CONSTRUCTION METHOD FOR PLANTING HOLLOW COLUMNS IN A SEABED OF A MARINE ENVIRONMENT FOR SUPPORTING WATERBORNE STRUCTURES THEREON

Abstract

In a construction method for planting a hollow column (21) in a seabed (2) for supporting a waterborne structure (11) thereon, a steel tube (101) is driven into the bed (2) to the founding stratum (5), with materials of the bed (2) within tube (101) excavated and any surplus steel tube (101) cut off. A first segment (1A) is inserted into tube (101), then second/subsequent segments (2A-8A) are joined tightly to its previous segment (1A-7A) to form column (21). Pressure grouting fills gaps between the tube (101) and column (21). Upon hardening, the tube (101) and column (21) form an integral unit adapted to take loads due to a surface friction resistance present between the steel tube (101) outer surface and soil materials (4) of the seabed (2), and due to an end bearing resistance present between the base of column (21) and the founding stratum (5).

Description

BACKGROUND

1. Field

The example embodiment in general relates to a construction method for planting hollow cylindrical columns in a seabed of a marine environment for supporting a waterborne structure, such as an offshore marine platform, thereon, which in turn is adapted to support wind turbines, bridges, marine buildings and the like.

2. Related Art

Existing foundation types (excluding floating types) in a marine environment can be divided into gravity type and pile type. Large scale gravity types are further referred to as a caisson of bottom-closed type or opened type. A traditional caisson foundation requires that the load bearing stratum be close to the seafloor so that the top soft material of the seabed can be removed easily and replaced with sand fill as a regular layer for levelling and for spreading the caisson loads. The bottom-closed caisson is then sunk to sit on the levelled sand layer. Any voids inside the caisson are usually filled with sand/stone to increase the dead weight so that the caisson is more stable. An opened type caisson itself is a cofferdam before its bottom is sealed by concrete plug, after it is sunk to the seafloor. Thereafter, the construction steps are similar to the closed-bottom caisson type. Pile type foundations carry the loads in a different manner than gravity types. Pile types carry the horizontal load by bending, while the gravity type take the load by moving the gravity load center off the center of gravity (C.G.). Pile type foundations carry the vertical load by end bearing (in the case of bored piles) or by skin friction (in the case of driven piles).

Applicant's prior art China Pat. Appl. Ser. Nos. 201210038405.9 and 201200104898.8 both describe a process whereby a hard seabed or soft materials in the seabed may be dredged, and may be applied to conditions where the bedrock is close to the seabed surface. In near shore waters, especially at an estuary where thick layers of soil and sand have settled, the removal of soft soil materials is simply not feasible. Accordingly, what is needed is a method of fixing waterborne structures such as an offshore marine platform to a seabed having thick layers of soft materials that typically cannot be completely removed.

There are noted differences in a foundations as between one for an offshore platform and one for sea-crossing bridges. The aforementioned foundation types mostly result from bridge engineering. For a bridge foundation, it is typical to have a small portion of gravity (vertical) loads but a significant portion of horizontal loads generated from wind, waves and earthquakes. As a result, the overturning moment is the dominant load to resist.

Conversely, the offshore platform foundation has significant gravity loads as well as lateral (horizontal) loads, so both load cases have significant effects on the platform. The overturning moment is induced by lateral loads. To resist the bending moment in a marine environment due to a thick layer of soft material, piles are effective and relatively cheaper to use than the caisson foundation, which requires the removal of substantially all of the soft material of the seabed. The piles mobilize the skin friction resistance of the pile shaft, whereas the caisson is put in an excavated hole in the seabed where the soil is loosely in contact with the walls. As a result, the caisson wall cannot generate any meaningful friction. However, a caisson has a large end bearing resistance area, hence it is good in resisting gravity loads. The example embodiment as to be described hereafter contemplates the merits of both cases, i.e., providing a foundation which offers friction resistance of the pile type foundation, as well as end bearing resistance of the caisson.

The geological environment is also considered in contemplating the foundation type. For example, in a seabed where the bedrock level is not close to the seafloor and not too deep to be reached by piles, the foundation type to be considered should be friction piles. In those cases where the bedrock level is closer to the seafloor or not too deep to be reached by excavation, the caisson foundation is typically considered. As such, in a seabed where the load bearing stratum level (founding stratum) is not too deep to be reached by excavation, the foundation type provided by the example construction method to be described hereafter proves to be effective, as it employs both advantages of having friction resistance of the friction piles as well as end bearing resistance of the caisson.

SUMMARY

An example embodiment of the present invention is directed to a construction method for planting a foundation of one or more bottom-closed hollow columns in a seabed beneath water of a marine environment for supporting waterborne structures thereon, where the seabed includes a thick layer of soft marine deposits or soil materials. In the method, a steel tube having an internal diameter with a margin tolerance greater than the external diameter of the hollow column is driven into the seabed at the designated location until it reaches the founding stratum. Any soft deposits or material of the seabed present inside the steel tube is then excavated down to the founding stratum. A bottom-closed first segment of the hollow column is then lifted into the steel tube where it floats in the water. While the first segment is held in position, a second segment is lifted onto the first segment in an end to end relation, the first and second segments aligned via match cast positioning blocks and shear keys, where opposed, joining faces of the segments are coated with an epoxy resin or equivalent and then joined by prestressing a plurality of stressing bars threaded through the two segments. The lifting and joining process is repeated until a final segment is exposed above the water surface. In an example, the design length of each individual segment is such that the assembled hollow column is capable of floating in the water. After all segments are assembled, the hollow column is water ballasted to sink it to the bottom of the steel tube. Any gaps or cavities between the steel tube and hollow column, and between the base (or bottom slab) of the hollow column and founding stratum are filled by applying a pressure grout with underwater concrete, starting from the low point at the bottom slab and gradually pushing the front upward until the concrete and cement emerges from a gap at the seafloor. After the concrete and cement hardens or sets, the steel tube is now bonded to the hollow column and thus forms a single integral unit. This integral unit is adapted to take loads due to a surface friction resistance present between the steel tube outer surface and soil materials of the seabed, and also due to an end bearing resistance present between the base of the hollow column and the founding stratum. Any surplus of steel tube at the mud line of the seafloor/seabed is then cut and removed. Alternatively, the cutting of the steel tube can be carried out before installation of the first segment.

Another example embodiment is directed to a construction method for planting a bottom-closed hollow column into a seabed beneath water of a marine environment for supporting a waterborne structure thereon. In the method, a steel tube having an internal diameter with a margin tolerance greater than the external diameter the hollow column is driven into the seabed until it reaches the design founding level, then any soft marine materials inside the steel tube are excavated to the founding stratum. The entire hollow column is then placed as one piece into the steel tube vertically so as to float on the water, then ballasted with water until the hollow column sinks to the bottom of the steel tube. Any gaps or cavities between the steel tube and hollow column, and between the hollow column base and founding stratum are filled with a pressure grout of underwater concrete and cement. Upon hardening, the steel tube and hollow column form a single integral unit. This integral unit is adapted to take loads due to a surface friction resistance present between the steel tube outer surface and soil materials of the seabed, and also due to an end bearing resistance present between the hollow column base and the founding stratum. Any surplus of the steel tube at the mud line of the seafloor/seabed is then cut. Alternatively, the cutting of the steel tube can be carried out before the installation of the hollow column

BRIEF DESCRIPTION OF THE DRAWINGS

The example embodiment will become more fully understood from the detailed description given herein below and the accompanying drawings, wherein like elements are represented by like reference numerals, which are given by way of illustration only and thus are not limitative of the example embodiments herein.

FIG. 1 is a side view illustrating a steel tube being driven into the seabed by a vibro hammer

FIG. 2 is a side view illustrating the steel tube being driven into the founding stratum and the marine deposit inside the tube is removed.

FIG. 3 is a side view illustrating any surplus length of the steel tube being cut at the mud line level of the seabed.

FIG. 4 is a side view illustrating the platform being carried by the auxiliary floater

FIG. 5 is a side view illustrating a first segment of the hollow column being lifted into the steel tube.

FIG. 6 is a side view illustrating the joining of the hollow column segments.

FIG. 7 is a side view illustrating application of the pressure grout of underwater concrete and cement to fill the gap and cavity around the assembled hollow columns

FIG. 8 is a side view illustrating the assembled segments and casting of in-situ joints between platform and hollow columns.

FIG. 9 is a side view illustrating a completed offshore platform with assembled columns.

FIG. 10 is directed to another example embodiment and is a side view illustrating installation of a steel tube by a vibro hammer mounted on a vessel.

FIG. 11 is a side view illustrating the excavation and removal of any marine soil of the seabed inside the steel tube.

FIG. 12 is a side view illustrating a final preparation stage of the steel tube.

FIG. 13 is a side view illustrating installation of an entire hollow column with pre-installed pressure pipes.

FIG. 14 is a side view illustrating application of the pressure grout of underwater concrete and cement to fill the gap and cavity around the hollow columns.

PARTS LIST

1. Sea surface

2. Seabed/seafloor

3. Bed rock

4. Soil strata

5. Founding stratum/load bearing stratum

11. Offshore platform

21. Hollow column

22. Pre-installed pressure pipes

25. Starter bars

27. In-situ concrete

31. Auxiliary floater

32. Supporting frame

61. Opening for column insertion

62. Temporary structure to contain the hollow column segment

101. Steel tube

102. Sand/stone layer

104. Shear key

105. Vibro hammer

107. Injected concrete and cement grout

109. Surplus section of steel tube

111. Steel bracket

112. Temporary props

113. Hydraulic jack

DETAILED DESCRIPTION

As to be shown more fully below, the example embodiment is directed to a construction method for planting hollow columns in a seabed to support waterborne structures thereon. In an example to be described in detail, the method may include driving a steel tube into the seabed until reaching a designated depth, such as a founding stratum. The steel tube is employed as a temporary casing for installation of a bottom-closed hollow column, which is inserted into the steel tube after seabed materials inside the steel tube have been excavated down to the designated depth. After insertion of the hollow column, any gaps between the steel tube and hollow column are pressure filled with underwater concrete or cement grout. Upon hardening, the steel tube and hollow column form an integral unit that is able to resist or take loads generated from a friction resistance between the steel tube surface against the soil pressure of the materials in the seabed, and an end bearing resistance from the hollow column base. It can be classified as a frictional end bearing pile or a deep founding caisson, since most caissons are founded not far away from the seafloor. The operation is carried out in a dry environment, thereby lowering construction costs and improving safety.

As will be shown in more detail below, in the example method the steel tube is used as a retaining structure as any marine soil of the seabed inside the steel tube is removed, and provided support during installation of the hollow column in a dry environment. The steel tube itself becomes part of the foundation system as it is integrated with the hollow column, thereby forming an integral unit contributing its friction resistance to the load carrying capacity in addition to the end bearing capacity of the base of the hollow column, which is a caisson by definition. The load carrying mechanism will be as follows: at first the load is resisted by the end bearing of the caisson (base of hollow tube). As the load increases, this triggers the yielding of the bearing area, which immediately mobilizes the skin friction resistance from the steel tube wall. The ultimate load carrying capacity of such a system will be the end bearing capacity+skin friction resistance. Conventional pile capacity is friction resistance and that for caisson is the end bearing capacity.

Additionally, the large space inside the hollow column has significant buoyancy that compensates for a portion of the gravity loads, this in turn reduces the bearing pressure on the founding stratum. In other words, this means that the founding stratum can be located much shallower than what is needed for the conventional caisson foundation. Further, overall stability is improved, since the buried depth of the wall formed by the construction method of the present invention is supported by the lateral pressure of the overburden soil.

In an example the large space inside the hollow column can be used as storage. In one case the space may be used as a fresh water tank to store rain water which has fallen on the platform. Since the void is huge, the stored fresh water can satisfy the drinking water consumption of the staff working and living on the platform. The space in the hollow column may also be used to store oil.

The construction method described hereafter involves no complicated underwater works. The only underwater work needed, as will be seen, is in the cutting of surplus steel tube at the mud line on the seabed/seafloor.

In an example, the base or bottom slab of the hollow column is tapered with its apex pointing downward, serving as a low point of the base. This is so that the pressure grout of underwater concrete and cement at the low point of the hollow column can be facilitated to flow easily upward to fill the gap. In an example, the bottom of the excavation steel tube interior may be backfilled with a layer of sand/stone to fill any large cavity which may exist in in the founding stratum. This is in order to stop a large volume loss of injected underwater concrete and cement grout.

In an example, the hollow column is fabricated using a matched segment casting process, which as is well known consists of employing precast concrete match cast segments using the match casting process to ensure a very closely fitting joint. As known, the segments are jointed together with epoxy resin/paste or equivalent and structurally joined by post-tensioning. In the example construction method, the #i+1 match cast segment is cast against a completed #i match cast segment end to end, i.e., the so-called matched cast method commonly adapted in bridge construction. The positioning blocks and the shear keys in the completed #i segment will produce matching reversal positioning blocks and shear keys in the matched face of the #i+1 segment. The matched cast process described in the above is also applicable to stressing ducts and stressing blocks for prestressing operation.

In an example, the last segment or the end of one single-piece hollow column has starter reinforcement bars sticking out from the end for lapping the reinforcement cage of the platform for in-situ concreting. This forms a permanent joint between the hollow column and the platform.

In an example, the marine platform is precast and is transported on sea by an auxiliary floater, and the platform and floater have an opening for the insertion of a hollow column, and a mechanism to hold the hollow column in position.

In an example, brackets may be welded to the steel tube for supporting the propping to the marine platform during the forming of an in-situ concrete joint between the marine platform and the hollow column Additionally in an example, pressure pipes are pre-installed in the hollow column for injection of the underwater concrete and cement grout. Further in an example, the shear keys, which may be embodied in a triangular shape with the sharp tips pointing downward, are welded evenly to the inner face of the steel tube in order to enhance the bond between the steel tube and the hollow column.

As used herein, the phrase “present invention” should not be taken as an absolute indication that the subject matter described by the term “ is covered by either the claims as they are filed, or by the claims that may eventually issue after patent prosecution; while the term “present invention” is used to help the reader to get a general feel for which disclosures herein are believed as maybe being new, this understanding, as indicated by use of the term “present invention,” is tentative and provisional and subject to change over the course of patent prosecution as relevant information is developed and as the claims are potentially amended.

Reference throughout this specification to one example embodiment” or “an embodiment” means that a particular system, method, feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one example embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Further, the particular systems, methods, features, structures or characteristics may be combined in any suitable manner in one or more example embodiments.

The term “and/or” may be understood to mean non-exclusive or; for example, 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.

As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. The term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

In the drawings, identical reference numbers identify similar elements or acts. The size and relative positions of elements in the drawings are not necessarily drawn to scale.

Unless the context requires otherwise, throughout the specification and claims that follow, the word “comprise” and variations thereof, such as “comprises” and “comprising,” are to be construed in an open, inclusive sense, that is, as “including, but not limited to.”

As used in the specification and appended claims, the terms “correspond,” “corresponds,” and “corresponding” are intended to describe a ratio of or a similarity between referenced objects. The use of “correspond” or one of its forms should not be construed to mean the exact shape or size.

As used herein, the term “hollow column” refers to a hollow cylindrical column fixed in the seabed in a body of water on which a wind power turbine, marine building, and/or bridge may be mounted thereon.

Accordingly, the example construction method for planting a hollow column in the seabed includes driving a steel tube with an internal diameter larger than the external diameter of the hollow column into the seabed down to the founding stratum, removing the soil inside the steel tube, inserting the hollow column in the steel tube and lowering the hollow column by water ballast to the founding stratum. With the pre-installed pressure pipes, pressure grout of underwater concrete and cement are to fill the gap and cavity around the hollow column starting from the low part gradually moving upward until the underwater concrete and the cement grout emerge from the gap at the seabed. The hollow column is then fixed successfully into the seabed and is ready to be integrated with the platform. No underwater works are involved.

In an example, the platform which is floated in by an auxiliary floater may be rested on the propping supported from brackets welded to the steel tube, or rested on the brackets cast in the top end of the last segment of the hollow column Prior to the insertion of the hollow column, a monitoring camera may be used to investigate the founding stratum if there are any large voids or gaps. If found, these voids and gaps are filled with sand and gravel.

Having supported on the brackets as mentioned above and the level is set by jack action, reinforcement bars are connected to the mechanical splicers embedded at walls of the column opening in the platform, reinforcement bars are fixed and lapped to the starter bars from the top end of the last segment of the hollow column. In-situ concrete is cast for the connecting joint. After the concrete gained strength, temporary props are removed and the floater is disassemble. The platform construction is completed.

General concepts of the example embodiment having been described above, the following FIGS. 1-14 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 8-10 m or larger to a seabed using a steel tube with an internal clear diameter larger than the external diameter of the hollow column by a tolerance margin say 300 mm. The example embodiment suits a seabed overlain with a layer of soft material, which is common in a near shore seabed.

FIGS. 1-9 and 10-14 illustrate two example embodiments 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.

Initially, a plurality of steel tubes 101, each for the installation of a hollow column 21, e.g., for example, four (4) steel tubes for a platform 11, are driven into the seabed 2 to the founding stratum 5. FIG. 1 shows the steel tube 101 being driven into the seabed by a vibro hammer, represented by element 105. FIG. 2 shows the steel tube driven down to the founding stratum 5, at this point any materials (marine soil 4) of the seabed 2 that are inside the steel tube 101 have been excavated and removed. FIG. 3 shows where any surplus steel tube 109 is cut at the mud line level on the seabed 2. Alternatively, the surplus steel tube 109 may be cut after the installation of the hollow column 21.

In order to increase the bond between the inner surface of the steel tube 101 and the external surface of the hollow column 21, the steel tube 101's inner surface is welded with a plurality of triangular shear keys 104 as shown in the enlarged diagram of FIG. 2. Orientation of the triangle shear keys is with the sharp angles of the shear keys 104 being pointing downward; this facilitates penetration in soil layers. These shear keys 104 should be distributed evenly on the inner surface of steel tube 101.

Steel brackets 111 as illustrated in FIG. 2 are welded to the steel tube 101 in several layers around the expected mud line level, since the final setting level of the steel tube 101 after being hammered into the seabed 2 varies so that several layers should cover the variation to ensure that when the surplus length of the steel tube 109 is cut from the mud line at the seabed 2, at least one layer of brackets 111 can be used.

FIG. 4 illustrates a platform 11 with four (4) column openings 61 supported by an auxiliary floater 31 having been towed into position, the column center aligning with the steel tube 101 center directly underneath. FIG. 5 illustrates how a first segment 1A of the eventual hollow column 21 to be constructed is inserted through its corresponding column opening 61 in platform 11 and into steel tube 101; it is able to float in the water.

FIG. 6 illustrates where a fifth segment 5A of the eventual hollow column 21 is stacking on the end of a fourth segment 4A after segments 1A to 4A have already been assembled within steel tube 100. These segments are joined by using prestress to compress two epoxy resin-coated matching faces together. The assembled segment length (1A-4A) is designed to be able to float on the water with the added weight of the next segment, which in this case is segment 5A.

FIG. 7 illustrates a completed hollow column 21 comprising eight (8) segments 1A to 8A and the gap and cavity and void around the hollow column are filled with pressure grout of underwater concrete and cement 107. After the underwater concrete and cement grout 107 hardens, props 112 are installed on the brackets 111 around the columns 1211 supporting the platform 11. Upon hardening of the concrete/cement, the steel tube 101 and hollow column 21 form a single integral unit. This integral unit is adapted to take loads due to a surface friction resistance present between the outer steel tube 101 surface and soil materials of the seabed 2, and also due to an end bearing resistance present between the hollow column 21 base and founding stratum 5.

FIG. 8 illustrates the in-situ casting of the joint between the hollow column 21 and the platform 11. The reinforcement bar mechanical splicers (not shown) embedded in the wall of the column openings 61 are re-attached with reinforcement bars (not shown) that lap the starter bars 25 to form the reinforcement cage which is then cast with in-situ concrete 27 to complete the joint. FIG. 9 illustrates a completed platform 11 supported by hollow columns 21 integrated with their respective steel tubes 101.

Another example embodiment of the construction method is illustrated with reference to FIGS. 10-14. Namely, FIG. 10 shows a piling vessel using a vibro hammer 105 to drive a steel tube 101 down into the seabed 2 through the soft marine deposit layer 4 and reaches the firm founding stratum 5. FIG. 11 illustrates a dredger excavating and removing the soft soil materials 4 inside the steel tube 101 down to the founding stratum 5. FIG. 12 illustrates where any surplus length of the steel tube 101 above the seabed 2 level has already be cut and taken away. FIG. 13 illustrates an entire, single-piece bottom-closed hollow column 21 which floats in the water and is shown grabbed and stabilized in a vertical position by a construction vessel, so as to be navigated to a position where the center of the hollow column 21 is aligned with the center of the steel tube 101. Gradually, the grab is loosened and the hollow column 21 is ballasted with water, so that it sinks gradually into the steel tube 101 until resting at the bottom founding stratum 5 above the backfilled sand/stone layer (if any). Thereafter, the hollow column 21's level, position and verticality are maintained by the construction vessel.

FIG. 14 illustrates that while the hollow column 21 floats inside the steel tube 101 and is constrained by the construction vessel (not shown but referred to FIG. 13), a floating batching plant vessel pumps underwater concrete and cement grout into the pre-installed pressure pipes 22 to pressure fill up the gap(s) and cavity(s) between the hollow column 21 and the steel tube 101 and the gap/void between the base of bottom slab of the column 21 and the founding stratum 5. After the underwater concrete and the cement grout harden, the hollow column 21 is fixed in the seabed 2 successfully. Similar to the previous embodiment, the thick layer of soil materials 4 of the seabed 2 provide friction resistance and end bearing resistance to the hollow column 21. Namely, upon hardening of the pumped in concrete/cement grout, the steel tube 101 and hollow column 21 form a single integral unit adapted to take loads due to the surface friction resistance present between the outer steel tube 101 surface and soil materials 4 of the seabed 2, and also due to the end bearing resistance present between the hollow column 21 base and founding stratum 5. The fixing of a hollow column 21 in the thick layer of soft material in marine environment is thus completed. Platform 11 is then constructed in a similar manner.

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. The present inventive embodiment is effective in all three categories although the hollow column 21 becomes purely a caisson that carries loads in end bearing.

According to the example embodiment above, the installation and construction of marine structures or offshore platforms using the example hollow column 21 eliminates the need for a temporary cofferdam, and the using of precast hollow column 21 in segments or better in one piece greatly reduce cost and construction time. Additionally, using the hollow column 21 to store fresh water could help to solve the fresh water supply problem for the persona working and living on the platform 11.

The example embodiment having been described, it is apparent that such may have many varied applications. For example, the method of fixing the hollow column 21 into the seabed 2 as disclosed herein is not limited to the specific example embodiment described above. Various changes and modifications thereof may be effected by one skilled in the art without departing from the spirit or scope of protection. For example, elements and/or features of different illustrative embodiments could be combined with each other and/or substituted for each other within the scope of this disclosure.

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.

The foregoing discussion of the invention has been presented for purposes of illustration and description. The foregoing is not intended to limit the invention to the form or forms disclosed herein. In the foregoing Detailed Description for example, various features of the invention are grouped together in one or more embodiments, configurations, or aspects for the purpose of streamlining the disclosure. The features of the embodiments, configurations, or aspects of the invention may be combined in alternate embodiments, configurations, or aspects other than those discussed above. This method of disclosure is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment, configuration, or aspect. Thus, the following claims are hereby incorporated into this Detailed Description, with each claim standing on its own as a separate preferred embodiment of the invention.

Moreover, though the description of the invention has included description of one or more embodiments, configurations, or aspects and certain variations and modifications, other variations, combinations, and modifications are within the scope of the invention, e.g., as may be within the skill and knowledge of those in the art, after understanding the present disclosure. It is intended to obtain rights which include alternative embodiments, configurations, or aspects to the extent permitted, including alternate, interchangeable and/or equivalent structures, functions, ranges or steps to those claimed, whether or not such alternate, interchangeable and/or equivalent structures, functions, ranges or steps are disclosed herein, and without intending to publicly dedicate any patentable subject matter.

Claims

1. A construction method for planting a bottom-closed hollow column into a seabed beneath water of a marine environment, the hollow column adapted to support a waterborne structure thereon, comprising: (a) driving a steel tube having an internal diameter with a margin tolerance greater than the external diameter of the hollow column into the seabed at an installation location thereof until it reaches a founding stratum of the seabed,(b) excavating any material of the seabed that is present inside the steel tube down to the founding stratum,(c) lifting a bottom-closed first segment of the hollow column into the steel tube vertically so that it floats on the water, and while the first segment is held in position, lifting a second segment onto the first segment in an end to end relation, the first and second segments aligned via match cast positioning blocks and shear keys, where opposed, joining faces of the first and second segments are coated with an epoxy resin or equivalent and joined by a compression set up by a plurality of stressing bars threaded through a plurality of preformed ducts extending across the joining faces, and where the lifting and joining steps are repeated until a final segment is joined such that it is exposed above the water surface,(d) filling up any gaps and cavities present between the steel tube and hollow column and between a base of the hollow column and founding stratum by applying a pressure grout of underwater concrete and cement, wherein after hardening the hollow column and steel tube form an integral unit adapted to take loads due to a surface friction resistance present between the steel tube outer surface and soil materials of the seabed, and due to an end bearing resistance present between the base and the founding stratum, and(e) cutting the steel tube at a mud line level of the seabed, wherein step (e) is performed between steps (b) and (c) or alternatively after step (d).

2. The method of claim 1, wherein the base is embodied as a bottom slab that is tapered with its apex pointing downward to serve as a lowest point of the slab, thereby allowing grout egressed from the lowest point to flow and rise so as to facilitate filling the gaps and cavities around the hollow column.

3. The method of claim 1, further comprising backfilling a layer of sand or stone in the bottom interior of the steel tube.

4. The method of claim 1, wherein the hollow column is assembled from a plurality of match cast segments, anda reverse profile of shear keys are formed in a given match cast segment by casting against the face of the segment with shear keys of a completed match cast segment.

5. The method of claim 1, wherein the hollow column is assembled from a plurality of match cast segments, anda reverse profile of positioning blocks are formed in a given match cast segment by casting against the face with positioning blocks of a completed match cast segment.

6. The method of claim 1, wherein uniformly distributed shear keys, such as triangle-shaped shear keys with sharp tips pointing downward, are welded to the inner face of the steel tube to increase bonding between the steel tube and the hollow column.

7. The method of claim 1, wherein a platform of the waterborne structure includes a plurality of openings, each for insertion of a corresponding hollow column therethrough as the platform is supported on a temporary floater.

8. The method of claim 1, wherein the waterborne structure includes a platform, with the hollow columns serving to support the platform thereon as the hollow columns are casted to corresponding platform joints.

9. The method of claim 1, wherein space within the hollow columns are adapted for storage.

10. A construction method for planting a bottom-closed hollow column into a seabed beneath water of a marine environment, the hollow column adapted to support a waterborne structure thereon, comprising: (a) driving a steel tube having an internal diameter with a margin tolerance greater than the external diameter of the hollow column into the seabed at an installation location thereof until it reaches a founding stratum of the seabed,(b) excavating any material in the seabed that is present inside the steel tube down to the founding stratum,(c) placing the entire hollow column into the steel tube vertically and ballasting it with water until it sinks to a final depth at the founding stratum,(d) filling up any gaps and cavities between the steel tube and hollow column and between a base of the hollow column founding stratum by applying a pressure grout of underwater concrete and cement, where after hardening the hollow column and steel tube form an integral unit adapted to take loads due to a surface friction resistance present between the steel tube outer surface and soil materials of the seabed, and due to an end bearing resistance present between the base and the founding stratum, and(e) cutting the steel tube at a mud line level of the seabed, wherein step (e) is performed between steps (b) and (c) or alternatively after step (d).