Pile P20 – A Case History
supported by 3D tomography and verified by coring
Erez I Amir. Piletest
Background
Pile P20 is part of a sensitive project so just a few details can be disclosed at this stage.
The pile is ACIP (augered-cast-in-place) 1m diameter and 14m long
The pile was pre-installed with 4 CSL access tubes and was tested more than 5 days after casting.
CSL Test Results
CSL (Cross-Hole Logging) was performed using CHUM (Cross Hole Ultrasonic Monitor) manufactured piletest.com
Testing revealed a significant relative energy (RE) decrease and a matching first arrival time (FAT) increase in profiles 13 and 23, and to a lesser degree also in profile 12 (Images 1, 2)
Image1
CSL results – showing an anomaly at all profiles at the same level
Image 2
A zoom into the anomaly zone, profile 23.
The bars on the left indicate that at 10m both FAT is increased by > 20% and RE decreased by > 12dB
Although the data was tested by 1D CSL and the pile was equipped with just 3 access tubes, a 3D tomography was attempted and reveals the location of the flaw (image 3)
Image 3
A 3D tomography view of the anomaly at 10m, showing velocities lower than 2750m/Sec, higher velocities are transparent
Coring
Following the CSL results, the inspector ordered coring of the pile which confirmed the CSL results (Image 4) – The concrete at 10m was totally washed-out leaving just aggregates.
Image 4
Cores showing the defect
Conclusions
- CSL is a viable test method with few false-positives
- Interpretation is usually straightforward
- 3D tomography supports tough decisions regarding anomalies.
Thanks
As this project is undergoing litigations, we thank the anonymous testing lab for sharing this information with us.
