CCIL CCIL - Canadian Council of Independent Laboratories Soil Testing and Geotechnical Analysis Questions and Answers 2

Question 1

Which ASTM standard covers the Modified Proctor compaction test used when higher compactive effort is required for subgrade evaluation?

Accepted Answer

ASTM D1557

Answer

ASTM D1557 specifies the Modified Proctor test using a 10 lb hammer dropped 18 inches in 5 layers, simulating higher energy compaction.

Question 2

In a hydrometer analysis of fine-grained soils, what physical law governs the settling velocity of particles in suspension?

Accepted Answer

Stokes' Law

Answer

Stokes' Law relates particle diameter to settling velocity in a viscous fluid, forming the theoretical basis for hydrometer analysis of silt and clay fractions.

Question 3

What is the purpose of the meniscus correction applied when reading a hydrometer during a particle-size analysis?

Accepted Answer

To account for the curved water surface at the hydrometer stem

Answer

Because the hydrometer stem is read at the top of the meniscus rather than the bottom, a meniscus correction is added to all readings.

Question 4

During field density testing with a nuclear density gauge, what type of radiation is used to measure soil moisture content?

Accepted Answer

Neutron radiation from an Americium-Beryllium source

Answer

Neutron radiation from an Am-241/Be source interacts with hydrogen atoms in water molecules, allowing indirect measurement of soil moisture content.

Question 5

What AASHTO classification would a soil with a liquid limit of 45 and plasticity index of 20 most likely fall under?

Accepted Answer

A-7-6

Answer

A soil with LL > 41 and PI > 11, where PI > LL - 30, classifies as A-7-6, indicating a highly plastic clay poor for subgrade use.

CCIL - Canadian Council of Independent Laboratories Practice Test

CCIL - Canadian Council of Independent Laboratories Practice Test

CCIL CCIL - Canadian Council of Independent Laboratories Soil Testing and Geotechnical Analysis Questions and Answers 2