KDOT Geotechnical & Earthwork Inspection 4 — Questions and Answers
Question 1: A KDOT inspector is overseeing slope grading on a fill embankment. The plan calls for a 2:1 (H:V) slope. If the embankment is 20 feet tall, what is the horizontal distance from the toe to the top edge of the slope?
- 10 feet
- 20 feet
- 40 feet (Correct answer)
- 60 feet
Correct answer: 40 feet
A 2:1 slope means 2 horizontal feet for every 1 vertical foot, so a 20-foot tall embankment requires 2 × 20 = 40 feet of horizontal distance.
Question 2: When using a nuclear density gauge, the inspector must follow NRC requirements including:
- Wearing a hard hat and safety vest only
- Carrying a dosimetry badge and following radiation safety protocols (Correct answer)
- Keeping the gauge at least 50 feet from other workers at all times
- Calibrating the gauge with a sand cone test after every 10 readings
Correct answer: Carrying a dosimetry badge and following radiation safety protocols
Nuclear density gauges contain radioactive sources requiring NRC compliance including dosimetry badges and radiation safety training for all operators.
Question 3: What is the significance of the optimum moisture content range (OMC ± tolerance) specified for fill placement?
- It defines the range where equipment tire pressure does not matter
- It identifies moisture levels where the required density can realistically be achieved (Correct answer)
- It determines the allowable plasticity index of the borrow material
- It sets the range for acceptable proctor test variation
Correct answer: It identifies moisture levels where the required density can realistically be achieved
The OMC window identifies moisture conditions under which the soil can be compacted to the specified density; outside this range, the density target cannot be met regardless of compaction effort.
Question 4: During rock embankment placement inspection, what is the primary concern with oversize rock placement?
- Oversize rocks reduce equipment fuel efficiency
- Large rocks can create voids that prevent proper compaction of surrounding material (Correct answer)
- Oversize rocks increase the risk of embankment settlement during construction only
- Large rocks cause excessive wear on compaction rollers
Correct answer: Large rocks can create voids that prevent proper compaction of surrounding material
Oversize rocks can bridge over each other, leaving voids that cannot be filled or compacted, leading to long-term embankment instability.
Question 5: What does a Unified Soil Classification System (USCS) symbol of 'ML' indicate?
- Medium limestone
- Lean clay of low plasticity
- Inorganic silt of low plasticity (Correct answer)
- Mixed-grain gravel with lime
Correct answer: Inorganic silt of low plasticity
In the USCS, 'M' designates silt and 'L' designates low plasticity, so ML = inorganic silt or very fine sand with low plasticity.
Question 6: An inspector notices that the contractor is placing fill against an existing abutment wingwall without benching the existing slope. What is the primary risk of this practice?
- Excessive noise from equipment near the structure
- A slip plane may form along the interface causing a slope failure (Correct answer)
- The wingwall concrete may be contaminated by soil
- Equipment may damage the wingwall footing
Correct answer: A slip plane may form along the interface causing a slope failure
Without benching, a smooth interface between old and new fill creates a potential failure plane where the new embankment can slide laterally.
Question 7: When inspecting lime stabilization of subgrade soils, how long is the typical mellowing period required after initial mixing before final mixing and compaction?
- 1 hour
- 24 to 48 hours (Correct answer)
- 7 days
- 28 days
Correct answer: 24 to 48 hours
Lime stabilization requires a mellowing period of 24 to 48 hours to allow the lime to react with the clay and reduce plasticity before final mixing.
KDOT Geotechnical & Earthwork Inspection 4
A KDOT inspector is overseeing slope grading on a fill embankment.
The plan calls for a 2:1 (H:V) slope.
If the embankment is 20 feet tall, what is the horizontal distance from the toe to the top edge of the slope?