Wall friction measurement and compaction characteristics of bentonite powders

Yong Ming Tien, Po Lin Wu*, Wei Hsing Huang, Ming Feng Kuo, Chen An Chu

*Corresponding author for this work

Research output: Contribution to journalArticle

16 Scopus citations

Abstract

This paper presents a new method (referred to as direct method) for measuring wall friction during powder compaction and ejection. The accuracy for wall friction force measurement by both new and conventional methods (referred to as indirect method) were first studied according to the theory of error propagation. The error sources for compact density measurement in both methods were also examined. Based on the accuracy in the measurement of wall friction force and compact density, the direct method is compared favorably to the indirect method. Two bentonites, Black Hills bentonite and Zhi-Hsing bentonite which were considered as the candidate buffer materials for the geological disposal of high-level radioactive wastes were adopted to conduct a series of compaction and ejection tests. The compaction characteristics of bentonite blocks were expressed in terms of compressibility curve, wall friction ratio and friction index. The Gurnham's equation was used to describe the compressibility curve. The effects of the aspect ratio of block on the friction ratio and friction index are discussed from both experimental and theoretical point of views. Ejection profiles of the compacted bentonite blocks during ejection phase were presented. The proposed measuring method is validated by comparing the readings of ejection force recorded by both upper load cell and ring-type load cell.

Original languageEnglish
Pages (from-to)140-151
Number of pages12
JournalPowder Technology
Volume173
Issue number2
DOIs
StatePublished - 19 Apr 2007

Keywords

  • Bentonite
  • Buffer material
  • Compaction
  • Ejection
  • Nuclear waste disposal
  • Wall friction

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