Columbia, Delft University, The Federal Technical University of Zurich, and others to be determined based on required expertise.
Strategic research and development for safe, rapid, mechanized development of underground mines.