Abstract:
A total of 246 bored cast-in-situ piles (240 working piles and 6 test piles) were cast for the main building / factory area using two different types of rigs, hydraulic rotary rig and truck mounted rig (TMRs). After casting about 150 piles using hydraulic rotary rig, truck mounted rigs were used to speed up the piling activity.
After installation of the piles, the client had doubts on quality of piling work executed at site with regard to the structural integrity of the installed piles. To evaluate the condition of pile quality the authors carried out pile testing and confirmatory geotechnical investigation. The paper presents the results of low-strain pile integrity tests (PIT), pile coring, probe holes and soil tests as well as analysis of previous geotechnical investigation and pile load test reports.
Although the pile load tests on the initial piles indicated that the 500 mm diameter 12.4 m long piles are safe for the design loads, low strain integrity tests suggested defects such as variations in pile diameter and short pile length. Typical results are tabulated below:
|
Pile No.
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Type of Rig used
|
PIT Data Interpretation / Test Conclusions
|
|
TP-1
|
Hydraulic Rotary Rig
|
Large variation in pile cross-section with depth. Increase in pile impedance below about 5 m depth.
|
|
TP-4
|
Hydraulic Rotary Rig
|
Early toe response. Pile may be short (9-10 m). Further investigation is required.
|
|
142
|
Truck Mounted Rig
|
Increase in pile impedance below about 10 m depth below the test level.
|
|
182
|
Hydraulic Rotary Rig
|
PIT could not be performed due to improper pile top preparation or presence of weak concrete at the test level.
|
To confirm pile lengths and to assess concrete quality, coring was done through a few piles. Results are tabulated below:
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Pile No.
|
Design Pile Length, m
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Length as per PIT, m
|
Maximum Explored Depth, m
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Actual Pile Length determined from coring, m
|
Observations and Interpretations
|
|
TP-4
|
12.37
|
9.0 - 10.0*
|
14.45
|
9.0
|
Soil was met below 9 m depth. Actual length of the pile is less than the anticipated length.
PIT results suggested pile length of 9-10 m.
|
|
TP-6
|
12.37
|
12.37
|
14.0
|
9.0 – 10.5
|
Actual length of the pile is less than the anticipated length of 12.37 m. Also, steel reinforcement was encountered at about 6.0 to 9.0 m depth.
|
|
TP-1
|
12.37
|
12.37
|
14.45
|
9.75
|
TActual length of the pile is less than the anticipated length of 12.37 m.
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*Updated length as per PIT results which showed reduction in pile length
The paper shall present the details of the study and the conclusions drawn based on the test results and analysis.
Abstract: Theme 2