Excavators

Question 1

Elaborate on the 4 steps in site prep

Answer 1

a) Right of Way Felling – Cutting of standing and down trees (20 meters wide or +/- 3m)
b) Clearing – Stack timber out of immediate construction area
c) Grubbing – removal of stumps, roots, etc.
d) Stripping – removal of unsuitable materials organics, silt, clay

Question 2

Elaborate on subgrade construction

Answer 2

• movement of rock and other material to create roadbed (unstabilized width), ditches, cut and fill slopes.

• Culverts are not usually installed yet (just some cross ditches)

Question 3

Elaborate on ballasting (stabilization)

Answer 3

• Make a road surface suitable for traffic with a layer of well graded materials
• Try to use on site materials as much as possible (a lot cheaper)
• Borrow Pits may be needed to supply shortage of materials
• Usually need – rock drill, excavator, FEL, trucks, cat for spreading ballast

Question 4

Elaborate on drainage installation

Answer 4

• Usually occurs as you ballast up to the culverts or bridges if you are using metal pipes
• Because you can drive them up to the site and deliver the culverts from the back of a truck
• For wooden culverts they can be built concurrent with subgrade

Question 5

Elaborate on surfacing

Answer 5

This step is often skipped if ballast is suitable. If ballast is unsuitable the road is surfaced with a erosion resistant material

Question 6

Shovel vs Excavator?

Answer 6

Shovels push to dig

Excavators pull to dig

Question 7

Applications of digging bucket and typical size.

Answer 7

• All granular materials and fractured rock
• +/- 2 yards
• Most common general use

Question 8

Cleanup bucket application

Answer 8

No teeth so harder to break out materials but good for leaving a smooth surface like ditching…

• Large capacity puts more stress on boom
• Good for loading trucks
• Good for stripping

Question 9

Rock breaker attachment

Answer 9

• Break up to medium hard rock without using explosives
• Useful when working in residential areas
• Need special plumbed machine

Question 10

What are excavators good at?

Answer 10

– Digging at a distance

– Separate materials

– Place and pile logs, rocks, stumps etc.

– Good on soft ground

– Split puncheon for culverts

Question 11

Name some suitable applications of excavators

Answer 11

• Extensive cutting, sidehill
• Deep overburden, silt, clay to separate
• Wet conditions
• Deep ditches
• High cutbanks
• Placing and building culverts

Question 12

What are some conditions that can effect excavator productivity.

Answer 12

• Type of material

– moist loam or sandy loam is good -100%

– Poorly blasted rock is bad – 40 to 50 %

• Angle of swing: A full 180 degree swing to load trucks is slow - 60 % reduction
• Bucket size and type: Use the proper bucket for the application

Question 13

As conditions get more difficult, what happens to cycle time and bucket size?

Answer 13

Bucket size is reduced and cycle time increases, reducing production.

Question 14

What is the standard utilization rate for excavators?

Answer 14

83%

Question 15

What are the typical steps in road construction?

Answer 15

1. Site Preparation
   a) Right of Way Felling
   b) Clearing
   c) Grubbing
   d) Stripping
2. Subgrade construction
3. Ballasting (Stabilization)
4. Surfacing / Drainage installation

Usually done in three passes