CO Dam Construction Contractor Exam
Practice Questions And Correct
Answers (Verified Answers) Plus
Rationale 2027 Q&A| Instant
Download Pdf.
1. A dam construction contractor is reviewing subsurface investigation
data before selecting the foundation treatment program for a
proposed concrete gravity dam. Which condition presents the
greatest concern for uncontrolled underseepage and uplift
pressures beneath the structure?
A. Competent, massive bedrock with very low permeability
B. A foundation containing open joints, solution channels, or highly
permeable fracture zones
C. Dense granular soil with a shallow groundwater table but no hydraulic
connection downstream
D. Uniform clay with low hydraulic conductivity and no significant fissuring
Answer: B
Rationale: Open joints, solution channels, and permeable fracture zones
can provide preferential seepage paths beneath a dam, increasing uplift
pressures, internal erosion risks, and the potential for uncontrolled
leakage.
, 2. During construction of an earthfill dam, why is moisture
conditioning of fill material performed before compaction?
A. To eliminate the need for laboratory compaction testing
B. To ensure the material reaches a moisture range that permits effective
density and strength development
C. To increase the particle size of granular materials
D. To prevent all settlement after reservoir filling
Answer: B
Rationale: Proper moisture conditioning helps the fill achieve the
specified compaction and engineering properties because soil behavior
during compaction depends significantly on its water content.
3. A contractor is constructing a zoned embankment dam with an
impervious central core. What is the primary function of the central
core?
A. To provide the principal roadway across the dam crest
B. To resist all earthquake loads without assistance from the shells
C. To reduce seepage through the embankment and control hydraulic
gradients
D. To serve as a permanent drainage blanket
Answer: C
Rationale: The impervious core is designed primarily to limit seepage
through the embankment and reduce the hydraulic gradients that could
otherwise contribute to internal erosion and instability.
, 4. Which construction practice is most important when placing
successive layers of earthfill in an embankment dam?
A. Placing all material in one continuous lift regardless of thickness
B. Ensuring each lift is spread uniformly and compacted to specified
requirements before placing the next lift
C. Allowing uncompacted material to remain overnight so it can dry
naturally
D. Compacting only the outer edges of each lift
Answer: B
Rationale: Controlled lift thickness and thorough compaction are
essential for achieving uniform density, minimizing weak zones, and
ensuring the embankment performs as designed.
5. A filter zone is installed between a fine-grained core and a coarse
drainage zone. What is the principal engineering purpose of the
filter?
A. To increase hydrostatic pressure within the core
B. To prevent migration of fine soil particles while allowing seepage water
to pass
C. To create a completely impermeable barrier
D. To replace foundation grouting requirements
Answer: B
, Rationale: Properly designed filters retain adjacent fine particles while
permitting water flow, thereby reducing the risk of internal erosion and
piping.
6. During excavation for a dam foundation, the contractor encounters
loose, weathered rock overlying competent bedrock. What is
generally the most appropriate initial response?
A. Ignore the weathered material because the dam weight will
consolidate it
B. Evaluate and remove or treat unsuitable material according to the
approved foundation preparation requirements
C. Cover the weathered rock immediately with concrete without
inspection
D. Increase the embankment height to compensate for the weak material
Answer: B
Rationale: Unsuitable or highly weathered foundation material may
have inadequate strength or excessive permeability and should be
removed or treated in accordance with the engineering design.
7. What is the primary purpose of a grout curtain beneath a dam?
A. To increase evaporation from the reservoir
B. To reduce seepage through permeable foundation zones
C. To provide reinforcement for the dam crest pavement
D. To replace all drainage galleries
Answer: B
Practice Questions And Correct
Answers (Verified Answers) Plus
Rationale 2027 Q&A| Instant
Download Pdf.
1. A dam construction contractor is reviewing subsurface investigation
data before selecting the foundation treatment program for a
proposed concrete gravity dam. Which condition presents the
greatest concern for uncontrolled underseepage and uplift
pressures beneath the structure?
A. Competent, massive bedrock with very low permeability
B. A foundation containing open joints, solution channels, or highly
permeable fracture zones
C. Dense granular soil with a shallow groundwater table but no hydraulic
connection downstream
D. Uniform clay with low hydraulic conductivity and no significant fissuring
Answer: B
Rationale: Open joints, solution channels, and permeable fracture zones
can provide preferential seepage paths beneath a dam, increasing uplift
pressures, internal erosion risks, and the potential for uncontrolled
leakage.
, 2. During construction of an earthfill dam, why is moisture
conditioning of fill material performed before compaction?
A. To eliminate the need for laboratory compaction testing
B. To ensure the material reaches a moisture range that permits effective
density and strength development
C. To increase the particle size of granular materials
D. To prevent all settlement after reservoir filling
Answer: B
Rationale: Proper moisture conditioning helps the fill achieve the
specified compaction and engineering properties because soil behavior
during compaction depends significantly on its water content.
3. A contractor is constructing a zoned embankment dam with an
impervious central core. What is the primary function of the central
core?
A. To provide the principal roadway across the dam crest
B. To resist all earthquake loads without assistance from the shells
C. To reduce seepage through the embankment and control hydraulic
gradients
D. To serve as a permanent drainage blanket
Answer: C
Rationale: The impervious core is designed primarily to limit seepage
through the embankment and reduce the hydraulic gradients that could
otherwise contribute to internal erosion and instability.
, 4. Which construction practice is most important when placing
successive layers of earthfill in an embankment dam?
A. Placing all material in one continuous lift regardless of thickness
B. Ensuring each lift is spread uniformly and compacted to specified
requirements before placing the next lift
C. Allowing uncompacted material to remain overnight so it can dry
naturally
D. Compacting only the outer edges of each lift
Answer: B
Rationale: Controlled lift thickness and thorough compaction are
essential for achieving uniform density, minimizing weak zones, and
ensuring the embankment performs as designed.
5. A filter zone is installed between a fine-grained core and a coarse
drainage zone. What is the principal engineering purpose of the
filter?
A. To increase hydrostatic pressure within the core
B. To prevent migration of fine soil particles while allowing seepage water
to pass
C. To create a completely impermeable barrier
D. To replace foundation grouting requirements
Answer: B
, Rationale: Properly designed filters retain adjacent fine particles while
permitting water flow, thereby reducing the risk of internal erosion and
piping.
6. During excavation for a dam foundation, the contractor encounters
loose, weathered rock overlying competent bedrock. What is
generally the most appropriate initial response?
A. Ignore the weathered material because the dam weight will
consolidate it
B. Evaluate and remove or treat unsuitable material according to the
approved foundation preparation requirements
C. Cover the weathered rock immediately with concrete without
inspection
D. Increase the embankment height to compensate for the weak material
Answer: B
Rationale: Unsuitable or highly weathered foundation material may
have inadequate strength or excessive permeability and should be
removed or treated in accordance with the engineering design.
7. What is the primary purpose of a grout curtain beneath a dam?
A. To increase evaporation from the reservoir
B. To reduce seepage through permeable foundation zones
C. To provide reinforcement for the dam crest pavement
D. To replace all drainage galleries
Answer: B
