NETTCP Soils and Aggregates 5

Question 1

What does the term 'well-graded' mean when describing aggregate gradation?

Accepted Answer

Particle sizes are distributed across a wide range with few gaps

Answer

Well-graded aggregate has a continuous distribution of particle sizes that allows smaller particles to fill voids between larger ones, improving density and stability.

Question 2

In New England transportation projects, frost depth considerations are critical because:

Accepted Answer

Freeze-thaw cycles cause heave and subgrade weakening during spring thaw

Answer

In New England's cold climate, frost penetrates deep into pavement structures, and spring thaw weakens saturated subgrades causing pavement heave and failure.

Question 3

Which field test provides a quick assessment of subgrade bearing capacity during construction?

Accepted Answer

Dynamic Cone Penetrometer (DCP) test

Answer

The Dynamic Cone Penetrometer provides a rapid in-situ measure of subgrade strength by tracking penetration rate per blow, correlating to CBR values.

Question 4

Organic soils are generally considered poor subgrade materials primarily because:

Accepted Answer

They compress significantly under load and have low shear strength

Answer

Organic soils compress significantly under load due to decomposable material, resulting in excessive long-term settlement and insufficient bearing capacity.

Question 5

The purpose of a geotextile fabric placed between subgrade and base course is to:

Accepted Answer

Provide separation, filtration, and prevent subgrade intrusion into base

Answer

Geotextile fabric separates weak subgrade from the aggregate base, prevents intermixing, and allows drainage while maintaining structural integrity.

(NETTCP) New England Transportation Technician Certification Program Practice Test

(NETTCP) New England Transportation Technician Certification Program Practice Test

NETTCP Soils and Aggregates 5