PRACTICAL EXERCISE Design a delayed initiation blast (would like to shoot a minimum of 10 holes per delay). Base the plan on the following: Rock - limestone, in thin layers w/tight joints Bench height - 24 ft
PRACTICAL EXERCISE Explosive - bulk ANFO, SG e 0.8 dry holes, no liner required. Explosive - dynamite, SG e 1.4 Cartridge size: 2 to 3.5 inch diameter in ¼ in. increments, by 16 in. long.
PRACTICAL EXERCISE Drills can use 6 in. bits. Regulatory scale distance factor 55 Nearest structure is 1,400 ft away
STEP 1: BURDEN DISTANCE ?
Explosive density empirical formula for burden distance: Equ. 13.1
STEP 1: BURDEN DISTANCE SG e ANFO = 0.8 SG r Limestone (Table 13.2)? D e = ? try 6 in. the maximum
STEP 1: BURDEN DISTANCE SG r Limestone ( ) Lets use an average number of 2.7
STEP 1: BURDEN DISTANCE B = 12.6 ft
STEP 2: BURDEN corrected Burden distance corrected for geological conditions (Table 13.3). K d = 1.00, no information assume “other cases.” K s = 1.10, thin layers w/tight joints
STEP 2: BURDEN corrected. Burden distance corrected for geological conditions. B corrected = 13.8 ft
STEP 3: STIFFNESS RATIO Need a Stiffness Ratio of 3 or greater. Bench height = 24 ft Burden corrected = 13.8 ft
STEP 4: BURDEN ADJUSTED Want a Stiffness Ratio of 3 therefore:
STEP 4: BURDEN ADJUSTED Do not complicate the field work, try to use one foot or half foot increments.