Pile integrity testing for monitoring pile construction

Pile Integrity Testing for Monitoring Pile Construction

1. 1
Sanjay Gupta Ravi Sundaram
Sorabh Gupta
CENGRS GEOTECHNICA PVT. LTD.
Pile Integrity Testing for
Monitoring Pile Construction

2. 2
What makes a “good pile”?
To perform successfully, a pile  To perform successfully, a pile 
must: must:
••
Have adequate soil  Have adequate soil  resistance   resistance  
••
Be structurally sound Be structurally sound
These are two separate requirements
Both must be satisfied

3. 3
Low Strain Integrity Methods PP
PILE INTEGRITY TESTING (PIT) PILE INTEGRITY TESTING (PIT) P
Measure Pile Top Motion, Reflections from Defects
PCROSS-HOLE SONIC LOGGING (CSL)
P
Determines Concrete Quality Between Tubes in Shaft
P
For larger augercast piles 
PSINGLE-HOLE SONIC LOGGING (SSL)
P
For smaller augercast piles
PPARALLEL SEISMIC (PS)
P
Hit Pile, Measure Hydrophone in Parallel Tube
P
Determines only Pile Length 

4. 4
QA/QC: PUnplanned Inspection
P
In response to something gone wrong
P
Unplanned costs - project delays 
PPlanned Inspection (
Preferred Preferred
)
P
Included in project specifications
P
Planned costs - normal pay item

5. 5
Why Do Pile Integrity Testing?
•
prime function is to locate major
defects 
(to evaluate 
questionable shafts)
•
inexpensive
, can test many piles
(good for quality 
assurance)
•
no advance selection
required
(good for forensic purposes)

6. 6
Defective Piles

7. 7
PIT Equipment
Accelerometers
Non-Instrumented
Hammer
Instrumented
Hammer

8. 8
PIT looks for defects
Small Hammer
Impact Device
Accelerometer
Measures
Response
Defect
One Person Operated

9. FF
∆∆∆∆∆∆∆∆
LL
Compressed Zone, races
along pile at wave speed c
c c
is the wave speed of the pile material is the wave speed of the pile material
In a time In a time
““
∆∆∆∆∆∆∆∆
tt
””
the wave travels a distance the wave travels a distance
∆∆∆∆∆∆∆∆
L = c L = c
∆∆∆∆∆∆∆∆
tt
Wave Propagation

10. 10

11. 11
Good Pile Good Pile
800 mm drilled shafts
L = 25 m   (L/D = 31)
Bad Pile Bad Pile
Normal test (pile top “free”)PIT -Basic Interpretations

12. 12
Any of these piles could have a defect..
How many piles should I test?

13. 13
Grinding top surface to make flat spot
Pile top preparation is key to good data
which is the key to best interpretation.
Shortcuts cause questionable data.
Preparation..

14. 14
Remove loose
contaminated or fractured
concrete from core; cut
rebar to min lengths

15. 15
Case Study 1: Noida Mall
POngoing Project
P800 mm dia BCIS piles in 
sand
PInitial Cyclic Pile Load Test:
P
Q
ult
=  270 MT
P
Q
safe
= 135 MT
P14 PIT were performed on 
initial and routine piles
0
10
20
30
40
50
60
70
80
90
0 50 100 150 200 250 300 350
Load (MT)
Field Data Extrapolated Values (Hyperbolic Model)
Qsafe (MT) = 135.0
270 MT

16. 16
Case Study 1: Noida Mall
7 m
Original Ground Level
Excavated Level, Pile COL
Pile Toe Level
27 m

17. 17
Case Study 1: Noida Mall
Variations in Pile Cross-section
Major defect at 16~18 m depth (or short pile)

18. 18
Case Study 2: ROB in Malout, Punjab
Good Pile (14 m length)
Weak Toe Response

19. 19
PIT -Low Strain Integrity Testing 
Standards
P
ASTM D5882 (1996)
P
Deep Foundations Institute “Inspector’s Guide to Augered Cast-in-Place 
Piles” 1994
P
Australian Standard AS 2159 (1995)
P
Eurocode 7, Section 7, Pile Foundations 
P
Specification for Piling - Institution of Civil Engi neers (1988) - England
P
CIRIA Document CP/28  (1995) - England
P
Norme Francaise NF P94-160-2 (1993)  - France
P
DGGT Com.2.1 for Pile Integrity Testing (draft Sept 1997) - Germany
P
Slovenia Highway Code
P
Spain Driven Pile Foundations Art.670 (draft 1996)
P
Bangladesh National Building Code  (1993)
P
CED 43 (4917) for concrete piles in IS-2911 (draft 1998) - India
P
Other documents…...
P
(Draft standards may have been further updated and made official)

20. 20
PIT Limitations
P
As per published literature, piles with L/D ratio upto 30 give reasonably 
good results 
P
Highly non-uniform piles may be difficult to interpret 
P
Cracks or mechanical joints block waves
P
Small defects or short length hard to find 
P
Not always applicable: pile type, walls, in structure
P
No direct correlation to pile capacity; but can help to identify which 
piles to load-test

21. 21
Let us strive to achieve.. quality in pile 
construction
THANK YOU…
Cengrs Geotechnica Pvt. Ltd