CTB Ballast & Subgrade Preparation 2

Question 1

What is the primary purpose of undercutting ballast during track maintenance?

Accepted Answer

To remove fouled ballast from beneath the ties and replace it with clean ballast

Answer

Undercutting removes contaminated fouled ballast from under and around ties, restoring proper drainage and structural load support to the track section.

Question 2

What does the term 'surfacing' mean in track maintenance and construction?

Accepted Answer

Lifting and tamping the track to restore correct grade, cross level, and surface geometry

Answer

Surfacing refers to the process of raising the track to proper grade and eliminating surface irregularities using ballast tamping and track lifting equipment.

Question 3

Which property of ballast is most important for ensuring good drainage performance?

Accepted Answer

Particle angularity and interconnected void space (porosity)

Answer

Angular ballast particles create large, interconnected void spaces that allow water to drain rapidly away from the track structure.

Question 4

What is the purpose of geotextile fabric when installed in a railroad track structure?

Accepted Answer

To act as a separator and filter between ballast and subgrade, preventing particle migration

Answer

Geotextile fabric separates the ballast from the subgrade while allowing water to pass through, preventing fine particles from migrating upward into the ballast layer.

Question 5

What equipment is typically used to compact newly placed subgrade fill material in track construction?

Accepted Answer

Vibratory roller or plate compactor

Answer

Vibratory rollers and plate compactors apply dynamic compaction energy to achieve the required density in subgrade fill materials.

CTB - Certified Track Builder Practice Test

CTB - Certified Track Builder Practice Test

CTB Ballast & Subgrade Preparation 2