U.S. patent application number 14/391357 was filed with the patent office on 2015-03-19 for method of and system for installing foundation elements in an underwater ground formation.
The applicant listed for this patent is IHC HOLLAND IE B.V.. Invention is credited to Justin Edward Stam.
Application Number | 20150078836 14/391357 |
Document ID | / |
Family ID | 48237202 |
Filed Date | 2015-03-19 |
United States Patent
Application |
20150078836 |
Kind Code |
A1 |
Stam; Justin Edward |
March 19, 2015 |
METHOD OF AND SYSTEM FOR INSTALLING FOUNDATION ELEMENTS IN AN
UNDERWATER GROUND FORMATION
Abstract
A method of and system for installing a foundation element, in
particular a (mono)pile, in a hard underwater ground formation uses
a driver. The method comprises the steps of placing a foundation
element on the underwater ground formation, placing a screen for
reducing noise input from the driver, driving the foundation
element into the ground formation by means of the driver while the
screen is positioned about the foundation element, and attenuating
noise transfer from the underwater ground formation to the outer
wall of the screen during at least part of the driving.
Inventors: |
Stam; Justin Edward;
(Lierderhholthuis, NL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
IHC HOLLAND IE B.V. |
EP Sliedrecht |
|
NL |
|
|
Family ID: |
48237202 |
Appl. No.: |
14/391357 |
Filed: |
April 10, 2013 |
PCT Filed: |
April 10, 2013 |
PCT NO: |
PCT/NL2013/050263 |
371 Date: |
October 8, 2014 |
Current U.S.
Class: |
405/228 ;
181/284 |
Current CPC
Class: |
E02B 2017/0065 20130101;
E02D 7/14 20130101; B63B 35/44 20130101; E02D 7/06 20130101; E02D
7/02 20130101 |
Class at
Publication: |
405/228 ;
181/284 |
International
Class: |
E02D 7/02 20060101
E02D007/02; B63B 35/44 20060101 B63B035/44 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 11, 2012 |
NL |
2008625 |
Claims
1. A method of installing a foundation element in a hard underwater
ground formation by means of a driver, comprising: placing a
foundation element on the underwater ground formation, placing a
screen for reducing noise input from the driver, driving the
foundation element into the ground formation by means of the driver
while the screen is positioned about the foundation element, and
attenuating noise transfer from the ground formation to an outer
wall of the screen during at least part of the driving.
2. The method according to claim 1, comprising at least
substantially dynamically uncoupling at least the outer wall of the
screen from the ground formation.
3. The method according to claim 2, wherein at least a lower end of
the outer wall of the screen is maintained at a distance from the
ground formation.
4. The method according to claim 3, wherein the screen is
suspended.
5. The method according to claim 3, wherein the screen is at least
50% buoyant.
6. The method according to claim 5, wherein the screen floats and
is held in position by one or more weights on the ground
formation.
7. The method according to claim 1, wherein a noise attenuating
material is being positioned between the ground formation and the
lower end of the outer wall of the screen.
8. The method according to claim 7, wherein a modulus of the
material is lower than a modulus of the material of the outer wall
of the screen and lower than a modulus of the underwater ground
formation.
9. A system for installing foundation elements in a hard underwater
ground formation, comprising a driver, a surface vessel configured
to secure the driver, and a screen carried by the surface vessel to
be placed about the foundation element to reduce noise input from
the driver, and an assembly configured to attennuate noise transfer
from the ground formation to an outer wall of the screen during at
least part of the driving.
10. The system according to claim 9, wherein the surface vessel
comprises, in addition to a crane configured to secure the driver
during driving, a crane configured to maintain the screen at a
distance from the ground formation during at least part of the
driving.
11. The system according to claim 9, wherein the screen is at least
50% buoyant.
12. The system according to claim 11, wherein the screen comprises
at least an inner wall and an outer wall.
13. The system according to claim 12, wherein the screen has a
buoyancy in excess of 100% and the system further comprises a
weight configured to maintain the floating screen upright.
14. The system according to claim 9, wherein the screen is provided
with a support of a noise attenuating material to be positioned
between the lower rim of the screen and the ground formation.
15. The system according to claim 14, wherein a modulus of the
support is lower than a modulus of the material of the outer wall
of the screen and lower than a modulus of the underwater ground
formation.
16. A noise mitigation system comprising a screen configured to be
placed about a foundation element to reduce noise when driven into
a ground formation, and an assembly configured to attenuate noise
transfer from the ground formation to an outer wall of the
screen.
17. The system according to claim 16, wherein the screen is at
least 50% buoyant.
18. The system according to claim 16, wherein the screen comprises
at least an inner wall and an outer wall.
19. The system according to claim 16, wherein the screen has a
buoyancy in excess of 100% and the system further comprises a
weight configured to maintain the floating screen upright.
20. The system according to claim 16, wherein the screen is
provided with a support of a noise attenuating material to be
positioned between a lower rim of the screen and the ground
formation.
21. The system according to claim 16, wherein a modulus of the
support is lower than a modulus of the material of the outer wall
of the screen.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application is a national stage filing of
International patent application Serial No. PCTNL2013/050263, filed
Apr. 10, 2013, and published as WO 2013154428 A2 in English.
BACKGROUND
[0002] The discussion below is merely provided for general
background information and is not intended to be used as an aid in
determining the scope of the claimed subject matter.
[0003] Aspects of the invention relate to a method of installing a
foundation element, in particular a (mono)pile, in a hard
underwater ground formation by means of a driver, such as an
hydraulic driver. The method comprises the steps of placing a
foundation element on the underwater ground formation, placing a
screen for reducing noise input from the driver into the
surrounding water, and driving the foundation element into the
ground formation by means of the driver while the screen is
positioned about the foundation element. Aspects of the invention
further relates to a system for installing foundation elements.
SUMMARY
[0004] This Summary and Abstract herein are provided to introduce a
selection of concepts in a simplified form that are further
described below in the Detailed Description. This Summary and the
Abstract are not intended to identify key features or essential
features of the claimed subject matter, nor are they intended to be
used as an aid in determining the scope of the claimed subject
matter. The claimed subject matter is not limited to
implementations that solve any or all disadvantages noted in the
background.
[0005] An aspect of the invention to further improve noise
mitigation, in particular when driving foundations elements in hard
subsea ground formations andor when the noise mitigation screen is
made of a material having a high modulus of elasticity, e.g. in
excess of 100 GPa.
[0006] To this end, the method comprises attenuating noise transfer
from the (underwater) ground formation to the outer wall of the
screen during at least part of the driving, preferably by at least
substantially dynamically uncoupling at least the outer wall of the
screen from the ground formation.
[0007] It was found that the medium, typically (sea)water, between
the foundation element, e.g. a monopile, and the screen is not the
only acoustic transfer path and that noise generated by the pile
driver is transmitted from the pile to the outer wall of the screen
also via the ground formation the screen is resting on or in. This
is particularly true when the ground formation comprises hard
materials, such as rock, concrete blocks (scour protection) or
compacted sand, andor when the screen is made of a material having
a high modulus of elasticity. As noise generated by the pulse-like
blows of a pile driver contains a wide spectrum of frequencies, the
outer wall of the screen is typically excited at one or more
eigenfrequencies, which dampen out relatively slowly. By
attenuating noise transfer via the ground formation, such
excitation is avoided or at least reduced and overall acoustic
radiation is further mitigated.
[0008] Attenuation is achieved passively e.g. by reducing, relative
to prior art methods and systems, the stiffness (modulus) of the
interface between the ground formation and the lower end of at
least the outer wall of the screen, or actively e.g. by
establishing the main eigenfrequencies of the screen and providing
means for extinguishing these frequencies in the noise generated by
the pile driver.
[0009] In an embodiment, the lower end of the outer wall of the
screen is maintained at a distance from, typically above, the
ground formation, e.g. by suspending the outer wall from an inner
wall of the screen (if the screen is double walled), from the pile
(if the screen is single walled) or from a surface vessel. The
distance is preferably in a range from 5 to 200 centimeters,
preferably 10 to 100 centimeters, preferably 15 to 70
centimeters.
[0010] In another embodiment, the screen is at least 50%,
preferably at least 70% buoyant, or even has a buoyancy of 100% or
more (at 100%, the density of screen equals the density of the
(sea)water), in which case the screen floats. In this latter
configuration, it is preferred that the screen is held in position
by one or more weights on the ground formation, such as concrete
blocks or a bubble ring resting on the ground formation, and
connectors, such as straps or chains, connecting the screen to the
blocks or ring.
[0011] In yet another embodiment, a noise attenuating material,
typically in the shape of a ring having a circumference that
corresponds to that of the screen, is being positioned between the
lower end of the outer wall of the screen and the ground
formation.
[0012] An aspect of the invention further relates to a system for
installing foundation elements, in particular (mono)piles, in a
hard underwater ground formation, comprising a driver, a surface
vessel, and a screen to be placed about the foundation element to
reduce noise input from the driver. The system further comprises
means for attenuating noise transfer from the ground formation to
the outer wall of the screen during at least part of the
driving.
[0013] In an embodiment, the surface vessel comprises, in addition
to a crane for securing the driver, a crane for suspending the
screen and maintaining the screen at a distance from the ground
formation during at least part of the driving. Note is this respect
that known vessels comprise a single crane for handling the pile
and screen and for securing the pile driver during operation.
[0014] In another embodiment, the screen is at least 50%,
preferably at least 70% buoyant or even has a buoyancy of 100% or
more and to that end e.g. comprises one or more chambers andor is
made from a material having a density lower than that of water.
[0015] In yet another embodiment, the screen is provided with a
support, attached to or separate from the screen, of a noise
attenuating material, preferably of a material having a modulus
that is lower than the modulus of the material of the outer wall of
the screen and lower than the modulus of the underwater ground
formation. During driving, the support is positioned between the
lower rim of the screen and the ground formation.
[0016] Aspects of the invention will now be explained in more
detail with reference to the Figures, which show a preferred
embodiment of the present method and system.
[0017] Within the framework of the present disclosure, the words
"hard ground formation" refer to formations, natural or artificial,
which, at least at the interface with the screen comprise material
having a modulus of elasticity in excess of 10 MPa. Typical
examples include, but are not limited to, rock (modulus usually in
a range from 10 to 90 GPa), densely packed sand (modulus usually 20
to 150 MPa), and so-called scour protection (modulus usually 10 to
90 GPa), i.e. rocks, concrete blocks or the like dumped at the
driving site prior to driving and intended to protect installed
foundations element from erosion e.g. by strong currents.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a cross-section of a first embodiment, wherein the
noise mitigation screen is suspended from a surface vessel.
[0019] FIGS. 2 and 3 are a perspective view and a cross-section of
a second embodiment comprising an inflatable cushion.
[0020] FIG. 4 is a perspective view of a third embodiment
comprising a floating screen.
[0021] It is noted that the Figures are schematic in nature and
that details, which are not necessary for understanding the present
invention, may have been omitted.
DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS
[0022] FIG. 1 shows an embodiment of a system 1 for installing a
monopile 2 in an underwater ground formation 3, e.g. a seabed. In
this example, the monopile 2 has a circular cross-section and a
diameter of five meters and is intended to serve, after
installation, as the foundation of a wind turbine.
[0023] The system 1 comprises an hydraulic driver 4 (depicted in
FIG. 2), e.g. an IHC Hydrohammer S-1800, connected to a power pack
on board of a surface vessel, such as a ship 5 or jack-up barge, a
driver screen 6 for securely mounting the driver on the monopile
and an anvil (hidden from view by the driver screen) for
transmitting impact energy from the driver 4 to the monopole 2.
[0024] The system further comprises a noise mitigation screen 7,
made of e.g. steel, to be placed about the foundation element to
reduce noise input from the driver 4 into the surrounding water. In
this example, the screen 7 comprises an inner wall 8 and an outer
wall 9, i.e. is double walled, has a circular cross-section and an
inner diameter of six meters. The double wall provides one or more
chambers 10 for air or a porous material and renders the screen 7
50% buoyant.
[0025] The upper rim of the screen 7 is provided with a detachable
extender, which is used to adjust the effective length of screen 7
to the depth of the water at the location where the foundation
element is to be installed. In general, it is preferred that, once
in place, the sound-insulating screen 7 extends to above the water
level.
[0026] The ship 5 comprises a first crane 11 to lift and manipulate
the monopile 2 and the screen 7 and a second crane (not shown) to
secure the hydraulic driver 4 during driving.
[0027] Installation of a monopile is carried out for instance as
follows. The cables of the crane are attached to the upper end of a
monopile stored on the deck of the ship and the monopile is lifted
overboard, manipulated to an upright position, lowered onto the
seabed and, if required by the circumstances, allowed to penetrate
the scour protection and possibly the seabed under its own weight.
At this stage, the monopile 2 is driven, e.g. by means of a
vibratory device, into the seabed to a depth of some meters to
further stabilize the monopole 2.
[0028] The driver 4 is positioned on top of the monopile 2 and the
screen 7 is lifted over the monopile 2 and the driver 4.
Alternatively, the screen 7 is placed and the driver 4 is
subsequently placed inside the screen 7 and on top of the pile 2.
In this position, the pile 2 is driven to the required depth.
Finally, the driver 4 is removed, the screen 7 lifted over the pile
2 and placed back on deck or into the sea, and installation is
completed.
[0029] A distance in a range from 20 to 100 centimeters is
maintained between the lower rim of the screen 7 and the seabed,
thus dynamically uncoupling the two. As a result, substantially no
noise or vibrations are transmitted to the screen 7 via the seabed.
Although noise leaks through the annular opening resulting from the
distance, the energy of this noise is significantly less that that
of the noise generated by excitation of the outer wall of the
screen 7 by the seabed, i.e. overall acoustic radiation is further
mitigated.
[0030] In the embodiment shown in FIGS. 2 and 3, the screen 7 rests
on an annular inflated cushion 12, which has a modulus of
elasticity that is at least one order of magnitude smaller than the
modulus of the seabed and the modulus of the screen 7. Thus, the
cushion effectively attenuates at least the higher frequencies,
i.e. serves as a low pass filter.
[0031] FIG. 4 shows a system comprising a screen 7 having a
buoyancy in excess of 100%, e.g. achieved by spacing the inner and
outer walls of screen 7 farther apart, and a weight 13 for holding
the floating screen 7 upright and spaced from the seabed over a
distance in a range from 20 to 100 centimeters. In this example,
the weight 13 is provided by a ring for generating a bubble screen
inside the double walled screen 7, i.e. the outer diameter of the
ring 13 is smaller than the inner diameter of the buoyant screen 7.
The screen 7 is attached to the ring 13 by means of straps 14.
[0032] The invention is not restricted to the embodiment described
above and can be varied in numerous ways within the scope of the
claims. For instance, the outer wall of the screen can be suspended
from the inner wall of the screen (resting on the ground
formation), e.g. by interconnections between the inner and outer
walls. It is preferred that such interconnections are made of or
provided with a dampening material.
* * * * *