CHUM 2D Tomography: See Inside the Pile, Slice by Slice
Updated: 23 hours ago
When Crosshole Sonic Logging (CSL) identifies a potential anomaly in a concrete pile, the next question is critical: Where is the anomaly, how much of the pile may be affected, and how severe is it?
Traditional CSL profiles help identify changes in ultrasonic signal behavior with depth. However, interpreting multiple profiles individually can make it difficult to understand the overall condition of the pile, particularly for large-diameter foundations with numerous access tubes.
CHUM 2D tomography helps bridge this gap by transforming CSL measurements into visual cross-sectional slices, allowing engineers to examine potential concrete flaws at specific depths and assess their possible extent.
What Is 2D Tomography in CSL Testing?
Crosshole Sonic Logging measures ultrasonic signals traveling between access tubes installed inside a concrete pile. Changes in First Arrival Time (FAT) and Relative Energy (RE) can indicate areas that require further investigation.
Each CSL profile represents a measurement path between a pair of tubes. When several paths show abnormal behavior at a similar depth, 2D tomography combines the available information into a cross-sectional view of the pile.
Instead of examining signal changes alone, engineers can inspect a horizontal slice showing how the concrete's estimated condition varies across the pile at that depth.
With CHUM Crosshole Sonic Logging, 2D tomography is available during testing, helping engineers visualize potential anomalies as data is collected.
Scan the Pile and Inspect Each Slice in Real Time
One of the practical advantages of CHUM 2D tomography is the ability to follow the pile's depth and examine the corresponding cross-sectional slices.
As testing progresses, the engineer can review the available tomography to understand how the estimated concrete condition changes along the pile.
Each slice provides a view of a particular depth, helping answer three important questions:
Where is the potential flaw? Identify the depth at which abnormal signal behavior appears.
Where within the cross-section is it located? Examine the spatial distribution and location of the potentially affected area.
How much of the cross-section may be affected? Review the estimated effective concrete area and determine whether further investigation is warranted.
Areas with abnormal ultrasonic behavior may appear as regions of reduced estimated concrete quality or potential voids in the tomography display. These indications should be interpreted alongside the original CSL measurements (i.e., severity graph based on DFI criteria) and other relevant evidence; a tomography image alone does not conclusively establish the physical nature of a defect.
The Effective Area Graph: One View of the Overall Situation
For complex piles, the challenge is not simply finding an abnormal reading. It is understanding how the different CSL profiles relate to one another, and what they collectively suggest about the pile.
This is where CHUM's effective area graph becomes particularly useful.
The effective area graph is a severity-oriented view that integrates information from the CSL profiles (containing FAT and RE* information) to help assess the overall condition of the pile at different depths. Rather than requiring the engineer to interpret each profile in isolation, it provides a consolidated indication of where the pile may warrant closer examination.
* FAT - First Arrival Time, RE - Relative Energy. Both pieces of information are gathered by the CHUM sensors.
Analysis tool | What it helps the engineer understand |
Effective area graph | The estimated effective concrete area and the overall severity indication at each depth |
2D tomography slice | The spatial distribution of potentially affected concrete within the cross-section |
Individual CSL profile | The specific tube-pair measurements and signal changes associated with a potential anomaly, presenting FAT and RE. |
DFI-based severity graph | The classification of abnormal signal behavior using the selected DFI-based criteria combining FAT and RE values |
The Effective Area is especially valuable for large piles exceeding 1 meter in diameter, where more than 10 CSL profiles may need to be reviewed to understand the overall condition.
In these situations, the Effective Area graph helps direct attention to depths of interest before the engineer examines the individual measurements in greater detail.
From Potential Anomaly to a More Informed Assessment
CHUM's tomography and severity views can be used together in a practical interpretation workflow.
Step 1: Locate the depth of interest. Review the effective area graph to identify depths where the estimated condition changes or a significant anomaly is indicated.
Step 2: Inspect the corresponding 2D slice. Examine the tomography at that depth to understand the approximate location and distribution of the potentially affected area.
Step 3: Save the relevant slice for reporting. Select the appropriate cross-sectional image to document the indication and support communication with the project team.
Step 4: Review the relevant CSL profile. Return to the tube-pair profile corresponding to the anomaly and examine the associated FAT and RE behavior.
Step 5: Cross-check the DFI-based severity indication. Compare the original measurements with the applicable severity criteria to help evaluate the significance of the anomaly.
This approach connects the visual evidence with the underlying measurements, making the findings easier to review, document, and discuss with other engineering professionals.
Importantly, the effective area graph, tomography slice, and DFI-based severity indication provide complementary information. They should be interpreted together rather than treated as interchangeable measurements.
Why Is This Particularly Important for Large-Diameter Piles?
As pile diameter and the number of access tubes increase, the number of tube-pair profiles can grow substantially.
For example, a pile with eight access tubes can produce 28 unique tube-pair profiles. Reviewing all of them individually can make it harder to identify the relationships between abnormalities at the same depth.
CHUM's effective area graph provides an integrated overview, while 2D tomography helps visualize the cross-section at selected depths. Engineers can then return to the relevant CSL profiles to investigate specific indications.
The result is a more organized way to move from a large dataset to a focused engineering assessment.
For further background, read Piletest's guide to CSL tomography and pile defect visualization.
What About 3D Tomography (3DT)?
While 2D tomography provides cross-sectional images at selected depths, 3DT extends the analysis by combining information through the pile's volume to create a three-dimensional representation.
This can provide additional spatial context for complex anomalies. However, the central advantage of CHUM 2D Tomography remains its practical ability to visualize individual pile slices and connect them with the effective area graph and the underlying CSL measurements, all in real time. You can actually scan the depth and see the 2D Tomography slice change in real time, kind of like doctors do in a CT scan. In comparison, 3DT requires offline computational software to generate the 3DT view.
Explore CHUM tomography capabilities for more information.
Frequently Asked Questions
1. What does 2D Tomography (2DT) show in CSL testing?
It provides a cross-sectional visualization of the pile at a particular depth, helping engineers assess the approximate location and distribution of areas associated with abnormal ultrasonic measurements.
2. What is the Effective Area graph in CHUM?
The effective area graph presents an integrated, depth-based assessment of the estimated effective concrete area and associated severity indications, helping engineers review the overall situation across multiple CSL profiles at a specific depth.
3. Why is 2DT useful for large piles?
Large piles may have many access tubes and numerous tube-pair profiles. The effective area graph helps identify depths requiring attention, while 2D slices help visualize the potential anomaly and guide more focused profile review.
4. Does a tomography image confirm a concrete defect?
No. Tomography helps visualize potential anomalies inferred from CSL measurements. Engineers must review the underlying profiles, severity indications, project information, ground profile, and any additional investigation required before determining the significance of a suspected flaw.
Conclusion: Turn CSL Measurements into a Clearer Picture
Identifying a potential anomaly is only the beginning of pile integrity assessment. Engineers also need to understand where it occurs, how it extends across the pile, and what the measurements suggest about its severity.
CHUM 2D Tomography supports this process by combining cross-sectional visualization with the effective area graph and individual CSL profiles. By identifying a depth of interest, examining the corresponding slice, and cross-checking the relevant measurements against DFI-based severity criteria, engineers can develop a more informed assessment and communicate their findings more clearly.
With CHUM, engineers can move from reviewing individual CSL profiles to understanding the pile slice by slice.
Learn more about CHUM CSL testing and tomography.
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