ABSTRACT: Two comprehensive surveys, which focus upon backfill practices and the economics of backfilling in underground mines in Canada, have been conducted. The two surveys were designed to assess operational practices and costs associated with the wide scope of filling operations that must be met by individual mines, ranging from raw material feed to the preparation plant, through underground backfill transportation, to in-stope product placement. This paper presents the current state of backfill usage in Canada, identifies trends in minefill practices and provides mine operators with an updated database of information upon which they might compare their own practices and costs with present trends throughout the industry.
Backfilling in Canadian mines has been practiced for close to 100 years and evidence anticipates the application of mine fill technology at an increasing rate during this decade [1, 2]. The evolution of backfill technology is closely related to the establishment of new mining methods. Hydraulically transported tailings and alluvial fills were introduced in the 1950's thus permitting the adoption of cut and fill mining where the backfill was used as a working floor. In the early 1960's cemented hydraulic backfill was introduced, followed by the adoption of undercut and fill, blasthole, and vertical retreat mining methods. The 1990's has been considered by many as the decade of high density tailings fills and pastefills, during which a number of mines have successfully introduced pastefill into their operations . Pastefill, a relatively new technology in mining, is gaining importance because of its many perceived advantages. The reasons behind the conversion to pastefill include economic, environmental, geotechnical and safety improvements. Today, many mines are in the process of converting to this form of backfilling and a number of operations are investigating the possible use of the entire portion of their mill tailings as a component of pastefill with considerable environmental benefits .
The Department of Mining Engineering at Queen's University conducted a survey of backfill practices and a survey of the economics of backfilling in underground mines across Canada. The survey of backfill practices was aimed at assessing the current state of backfill usage and the knowledge base in backfill design, from preparation through transportation to placement. The second survey was aimed at examining the economic aspects associated with backfilling operations in Canadian mines. The information presented for the first and second surveys relates to populations consisting of thirty-three and twenty-three underground mine operations employing backfill, respectively.
The presentation of survey information will evolve into a larger technical work that will be used to promote industrial implementation of new backfill technology within the Canadian mining industry. The eventual goals of this effort will be to reduce backfill energy costs, and enhance both the application of alternative cementing agents in backfill and the development of low-cost multiphase flow technology in pipeline transport.
2. BACKFILL PRACTICES SURVEYT
2.1. Survey Format
A comprehensive questionnaire, consisting of ninety-four questions, was carefully laid out and subdivided into eight components: i) general operation overview, ii) backfill preparation, iii) backfill transportation, iv) stope preparation, v) backfill in situ properties, vi) in situ monitoring and instrumentation, vii) productivity and economics, and viii) failures and remedies.