CTQP Pile Driving Inspection 1 — Questions and Answers
Question 1: What is the primary purpose of a 'driving criterion' or 'refusal' specification for pile driving?
- To set the maximum rate of pile installation
- To define the blow count per inch that indicates adequate bearing capacity has been reached (Correct answer)
- To specify the type of hammer required for each pile type
- To establish the minimum embedment depth regardless of blow count
Correct answer: To define the blow count per inch that indicates adequate bearing capacity has been reached
The driving criterion specifies the blow count (blows per inch or per foot) that indicates the pile has reached the required bearing capacity in the soil.
Question 2: What does 'set' mean in pile driving terminology?
- The total length of pile installed
- The penetration of the pile per blow of the hammer (Correct answer)
- The pre-boring depth before driving begins
- The setback distance from an existing structure
Correct answer: The penetration of the pile per blow of the hammer
Set is the penetration of the pile per hammer blow, typically measured in inches per blow or blows per inch, and is used to assess pile capacity during driving.
Question 3: What information must be recorded on a pile driving log for each pile?
- Only the final tip elevation
- Hammer type, blow counts, driving time, tip and cutoff elevations, and any splices or interruptions (Correct answer)
- Hammer type and final blow count only
- The date, pile number, and inspector name only
Correct answer: Hammer type, blow counts, driving time, tip and cutoff elevations, and any splices or interruptions
A complete pile driving log must record hammer identification, blow counts at regular intervals, driving interruptions, tip elevation, cutoff elevation, splice locations, and any anomalies.
Question 4: What is a 'pile splice' and when is it required?
- A repair weld applied to a cracked pile after driving
- A connection joining two pile sections when the required length exceeds a single pile section (Correct answer)
- A test plug inserted into a hollow pile before driving
- An epoxy coating applied to the pile tip
Correct answer: A connection joining two pile sections when the required length exceeds a single pile section
A pile splice joins two pile segments when the required pile length exceeds the available single-piece length, and must be made using approved methods (welding for steel, mechanical connectors for concrete).
Question 5: What is the purpose of a 'follower' in pile driving?
- A secondary pile driven alongside the primary pile
- An extension piece used to drive a pile when the hammer cannot reach the pile head (Correct answer)
- A monitoring instrument attached to the pile during driving
- A guide frame that keeps the pile properly aligned
Correct answer: An extension piece used to drive a pile when the hammer cannot reach the pile head
A follower is an extension piece placed between the hammer and the pile head to allow driving when the pile head is below the reach of the hammer, such as in water or after cutoff.
Question 6: What is 'pile heave' and why is it a concern?
- The upward movement of previously driven piles caused by driving adjacent piles (Correct answer)
- Excess vibration transmitted through the ground during driving
- Lateral displacement of a pile after driving is complete
- The rebound of the hammer after striking the pile
Correct answer: The upward movement of previously driven piles caused by driving adjacent piles
Pile heave occurs when driving adjacent piles causes previously driven piles to move upward, potentially reducing their capacity and requiring re-driving.
CTQP Pile Driving Inspection 1
What is the primary purpose of a 'driving criterion' or 'refusal' specification for pile driving?