Free Fall Cone Penetrometer (FFCPT)

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FFCPT-660
4-Page Brochure
( 413k PDF File )
[ Web Version ]

MVP-FFCPT Paper from UDT Conference Dec 2006
(1.3MB PDF File)

PowerPoint Presentation from Canadian Hydrographic Conference 2006
(19MB PPT File)

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Harpoon FFCPT
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Free Fall Cone Penetrometer (FFCPT)

Geotechnical Applications of the FFCPT

Retrieving the FFCPT After a Deployment [Click to enlarge]

Component Modules of the FFCPT [Click to enlarge]

The Free Fall Cone Penetrometer (FFCPT) was developed to collect geotechnical and geophysical data during route location surveys for seabed cable and pipeline installations, for bottom classification and acoustic ground-truthing, as well as for mine countermeasures and geo-environmental studies.

FFCPT is a very robust device designed to free fall through the water column, then impact the seabed. Onboard acceleration and pressure sensors monitor the sediment penetration response, producing continuous profiles similar to a conventional piezocone penetrometer. FFCPT test results can be used to evaluate:

Seabed classification; acoustic groundtruth (grain size, correlation to sidescan sonar reflectivity or multibeam backscatter maps)
Geotechnical site investigation (alternative to CPT on cable and pipeline route surveys; also shallow foundations)
Dredging quantity surveying (thickness and density of fluid mud layers)
Stability of Contaminant Disposal sites (integrity of capping blankets, consolidation of capped waste)
Naval applications (mine countermeasures research)

Screenshot from FFCPT Software [Click to Enlarge]

The standard FFCPT weighs 52 kg and can achieve 2-3m penetration in soft clays and silts. Sensor data is acquired at a rate of 2,000 Hz and is stored to non-volatile flash memory. Datalogging is initiated after a preset trigger depth has been reached. Data is downloaded after each deployment. The screen at right shows a typical data set as recorded by the probe.

FFCPT results provide information on:

Layering within the sediment column
Undrained shear strength (deduced independently from dynamic penetration and pore pressure response)

Shear strengths determined with FFCPT are more reliable than with conventional CPT systems in very soft clays due to the enhanced sensitivity. FFCPT can detect fluid mud suspensions that exist above the seabed using optical reflectance techniques.

Interpreted profile of undrained shear strength, determined from two (2) independent measurements (dynamic penetration resistance and pore pressure response).

Pore pressure data have been used to calculate the normalized penetration resistance (Q_n) and the pore pressure ratio (B_q), used to classify the sediment, as indicated by the Sediment Behaviour Type (SBT).

Readying FFCPT for Deployment [Click to enlarge]

The photograph shows FFCPT being readied for deployment. The lightweight version typically penetrates to depths of 1-2m in silts and 2-3m in soft clays. Weighted ballast sections are added for deeper penetration testing. Stabilizing fins allow for stable vertical free fall into the seafloor.

Seafloor Sediment Classification Using the FFCPT
The FFCPT offers a low-cost, rapid, reliable method for obtaining information on the engineering and sedimentological characteristics of sediment at the seafloor. The equipment can be rigged to optimize testing within a given depth window of soft sediment. This feature makes it ideal for route location surveys, where regional coverage of the seafloor is more desirable than detailed information at any particular site.

FFCPT testing can be performed using a freewheel-capable winch such as an MVP200 or a variety of recovery winches / capstans, if they permit free fall during deployment. Data from an FFCPT test is shown plotted on a Robertson chart (below), which is useful in evaluating sediment composition.

Please note the elements of the animation shown above are not to scale.

The hi-resolution version of the above Flash animation illustrating the UNDERWAY CAPABILITIES of the FFCPT is available HERE!

FFCPT is designed to survive impact with a hard bottom (bedrock). Acquired data is used to distinguish between rock, gravel, sand, silt and clay, as well as to provide index information on density and stiffness. FFCPT testing can be accomplished from the same vessel used for geophysical surveying, giving immediate feedback on bottom sediment classification, dynamic moduli, density, porosity and shear strength.

The active section is instrumented with a computer datalogger and sensors for evaluating geotechnical characteristics of marine sediment, including accelerometers, pressure transducers and an optical backscatter (OBS) to determine the mud/water interface. The standard FFCPT package uses 3 accelerometers (3g / 20g / 90g), 2 pressure transducers (currently 1000psi) and an OBS. Other sensors are planned for future applications (call for details). The FFCPT is shown here being deployed using ODIM Brooke Ocean's Moving Vessel Profiler™ 200 (MVP200) winching system installed on the CCGS Matthew.

FFCPT deployed using ODIM Brooke Ocean's MVP™200

FFCPT can also be fitted with an optional SV&P sensor. This permits sound velocity and pressure readings to be collected from the water column as the probe freefalls to the seafloor.

ODIM Brooke Ocean and its development partners are continuing to test FFCPT as a payload on our MVP (Moving Vessel Profiler™), a commercial winching / telemetry system for underway sound-velocity profiling of the water column. Deploying FFCPT on station using the FFCPT with Experimental Nose Cone

MVP enables simultaneous collection of high-quality geotechnical data during geophysical surveying operations. FFCPT / MVP packages are currently available for stationary (on station) and underway deployment applications. Underway geophysical surveying increases the number of sites that can be tested per day. Contact ODIM Brooke Ocean if underway FFCPT testing can benefit your application!

A variety of configurations of the FFCPT are now available that provide different instrument packages and seabed penetration characteristics (see photo to the left). Contact ODIM Brooke Ocean for more information.

The HARPOON FFCPT was developed for use with conventional piston or gravity corer systems. Find out more information here.

The following testimonials are available regarding FFCPT:

• Defence Research Development Canada (DRDC) Atlantic (1MB)
• Natural Resources Canada (Harpoon FFCPT) (136k)

ALSO AVAILABLE:

MVP-FFCPT Paper Presented at UDT-Pacific Conference December 2006 by Arnold Furlong, Brooke Ocean Technology. Download a copy here (1.3MB).
2-page FFCPT handout produced by DRDC. Download a copy here (326K).

This document is provided courtesy of DRDC Atlantic.

"The Integration of the Free Fall Cone Penetrometer Test (FFCPT) with the Moving Vessel Profiler (MVP) for the Rapid Assessment of Seabed Characteristics" - PowerPoint presentation from the Canadian Hydrographic Conference 2006 (John C. Osler - DRDC Atlantic, Arnold Furlong - Brooke Ocean Technology, Harold Christian - Christian Situ Geosciences Inc., Mike Lamplugh - Canadian Hydrographic Service). PLEASE NOTE: This is a VERY LARGE file (19MB) and may take some time to download. Right-click here or on the image and select "Save Target As..." to save the .PPT file to your hard drive.
This document is provided courtesy of DRDC Atlantic. If you do not have PowerPoint or the PowerPoint Viewer installed, click here or here (Microsoft site) to download a copy of the free PowerPoint viewer.

For more information, please contact ODIM Brooke Ocean.

Download the FFCPT brochure (PDF 413k).

The Free Fall Cone Penetrometer (FFCPT) was developed jointly with Defence Research and Development Canada Atlantic.

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