LOUISIANA ROADWAY SUBGRADE
EXAMINATION WITH ACTUAL QUESTIONS
AND VERIFIED ANSWERS, PLUS
EXPLAINED RATIONALES/EXPERT
VERIFIED FOR GUARANTEED 100% PASS
2026/LATEST UPDATE/INSTANT
DOWNLOAD PDF
1. During construction of a roadway subgrade, the primary purpose of
the subgrade is to:
A. Provide the final riding surface for traffic
B. Support the pavement structure and distribute imposed loads to the
underlying soil
C. Prevent all water from entering the roadway
D. Replace the need for base-course material
Answer: B. Support the pavement structure and distribute imposed
loads to the underlying soil
Rationale: The subgrade is the prepared soil foundation immediately
beneath the pavement structure. Its strength, stiffness, uniformity,
drainage characteristics, and moisture condition directly affect
pavement performance. A weak or highly variable subgrade can cause
rutting, settlement, cracking, and other pavement failures even when
the upper pavement layers are properly constructed.
2. Which soil property is most directly associated with the ability of a
roadway subgrade to withstand repeated wheel loading without
excessive deformation?
1
,A. Plasticity index alone
B. Bearing capacity and stiffness
C. Soil color
D. Organic content alone
Answer: B. Bearing capacity and stiffness
Rationale: A roadway subgrade must possess sufficient strength and
stiffness to resist deformation under repeated traffic loading.
Depending on the project specifications, this performance may be
evaluated using tests such as California Bearing Ratio (CBR), resilient
modulus, density/moisture relationships, or other approved strength
tests.
3. A contractor is preparing a clayey subgrade for a roadway. The soil
is substantially wetter than its optimum moisture content. Which
condition is most likely?
A. Maximum achievable dry density will automatically increase
B. The soil may become unstable and difficult to compact
C. The soil will always become stronger
D. The soil will become nonplastic
Answer: B. The soil may become unstable and difficult to compact
Rationale: Excess moisture in fine-grained soils can produce
pumping, rutting, weaving, kneading, and unstable working
conditions. When soil is significantly wetter than its optimum moisture
content, compaction may become ineffective because the water
occupies pore spaces and prevents the soil particles from being
rearranged into a dense structure.
4. What is the principal purpose of a moisture-density relationship
test such as the Proctor test?
2
,A. To determine the pavement's asphalt content
B. To determine the relationship between moisture content and
achievable dry density
C. To determine the roadway's traffic volume
D. To determine the thickness of concrete pavement
Answer: B. To determine the relationship between moisture content
and achievable dry density
Rationale: A moisture-density test establishes the relationship between
water content and dry density for a particular soil and compactive
effort. It provides an optimum moisture content and corresponding
maximum dry density that can be used as a basis for field compaction
control.
5. The term "optimum moisture content" refers to the moisture
content at which:
A. Soil contains no water
B. The soil reaches its maximum dry density for a specified compactive
effort
C. The soil becomes completely saturated under all conditions
D. The soil has its maximum organic content
Answer: B. The soil reaches its maximum dry density for a specified
compactive effort
Rationale: For a specified compactive effort, there is generally a
moisture content at which the soil can be compacted to its highest dry
density. This is called the optimum moisture content. Adding water
beyond that point generally causes dry density to decrease.
3
, 6. A field density test indicates that a compacted subgrade has
achieved only 91% of the specified maximum dry density when the
project requirement is 95%. What should generally occur?
A. Accept the work immediately
B. Remove the entire roadway
C. Take corrective action and recompact or otherwise improve the
deficient area
D. Apply asphalt directly over the deficient area
Answer: C. Take corrective action and recompact or otherwise
improve the deficient area
Rationale: A field density below the specified requirement indicates
inadequate compaction unless an approved alternative acceptance
provision applies. The deficient material generally needs additional
processing, moisture adjustment, recompaction, replacement,
stabilization, or another approved corrective measure before
acceptance.
7. Which of the following is a major cause of nonuniform roadway
subgrade performance?
A. Uniform soil classification throughout the project
B. Consistent moisture conditions
C. Variable soil types and inconsistent compaction
D. Proper drainage
Answer: C. Variable soil types and inconsistent compaction
Rationale: Changes in soil type, moisture, density, groundwater
conditions, and construction procedures can create weak spots.
Pavement structures perform best when the subgrade provides
relatively uniform support. Abrupt changes in support can contribute
to differential settlement and pavement distress.
4
EXAMINATION WITH ACTUAL QUESTIONS
AND VERIFIED ANSWERS, PLUS
EXPLAINED RATIONALES/EXPERT
VERIFIED FOR GUARANTEED 100% PASS
2026/LATEST UPDATE/INSTANT
DOWNLOAD PDF
1. During construction of a roadway subgrade, the primary purpose of
the subgrade is to:
A. Provide the final riding surface for traffic
B. Support the pavement structure and distribute imposed loads to the
underlying soil
C. Prevent all water from entering the roadway
D. Replace the need for base-course material
Answer: B. Support the pavement structure and distribute imposed
loads to the underlying soil
Rationale: The subgrade is the prepared soil foundation immediately
beneath the pavement structure. Its strength, stiffness, uniformity,
drainage characteristics, and moisture condition directly affect
pavement performance. A weak or highly variable subgrade can cause
rutting, settlement, cracking, and other pavement failures even when
the upper pavement layers are properly constructed.
2. Which soil property is most directly associated with the ability of a
roadway subgrade to withstand repeated wheel loading without
excessive deformation?
1
,A. Plasticity index alone
B. Bearing capacity and stiffness
C. Soil color
D. Organic content alone
Answer: B. Bearing capacity and stiffness
Rationale: A roadway subgrade must possess sufficient strength and
stiffness to resist deformation under repeated traffic loading.
Depending on the project specifications, this performance may be
evaluated using tests such as California Bearing Ratio (CBR), resilient
modulus, density/moisture relationships, or other approved strength
tests.
3. A contractor is preparing a clayey subgrade for a roadway. The soil
is substantially wetter than its optimum moisture content. Which
condition is most likely?
A. Maximum achievable dry density will automatically increase
B. The soil may become unstable and difficult to compact
C. The soil will always become stronger
D. The soil will become nonplastic
Answer: B. The soil may become unstable and difficult to compact
Rationale: Excess moisture in fine-grained soils can produce
pumping, rutting, weaving, kneading, and unstable working
conditions. When soil is significantly wetter than its optimum moisture
content, compaction may become ineffective because the water
occupies pore spaces and prevents the soil particles from being
rearranged into a dense structure.
4. What is the principal purpose of a moisture-density relationship
test such as the Proctor test?
2
,A. To determine the pavement's asphalt content
B. To determine the relationship between moisture content and
achievable dry density
C. To determine the roadway's traffic volume
D. To determine the thickness of concrete pavement
Answer: B. To determine the relationship between moisture content
and achievable dry density
Rationale: A moisture-density test establishes the relationship between
water content and dry density for a particular soil and compactive
effort. It provides an optimum moisture content and corresponding
maximum dry density that can be used as a basis for field compaction
control.
5. The term "optimum moisture content" refers to the moisture
content at which:
A. Soil contains no water
B. The soil reaches its maximum dry density for a specified compactive
effort
C. The soil becomes completely saturated under all conditions
D. The soil has its maximum organic content
Answer: B. The soil reaches its maximum dry density for a specified
compactive effort
Rationale: For a specified compactive effort, there is generally a
moisture content at which the soil can be compacted to its highest dry
density. This is called the optimum moisture content. Adding water
beyond that point generally causes dry density to decrease.
3
, 6. A field density test indicates that a compacted subgrade has
achieved only 91% of the specified maximum dry density when the
project requirement is 95%. What should generally occur?
A. Accept the work immediately
B. Remove the entire roadway
C. Take corrective action and recompact or otherwise improve the
deficient area
D. Apply asphalt directly over the deficient area
Answer: C. Take corrective action and recompact or otherwise
improve the deficient area
Rationale: A field density below the specified requirement indicates
inadequate compaction unless an approved alternative acceptance
provision applies. The deficient material generally needs additional
processing, moisture adjustment, recompaction, replacement,
stabilization, or another approved corrective measure before
acceptance.
7. Which of the following is a major cause of nonuniform roadway
subgrade performance?
A. Uniform soil classification throughout the project
B. Consistent moisture conditions
C. Variable soil types and inconsistent compaction
D. Proper drainage
Answer: C. Variable soil types and inconsistent compaction
Rationale: Changes in soil type, moisture, density, groundwater
conditions, and construction procedures can create weak spots.
Pavement structures perform best when the subgrade provides
relatively uniform support. Abrupt changes in support can contribute
to differential settlement and pavement distress.
4
