The document discusses drilling and blasting operations for mining. It explains that drilling accounts for 65% of blasting costs while explosives account for 30%. It describes factors to consider for drilling like depth and rock properties. There are different types of drills from handheld to track mounted. The document also discusses blast design terminology like burden, spacing, stemming. It provides formulas to calculate burden, spacing, stemming and explosive charge quantities. The goal is finer fragmentation with a spacing to burden ratio over 1, delay detonators and higher explosive charge.

1. DRILLING
BENCH BLASTING
&
ECONOMY

2. ECONOMICS OF BLASTING
OPERATIONS
DRILLING - 65%
EXPLOSIVES - 30%
FIRING
SEQUENCE - 05%

3. DRRILLING:
FACTORS TO BE CONSIDERED BEFORE
DRILLING:
• Nature of area
• Depth of hole
• Extent to which rock is broken..
• Out put size.
CLASSIFICATION OF DRILLS:
• Hand Held - Small
• Wheel Mounted - Medium
• Track Mounted - Heavy

4. BENCH BLAST DESIGN

5. BREAKAGE PHENOMENAN:
• Detonation of explosive in any rock mass brings
rock mass in compression.
• Shock wave- All Directions
• Shock wave- After reaching free surface
reflect back.
• Resulting conversion of compression state of rock
mass into tension, and rock breaks into burden
area.
• Most material natural and unnatural are weaker
against tensile strength as compared to
compressive strength.

6. BENCH BLAST TERMINOLOGY
Burden = Distance from 1st row to
Free face-or- between rows.
Spacing = Distance between holes
in a row.
Sub drilling = Drilling below bench
height.
Bottom Charge = High Explosive in
bottom portion.
Column Charge = Low explosive in
column section.
Stemming = Empty portion at top of
hole, to be filled with sand/gravel.

7. PACKING DEGREE OF EXPLOSIVES:
Emulite -150:
95 % -or- 1.25 Kg/Ltr
Wabox 80%:
90% -or- 1.45 Kg/Ltr
ANFO-WAPRIL:
100 % -or- 0.85 Kg/Ltr

8. CALCULATION FORMULAS:
Burden:
Hole dia. in inches = Meter
Spacing:
S = 1.25 Burden
Sub Drilling:
U = .03 x Burden
Stemming:
H0 = Burden

9. CHARGE CALCULATION :
Bottom Charge:
• Concentration = Ib = 7.85 D^2 P
• (D=hole dia in dm , P=packing degree)
• Height = hb = 1.3 Burden
• Quantity = Qb = hb x Ib
Column Charge:
• Concentration = 40 – 50% of Ib.
• Height = Hc = H – Hb – Ho
• Quantity = Qc = Ic x Hc
Total Charge:
• Q = Qb + Qc

10. SPECIFIC CHARGE (kg/m3):
Q = Q / B x S x K
SPECIFIC DRILLING (M / M3):
D = H / Bx S x K

11. Finer Fragmentation:
• Spacing / Burden Ratio > 1
• Use of Delay Detonators
• Higher Specific Charge
Coarser Fragmentation:
• Spacing / Burden Ratio < 1
• Instantaneous Blasting
• Blasting of one row at a time.