CUMULATIVE CORE INDEX FOR ROCK QUALITY EVALUATIONS

The cumulative core index is a numerical core logging procedure proposed for evaluating the rock quality in drill cores. It provides an objective, convenient and rapid means of quantifying a fundamental rock mass property. This technique takes into account three potential weakness sources in a rock mass which are the natural discontinuities, core fragments cut by these discontinuities, i.e. broken core zones and the core losses. The cumulative measurements of these variables along the borehole length lead to definition of the cumulative core index as the summation of source percentages with special weights given to discontinuities which separate the intact core lengths that are greater than a specified threshold level. Any increase in the discontinuity number gives rise to increase in the cumulative core index value which implies deterioration in rock quality. In deciding the values of weakness weights of discontinuities, the orientation angle of the discontinuities with the core axis are taken into consideration. The necessary expressions that relate the cumulative core index to the classical core index and the rock quality designation (RQD) are presented on the basis of a negative exponential distribution for the discontinuity spacings. Practical charts are developed for the relation between the cumulative core index and the average discontinuity number. Furthermore, a complete discussion is provided for comparison of the cumulative core index with the RQD. Finally, the applications of the cumulative core index are presented for the discontinuities in the granitic rocks and the ash-fall tuffs.(A)

  • Availability:
  • Corporate Authors:

    Pergamon Press, Incorporated

    Headington Hill Hall
    Oxford OX30BW,    
  • Authors:
    • SEN, Z
  • Publication Date: 1990-4

Language

  • English

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00604830
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS
  • Created Date: Feb 28 1991 12:00AM