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Rock Mechanics and Rock Engineering

, Volume 52, Issue 10, pp 4057–4070 | Cite as

Influence of Joint Conditions and Blast Design on Pre-split Blasting Using Response Surface Analysis

  • A. K. RainaEmail author
Original Paper
  • 217 Downloads

Abstract

Blasting is a major method of excavation in mining, civil construction and infrastructure projects. The integrity of the rockmass of the final wall after excavation is important for the stability and economics of the operation. Perimeter blasting achieves a planned surface of the rockmass. The pre-split is one such technique, deployed when there is no free face and, thus, involving several interactions of rockmass properties, including strength, joint spacing and joint orientation, with respect to blastholes, blast design, explosive configuration, blasthole deviations and other variables. The mechanism and models of the pre-split are perfunctory, particularly in defining interactions of pre-splitting variables. The basis of pre-splitting vis-à-vis dominant variables affecting performance is, accordingly, discussed here. Since the half cast factor, generally used for damage assessment, has its limitations, the index of blast damage has been compared while modelling performance. Models using response surface analysis for pre-splitting, for both blast damage index and half cast factor, were developed using historical data. The angle of the blasthole with respect to the major joint orientation, spacing of the joints, blasthole spacing, drill deviation, linear charge concentration and compressive strength has been used to compare the above-mentioned damage criteria. Blast damage index has been found to be a better predictor for determining rockmass damage due to blasting. The desirability of the variables deployed has been determined using optimization procedures. A fresh impetus to pre-split studies is expected to provide a ground for future research, particularly studies using advanced computational and numerical algorithms.

Keywords

Blast damage Perimeter blasting Contour blasting Rock properties Joint orientation Response surface analysis 

List of Symbols

Sj/Sb

Ratio of joint spacing to pre-split hole spacing

f(Sj/Sb)

Resolved values of Sj/Sb

qlc

Linear charge concentration (kg/m)

θ

Angle of inclination of blasthole between blasthole and major joint orientation in radians

δdd

Drill deviation

σc

Unconfined uniaxial compressive strength (weighted average) also referred to as UCS or uniaxial compressive strength of the rock

σt

Tensile strength of intact rock

σtd

Dynamic tensile strength estimated from compressive strength

dh

Blasthole diameter

pb

Estimated blasthole pressure

pn

Normal component of blasthole pressure

pt

Tangential component of blasthole pressure

vmax

Peak particle velocity

ρr

Density of rock

vp

p-Wave velocity of rock

k

Rock constant

IBD @1m

Blast damage index calculated at 1 m from blasthole and HCF% is half cast factor percentage

Notes

Acknowledgements

The author is thankful to the Director CSIR-Central Institute of Mining and Fuel Research, India, for his permission to publish the paper. The sponsorship of APGENCO is gratefully acknowledged. Thanks to all my colleagues for their help and cooperation during data generation. My profound thanks to Sri Ramesh for his critical views all along the study. Thanks to Suraj for help with references and Geeta and KP Madhu for critically examining the text for errors. Thanks to anonymous reviewers whose initial criticism has helped in improving the paper significantly.

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Copyright information

© Springer-Verlag GmbH Austria, part of Springer Nature 2019

Authors and Affiliations

  1. 1.CSIR-Central Institute of Mining and Fuel ResearchNagpurIndia

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