Rock Excavatability The excavatability of rock depends mainly on the rock strength & layer thickness (bed spacings) The diagram shows excavation methods given the bed spacings and rock strength descriptions. Excavation methods considered are Digging, Rock breaking and Blasting. Bed Spacings (layer thickness) Rock Strength ( Field Estimation) Very Small - up to 60mm Weak :- Gravel size lumps can be broken by heavy hand pressure. Small - 60mm > 200mm Moderately Weak :- Only edges can be broken by heavy hand pressure. Medium - 200mm > 600mm Moderate Strong :- Can be broken by hammer blows when held in hand. Large - 600mm > 1m Strong :- Can be broken by hammer blows when on a solid surface. Very Large - 1m > 4m Very strong :- Rock chipped by hammer blow. Extremely Strong :- Rock rings on hammer blows, Needs sledge to break. HARD DIG ROCKBREAKER EASY DIG Very Small - Small - BLAST Medium - Large - Extremely Strong Very Large - Very Strong Strong Moderate Strong Moderately Weak Weak Excavatability 3D Diagram for Rock with a Free Face Schedule of Rockbreaking Outputs Rock Description :- Strong with Large bed spacings Plant Excavator 25 tonne with Rockbreaker 2 tonne. 5 m3 / hour 3 m3 / hour Excavator 40 tonne with Rockbreaker 3.5 tonne. 8 m3 / hour 4 m3 / hour Excavator 70 tonne with Rockbreaker 6 tonne. 14 m3 / hour 7 m3 / hour Rock Hammer's Preformance. Rockbreaking - 5 Tips on correct use to achieve efficiency. 1 Place the Hammer at 90* to the workface. 2 Use the excavator boom to press the breaker firmly against the rock. 3 4 Stop the breaker quickly, as idle strokes, after the rock breaks, will damage the breaker. 5 Do not strike in one spot for more than 15 seconds, as the chisel would overheat. Soils - Strength Scale Term Field Identification & Classification Very Soft Extrudes between fingers when squeezed in hand. Soft Moulded by light finger pressure. Firm Can be moulded by strong finger pressure. Stiff Can be indented by thumb. Very Stiff Can be indented by thumb nail . Do not let the chisel move outwards from the breaker when it penetrates the rock. Feed the breaker all the time with the excavator boom. Trenches Rock breakers can be judged by their output power rating which is their single blow impact energy multiplied by the frequency i.e. number of blows per minute. The impact energy breaks the rock and the frequency determines the penetration rate into the rock. Open Areas The Association of Equipment Manufacturers, "AEM", formed the Mounted Breaker Manufacturers Bureau "MBMB", test and issue results known as the AEM-MBMB rating system for breakers.
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Rock excavability, drill & blast, marine & haulage
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Rock Excavatability
The excavatability of rock depends mainly on the rock strength & layer thickness (bed spacings)
The diagram shows excavation methods given the bed spacings and rock strength descriptions.
Excavation methods considered are Digging, Rock breaking and Blasting.
Bed Spacings (layer thickness) Rock Strength ( Field Estimation)
Very Small - up to 60mm Weak :- Gravel size lumps can be broken by heavy hand pressure.
Small - 60mm > 200mm Moderately Weak :- Only edges can be broken by heavy hand pressure.
Medium - 200mm > 600mm Moderate Strong :- Can be broken by hammer blows when held in hand.
Large - 600mm > 1m Strong :- Can be broken by hammer blows when on a solid surface.
Very Large - 1m > 4m Very strong :- Rock chipped by hammer blow.
Extremely Strong :- Rock rings on hammer blows, Needs sledge to break.
HARD DIG ROCKBREAKER
EASY DIG
Very Small -
Small - BLAST
Medium -
Large -
Extremely Strong
Very Large - Very Strong
Strong
Moderate Strong
Moderately Weak
Weak
Excavatability 3D Diagram for Rock with a Free Face
Schedule of Rockbreaking Outputs Rock Description :-
Rockbreaking - 5 Tips on correct use to achieve efficiency.
1 Place the Hammer at 90* to the workface.
2 Use the excavator boom to press the breaker firmly against the rock.
3
4 Stop the breaker quickly, as idle strokes, after the rock breaks, will damage the breaker.5 Do not strike in one spot for more than 15 seconds, as the chisel would overheat.
Soils - Strength Scale Term Field Identification
& Classification Very Soft Extrudes between fingers when squeezed in hand.
Soft Moulded by light finger pressure.
Firm Can be moulded by strong finger pressure.
Stiff Can be indented by thumb.
Very Stiff Can be indented by thumb nail .
Do not let the chisel move outwards from the breaker when it penetrates the rock. Feed the breaker
all the time with the excavator boom.
Trenches
Rock breakers can be judged by their output power rating which is their single blow impact energy multiplied by the
frequency i.e. number of blows per minute. The impact energy breaks the rock and the frequency determines the
penetration rate into the rock.
Open Areas
The Association of Equipment Manufacturers, "AEM", formed the Mounted Breaker Manufacturers Bureau "MBMB", test
and issue results known as the AEM-MBMB rating system for breakers.
Output ;- Excavator 45 tonne - 6 minutes to load 40 tonne Dumper Output ;- See below 7 km 33 minutes
12 km 53 minutes
Step 3 Tip & Spread Step 4 Compaction & Shape side slope
Output ;- Dozer D65 - capacity 40 loads per hour Output ;- Roller Single Drum 16 tonne i.e. spread load of 17.5 m3 every 1½ minutes Average 800 m3 per hour
Schedule of Dumper's Haulage Outputs
Haul Distance Haulage Cycle Loads per hour Volume per hour
Taken as volume for Sub soil before bulking.
1 km 9 minutes 6.67 loads 17.5 m3 117 m3
7 km 33 minutes 1.82 loads 17.5 m3 32 m3
12 km 53 minutes 1.13 loads 17.5 m3 20 m3
Haulage Cycle Times ( load / haul / tip / return )
Haul Distance Time to travel Time to return Average speed 30 km / hour