Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

FRST 272 - Road Design II > Mass haul > Flashcards

Mass haul Flashcards

1
Q

What does borrow imply on a mass haul diagram

A

Implies that you need a borrow pit outside the roadway

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is free haul?

A

A set distance in contract, defining the distance of earth that must be moved for free. Standard is 300m

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Overhaul distance

A

Distance beyond free haul. Consider wasting if possible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Define ripable rock

A

Rock that is too dense to be excavated without breaking it apart first with a ripper

  • Not so hard that it needs to be blasted
  • Various charts are published describing which materials are rippable by various machines
  • Classified by seismic velocity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Define seismic velocity?

A

Measure of strength of P waves and S waves.

P waves (primary waves) are compression waves in materials propagated by explosion or earthquake. Faster as material gets denser.

The S-wave moves as a shear or transverse wave, so motion is perpendicular to the direction of wave propagation. Slower

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Rock Breakers

A

Hydraulic powered jackhammers that attach to excavators

  • Remove bucket and attach breaker in about an hour
  • Effective in stratified or highly fractured rock of soft to medium hardness
  • Useful in areas where you can’t use explosives (next to buildings, power lines…..)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the objective of drilling and blasting?

A

to fracture rock to the preferred size and leave it in the correct place for use on the road

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are some requirements of controlled blasting

A

Controlled blasting requires a good knowledge of rock, explosives, detonators, and delay mechanisms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How are blasting holes drilled?

A

Require a pneumatic or hydraulic rock drill mounted on various types of carriers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What’s a tank drill?

A
  • All the machinery is mounted on one carrier
  • Called a tank drill because the are mounted on a WWII design tank undercarriage
  • Usually a pneumatic hammer
  • Not very mobile due to tracks
  • Very common on BC coast
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What eventually replaced the tank drill

A

Rubber tired rock drill: All equipment on one carrier

  • Rubber tires mean you don’t need a low bed truck to carry the machine between work sites
  • High mobility means a large operator may replace two tank drills with one RT drill
  • Hydraulic powered hammer is very fast
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe typical bits for rock drills

A
  • Bits used in forestry are 2 1/2 or 3 inches
  • 3 inch holes drill slower but will hold more powder and therefore less holes required (good for quarry work
  • 2 ½ holes are usually suited to general road construction work
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe the drill rod

A
  • This part connects the hammer to the drill bit
  • Usually 10 and 12 foot lengths
  • To drill holes deeper than rod length connect rods with couplers
  • Rods are hollow to feed air to the drill bit for cooling and to eject rock dust
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the 2 explosives categories?

A
  1. Blasting Agents

• Not cap sensitive (a blasting cap won’t set them off)

  1. High Explosives

• Cap Sensitive (a blasting cap will detonate)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe blasting agents?

A
  • Ammonium Nitrate (94%)+ Fuel Oil (6%) is very commonly used in forestry (ANFO)
  • Need a cap inserted into a high explosive primer to set them off
  • Safe and inexpensive
  • Not sensitive to heat, shock, or friction
  • Can be mixed on site (requires a special license) or purchased premixed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the typical blasting agent used?

A

ANFO Ammonium nitrate fuel oil

  • Usually poured into down holes (vertical hole)
  • But can be loaded with a special air compressor in flat holes
  • Must be very careful when blowing into rock with lots of natural fissures (overloading causes excessive fly rock)
  • Not very water resistant
17
Q

Describe high explosives?

A
  • Nitroglycerine based products usually mixed with a stabilizer or organic filler like sawdust
  • Sensitive to heat, shock, friction, moisture
  • Store carefully and use them quickly after manufacture
  • Nitro can cause headaches so don’t breathe the fumes
18
Q

What are the typical detonating systems required?

A
  • Electrical isn’t very common anymore
  • Non electric detonating systems are often used in forestry (E-Z Det, Nonel are some trade names )
  • Use explosive chords to link drill holes

– Prima-cord, E-cord, B-line

• Connectors between lines act as delays

– Delays are in milliseconds

19
Q

How are high explosives packaged?

A

Sausages

Mmm sweet sausages

Maybe u will get a sausage Sammy this morning eh big boy?

That’s right fatty get 2. Don’t forget to breathe

20
Q

Which way should a driller direct the blast?

What are the benefits of proper technique in blasting?

A

Direct blast UP

• Proper drilling, loading and delay techniques will:

– Minimize fly rock

– Provide proper fragment size for usable rock

– Prevent overloading of the fill slope

– Minimize damage to trees

21
Q

What are the sources of energy in borehole blasting?

A
  • Shockwave (p and S waves fracture rock)

- Gas expansion (causes heaving effect)

22
Q

What is burden?

A

Distance from borehole to where cracking will stop. Based on rock density. Important to optimize distance to free space.

23
Q

What does burden depend on?

A

Burden is most important design parameter in blasting ***

Depends on:

– Specific gravity of explosive

– Specific gravity of rock

– hole diameter

24
Q

Define specific gravity

A

the ratio of the density of a given solid or liquid to the density of water. Density of rock / Density of water

25
Q

What is the burden equation?

A

B = [ (2)(SG e /SG r ) + 1.5] De

Where De equals size of borehole, SGe is standard gravity of ANFO on label and SGr is standard gravity of rock

26
Q

What is stemming?

A

• Stemming – Top of borehole filled with inert material to contain gasses

27
Q

Sub drilling

A

drilling past the point where you want the breakage to stop because holes don’t normally break for full length

28
Q

Stiffness Ratio

A

ratio of rock column length to burden (4 is best)

Hole should be 4 times deeper than burden distance.

29
Q

Explains the importance of timing and delays?

A
  • Must allow time for rock to move away for the next row of holes to explode
  • Inadequate delay causes the same problems as too much burden

– Need to allow time for rock to move out of the way so that the subsequent row has a space to move into

• After the blast look at the shape of the pile for clues on proper delays

30
Q

Which way do you haul material?

A

From cut to fill

FRST 272 - Road Design II (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions