Abstract

Paste backfill or pastefill, has become the industry standard for sustainable mine fill; minimizing surface tailings storage requirements, while maximizing resource recovery underground through improved local and regional stability.

To realize all the benefits of paste backfill, a “good” product must be produced, meeting all the specified uncured and cured material properties, including ingredient quantities, rheology, early strength, and final strength. When these specified properties are not met, the impact on safety, the environment and mining production can be catastrophic.

While the immediate short-term consequences (blocked lines, paste spills, etc.) of bad paste are well known, the long-term downstream consequences and related costs are rarely totaled and reflected upon, as mine planning and operations adjust in haste and the mining cycle continues. These long-term consequences include re-working mine designs, additional underground development requirements, mass failure into adjacent stopes, significant paste dilution affecting skip production and mill performance, delay of sequences and sterilization of ore. These costs, stemming from “bad paste” are typically absorbed by multiple departments, such as engineering, mine haulage/development, mine backfill and the processing plant. As such, the costs are rarely totalized and attributed to the “bad paste” incident.

This paper looks at four case studies where an incidence of “bad paste” has negatively impacted the mining operation. The cost of the downstream flow-on effects that can be attributed to the original “bad paste” events have been examined. The quantification of these costs will help operations justify the upfront costs of good quality backfill engineering, construction, instrumentation, engineers, and operators that are often overlooked in attempts to reduce capital and operational expenditure.