Patent Application
20150218770
The present disclosure relates generally to a modified pile foundation system for scour protection. In particular, the present disclosure relates to systems and methods for reducing scouring by disposing an enclosure around a pile.
This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present techniques. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present techniques. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
Pile foundations may be utilized for the support of various structures such as offshore structures, including large offshore platforms, floating storage vessels, oil-rigs, and other offshore subsea equipment to safely carry and transfer a structural load to the bearing strata located at some depth below the surface of the sediment. In operation, a pile foundation may steady and hold the position of the offshore structure in a harsh environment including rough currents, waves, flood-waters, and any action caused by a vessel-propeller. Today, pile foundation systems are one of the most commonly used anchoring technologies in transferring load through compressible or component sediments in many deep-water offshore production techniques.
There are various types of piles and many are classified with respect to their load transmission and functional behavior. Types of piles include end bearing piles, settlement reducing piles, tension piles, laterally loaded piles, piles in fill, and friction piles. Friction piles derive their load carrying capacity from the adhesion or friction of the soil sediment in contact with the shaft of the pile. The load carrying capacity of a friction pile may be partially derived from end bearing and partially from skin friction between the embedded surface of the pile and the surrounding soil.
One type of friction pile is a suction pile and is an alternative to traditional pile foundations such as driven piles, drag anchors, and gravity caissons. The advantages of suction piles, as opposed to traditional systems, may include various cost cutting benefits and ease of installation and removal. A suction pile may be a cylindrical structure, closed on one end and open on the other, and may be used underwater to secure many offshore structures.
There are usually two stages to the installation of the suction pile. The first stage may include lowering the suction pile onto the seabed where the suction pile is partially embedded deep into the soil sediment under its own weight. The second stage may include the suction pile undertaking a suction force created by pumping water out of the top of the suction pile through a port. The proportions of the pile and the suction force may be dependent upon the type of soil sediment the suction pile may encounter. Sand may be difficult to penetrate but may provide good holding capacity. Thus, the height of the suction pile may be as short as half the diameter and the hydraulic gradient may reduce the resistance of the sand to zero. With clays and mud soil types, the suction pile may easily penetrate but such sediment types may provide poor holding capacity. Thus, a suction pile in a clay or mud environment may have a height that is several times greater than its diameter. Additionally, in a clay and mud environment, the suction force may exceed the tip and skin resistance of the pile. Thus, site investigative soil test may be conducted to determine the impact of the sediment's capacity on the pile.
Another type of frictional pile is a driven pile which may be a structural column configured to be driven, pushed, or otherwise installed into the soil. Driven piles may be installed using some form of external weighted force such as a hammer to drive the pile into unexcavated soil.
One conventional method of driving a pile into place may include using a heavy weight placed between guides and raising the weight until it reaches its highest point. The weight may then be released landing forcefully upon the pile in order to drive the pile deep into the sediment. Various methods may be utilized to raise the weight and drive the pile including a diesel hammer, a hydraulic hammer, a hydraulic press-in, a vibratory pile driver, a vertical travel lead system, among other methods.
Regardless of the type of pile utilized, the removal and deposition of seabed sediment caused by waves and currents may significantly reduce the holding capacity of the pile. This removal of the seabed sediment is referred to as scouring. Scouring may occur when waves and currents pass around an object, such as a pile in the water column. Several types of scouring may be identified with piles supporting offshore structures. One type of scouring may include erosion of the sea bottom (sea-bottom scour) proximate the pile due to unidirectional waves and currents. As the water flows around the pile or the pile is struck by forceful waves and currents, the water may change direction and accelerate. Another type of scouring may include the loss of soil around a pile due to the cyclic deflection of the pile under wave forces or the movement of mooring lines attached to the pile. Scouring may also occur due to ice dragging on the seabed. Thus, the sediment located in close proximity to the pile may be loosened, suspended, and carried away by such actions. This may possibly affect the functional basis of the pile located in the sediment and thus the stability of the offshore structure moored to the pile.
U.S. Pat. No. 8,465,229 to Maconocie et al. discloses an improved system for increasing an anchoring force on a pile. A sleeve is installed over the pile and may be used to provide an additional connecting force to the existing pile. The sleeve may include its own padeye for coupling an anchor line or other coupling member to a structure to be secured. Additionally, the sleeve may include an assembly of rings coupled together with at least one or more longitudinal members.
U.S. Patent Publication No. 2012/0128436 by Harris discloses a disk around a pile in an effort to reduce scouring in close proximity to the pile. The disk has a pile opening through which the pile protrudes and the disk sits on top of the seabed. The disk may include a peripheral skirt for embedding into the seabed below the portion of the disk installed above the seabed. The disk may also include partitions for segmenting chambers of the disk. The chambers may be filled with fluidized fill material, such as grout or concrete to hold the disk in place. However, there still remains a desire to provide scour protection to a pile system while providing maximum surface area contact between the pile and surrounding soil.
In one aspect of the present disclosure, a system for reducing scouring is provided. The system includes a pile having a maximum cross-sectional dimension, Dp. The system also includes an enclosure that is circumferentially disposed around the pile, the enclosure having a first end proximate a surface of a seabed; a second end distal the surface of the seabed; and a maximum cross-sectional dimension, De, wherein De is at least 1.25 times Dp.
In another aspect of the present disclosure, a method for reducing scouring around a pile is provided. The method providing a pile, where the pile has a maximum cross-sectional dimension, Dp. The method also includes installing an enclosure circumferentially around the pile, where the enclosure has a first end proximate a surface of a seabed, a second end distal the surface of the seabed, and a maximum cross-sectional dimension, De, wherein De is at least 1.25 times Dp.
In yet another aspect of the present disclosure, a system for reducing scouring around anchors used for offshore production facilities is provided. The system includes a plurality of piles for stabilizing an offshore floating structure, where each pile has a maximum cross-sectional dimension, Dp. The system also includes an enclosure that is circumferentially disposed around each pile, the enclosure having a first end proximate a surface of a seabed; a second end distal the surface of the seabed; and a maximum cross-sectional dimension, De, wherein De is at least 1.25 times Dp.
The advantages of the present disclosure are better understood by referring to the following detailed description and the attached drawings, in which:
In the following detailed description section, the specific embodiments of the present disclosure are described in connection with one or more embodiments. However, to the extent that the following description is specific to a particular embodiment or a particular use of the present disclosure, this is intended to be for exemplary purposes only and simply provides a description of the one or more embodiments. Accordingly, the disclosure is not limited to the specific embodiments described herein, but rather, it includes all alternatives, modifications, and equivalents falling within the true spirit and scope of the appended claims.
Various terms as used herein are defined below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in at least one printed publication or issued patent.
Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art would appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name only. The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. When referring to the figures described herein, the same reference numerals may be referenced in multiple figures for the sake of simplicity. In the following description and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus, should be interpreted to mean “including, but not limited to.”
As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary.
Concentrations, quantities, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a numerical range of 1 to 4.5 should be interpreted to include not only the explicitly recited limits of 1 to 4.5, but also include individual numerals such as 2, 3, 4, and sub-ranges such as 1 to 3, 2 to 4, etc. The same principle applies to ranges reciting only one numerical value, such as “at most 4.5”, which should be interpreted to include all of the above-recited values and ranges. Further, such an interpretation should apply regardless of the breadth of the range or the characteristic being described.
The term, “seabed” or “seafloor” as used herein means soil sediment located under a body of water. The body of water may be a freshwater body or a seawater body.
The term “substantially”, “substantially the same” or “substantially equal” as used herein unless indicated otherwise means to include variations of a given parameter or condition that one skilled in the pertinent art would understand is within a small degree variation, for example within acceptable manufacturing tolerances. Values for a given parameter or condition may be considered substantially the same if the values vary by less than 5 percent (%), less than 2.5%, or less than 1%.
The term “substantially different” as used herein means to include variations of a given parameter or condition that one skilled in the pertinent art would understand is not within a small degree of variation, for example outside of acceptable manufacturing tolerances. Values for a given parameter or condition may be considered substantially different if the values vary by greater than 1%, greater than 2.5%, or greater than 5%.
Scouring may cause seabed degradation and erosion around a pile. In some instances, the scouring may be significant, for example reaching a depth of at least twice the diameter of the pile, the maximum diameter of a pile may be 1.25 to 6 meters. Thus, if the soil sediment proximate the pile foundation is disturbed due to scouring activity, this may have severe implications on the functional performance of the pile. For example, the loads the pile may support may be reduced or the pile may become dislodged from the seabed floor, making the pile unstable and susceptible to various movements. In such situations, failure of the pile foundation system and unguided movement of the offshore structure may occur.
Embodiments of the present disclosure provide methods and systems for reducing souring. The system for reducing souring includes a pile. The pile may be a new or existing pile. The pile may be any suitable pile, for example a pile selected from the types of piles as described herein. In one or more embodiments, the pile may be commonly used in the offshore hydrocarbon production industry to moor offshore structures, risers, pipelines, and other subsea structures. In one or more embodiments, the pile may be a friction pile, for example a suction pile or a driven pile. A suction pile may also include a suction port to enable a suction force to be applied during installation to remove water and a positive force to be applied to add water during removal of the suction pile from the seabed. The pile may comprise any suitable material, for example concrete or metal. For offshore applications, the metals may include structural steel or cast-iron.
In operation, the pile 108 may penetrate the seabed 112 so that the top of pile 108 may be substantially flush with the seabed level 112. As used herein, the term “substantially flush” means within 1 meter or less of the surrounding seabed level. The method of installing the pile structure 108 may include removing water from a port 113 that, in turn, pulls the pile, e.g. a hollow cylinder, into the seabed 112. In some embodiments, the pile 108 may be forced into the seabed, for example, by driving the pile 108 into the seabed 112, as described herein. It should be noted that a plurality of piles 108 may be embedded in the seabed 112 so as to facilitate stability of the platform 102.
In one or more embodiments, prior to installation, the enclosure 106 may be circumferentially disposed around the pile 108. In one or more other embodiments, the enclosure 106 may be circumferentially disposed around an existing pile located in the seabed 112 to reduce scouring. In particular, axial wall(s) 106a of the enclosure 106 surround the upper portion of the pile 108.
A metal plate 114 may be installed at the top of the enclosure 106 at the axial end of the enclosure proximate the seabed 112. In one or more embodiments, the metal plate 114 may be configured to rigidly connect the pile 108 to the enclosure 106 during installation of a new pile. The metal plate 114 may be installed at the top of the pile 108 to preserve the portion of the seabed located between the enclosure 106 and the upper portion of the pile 108. A port 115 in the metal plate 114 may be used to allow water to exit the enclosure 106 during installation of the pile 108. This modified pile foundation system 104 may be implemented to reduce or substantially eliminate scouring of soil sediment 116 in close proximity to the pile foundation system 104, as shown in
The pile may include one or more external surfaces in contact with soil sediment. As shown in
The pile may have any suitable cross-sectional geometry, for example circular, oval, elliptical, or polygonal such as triangular, square, rectangular, pentagonal, hexagonal, etc. In one or more embodiments, one or more external surfaces of the pile may have one or more surface features to enhance frictional contact with the soil sediment.
As previously stated, the enclosure 106 may be configured to be disposed around the pile 108 having a maximum cross-sectional dimension, Dp 118. The enclosure has a maximum cross-sectional dimension, De, 122. The maximum cross-sectional dimension, De, may be at least 1.25 times the maximum cross-sectional dimension, Dp 118, of the associated pile 108 disposed within the enclosure 106. In one or more embodiments, the maximum cross-sectional dimension, De, may be at least 1.5 times the maximum cross-sectional dimension, Dp 118, of the associated pile, for example at least 1.75 times, at least 2 times, at least 2.5 times, or at least 3 times or more of the associated pile. The radially internal surface of the axial side wall(s) 106a of the enclosure 106 may be disposed a given distance from the radially outer surface(s) of the pile such that sufficient seabed 116 remains in contact with the pile 108. This may aid in maintaining the load carrying capacity of the pile 108, i.e. maintaining the effective length of the pile 108, while preventing scouring proximate to the pile 108.
Additionally, the enclosure may have a maximum axial dimension, Le 124. The maximum axial dimension, Le 124, may be any suitable dimension sufficient to extend below the surface of the seabed 112 to reduce or prevent scouring proximate the pile 108. In one or more embodiments, the maximum axial dimension, Le 124, may be determined based on the predicted scour depth for the pile 108. In one or more embodiments, the maximum axial dimension, Le 124, may be at least 10% of the maximum axial dimension, Lp 120, of the associated pile 108, for example at least 25%, at least 30%, or at least 40%, same basis. In one or more embodiments, at least 80% of the maximum axial dimension, Le 124, is disposed beneath the surface of the seabed 112, for example at least 90%, at least 95%, at least 99% or 100%, same basis. In one or more embodiments, the enclosure 106 may be configured to axially extend to a depth beneath the surface of the seabed 112 of greater than 1.3 times Dp, at least 1.5 times Dp, at least 2 times Dp, or more.
The enclosure 106 may have any suitable cross-sectional geometry, for example circular, oval, elliptical, or polygonal such as triangular, square, rectangular, pentagonal, hexagonal, etc. The enclosure 106 may have substantially the same cross-sectional geometry as the associated pile 108 or may have a substantially different cross-sectional geometry. In one or more embodiments, one or more external surfaces of the enclosure may have one or more surface features to enhance frictional contact with the soil sediment. The axial length of the enclosure 106 may comprise any suitable metal, for example structural steel or cast-iron metal.
As previously stated, in one or more embodiments, a metal plate 114 may be disposed on top of the axial side wall(s) 106a at the axial end of the enclosure 106 proximate the seabed 112. The metal plate 114 may be configured to connect the enclosure 106 and the pile 108. In one or more embodiments, the metal plate 114 may provide a rigid connection facilitated by welding, bolting, clamping, or any other type of connection that provides a sturdy and rigid connection. The metal of the metal plate 114 may comprise substantially the same metal as the axial side wall(s) 106a of the enclosure 106 or may comprise substantially different metal from the axial side wall(s) 106a of the enclosure 106. The metal plate 114 that may be constructed from any number of metals, such as steel or corrosion resistant alloys, among others. In one or more embodiments, the metal plate 114 may have sufficient weight to aid in disposing the enclosure 106 into the seabed 112. In one or more embodiments, the pile foundation system may be configured to connect enclosure 106 and the pile 108 during penetration of a new pile 108. In one or more other embodiments, the enclosure 106 of the pile foundation system may be disposed around an existing pile 108.
The water that may be removed from the suction pile 204 may be pumped out from the port 212 located at the top of the suction pile 204. The removal of the water through the port 212 creates a vertical load on the suction pile 204, forcing it to penetrate deep into the seabed 210. Although the suction pile 204 may initially be substantially flush with the seabed 210, the level of the seabed may be eroded and washed away until a scouring line 214 exists. Without the enclosure 202, the formation of the scouring line 214 and thus, the foundational displacement of the suction pile 204, may lead to the potential exposure and reduction in load carrying capacity of the suction pile 204. Accordingly, the enclosure 202 can reduce or eliminate the scouring proximate the suction pile 204. Additionally, the enclosure 202 can act to potentially increase the long-term integrity of the suction pile 204 by preventing coupling members, ice, waves, and currents from unsettling and removing soil sediment in area 216 located proximate the suction pile 204. This can protect both the sediment area 216 and the suction pile 204 from the adverse effects of scouring. Thus, although scouring may continue to erode other areas of the seabed 210 to scouring line 214, the sediment area 216 immediately adjacent to the suction pile 204 may not be compromised.
The suction pile system, as shown in
The maximum axial dimension, Le 219, or depth of the enclosure 202 may extend beyond the actual and/or predicted scouring line 214. Thus, the forces that lead to scouring are not able to have an effect upon the sediment area 216 (mitigating scouring) that may be located proximate to the suction pile 204, for example proximate the top portion of the suction pile 204. Accordingly, when the sediment area 216 located near the suction pile 204 is stabilized, the foundation integrity of the suction pile 204 may be ensured. Additionally, such suction pile foundation systems in accordance with the present disclosure may provide for maximum frictional contact (skin contact) between the soil sediment 216 and the outer surface of the suction pile 204 while also providing scour protection.
In one or more embodiments, the metal plate 206 may provide a rigid connection facilitated by welding, bolting, clamping, or any other type of connection that provides a sturdy and rigid connection. The rigid connection may act to securely connect the metal plate 206 to both the suction pile 204 and the enclosure 202. In one or more embodiments, the enclosure 202 may include internal structures 220 to provide strength and stiffness to the enclosure 202. The internal structures may be any suitable structure to provide strength and stiffness to the enclosure without significantly impacting the load carrying capacity of the pile, for example vertical metal plates, metal vertical fins, or radial struts. In one or more embodiments, the internal structures 220 may allow for at least 90% surface contact between the soil sediment 216 and the outer surface of the pile 204 disposed below the seabed 210, at least 95%, or at least 99%, on the same basis.
As shown in
A driven pile 304 may be a column designed to transmit surface loads to low-lying soil or bedrock. Loads may be transmitted by friction between the driven pile 304 and the seabed 308 or by point bearing through the end of the driven pile 304, where the driven pile 304 may transfer the load through a soft soil to an underlying firm stratum. The actual amount of frictional resistance or end bearing may depend on the particular site conditions. In one or more embodiments, the driven pile 304 may be utilized as a foundation system for fixed platforms (jackets), tension-leg platforms (TLP), semisubmersible platforms; floating production, storage and offloading (FPSO) facilities, buoys, among other subsea components.
As shown in
The metal plate 306 may provide additional protection from scouring at the top of the driven pile 304. The enclosure 302 reduces or eliminates the effect of scouring forces upon the soil sediment 310 proximate the driven pile 304, such soil sediment 310 stabilizes and provides at least a portion of the load carrying capacity of the driven pile 304 thus ensuring the foundation integrity of the driven pile 304. The maximum axial dimension, Le 313, or depth of the enclosure 302 may extend beyond the actual and/or predicted scouring line 312. This may prevent the occurrence of ice, wave and current forces reaching the area proximate the top of the driven pile 304, thus protecting the soil sediment 310. As previously discussed, the metal plate 306 may provide a rigid connection between the enclosure 302 and the driven pile 304.
As shown in
A scouring protection system may be utilized to provide protection to a pile system embedded within an ocean seafloor. A scouring system may implement an enclosure disposed circumferentially around a pile and connected to the pile via a plate installed at the top of the enclosure and the pile. Such a scouring protection system provides the advantage of protecting the seabed between the enclosure and the pile from scouring. In particular, both the pile and sediment area located immediately adjacent to the pile may not succumb to the adverse effects of scouring.
While the present disclosure may be susceptible to various modifications and alternative forms, the one or more embodiments described herein have been shown only by way of example. However, it should again be understood that the present disclosure is not intended to be limited to the particular embodiments disclosed herein. Indeed, the present disclosure includes all alternatives, modifications, and equivalents falling within the true spirit and scope of the appended claims.
This application claims the benefit of U.S. Provisional Application No. 61/936,758, filed Feb. 6, 2014, the entirety of which is incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 61936758 | Feb 2014 | US |
