CA2689489A1 - Free fall cone penetrometer test - Google Patents
Free fall cone penetrometer test Download PDFInfo
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- CA2689489A1 CA2689489A1 CA 2689489 CA2689489A CA2689489A1 CA 2689489 A1 CA2689489 A1 CA 2689489A1 CA 2689489 CA2689489 CA 2689489 CA 2689489 A CA2689489 A CA 2689489A CA 2689489 A1 CA2689489 A1 CA 2689489A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V11/00—Prospecting or detecting by methods combining techniques covered by two or more of main groups G01V1/00 - G01V9/00
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B27/00—Arrangement of ship-based loading or unloading equipment for cargo or passengers
- B63B27/08—Arrangement of ship-based loading or unloading equipment for cargo or passengers of winches
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B2211/00—Applications
- B63B2211/02—Oceanography
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Abstract
A system is taught for collection of ocean and seabed data from a moving vessel. The system includes a modular free fall probe for collecting data and a winch system including a drum. A line puller maintains tension on the drum when the probe impacts the seabed and a controller controls rotation of the drum for retrieval of the probe. A method is also taught for collecting ocean and seabed data from a moving vessel by first deploying a probe along a line from a moving vessel and then allowing the probe to free fall through a water body until it impacts a seabed. A line puller is engaged to maintain tension on the drum during free fall and at impact. The line feed is terminated and the line puller is disengaged after impact of the probe with the seabed and the probe is extracted from the seabed by action of the moving vessel. The line is then winched back to retrieve the probe, which is then maintained in a towed position for further deployment.
Description
Free Fall Cone Penetrometer Test Field of the Invention This invention relates to a system for obtaining oceanographic profile data from a moving vessel.
Background of the Invention Determination and characterization of ocean and seabed parameters is an important part of physical oceanography, climate studies, fisheries and naval operations. When conducting oceanographic surveys it is often difficult to collect continuous, accurate data and process such data in real-time.
Various devices are known or have been proposed for the collection of data relating to ocean properties such as temperature, salinity and other characteristics. These are commonly known in the art as CTD
(Conductivity-Temperature-Depth) probes. Examples of prior devices are disclosed in U.S. Pat. No.
3,339,407 to Campbell, et al., and U.S. Pat. No. 3,397,573 to Carter. In these patents the probes described are expendable.
Other devices are used to measure seabed characteristics. Those known in the art include conventional push-cone probes and in-situ sound speed and attenuation probes, or ISSAP, as developed by Kraft et al., 1992. Free-falling devices include the expendable bottom penetrometer (XBP) taught in US
5,681,982 by Stoll and Akal and the sediment terminal impact Newton gradiometer (STING), by Poeckert et al. 1997. Also known are the expendable Doppler penetrometer (XDP) by Beard, 1984, free fall resistivity penetrometers by Rosenberger, 1999 and a free fall cone penetrometer (FF-CPT) by Stegmann.
Collection of physical seabed samples is a time consuming and involved process and cannot be conducted from a moving vessel. As well, it is nearly impossible to maintain samples in their original temperature and pressure conditions once they have been brought to the surface for assessment.
It is greatly desirable to facilitate real-time acquisition of water column and seabed data, without discarding probes on the seafloor. Furthermore, it would be desirable to be able to provide automated and repeated deployment and retrieval of a descending probe while the vessel is in motion. Operation with various types of vessels in transit at the normal velocity of the vessel is also highly sought.
Summary of the Invention The present invention provides a system for the automated collection of ocean and seabed data from a moving vessel. The system comprises a hydrodynamically streamlined, modular free fall probe for collecting data from a water body and from a seabed and a winch system including a drum for storing a line connecting the probe with the vessel. A line puller, disengagebly connected to the winch system, maintains tension on the drum when the probe impacts the seabed and a controller controls rotation of the drum for retrieval of the probe.
The present invention further comprises a method of collecting ocean and seabed data from a moving vessel. The method comprises first deploying a probe along a line from a moving vessel, wherein said line is fed from a drum via a winch to the probe and then allowing the probe to free fall through a water body until it impacts a seabed. A line puller on the winch is engaged to maintain tension on the drum during free fall and at impact. The line feed is terminated and the line puller is disengaged after impact of the probe with the seabed and the probe is extracted from the seabed by action of the moving vessel tightening and pulling the line. The line is then winched back to retrieve the probe. The probe is then maintained in a towed position for further deployment.
Brief Description of the Drawings The present invention is now described in further detail, with reference to the following drawings in which:
Figure 1 is an illustration of the overall system of the present invention;
Figure 2 is an illustration of one embodiment of the winch system of the present invention;
Figure 3 is an illustration of one embodiment of the free fall cone penetrometer of the present invention;
Figure 4 is a schematic diagram of a preferred embodiment of the process of the present invention;
Figure 5 is a plot of pull-out loads as a function of vessel speed at four sites from the field trials;
Figure 6 is a plot of impact velocity of the FFCPT with the seabed as a function of vessel speed;
Figure 7 is a plot of the actual depth of FFCPT penetration as a function of vessel speed; and Figure 8 is a plot of a combination of FFCPT results with different survey information. Thin vertical red lines are FFCPT drop locations. Pseudo-cores of sediment behaviour type as a function of depth of penetration are plotted at each FFCPT drop location.
Description of the Preferred Embodiments With reference to Figure 1, the system includes a probe 2, preferably in the form of a free fall cone penetrometer test (FFCPT), a line 4 and a moving vessel profiler (MVP) 6 mounted on a vessel 8.
Background of the Invention Determination and characterization of ocean and seabed parameters is an important part of physical oceanography, climate studies, fisheries and naval operations. When conducting oceanographic surveys it is often difficult to collect continuous, accurate data and process such data in real-time.
Various devices are known or have been proposed for the collection of data relating to ocean properties such as temperature, salinity and other characteristics. These are commonly known in the art as CTD
(Conductivity-Temperature-Depth) probes. Examples of prior devices are disclosed in U.S. Pat. No.
3,339,407 to Campbell, et al., and U.S. Pat. No. 3,397,573 to Carter. In these patents the probes described are expendable.
Other devices are used to measure seabed characteristics. Those known in the art include conventional push-cone probes and in-situ sound speed and attenuation probes, or ISSAP, as developed by Kraft et al., 1992. Free-falling devices include the expendable bottom penetrometer (XBP) taught in US
5,681,982 by Stoll and Akal and the sediment terminal impact Newton gradiometer (STING), by Poeckert et al. 1997. Also known are the expendable Doppler penetrometer (XDP) by Beard, 1984, free fall resistivity penetrometers by Rosenberger, 1999 and a free fall cone penetrometer (FF-CPT) by Stegmann.
Collection of physical seabed samples is a time consuming and involved process and cannot be conducted from a moving vessel. As well, it is nearly impossible to maintain samples in their original temperature and pressure conditions once they have been brought to the surface for assessment.
It is greatly desirable to facilitate real-time acquisition of water column and seabed data, without discarding probes on the seafloor. Furthermore, it would be desirable to be able to provide automated and repeated deployment and retrieval of a descending probe while the vessel is in motion. Operation with various types of vessels in transit at the normal velocity of the vessel is also highly sought.
Summary of the Invention The present invention provides a system for the automated collection of ocean and seabed data from a moving vessel. The system comprises a hydrodynamically streamlined, modular free fall probe for collecting data from a water body and from a seabed and a winch system including a drum for storing a line connecting the probe with the vessel. A line puller, disengagebly connected to the winch system, maintains tension on the drum when the probe impacts the seabed and a controller controls rotation of the drum for retrieval of the probe.
The present invention further comprises a method of collecting ocean and seabed data from a moving vessel. The method comprises first deploying a probe along a line from a moving vessel, wherein said line is fed from a drum via a winch to the probe and then allowing the probe to free fall through a water body until it impacts a seabed. A line puller on the winch is engaged to maintain tension on the drum during free fall and at impact. The line feed is terminated and the line puller is disengaged after impact of the probe with the seabed and the probe is extracted from the seabed by action of the moving vessel tightening and pulling the line. The line is then winched back to retrieve the probe. The probe is then maintained in a towed position for further deployment.
Brief Description of the Drawings The present invention is now described in further detail, with reference to the following drawings in which:
Figure 1 is an illustration of the overall system of the present invention;
Figure 2 is an illustration of one embodiment of the winch system of the present invention;
Figure 3 is an illustration of one embodiment of the free fall cone penetrometer of the present invention;
Figure 4 is a schematic diagram of a preferred embodiment of the process of the present invention;
Figure 5 is a plot of pull-out loads as a function of vessel speed at four sites from the field trials;
Figure 6 is a plot of impact velocity of the FFCPT with the seabed as a function of vessel speed;
Figure 7 is a plot of the actual depth of FFCPT penetration as a function of vessel speed; and Figure 8 is a plot of a combination of FFCPT results with different survey information. Thin vertical red lines are FFCPT drop locations. Pseudo-cores of sediment behaviour type as a function of depth of penetration are plotted at each FFCPT drop location.
Description of the Preferred Embodiments With reference to Figure 1, the system includes a probe 2, preferably in the form of a free fall cone penetrometer test (FFCPT), a line 4 and a moving vessel profiler (MVP) 6 mounted on a vessel 8.
As seen in Figure 2, the MVP 6 includes a winch 10, a drum 12 for storing the line 4 that connects the probe 2 with the vessel 8, a line puller 14, a controller, brake means and one or more sensors. Both the probe 2 and the winch 10 are equipped with real-time data telemetry modules.
The winch 10 is preferably a self contained electro-hydraulic winch.
The line puller 14 acts to prevent slack line 4 on the drum 12 when the FFCPT
impacts the seabed. The line puller 14 comprises a pair of traction rollers along which the line 4 travels off the drum 12 during descent of the probe 2 through the water body to the seabed 22. The traction rollers are mounted in a housing which is pivotally mounted about a horizontal pivot whose axis is generally perpendicular to a longitudinal axis of the vessel 8. Preferably the line puller 14 is directed astern of the vessel 8 during line 4 deployment, to ensure proper operation of the line puller 14 and to ensure better handle of pullout loads by the MVP 6 structure.
The line puller 14 is hydraulically driven and incorporates a clutch bearing to allow the traction rollers to freewheel during free fall yet be driven once tension is removed from the cable. The line puller 14 may remain in place in a deactivated mode for operations with alternate payloads such as, for example, sound velocity pressure (SVP) and CTD sensor payloads. A quick engage/disengage lever advantageously allows for quick engagement or disengagement of the line puller 14 as required by the particular payload to be used.
The winch 10 is powered by a suitable motor 24 that is interconnected with the drum 12 by a clutch, and provided with break means. The winch 10 can be secured to the deck in a variety of configurations. The MVP 6 is preferably mounted at the stern of the vessel 8 and deploys directly off the stern. It is also possible to deploy other equipment such as a sidescan sonar, sound sources, one or more streamers and magnetometers simultaneously with the MVP system 6 without disrupting its operation or the operation of neighbouring systems on the vessel 8.
For operation with the FFCPT, the present MVP system 6 includes supplemental bracing to the frame, a load cell to monitor pull-out loads, and modifications to the controller to prevent damage to the winch motor 24 in the event of brake slippage, if the load exceeds a predetermined tension on the line 4. The MVP system 6 is designed such that the brake will slip before any other point of failure is encountered, for example a snag in the line 4.
The line 4 preferably has a low drag coefficient to reduce recovery tension and to increase free fall speed of the payload. In a further preferred embodiment, the line 4 is an electro-mechanical cable that advantageously also allows the FFCPT to receive data in real-time and to be powered via the cable, avoiding the requirement to recover the FFCPT to change its internal batteries. A power management system provides power management and fail-safes.
Flagging arms located on the MVP 6 are used together with conventional CTD and SVP payloads, and removed when working with the FFCPT. As these are at the end of the MVP boom, traditional flagging arms are at a considerable height above the deck and accessed only by an elevated platform or ladder and the use of fall-restraint gear. The present flagging arm design uses a quick release/connect system that greatly diminishes the time required for the changeover.
The FFCPT payload has been integrated with the MVP 6 to permit the assessment of seabed 22 characteristics from a vessel 8 that is underway. Rather than applying the break means 18 to stop the descent of, for example, an SVP or CTD payload at a preset height above the seabed 22, the FFCPT
payload is intentionally allowed to impact the seabed 22. The integration of the FFCPT with the MVP 6 provides a means for obtaining seabed parameters with minimal impact on other operations. Relative to traditional methods of making in situ seabed measurements from a stationary vessel 8, such as cores or conventional cone penetrometers, this integration offers an order of magnitude increase or higher in the rate of seabed data collection.
The FFCPT makes direct measurements of geotechnical properties of the seabed 22. It incorporates the same scaling factors as a conventional pushed cone probe, but with a larger diameter to house the instrumentation. It is designed to free fall into the seabed 22 and to survive impacts with rock, if and when that happens.
The FFCPT is illustrated in Figure 3, to which reference is now made. The FFCPT is instrumented with power supply, electronics, optical and tail pressure sensors. It further comprises a nose cone 26 that houses geotechnical sensors, namely acceleration and dynamic pore pressure sensors, which measure acceleration and dynamic sediment pore pressure as a function of depth of penetration into the seabed 22. The FFCPT also records hydrostatic pressure, to monitor its descent velocity during free-fall, and comprises an optical backscatter sensor 30 for the detection of the water-sediment interface, or 'mudline', which is particularly helpful on high porosity fluid-mud seabeds.
Other optical sensors or modules may also optionally be included, such as, for example a digital camera, for visual detection and recording of ocean or seabed characteristics. When fitted with an optional electrical resistivity module, the FFCPT can also obtain geoacoustic, or small strain, properties of the seabed 22 by relating resistivity to porosity and other parameters. The FFCPT is advantageously designed in a modular fashion, to allow for addition and replacement of sensors as required.
The winch 10 is preferably a self contained electro-hydraulic winch.
The line puller 14 acts to prevent slack line 4 on the drum 12 when the FFCPT
impacts the seabed. The line puller 14 comprises a pair of traction rollers along which the line 4 travels off the drum 12 during descent of the probe 2 through the water body to the seabed 22. The traction rollers are mounted in a housing which is pivotally mounted about a horizontal pivot whose axis is generally perpendicular to a longitudinal axis of the vessel 8. Preferably the line puller 14 is directed astern of the vessel 8 during line 4 deployment, to ensure proper operation of the line puller 14 and to ensure better handle of pullout loads by the MVP 6 structure.
The line puller 14 is hydraulically driven and incorporates a clutch bearing to allow the traction rollers to freewheel during free fall yet be driven once tension is removed from the cable. The line puller 14 may remain in place in a deactivated mode for operations with alternate payloads such as, for example, sound velocity pressure (SVP) and CTD sensor payloads. A quick engage/disengage lever advantageously allows for quick engagement or disengagement of the line puller 14 as required by the particular payload to be used.
The winch 10 is powered by a suitable motor 24 that is interconnected with the drum 12 by a clutch, and provided with break means. The winch 10 can be secured to the deck in a variety of configurations. The MVP 6 is preferably mounted at the stern of the vessel 8 and deploys directly off the stern. It is also possible to deploy other equipment such as a sidescan sonar, sound sources, one or more streamers and magnetometers simultaneously with the MVP system 6 without disrupting its operation or the operation of neighbouring systems on the vessel 8.
For operation with the FFCPT, the present MVP system 6 includes supplemental bracing to the frame, a load cell to monitor pull-out loads, and modifications to the controller to prevent damage to the winch motor 24 in the event of brake slippage, if the load exceeds a predetermined tension on the line 4. The MVP system 6 is designed such that the brake will slip before any other point of failure is encountered, for example a snag in the line 4.
The line 4 preferably has a low drag coefficient to reduce recovery tension and to increase free fall speed of the payload. In a further preferred embodiment, the line 4 is an electro-mechanical cable that advantageously also allows the FFCPT to receive data in real-time and to be powered via the cable, avoiding the requirement to recover the FFCPT to change its internal batteries. A power management system provides power management and fail-safes.
Flagging arms located on the MVP 6 are used together with conventional CTD and SVP payloads, and removed when working with the FFCPT. As these are at the end of the MVP boom, traditional flagging arms are at a considerable height above the deck and accessed only by an elevated platform or ladder and the use of fall-restraint gear. The present flagging arm design uses a quick release/connect system that greatly diminishes the time required for the changeover.
The FFCPT payload has been integrated with the MVP 6 to permit the assessment of seabed 22 characteristics from a vessel 8 that is underway. Rather than applying the break means 18 to stop the descent of, for example, an SVP or CTD payload at a preset height above the seabed 22, the FFCPT
payload is intentionally allowed to impact the seabed 22. The integration of the FFCPT with the MVP 6 provides a means for obtaining seabed parameters with minimal impact on other operations. Relative to traditional methods of making in situ seabed measurements from a stationary vessel 8, such as cores or conventional cone penetrometers, this integration offers an order of magnitude increase or higher in the rate of seabed data collection.
The FFCPT makes direct measurements of geotechnical properties of the seabed 22. It incorporates the same scaling factors as a conventional pushed cone probe, but with a larger diameter to house the instrumentation. It is designed to free fall into the seabed 22 and to survive impacts with rock, if and when that happens.
The FFCPT is illustrated in Figure 3, to which reference is now made. The FFCPT is instrumented with power supply, electronics, optical and tail pressure sensors. It further comprises a nose cone 26 that houses geotechnical sensors, namely acceleration and dynamic pore pressure sensors, which measure acceleration and dynamic sediment pore pressure as a function of depth of penetration into the seabed 22. The FFCPT also records hydrostatic pressure, to monitor its descent velocity during free-fall, and comprises an optical backscatter sensor 30 for the detection of the water-sediment interface, or 'mudline', which is particularly helpful on high porosity fluid-mud seabeds.
Other optical sensors or modules may also optionally be included, such as, for example a digital camera, for visual detection and recording of ocean or seabed characteristics. When fitted with an optional electrical resistivity module, the FFCPT can also obtain geoacoustic, or small strain, properties of the seabed 22 by relating resistivity to porosity and other parameters. The FFCPT is advantageously designed in a modular fashion, to allow for addition and replacement of sensors as required.
The inclusion of a SVP sensor 28 in the tail of the FFCPT permits the acquisition of water column sound speed data during each deployment. This makes the data set more comprehensive for many applications, and also for hydrographic mapping systems that have a basic requirement for water column sound speed data. Preferably, a field swappable SV XchangeTM sound speed and water depth sensor is utilized, being attached to the FFCPT housing with a bulkhead connector that allows for ease of exchange of the SVP sensor 28 in the event that it requires calibration, repair or replacement.
The FFCPT provides two independent means of calculating the undrained shear strength. The first technique uses the acceleration to calculate the dynamic penetration resistance. The second technique uses the dynamic pore pressure measured by a sensor in the nose cone 26 of the FFCPT. The pressure signal passes through a porous hydrophilic ring to the pressure sensor inside a cavity in the nose cone 26 that is filled with a fluid. Such fluids are well known in the art and can be, for example, mineral oil.
Before conducting experiments, steps are taken to ensure that the cavity does not contain any air and that the pressure transducer has reached thermal equilibrium. Normalized values of the dynamic penetration resistance and dynamic pore pressure can then be used in a qualitative determination of the sediment behaviour type e.g. clay, silt, sand, or gravel by the direct application of geotechnical analysis methods and parametric-based correlations already long established in engineering practice and well known to those skilled in the art. When plotted against each other, these parameters yield an empirical measure of sediment type, based on the zone in which the data lie.
Through comparison of FFCPT results with independent measurements of sediment grain size and porosity for clay, silt, and sand seabeds, the inventors have confirmed that the FFCPT accurately characterizes a diverse range of marine sediments.
The FFCPT is advantageously fashioned in a hydrodynamic shape and is preferably made from stainless steel. The weight of the present FFCPT is approximately 60 kg although smaller and larger versions of the FFCPT have also been developed and tested with use in the present system.
A miniature, approximately 10 kg version has been designed and tested for operations from small boats in coastal environments. A larger, approximately 110 kg version has been designed and tested for deeper-water operations, for example by the seismic exploration industry, in which the additional weight allows the probe 2 to free fall to greater depths, dragging the line 4 with it.
The FFCPT is preferably equipped with tail fins 32 to orient the FFCPT's impact with the seabed 22 at a near-vertical angle. The tail fins 32 are more preferably designed to be asymmetric to prevent rotation of the FFCPT when it is being retrieved and towed behind the vessel 8 and thereby prevent potential damage to the line 4.
The FFCPT provides two independent means of calculating the undrained shear strength. The first technique uses the acceleration to calculate the dynamic penetration resistance. The second technique uses the dynamic pore pressure measured by a sensor in the nose cone 26 of the FFCPT. The pressure signal passes through a porous hydrophilic ring to the pressure sensor inside a cavity in the nose cone 26 that is filled with a fluid. Such fluids are well known in the art and can be, for example, mineral oil.
Before conducting experiments, steps are taken to ensure that the cavity does not contain any air and that the pressure transducer has reached thermal equilibrium. Normalized values of the dynamic penetration resistance and dynamic pore pressure can then be used in a qualitative determination of the sediment behaviour type e.g. clay, silt, sand, or gravel by the direct application of geotechnical analysis methods and parametric-based correlations already long established in engineering practice and well known to those skilled in the art. When plotted against each other, these parameters yield an empirical measure of sediment type, based on the zone in which the data lie.
Through comparison of FFCPT results with independent measurements of sediment grain size and porosity for clay, silt, and sand seabeds, the inventors have confirmed that the FFCPT accurately characterizes a diverse range of marine sediments.
The FFCPT is advantageously fashioned in a hydrodynamic shape and is preferably made from stainless steel. The weight of the present FFCPT is approximately 60 kg although smaller and larger versions of the FFCPT have also been developed and tested with use in the present system.
A miniature, approximately 10 kg version has been designed and tested for operations from small boats in coastal environments. A larger, approximately 110 kg version has been designed and tested for deeper-water operations, for example by the seismic exploration industry, in which the additional weight allows the probe 2 to free fall to greater depths, dragging the line 4 with it.
The FFCPT is preferably equipped with tail fins 32 to orient the FFCPT's impact with the seabed 22 at a near-vertical angle. The tail fins 32 are more preferably designed to be asymmetric to prevent rotation of the FFCPT when it is being retrieved and towed behind the vessel 8 and thereby prevent potential damage to the line 4.
An approximately two foot wire rope extension is located between the probe 2 and the line 4 to act as a standoff, preventing the line 4 from coiling around the tail fins 32.
The present system incorporates a real time data telemetry module. Real-time data telemetry allows monitoring of the depth of the FFCPT during the free-fall and recovery phases of the winch 10 operations. In terms of the FFCPT, the real time telemetry data from the impact of the FFCPT with the seabed 22 are available for processing immediately to determine bottom properties, and as quality assurance.
Data processing and display software has been written for the FFCPT to work with projects holding multiple drops of the FFCPT and storing the data in XML format.
Impact of the FFCPT with the seabed 22 can be determined by data collected from one or more sensors on the probe 2. Preferably data from two or more sensors are used, to provide redundancy and to prevent errors in impact measurement. Impact detection is preferably carried out by examining (a) changes in acceleration as detected by acceleration sensors, (b) changes in mudline, as detected by the optical backscatter sensors and (c) changes in both pressure and pore pressure.
In a particularly preferred embodiment, vehicle dynamics have been introduced to provide a means to confirm the instant of impact of the FFCPT with the seabed 22. The vehicle dynamics is used to correct offsets or errors in the accelerometer sensor data that may occur, for example, as a result of temperature or other effects, by reconciling the impact velocity measured by changes in water depth versus time with that from integration of the acceleration signals during penetration into the seabed 22.
The FFCPT software also has the ability to filter acceleration and pressure time series by means of digital filtering. When the FFCPT impacts harder materials such as shells or rocks, the FFCPT tends to resonate at the natural frequency of the probe 2. Since probe 2 vibrations are typically at much higher frequencies than the layered structure of the seabed 22, these vibrations can be successfully filtered out.
Surface powering involves DC to DC converters for safety to personnel operating the instrumentation, to prevent inadvertent damage to the FFCPT if the cable is damaged or removed, and to provide consistency with other commonly used payloads for the MVP 6.
Once the FFCPT has manually been deployed to the towed position just aft of the ship, it can be switched over to automatic mode. On command, the control algorithm allows the probe 2 to free fail behind the ship as the vessel 8 is underway.
While the probe 2 is falling, the winch 10 deploys the line 4. After a first short interval from when the probe 2 has impacted the seabed 22, the controller terminates the cast by deactivating the line puller 14 and activating the break means 18. This short interval can be between 2 to 5 seconds, to allow the probe 2 to collect the necessary seabed data. Impact with the seabed 22 is detected by the controller from the status of the FFCPT's high resolution data buffer.
As the vessel 8 continues moving, the line 4 becomes taut and the probe 2 is thus extracted from the seabed 22 and begins an immediate ascent toward the surface. The winch 10 is then automatically engaged to winch the probe 2 back to the towed position just behind the ship.
In a preferred embodiment, the winch 10 is engaged after a second, longer time delay from impact of the probe 2 with the seabed 22. Preferably, this second time interval is between 10 to 15 seconds.
Alternatively, if the vessel 8 is not moving for any reason, the winch 10 maybe engaged to both extract the probe 2 from the seabed 22 and also to retrieve the probe 2 back to the vessel 8.
Once the probe 2 is recovered to the towed position, the probe 2 can be deployed again, as soon as data transfer from the probe 2 to the MVP 6 is complete. Alternately, the probe 2 can be recovered and left in the towed position awaiting the command for the next deployment.
Preferably, a marker on the line 4, such as enlargement, in conjunction with a suitable detector may be used for detection of completion of spooling of the line 4 to the drum 12 during the retrieval stage to provide the necessary signal to disengage the clutch and activate the break means 18 for termination of line 4 retrieval. Alternatively, line metering means located on the MVP 6 monitors the line 4 as it is paid out or winched in, and may be utilized to provide the necessary termination signal, or may optionally be used as a back-up system to the line marker.
The probe 2 descent rate is determined by its drag and the drag of the line 4 pulled behind it. An algorithm has been developed to allow for drag correction to account for the drag force on the line 4 in the calculation of seabed properties.
Numerous scientific and commercial applications for the MVP 6 with an FFCPT as the payload are also foreseen, for example: ground-truth for acoustic seabed classification systems, pipeline and cable route surveys, benthic habitat surveys, and dredge site surveys.
Examples The following examples serve merely to illustrate aspects of the present invention and do not limit the scope thereof in any way. The examples are based on field trials that were reported by the inventors in the article "The Integration of the Free Fall Cone Penetrometer (FFCPT) with the Moving Vessel Profiler (MVP) for the Rapid Assessment of Seabed Characteristics;" International Hydrographic Review; Vol. 7, No. 3; pages 45-53; October 2006.
The present system incorporates a real time data telemetry module. Real-time data telemetry allows monitoring of the depth of the FFCPT during the free-fall and recovery phases of the winch 10 operations. In terms of the FFCPT, the real time telemetry data from the impact of the FFCPT with the seabed 22 are available for processing immediately to determine bottom properties, and as quality assurance.
Data processing and display software has been written for the FFCPT to work with projects holding multiple drops of the FFCPT and storing the data in XML format.
Impact of the FFCPT with the seabed 22 can be determined by data collected from one or more sensors on the probe 2. Preferably data from two or more sensors are used, to provide redundancy and to prevent errors in impact measurement. Impact detection is preferably carried out by examining (a) changes in acceleration as detected by acceleration sensors, (b) changes in mudline, as detected by the optical backscatter sensors and (c) changes in both pressure and pore pressure.
In a particularly preferred embodiment, vehicle dynamics have been introduced to provide a means to confirm the instant of impact of the FFCPT with the seabed 22. The vehicle dynamics is used to correct offsets or errors in the accelerometer sensor data that may occur, for example, as a result of temperature or other effects, by reconciling the impact velocity measured by changes in water depth versus time with that from integration of the acceleration signals during penetration into the seabed 22.
The FFCPT software also has the ability to filter acceleration and pressure time series by means of digital filtering. When the FFCPT impacts harder materials such as shells or rocks, the FFCPT tends to resonate at the natural frequency of the probe 2. Since probe 2 vibrations are typically at much higher frequencies than the layered structure of the seabed 22, these vibrations can be successfully filtered out.
Surface powering involves DC to DC converters for safety to personnel operating the instrumentation, to prevent inadvertent damage to the FFCPT if the cable is damaged or removed, and to provide consistency with other commonly used payloads for the MVP 6.
Once the FFCPT has manually been deployed to the towed position just aft of the ship, it can be switched over to automatic mode. On command, the control algorithm allows the probe 2 to free fail behind the ship as the vessel 8 is underway.
While the probe 2 is falling, the winch 10 deploys the line 4. After a first short interval from when the probe 2 has impacted the seabed 22, the controller terminates the cast by deactivating the line puller 14 and activating the break means 18. This short interval can be between 2 to 5 seconds, to allow the probe 2 to collect the necessary seabed data. Impact with the seabed 22 is detected by the controller from the status of the FFCPT's high resolution data buffer.
As the vessel 8 continues moving, the line 4 becomes taut and the probe 2 is thus extracted from the seabed 22 and begins an immediate ascent toward the surface. The winch 10 is then automatically engaged to winch the probe 2 back to the towed position just behind the ship.
In a preferred embodiment, the winch 10 is engaged after a second, longer time delay from impact of the probe 2 with the seabed 22. Preferably, this second time interval is between 10 to 15 seconds.
Alternatively, if the vessel 8 is not moving for any reason, the winch 10 maybe engaged to both extract the probe 2 from the seabed 22 and also to retrieve the probe 2 back to the vessel 8.
Once the probe 2 is recovered to the towed position, the probe 2 can be deployed again, as soon as data transfer from the probe 2 to the MVP 6 is complete. Alternately, the probe 2 can be recovered and left in the towed position awaiting the command for the next deployment.
Preferably, a marker on the line 4, such as enlargement, in conjunction with a suitable detector may be used for detection of completion of spooling of the line 4 to the drum 12 during the retrieval stage to provide the necessary signal to disengage the clutch and activate the break means 18 for termination of line 4 retrieval. Alternatively, line metering means located on the MVP 6 monitors the line 4 as it is paid out or winched in, and may be utilized to provide the necessary termination signal, or may optionally be used as a back-up system to the line marker.
The probe 2 descent rate is determined by its drag and the drag of the line 4 pulled behind it. An algorithm has been developed to allow for drag correction to account for the drag force on the line 4 in the calculation of seabed properties.
Numerous scientific and commercial applications for the MVP 6 with an FFCPT as the payload are also foreseen, for example: ground-truth for acoustic seabed classification systems, pipeline and cable route surveys, benthic habitat surveys, and dredge site surveys.
Examples The following examples serve merely to illustrate aspects of the present invention and do not limit the scope thereof in any way. The examples are based on field trials that were reported by the inventors in the article "The Integration of the Free Fall Cone Penetrometer (FFCPT) with the Moving Vessel Profiler (MVP) for the Rapid Assessment of Seabed Characteristics;" International Hydrographic Review; Vol. 7, No. 3; pages 45-53; October 2006.
Example 1:
The FFCPT was deployed from MVP winch systems installed on the CFAV Quest and CCGS Matthew.
Seabed and SVP data have been collected from these vessels while underway in Bedford Basin, the approaches to Halifax Harbour, and in St. Margaret's Bay at speeds ranging from 4 to 8 knots. Four sites in St. Margaret's Bay, Nova Scotia (Table 1) were selected for underway drop testing based on the diversity of sediment types and expected penetration of the FFCPT. Sites 1-3 are in an area with extensive survey information: four swath bathymetry systems (Atlas Hydrosweep MD50, Simrad EM3000 and EM710, and Reson 8125); sidescan sonar (Klein 5500); sediment cores with grain size analysis and multi-sensor core logging of physical properties (porosity and compressional wave sound speed); stereo photographs; high resolution seismic profiles (EdgeTech X-Star chirp system and GeoAcoustics Boomer impulsive system); scientific and commercial seabed classification systems - grab samples and sediment probe drops (FFCPT, STING, and XBP).
Site Latitude Longitude Anticipated Penetration (m) Operational Sediment Type Depth (m) 1 44236.958'N 063959.794'W 0.5 40 Sand and gravel 2 44936.601'N 064200.629'W 1 39 Sand 3 44936.436'N 064900.557'W 1.5 43 Sand over silt & clay 4 44934.972'N 063959.244'W 2.5 58 Clay Table 1: Underway Drop Testing Site Conditions Example 2: Underway drop testing Underway drop testing progressed from Sites 1 through 4, with the expectation that pull-out loads would increase at the progressively softer sites as the depth of FFCPT
penetration increases. To eliminate the possibility of damaging the electro- mechanical cable on the MVP
during the initial tests conducted aboard CFAV Quest, the electro-mechanical cable was replaced with a mechanical rope (01/4", 5000lbs break strength). For the FFCPT transects aboard CCGS Matthew, the standard electromechanical cable for MVP operations was used and the 'slow' data from the FFCPT, decimated to 1 Hz, was telemetered up the tow cable. To minimize the risk of damaging equipment, the initial underway drops at Sites 1-4 were conducted with a 'dummy' probe whose geometric and mass properties are identical to the FFCPT. Underway drops with the actual FFCPT
were then conducted at speeds of 6, 5, 4, and 3.5 knots.
An objective of the underway drop testing was to determine if that the FFCPT
could be extracted from the seabed regardless of seabed type and for a reasonable range of vessel speeds. Measured peak pull-out loads at Sites 1 to 4 were less than 275 kg, and well within the capacity of the brake means on the cable drum of the MVP, as seen in Figure 5. The measured pull-out forces in Newtons have been normalized by the acceleration due to gravity to provide pull-out 'loads' in units of kilograms.
There was some unexpected behaviour as the pull-out loads at Site 2 were consistently higher than Sites 3 and 4. A detailed examination of the load cell time series has revealed that the extraction from the softer sites 3 and 4 is more gradual, approximately 4 to 5 second duration, whereas the extraction from harder sites 1 and 2 is faster, approximately 2 to 3 second duration. There is some evidence that the pull-out load decreases as vessel speed increases, again as seen in Figure 5 due to the near-vertical force exerted by the catenary that the line forms in the water column, though this effect is not as pronounced as expected. Another metric to examine underway drop behaviour is the impact velocity of the FFCPT
when it strikes the seabed, as seen in Figure 6. The impact velocity may be determined by measuring the rate of change of the hydrostatic pressure and/or by integration of accelerometer signals during the impact event. In the present case, there appears to be a trend, in three of the four sites for the impact velocity to decrease as vessel speed increases. It is suspected that this is a consequence of additional line being in the water at higher vessel speeds. This explanation would be consistent with an analysis of FFCPT drops from a stationary vessel that indicates that the impact velocity decreases as water depth, and hence line drag increases. The depth of penetration of the FFCPT into the seabed depends upon the site, from approximately 250 cm for a soft clay seabed, such as Site 4 as seen in Figure 7, to less than 50 cm for a sand and gravel seabed as seen in Site 1 in Figure 7. The depth of penetration is quite consistent at all vessel speeds, again as illustrated in Figure 7, as are the sediment behaviour types in the respective pseudo-cores (not shown). These observations suggest that the performance of the FFCPT
does not depend on vessel speed or impact velocity.
Example 3: Multiple underway drop survey transects Having established confidence that the FFCPT could be deployed on a wide range of seabed types at different vessel speeds, underway testing progressed to conducting a series of drops in succession as the vessel maintained course and speed. Multiple drop survey transects were conducted by CFAV Quest passing through Sites 1 and 2 at 4 and 6 knots. Subsequently, multiple drop survey transects were conducted by CCGS Matthew in Halifax Harbour and its approaches, and in St.
Margaret's Bay. At the latter location, CCGS Matthew repeated the CFAV Quest transects and then progressed along four additional transects designed to pass through Sites 2 and 3 and areas identified as being distinct sediment classes, based on the angular backscatter response of swath bathymetry data. The cycle time per drop is the approximate time required for a complete drop cycle consisting of free-fall, impact, and winch back in 50 m of water, and also the time needed to write data collected by the FFCPT to an internal flash memory. The survey transects conducted with CFAV Quest used a time interval of 90 s between successive drops (180 m at a vessel speed of 4 knots); those conducted from CCGS Matthew used a time interval of 75 s (with probe re-arming confirmed by monitoring the 'slow' data telemetry).
The various above examples compared the relationship between acoustic techniques for seabed classification and in situ measurements that are made by the FFCPT. It is noted by the inventors that the acoustic techniques have the advantage of providing broad area coverage for REA applications and they are generally able to successfully distinguish regions of the seabed that are distinct from one another.
However, they are generally unable to indicate the physical properties of the seabed that are responsible for the distinct regions.
Figure 8 is a combination of SVP profiles and pseudo-cores measured by the FFCPT, a sub-bottom profiler image, and seabed classification from EM3000 swath bathymetry angular backscatter analysis.
FFCPT drops in acoustic classes 1, 6, and 7 generally have limited penetration (less than 0.5 m) and report seabed compositions of gravel and sand. This is consistent with the grain size information available from grab samples. The FFCPT indicates that Class 1 has a thin layer of sandy-silt. FFCPT drops in Class 5 have deeper penetration (1 to 1.5 m) and indicate a sandy-silt to silty-sand composition.
This detailed description of the present devices and methods is used to illustrate certain embodiments of the present invention. It will be apparent to a person skilled in the art that various modifications can be made and that various alternate embodiments can be utilized without departing from the scope of the present application, which is limited only by the appended claims.
The FFCPT was deployed from MVP winch systems installed on the CFAV Quest and CCGS Matthew.
Seabed and SVP data have been collected from these vessels while underway in Bedford Basin, the approaches to Halifax Harbour, and in St. Margaret's Bay at speeds ranging from 4 to 8 knots. Four sites in St. Margaret's Bay, Nova Scotia (Table 1) were selected for underway drop testing based on the diversity of sediment types and expected penetration of the FFCPT. Sites 1-3 are in an area with extensive survey information: four swath bathymetry systems (Atlas Hydrosweep MD50, Simrad EM3000 and EM710, and Reson 8125); sidescan sonar (Klein 5500); sediment cores with grain size analysis and multi-sensor core logging of physical properties (porosity and compressional wave sound speed); stereo photographs; high resolution seismic profiles (EdgeTech X-Star chirp system and GeoAcoustics Boomer impulsive system); scientific and commercial seabed classification systems - grab samples and sediment probe drops (FFCPT, STING, and XBP).
Site Latitude Longitude Anticipated Penetration (m) Operational Sediment Type Depth (m) 1 44236.958'N 063959.794'W 0.5 40 Sand and gravel 2 44936.601'N 064200.629'W 1 39 Sand 3 44936.436'N 064900.557'W 1.5 43 Sand over silt & clay 4 44934.972'N 063959.244'W 2.5 58 Clay Table 1: Underway Drop Testing Site Conditions Example 2: Underway drop testing Underway drop testing progressed from Sites 1 through 4, with the expectation that pull-out loads would increase at the progressively softer sites as the depth of FFCPT
penetration increases. To eliminate the possibility of damaging the electro- mechanical cable on the MVP
during the initial tests conducted aboard CFAV Quest, the electro-mechanical cable was replaced with a mechanical rope (01/4", 5000lbs break strength). For the FFCPT transects aboard CCGS Matthew, the standard electromechanical cable for MVP operations was used and the 'slow' data from the FFCPT, decimated to 1 Hz, was telemetered up the tow cable. To minimize the risk of damaging equipment, the initial underway drops at Sites 1-4 were conducted with a 'dummy' probe whose geometric and mass properties are identical to the FFCPT. Underway drops with the actual FFCPT
were then conducted at speeds of 6, 5, 4, and 3.5 knots.
An objective of the underway drop testing was to determine if that the FFCPT
could be extracted from the seabed regardless of seabed type and for a reasonable range of vessel speeds. Measured peak pull-out loads at Sites 1 to 4 were less than 275 kg, and well within the capacity of the brake means on the cable drum of the MVP, as seen in Figure 5. The measured pull-out forces in Newtons have been normalized by the acceleration due to gravity to provide pull-out 'loads' in units of kilograms.
There was some unexpected behaviour as the pull-out loads at Site 2 were consistently higher than Sites 3 and 4. A detailed examination of the load cell time series has revealed that the extraction from the softer sites 3 and 4 is more gradual, approximately 4 to 5 second duration, whereas the extraction from harder sites 1 and 2 is faster, approximately 2 to 3 second duration. There is some evidence that the pull-out load decreases as vessel speed increases, again as seen in Figure 5 due to the near-vertical force exerted by the catenary that the line forms in the water column, though this effect is not as pronounced as expected. Another metric to examine underway drop behaviour is the impact velocity of the FFCPT
when it strikes the seabed, as seen in Figure 6. The impact velocity may be determined by measuring the rate of change of the hydrostatic pressure and/or by integration of accelerometer signals during the impact event. In the present case, there appears to be a trend, in three of the four sites for the impact velocity to decrease as vessel speed increases. It is suspected that this is a consequence of additional line being in the water at higher vessel speeds. This explanation would be consistent with an analysis of FFCPT drops from a stationary vessel that indicates that the impact velocity decreases as water depth, and hence line drag increases. The depth of penetration of the FFCPT into the seabed depends upon the site, from approximately 250 cm for a soft clay seabed, such as Site 4 as seen in Figure 7, to less than 50 cm for a sand and gravel seabed as seen in Site 1 in Figure 7. The depth of penetration is quite consistent at all vessel speeds, again as illustrated in Figure 7, as are the sediment behaviour types in the respective pseudo-cores (not shown). These observations suggest that the performance of the FFCPT
does not depend on vessel speed or impact velocity.
Example 3: Multiple underway drop survey transects Having established confidence that the FFCPT could be deployed on a wide range of seabed types at different vessel speeds, underway testing progressed to conducting a series of drops in succession as the vessel maintained course and speed. Multiple drop survey transects were conducted by CFAV Quest passing through Sites 1 and 2 at 4 and 6 knots. Subsequently, multiple drop survey transects were conducted by CCGS Matthew in Halifax Harbour and its approaches, and in St.
Margaret's Bay. At the latter location, CCGS Matthew repeated the CFAV Quest transects and then progressed along four additional transects designed to pass through Sites 2 and 3 and areas identified as being distinct sediment classes, based on the angular backscatter response of swath bathymetry data. The cycle time per drop is the approximate time required for a complete drop cycle consisting of free-fall, impact, and winch back in 50 m of water, and also the time needed to write data collected by the FFCPT to an internal flash memory. The survey transects conducted with CFAV Quest used a time interval of 90 s between successive drops (180 m at a vessel speed of 4 knots); those conducted from CCGS Matthew used a time interval of 75 s (with probe re-arming confirmed by monitoring the 'slow' data telemetry).
The various above examples compared the relationship between acoustic techniques for seabed classification and in situ measurements that are made by the FFCPT. It is noted by the inventors that the acoustic techniques have the advantage of providing broad area coverage for REA applications and they are generally able to successfully distinguish regions of the seabed that are distinct from one another.
However, they are generally unable to indicate the physical properties of the seabed that are responsible for the distinct regions.
Figure 8 is a combination of SVP profiles and pseudo-cores measured by the FFCPT, a sub-bottom profiler image, and seabed classification from EM3000 swath bathymetry angular backscatter analysis.
FFCPT drops in acoustic classes 1, 6, and 7 generally have limited penetration (less than 0.5 m) and report seabed compositions of gravel and sand. This is consistent with the grain size information available from grab samples. The FFCPT indicates that Class 1 has a thin layer of sandy-silt. FFCPT drops in Class 5 have deeper penetration (1 to 1.5 m) and indicate a sandy-silt to silty-sand composition.
This detailed description of the present devices and methods is used to illustrate certain embodiments of the present invention. It will be apparent to a person skilled in the art that various modifications can be made and that various alternate embodiments can be utilized without departing from the scope of the present application, which is limited only by the appended claims.
Claims (30)
1. A system for the automated collection of ocean and seabed data from a moving vessel, comprising:
a. a hydrodynamically streamlined, modular free fall probe for collecting data from a water body and from a seabed;
b. a winch system including a drum for storing a line connecting the probe with the vessel;
c. a line puller, disengagebly connected to the winch system, for maintaining tension on the drum when the probe impacts the seabed; and d. a controller for controlling rotation of the drum for retrieval of the probe.
a. a hydrodynamically streamlined, modular free fall probe for collecting data from a water body and from a seabed;
b. a winch system including a drum for storing a line connecting the probe with the vessel;
c. a line puller, disengagebly connected to the winch system, for maintaining tension on the drum when the probe impacts the seabed; and d. a controller for controlling rotation of the drum for retrieval of the probe.
2. The system of claim 1 wherein the probe comprises one or more data collecting means.
3. The system of claim 2 wherein the data collecting means comprise sound-velocity-pressure sensors, optical backscatter sensors, tail pressure sensors, dynamic pore pressure sensors, acceleration sensors, hydrostatic pressure sensors, optical sensors and electrical resistivity modules.
4. The system of claim 3, wherein the sound-velocity-pressure sensor is field swappable and comprises bulkhead connectors to connect and disconnect to the probe.
5. The system of claim 1 wherein the probe comprises tail fins to orient the probe in a generally-vertical direction as it impacts the seabed.
6. The system of claim 5 wherein the tail fins are asymmetric to prevent rotation of the probe when the probe is retrieved or towed behind the vessel.
7. The system of claim 1 wherein the probe is sized for operations from small boats in coastal environments.
8. The system of claim 1 wherein the probe is sized for deep-water operations.
9. The system of claim 1 further comprising brake means associated with the drum and activated by the controller upon impact of the probe with the seabed, to terminate line deployment.
10. The system of claim 9 wherein impact of the probe with the seabed is detected by one or more sensors on the probe and relayed to the controller.
11. The system of claim 10 wherein impact of the probe with the seabed is detected by two or more sensors on the probe, to achieve redundancy and reduce errors in impact detection.
12. The system of claim 11 wherein impact of the probe with the seabed is detected by the acceleration sensors, the optical backscatter sensors and the dynamic pore pressure sensors.
13. The system of claim 1 wherein the winch system further comprises quick connect flagging arms that are connected for use of the winch system with a conductivity-temperature-depth payload and disconnected for use of the winch system with the free fall probe.
14. The system of claim 1 wherein the line puller is disengagebly connected to the winch system by means of a quick engage lever.
15. The system of claim 1 wherein the winch system further comprises a load cell to monitor loads encountered as the probe is extracted out of the seabed.
16. The system of claim 1 wherein the probe and the winch system further comprise real-time data telemetry means to enable real-time depth monitoring of the probe during descent and retrieval, and to enable immediate data collection at the time of the probe contact with the seabed.
17. The system of claim 1 wherein the line is an electro-mechanical cable that supplies power to the probe.
18. The system of claim 1 wherein the probe further comprises data processing and display means for processing data collected from multiple probe descents and storing the data in XML format.
19. The system of claim 1 wherein probe further comprises data filtering means of filtering noise from data received by the probe.
20. The system of claim 19 wherein the data filtering means acts to filter vibration noise created by impact of the probe with hard materials on or in the seabed.
21. A method of collecting ocean and seabed data from a moving vessel, said method comprising the steps of:
a. deploying a probe along a line, from a moving vessel, wherein said line is fed from a drum via a winch to the probe;
b. allowing the probe to free fall through a water body until it impacts a seabed c. engaging a line puller on the winch to maintain tension on the drum during free fall and at impact;
d. terminating line feed from the drum and disengaging the line puller after impact of the probe with the seabed;
e. extracting the probe from the seabed by action of the moving vessel tightening and pulling the line;
f. winching back the line to retrieve the probe through the water body and back to the vessel; and g. maintaining the probe in a towed position for further deployment.
a. deploying a probe along a line, from a moving vessel, wherein said line is fed from a drum via a winch to the probe;
b. allowing the probe to free fall through a water body until it impacts a seabed c. engaging a line puller on the winch to maintain tension on the drum during free fall and at impact;
d. terminating line feed from the drum and disengaging the line puller after impact of the probe with the seabed;
e. extracting the probe from the seabed by action of the moving vessel tightening and pulling the line;
f. winching back the line to retrieve the probe through the water body and back to the vessel; and g. maintaining the probe in a towed position for further deployment.
22. The method of claim 21, wherein steps a. to g. are repeated one or more times to allow for multiple deployments and collection of multiple sets of oceanographic data.
23. The method of claim 21, wherein impact of the probe with the seabed is detected by one or more sensors on the probe and conducted to a controller on the vessel.
24. The method of claim 23, wherein impact of the probe with the seabed is detected by two sensors on the probe, to achieve redundancy and reduce errors in impact detection.
25. The method of claim 24, wherein impact of the probe with the seabed is detected by the acceleration sensors, the optical backscatter sensors and the dynamic pore pressure sensors.
26. The method of claim 25, wherein the line feed is terminated by the controller by applying brake means to the winch.
27. The method of claim 26, wherein there is a first time delay between the probe impacting the seabed and terminating the line feed and disengaging the line puller.
28. The method of claim 27, wherein the first time delay is 2 to 5 seconds.
29. The method of claim 21, when there is a second time delay between the probe impacting the seabed and winching the line back.
30. The method of claim 29, wherein the second time delay is 10 to 15 seconds.
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CA 2689489 CA2689489A1 (en) | 2009-12-31 | 2009-12-31 | Free fall cone penetrometer test |
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CA 2689489 CA2689489A1 (en) | 2009-12-31 | 2009-12-31 | Free fall cone penetrometer test |
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