Safe rapid drifting - Support selection

F. T. Suorineni, P. K. Kaiser, J. G. Henning

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)

Abstract

Current drift advance rates in mining fall short of expectations with advances in drilling and blasting technologies. Quick access to orebodies improves their net present value (NPV). This is critical for block cave mining where several kilometers of drift network is initially required at high capital cost. Many mining companies are now planning block caving because of its long-term low production cost. This paper critically reviews the developments in tunnelling and mine drift development rates with advances in drilling and explosives technologies. Current drift support practice during development is also critically reviewed together with the rock mass classification systems. These reviews show that, while drilling and explosive technologies have drastically improved since 1850, current drift advance rates in the Canadian metalliferrous mining industry have either remained stagnant or dropped below the1960 advance rate levels and in comparison to advance rates in civil tunnelling. It is also established that a major cause for this stagnation is the use of long-term support in good ground conditions where only temporary support is required near-face for worker safety in the short-term. Long-term support takes up 46% of development cycle time. The paper presents a methodology for drift support design for underground hard rock conditions typically found in current mining practice in the Canadian Shield and discusses the rationale for optimizing ground support systems installed near-face during drift development. An improved Q-system called Q-star (Q*) that accounts for discontinuous joints (rock bridges) and roughness of short joints in the rock mass is developed to more reliably estimate the self-support capacities of rock masses. It is recommended that construction damage be accounted for in the rock mass rating for safe support selection during development. A procedure is developed for the adjustment of Q* to account for construction damage. Perimeter blasting is recommended as pre-requisite for rapid drift development in order to minimize construction damage, reduce support demand and scaling and mucking times. A support matrix is presented based on rock mass quality and stress level for safe rapid drift development. Two case histories in active mines are presented to validate the procedure. The methodology is applicable to stress-induced damage and may not apply where complete relaxation occurs. While the procedures presented are focused on typical conditions in the Canadian Shield underground mines, they may be applicable in civil engineering tunneling and other underground mines where drill-and-blast is used as the excavation method. Crown

Original languageEnglish
Pages (from-to)682-699
Number of pages18
JournalTunnelling and Underground Space Technology
Volume23
Issue number6
DOIs
Publication statusPublished - Nov 1 2008
Externally publishedYes

Keywords

  • Advance rates
  • Drill-and-blast
  • Mining
  • Rapid drifting
  • Rockmass classification systems
  • Support matrix
  • Support selection

ASJC Scopus subject areas

  • Building and Construction
  • Geotechnical Engineering and Engineering Geology

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