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

To lower the track profile below its original elevation

Answer

To install new ties without disturbing the existing rail

Answer

To compact the subgrade through vibration from the undercutter machine

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

Painting the top of the rail with a protective coating

Answer

Installing a paved surface between rails at road crossings

Answer

Cleaning the ballast surface with power washing 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

Color and mineral composition

Answer

Weight per cubic foot of the ballast material

Answer

Chemical reactivity with rail steel components

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

To provide electrical insulation between the rails and subgrade

Answer

To replace the need for ballast in light-rail applications

Answer

To waterproof the top surface of the subgrade against all moisture

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

Ballast tamping machine (tamper)

Answer

Rail anchor applicator machine

Answer

Rail saw and magnetic drill press

Question 6

What is a 'ballast section' as used in track engineering drawings?

Accepted Answer

The cross-sectional shape and dimensions of the ballast layer, including depth and shoulder width

Answer

The portion of the project budget allocated to ballast material procurement

Answer

A section of track where ballast has been removed for subgrade inspection

Answer

The specification sheet listing approved ballast material suppliers

Question 7

What is the minimum FRA-required ballast depth under the base of ties for Class 4 track operations per 49 CFR Part 213?

Accepted Answer

12 inches

Answer

4 inches

Answer

6 inches

Answer

8 inches