CO Earth Retention Contractor Exam
(State Of Colorado) Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
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Question 1
What is the primary purpose of earth retention systems?
A. Increase groundwater flow
B. Prevent soil erosion only
C. Resist lateral earth pressures and stabilize excavations
D. Improve soil fertility
Answer: C
Rationale: Earth retention systems such as retaining walls, sheet piles, and
soldier piles are engineered to resist lateral soil pressures and maintain stability
of excavations or slopes. While they may incidentally reduce erosion, their
primary structural function is to counteract earth pressure and prevent collapse
or movement of retained soil masses.
Question 2
Which soil type generally exerts the highest lateral pressure on retaining
structures?
A. Gravel
B. Clay
,C. Dry sand
D. Silt
Answer: B
Rationale: Clay soils, especially when saturated, exert higher lateral pressures
due to cohesion and water retention. Unlike granular soils, clay can retain water
and develop significant active and passive pressures, increasing load demands
on earth retention systems.
Question 3
What is the active earth pressure condition?
A. Soil at rest against a wall
B. Soil expanding away from a wall
C. Soil moving toward a wall
D. Soil in a frozen state
Answer: B
Rationale: Active earth pressure occurs when a retaining structure moves
slightly away from the soil, allowing the soil mass to expand and mobilize its
minimum lateral pressure state. This condition reduces lateral forces compared
to at-rest conditions.
Question 4
Which of the following is commonly used as a deep earth retention system?
A. Asphalt paving
B. Sheet piles
C. Concrete sidewalks
D. Brick veneer
Answer: B
Rationale: Sheet piles are interlocking steel, vinyl, or timber sections driven into
,the ground to retain soil or water. They are widely used in deep excavations and
waterfront structures due to their strength and installation efficiency.
Question 5
What is the function of a tieback anchor in retaining walls?
A. Increase soil density
B. Transfer lateral loads to stable soil or rock
C. Drain groundwater only
D. Reduce wall height
Answer: B
Rationale: Tieback anchors are tension elements installed into stable soil or rock
behind a retaining wall. They transfer lateral earth pressures from the wall to
deeper, more stable ground, improving wall stability and reducing structural
demand.
Question 6
Which factor most affects lateral earth pressure magnitude?
A. Paint color of the wall
B. Soil unit weight and friction angle
C. Weather forecast
D. Concrete curing time
Answer: B
Rationale: Soil unit weight and internal friction angle are key geotechnical
properties that directly influence lateral earth pressure. Heavier soils and lower
friction angles increase pressure on retaining structures.
Question 7
, What is a soldier pile wall typically constructed with?
A. Timber planks only
B. Steel H-beams with lagging
C. Plastic sheets
D. Asphalt layers
Answer: B
Rationale: Soldier pile walls consist of vertical steel H-beams driven into the
ground, with horizontal lagging (wood, precast concrete, or steel) installed
between piles to retain soil. They are common in urban excavations.
Question 8
What is the purpose of lagging in earth retention systems?
A. Waterproofing only
B. Filling voids between piles to retain soil
C. Increasing soil permeability
D. Reducing concrete strength
Answer: B
Rationale: Lagging fills the spaces between structural members like soldier piles,
preventing soil from collapsing into the excavation while allowing staged
excavation and support installation.
Question 9
Which condition represents passive earth pressure?
A. Soil pushing away from a wall
B. Soil at rest
C. Soil being compressed against a structure
D. Soil fully saturated
Answer: C
Rationale: Passive earth pressure occurs when soil is compressed against a
(State Of Colorado) Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
Question 1
What is the primary purpose of earth retention systems?
A. Increase groundwater flow
B. Prevent soil erosion only
C. Resist lateral earth pressures and stabilize excavations
D. Improve soil fertility
Answer: C
Rationale: Earth retention systems such as retaining walls, sheet piles, and
soldier piles are engineered to resist lateral soil pressures and maintain stability
of excavations or slopes. While they may incidentally reduce erosion, their
primary structural function is to counteract earth pressure and prevent collapse
or movement of retained soil masses.
Question 2
Which soil type generally exerts the highest lateral pressure on retaining
structures?
A. Gravel
B. Clay
,C. Dry sand
D. Silt
Answer: B
Rationale: Clay soils, especially when saturated, exert higher lateral pressures
due to cohesion and water retention. Unlike granular soils, clay can retain water
and develop significant active and passive pressures, increasing load demands
on earth retention systems.
Question 3
What is the active earth pressure condition?
A. Soil at rest against a wall
B. Soil expanding away from a wall
C. Soil moving toward a wall
D. Soil in a frozen state
Answer: B
Rationale: Active earth pressure occurs when a retaining structure moves
slightly away from the soil, allowing the soil mass to expand and mobilize its
minimum lateral pressure state. This condition reduces lateral forces compared
to at-rest conditions.
Question 4
Which of the following is commonly used as a deep earth retention system?
A. Asphalt paving
B. Sheet piles
C. Concrete sidewalks
D. Brick veneer
Answer: B
Rationale: Sheet piles are interlocking steel, vinyl, or timber sections driven into
,the ground to retain soil or water. They are widely used in deep excavations and
waterfront structures due to their strength and installation efficiency.
Question 5
What is the function of a tieback anchor in retaining walls?
A. Increase soil density
B. Transfer lateral loads to stable soil or rock
C. Drain groundwater only
D. Reduce wall height
Answer: B
Rationale: Tieback anchors are tension elements installed into stable soil or rock
behind a retaining wall. They transfer lateral earth pressures from the wall to
deeper, more stable ground, improving wall stability and reducing structural
demand.
Question 6
Which factor most affects lateral earth pressure magnitude?
A. Paint color of the wall
B. Soil unit weight and friction angle
C. Weather forecast
D. Concrete curing time
Answer: B
Rationale: Soil unit weight and internal friction angle are key geotechnical
properties that directly influence lateral earth pressure. Heavier soils and lower
friction angles increase pressure on retaining structures.
Question 7
, What is a soldier pile wall typically constructed with?
A. Timber planks only
B. Steel H-beams with lagging
C. Plastic sheets
D. Asphalt layers
Answer: B
Rationale: Soldier pile walls consist of vertical steel H-beams driven into the
ground, with horizontal lagging (wood, precast concrete, or steel) installed
between piles to retain soil. They are common in urban excavations.
Question 8
What is the purpose of lagging in earth retention systems?
A. Waterproofing only
B. Filling voids between piles to retain soil
C. Increasing soil permeability
D. Reducing concrete strength
Answer: B
Rationale: Lagging fills the spaces between structural members like soldier piles,
preventing soil from collapsing into the excavation while allowing staged
excavation and support installation.
Question 9
Which condition represents passive earth pressure?
A. Soil pushing away from a wall
B. Soil at rest
C. Soil being compressed against a structure
D. Soil fully saturated
Answer: C
Rationale: Passive earth pressure occurs when soil is compressed against a
