KDOT Geotechnical & Earthwork Inspection 3 — Questions and Answers
Question 1: According to KDOT practice, what action should be taken when embankment fill material delivered to the project contains significantly more rock than the approved material sample?
- Accept the material if it passes visual inspection
- Reject or quarantine the load and notify the engineer for evaluation (Correct answer)
- Increase compaction effort to compensate
- Reduce lift thickness by 50%
Correct answer: Reject or quarantine the load and notify the engineer for evaluation
Material that deviates significantly from the approved sample must be quarantined and evaluated by the engineer before placement.
Question 2: In a sand cone density test, the weight of sand filling the hole is used to determine:
- The dry density of the in-place soil
- The volume of the excavated hole (Correct answer)
- The moisture content of the excavated soil
- The compaction percentage of the fill
Correct answer: The volume of the excavated hole
The sand of known unit weight fills the excavated hole, and its measured weight is used to back-calculate the volume of the hole.
Question 3: What does the term 'shrinkage factor' mean in earthwork calculations?
- The reduction in soil volume when moisture is lost during compaction
- The ratio comparing the volume of soil in bank measure to its volume when compacted in place (Correct answer)
- The percentage of organic material removed during processing
- The reduction in project quantity due to material rejection
Correct answer: The ratio comparing the volume of soil in bank measure to its volume when compacted in place
Shrinkage factor accounts for the fact that a cubic yard of soil in the borrow pit (bank measure) occupies less volume once compacted in the embankment.
Question 4: Which condition typically requires a KDOT inspector to suspend embankment fill operations?
- Ambient temperature above 90°F
- Active rainfall or standing water in the fill zone (Correct answer)
- Wind speed exceeding 15 mph
- Soil temperature below 60°F
Correct answer: Active rainfall or standing water in the fill zone
Active rain or standing water in the placement zone prevents achieving proper compaction and must cause a work suspension.
Question 5: A KDOT inspector is checking subgrade preparation. Which of the following defects requires correction before embankment placement begins?
- Minor surface discoloration from equipment traffic
- Soft or yielding zones identified by proofrolling (Correct answer)
- Tire tracks less than 1 inch deep from subgrade equipment
- Natural variation in soil color across the subgrade
Correct answer: Soft or yielding zones identified by proofrolling
Soft or yielding zones identified during proofrolling indicate inadequate bearing capacity that must be corrected before fill placement.
Question 6: What AASHTO classification system group would a soil with a PI of 10 and 40% passing the No. 200 sieve most likely fall under?
- A-1-a
- A-3
- A-4 (Correct answer)
- A-7-6
Correct answer: A-4
A soil with significant fines (40% passing No. 200) and a PI of 10 typically classifies as A-4, which is a silty soil with low to medium plasticity.
Question 7: During inspection of a storm drain trench backfill, the inspector finds the contractor is using cohesive material with 85% relative compaction per nuclear gauge. KDOT typically requires pipe zone backfill to achieve:
- 85% relative compaction
- 90% relative compaction
- 95% relative compaction (Correct answer)
- 100% relative compaction
Correct answer: 95% relative compaction
KDOT specifications typically require 95% relative compaction for pipe zone and structural backfill to prevent pipe settlement and damage.
KDOT Geotechnical & Earthwork Inspection 3
According to KDOT practice, what action should be taken when embankment fill material delivered to the project contains significantly more rock than the approved material sample?