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.

Drill, Blast & Crush rock Motorway Cut - Sequence

Step 1 Strip Topsoil & Overburden Step 2 Drill Blast-holes Step 3 Charge & Stem Holes Step 4 Exclusion Zone - 150 m radius

Resources: Excavator 45 tonne & Dumpers 40 tonne Resources :- Drill Rig & Shot Firer & Helper Resources :- Shot Firer, Helper & Loader

Duration :-

Step 5 Blast & set up Seismographs Step 6 Secondary Breaking of Rock Step 7 Load & Crush Step 8 Load & Haul away from Crusher

Resources :- Explosives & Detonators Resources :- Wheeled Loader & Dumpers

Ratio of Explosives to Rock = 0.3 kgs per m3 Qty & Outputs :- 1,100 m3 or 2,500 tonnes per day Qty & Outputs :- Load 240 tonne or 100 m3 / hour

Jaw Crusher produces 150 mm down fill material.

Typical Charging ( Explosive & Detonators )

Shock wave tube Depth Spacing Burden

Depths

Distance Weight (kgs) - M.I.C. 1 m 5 m 1 m 3 m 3 mExplosives per delay. 2 m 2.7 m minimum depth of Stemming

50 m 5.71 kgs 3 m to plug hole

90 m 18.50 kgs 4 m

200 m 91.40 kgs 5 m Formation

350 m 280.00 kgs 6 m 1 m depth Sub drilling

Effects of Peak Partical Velocity (PPV) values Explosive with Detonator

Note: The PPV is the strength of the vibration Distance to nearest Structure = 90 m

PPV Value Maximun Charge per delay = 18.5 kgs

mm / second

0.5 Perceptible motion level to people Grid ( Spacings by Burden) = 3 m x 3 m

10 Usual limit set on contracts. Volumn of rock per hole = 54 m3

51 Safe Limit by US Bureau of Mines Ratio; Explosives to Rock = 0.3 kgs per m3

127 50% Probability of Minor Plaster damage Charge required = 16.2 kgs

193 50% Probability of Major Plaster damage

Comment / Effect

Resources :- Excavator 45 tonne with 4 tonne rockbreaker

Note :- Typically 30 % of blasted rock to be broken to fit

into the Crusher opening.

Quantities = 2,600 m3 of blasted rock & 0.78 tonne of

Explosives

Quantity / Distance Relationship

for a P.P.V. of 10mm / second

as determined by Trial Blast on site

Depth

6 m

Total

Sub

Drilling

Typical wheeled articulated loader weighs 19 tonne and has a

bucket capacity of 4 m3.

Qty & Outputs :- Excavator 45 tonne will dig & load 190 m3 /

hour

Blasts designed to ensure vibration at nearest structure is below the limit set of 10 mm / second (P.P.V.) and to fragment the

rock so it can be crushed with minimum secondary breaking. Note; Maximum Instantaneaous Charge M.I.C. is the amount of

explosive in kilograms which is detonated at a given moment in time, this determins the vibration.

Sub-drilling is drilling below the required depth to allow for poor

fragmentation at the bottom of blast-hole.

Blast Design Points

• Carry out condition surveys on nearby buildings to record

existing cracks.

• Purpose of Blast; to fragment the rock so it can be loaded into a

crusher with the minimum amount of secondary breaking.

• Design blast to minimise ground vibration & fly-rock.

Down-the-Hole hammer drilling is a percussive-drilling method,

where the percussion ( hitting / hammer action) happens behind the bit

down in the hole and the rotating mechanism is located on the drill rig.

Qty & Outputs :- 30% x 2,600 m3 divided by 30 m3 / hour

=> 26 hours

Qty & Outputs :- 30 holes per shift 110 mm dia x 6m deep Stemming is material placed in the top of a blast hole, overlying

the explosive, which prevents all the explosive energy blowing

out of the top of the hole.

i.e. Place explosive and detonator in hole & fill with 20 mm

aggregates as plug.

Resources :- Jaw Crusher on tracks & Excavator 35 tonne

Drilling Pattern

Crusher Capacity: 300 tonnes per hour, 1100 mm x 700mm opening

150 m

150 m

Burden

Spacings

Underwater Drill, Blast & Dredge Rock

Step 1 Equip Spud Barge Step 2 Install Casing to Rock Step 3 Drill 65 mm dia blast-holes Step 4 Install Ducts & Remove Casing

Resources :- Crawler Crane 30 tonne capacity

Top of duct to be above high tide level.

Step 5 Charge Holes from Work Boat Step 6 Move Barge away from Blast Step 7 Blast Rock Step 8 Dredge Rock & Load Hopper Barge

Qty & Outputs :- 3 hours to load 50 m3 barge

Ratio of Explosives to Rock = 1.4 kgs per m3 of rock. Duration :-

Typical Charging ( Explosive & Detonators ) Notes

Shock wave tube

Plastic Tube 50 mm dia Depth Spacing Burden

Distance Weight (kgs )- M.I.C. 2 m 1.5 m 1.2 m 1.2 m

Explosives per delay.

50 m 5.71 kgs Water90 m 18.50 kgs

200 m 91.40 kgs

350 m 280.00 kgs

Effects of Peak Partical Velocity (PPV) values 1 m 0.7 m depth of Stemming

to plug hole

2 m FormationPPV Value

mm / second 3.5 m 1.5 m depth Sub drilling

0.5 Perceptible motion level to people

10 Usual limit set on contracts. Explosive with Detonator

51 Safe Limit by US Bureau of Mines127 50% Probability of Minor Plaster damage Grid ( Spacings by Burden) = 1.2 m x 1.2 m

193 50% Probability of Major Plaster damage Ratio; Explosives to Rock = 1.4 kgs per m3

Comment / Effect

• Nitroglycerine-type explosive along with non-electric

detonators will be used to maximise the use of delay blasting

techniques to fragment the rock.

• To avoid fly rock the holes will have 700mm depth of

stemming and blasting will be during daily high tide. Stemming

is material placed in the top of a blast hole, overlying the

explosive, which prevents all the explosive energy blowing out

of the top of the hole.

• Blasts to be designed to ensure vibration level at nearest

structure is below the limit set of 10 mm per second P.P.V.

and to fragment the rock so it can be dredged and loaded into

a hopper barge.

Casing used to exclude foreign material and for locating

duct in hole

Resources :- Spud Barge with Excavator 70 tonne &

Hopper Barge

Resources :- Drilling Rig with Drifter aka Tophammer.

Resources :- Tug Boat

Fix depth gauges to existing harbour wall showing the

drill depth below tide level.

Drifter aka Tophammer drilling is a percussive-drilling method,

where both the percussion ( hitting action) & rotating mechanism is

located on the drill rig's boom.

• Trial Blasts carried out to establish the Maximum

Instantaneaous Charge M.I.C. is the amount of explosive in

kilograms which is detonated at a given moment in time.

Blasts are made up of multiple holes with a delay of a few

milliseconds between each one. In this way, the amount of

energy entering the rock at a single moment is reduced, which

lowers the vibration level.

Note: The PPV is the strength of the vibration

Resources: Barge with Spuds, Crawler Crane 30 tonne,

Drilling Rig with drifter hammer and purpose built platform on

front for working over water, Tug & Work Boat, Store,

Canteen, Toilet & Mooring Winches

Quantity / Distance Relationship

for a P.P.V. of 10mm / second

as determined by Trial Blast on site

Set up seismographs at the nearest buildings to monitor

vibration level of blast.

3.5 m

Total

Sub

Drilling

i.e. Place Explosive and Detonator in hole & fill with 12 mm

chips as plug ( Stemming ). Detonating cord connects the

detonators to shore for firing.

Detonators typically have time delays of 25 milliseconds

intervals.

Drilling Pattern - 1.2 m spacings by 1.2 m burden

subdrill by 1.5 m below formation

• Rock Description ; Strong quartzite with medium spaced

discontinuities and highly fractured zones

Drilling Pattern

Depth

Qty & Outputs :-

Qty & Outputs :-

Ducting is used to load holes with Explosives, Detonator &

Stemming

Spacings

Burden

Rotating mechanism & Tophammer

Drill String

C:\Users\David Moloney\Documents\1 Book Construction Planning\1 Haulage & Fill

Fill

Cut

Typical Cut to Fill Situationdavmol .

Step 1 Dig, swing 90* & Load Step 2 Haulage by Dumpers 40 tonne.

Excavator 45 tonne with bucket - heaped capacity = 2.3 m3 Dumper 40 tonne with tailgate - heaped capacity = 22.7 m3

1 km 9 minutes

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

= 1 km every 2 minute

1 km 4 minutes 2 minutes 1 minutes 2 minutes 9 minutes

7 km 4 minutes 14 minutes 1 minutes 14 minutes 33 minutes

12 km 4 minutes 24 minutes 1 minutes 24 minutes 53 minutes

Schedule of Excavator's Outputs

Time to Load Dumpers per Hour

to dig, swing 90* & load 40 tonne

25 tonne 1 m3 30 seconds 2 m3 120 m3 10 minutes 6 nr

35 tonne 1.2 m3 30 seconds 2.4 m3 144 m3 8 minutes 7.5 nr

45 tonne 1.6 m3 30 seconds 3.2 m3 192 m3 6.2 minutes 9.6 nr

70 tonne 3 m3 30 seconds 6 m3 360 m3 4 minutes 15 nr

Granular 10%

Sub soil 30%

Topsoil 40%

Weak Rock 30%

Notes: Hard Rock 50%

An Excavator with a 1.2 m3 bucket digs only 0.84 m3 of subsoil before bulking.

Productivity

Decide on a job efficiency % value to take account of weather, breakdowns, disruptions, queuing, resources

mismatch, site conditions etc .

Bulking Factor

( Bulk Qty ) 40 tonne

Dig, Load, Cart, Tip, Spread & Compact Fill.

per Hour Dumper

Time queue &

load

see below

Tip Cycle Time

Capacity of

Dumper

CapacityCapacity

capacity per Minute

Allow for increase in the volume of material during excavation due to

bulking. ( Increase in volume when material is loosened )

A Dumper 40 tonne with side boards and tailgate has a capacity of

22.7 m3, carries only 17.5 m3 of subsoil before bulking.

( Heaped )

Excavator

Size

Cycle TimeBucket