Publications

The pore water pressure (PWP) has a significant effect on effective stress and strength development in cemented paste backfill (CPB) structures. Moreover, the PWP has a considerable impact on stability and design of barricades. Hence, it has paramount and practical importance for stability analysis as well as the cost-effective design of CPB structures and barricades. In this study, a multiphysics model is developed and successfully validated against laboratory and field data to assess and predict the development and evolution of PWP within CPB mass. A series of engineering issues are then examined with the model to investigate the PWP in field CPB mass with respect to the changes in the mixture recipe, as well as the backfilling, surrounding rock and curing conditions. The obtained results provide in-depth insight into the PWP evolution in CPB.

Paste backfill and uncemented rockfill are used at the Éléonore gold mine to allow pillarless recovery of the narrow gold veins. A major constraint of the Éléonore operation is to store the sulphide tailings underground. Maximizing uncemented rockfill underground is an important economic factor. A good balance of paste backfill and uncemented rockfill is critical to allow the mill to discharge the sulphide material without compromising paste quality and the continuous mill operation.

This study is part of an ongoing internal research program that aims to find an economical mix design with desired fresh and hardened properties at high sulphide content. The effects of the different mix parameters were evaluated independently using the compressive strength at different curing times. All of the mixes were batched at the same consistency. This paper covers the mix design philosophies and challenges encountered during full-scale implementation tests along with innovative techniques used at the Éléonore paste backfill plant.

Cemented paste backfill (CPB) with excellent flow ability and a high rate of early strength gain achieved in an economical manner is a key target in the backfill technology. This paper presents the results of an experimental investigation of the effect of a novel chemical admixture (Master Glenium 7500) on the rheological properties (yield stress, viscosity) and mechanical properties of CPB. The yield stress and viscosity of CPB samples containing 0%, 0.05%, 0.125% and 0.25% admixture were tested up to 4 hours. Unconfined compressive strength (UCS) of the samples was also determined after 1, 3, 7 and 28 days. The results obtained show that the admixture significantly reduces the viscosity and the yield stress of CPB. The admixture also proved to be important for strength development. At the initial stage, up to 3 days curing period, samples with admixture show lower UCS but become stronger than the treated samples after 7 days. This shows that this admixture can significantly improve the rheological properties, strength and strength gain rate of CPB. The findings of this study will, therefore, help to prepare CPB with enhanced performance properties.

This paper discusses the paste design and the experimental results of using an environmentally benign additive known as engineering backfill fiber (EBF), which can potentially and significantly reduce of the cost of paste backfill. It was found that paste with EBF produced less bleed water and developed higher strength. The improved high early strength allowed a more flexible mining and backfill schedule. EBF may also be used for managing the risk of liquefaction and improve safety. The tailings, binder, and water used in this series of experiments were collected in a real world mining process.

The results discussed in this paper highlighted a Feasibility study of overburden material (OBM) from mines as stowing/backfill material. The study refers significant physical parameters like particle size, dry density, porosity, permeability etc. The flow characteristic i.e. pressure gradient change for slurry transport of OBM for 37.5 mm circular pipe have been experimentally evaluated. The linear expressions related with change in pressure gradient have been presented using multiple regressions of data. Water percolation characteristic after placement of slurry also have been evaluated experimentally. The commonly used stowing material; sand is taken for the comparative analysis with overburden material.

With the development of information technology, digital mines has become a development goal of the mining enterprises in recent years. The equipment intelligent, automation production, management information mining mode of production is being extended gradually, the digital management system of filling has become an important project of digital mined development. This paper studies the remote automatic filling process control, material concentration and flow rate of the real-time monitoring technology, to develop a suitable metal mines filled automatic control system. The system is applied in a copper mine enterprises. The test results show that the system realizes the production equipment and process for remote status monitoring and management, optimize the number of staff, reduce labor intensity and improve packing efficiency, to achieve a continuous and stable mine production.

In order to meet the need of efficient backfills in some low grade and hard-to-recover mines, a new backfilling method named short-processing tailing-storage-free filtration backfilling method was invented by studying on the quantity and concentration control of filtrated slurry, as well as optimizing of mine operating flowchart and cyclone clusters. No tailing storage is required for this system; as a result, tailings can be transported to cyclone clusters directly. Generally, the concentration and production rate of the downstream inside the cluster is between 68% to 72% and 69% to 72% respectively. This downstream then flow directly down to the continuous mixers for the mixing with cement, and ultimately, was filled into the voids through underground reticulation systems and boreholes. The installation time for this system has been reduced to 4 months, while the capital investment and operating cost are also reduced by 70% and 20% respectively. The strength of the filling body, with ratio of cement to sand 1:4, can reach up to 3.2Mpa in 28 days. Therefore, this system can be effectively integrated with the overall mining sequence, balance the mineral extraction rate and processing rate safely, hence to improve the profitability of the mine.

The benefits of incorporating chemical admixtures into mine paste fill designs are numerous and cost effective, especially when incorporating metrics such as energy- and cement consumption, reduced dewatering costs, reduced downtime and pipe blockages as well as reduced plant maintenance costs into the equation. The addition of admixtures is a tool to optimize the backfill product in order to have a direct feedback on the backfill quality and numerous operating cost centres. Using admixtures provides the paste fill engineer with a tool to adjust and modify many variables of the paste mix. The following variables can be modified in order to obtain a cost performing backfill paste: enhanced rheological behaviour (better thixotropic profile, improved slump, better pumpeability), reduced water content, reduced cement content or change of cement type, increased solid content, improved compressive strength and improved cure time. An adjustment to any of the mix design variables can result in significant improvements of the paste cost-performance and reduction in overall operational expenses. Test results have proven that the addition of a single admixture at relatively low dosage of 1% to 3% by weight of cement can have powerful effects in modifying the parameters listed above. A prerequisite for good results is a good understanding about the mineralogy and granulometry of the ore host and therefore the source of the tailing material which leads to a customized adjustment of the used admixture in any given paste backfill operation. This paper outlines results from different mine backfill pastes and how to come up with the right admixture choice.

Wear is the result of material loss due to impingement, impact, scuffing, and the sliding of particles across the material surface. Add to that the many other variables which affect the wear rates such as pressure, temperature, velocity, and particle size just to name a few. With that being said wear is very application specific. There are a few standard tests such as the National Bureau of Standards (NBS), DIN and the Taber Abrasion that provide guidance, but often specific field tests must be conducted to determine the best material. This presentation describes the relationship between lab data and field results with various types of cast polyurethane systems. In the end, experience in various operating environments is often needed in order to select the proper polyurethane system for the specific wear service.

There are many forms of backfill that can be considered for a specific mine application and the mine plan, layout and mining method are all key criteria required to develop the appropriate backfill properties. In some instances, a high strength fill may be required for large bulk open stopes and aggregate fill may be the best solution. However, generating suitable aggregate can present logistical challenges and so is often considered an expensive option, but in cases where development waste is readily available, a cemented aggregate fill (CAF) may be an appropriate and cost effective solution. Open stope mining creates large voids and properly designed backfill is used to ensure regional stability as well as to maximize the extraction ratio. CAF is broadly defined as a rock fill that can be modified to suite the mining requirements by optimizing the particle size distribution through a combination of screening, inclusion of tailings or crushing of the waste rock, and adding binder such as cement. The requirements to conduct UCS test work on CAF presents unique challenges and a specially designed and constructed 50 tonne load frame was developed for this test work. This paper presents results from a series of laboratory scale tests on CAF to determine the effect of particle size distribution on the unconfined compressive strength (UCS) so as to optimize the binder content of a CAF backfill product.

Backfill production can be challenging in a mining environment in which multiple mining methods are in use (longhole, overhand & underhand cut and fill). It becomes even more complex when there are multiple headframes, two processing facilities, and associated pastefilling facilities, and where many small, high grade stopes take priority over all others. The complexity of this type of operation in a mine that is mature and where the stoping areas are widely spaced and deep, can present many obstacles to maintaining the ideal inventory of stopes ready to fill and the reticulation to support.

Numerous associated obstacles over time led to a backlog of 80,000 tons of unfilled stopes. Such a deficit is very difficult to overcome when the pressure to meet targeted ounce production can lead to short term decisions which eventually create long term pain.

This paper describes the actions that were taken to completely overhaul the backfill process, eliminate the backlog and implement a sustainable system that will ensure the future success of the mine.

Through innovative improvements, via a structured team approach, with a focus on design flexibility, improved processes, optimization, and a simple mantra "do every task as soon as you can do it," significant step changes in backfill management were achieved.

Changes to organizational structure, planning, scheduling, and coordination, along with optimized preparation, transportation, and distribution, were achieved through the introduction of a philosophy where through team work, collective awareness, understanding, and ownership successful outcomes are achievable.