U.S. patent application number 15/542176 was filed with the patent office on 2018-09-20 for methods and systems for dredging.
The applicant listed for this patent is DOTOCEAN NV. Invention is credited to Sebastien DEPREZ, Koen GEIRNAERT, Peter STAELENS.
Application Number | 20180266072 15/542176 |
Document ID | / |
Family ID | 55071050 |
Filed Date | 2018-09-20 |
United States Patent
Application |
20180266072 |
Kind Code |
A1 |
GEIRNAERT; Koen ; et
al. |
September 20, 2018 |
Methods and Systems for Dredging
Abstract
The invention relates to a dredging method for dredging a
navigation channel for guaranteeing a nautical depth of a
navigation channel. The method comprises performing agitation for
mobilizing sediment and displacing the mobilized sediment to a
collector which is embedded in the bottom of the navigation
channel, the collector being a trench in the navigation channel
wherein the trench has, when not being filled with sediment, a
bottom level positioned substantially deeper than the nautical
depth of the navigation channel. The method also comprises, in a
step different from said performing agitation dredging, after
solidification of the sediment collected in the collector, removing
the solidified sediment from the collector so that the collector
again has a bottom level positioned substantially deeper than the
nautical depth of the navigation channel.
Inventors: |
GEIRNAERT; Koen; (Drongen,
BE) ; DEPREZ; Sebastien; (Houthulst, BE) ;
STAELENS; Peter; (Brugge, BE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DOTOCEAN NV |
Brugge |
|
BE |
|
|
Family ID: |
55071050 |
Appl. No.: |
15/542176 |
Filed: |
January 7, 2016 |
PCT Filed: |
January 7, 2016 |
PCT NO: |
PCT/EP2016/050240 |
371 Date: |
July 7, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02A 10/00 20180101;
E02F 5/287 20130101; E02B 3/023 20130101; E02F 3/9206 20130101;
E02F 3/907 20130101; Y02A 10/28 20180101 |
International
Class: |
E02F 3/92 20060101
E02F003/92; E02B 3/02 20060101 E02B003/02; E02F 3/90 20060101
E02F003/90; E02F 5/28 20060101 E02F005/28 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 7, 2015 |
GB |
1500220.7 |
Claims
1-30. (canceled)
31. A method for dredging a navigation channel for guaranteeing a
nautical depth of a navigation channel, the method comprising
performing agitation for mobilizing sediment and displacing the
mobilized sediment to a collector which is embedded in the bottom
of the navigation channel, the collector being a trench in the
navigation channel wherein the trench has, when not being filled
with sediment, a bottom level positioned substantially deeper than
the nautical depth of the navigation channel, in a step different
from said performing agitation dredging, after solidification of
the sediment collected in the collector, removing the solidified
sediment from the collector so that the collector again has a
bottom level positioned substantially deeper than the nautical
depth of the navigation channel.
32. A method according to claim 31, wherein said displacing the
mobilized sediment is performed by water injection.
33. A method according to claim 31, wherein said displacing the
mobilized sediment is performed by plough dredging.
34. A method according to claim 31, wherein, prior to said
agitation dredging, the method comprises forming the trench in the
navigation channel.
35. A method according to claim 31, wherein said performing
agitation comprises agitation dredging through water injection
dredging using a water injection dredger or wherein said performing
agitation comprises agitation dredging through water injection
dredging using a plough dredger.
36. A method according to claim 31, wherein said performing
agitation comprises using a water injection system installed at or
near the nautical bottom.
37. A method according to claim 36, wherein said performing
agitation comprises performing agitation through a water injection
system being at least partly integrated in mats for scour
protecting or mats forming the wall of the collector.
38. A method according to claim 31, wherein said removing sediment
from the collector comprises removing sediment with a jumbo hopper
dredger.
39. A method according to claim 31, wherein said removing sediment
from the collector comprises removing sediment by pumping through a
stationary or mobile pumping system.
40. A method according to claim 31, wherein the method comprises,
prior to said performing agitation for mobilizing sediment,
determining any of soil strength and/or density and determining
based thereon any or more of the dredging power, the dredging
effort, the water injection volume to erode, liquefy or mobilise
the underwater sediment layer.
41. A method according to claim 31, wherein the method comprises
predicting when the sediment needs to be moved to the
collector.
42. A method according to claim 31, wherein the method comprises
predicting when the sediment needs to be removed from the collector
for guaranteeing a predetermined nautical depth.
43. A method according to claim 31, wherein the method comprises
predicting when the sediment needs to be removed from the
collector.
44. A method for assisting according to claim 43, wherein said
predicting is based on an estimate of the amount of mobilized
sediment collected in the collector or the degree of consolidation
of the sediment in the collector.
45. A water injection platform for dredging a navigation channel
for guaranteeing a nautical depth of a navigation channel, the
platform comprising an agitation system for performing agitation
for mobilizing sediment and displacing the mobilized sediment to a
collector which is embedded in the bottom of the navigation
channel, the collector being a trench in the navigation channel
wherein the trench has, when not being filled with sediment, a
bottom level positioned substantially deeper than the nautical
depth of the navigation channel.
46. A water injection platform according to claim 45, the platform
further comprising the collector for collecting the mobilized mud
and/or comprising the platform comprising a dredging pumping system
for pumping the liquefied sediment and/or wherein the collector is
a trench made in the seabed of the navigation channel and/or
wherein the agitation system is based on a floating platform or
vessel.
47. A water injection platform according to claim 45, wherein the
water injection system comprises a submersed system with mounted or
integrated nozzles and/or comprises one or more mats where
injectors are integrated and connected with a water injection pump
and/or wherein the mat is a mat suitable for scour protection or as
surface or wall to shape a collector and/or wherein the collector
is formed and shaped in the soil or in the mud and/or wherein the
collector is made out of material like concrete or steel.
48. A water injection platform according to claim 45, wherein the
water injection platform furthermore comprises a monitor system for
measuring soil strength and density for determining the dredging
power, the dredging effort in hours and the water injection volume
to erode, liquefy and mobilise an underwater sediment layer and/or
wherein the water injection platform comprises a monitor system for
predicting when the sediment needs to be removed from the collector
for guaranteeing a predetermined nautical bottom level and/or
wherein the water injection platform comprises a pumping station on
a dredging ship for pumping the sediment from the collector towards
a dredging ship or a stationary pumping station for pumping the
sediment from the collector towards a pipe line to relocate the
sediment to a dumping or treatment site where the sediment is
permanently stored or where it is re-suspended and carried away
from the area temporally or permanently.
49. A monitor system for assisting a dredging process in a
navigation channel, the dredging process comprising a step of
performing agitation for mobilizing sediment and displacing the
mobilized sediment to a collector being a trench in the navigation
channel wherein the trench has, when not being filled with
sediment, a bottom level positioned substantially deeper than the
nautical depth of the navigation channel and a separate step of,
after solidification of the sediment collected in the collector,
removing the solidified sediment from the collector so that the
collector again has a bottom level positioned substantially deeper
than the nautical depth of the navigation channel, the monitoring
system being adapted for determining any of soil strength and/or
density and determining based thereon any or more of the dredging
power, the dredging effort, the water injection volume to erode,
liquefy or mobilise the underwater sediment layer, and/or for
predicting when the sediment needs to be removed from the collector
for guaranteeing a predetermined nautical bottom level.
Description
FIELD OF THE INVENTION
[0001] The invention relates to the field of agitation dredging in
general and in particular water injection dredging. The present
invention relates to methods and systems for performing,
monitoring, controlling and/or optimizing the agitation dredging
process to liquefy, erode and displace sediment in a port or
waterway towards a central collector and optionally remove the
sediment with alternative methods from the collector. This may
optimize the dredging effort.
BACKGROUND OF THE INVENTION
[0002] Transport over water is becoming more and more important in
a globalized economy. This results in more and bigger vessels and
ships that need to enter harbors and inland waterways. Therefore
the navigability of harbors and waterways need to be guaranteed.
Deepening and widening of waterways and harbors is a constant
activity done by authorities to ensure ships can pass and navigate.
In most of the ports and waterways there is also continuous inflow
of sediments and therefore maintenance dredging is necessary. To
determine when and how much there needs to be dredged the
underwater sediment and mud layers must be monitored and analyzed.
Classically the maintenance dredging work is performed by trailer
suction hopper dredgers, but alternatively the same result can be
achieved by WID (water injection dredging) dredgers in combination
with supportive techniques.
[0003] If a similar result can be achieved by agitation dredging
like by WID dredgers the resulting effort and cost can be
reduced.
SUMMARY OF THE INVENTION
[0004] It is an object of the present invention to provide a method
for dredging, e.g. agitation dredging.
[0005] It is an advantage of at least some embodiments of the
present invention in that they provide in a combined method of an
agitation dredging technique and a sediment collector, a water
injection platform system, a method or system for assisting in such
a dredging method or a mat that can be used in such a dredging
method.
[0006] The above object can be obtained using methods, systems or
products according to embodiments of the present invention.
[0007] In one aspect, the present invention relates to a method for
dredging a navigation channel for guaranteeing a nautical depth of
a navigation channel, the method comprising
[0008] performing agitation for mobilizing sediment and displacing
the mobilized sediment to a collector which is embedded in the
bottom of the navigation channel, the collector being a trench in
the navigation channel wherein the trench has, when not being
filled with sediment, a bottom level positioned substantially
deeper than the nautical depth of the navigation channel,
[0009] in a step different from said performing agitation dredging,
after solidification of the sediment collected in the collector,
removing the solidified sediment from the collector so that the
collector again has a bottom level positioned substantially deeper
than the nautical depth of the navigation channel.
[0010] It is an advantage of embodiments of the present invention
that the action of mobilizing and the action of removing collected
sediment from the navigation channel is decoupled, allowing to use
different means for the mobilizing and the removing.
[0011] It is an advantage of embodiments of the present invention
that the action of removing sediment from the collector can be
performed less frequent, e.g. using a larger dredger, by temporary
storing sediment in a local collector.
[0012] Displacing the mobilized sediment may be performed by water
injection. The displacement of the mobilized sediment can be over a
distance of up to several tens of meter. In a special case the
action of the movement of sediment can be assisted by a plough
dredger. The plough dredger can assist in driving sediment to the
collector.
[0013] The method may comprise, prior to said agitation dredging,
forming the trench in the navigation channel. It is an advantage of
embodiments of the present invention that a natural collector can
be used. Alternatively, an artificial collector, such as for
example made of concrete walls can be created in the navigation
channel having a floor positioned substantially below the nautical
depth.
[0014] Said performing agitation may comprise agitation dredging
through water injection dredging using a water injection
dredger.
[0015] Said performing agitation may comprise using a water
injection system installed at or near the nautical bottom.
[0016] Said performing agitation may comprise performing agitation
through a water injection system being at least partly integrated
in mats for scour protecting or mats forming the wall of the
collector.
[0017] Said removing sediment from the collector may comprise
removing sediment with a jumbo hopper dredger. Said removing
sediment from the collector may comprise removing sediment by
pumping through a stationary or mobile pumping system.
[0018] The method may comprise, prior to said performing agitation
for mobilizing sediment, determining any of soil strength and/or
density and determining based thereon any or more of the dredging
power, the dredging effort, the water injection volume to erode,
liquefy or mobilise the underwater sediment layer.
[0019] The method may comprise predicting when the sediment needs
to be removed from the collector for guaranteeing a predetermined
nautical depth.
[0020] The present invention also relates to a method for assisting
a dredging process in a navigation channel, the dredging process
comprising a step of performing agitation for mobilizing sediment
and displacing the mobilized sediment to a collector in the
navigation channel and a separate step of removing sediment from
the collector, wherein the method for assisting comprises
[0021] determining any of soil strength and/or density and
determining based thereon any or more of the dredging power, the
dredging effort, the water injection volume to erode, liquefy or
mobilise the underwater sediment layer, and/or
[0022] predicting when the sediment needs to be removed from the
collector. Said predicting may be based on an estimate of the
amount of mobilized sediment collected in the collector.
Determining dredging parameters or determining when the sediment
needs to be removed may be determined based on the nautical depth,
a consolidation level of the sediment, the amount of sediment in
the collector, . . . etc.
[0023] The present invention also relates to a water injection
platform for dredging a navigation channel for guaranteeing a
nautical depth of a navigation channel, the platform comprising an
agitation system for performing agitation for mobilizing sediment
and displacing the mobilized sediment to a collector which is
embedded in the bottom of the navigation channel, the collector
being a trench in the navigation channel wherein the trench has,
when not being filled with sediment, a bottom level positioned
substantially deeper than the nautical depth of the navigation
channel.
[0024] The platform further may comprise the collector for
collecting the mobilized mud.
[0025] The platform may comprise a dredging pumping system for
pumping the liquefied sediment or for collecting the sediment from
the collector.
[0026] The collector may be a trench made in the seabed of the
navigation channel.
[0027] The agitation system may be based on a floating platform or
vessel.
[0028] The water injection system may comprise a submersed system
with mounted or integrated nozzles.
[0029] The water injection system may comprise one or more mats
where injectors are integrated and connected with a water injection
pump. The mat may be a mat suitable for scour protection or as
surface or wall to shape a collector.
[0030] The collector may be formed and shaped in the soil or in the
mud.
[0031] The collector may be made out of material like concrete or
steel.
[0032] The water injection platform may furthermore comprise a
monitor system for measuring soil strength and density for
determining the dredging power, the dredging effort in hours and
the water injection volume to erode, liquefy and mobilise an
underwater sediment layer.
[0033] The water injection platform may comprise a monitor system
for predicting when the sediment needs to be removed from the
collector for guaranteeing a predetermined nautical depth or
consolidation level or density level in the collector.
[0034] The water injection platform may comprise a pumping station
on a dredging ship for pumping the sediment from the collector
towards a dredging ship or a stationary pumping station for pumping
the sediment from the collector towards a pipe line to relocate the
sediment to a dumping or treatment site where the sediment is
permanently stored or where it is re-suspended and carried away
from the area temporally or permanently.
[0035] The present invention also relates to a monitor system for
assisting a dredging process in a navigation channel, the dredging
process comprising a step of performing agitation for mobilizing
sediment and displacing the mobilized sediment to a collector being
a trench in the navigation channel wherein the trench has, when not
being filled with sediment, a bottom level positioned substantially
deeper than the nautical depth of the navigation channel and a
separate step of, after solidification of the sediment collected in
the collector, removing the solidified sediment from the collector
so that the collector again has a bottom level positioned
substantially deeper than the nautical depth of the navigation
channel, the monitoring system being adapted for determining any of
soil strength and/or density and determining based thereon any or
more of the dredging power, the dredging effort, the water
injection volume to erode, liquefy or mobilise the underwater
sediment layer, and/or for predicting when the sediment needs to be
removed from the collector for guaranteeing a predetermined
nautical bottom level or consolidation level or density level in
the collector.
[0036] The monitoring system may be adapted for predicting when the
sediment needs to be removed from the collector based on an
estimate of the amount of mobilized sediment collected in the
collector and or the consolidation or density levels of the
sediment in the collector.
[0037] The present invention also relates to a mat for protecting
or forming a bottom for a navigation channel, the mat comprising a
fluid delivery system, such as for example an integrated or mounted
injectors, for injecting water for mobilizing sediment that has
formed on the mat.
[0038] The injectors may be integrated in the mat, the injectors
being part of or integrated in a fluidic channel system.
[0039] The injectors may be positioned at one end of the channels
of the fluidic channel system and wherein the channels are at the
other end are combined and form a water injection entrance.
[0040] The injectors may be oriented in a predetermined direction
away from perpendicular to the mat surface in order to displace the
sediment along a given direction.
[0041] The mat may be a mat suitable for scour protection or as
surface or wall to shape a collector.
[0042] The collector can act as a buffer where agitated and mobile
sediment can consolidate and be removed by different techniques
like a static or dynamic pump station or by a hopper dredger. The
collector can be shaped in this way that the liquefied and
mobilized sediment can flow towards a collection area. The angle of
repose of a sediment is reduced while the pore pressure of the
sediment is being increased to the point the sediment becomes a
liquefied substance or thixotropic substance and is being mobilized
by means of induced or natural currents or slope induced gravity to
a designated area or reservoir of collection called collector where
the sediment either is stored for relatively short periods or
consolidates to be collected at a later stage.
[0043] The collector can be .e.g. a central trench where the slopes
are under a sudden angle towards the trench induce to induce
sediment flowing towards the trench. The collector can also be a
network of trenches. The trenches can be natural or preinstalled
with a hopper dredger or by a plough dredger and or in combination
with water injection dredging, and are typically deeper than the
nautical depth of the port or waterway. Due to the fact that the
trenches are deeper than the nautical depth, they act as a buffer
location in space and time for liquefied sediment.
[0044] The sediment is then being pumped out by means of a pumping
station, this pumping station can be a dredging ship or in the case
the sediment remains in suspension in the collector a permanent
installation and a pipe line to relocate the sediment to a dumping
or treatment site where the sediment is permanently stored or
re-suspended and carried away from the area temporally or
permanently.
[0045] The sediment in suspension can be further threated.
Treatments of the suspension can be degassing in order to increase
the bulk density of the suspension and to let it stay low in the
water column. Treatments of the suspension can be adding micro or
larger gas bubbles into the suspension to oxidize the sediment
particles or to decrease the bulk density of the suspension in
order to let the suspension move upward in the water column.
Treatments can be the dewatering of the sediment suspension in
order to increase bulk density or increase the yield point of the
sediment suspension. Treatments can be dilution of the sediment in
order to decrease bulk density or decrease the yield point of the
sediment suspension.
[0046] The liquefaction of sediment layers in e.g. a shipping
channel comprises the injection of high volumes of water into the
sediment at relatively low pressures. The water volume can either
be injected from above the sediment by a water injection dredger or
from below the sediment by permanent infrastructure placed at or
below maintenance depth before the sediment settled down and formed
a sediment layer.
[0047] Typically sediment is being diluted to the point where all
solid properties of the sediment are lost and the suspended
sediment can be described as a fluid. Typically the injection
volume of additional water into the sediment is about a factor 0.25
to 3 higher than the volume of sediment to be mobilized, depending
on the initial bulk density of the sediment and the yield
characteristics of the sediment or sediment suspension.
[0048] The designated area of the collector where sediment
accumulation and or consolidation is possible is a buffer where the
re-suspended sediment is prevented to flow back into the dredged
area. Current measurements and models are often required to
determine the optimum time interval where further transport and
re-suspension can occur.
[0049] The time interval where the suspended sediment is buffered
before being transported can be extended by increasing the
suspended sediment layer thickness. Consolidation invokes an upward
going drainage current, hence the effect is similar to artificial
water injection into the sediment: the upper layer of the sediment
remains in suspension until the water current drops below a
critical discharge. This effect allows intertidal buffering of the
suspended sediment with a minor penalty of sediment that will
remain consolidated on the bottom of the reservoir.
[0050] When consolidation speed is to be increased additions to the
sediment can be made. A silt and or clay mixture can be mixed up
with sand particles in order to increase consolidation speed. In a
tidal area gas bubbles can also be added to the suspension in order
to have a natural pumping effect based on the increase and decrease
of the bubble volume in function of the change of hydrostatic
pressure, following the universal gas law V=nrT/P. The bubble
oscillation will pump additional water through the sediment drain
channels and as such enhance the sediment consolidation speed.
[0051] When consolidation speed is to be decreased extractions from
the sediment can be made. A sand fraction can be extracted in order
to decrease consolidation speed. In a tidal area gas bubbles can
also be extracted from the suspension in order to decrease the
natural pumping effect based on the increase and decrease of the
bubble volume in function of the change of hydrostatic pressure,
following the universal gas law V=nrT/P. A reduction of the bubble
oscillation will reduce pumping of additional water through the
sediment drain channels and as such decrease the sediment
consolidation speed.
[0052] In order to determine if the sediment can be eroded by water
injection dredging, soil strength, soil rheological parameters and
soil density parameters need be measured. An example of a soil
strength measurement instrument is a free fall penetrometer where
the intrusion resistance is a measure for the strength of the soil.
The soil strength is in relation with the water injection power to
erode a sediment layer.
[0053] In order to determine how much water needs to be added to
liquefy the sediment and make it Newtonian or quasi-Newtonian, the
density of the sediment layer before the injection dredging action
needs to be measured.
[0054] The combination of strength and density measurement allows
to exactly determine the dredging power and dredging time to erode,
liquefy and mobilize a sudden mud volume.
[0055] Besides the preparation and planning of the dredging
operations both measurement methods can also be used to follow up
the status of the liquefied suspension in the collector.
[0056] Permanent or non-permanent water injection into the sediment
can hold the sediment longer into suspension if longer time
intervals is a requirement. When water injection dredging is
applied the sediment is liquefied and potentially suspended in the
water column. The sediment load in the water column can be measured
and traced by turbidity sensors. E.g. local measurements with
acoustic Doppler current profilers (ADCP) or optical turbidity
sensor can show how and in which direction the mobilized mud is
moving. The turbidity sensor can be installed on an autonomous
vessel to follow from the surface the underwater sediment flow.
[0057] It is an advantage of embodiments according to the present
invention that systems and methods are provided for controlling WID
dredging actions by installing an underwater collector structure.
It is an advantage of embodiments according to the present
invention that a natural gravity flow is induced by such a
collector.
[0058] It is an advantage of embodiments according to the present
invention that the mud collector can be made of another material
then sediment e.g. concrete or metal.
[0059] It is an advantage of embodiments according to the present
invention that the on the mud collector injection nozzles are
mounted.
[0060] It is an advantage of embodiments according to the present
invention that the on the mud collector injection nozzles are
mounted on the collector structure and that the injection nozzles
are driven by a tidal pump system.
[0061] It is an advantage of embodiments according to the present
invention that scour protection mats are used as injection systems
where tubes and operating in the mats are functioning as injector.
By pumping water in the mats.
[0062] It is an advantage of embodiments according to the present
invention that scour protection mats are used as collector
surface.
[0063] It is an advantage of embodiments according to the present
invention that scour protection mats are combined with water
injection nozzles which are mounted on or in the mat and driven by
tidal pumps.
[0064] It is an advantage of embodiments according to the present
invention that systems and methods are provided to generate and
shape the collector in the mud layer. The collector can be shaped
by a HTSD or WID dredger or a plough dredger.
[0065] It is an advantage of embodiments according to the present
invention that systems and methods are provided to combine the
collector with a pump station. The pump station will suck the
liquefied sediment out of the collector and will transport it to a
dumping site. The pump station can be stationary and connected to a
quay wall or can be mobile and mounted on a floating platform.
[0066] It is an advantage of embodiments according to the present
invention that systems and methods are provided to combine the pump
station with a pipe lines or pipe floats to pump the sediment
outside a dock or waterway into the open water.
[0067] It is an advantage of embodiments of the present invention
that methods and systems are provided for analyzing the physical
soil parameters like tip and shear strength of a free fall cone to
determine the WID dredging power and effort.
[0068] It is an advantage of embodiments of the present invention
that methods and systems are provided for analyzing the physical
soil parameters like density of the sediment layer to determine the
gel point of the sediment and liquefying effort.
[0069] It is an advantage of embodiments of the present invention
that methods and systems are provided for analyzing the turbidity
to determine in which direction the liquefied sediment cloud is
directed. The turbidity can be analyzed by a turbidity sensor is
mounted on an unmanned surface vessel that is autonomous tracing
the sediment cloud.
[0070] It is an advantage of embodiments according to the present
invention that parameter such as required dredging power for
dredging the different soil layers can be derived, as well as the
nautical bottom of the waterway, the soil structure and the
identification of the soil type and that this information is used
to optimize the dredging effort.
[0071] The above objective is accomplished by a method and device
according to the present invention.
[0072] The present invention relates to a computerized system for
obtaining information regarding the related parameters of the water
injection dredging process and the status of the collector, the
system comprising an input means from sensors, for example sensors
on a WID or plough dredger, sensors in the navigation way, such as
in or near the collector, in or near mats in the navigation way,
sensors in probing systems, penetrometers, etc. Typically a
processor is provided for determining the relevant information.
Information regarding the shape, size or other features of the
collector also may be used.
SHORT DESCRIPTION OF THE DRAWINGS
[0073] FIG. 1 illustrates an example of an water injection dredger
as can be used in embodiments of the present invention.
[0074] FIG. 2 shows a T-bar with injection nozzles as can be used
in embodiments of the present invention.
[0075] FIG. 3 shows the injection dredging principle where sediment
is injected, liquefied, mobilized and displaced, according to an
embodiment of the present invention.
[0076] FIG. 4 shows the water injection principle in combination
with a trench. The trench is cut out of the seabed. The water
injection dredging technique is used to erode and mobilize sediment
from around the trench into the trench, according to an embodiment
of the present invention.
[0077] FIG. 5 show a cross section of a navigation channel where
the seabed soil underwater is depicted, before applying a method
according to an embodiment of the present invention.
[0078] FIG. 6 shows a navigation channel where in the middle of the
channel a trench is made, according to an embodiment of the present
invention.
[0079] FIG. 7 shows a figure where the sediment in the navigation
channel is mobilized from the side into the trench, according to an
embodiment of the present invention.
[0080] FIG. 8 illustrates the working procedure according to an
embodiment of the present invention, wherein the erosion is done in
steps starting from close to the trench going to the other sides.
While mobilizing the sediment a small slope is introduced.
[0081] FIG. 9 shows a filled trench with water sediment emulsion as
can be obtained using a method according to an embodiment of the
present invention. The trench is used to consolidate the
sediment.
[0082] FIG. 10. Illustrates features and principles as can be used
for determining the liquid delivery system parameters in mats
usable in embodiments of the present invention.
[0083] FIG. 11 to FIG. 14 illustrate features and principles as can
be used in methods and systems for monitoring or assisting in
dredging methods according to embodiments of the present
invention.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0084] In the following detailed description, specific details are
set forth in order to provide a thorough understanding of the
invention and how it may be practiced in particular embodiments.
However it will be understood that the present invention may be
practiced without these specific details. In other instances,
well-known methods, procedures and techniques have not been
described in detail, so as not to obscure the present invention.
While the present invention will be described with respect to
particular embodiments and with reference to certain drawings, the
reference is not limited hereto. The drawings included and
described herein are schematic and are not limiting the scope of
the invention. It is also noted that in the drawings, the size of
some elements may be exaggerated and, therefore, not drawn to scale
for illustrative purposes.
[0085] Furthermore, the terms first, second and the like in the
description and in the claims, are used for distinguishing between
similar elements and not necessarily for describing a sequence,
either temporally, spatially, in ranking or in any other manner. It
is to be understood that the terms so used are interchangeable
under appropriate circumstances and that the embodiments of the
invention described herein are capable of operation in other
sequences than described or illustrated herein.
[0086] It is to be understood that the terms used in embodiments of
the invention described herein are capable of operation in other
orientations than described or illustrated herein.
[0087] It is to be understood that the term "comprising" should not
be interpreted as being restricted to the steps or elements listed
thereafter; it does not exclude other elements or steps. It is thus
to be interpreted as specifying the presence of the stated
features, integers, steps or components as referred to, but does
not preclude the presence or addition of one or more other
features, integers, steps or components, or groups thereof. Thus,
the scope of the expression "a device comprising A and B" should
not be limited to devices consisting only of components A and
B.
[0088] Where in embodiments according to the present invention
reference is made to a waterway, reference is made to a navigable
body of water, such as a river, channel, canal, sea, lake or
ocean.
[0089] Where in embodiments according to the present invention
reference is made to agitation dredging type identification,
reference is made to water injection dredging of the soil based on
injection of the top layer of the soil, eroding, liquefying and
displacing the top layer of the soil consisting of sediment. This
dredging technique can be combined with plough dredging to help
moving mechanically the soft sediment.
[0090] Where in embodiments according to the present invention
reference is made to "nautical depth", reference is made to the
depth where physical characteristics of the bottom of a waterway
reach a critical limit beyond which normal navigation is not
possible. The nautical bottom can be defined as the level where
physical characteristics of the bottom reach a critical limit
beyond which contact with a ship's keel influences the
controllability and maneuverability. According to embodiments of
the present invention, the nautical depth may be defined as in the
report Navigation in muddy areas, Supplement to Bulletin no. 43,
PTC2 report of WG 03-1983 issue, MarCom Working Group 03.
[0091] Where in embodiments according to the present invention
reference is made to "soil structure" and "soil type" or "soil type
identification", reference is made to the classification of the
soil type based on the physical parameters of the measured soil.
Based on for example the density, shear stress, viscosity and other
physical parameters a soil type can be identified.
[0092] Where in embodiments according to the present invention
reference is made to a soil type identification, reference is made
to the classification of the soil type based on the physical
parameters of the measured soil.
[0093] In a first aspect, the present invention relates to a
dredging method for displacing sediment in a navigation channel
towards a deeper collector in order to keep the navigation channel
on a sudden depth. According to embodiments of the present
invention, a method is described for dredging a navigation channel
for guaranteeing a nautical depth of a navigation channel. The
method comprises performing agitation for mobilizing sediment and
displacing the mobilized sediment to a collector which is embedded
in the bottom of the navigation channel. The method also may
comprise, in a step different from said performing agitation
dredging, removing sediment from the collector. Said displacing the
mobilized sediment may be performed by water injection.
[0094] By way of illustration some standard and optional steps are
described with reference to an exemplary method comprising several
steps.
[0095] First step is the use of agitation dredging to mobilize
sediment from one place to another. In FIG. 7 a navigation channel
is depicted where via the method described in FIG. 3 the top of the
soil consisting of deposited sediment is eroded, liquefied and
displaced. The displacement is established by the injected water
after it was eroded. The displacement can take place over several
tens of meters.
[0096] The second step is to mobilize the sediment from the bed of
a navigation channel towards a deeper positioned trench in the
navigation channel. In FIG. 8 a deeper trench in the middle of a
navigation channel is depicted. By eroding and liquefying the edges
around the trench the loose sediment can be moved into the trench.
By moving a portion of the sediment a slope for the sediment
further away from the trench is created. During this process the
water injection dredger can be assisted by a plough dredger.
[0097] The third step is to let the mobilized and liquefied
sediment consolidate in the trench. The sediment in the trench is
liquefied by the added water of the water injection dredger. By
collecting the sediment and leave it untouched over time it will
start to dewater and consolidate as depicted on FIG. 9.
[0098] The fourth step is a method to empty the collector. The
emptying of the collector can happen via a pumping system. The
pumping system can a stationary pump or a mobile pump or a jumbo
hopper dredger.
[0099] Instead of applying a water injection dredger to erode and
mobilize the sediment on the seabed of the navigation channel an
anti-erosion mat with an internal water injection pumping system
could be deployed. When sediment is on top of the mat, water can be
injected through the mat so the sediment is liquefied and starts to
mobilize. When the mat is under a sudden angle of repose the
sediment will start to flow toward a lower point like a collector.
Such a mat thus may comprise a fluid delivery system, such as for
example integrated or mounted injectors for injecting water or a
structure for diffusively providing water, whereby the fluid
delivery system is adapted for mobilizing sediment that has formed
on the mat. When injectors are used, such injectors can be
integrated in the mat. Such injectors may be part of or integrated
in a fluid channel system. The injectors may for example be
positioned at one end of the channels of the fluidic channel system
and the channels may be combined at the other end and form a water
injection entrance. Such a water injection entrance may for example
be interconnected with a pumping system for pumping water through
the mats or may be for example be based on tidal flow. The
injectors or water openings may be oriented in such a direction
with respect to the mat surface, such that a displacement in a
given direction can be enforced to the sediment. The mats used may
be suitable for scour protection or may serve as a surface or wall
to shape a collector. Design of the mats and the fluid delivery
therein can be performed taking into account how consolidation of
sediment can be prevented. By way of illustration, an illustration
of considerations to be taken into account are described below.
FIG. 10 depicts consolidation behaviors of 2 different substances.
The evolution of the top of the mud in function of the time is
depicted. When injecting water from below the volume of water
injected must be at least equal to the volume of water drained from
the system. The required volume of water must be equal or more than
the worst case drain scenario over a time span of 1 tidal cycle, on
average 12 h. Also consolidation speed depends on the mud layer
thickness. In order to find the worst case requirements a sample
must be taken in-situ, liquidized to the point where yield stress
starts to form in the sediment, and a sedimentation column must be
filled with sediment until the worst case thickness of the sediment
layer that will lay upon the infrastructure. In FIG. 10, the
modified mud1 consolidation was 20 cm during one tidal cycle, this
would mean that a discharge from below of at least 0.2 m.sup.3/m
per 12 hours must be done in order to let the sediment recover the
drained water. Ideally, the discharge into the sediment layer is at
least 2 times higher than the drained volume. The reason why it
must be higher is that internal drain channels in the consolidating
sediment will also partly drain the injected water and as such
reduce the efficiency of the injection. It is expected that the
consolidation curve described here is rapid and most sediments in
ports will consolidate slower.
[0100] The injection of water into the sediment can be done diffuse
or by injection nozzles, both systems have advantages and
disadvantages. In general one could state that a violent discharge
of water into the consolidating sediment will be the most efficient
system, since it destroys all internal structures formed during the
consolidation. Violent discharge will require nozzles and large
volumes of water will need to be available, diffuse injection will
require a low discharge rate, minimal water volumes but internal
structures in the sediment will be preserved, resulting in a
gradual efficiency decrease.
[0101] In one aspect, the present invention relates to a water
injection platform for dredging a navigation channel for
guaranteeing a nautical depth of a navigation channel, the platform
comprising an agitation system for performing agitation for
mobilizing sediment and displacing the mobilized sediment to a
collector which is embedded in the bottom of the navigation
channel. The platform further may comprise the collector. The
collector may be a trench in the navigation channel or may be an
artificial collector having concrete or metal walls. Furthermore, a
dredging pumping system for pumping the liquefied sediment also may
be comprised. Other features may correspond with elements of the
injection platform used for describing the above method or with
means for performing method aspects of the method as described
above.
[0102] Whereas the mat has been described above as part of an
injection platform, the present invention also relates in another
aspect to a mat as such, comprising standard and/or optional
features as described above.
[0103] In yet another aspect the present invention relates to a
measurement method for obtaining information regarding the
preparation of the dredging method and the follow up of the dredged
area and the collector. The present invention thus also relates to
a method for assisting a dredging process in a navigation channel,
the dredging process comprising a step of performing agitation for
mobilizing sediment and displacing the mobilized sediment to a
collector in the navigation channel and a separate step of removing
sediment from the collector. The method for assisting comprises
determining any of soil strength and/or density and determining
based thereon any or more of the dredging power, the dredging
effort, the water injection volume to erode, liquefy or mobilise
the underwater sediment layer. Additionally or alternatively the
method for assisting comprises predicting when the sediment needs
to be removed from the collector for guaranteeing a predetermined
nautical depth or a consolidation level or density level in the
collector. Such predicting may be based on an estimate of the
amount of mobilized sediment collected in the collector. For
determining the parameters as described above, use can be made of a
free fall penetrometer, such as for example a free fall
penetrometer as known from literature. It is to be noticed that for
determining the parameters and their use, information may be taken
into account regarding the position, shape or other details of the
collector in the navigation way. By way of illustration,
embodiments of the present invention not being limited thereto,
some further details and advantages may be illustrated with
reference to FIGS. 11 to 14.
[0104] As depicted in FIG. 11 there is a relationship between the
cutting depth of the injection nozzle of a WID dredger and the
resistance of intrusion of a free fall penetrometer. By taking free
fall penetrometer measurements of the sediment layers in the zone
of interest, one can predict the cutting depth and the volume of
sediment that will be influenced and agitated by the nozzle
action.
[0105] The bulk density levels of the in-situ sediment determine
the amount of water that need to be added in order to bring the
sediment to the liquefaction point. As depicted on FIGS. 12, 13 and
14, out of the cutting depth and the density levels the number of
times a sudden water injection dredger need to go over measured
zone to liquefy and mobilize the measured sediment.
[0106] In one aspect, the present invention also relates to a
monitoring system for performing a method as described above. Such
a monitoring system may be a processing system performing the
method steps of the method for assisting dredging as described
above, and may include or be connectable to a free fall
penetrometer or other parameter determination means for determining
parameters. In some embodiments the processing system may also be
wireless connectable to such devices for receiving parameter
input.
[0107] In a further aspect, the present invention relates to a
computer program product for, when executing on a computing device,
executing the determining and/or deriving of information as
described in the method according to the above aspects. The present
invention also relates to a computer-readable data carrier storing
a computer program product according to this further aspect, and to
the transmission of such computer program product over a
communication network. The present invention thus also includes a
computer program product, e.g. an application program product also
referred to as applet, which provides the functionality of any of
the data processing steps of the methods according to the present
invention when executed on a computing device. The computer program
product can also be transmitted via a carrier wave in a network,
such as a LAN, a WAN or the Internet. Transmission media can take
the form of acoustic or light waves, such as those generated during
radio wave and infrared data communications. Transmission media
include coaxial cables, copper wire and fibre optics, including the
wires that comprise a bus within a computer.
[0108] While the invention has been illustrated and described in
detail in the drawings and foregoing description, such illustration
and description are to be considered illustrative or exemplary and
not restrictive. The invention is not limited to the disclosed
embodiments.
[0109] The foregoing description details certain embodiments of the
invention. It will be appreciated, however, that no matter how
detailed the foregoing appears in text, the invention may be
practiced in many ways, and is therefore not limited to the
embodiments disclosed. It should be noted that the use of
particular terminology when describing certain features or aspects
of the invention should not be taken to imply that the terminology
is being re-defined herein to be restricted to include any specific
characteristics of the features or aspects of the invention with
which that terminology is associated.
* * * * *