Table of contents


CHUM

Cross Hole Ultrasonic Monitor
User Manual



All rights reserved Piletest.com™

1. Installation

Windows XP/WIN7/WIN8.1/WIN10: You will need system administrator rights to complete the setup. Once completed, the software is ready for use by all users. (Consult your IT personnel if not sure)

Notes: Before using CHUM, ensure that the battery is fully charged (after 1-2 hours of charging time), or until the Orange LED of the CHUM main unit turns off. Use only the charger provided with the CHUM system.

 

Minimal requirements:

  • Pentium III 500 MHz

  • Windows XP

Recommended

  • For intensive field work: 900 MHz, Tablet PC or touch-screen with outdoor visibility

Software Setup

  • Insert the provided CHUM CD your received, into the CD drive of your computer. The CHUM setup will start automatically.

  • Follow the setup defaults to install CHUM (Usually <1 minute).

  • In case the setup does not start automatically, double click the SETUP icon on the CD root folder.

  • CHUM software can be found here:  [Start]>[Programs]>[Pile Testing ]  or   [Start]>[All Apps]>[Pile Testing ]

Hardware drivers setup

You only need to install the hardware drivers on the computer that is being used for testing, but you can also install it on your office PC and connect the CHUM system to that PC as well.

  • Plug the CHUM USB connector into the computer

  • The green LED on the CHUM panel will blink ten times and then stay on

  • The "found new hardware" pop-up notification appears and the "found new hardware" wizard should open automatically

  • Follow the wizard's instructions, and insert the CHUM CD to the CD drive of your computer and press [next]

  • The Wizard will start copying the driver files from the CD

  • If you are using a Windows XP system, the system may display a security warning -- you can safely ignore this warning and press [Continue Anyway] -- the CHUM driver is fully tested and is Digitally Signed by Microsoft, and does not impair your system's stability

  • After the files are copied, close the wizard by clicking [Finish].

 


2. FAMILIARIZING YOURSELF WITH THE CHUM SYSTEM

The CHUM system consists of the following components:

  • CHUM instrument

  • A pair of pulleys with depth meters

  • A depth cable (I cable or Y cable)

  • 2 Ultrasonic emitters/receivers on cable reels

  • Computer (Not provided)

  • Battery charger

  • 12 V DC car battery adapter (Optional)


 

The CHUM instrument has a rugged housing and contains the following:

  • Battery: The CHUM uses a high-capacity 11.1V 4.4 Ah Lithium battery, that enables up to two days of normal use. The battery does not need to be discharged periodically, hardly loses any power during storage, and does not require maintenance.

  • An AC power adapter that can be used to power the CHUM while charging the battery, just like a notebook computer (a car-lighter socket DC charger is optional).

  • A microcontroller with data conditioning, processing and acquisition circuits.

  • CHUM connector panel. The respective connectors and controls on this panel are (from top to bottom):

    1. Power (from either AC or car battery source)

    2. USB (Note: when you connect the the USB cable to a computer, the system is powered on)

    3. Green LED
      • ON: Indicates that all internal power supplies are OK

      • Start: Blinks 10 times at 2 Hz, when the unit is started, indicating that the firmware is OK
        Note: Ensure that the USB cable is plugged into a computer that is switched on

      • Suspend: - A quick blink every 3 seconds approximately, when the system enters suspend mode (after 30 seconds of inactivity). The 'Suspend' mode saves battery life, and allows the system to resume operation automatically when needed

      • In Operation: A short blink for each transmitted pulse

    4. Orange LED
      • ON: Indicates that the charging circuit is OK

      • Battery Empty: The LED blinks to indicate that the battery is empty/intermittent charging

      • Charge: The LED lights bright to indicate continuous charging

      • Battery Full: The LED dims when battery is fully charged

    5. Emitter socket

    6. Receiver socket

    7. Depth meter socket

  • Hardware features

    1. Automatic gain control: CHUM has 8 gain levels, from X1 (5 V), to X256 (~20 mV). The gain is adjusted automatically to acquire the best signal quality, with the maximal number of bits without saturating the A/D acquisition card

    2. Excellent signal to noise ratio: For best pile analysis at maximal distance (tested profile length)

    3. Low power consumption: For maximum operational time in the field

    4. Automatic Suspend mode: To increase battery operation time

 

Two pulleys: Both contain a bi-directional rotary encoder. The encoder generates an exact number of pulses per revolution

Note: Depth encoders should be calibrated.

 

Two Transducers and Cables: The dual-purpose transducers contain piezo-electric ceramic elements that generate signals of 50 kHz (nominal frequency). Each transducer can function as either emitter or receiver, depending on the socket it is plugged into.

These transducers are attached to polyurethane coated cables wound on a drum. The cables may be ordered in lengths of  50 or 100 or 150 meters. Custom lengths are available upon request.

 


3. GETTING STARTED

  • Power on the computer, and wait for the Windows main screen to appear

  • Ensure that the Emitter, Receiver and Depth meter are connected to the CHUM instrument panel

  • Plug the USB cable into the computer

  • Start the CHUM software. The CHUM main screen appears





  • From the top menu bar, click [FILE] and then [NEW PROJECT] (or the "Start a new project" link, or the button)

  • Choose a name, or number, for the new project. You can use the name "TEST" for this project

  • Optionally enter any suitable text on the TITLE and SUBTITLE lines, which best describes the project

  • Before testing your first pile, you must calibrate the depth meter See Depth Calibration

 

3.1.  Testing

  • On the CHUM Main Screen, click the large plus [+] button to activate the pile screen



 

  • The test wizard has several stages:

To move between the test phases, click the [Next] and [Back] buttons. If a button is grayed out, CHUM needs more information to move ahead, or does not expect the button to be pressed at this stage

The pile name/number and tested profile is displayed on the window caption.



[More ] Opens advanced pile options



Edit tube distances -- see Define tube distances

Cut all -- Cuts the all profiles top (tube-stick-up) so that profiles will have the same length

Consult with piletest.com -- Send this for Consulting with Piletest.com

3DT -- Perform three-dimensional tomography (Optional CHUM component)

Report  prints a report from this pile only. Convenient for on-site printing. To produce a detailed report, see Reporting

Duplicate - Creates a pile similar to the current one



3.2.  Pile details and geometry

In the CHUM Main Screen (see screenshot), enter information about the whole pile (not just specific profile): the pile name, sub-site, and diameter, access tube layout and level. You may also enter pile specific notes (e.g. "pile top needs trimming").

The pile (or element) name may be up to 20 characters long and may contain any character

Sub-sites are a convenient way of breaking up a big project into smaller units (Read more…).

Select an existing sub-site, or create a new one by pressing the [New…] button.




[Save] exits the wizard and saves all changes and all details. Changes are also saved automatically after each log is taken.

[Save compact] Only arrival time and energy are recorded in the files. Files are tiny but no FAT picking can be done after they are saved, and no waterfall presentation can be done (The ASTM standard may require it).

The drop-down menu above the pile scheme enables you to choose one of many available tube layouts you may be going to test. You may choose among:

  • A pile with up to 4 access tubes named N, S, E and W

  • A pile with 2 to 15 access tubes numbered 1...N clockwise (1 is northernmost by convention)

  • A straight diaphragm wall element  (barrette)

  • A pile with a single access tube (AKA single hole test)

  • Additional tube layouts may be supplier (free) from Piletest

After you have selected the scheme, you can rotate using the rotate_left and rotate_right icons to the correct azimuth. This only affects the reporting and has no other meaning.

There are several ways to specify the profiles you want to test:

Fastest: Click the [ALL] icon to define all combinations. After you have finished testing you can use the [Clear Untested] button to remove the redundant combinations only.

Coolest: Using the stylus, draw a line between the tubes (You can specify more than one profile in one broken line). To specify single-hole tests, draw a circle around one of the tubes. This input is very convenient when using a stylus (as opposed to a mouse).

Advanced: Click the small [+] button below the profiles list to show the new profile screen.





You may enter any name, but only names made of two tube letters/numbers will appear in the scheme graphics. Other profile names will be reported, but cannot be assigned to tubes.

Note: the profile letters/numbers have a significant meaning when performing Tomography


Tested cross-profiles are painted with a thick, red line, this way you can always see which profiles are still untested.

To delete a profile, either:

  • Select it from the list and press [X]

  • Re-draw over it

  • Press [Clear untested] (if the profile was not yet tested)

If the profile was already tested, you must confirm the deletion



TIP: Under normal conditions, piles should be tested at a concrete age of around seven days. Testing should not be performed earlier than 2 days after concrete placement, as the curing process may be slower in certain areas.  Also, tube de-bonding (separation of tube from concrete, in plastic tubes) becomes more likely as time after concrete placement increases. For this reason, interpreting the data may become much more difficult if testing is performed, about  two weeks or more, after concrete placement.

TIP: For CSL testing, the pile to be tested has at least two embedded test tubes. The diameter of the tubes should exceed the transducer diameter by at least 10 mm, and they should be checked for clearance throughout their length. The tubes should have been filled with clean water either prior to or soon after concrete placement.

  • Place the pulleys on top of two of these tubes, and lower both emitter and receiver all the way to the bottom

  • Click on the profile to be tested (or highlight it and press [Next]) and the leveling screen will appear.
    TIP: If you press  [Next] before lowering the cables, you can then monitor the approximate tube length

3.3.   Define tube distances

The ASTM standard requires all tube distances to be reported. For tomography, tube distances MUST be entered.

To enter tube distances, select "tube distances: [EDIT]" and enter the distance for each tube pair.

When enough tube pairs have been defined, you may use [Auto complete] to automatically calculate the position of all the other tube pairs. This is useful for a large number of tubes.

For example, in a four-tube pile, 5 of the 6 combinations must be entered to calculate the sixth, but for a 10-tube pile, only 18 of the 45 possible combinations must be entered, and the rest can be calculated.

TIP: it is advisable to add some redundant measurements for cross-check. The algorithm will report the maximal error in this case.



 

 

3.4.  Leveling



Testing is done by pulling from bottom to top. Before you start pulling, you should make sure that both transducers are at the initial test position. Both transducers should be at  the same level, and as close to  the bottom of the test tubes as possible.

On this screen you can see the following items, which are all designed to help you bring the transducers to the initial test position.

On the left there is, a black strip that scrolls from the bottom to the top of the screen, showing the relative signal strength (thickness of the strip) and the First Arrival Time (FAT).

A thin line on the left also represents the FAT, but is heavily filtered and reacts more slowly to changes. The combination of the fast and slow moving indicators gives a clear sense of the direction of change.

A pop-up window appears on the lower right hand side, and displays a virtual oscilloscope that shows signal shape, strength (gain), and automatically picked FAT (triangle).

TIP: Double-clicking the oscilloscope window maximizes and restores it.  The window can also be moved and repositioned

A distance meter, giving the approximate distance between the transducers (in feet or meters).

If you intend to run tomography on this profile, check the [ ] Do Tomography. You must enter the tube distance for tomography.

Select the sample duration (500, 1000, 1500 or 2000 µs) which best fits the current profile distance.

If the FAT is not picked up correctly, click the [FAT options] button to show the FAT options page

Click the [Options] button to open the options page and change general options such as sample spacing, unit system, and profile compression)

If you are lowering the transducers while in this screen, depth from top (H) is displayed, click on the depth label to reset it.

Using the controls

While in the leveling screen, move any of the transducers up or down, in order to bring them to the same level. This is accomplished by observing the following indicators:

  • The black strip is closest to the left hand side of the screen and also the widest

  • The signal on the Scope window is strongest (low gain)

  • Distance on the meter is minimal and should be roughly equal to the measured distance between the tubes

TIP: Always level the transducers in a clean concrete zone. If the pile has a soft bottom, perform the leveling a few feet (~1m) above the bottom, then lower both cables carefully together to the bottom before continuing.

When you have satisfied the leveling criteria, click [Next], and the pulling prompt will appear.

 

3.5 Start Pulling

Do not click the [Next] button yet, CHUM will move automatically to the next test phase when you start pulling

TIP: Select the "use sounds and voices" option if you want the "pull" command announced using the default system voice

At this stage start pulling both cables together, hand after hand, as smoothly as possible until both transducers reach the top. The rate of pulling should be no more than 40 samples per second, if the vertical spacing is set to 5cm, this will be up to 2.0 m/s (which is very fast)





 

3.6. Logging

The data collection screen is very similar to the leveling screen except for a vertical depth axis along the signal strip on the left side of the screen, as well as no distance (between transducers) presented in the meter area.

The plot will scroll upward as the cables are pulled up.  The transducers can be raised and lowered in suspect areas/zones of the concrete to increase the number of data points taken.  The plot of the signal strength will scroll in synchronization with the cables as they are pulled up and down.

Suspect zones will be noticeable when the strip is thinner and/or when the left edge of the strip is further away from the depth axis (increase in FAT).   When you have finished pulling, click the [Next] button, the profile will be automatically saved, and the Analysis screen displayed.

 

When tomography is performed, this screen has some additional controls, and pulling is performed in a special way. See Tomography





 

 

3.7.  Analysis

At this stage, the results of the test are displayed on the screen as shown below. There a few options for this display, and the "Lines Plot" mode is the most common. In this form, the first arrival time (FAT) and the attenuation registered at the receiver are shown as a function of depth. A local increase of FAT or attenuation may indicate an anomaly.



 

Controls description from top to bottom

The profile name can be edited

[Presentation] Change the presentation mode

[ Filter=n ] FAT, Energy, Attenuation and Wave Speed filtering (0 = no filter, 5=heavy filtering) (Read about filters)

[] Remove the top or bottom of the profile log

  • Erasing the top of the log is sometimes used if the access tube stick-up much higher than the pile top surface

  • Erasing the log bottom may be used if the cables were pulled with too much slack, but should usually be avoided.

[FAT] start the FAT utility form to analyze the data more thoroughly,

[Clear] Delete the data you just collected (Warning: You will have to redo the test!)

[ More  ] show advanced options menu:

  • Save as CSV (Excel data format) - Compact or detailed
    The profile is saved in CSV format (Plain text format with comma delimiter) and Excel (or any other associated application) is launched
    Detailed file contains full waveform information. Read about using this feature

  • Cut to length - enter a length to which to cut from the top of this pile. Useful when the access tubes are sticking out of the concrete in different heights.

  • Wave Speed Calculator -- A simple test method for accurately measuring the wave speed read more…

Profile specific notes may be entered (e.g. "Flaw at 3.5m")

Vertical zoom in and out

Horizontal zoom in/out


4.  COMMON TASKS

4.1.  Starting a new project

  1. From the main menu, select [File]-[New project]

  2. Verify that the "Home folder" points to the correct path, or click [Home Folder] to change it

  3. Enter the project's name or number and click [OK]

CHUM will create a new folder under the home folder, and will create the file PISA.PROJECT.

TIP: Use project numbers, rather than names. This makes finding and managing many projects simpler

4.2.  Opening an existing project

If the file was created or opened recently, it will be listed in the "most recently used" list under the "file" menu

  1. From the main menu, select [File]-[Open project]

  2. Verify that the "Home folder" points to the correct path, or click [Home Folder] to change it

  3. Select the project and click [OK]

4.3.  Saving a project

There is no option or need to save a project, all changes are saved automatically

4.4.  Transferring project files to another computer

When you visit the site for the first (or only) time, connect the computers, and copy the whole project folder to the target (This can usually be done by dragging the project's folder).

During future visits to the site, sort the source folder by date, and only copy the latest added files to the target computer.

4.5.  Sending files over e-mail

If the files are small, you can send them as an e-mail attachment. We recommend you that you compress the files using WinZip or a similar program. Note: Many e-mail providers do not accept large attachments.

The simplest and best way to send a file to Piletest is using the Consulting Wizard

4.6.  Changing the location where projects are saved

From the 'Open', or 'New Project' screens, select [Home folder] , then click [Modify] and select the folder where you want your projects to be stored and where the "Open Project" command looks for existing projects.

 

See also: Projects, Sub-sites and files


5. Options

The Options Screen [Tools]-[Options] displays two tabs "Logger" and "General"

5.1.  Logger options



Vertical spacing
The spacing between samples. A typical general-purpose value is 5 cm (2 inches). A smaller spacing will give a finer coverage of the cross profile but will produce larger files and limit the pulling velocity to 40 samples per second.
Default Filter
Defines the initial filter value for new piles. The recommended value is 1.
Wave speed calculation
Select simple calculations, or compensate for the time the wave travels in water
FAT options
Opens the FAT options dialog box
Signal classification
Opens the Signal Classification dialog box where you can assign one of three categories to a pulse, based on wave speed and attenuation changes.



 

5.2.  General options



Units: Select if the system is using Metric (m) or English units (Feet and Inches)

Software keyboard: Check this option to have show an automatic screen keyboard pop-up when an alpha-numeric input is required. This option is only useful for keyboard-less computers.

Unit Code: Changes the first character prefix of newly generated pile files (eg. the 'A' in  A0002782.9_2.PILE). If you have more than one CHUM unit, assign a unique code (for example 'A', 'B'...) each unit to avoid accidentally using the same name, for example if the same project is being tested by several CHUM units.

(See also Projects, Sub-sites and files)

Use Sounds and Voices: Disable or enable voice instructions. CHUM uses the default Windows voice, accessible via [Control panel]-[Speech]-[Text to speech]. You can change the voice, and it's speed there.

5.3.  Depth Calibration

CHUM uses a digital rotary encoder that generates an exact number of pulses per pulley rotation.

Depth calibration determines the number of pulses per length pulled. This number is stored internally in the test computer.

You should perform depth calibration:

  • Once before starting to test your first pile

  • When starting to use a new computer

  • Once a year

  • Whenever there is a doubt regarding the depth reading

 

To perform depth calibration, simply select [Tools]-[Depth calibration] and follow the wizard

Verify repeatability by re-running the wizard.


For your reference, here is an extract from ASTM 6760-16 (Standard Test Method for Integrity Testing of Deep Foundations by Ultrasonic Crosshole Testing)

6.3.6 Transducer Depth-Measuring Device ...
The depth-measuring device shall be accurate to within 1 % of the access duct length, or 0.25 m, whichever is larger


 

5.4.  Signal classification options

From the Options Logger tab, select signal classification, to open this page.

Signal classifications are used to color-code a pulse based on wave speed and attenuation changes, and for real-time and fuzzy-logic tomography, and to control the values that classify a pulse into one of three color-marked categories. The categories are "good", "questionable" and "poor", but are actually only two logic criteria options, as depicted below:





You can control the area of the three zones by clicking and moving the black bars, changing the logic operator ("AND" / "OR"), or by ignoring attenuation altogether, by un-checking the Attenuation Increase checkbox, and using only wave speeds.

 

5.5.  FAT picking options

The FAT (First Arrival Time) picking options can be accessed either from the Main Menu (Tools-Options), from the Leveling screen, or from the FAT utility.

Four options for picking the FAT are available, and each method uses different settings:

Automatic:

A Piletest.com proprietary algorithm -- no additional settings are needed.

Click here for more details about the algorithm.

PLEASE USE THIS ALGORITHM - ALL OTHERS ARE FOR ADVANCED/BACKWARDS COMPATIBILITY REASONS

Dynamic threshold:

A Piletest.com algorithm which uses a threshold level based on the pulse amplitude

Minimum Time:  You can set this limit so that the signal picking routine will not look for a shorter FAT.  For example, a delay of 200 µSec will cause all FATs to be 200 µsec or higher. 

Note: Set the delay time sufficiently lower than the minimum wave travel time between the tubes for normal quality concrete.  For example: 250 µsec for tubes 1m apart and a typical 4000m/sec concrete wave speed (t=L/C).
The minimum time is represented as the horizontal position of a small red triangle.

Threshold Ratio:

This is a limit that references the pulse amplitude. In general, a higher ratio means that the program will pick FATs sooner, but is also more sensitive to noise. The signal is typically strongest in the earlier portion of the record after the first few peaks.  For example a ratio of 10 means that the first occurrence of a signal amplitude 1/10 of the maximum is defined as the FAT. A typical value is around 10 to 20, but under poor test conditions, lower values may be required.

Minimum Level: 

This is an absolute limit that does not depend on the background noise level.  If the threshold is lower than for example 10 mV, then any value lower than that before the first 10mv peak will be ignored. This option is rarely needed and may usually be kept as 0. This is only useful in the case of very weak signals and is mainly kept for backward compatibility with previous versions of CHUM.

Fixed threshold:

Old-Fashioned picking -- the threshold value is fixed.

STA/LTA (Short Term Average / Long Term Average)

This algorithm is used in earthquake studies to determine the exact time the earthquake began.

Description:

A window of defined size is moved along the time axis and measures the average of samples in this window.
Another window of larger size follows the first one
FAT is defined as the earliest point where the ratio between the two averages exceeds a user-defined ratio
Typical values are:
Window size:     6
Ratio:             1.6

ref: Caltech Earthquake Detection and Recording (CEDAR) system [Johnson, 1979].

For more details-- search for"STA/LTA" on the Internet.

 

5.6.  Presentation

The presentation window is accessible from the Analysis screen, or from the Report screen.





You can select a presentation mode from the following currently available methods:

  • Line Plot, with a combination of the following curves

    • FAT: [milliseconds]

    • FAT Flag: A colored flag at FAT+20%

    • Relative energy [unit-less] or Attenuation [dB] - but not both

    • Apparent Wave speed: [m/s of feet/s]

    • Waterfall Watermark: Creates washed-out Waterfall background
      (Note: the ASTM standard requires that waterfall presentation is added if any filtering is used)

    • PSD - Report according to Chinese standard (NOT RECOMMENDED)

  • Waterfall:

    • Classic:
      Ignores the amplitude of the signal and draws two-color, high contrast diagram
      Low-energy zones will appear the same as high-energy zones as long as the FAT is stable

    • Modern:
      The energy of the signal effects the brightness of the diagram,
      low-energy zones will appear lighter

  • Fuzzy logic tomography (*)
  • Parametric tomography (*)
    * - Only if the data was collected with diagonal readings using two depth encoders (Tomography)
  • Color: Select the color for the presentation. When selecting a color, consider your final report capabilities:

    • Does your printer print in color or in gray scale

    • Is the report going to be faxed -- most faxes are black and white only.

 

 


6. Reporting

CHUM reporting options can be set using the following three tab sheets

Report contents

Filtering

Layout options

As soon as you click [OK] to create a report, a report file called report1.rtf is generated and opened by the default program on your computer associated with the RTF document file type. You can then for example edit the report, merge it with other documents, or e-mail it.

See also: [Page setup dialog] [Report style]




Contents Tab

  • Check the [X] Project Totals checkbox to produce a table specifying the number of piles and profiles, and the total length of piles and profiles for each sub-site.

  • Check the [X] Project Summary checkbox to produce a table displaying the measured length of each profile, and related comments recorded with it.

  • [ ] Site Plan is not yet implemented.

  • Check the [X] Detailed report checkbox to produce a table for each pile including graphs and all recorded details. When you select this option, you can also fill in additional options in the [Options] tab.




Filter tab

  • You may select to report all piles, only piles from the past month, or those from the last site visit.

  • If a pile is selected in the main page, a forth option is displayed here that allows you to report only the selected pile

  • Check [X] Include non-tested piles to include piles which have no recorded logs, in the final report.


Options tab

This tab is only available if the [X] Detailed report checkbox is checked

"Vertical scale" can be set to a specific value, or set to [Automatic] to best fit the page height. If you select "Automatic" the scale is calculated to fit the longest profile in the report to one column. Larger scales may cause some profiles to be printed over several columns. Number of columns (one graph per column) can be set. We recommend that you switch to landscape print orientation when using more than 3 or 4 columns.

You can select Presentation modec for the whole report.

The "Distortion" option is only enabled for a tomography report, and will improve the visual presentation of piles by distorting their width in favor of height.

TIP: You cannot mix different presentation modes, and scales, etc in one report, however, you can do this by by cutting and pasting two separate reports into one document.



6.1.  Controlling the report style

From the main menu, select [Tools] -- [Style] to show the style screen





Select an item from the list on the left hand side and change its appearance using the controls on the right side.

[x] Use: Include or exclude items from your report.

[Default]: Restore the style for all items to the factory settings

[Close]: Done. Try your new style by producing a report

TIP: You may select several items from the list on the left by pressing the [shift] or [control] keys while clicking items. This way you can change the appearance of several items at once.

TIP: underscores (_) are converted to spaces. Append a few underscores to your prompts to ensure proper tabulation of titles labels and values.

TIP: Avoid using too many font styles in your report; a good-looking report usually uses two to three font styles at the most.



6.2.  Page setup

From the main menu, select [File] -- [Page Setup] to show the following screen





The name of your currently selected default printer is displayed on top. Set the margins you would like each side of the report page (mm).


7. Advanced options

7.1.  Enable/Disable features

From the main menu, select [Tools]-[Enable/Disable features] to enable/disable CHUM features.





By default, all features in the checklist are enabled, but you may select to disable some of the features for the following reasons:

  • To simplify the use of CHUM by hiding features you never use

  • To limit the level of control you give the field technician

  • To prevent possible operation errors in the field

  • To encourage your team to adopt a specific workflow

 

You can use a password to prevent unauthorized changes to the features selection (see Note). . After you select a (non-empty) password, you will need to re-enter it every time you start the feature manager.

Tip: If you forgot your password - look it up in the file CHUM.INI, stored under your user's "application data" folder

Note: There is no way to protect this password completely from malicious users.

Tip: To remove the password, delete it - set it to empty.

7.2.  First Arrival Time (FAT) Picking

To access the First Arrival Time (FAT) options, click [FAT] from the Analysis screen.

The FAT screen has two panes. The Left pane displays the FAT vs. depth plot, and the Right pane displays the actual signals.

Note: the vertical position is referenced from the bottom of the tubes rather than the top because the data is collected from the bottom up.  When you exit the FAT signal picking screen, the software re-plots the depth from the top.

The vertical separator between the panes can be dragged right or left.

 The horizontal separator between the signals on the right pane can be dragged up and down.





In some cases, the CHUM system automated FAT signal picking routine does not select the FAT correctly and you may need to adjust it manually.. There are two ways to select the FAT signals -- manual and automatic.

Manually:   Click on the signal trace on the right hand side of the screen.  The highlighted signal is shaded,  and a small circle appears on the left side highlighting where the particular signal is in the plot.  Remember that in this screen, vertical position is from the bottom. You can also pick the FAT in the signal by moving the mouse to the desired point then clicking the left mouse button.  The FAT will be delineated by the two diagonals intersecting at the FAT on the horizontal (time) axis.  The time of the FAT (in Microseconds) will be shown in the data area. The highlighted circle in the depth plot on the left will move accordingly depending on where you selected the FAT on the signal plot on the right.  Additional data such the depth (in meters/inches) and scale are also displayed.

Automatically:   This option is very powerful as it allows you to change the FAT for all applicable signals along the pile.   Click [Calc] to enter the automatic FAT picking menu.

Once you have selected the values, click [Close].  The program will then recalculate all of the FATs for the entire profile.  You will see a change in the plot of the individual FATs.  If you agree with the FATs, then click [Accept].  Click [Cancel] to cancel any changes you have made.

The [More] button  provides the following additional options:

  • Change the view of the signals option allows you to view the raw and/or the filtered data, and/or the signal envelope

  • Delete/Undelete any signals that you have highlighted on the right.

  • Restore all previously deleted signals (only if you are still in theFAT signal picking screen).

  • Copy the highlighted pulse shape to the windows clipboard, you may paste it into your report

  • Set to Infinite when no wave arrival is visible


7.3.  Consulting with Piletest.com

From the Pile details page, select [More▼] and [Consult]

Piletest.com offers limited consulting services in order to:

  • Help novice testers with analysis

  • Help advanced users with difficult cases

  • Collect interesting test cases

 

The "Consulting Wizard" opens





The consulting wizard lets you select the profiles of the pile that will be compressed. The trade-off is yours:

  • Compressed profiles contain no waveform data and no FAT picking can be done, but the profiles are very small in size and can be easily transferred

  • Non-Compressed profiles contain full waveform data and Piletest.com can observe and modify the FAT pickings. But such profiles are much larger and take much longer to transfer. If the whole file size is below 4Mb, and you do not have any bandwidth limitations, send the file uncompressed.

The wizard provides an estimate of the file size and the expected transfer time. Files are first transferred to Piletest.com's cloud storage (by FTP). Then your default e-mail editor opens and creates a new message to consult@piletest.com - please provide clear information about the consulting you require.

 

7.4.  Data Sources



CHUM can accept data from various sources. This allows you to use the same software in the field and on the desktop computer, and to train people or demonstrate the software without the hardware.

From the main menu, select [tools] -- [Data source] (or the play button ) to display the Data Source screen.



 

 

 

By default, CHUM can use the followign data sources:

Name Description
USB Connects to the CHUM hardware via a USB drive, in order to test piles. Select this data source if you are working in the field.
Demo Uses simulated pulses with one simple defect
Replay Replays a stored profile from any pile (Advanced)

The currently selected data source is displayed in the window title.

To change a data source - select one from the drop-down list.

To test the currently connected data source, press [Test ▶], the dialog will expand to show the data source diagnostics. In this mode, CHUM triggers the emitter at 10 Hz and displays the following parameters:

  • The data source description

  • Tomography supported / not supported

  • Hardware status and error codes

  • Raw depth encoder counter readings for both counters (ignore the second reading if you only have one depth encoder)

  • Sample rate (Should be 500 KHz)

  • Battery voltage, and voltage indicator

  • The automatic gain picked for the displayed signal

  • Attenuation for the received pulses

Press the [Stop ■] button to exit the self-diagnostics mode

7.5.  Exporting data

You may export profiles stored in the native CHUM internal format to a CSV (Comma delimited) format that can be used in most spreadsheet software programs (such as Microsoft Excel).

To generate a CSV file, start CHUM, select the pile and profile you want to export, click [More] and select either a detailed, or a compact file format

  • Compact CSV contains the profile details, and the individual pulses FAT and Energy

  • Detailed CSV contains, in addition to the compact data, the shape of each pulse.

CHUM now asks you for a filename and location to store the CSV file, the default file name is <pilename>.<profile name>.CSV. Ffor example if you save profile NS of pile 3-1, the default filename would be 3-1.NS.CSV

 

As soon as you save the file, CHUM will try to launch the associated application (such as Excel). If the application does start automatically start your spreadsheet application manually and open the saved CSV file.

Note: If you get a "file not loaded completely" message, simple ignore it.


Description of the Cells displayed in the spreadsheet

  • A2..F2    Project name, Pile name, Profile name, Filter, tubes distance (cm), profile notes

  • Row 3 - Samples headings:

Column

Title

Description

Units

A

D1

Master (or single) depth encoder readings

cm from bottom

B

D2   

Secondary depth encoder readings (identical to D1 if no tomography was done)

cm from bottom

C

T0   

FAT

microseconds

D

Energy

Total energy of the pulse

V•Sec

E

SampleRate

A/D sampling rate (samples / second)

Hz

F

Gain

AGC (Automatic Gain Control) value *

-

G

Number of samples

how many samples are taken for one pulse

Samples

H...

Value(n)

Pulse shape data, 12-bit value (-2048..+2047)*

Bits

*    To convert the pulse value to volts, use the following formula

Volts = Value * 5.0 / (2048 * gain)


Generating a curves chart

(Only for Microsoft Excel )

  • select B4..D4

  • Press Ctrl+Shift+Down to select 3 columns of data

  • Press the chart wizard icon

  • Select X-Y scatter without markers

  • (Optionally) swap X and Y axis and add titles and labels

  • press [Finish]


Extracting a single pulse shape chart

(Only for Microsoft Excel )

Note: The option is only available if you save detailed CSV file.

  • Select Hn (where n stands any row, for example H4)

  • Press Ctrl+Shift+Right to select the whole row

  • Press the chart wizard icon

  • Select X-Y scatter without markers

  • (Optional) specify titles and labels

  • Click [Finish]

7.6.  Wave Speed Calculator

The wave speed calculator uses the standard test wizard. Testing is performed as follows:

  • Lower both transducers together to exactly the same level. This level should be in the middle of the pile, at the bottom of a 4-5 m (10-15') zone of uniform concrete. This is the tested sample.

  • Define a profile in the pile, and press [Next] to start testing it, just like in a standard test

  • Set sample size to maximal (2000 us)

  • Leave the passive transducer stationary, and raise only the transducer connected to the depth pulley. Watch the scope window and keep pulling until the signal becomes too weak and FAT picking is no longer possible

  • Press [Next] to show the profile, which should be similar to the following graph:


  • Use the [] (scissors) icon to trim the top or bottom part of the profile,  keeping  only the part where the FAT pickings are reliable.

  • Enter the exact distance between the test tubes.

  • Select [ More ]-[Wave Speed Calculator]

The velocity and R2 (coefficient of determination) replace the profile notes,
e.g. "Wave Speed=4200m/s, R^2=0.998"


Internally, CHUM uses a linear regression on the distance vs. FAT vector; the slope of the trend line is the wave speed.

Advantages over laboratory test of a concrete cylinder sample:

  • Intuitive

  • Large sample size: on samples close in size to the wavelength, the wave speed is different than the one in a real pile

  • Averaging many samples, eliminating intermittent noises

  • Affordable: No special equipment or test method is needed

  • Independent of constant delays

  • Good indication of the test reliability (R2)

 

 


8. Behind the scenes

8.1.  Projects, Sub-sites and files

8.1.1. Background

CHUM uses one dedicated folder named "Home folder", located by default in "C:\Pile testing" to store projects. Each project is stored in a sub-folder of the Homefolder.

  • Each pile with all its profiles is stored as a separate file, with the extension .PILE, under the project folder.

  • A project folder also contains a text file called "PISA.PROJECT", which stores the project's titles and other miscellaneous settings.

A pile's file consists of a unit code, a system-wide unique number, the digested pile's name and the extension ".pile". For example, pile 123** will be stored under the name B000059.123__.PILE.

  • B is the unit code (Only relevant for users with more than one CHUM unit)

  • 000059 means this is the 59th pile stored on this system

  • 123___ is the pile's name -- the underscore (_) replaces characters that cannot be used in a filename

  • .PILE is the file extension

The file naming scheme ensures that no two piles will ever get the same file name, and no test work will ever get overwritten or deleted.

For example:

	C:\MY_PILE_TESTING        ← Home folder
	├───1003	             ← A project
	│   ├───A00059.A100.PILE 	← A pile
	│   ├───A00060.A101.PILE 	← Another pile
	│   └───CHUM.PROJECT     	← Project's settings
	│   :
	│   
	├───1004	             ← Another project
	:

 

8.1.2. Sub-Sites

Sub-sites are a way to "break up" a project into smaller parts, which are easier to manage and can produce a clearer report.

For example: if the project contains several buildings, each building can be used as a sub-site. Piles on different buildings can have the same names.

Sub-sites are stored in the file of each pile. and piles are grouped by sub-site when a project is opened.

If the last pile of a sub-site is moved to a different sub-site or deleted, the sub-site is removed. Sub-sites cannot remain empty.

A new pile in a new project is created in the "default" sub-site, and the name does not appear in the report. If you then create a new pile in a new sub-site, CHUM will suggest that you rename the "Default" sub-site to a more meaningful name, to avoid confusion.

8.2.  CHUM filters

8.2.1. Signal Filter

The "Signal filter" is a software algorithm applied to each signal received before the First Arrival Time (FAT), and Energy are picked. The Signal filter cannot be changed. CHUM always saves the raw data before filtering, and then the filtering is carried out in real-time, as needed.

The Signal filter is an optimal linear phase FIR filter based on the Remez algorithm and has the following response:

The graph below shows a signal before the filter is applied to it (gray) and after it is applied (green). It is clearly visible that the lower frequency noise at the left side of the signal was significantly reduced allowing an accurate FAT picking.

 

8.2.2. Profile Filters

Profile filters are three different algorithms applied to the whole profiles of picked data points (FAT and Energy) before they are presented. The user can control these filters by selecting a single filter value F between 0 and 5, where 0 denotes no filter and 5 denotes maximum filtering.

The three filters are the Median filter, Running Averages filter and Delay filter. The Median and Running Averages filters use the theoretical vector of measurements that is convoluted by a relatively large kernel -- the exact size depends on the pulse shape and transducer geometry. The Delay filter is based on an a-priori fact that actual arrival times cannot be significantly lower than the expected arrival time.

Median filter:
Replace each value in a vector with the median value of its neighbors:

A_i \leftarrow \mathrm{median \ of}(A_{i-k}, A_{i-k+1}, \ldots\, A_{i-1}, A_{i}, A_{i+1}, \ldots\, A_{i+k-1}, A_{i+k})

Where k equals the filter value F.

Running averages filter
Replace each value in a vector with the average of its neighbors:

A_i \leftarrow \frac{(A_{i-k}, A_{i-k+1}, \ldots\, A_{i-1}, A_{i}, A_{i+1}, \ldots\, A_{i+k-1}, A_{i+k})}{2 k + 1}

Where k equals the filter value F.

Delay filter:

Find the N percentile arrival time T when N=F * 5
("5" was found experimentally)

Set all arrival times lower than T to T

Examples:

If filter=0, N=0, thus T is the 0 percentile (Minimum) arrival time and the filter does nothing since no time is lower than the minimal time

If filter=5, N=25, thus T is the 25 percentile arrival time, which is usually the normal arrival time of the profile.


The following table shows the same profile FAT values with three levels of processing: without any filter, with a low filter (F=1) and with the maximum filter (F=5):

1 - Noise removed by the Median filter

2 - Noise removed by running Averages filter

3 - Noise removed by the Delay filter

F=0
F=1
F=5

 

8.3.         What is "Attenuation"?

Energy is the amount of energy that arrives at the receiver for each transmitted pulse. Since the energy of the transmitted signals is more or less constant, the energy arriving at the receiver should also be more or less constant .

When a defect in the tested medium blocks the signal, it absorbs some (or all) of the transmitted energy, and a lower energy value is detected at the receiver. Some defects such as necking can significantly reduce the received energy but do not change the FAT since a direct path between the transmitter and the receiver still exists.

Energy is calculated as the sum of the absolute voltage values along the received pulse:

\large E=\sum_i{|V_i|}

Attenuation is calculated as follows:

\large A=20\cdot%20log_{10}(C/E)

Where:

A - Attenuation [dB]
E - The received energy
C - A constant value representing the maximal possible value of received energy

Therefore an Attenuation of ~6 db means that the received energy is about half the maximal possible value since the scale is logarithmic. A shift of ~6 db from the normal attenuation value recorded within a profiles means that the energy has dropped by ~50% at this point, and a shift of ~12 db corresponds to an energy drops to ~25%.

The Chinese standard defines a suspected anomaly as a 6 db attenuation increase relative to the normal attenuation received. This assessment must be backed up by an increase in the FAT .

8.3.1.            How does the energy change with regard to distance?

In a homogeneous medium, the signal attenuation can be calculated according to the following formula:

\large E_r = E_t\cdot e^{-k\cdot f\cdot x}

Where:

E_r - The received energy
E_t - The transmitted energy
k - Attenuation factor of the medium
x - Distance between the transmitter and receive
f - Signal base frequency (Hz)

Sometimes, it is useful to know distance needed to halve the energy of the signal (6db drop):

X = \frac{ln(E_r / E_t)}{-k\cdot f} = -\frac{ln(^1/_2)}{k\cdot f}

Since k and f are constants, x is also constant with a typical value (in good concrete) of 60 cm (2 feet) and much higher values in water.

The following graph was created by holding one sensor at the bottom, and pulling only the other sensor, hence gradually changing the distance. The data was exported to CSV, and plotted using a spreadsheet. The maximum distance logged was 4.5m (!) and the linear correlation was 0.99.  The slope indicates exactly 10 db/m (=6dB/60 cm) - so the energy drops to half every 60 cm. The total energy drop is 40dB = 2 orders of magnitude.

 


9. Tomography

Required equipment

To perform tomography, you need two instrumented depth encoders, and a suitable "Y" depth cable.

 

Overview

To perform tomography in CHUM, pull both transducers together, normally, and when you pass a suspect zone, raise and lower each of the transducers (see instructions below) in to collect diagonal readings. Once the suspect zone has been analzed from all angles, level the transducers and keep pulling normally to the top of the pile, or the next suspected zone.

See here a general description about tomography.

 

Know your left and right!

Important: It is critical to assign the correct depth encoder to the correct access tube. Failing to do so will produce mirror images in 2D tomography, and will produce meaningless results in 3D tomography!

The assignment convention is as follows:

  • the "Y" depth cable splits to a green branch which connects to one depth encoder called "primary" and a red branch which connects to the other encoder, called "Secondary".
    Note: The encoders are identical, the cable branch color marks the role.

  • The primary depth encoder is always assigned to the first profile letter and the secondary, to the second letter.

For example:

  • When logging profile "34", place the primary encoder on tube "3" and the secondary on tube "4".

  • When logging profile "NS", place the primary encoder on tube "N" and the secondary on tube "S".

If you mistakenly logged the data the wrong way, you should re-log the profile, or simply rename it to "43" or "SN".

On the plot, the primary channel is always on the left.

 

How to collect the data?

To collect good data, follow these instructions:

1.          All the profile area should be "covered" by horizontal readings (The software uses those readings for lines plot)

2.          Every pixel in the suspect zone should be covered by at least two forward (//) and two backwards diagonal (\\) readings. The more, the better.

Mathematically, each pulse is a row (Linear equation) in the matrix. To get consistent results, you must get an over-determined matrix (more pulses than pixels). The way the data is collected in the CHUM system generates a good distribution of information (matrix very-over-determined on suspect zones and under-determined in good pile zones)

Note: In order to get consistent results, the data must be collected in a consistent way, for this, a data collection procedure is defined. The procedure collects the data in "fans". As demonstrated below:


The right transducer is lowered in small steps, and for each step a "fan" of samples is performed by the second transducer


You can create a schematic representation of the procedure by plotting D1 against D2
(either D1 or D2 can be primary or secondary)

In other words:

  1. Pull both transducers horizontally until above and out of the defective zone (Point A)
  2. Keep #1 steady, and lower #2 until the signal is almost lost (You can go over +/- 45deg)
  3. Keep #2 steady and lower #1 by a small increment (about 5-10cm = 2-4 inches)
  4. Keep #1 steady and raise #2 until the signal is almost lost, or both #1 and #2 are above the suspected zone
  5. Again, Keep #2 steady and lower #1 by a small increment (about 5-10cm = 2-4 inches)
  6. go to step 2 until both #1 and #2 are below the defect zone (Point B)
  7. Level #1 and #2 to horizontal (+/- 2deg) and continue pulling upwards till the top, or the next suspected zone

An animation of the process can be viewed here:

https://www.piletest-office.com/downloads/TomographyDemo.exe

This might look complicated at first, but it is actually quite simple, and once you practice it, it is very easy to use in the field, and will give you good, consistent results each time.

Take your time, and practice this several times in a non-stressing environment.

While the data is logged, pay attention to the following indications:

  • Primary encoder pulled up (└  ) down ( ┌  ) or steady ( ─ )

  • Secondary encoder pulled up ( ┘ ) down ( ┐ ) or steady ( ─ )

  • Average length pulled from bottom (H:nnn.nn)

  • Angle between transducers (0° is horizontal)

  • FAT and Gain on the oscilloscope window



 

Once the data is collected, it can be viewed and reported in all presentation modes. The data can also be presented in the one-dimensional lines plot or waterfall presentation. For this, the software filters-out the diagonal readings and uses only the horizontal ones.

 

TIP: When performing tomography, change the vertical spacing in the options logger tab to a smaller value, such as 2-3 cm (0.75" -- 1.0 inches)

See also: Signal classification options

Types of tomography

CHUM supports the following types of tomography

  • Real time (Based on simplified fuzzy-logic)

  • Fuzzy-logic

  • Parametric

  • Three Dimensional (3DT) Tomography

The data for all types of tomography is collected in the same way. For 3D Tomography, enough profiles must be collected to cover the pile's cross section.

 

Principle of Fuzzy-Logic (and real time) tomography

In short: "A concrete pixel is painted by the highest category of the rays passing through it."

In detail:

  • The profile is broken into pixels

  • All the rays passing through a pixel are collected, and assigned a color category according to the logical classification conditions you specified.

  • The classification counts are sorted, and the final color is the Nth order-statistics, where N=100-2*Filter (No filter ➤ N=100 = Maximum). Using order-statistics instead of just Maximum compensates noisy readings.  In real-time tomography, N always=100

To speed things up, CHUM uses a variable pixel size. Initially, the whole pile is considered as one pixel. If all rays going through a pixel agree on color (or the pixel is small enough) it is painted, otherwise it is cut into two smaller pixels, and so on.

Limitations of Fuzzy-Logic tomography

  • The calculations are done on apparent wave speed and attenuation. Those are an average of values along the ray path. The apparent value is therefore always higher than (or at best equal to) the value inside the poor-quality pixel. As a result, the contrast of fuzzy-logic tomography is lower than matrix-based solutions.

  • Because of angle limitations, the plotted areas always show "ghost" shadows

 

3D Tomography

 

3DT is an optional component of CHUM and is sold separately.

 

3DT is the next step in tomography, and its success depends on the success of the 2D tomography phases. Be careful -- mediocre 2D results do not produce useful 3D results. 

 

Before performing 3DT, verify the following:

  • FAT pickings have been performed and reviewed.

  • All profile names map to the type layout scheme -- those are used to locate the profiles in the X-Y plane

  • Profile names use the encoders conventions (See Know your left and right)

  • All tube distances are correct

 

Open the Pile details page and select [More] and [3DT]

(Or run the CHUM3DT directly from the start menu)

The 3DT wizard opens

Follow the wizard to perform the matrix inversion. This can take some minutes, or significantly more, depending on the data and your computer.

The results of the calculations are kept in a file, and the next time, you can just view the results instead of re-calculating them.

Once the calculations are done, the following screen appears:

 

3D Image pane: Moving, tilting and zooming the pile.

Action

Mouse

Other

Rotate the camera around the pile axis

Drag Left-Right:

-

Move the camera AND the view point up or down

 Drag Up-Down

-

Move the camera up or down, keeping the view (tilt the pile)

Right Drag + Up-Down
Ctrl + Mouse: Drag Up-Down

-

 

Zoom in or out

Wheel up-down

Zoom in/out icons

Show/Hide the vertical slice disk

Click on mouse wheel

Menu: View - slice plane

Revert to the initial view (If you are "Lost in space")

-

Toolbar: top icon

View the pile's toe

 

Toolbar: bottom icon

Change threshold wave speed

Click/Drag on the palette

-

You may also use a joy stick, if one is connected to your system.

 

The 3D image is plotted using the whole pane width. Drag the separator splitter between the panes to enlarge it, or even hide some panes to get more viewing area.

 

Horizontal slices

From the [View] menu, select [Slice plane] in order to show a semi-transparent plane showing the slice level. Drag the pile up or down to control the slice elevation. Use the middle mouse button, or click the mouse wheel for the same purpose.

The whole horizontal slice pane can be hidden by selecting [Horizontal slices] from the [View menu]. The [-] icon on the pane can also be used for that.

You may instruct the software to collect all the horizontal slices that have low velocities by selecting [Tools]-[Collect...]. the slices are collected into a list, you may remove slices from the list by clicking the small [-] icon on the upper-left corner of each slice. Clicking on the slice moves the pile to that level.

The profile is plotted using the whole pane width. Drag the vertical splitter between the panes to enlarge it.

 

Vertical slices

Drag the [A] and [B] positions around the pile to define your profile. [A] Will be presented on the left.

The profile is plotted to scale (without X-Y distortion) using the whole pane width. Drag the vertical splitter between the panes to enlarge it.

 

Reporting

Reporting is done by a "copy and paste" operation, directly into your report document. Select one of the [Edit]-[copy]-[...] options to copy the desired image into your clipboard.

Switch to your report document, and press Ctrl+V to paste the graphics. Repeat with all the needed graphics.

 

Note: that when pasting directly into your word processor, the slices graphics are copied using a vector format. Using this format the images size can be enlarged and reduced without losing resolution. The format is also more compact in size. The 3D graphics uses simple raster (photo) format.

 

Generating a 3D movie

From the [Movie] menu, select [Action] to start recording. Move the 3D image around to show the anomalies from the best view angles, and select [Cut n' print] to generate the MPEG movie. During the recording, watch the number of frames and the movie file size on the bottom status bar.

TIP 1: Resize the window to a smaller size before starting to get smaller file size movies and faster response during recording.

TIP 2: Movie segments can be easily edited and narrated using a video editing software, such as the free "Windows movie maker" by Microsoft.

 


Appendix A - Frequently Asked Questions (FAQ)

The Frequently Asked Questions (FAQ) below are actual questions asked by Piletest customers.

 


A.1.  Category: The Equipment


What type of computer can we use with your equipment, storage etc.
For testing on site, the ideal computer is a Tablet PC, running Windows XP. We have had excellent experience with tablets, and they are highly recommended.
You can also use a regular notebook computer on site, as long as it runs Windows XP or higher and has a USB port.

Note: The LCD display of normal notebook computers is NOT designed to work outdoors, and intense sunlight may render the screen unreadable.

For office work any Windows computer and printer are acceptable.


Can your equipment correspond with computer?
All our instruments are computer based, under the Windows operating system. The same software is used for testing in the field and analysis and reporting in the office.


A.2.  Category: Test Method


What is the effect of bulging on attenuation?
Bulging has a negligible effect on attenuation, while necking has a marked one.


What is the unit 'dB' used for calculating the attenuation and what is its dimension?
Decibels are commonly used as a relative measurement of attenuation on a log scale. You can read more in https://arts.ucsc.edu/EMS/Music/tech_background/TE-06/teces_06.html. The dB is convenient for our purpose, because it enables us to assign numerical values to attenuation and thus define anomalies quantitatively.


What is the maximal length and diameter of testing piles?
You can use CHUM to test piles of any diameter to depths of 145m!  


Can we test integrity of reinforcement in piles and it length?
No.


 

Can we test reinforced piles?
Absolutely, you can test any concrete piles. The normal amount of reinforcement (<1%) has no influence on the results.


I have a question concerning the CHUM module. Currently we are working on a project in which we are trying to locate an existing below ground tunnel. The tunnel is located in the Cooper Marl formation approximately 100 to 120 feet below the ground surface. The Cooper Marl is a relatively homogeneous calcareous sandy, clayey silt typically used as the bearing layer for the Charleston area. It has typical compressive wave velocities of 5400 ft/sec and shear wave velocities of 1400 ft/sec based on SCPTu testing. The tunnel was 8 feet in diameter when constructed and may or not be lined. My question to you is could the CHUM be used to detect the tunnel? Our plan using the CHUM would be to install inclinometer casing approximately 20 to 30 feet apart and use the tomography option to accurately locate the tunnel. So my questions are: Is the concept feasible? In theory, I would think it is just like detecting a defect in a very weak concrete, but theories have a way of staying theories. If so, would modifications to the CHUM hardware and software be required? The first arrival times would be very long (on the order of 5 microseconds). What would be the approximate cost of these modification be and how long would it take to make them? If not possible, could the CHUM receivers be used to detect shear waves? We were also thinking of possibly using shear waves to detect the tunnel.
As the CHUM maximum range in high-quality concrete is 3-4 meters, I am afraid the energy emitted by the CHUM emitter is just too low to reach those distances and still be of value. This may seem a drawback, but since the CHUM is designed to emit many thousands of pulses per day and still be portable enough it is unavoidable. You will have therefore to consider other techniques.


A.3.  Category: Testing


In the visible graph while pulling out transducers, what does the width of the graph stand for, also what is meant by necking in and out of the graph and also the projection of slight slashes in the graph pulse, please clarify with examples.
The width of the graph is proportional to the received energy. Small changes in real-time are usually noise. Larger changes might indicate defects. Post-processing usually reveals more information. Slight slashes - I'm, not sure what you mean. If it is the diagonal lines on the pulse scope - those are merely a graphical way of showing the FAT. If you meant the crisscross on the logging window - this comes to show a difference between tested and untested areas. Since the display is practically B&W in direct sunlight - this is a simple way of showing a "third" color.


What does the voltage in Scope Window stand for? Has the FAT any relationship with the voltage, as we have observed an inverse proportionality between FAT and Voltage in site.(i.e. as FAT increases Voltage decreases and vice versa) What should be the voltage when we are about to start pulling.
CHUM uses Automatic Gain Control (AGC) - automatically changing the dynamic range of its A/D converter in order to use the range that best fits the sample size. The voltage scale can change in eight levels between 5 V, to 39 mV. As the pulse amplitude drops - CHUM uses a smaller range, and vise versa. The behavior you saw is natural and expected to have the range change in inverse proportion to the FAT (See What is "Attenuation"?)


It was observed that during the testing, we are losing 30 to 35cm of pile length, could you please explain.
This is the transceiver length. Testing starts when the BOTTOM of the transducer touches the BOTTOM of the tube, but stops when the TOP of the transducer reaches the TOP of the tube. If the tube is only 31cm long - the transducer can only move 1cm inside it. This is OK and is inherent to this test method.


We could see that in some cases, the Attenuation curve is touching the FAT curve and in some cases the Attenuation curves come first and then the FAT curve and vice-versa also. Has this got any implications?
No! FAT and attenuation have different units. The curves are plotted on the same area in order to save space and nothing more. If I was to pick different units for the axes, the curves would touch at a different, arbitrary point.


Does pulling velocity have any effect on the test result?
Pulling speed has no effect on the results. The encoder constantly transmits the depth to the instrument, and a pulse is sent in predetermined vertical spacing.


Our CHUM is not showing the exact spacing between the sonic tubes. (for eg. When we measure 0.64m in the site the CHUM is showing 0.88m).we have tried this out in some 10 piles and still the error is existing.
In the leveling screen, the distance is only an estimated (this is why it has the ~ sign next to it) CHUM can only measure time, not distance! The distance is calculated assuming a signal wave speed of 4400m/s. In your case, the signal wave speed might be lower - the concrete might be too fresh or of lower grade/quality. Anyway - the distance value is presented in this screen in order to help you level the pulses, not for reporting.


A.4.  Category: Interpretation


What are the criteria for FAT and  Attenuation to judge pile integrity i.e. during our testing, some FAT will be 184 µs and for other pile it will go to 260 µs. Also how is FAT related to concrete quality and  what is the range of values of FAT and Attenuation for good and  bad piles. Please advise with examples.
FAT stands for First Arrival Time. Since the wave speed in cured concrete is about 4300 m/s (+/- 10%), it will take the wave 1 ms to pass 4.3 m, 500 µs to pass 2.15 m and 250 µs to pass 1.075 m etc. Since profiles are never at the exact same distance, it is expected that the FAT will change. 184 µs is typical for a profile of 0.8 m and 260 µs corresponds to 1.1 m If your FAT is too high for the profile distance, the concrete might not be cured or it is of low quality/grade. The received signal has a measurable energy. The energy drops exponentially as the distance grows. It is expected for the energy to remain roughly constant in a homogeneous concrete. Attenuation is simply the energy in decibels (dB) units, relative to the maximal energy that can be recorded. A change of 6 dB means half the energy, 12 dB is 1/4 the energy, etc. (See What is "Attenuation"?)


A number of the traces show a very large drop in the relative energy, but little or no change in the FAT.  I understand that it is generally taken that the FAT gives the biggest indication of inclusions or defects, however, I note on your web site that a low relative energy means a "weak" signal.  When would I expect to get a weak signal, and could it represent an anomaly even if the FAT's are consistent?
A weaker signal with no change in FAT can be generated when the wave path becomes smaller, for example, in the case of a necking.

As seen in this image, the shortest path between source and receiver is not disturbed; therefore the FAT shows no indication of the defect. However, the total amount of energy reaching the receiver is significantly reduced. This is just one way of explaining this phenomenon. I am not aware of any research done to quantify it or find additional explanations. There is no way to assess the size and severity of the defect (if it is indeed a defect) from this trace, but you can quite confidently assess that if the energy dropped significantly (say by 18 dB or more in the attenuation curve) you need not crying wolf.


In general the traces are quite smooth (about a vertical line), but every now and then the line is very jagged, although still about a vertical line. Does this sound like a problem?
Concrete is not a homogeneous material and some variations of the FAT and attenuation are to be expected even in the most controlled environment. Unless you can see a significant change in FAT or energy (And I cannot quantify this change) you are safe.


How can we estimate the distorted area of the pile, from FAT and  Attenuation?
There is no standard, and you have to apply solid judgment for changes in FAT or attenuation. I recommend that you send the files to us. We will be glad to assist you with the interpretation until you feel confident enough.


Which is the easiest method of evaluating a pile, like FAT vs. Attenuation or FAT vs. Energy. Explain.
Those are equivalent. Originally CHUM only showed Energy (without units). We introduced Attenuation in a later version, but kept the energy option for backward compatibility for those users who were used to presenting and submitting energy curves in their reports.


In our Equipment, for the PRESENTATION of results, we are allowed to choose from FAT, Attenuation, Relative Energy and  Apparent wave speed. BUT, when we choose the Apparent wave speed option, we are able to see a green legend for Apparent wave speed in the bottom of the graph and  also the wave speed written in m/s. BUT, there is no representation of it in the graph.
CHUM can only measure arrival time, not signal wave speed. In order to plot the wave speed curve, you must enter the horizontal spacing between the tubes. Once you enter this value, you will be able to see the wave speedcurve.  


A.5.  Category: Reporting


Can we copy or duplicate a pile in the CHUM.
No. But you can do this in Windows - open the project folder, copy the file (right-click - copy, right-click on the folder - paste). Now re-open the project and rename the pile. May I ask why you need this option?


A.6.  Category: Training


Do you conduct the seminars for users?
Training can be arranged at cost.


 


Appendix B - Checklists

Before going out to a site, check that the software is installed correctly (you should look for new CHUM versions at least once a month in the Piletest.com user community download area), and that the instrument's battery is fully charged.. Check that you have the following equipment with you:

  • The CHUM instrument

  • Charged and installed computer

  • A set of transducers (emitter and receiver)

  • Two pulleys, including at least one depth meter.

  • A depth cable

  • The relevant project documents

  • Measuring tape

  • Adhesive tape

  • Permanent marker

Optional Equipment:

  • battery charger / lighter charger

  • A sounder / Dummy probe

Tip:

In hot weather: Take sufficient drinking water, and a hat.

In cold weather: Take warm clothing, and a hot drink?

 

 


Appendix C - Troubleshooting

C.1.  Symptoms

C.1.1  Symptom:  No Signal, or no response from the CHUM

 

Please use the following procedure to troubleshoot this problem:

 

1.          Connect your set of transceivers and place them in a bucket of water.

2.          Connect the USB connector to your computer

3.          Start the CHUM software

4.          ?: The green LED on the CHUM panel is OFF

•        Possible diagnostics: Low or dead battery

•        Possible diagnostics: Damaged computer USB port

•        Possible diagnostics: Damaged CHUM unit

5.          Click the test icon

6.          Make sure the USB CHUM data source is selected

7.          Press [Test] or [➤]

8.          ?: The software displays an I/O error message

•        Possible diagnostics: Low or dead battery

•        Possible diagnostics: More than one instance of CHUM is running

•        Possible diagnostics: An additional CHUM/PET system is connected.

9.          ?: A No error message, the scale at the oscilloscope window is low (39 mv) and there is no distinctive signal

•        Possible diagnostics: Damaged transceiver

10.       If you have a transducer emulator, connect it

11.       ?: The greed LED on the emulator is flashing

•        Possible diagnostics: Damaged transceiver

12.       ? : CHUM works well outside, but not when testing a real pile

•        Possible diagnostics: no water in the access tubes

•        Possible diagnostics: Defective pile/soft bottom

 

C.1.2.  Symptom:  Wrong or inconsistent depth readings

 

Please use the following procedure to troubleshooting this problem:

 

  1. Connect the depth encoder(s) and the depth cable

  2. Connect the USB connector to your computer

  3. Start the CHUM software

  4. Click the test icon

  5. Make sure the USB CHUM data source is selected

  6. Press [Test]  or [➤]

  7. Use a pencil to mark a line on the depth wheel

  8. Rotate the depth encoder 360 degrees clockwise, and then counter clockwise to about the same point. Watch the "counters" reading

  9. ? The counter reading did not change at all

        Possible diagnostics: Damaged depth cable

        Possible diagnostics: Damaged depth encoder

        Possible diagnostics: Damaged CHUM unit

  1. ?: You are using two encoders and each one moves in a different direction

•        Possible diagnostics: One of the encoder bases is rotated 180 degrees. Disassemble and fix it.

  1. ?: You using two encoders. They both change the same way, but at different speed (Different counts/revolution)

•        Possible diagnostics: Two encoder models are used. Don't mix and match encoders from different models, contact Piletest.com for a workaround.

  1. ?: The counter reading changed to +/- 1 and 0, but nothing beyond that.
    or

  2. ?: The counter reading changed only in one direction

•        Possible diagnostics: Damaged depth cable

•        Possible diagnostics: Damaged depth encoder

  1. ?: The counter reading changed significantly in one directionand then back to (nearly) zero?

  2. Perform depth calibration, twice to verify reproducibility

  3. ?:  The results of each calibration are very different (More than 0.1% off)

•        Possible diagnostics: The wheel might have collected too much dirt/ice and does not rotate freely, so the cable slips over it

•        Possible diagnostics: Damaged depth cable

 

 

C.2.  Possible diagnostics:

C.2.1. Possible diagnostics: Low or exhausted battery

Connect the CAR charger to the CHUM unit, and use a voltmeter to measure the voltage directly.

See CHUM internal battery and battery charger

C.2.2. Possible diagnostics: Damaged computer USB port

•      Connect the CHUM unit to another computer with CHUM installed to verify the problem is really the USB port

•      Try to connect other peripherals, such as a mouse or a disk-on-a-key to the port, and verify that it works correctly

C.2.3. Possible diagnostics: Damaged CHUM unit

If you have verified that the unit is indeed defective, Contact support@Piletest.com

C.2.4. Possible diagnostics: More than one instance of CHUM is running

Open Task Manager -- (Ctrl-Alt-Delete) and switch to the Processes tab. Check [●] Show Processes from all Users, sort by process name and look for CHUM.EXE -- only one instance is allowed. Kill all other instances.

C.2.5. Possible diagnostics: An additional CHUM/PET system is connected.

Simply disconnect other CHUM/Pet units.

C.2.6. Possible diagnostics: Damaged transceiver

•        Try to swap the transceivers (Tx ⇔ Rx), if this solves the problems, one or more of the transceivers is not functioning as dual-purpose anymore.

•        If you have a spare transceiver, try all 6 combinations to pinpoint the faulty function.

•        Examine the transceivers' cable manually for physical damage.

C.2.7. Possible diagnostics: Damaged depth cable

•        Visually inspect the cable for physical damage.

•        Use an Ohmmeter to test the cable connectivity end-to-end.

C.2.8. Possible diagnostics: Damaged depth encoder

•        Visually inspect the encoder for physical damage, high friction or water penetration.

•        Cross-check with other encoders, if available.


Appendix D - Anomaly, Flaw, or Defect?

 

When discussing pile integrity, it is important to distinguish between three terms that are often confused:

  • An anomaly is any irregular feature in the NDT graphic results. An anomaly may be due to the testing instrument (such as noise), the means used (access tube debonding in a cross-hole test), the surrounding soil (abrupt changes of soil friction in the sonic test), or to the pile itself. It is the responsibility of the testing laboratory to gather and analyze all relevant data and try to resolve every anomaly before it is declared a flaw.

  • A flaw is any deviation from the planned shape and/or material of the pile.

  • A defect is a flaw that, because of either size or location, may detract from the pile's capacity or durability. The geotechnical and the structural engineers are jointly responsible to decide which flaw comprises a defect.


 


 

Appendix  E - Theoretical background

E.1.  Ultrasonic Testing - Basic Principles

The sonic ("low strain") method belongs to the external test-methods, as it accesses only the top of the pile. Ultrasonic logging, on the other hand, is intrusive and necessitates the prior installation of access tubes (Usually two or more) in the pile. Before the test they have to be filled with water (to obtain good coupling) and two transducers are lowered inside two of the tubes. One of these transducers is an emitter and the other a receiver of ultrasonic pulses. Having been lowered to the bottom, the transducers are pulled simultaneously upwards to produce an ultrasonic logging profile. The emitter repeatedly produces ultrasonic wave bursts in all directions. These waves do eventually reach the receiver. The testing instrument then plots the travel time between the tubes versus the depth. As long as this time is fairly constant, it shows that there is no change in concrete quality. A sudden increase of the travel time at any depth indicates a defect at this depth. The cross hole method has been described in a number of recognized standards (AFNOR 1993, ASTM 2002 ). As we shall see later, the cross-hole method may be further refined to produce high-quality results.

A variation of ultrasonic logging is the single-hole method (Amir 2002): In this method both emitter and receiver are lowered, with a fixed pre-determined vertical spacing, in the same tube (or hole). In this case the waves do not travel across, but rather along, the pile axis.

While the access tubes introduce an extra expense item, the cross-hole technique compensates for this by allowing the testing equipment to approach potential defects. An additional advantage of this test is the enhanced resolution: While the sonic test uses a wavelength of at least two meters, the cross-hole method utilizes ultrasonic frequencies, with typical wavelengths of 50 to 100 mm. Since resolution is strongly dependent on the wavelength, the cross-hole method enables us to locate even minute defects.

 

Because of these short wavelengths, the one-dimensional theory, on which we based the sonic method,  is no longer applicable. Thus, we have to look into the theory describing  the behavior of waves in space.

E.2.  Three-dimensional wave propagation

In prismatic rods, we meet only one type of wave - the one-dimensional longitudinal wave which can be either compressive or tensile.

Body waves moving in a three-dimensional elastic space, however, may be of two distinct types: Dilatational (P-Waves) and distortional (S-Waves).

When the displacements associated with the wave occur on the axis of wave propagation (as in the rod), the waves are called longitudinal or P-Waves. The particles in this case may move either in the same direction (compressive wave) or in the opposite direction (tensile wave). P-Waves are accompanied by volume expansion or decrease.

When the wave causes particles to move perpendicular to its direction of motion, the waves are known as S-Waves or shear waves. The character of S-Waves is further determined by the direction of displacement: When particle displacements are horizontal, the waves are called SH-Waves. SV-Waves, on the other hand, are characterized by vertical motion. A general S-Wave may be decomposed into its SV and SH components.

As mentioned before, waves radiate from the point of application of any dynamic  load. As the distance from this point increases, the waves may be assumed to travel as a plane front. All material particles then move in this plane (S-Waves) or perpendicular to it (P-Waves). This assumption leads to substantial simplification in the mathematical treatment: If we denote the particle displacement by ψ, then the propagation of plane waves is governed by the following differential equation:

\frac{\partial ^2\psi}{\partial t^2} = c^2 \frac{\partial ^2\psi}{\partial x^2} Equation 1

in which c^2 = \frac{E}{2 \rho (1+\nu)}  for S- (or distortional) Waves and c^2 = \frac{E}{\rho}\cdot\frac{(1-\nu)}{(1+\nu)\cdot(1-2\nu)}  for P- (or dilatational) Waves. c, as usual, is the wave propagation speed. For Poisson's ratio \nu =0.25, the speed ratio cP/cS is equal to \sqrt{3}, which means that P-Waves propagate much faster than S-Waves. For good-quality concrete, cS=2,580 m/sec and cP = 4,470 m/sec. In comparison, c for a rod of the same material is equal to 4,080 m/sec.

To visualize the behavior of plane wave, we often prefer to trace a single normal to the wave front, and follow its' path. As an analogy to optics, the trajectory of such a normal is termed a ray path.

E.3.  Attenuation

When a wave front moves away from the emitter, it becomes larger with distance. If we assume that no energy is lost during the process, the energy per unit area of the front (or per ray) declines with distance. The rate of decrease depends on the shape of the front. If the front is spherical, the wave energy per unit area will change as the inverse of the square of the distance from the source:

\frac{E_{2}}{E_{1}} = \left(\frac{r_{1}}{r_{2}}\right)^2 Equation 2

Where: E_1 and E_2 denote the wave energies at points 1 and 2, respectively, while r_1 and r_2 are the respective distances from the source of  points 1 and 2. Since the energy E is proportional to the square of the amplitude A, Equation 2 can be re-written as:

\frac{A_{2}}{A_{1}} = \frac{r_{1}}{r_{2}} Equation 3

Equation 3 describes what we define as geometric attenuation, which occurs in all types of media and is the only source of energy loss in perfectly elastic materials. In real materials, which also exhibit viscous and frictional behavior, part of the mechanical energy of the waves is constantly converted into heat. This phenomenon, defined as material loss or intrinsic attenuation, is represented by the following equation (Santamarina et al. 2002):

  A_{2} = A_{1}\cdot e^{-k\cdot f(r_{2}-r_{1})} Equation 4

in which k is a medium-dependent constant and f is the wave frequency.  Equation 4 shows clearly that material attenuation causes the wave amplitude to  decrease  with increasing distance from the source, at a rate that is dependent on the frequency. Higher frequency waves attenuate much faster than those with lower frequencies and therefore have a smaller range.

Since wave amplitudes may vary over a few orders of magnitude, it is convenient to express amplitude ratios on the decibel scale, defined as dB=20\cdot%20log(A_2/A_1). Since 20\cdot%20log(^1/_2) \approx 6 , every 6 dB represent an amplitude ratio of 2. 

Figure 1 is an example obtained by passing ultrasonic waves in a concrete pile while varying the distance between the emitter and the receiver. The exponential character of the attenuation is immediately apparent.

Figure  1: Attenuation of Ultrasonic Waves in Concrete

E.4.  Waves in an elastic half-space

When a dynamic load is applied at the free surface of a boundary, both P- and S- waves radiate from the point of application into the body. In addition, this load will produce surface waves that are not dissimilar to the ripples created by throwing a stone into calm water. These surface waves, named after Lord Rayleigh, include longitudinal and transverse components. They are confined to a thin layer close to the surface and propagate at a wave speed that is slightly smaller than cS.

Inside an infinite uniform body, plane body waves will propagate in straight lines. In a half-space, some waves will eventually hit the boundary x = 0 and will be reflected back into the body having undergone several changes:

When the waves hit the boundary at a right angle, P-Waves will change sign: Compressive waves are reflected as tensile, and vice versa. This follows directly from the requirement that the boundary be stress-free.

When a wave meets the boundary at an angle q1<900, it undergoes mode conversion and is reflected back as two distinct waves: A P-wave is reflected at the angle of incidence q1, and an SV-wave is reflected at a different angle q2< q1 (Fig. 1 - Kolsky p. 24).

When the incident wave is of SV type, it will create two distinct reflected waves: An SV-wave will be reflected at the angle of incidence q2, and a P-wave at a larger angle q1.

 

Figure  2: Reflection of P-Waves from the boundary x = 0

The amplitudes of both reflected waves depend on the amplitude of the incident wave, the angle of incidence and Poisson's ratio (Kolsky pp. 27-28).

E5. Waves in Non-homogeneous Media

Up to this point we have dealt with homogenous media. For our purposes, a medium is defined as non-homogenous when it fulfils the following two conditions:

1.      The medium includes zones with different characteristic impedance (Z=ρ•c)

2.      The typical size of these inclusions d is much larger than the wavelength λ.

In such media, whenever a wave hits an inclusion, its propagation pattern will change at the interface. Here we shall distinguish between two cases:

Normal incidence

When a wave with an amplitude Ai travels from a region with the impedance Z to a region with another impedance Z' through a normal interface, it will be partly reflected back with an amplitude Ar while another part will pass through the interface with an amplitude At.

Therefore, when a wave meets a weaker region (Z'<Z) it will change sign: A compressive wave will be reflected as a tensile wave, and vice versa. If, on the other hand, Z'>Z the reflected wave will preserve the sign of the incident wave.

This ratio At/Ai is always positive, which means that the transmitted part of the wave will preserve the sign of the incident wave.

Oblique Incidence

When a wave meets the interface at an angle θ1 to the normal, it will create four new waves: Two of them reflected and two - refracted (Figure 3).

Figure  3: Reflection and refraction of P- and SV-waves

 

E.6.  Media with inclusions

A generalization of the case, which we discussed above, is that of a given medium with an inclusion of an arbitrary shape having different properties. This situation, by the way, is of most importance to those who are in the business of locating defects in cast- in-situ concrete piles. From our previous discussion we may now realize that in a typical case, an incident wave will create four distinct waves when hitting the inclusion. Of these, two will enter the inclusion at different angles, and each of those may create four more waves upon leaving the inclusion. Thus, for each ray path hitting a typical inclusion there will  be two waves reflected back from its boundary and a number of waves leaving at various locations and angles. Clearly, a mathematical treatment of the general case (An inclusion with an arbitrary form) is rather hopeless. Idealized cases, such as a plane wave in an infinite medium with a spherical or cylindrical inclusion, may be treated by analytical methods using infinite series (Graff p. 394 ff.).

A typical case of a plane P-wave hitting a cylindrical inclusion is demonstrated (For a single ray path) in Figure 4. In this example, a single wave creates three pairs of waves exiting the cylinder. We note immediately that none of these follows the original trajectory! The amplitudes of each wave and its sign (either compressive or tensile) are shown as a fraction of the amplitude of the incident wave.

Figure  4: A P-wave hitting a cylindrical inclusion