One of the most common unit operations in mining is drilling and blasting. This is a process during which a rock mass undergoes a transformation from a compact mass to blocks of differentiated volume of more or less the same dimensions. In this field, there is an adapted and specific vocabulary. Let’s take a look at some frequently used terms.
Blasthole inclination or angle
“Blasthole inclination (αbi), (°), the angle between the blasthole and a reference plane, normally the horizontal plane.”
Bench height
“Height of bench (Hb), (m), the vertical distance between the floor and top level of a bench.”
Subdrilling length
“Subdrill, length of blasthole drilled below the planned level of breakage at the floor in bench blasting. subdrilling length (lsub), (m), the length of subdrilling.”
Burden
“Burden in bench blasting (B), (m), shortest perpendicular distance between the centre line of a charge and the free or buffered face.
Spacing
“Spacing (S), (m), distance between boreholes in a row. It is necessary to distinguish between spacing in drilling (Sd) and spacing in blasting (Sb).” The variants are as follows:
“Spacing in blasting (Sb), (m), the distance between holes initiated on the same delay number. In some blasts when all holes are initiated with different delays the spacing in blasting is defined as the distance between holes detonated consecutively. Spacing in drilling (Sd), (m), the distance between adjacent holes in a row of holes located parallel to the blast front or free surface.”
Stemming
Stemming length (ls) (m), the length of stemming, is the length of the blasthole at its collar that is not filled with explosives and is packed with inert material as defined herein:
Stemming, the inert material of dense consistency, such as drill cuttings, gravel, sand, clay, or water in plastic bags, which is inserted in the collar of the drill hole after charging and used to seal the hole temporarily in order to prevent venting of gas, increase blasting efficiency, to reduce air shock waves or dampen any open fames. In coal mining water stemming cartridges work very well as they also contribute to minimise dust and fires. Stemming is also used as a material to separate explosive charges in a borehole (decks). Stem ming can also be used to seal off open cracks intersecting the blasthole.
Specific charge
Specific charge (q) (kg/m3) or (kg/t) is the consumption (planned or actual) of explosive per cubic metre or metric ton of rock.
Hole-to-hole delay
Hole-to-hole delay (tHH) is the time delay used between two adjacent blastholes in order to fire these at different timings.
Row-to-row delay
Row-to-row delay (tRR) is the time delay used between adjacent rows so as to fire the holes at different timings.
Objects of concern
Objects of concern (OCs) are objects that are amenable to blast-induced damage, injury, or fatality and are detailed later.
Blast danger zone
Blast danger zone (BDZ) is the zone around blasting, generally stipulated or fixed by regulatory authorities, that must be secured and cleared of OCs before blasting. Special permissions are required to blast within BDZ.
