Classifications

• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
  • E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
  • E02D5/22—Piles
  • E02D5/34—Concrete or concrete-like piles cast in position ; Apparatus for making same
  • E02D5/38—Concrete or concrete-like piles cast in position ; Apparatus for making same making by use of mould-pipes or other moulds
  • E02D5/40—Concrete or concrete-like piles cast in position ; Apparatus for making same making by use of mould-pipes or other moulds in open water
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02B—HYDRAULIC ENGINEERING
  • E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
  • E02B17/04—Equipment specially adapted for raising, lowering, or immobilising the working platform relative to the supporting construction
  • E02B17/06—Equipment specially adapted for raising, lowering, or immobilising the working platform relative to the supporting construction for immobilising, e.g. using wedges or clamping rings
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
  • E02D27/00—Foundations as substructures
  • E02D27/32—Foundations for special purposes
  • E02D27/52—Submerged foundations, i.e. submerged in open water
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
  • E02D19/00—Keeping dry foundation sites or other areas in the ground
  • E02D19/02—Restraining of open water
  • E02D19/04—Restraining of open water by coffer-dams, e.g. made of sheet piles
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
  • E02D27/00—Foundations as substructures
  • E02D27/10—Deep foundations
  • E02D27/12—Pile foundations
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
  • E02D27/00—Foundations as substructures
  • E02D27/10—Deep foundations
  • E02D27/18—Foundations formed by making use of caissons
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
  • E02D27/00—Foundations as substructures
  • E02D27/32—Foundations for special purposes
  • E02D27/42—Foundations for poles, masts or chimneys
  • E02D27/425—Foundations for poles, masts or chimneys specially adapted for wind motors masts
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
  • E02D27/00—Foundations as substructures
  • E02D27/32—Foundations for special purposes
  • E02D27/52—Submerged foundations, i.e. submerged in open water
  • E02D27/525—Submerged foundations, i.e. submerged in open water using elements penetrating the underwater ground
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
  • E02D29/00—Independent underground or underwater structures; Retaining walls
  • E02D29/06—Constructions, or methods of constructing, in water
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
  • E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
  • E02D5/22—Piles
  • E02D5/34—Concrete or concrete-like piles cast in position ; Apparatus for making same
  • E02D5/38—Concrete or concrete-like piles cast in position ; Apparatus for making same making by use of mould-pipes or other moulds
  • E02D5/44—Concrete or concrete-like piles cast in position ; Apparatus for making same making by use of mould-pipes or other moulds with enlarged footing or enlargements at the bottom of the pile

Definitions

• the example embodiment in general relates to a construction method for fixing hollow cylindrical columns for supporting an offshore marine platform thereon, which in turn is adapted to support wind turbines, bridges and marine buildings thereon, to a seabed in a marine environment, and more particularly to a method in which the hollow column is employed as a temporary cofferdam during construction of the pile cap in a dry environment, thereby lowering construction costs and improving safety.
• a type of commander base on site is needed to support the development of ocean resources that include offshore wind energy, ocean current and tidal energies, ocean fish farms, and even the building of an ocean city, etc.
• the base may be fixed to the seabed or may be configured so as to float in the water.
• a drawback of the floating-type base is that mooring the base for the purpose of anchorage is difficult where the water depth is shallower than 50m. The base drifts aimlessly if the mooring lines are broken as this would pose great danger to the public.
• a fixed base is often more desirable and offers greater safety than the floating base.
• a stationery fixed platform is desirable in that it offers riders the comfort similar to living on land, as opposed to the boat living on the floating base.
• the conventional method for fixing the hollow column to the seabed in preparation for placing a platform deck of an offshore platform thereon utilizes a plurality of piles, whereby the pile cap is typically constructed under water on the seabed.
• a temporary steel cofferdam-type of structure is used to provide a dry working environment within the interior of the hollow column.
• use of a temporary cofferdam is costly. Therefore, what is needed is a method that eliminates the temporary cofferdam so as to drastically lower both cost and construction time. Further, if there is a precast factory on land to produce parts of the platform, with the platform thereafter assembled on top of the already fixed hollow column, improved mass production capabilities and speed of construction is possible.
• An example embodiment is directed to a construction method for fixing a foundation for supporting waterborne structures such as an offshore platform to a seabed, the foundation having one or more hollow cylindrical columns that are to be fixed to the seabed, such as a seabed comprising a thick layer of soft marine deposits.
• a plurality of steel tubes are driven into the founding layer in the seabed at an installation location of the hollow column, the steel tubes having a given free length above sea level, and the hollow column is then lowered down to the seabed so that the steel tubes are within the hollow column.
• Underwater concrete is injected between the seabed and bottom of the hollow column so as to form a concrete plug.
• the interior of the hollow column is dewatered so as to be used as a cofferdam, and then the steel tubes are cut above a pile cap level or determined design level. Thereafter, concrete is injected to cast the pile cap so as to complete the foundation.
• Another example embodiment is directed to a construction method for fixing a foundation for supporting waterborne structures such as an offshore platform to a seabed, the foundation having one or more hollow cylindrical columns that are to be fixed to the seabed.
• a plurality of steel tubes is driven into the founding layer in the seabed, and the hollow column is then lowered down to the seabed so as to surround the steel tubes.
• a reinforced concrete plug is then formed in the bottom of the hollow column, the hollow column configured as a cofferdam.
• the interior of the hollow column is then dewatered, pile cap reinforcement is fixed, and then concrete is cast to form a pile cap.
• FIG. 1 is an indicative intermediate construction stage according to an example construction method of fixing a hollow column to a seabed.
• FIG. 2 is an indicative final construction stage according to an example construction method of fixing a hollow column to a seabed.
• FIG. 3 is an indicative sectional view F-F of FIG. 1.
• FIG. 4 is an indicative sectional view G-G of FIG. 1.
• FIG. 5 is an indicative elevation sectional view showing the formation of the pile cap.
• FIG. 6A is an indicative side view showing the shear key at the surface of the steel casing or steel pipe pile in a section of the pile that is expected to be embedded in the concrete plug.
• FIG. 6B is a cross-sectional view taken from line H-H in FIG. 6A to illustrate the layout of shear keys in the steel casing or steel pipe pile.
• FIG. 6C is a magnified view of a portion of the shear keys in FIG. 6A.
• FIG. 7A, 7B, 8 and 9 indicatively show three different skirting options for three different seabed geologies.
• a and/or B means that: (i) A is true and B is false; or (ii) A is false and B is true; or (iii) A and B are both true.
• the term “hollow column” refers to a hollow cylindrical column fixed to the seabed in a body of water on which a wind power turbine, marine building, and/or bridge may be mounted thereon.
• the example construction method for fixing a hollow column to the seabed includes driving steel tubes (also referred to herein as steel pipe piles or “piles” ) into the founding layer in the seabed, lowering the hollow column to the seabed so as to surround the steel tubes, and forming a reinforced concrete plug in the bottom of the hollow column, the hollow column being configured as a cofferdam.
• the interior of the hollow column is then dewatered, pile cap reinforcement is fixed, and concrete is finally cast to form a pile cap thereby completing the installation, in preparation for thereafter supporting a to-be-built platform deck of a waterborne structure such as an offshore marine platform thereon.
• the hollow column serves as the cofferdam during the construction stage, e.g., without having to employ the typical costly temporary steel cofferdam; moreover, the hollow column is part of the support structure for a waterborne structure such as an offshore marine platform. It is further both safe and efficient.
• the pile may be a steel pipe pile having a length portion within the pile cap that can be modified so as to be integrated into the reinforcement cage of the to-be-cast pile cap, to be cast in-situ.
• a temporary pile head jacking prop with level and position adjusting jacks is fixed to the top of the pile to support the hollow column.
• a monitoring camera may be used to investigate the bottom of the hollow column so as to determine if there are any large voids or gaps. If found, these voids and gaps are filled with sand gravel.
• the concrete plug that is formed is not purely for stopping water coming in, as in the conventional construction method. Rather, the concrete plug also provides support to the hollow column. This is because reinforcement steel bars are pre-installed at the bottom of the hollow column in gaps between piles. These reinforcement steel bars translate the conventional concrete plug into a reinforced concrete slab. In an alternative, the bottom part of the concrete plug extends in a radial direction a short distance. To enhance the bond between the concrete plug and the piles, an expected section of the pile that is to be embedded in the concrete plug may be welded with triangular-shaped shear keys.
• the bottom of the hollow column may be installed with a skirting.
• the skirting includes a steel plate having a diameter larger than that of the hollow column, so as to prevent an excessive loss of concrete sideways during casting of the concrete plug.
• the skirting includes a cantilever plate with stiffeners and is fixed by bolts to the bottom end of the hollow column.
• the skirting has a steel skirting board that is oriented approximately perpendicular to the cantilever.
• the skirting may be embodied as a steel ring with teething extending from the end of the hollow column.
• the skirting may be embodied as a plurality of radially-distributed L-shaped steel plates bolted to the end of the hollow column.
• the example construction method eliminates the need for a costly temporary cofferdam and also eliminates the need for underwater execution; hence, employment of the example method at an installation location substantially reduces the construction risks and substantially improves the quality of works.
• FIGS. 1-9 should be referred to for describing an example method of fixing an offshore marine platform adapted to support wind turbines, bridges and marine buildings thereon to a seabed which may include a thick layer of soft materials within a marine environment.
• the example method is based on fixing a precast, reinforced, concrete hollow cylindrical column having a diameter in a range of about 8-10m or larger to a seabed using a plurality of steel pipe piles or “piles” .
• the example embodiment suits a seabed overlain with a layer of soft material, which is common in a near shore seabed.
• FIGS. 1, 2 and 5 illustrate an example embodiment of the method as directed to a near shore application. It is understood that a person of skill in the art is capable of extending this example application to any similar type of water zones. It should be clear that the construction vessels used in this example could be of any similar construction vessels; hence, details of their function are omitted herein for purposes of brevity.
• a plurality of pile 49 are sunk at the location of hollow column 108, e.g., for example, four (4) or more steel piles 49 may be arranged within the internal space of a hollow column 108 and driven into the seabed 2 to the suitable stratum.
• the piles 49 could be oriented vertically or inclined, so long as they do not hinder the insertion of the hollow column 108 downward into seabed 2 so as to enclose the piles 49.
• stabilization bracing 119 is prepared for stabilizing each pile 49 position, e.g., bracing 119 is bolted to the piles 49 after the insertion of the hollow column 108 enclosing the group of piles 49.
• the bracing 119 can be configured in a triangular pattern or any other geometry.
• a temporary pile head jacking prop 113 with level adjusting jacks is then fixed to the top of the steel piles 49.
• the prop 113 is made by cutting the top of the steel piles 49 to a required level, then welding a thick steel plate to the pile head and placing a jack on the plate.
• an installation vessel hoists the hollow column 108, which has been precast on land, and inserts the hollow column 108 into the group of piles 49 down to the seabed 2 so that the piles 49 are arranged within the interior of the hollow column 108.
• the wall of the hollow column 108 should enclose the pile group without touching any of the piles 49.
• part of the wall of the hollow column 108 penetrates the seabed 2. Thereafter the stabilization bracing 119 is installed.
• the hollow column 108 is installed with a temporary cross frame 112, which may be fixed to the wall of the hollow column 108 by welding or bolting.
• the cross frame 112 is supported by the pile head jacking support 113, the level of which is adjustable so that the hollow column 108 level can be adjusted to the required level above sea level 1.
• a monitoring camera may be used to inspect if there are any gaps between the wall of the hollow column 108 and the seabed 2. If gaps are discovered, sand gravel is added to fill the gaps.
• a tremie pipe is then used to inject tremie concrete (underwater concrete) into the bottom of the hollow column 108 to form a concrete plug 43. Concrete plug 43 is adapted to prevent water from coming in. As shown on FIG. 1, the concrete migrates outward under a gravity effect and is confined by a skirting plate.
• the bottom end of the wall of the hollow column 108 is pre-installed with reinforcement steel bars 45, such that the conventional mass concrete plug is translated into reinforced concrete slab.
• the conventional mass concrete plug 43 serves as a small pile cap capable of supporting the weight of the hollow column 108, and its buoyancy, plus any construction loads during construction.
• the small pile cap/concrete plug 43 provides a water stop function that allows dewatering inside the hollow column 108. Accordingly, the wall of the hollow column 108 now functions in the role of a cofferdam to stop water from entering therein.
• the construction vessels can be withdrawn.
• the hollow column 108 is now standing firm in the sea and is prepared for the platform deck construction thereon.
• a plurality of lapping bars 111 may be pre-installed for connection to the platform deck.
• the steel casing is filled with reinforced concrete from the level of pile cap 44 down to the bottom of the bored hole.
• the hollow column 108 may be embodied as a singular reinforced concrete element; however, it is also possible for the hollow column 108 to be divided into several segments.
• a plurality of concrete shear keys and positioning blocks (both well known art and not shown for brevity) provided at the segment common end faces may be used to hold the segments together by pre-stressed bars. Segments can be assembled on the construction vessel and hoisted as a singular article for installation. Thereafter the procedures are similar to those described above.
• the steel pile surface (similarly the steel casing surface in a concrete bored pile configuration) has a plurality of triangular shear keys 50 welded thereto in such an orientation that the sharp angles of the shear keys 50 are pointing downward; this orientation facilitates soil layer penetration.
• These shear keys 50 may distributed on the surface of a section of the pile/casing 49A that comes into contact with the small pile cap/concrete plug 43; see FIGS. 6A-6C for example.
• Shear keys 50 in this example are embodied as small triangular-shaped pieces of metal with the sharp angles pointing downward. Although the shear keys 50 offer little resistance to the pile 49/casing being driven downward through the soil layer, the keys 50 provide great resistance to hollow column 108 downward movement; the hollow column 108 is resisted by the surface and mechanical bonds of the shear keys 50. It should be clear that the shape of the shear keys 50 is not limited to that shown in FIGS. 6A-6C; any geometric form that increases the surface area of the contact face between the steel pile 49/steel casing and small pile cap/concrete plug 43 is also feasible.
• the example embodiment is applicable to seabeds having different geological conditions, which may broadly be classified into three (3) categories: 1) a seabed composed of a soft material, mainly marine mud; 2) a seabed composed of sandy clay, and 3) a seabed formed of hard weathered rock.
• a seabed composed of a soft material mainly marine mud
• a seabed composed of sandy clay mainly kaolin
• a seabed formed of hard weathered rock a seabed formed of hard weathered rock.
• different skirting options are employed based on the category or geological condition of the seabed 2.
• FIGS. 7A and 7B indicatively show a cantilever skirting for application in soft marine deposit.
• the main function of skirting is to confine the underwater concrete within a skirting board during casting of the concrete plug (small pile cap) 43, although the skirting provides a secondary function of reducing the bearing pressure on the seabed 2 due to the increased contact area.
• FIG. 7A shows a skirting in a circular form comprising a cantilever plate 121 bolted to the bottom end of the wall of the hollow column 108, with its outer edge at a radius greater than that of hollow column 108.
• a plurality of stiffeners 123 may be distributed evenly in a circle.
• the skirting in this example further includes a skirting board 122 attached to the outer edge of the cantilever plate 121.
• the skirting may be prefabricated in factory and fixed to the bottom end of the wall of the hollow column 108 by bolts 124.
• FIG. 8 shows another skirting option for sandy seabed.
• This ring skirting comprises a steel ring 141 bolted to the bottom end of the wall of the hollow column 108. Teething 142 is attached to the steel ring 141. The teething 142 allows the wall of the hollow column 108 to penetrate into the sandy seabed, to make close contact with the seafloor so as to prevent the underwater concrete from escaping sideways during the casting of the concrete plug (small pile cap) 43.
• FIG. 9 illustrates yet another skirting option for a seabed composed of weathered rock. Any kind of penetration cannot be used, since the weathered rock is extremely hard to penetrate. It is impossible for a single skirting to cover a general uneven terrain of the seabed.
• the solution is to use a plurality of L-shaped skirting plates 131 attached to the bottom end of the wall of the hollow column 108. As shown in FIG. 9, this example skirting is divided into 64 L-shaped skirting plates 131 configured to ride over any uneven terrain in the seabed 2, thereby preventing an excessive loss of underwater concrete during casting of the concrete plug (small pile cap) 43.
• the installation and construction of marine structures or offshore platforms using the example hollow column 108 eliminates the need for a temporary cofferdam, greatly reducing cost and construction time. Additionally, using the hollow column 108 to guard off water enhances the safety of workers inside the hollow column 108.
• the formed concrete plug 43 is not merely a mass of concrete, but a specially designed, reinforced concrete plug having dual functions: a first function as a water stop and a second function as a temporary (small) pile cap supporting the hollow column 108 during the construction of the permanent pile cap 44. To enhance the first function, a skirting may be added to the end of the hollow column 108. To enhance the second function, shear keys 50 are welded to the surface of the piles 49 at the section of the piles 49A that is expected to be embedded in the concrete plug 43.
• the present invention in various embodiments, configurations, and aspects, includes components, methods, processes, systems and/or apparatus substantially as depicted and described herein, including various embodiments, sub-combinations, and subsets thereof. Those of skill in the art will understand how to make and use the present invention after understanding the present disclosure.
• the present invention in various embodiments, configurations, and aspects, includes providing devices and processes in the absence of items not depicted and/or described herein or in various embodiments, configurations, or aspects hereof, including in the absence of such items as may have been used in previous devices or processes, e.g., for improving performance, achieving ease and ⁇ or reducing cost of implementation.

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• Engineering & Computer Science (AREA)
• Structural Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Civil Engineering (AREA)
• Mining & Mineral Resources (AREA)
• Paleontology (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• Mechanical Engineering (AREA)
• Foundations (AREA)
• Piles And Underground Anchors (AREA)
• Revetment (AREA)
• Bridges Or Land Bridges (AREA)

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Publications (2)

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• 2014
  • 2014-01-15 CN CN201410018362.3A patent/CN104775446B/zh active Active
• 2015
  • 2015-01-14 SG SG11201605777XA patent/SG11201605777XA/en unknown
  • 2015-01-14 JP JP2016564370A patent/JP2017503101A/ja active Pending
  • 2015-01-14 US US15/111,889 patent/US20160340852A1/en not_active Abandoned
  • 2015-01-14 EP EP15737412.5A patent/EP3094788A4/de not_active Withdrawn
  • 2015-01-14 WO PCT/CN2015/070659 patent/WO2015106679A1/en active Application Filing
• 2016
  • 2016-01-14 HK HK16100403.3A patent/HK1212404A1/xx unknown
  • 2016-07-15 PH PH12016501403A patent/PH12016501403A1/en unknown

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