some implications of empiricism and assumptions in laboratory testing

International Journal of Rock Mechanics & Mining Sciences 41 (2004) 374

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doi:10.1016/j.ijrm

SINOROCK2004 Paper 1A 19

Some implications of empiricism and assumptions inlaboratory testing

H. Abdullah*, A.K. Dhawan

Central Soil & Materials Research Station, New Delhi, India

Abstract

Some implications of approximations introduced by empiricism and/or assumptions in the laboratory assessment of rock are

highlighted with the help of discussions on three topics:

* correlation between uniaxial compressive strength and point load strength index;* the use of triaxial compression test data for assessment of c, f, m and s parameters (Fig. 1); and* evaluation of dynamic elastic parameters (based on wave velocities).

In the case of correlation between point load strength index and uniaxial compressive strength, our submission is that the universal

correlation of 20–25 is highly misleading, and the database for the same needs to be specified; also, the instances of different

correlation factors need to be specified, so that one knows which cases one can realistically utilize this correlation. The case of

assessment of c, f, m and s parameters is to show that, in a given case, one or the other theory may or may not be applicable. And,

there could also be situations when none of the existing theories may be applicable, and one might have to improvise. In the third

case of evaluation of dynamic elastic parameters, based on wave velocities, the objective is to highlight that in certain cases the

theories, practices, and/or the empirical relations normally adopted may not be applicable when the underlying assumptions do not

hold good; and unacceptable distortions are introduced if these are used.

The paper presents alternatives to deal with the discussed atypical situations. The submission is that ingenuity is called for to

assess a rock; and the assessment must be holistic. Two things need to be made mandatory: to communicate the test data to a

centralized place, so that suggested relations can be re-examined; and to declare the database on which any relation is based.

Keywords: Rock; Laboratory; Assumptions; Empiricism; Static; Dynamic

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Fig. 1. Strength envelope.

ng author.

sses: habdullah@csmrs.nic.in (H. Abdullah), akd847@csmrs.nic.in (A.K. Dhawan).

th paper see CD-ROM attached.

ms.2003.12.095