Burden related to blasthole diameter in rock blasting

• Since the 1950s, most of the empirical formulas in rock blasting have incorporated a linear relation between burden and blasthole diameter. Recently it has been shown that a non-linear relation is more accurate for blasthole diameters in 40-400 mm range. This relation is different for surface and underground mines. In this paper, a complete relation between burden and either blasthole diameter or specific charge is established. This relation is based on energy conservation in single hole blast and consists of three terms which are related to surface energy for the two side cracks, fragmentation for the rock prism released and energy needed to move the rock. Four approximate formulas describing burden as a power function of the blasthole diameter are derived from the complete relation and dimensional analysis. The exponents of the diameter in the formulas are 2, 1, 5/6 and 2/3 and these decrease with the increasing scale in blasting. The coefficients of the power formulas are expressed as functions of the physical properties of the rock and explosive. The linear relation, derived as a special case with comparatively small blasthole diameters, is in a good agreement with Langefors' well-known formula. The valid ranges of the new formulas depend on the rock properties. The formulas were tested against the regression curves from real values in surface and underground mines and the results were better than those obtained using empirical methods.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Samhällsbyggnadsteknik -- Annan samhällsbyggnadsteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Civil Engineering -- Other Civil Engineering (hsv//eng)

Nyckelord

Mining and Rock Engineering

Gruv- och berganläggningsteknik

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