AU2017248492B1

AU2017248492B1 - Lifting structure, work boat, and method for installing pivot anchor

Info

Publication number: AU2017248492B1
Application number: AU2017248492A
Authority: AU
Inventors: Tatsuya Kimura
Original assignee: JAPAN LANDCARE TECHNOLOGIES CO Ltd
Current assignee: JAPAN LANDCARE TECHNOLOGIES Co Ltd
Priority date: 2016-12-29
Filing date: 2017-10-19
Publication date: 2018-07-05
Anticipated expiration: 2037-10-19
Also published as: JP2018109340A; JP6252882B1; TW201823556A; KR20180078135A; JP2018109343A; JP6202658B1

Abstract

A lifting structure is provided, which makes it possible to upwardly pull an object installed at the bottom of water, more reliably and at a high operation efficiency irrelevant to a state of the bottom of water. A lifting structure for lifting an object installed at a bottom of water comprises a lifting apparatus which has a lifting axis and which lifts the object along the lifting axis; a reaction force plate which has a bottom surface configured to press the bottom of water in a case that the object is lifted by the lifting apparatus; and a connecting portion which connects the lifting apparatus and the reaction force plate so that the bottom surface is rotatable with respect to the lifting axis.

Description

LIFTING STRUCTURE, WORK BOAT, AND METHOD FOR INSTALLING

PIVOT ANCHOR

RELATED APPLICATIONS

[0001] This application claims priority from Taiwanese Patent Application No. 105143774 filed on 29 December 2016 and Japanese Patent Application No. 2017-035339 filed on 27 February 2017, the contents of both of these applications are incorporated herein by reference.

TECHNICAL FIELD

[0002] The present invention relates to a lifting structure which is provided with a lifting apparatus, a work boat which is provided with the lifting structure, and a method for installing a pivot anchor based on the use of the lifting structure.

BACKGROUND ART

[0003] In recent years, the aquatic mega-solar (the floating mega-solar power plant), in which solar panels are arranged on the water surface, is progressively installed. In the case of the aquatic mega-solar, the solar panels, which float on the water surface, are connected by wires to anchors which are installed at the bottom of water (also referred to herein as the water floor), and the solar panels are retained at constant positions on the water surface. A pivot anchor is also used as the anchor which is installed at the bottom of water.

[0003a] A person skilled in the art would understand that the reference to the bottom of water in the present specification to mean land underlying water (also referred to herein as a water floor) and may include the bottom of any body of water, such as a seabed, a lakebed, a riverbed, the floor of a pond and the like.

[0004] An example of the pivot anchor (the pivoting anchor) is as depicted in Fig. 8(a). The pivot anchor has such a structure that an anchor portion 91 and a rod portion 92 are pivotably connected to one another at a connecting portion 91P.

[0005] When the pivot anchor 90 is installed, one end of a hammering rod (a drive rod) 93 is inserted into a hole 91h formed in the anchor portion 91. A pressing force is applied from the other end of the hammering rod 93, and the anchor portion 91 and a part of the rod portion 92 are hammered into (driven into) the earth or ground (Fig. 8(b)). Subsequently, the hammering rod 93 is drawn out (Fig. 8(c)), and the part of the rod portion 92, which remains on the ground, is pulled upwardly by using, for example, a hydraulic jack. The tensile force allows the anchor portion 91 to pivot with respect to the rod portion 92, and the anchor portion 91 is arranged so that the anchor portion 91 has the largest projected area in the direction perpendicular to the direction in which the rod portion 92 is pulled (Fig. 8(d)). Accordingly, the rod portion 92 is fixed to the ground g in a state in which the rod portion 92 has a high withdrawal resistance. Note that further details about the pivot anchor are described, for example, in Patent Document 1.

[0006] A method, which is described in Patent Document 2 issued for the present applicant, is used as the method for efficiently installing a pivot anchor at the bottom of water. According to the method described in Patent

Document 2, a reaction force plate, which can be easily moved by a barge, can be used to perform, at high operation efficiencies, the hammering of the anchor portion into the bottom of water by using, for example, a hydraulic hand breaker and the upward pulling of the rod portion by using, for example, a hollow hydraulic jack.

[Citation List] [Patent Documents] [0007]

Patent Document 1: United States Patent No. 7,789,594 Patent Document 2: Japanese Patent No. 5641270 [0008] Where any or all of the terms "comprise", "comprises", "comprised" or "comprising" are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, steps or components.

[0009] A reference herein to a patent document or any other matter identified as prior art, is not to be taken as an admission that the document or other matter was known or that the information it contains was part of the common general knowledge as at the priority date of any of the claims .

SUMMARY OF THE INVENTION

[0010] It has been also found out that the operation is not easy depending on the state of the bottom of water in the operation for installing the pivot anchor.

[0011] Embodiments of the invention may provide a lifting structure, a work boat provided with the lifting structure, and a method for installing a pivot anchor based on the use of the lifting structure which make it possible to upwardly pull an object installed at the bottom of water, more reliably and at a high operation efficiency irrelevant to a state of the bottom of water.

[0012] According to one aspect of the present invention, there is provided a lifting structure for lifting an object installed at a water floor, the lifting structure comprising: a lifting apparatus which has a lifting axis and which lifts the object along the lifting axis; a reaction force plate which has a bottom surface configured to press the water floor in a case that the object is lifted by the lifting apparatus; and a connecting portion which connects the lifting apparatus and the reaction force plate so that the bottom surface is rotatable with respect to the lifting axis, wherein the lifting apparatus, which is rotatable with respect to the reaction force plate, has a center of rotation which is disposed in a plane including the bottom surface of the reaction force plate or on a side of the plane opposite to a side on which the lifting apparatus is positioned.

[0013] A penetrating portion which ranges between the bottom surface of the reaction force plate and an upper surface of the reaction force plate opposed to the bottom surface may be formed in the reaction force plate; and the lifting apparatus and the reaction force plate may be connected so that the lifting apparatus lifts the object via the penetrating portion.

[0014] The penetrating portion may be a cutout which extends from an edge of the reaction force plate.

[0015] The connecting portion may define a guide space adopted to guide the object to the lifting apparatus, between the lifting apparatus and the reaction force plate.

[0016] The connecting portion may include a plurality of legs which extend upstandingly from the reaction force plate, and a plate portion which is retained in parallel to the reaction force plate by the legs and which has an opening; and the guide space may be defined among the plurality of legs, the plate portion, and the reaction force plate.

[0017] The connecting portion may be configured such that a dimension of the guide space in a direction orthogonal to the bottom surface of the reaction force plate is changeable.

[0018] The connecting portion and the reaction force plate may be detachable.

[0019] The lifting apparatus may be a hollow hydraulic jack.

[0020] There is also disclosed herein, a lifting structure for lifting an object installed at a bottom of water, the lifting structure comprising: a lifting apparatus which has a lifting axis and which lifts the object along the lifting axis; a reaction force plate which has a bottom surface configured to press the bottom of water in a case that the object is lifted by the lifting apparatus; and a connecting portion which connects the lifting apparatus and the reaction force plate so that the bottom surface is rotatable with respect to the lifting axis, wherein the connecting portion defines a guide space adopted to guide the object to the lifting apparatus, between the lifting apparatus and the reaction force plate.

[0021] There is also disclosed herein, a lifting structure for lifting an object installed at a bottom of water, the lifting structure comprising: a lifting apparatus which has a lifting axis and which lifts the object along the lifting axis; a reaction force plate which has a bottom surface configured to press the bottom of water in a case that the object is lifted by the lifting apparatus; and a connecting portion which connects the lifting apparatus and the reaction force plate so that the bottom surface is rotatable with respect to the lifting axis, wherein the connecting portion and the reaction force plate are detachable.

[0022] According to another aspect of the present invention, there is provided a work boat for lifting an object installed at a water floor, the work boat comprising: a barge which is configured to move on water; the lifting structure as previously described herein which is connected movably with respect to the barge; and a moving mechanism which moves the lifting structure with respect to the barge.

[0023] According to yet another aspect of the present invention, there is provided a method for installing a pivot anchor wherein the pivot anchor, which has an anchor portion and a rod portion connected pivotably to the anchor portion, is installed at a water floor, the method for installing the pivot anchor comprising: driving the anchor portion into the water floor; arranging the lifting structure as described herein at the water floor by grounding the reaction force plate of the lifting structure on the water floor; and lifting the rod portion by the lifting apparatus of the lifting structure to pivot the anchor portion.

[0024] In the method for installing the pivot anchor, the arranging of the lifting structure at the bottom of water may include engaging the lifting apparatus and the rod portion, and rotating the reaction force plate with respect to the lifting apparatus to ground the reaction force plate on the bottom of water.

[0025] According to the lifting structure, the work boat provided with the lifting structure, and the method for installing the pivot anchor based on the use of the lifting structure of the present invention, it may be possible to upwardly pull the object installed at the bottom of water, more reliably and at a high operation efficiency irrelevant to the state of the bottom of water.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]

Fig. 1 is a perspective view depicting a work boat according to an embodiment of the present invention including a lifting structure according to an embodiment of the present invention.

Fig. 2(a) is a perspective view depicting a hollow hydraulic jack included in the lifting structure. Fig. 2 (b) illustrates a method for lifting a lifting rod by using the hollow hydraulic jack depicted in Fig. 2(a).

Fig. 3 is a flow chart illustrating a method for installing a pivot anchor according to an embodiment of the present invention.

Figs. 4(a), 4(b) and 4(c) illustrate the contents of the operation of the pivot anchor driving step.

Figs. 5(d) and 5(e) illustrate the contents of the operation of the lifting structure installing step, and Fig. 5(f) illustrates the contents of the operation of the rod portion lifting step.

Fig. 6 is a diagram for explaining a more desirable dimension of a guide space.

Fig. 7 is a perspective view depicting a lifting structure according to a modified embodiment of the present invention.

Figs. 8(a), 8(b), 8(c) and 8(d) illustrate the procedure to install the pivot anchor into the earth or ground.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

[0027] <Embodiments>

An explanation will be made about a lifting structure 2, a work boat 100 provided with the lifting structure 2, and a method for installing a pivot anchor based on the use of the work boat 100 according to embodiments of the present invention, as exemplified by a case in which the pivot anchor is installed at an inclined bottom of water by using them. Note that for example, MANTA RAY (trade name) produced by Foresight Products can be used as the pivot anchor. However, there is no limitation thereto.

[0028] As depicted in Fig. 1, the work boat 100 of this embodiment principally has a barge 1 which includes an outboard motor (an outboard engine) 14, and the lifting structure 2 which is connected to the barge 1 by the aid of a wire W. In Fig. 1, the barge 1 floats on the water surface, and the lifting structure 2 is grounded on the bottom of water.

[0029] In the following explanation, the direction, in which the outboard motor 14 is positioned in Fig. 1, is designated as the back side of the work boat 100 and the barge 1, and the side opposite thereto (lower-left side in Fig. 1) is designated as the front side of the work boat 100 and the barge 1. Further, the horizontal direction which is orthogonal to the front-back direction, is designated as the widthwise direction of the work boat 100 and the barge 1.

[0030] The barge 1 principally has an upper board (upper deck) 11, a pair of floats 12 which are arranged under the upper board 11, a mast 13 which extends upwardly from a substantially central portion of the upper board 11, and the outboard motor 14 which is attached to a side surface of the upper board 11.

[0031] The upper board 11 is a substantially U-shaped flat plate. The upper board 11 has a cutout IS which is disposed at a central portion in the widthwise direction and which is directed backwardly from the front end.

[0032] Each of the pair of floats 12 is a hollow floating member having a substantially rectangular parallelepiped shape. The floats 12 are attached to the lower surface of the upper board 11 so that the cutout IS is interposed in the widthwise direction, while directing the longitudinal direction in the front-back direction.

One float 12 is attached to the upper board 11 along one edge in the widthwise direction of the upper board 11, and the other float 12 is attached to the upper board 11 along the other edge in the widthwise direction of the upper board 11.

[0033] The mast 13 includes a pair of poles 13a which are fixed perpendicularly to the upper surface of the upper board 11, and a beam 13b which extends in parallel to the upper board 11 while connecting upper end portions of the pair of poles 13a. The mast 13 strides across the cutout IS in the widthwise direction. A hydraulic gauge G is attached to one pole 13a of the mast 13. A winch (moving mechanism) 15 is attached to the center in the widthwise direction of the beam 13b.

[0034] The outboard motor 14 is attached to the back edge of the upper board 11. The outboard motor 14 may be any engine for the small ship or boat.

[0035] Other than the above, the barge 1 is provided with a hydraulic power unit 40 which is installed on the upper board 11. The hydraulic power unit 40 is used as a hydraulic pressure (oil pressure) source for a hollow hydraulic jack 23 and a hydraulic breaker 50 described later on.

[0036] The lifting structure 2 principally includes a reaction force plate 21, a connecting portion 22 which is provided on the upper surface of the reaction force plate 21, and the hollow hydraulic jack 23 which is rotatably (swingably, pivotally) connected to the connecting portion 22 .

[0037] The reaction force plate 21 is a plate member having a bottom surface 211 which is to be brought in tight contact with the bottom of water during the lifting operation based on the use of the hollow hydraulic jack 23. In this embodiment, the reaction force plate 21 is a flat plate which is formed of a metal such as iron, stainless steel or the like. The reaction force plate 21 is substantially U-shaped, and the reaction force plate 21 has a cutout 2S which extends in a predetermined direction.

[0038] The connecting portion 22 includes four legs 221a, 221b, 221c, 221d which extend upstandingly from the reaction force plate 21, a horizontal plate portion 222 which is retained horizontally by the four legs 221a to 221d, and a pair of vertical plate portions 223 which extend upstandingly from the upper surface of the horizontal plate portion 222.

[0039] Two of the legs 221a to 221d are provided on each of the both sides of the cutout 2S. The legs 221a, 221b are connected to the reaction force plate 21, on one side of the cutout 2S, along the direction in which the cutout 2S extends. The legs 221c, 221d are connected to the reaction force plate 21, on the other side of the cutout 2S, along the direction in which the cutout 2S extends.

[0040] The horizontal plate portion 222 is a square or a rectangle. The horizontal plate portion 222 is integrally connected at four corners thereof to the respective upper ends of the four legs 221a to 221d. Accordingly, the horizontal plate portion 222 is retained in parallel to the reaction force plate 21 over or above the cutout 2S of the reaction force plate 21. A through-hole H, which penetrates through the horizontal plate portion 222 in the thickness direction, is provided at a central portion of the horizontal plate portion 222. Note that, although the shape of the through-hole H is rectangular in Fig. 1, the through-hole H may be any shape including, for example, squares and circles.

[0041] A rectangular parallelepiped-shaped guide space GS is defined by the four legs 221a to 221d, the upper surface of the reaction force plate 21, and the lower surface of the horizontal plate portion 222. The guide space GS is communicated with the outside of the guide space GS via the cutout 2S, the through-hole H, and the gaps formed between the adjoining two of the legs 221a to 221d.

[0042] The cutout 2S of the reaction force plate 21, the guide space GS, and the through-hole H are overlapped with each other, as viewed in the direction orthogonal to the reaction force plate 21. Details of the dimension of the guide space GS will be described later on. However, it is desirable that the outer shape of the guide space GS is larger than the outer shape of the hollow hydraulic jack 23 in the plane parallel to the reaction force plate 21. It is desirable that size of the outer shape of the guide space GS is the same as that of the cutout 2S, or the cutout 2S is larger than the outer shape of the guide space GS .

[0043] The pair of vertical plate portions 223 are opposed to one another while interposing the through-hole H of the horizontal plate portion 222 in the direction orthogonal to the direction in which the cutout 2S extends. A slit S is provided for each of the pair of vertical plate portions 223. Each of the slits S is circular arc-shaped. In this embodiment, the center So of the circular arc is positioned in the plane including the bottom surface 211 of the reaction force plate 21.

[0044] The hollow hydraulic jack 23 is a lifting apparatus for performing the lifting for the pivot anchor or the like. As depicted in Fig. 2(a), the hollow hydraulic jack 23 has a cylindrical hollow cylinder 231 and a socket 232 which is provided on one end side of the hollow cylinder 231.

[0045] A hole 231h, which extends along the central axis (lifting axis) A, is defined at a central portion in the radial direction of the hollow cylinder 231. A ring-shaped piston (not depicted) is accommodated in the hollow cylinder 231.

[0046] The socket 232 has a cup-shaped form which is open on the side opposite to the side on which the hollow cylinder 231 is positioned. The socket 232 has, at a bottom portion thereof, a circular small hole 232h having the center of the central axis A. The cross-sectional shape of the inner surface 232i (Fig. 2(b)) of the socket 232 is a circular shape having the center of the central axis A. The diameter thereof is small at lower positions (positions near to the hollow cylinder 231), and the diameter is increased gradually upwardly as separating far from the hollow cylinder 231. That is, the inner surface 232i of the socket 232 is formed to have a tapered shape (Fig. 2 (b)) .

[0047] The unillustrated piston disposed in the hollow cylinder 231 is connected to the socket 232. When the piston is moved in the direction of the central axis A, the socket 232 is also moved in the direction of the central axis A.

[0048] A pair of bosses b, which mutually protrude toward the opposite sides, are fixed on the outer circumferential surface of the hollow cylinder 231 disposed in the vicinity of the end portion on the side opposite to the side on which the socket 232 is positioned. The hollow hydraulic jack 23 is rotatably connected to the reaction force plate 21 and the connecting portion 22 by inserting the pair of bosses b into the pair of slits S of the vertical plate portions 223 of the connecting portion 22.

[0049] The rotation of the hollow hydraulic jack 23 has the following feature.

[0050] Each of the slits S is circular arc-shaped. Each of the centers So of the circular arcs is positioned in the plane which includes the bottom surface 211 of the reaction force plate 21. Therefore, the hollow hydraulic jack 23 is rotated (swang, pivoted) in the direction in which the cutout 2S extends, about the axis of rotation X (Fig. 1) which connects the pair of centers So, in accordance with the sliding of the bosses b in the slits S. Note that the axis of rotation X is orthogonal to the direction in which the cutout 2S extends, in the plane which includes the bottom surface 211 of the reaction force plate 21.

[0051] The range of the rotation of the hollow hydraulic jack 23 is arbitrary. However, for example, the range is about 5° to 30° on the both sides respectively on the basis of the position at which the central axis A is perpendicular to the reaction force plate 21. It is desirable that the central axis A passes through the guide space GS and the cutout 2S in all of the range. However, there is no limitation thereto.

[0052] The wire W, which extends from the winch 15 attached to the mast 13 of the barge 1, has the end portion which is connected to the reaction force plate 21 of the lifting structure 2. The direction in which the cutout 2S of the lifting structure 2 extends and the direction of rotation of the hollow hydraulic jack 23 are coincident with the front-back direction of the barge 1 in the state in which the barge 1 and the lifting structure 2 are connected to one another. Further, the direction, in which the axis of rotation X of the hollow hydraulic jack 23 of the lifting structure 2 extends is coincident with the widthwise direction of the barge 1. The cutout IS of the upper board 1 of the barge 1 and the cutout 2S of the reaction force plate 21 have the extending directions which are coincident with each other, and the cutout IS of the upper board 1 of the barge 1 and the cutout 2S of the reaction force plate 21 are overlapped with each other in the upward-downward direction.

[0053] Next, an explanation will be made about a method for installing the pivot anchor of this embodiment with reference to a flow chart of Fig. 3, and Figs. 4(a) to 4(c) and Figs. 5(d) to 5(f).

[0054] As depicted in Fig. 3, the method for installing the pivot anchor of this embodiment includes a mark arranging step Si of arranging a mark to indicate the position of installation of the pivot anchor at the bottom of water, a pivot anchor hammering step (a pivot anchor driving step) S2 of hammering (driving) the pivot anchor at the mark position, a lifting structure arranging step S3 of arranging the lifting structure 2 at the bottom of water, a rod portion lifting step S4 of lifting the rod portion of the pivot anchor by the lifting structure 2, and a withdrawal resistance measuring step S5 of measuring the withdrawal resistance of the pivot anchor.

[0055] In the mark arranging step SI, the mark M, which indicates the position of installation of the pivot anchor 90, is arranged at the bottom of water B. As for the mark M, for example, it is possible to use a bamboo pole in which a flag is attached to one end and a reinforcing steel (steel rod, steed bar) is combined to the other end. The reinforcing steels of the marks M are successively inserted into the places of the bottom of water B at each of which the pivot anchor 90 is to be hammered, while leading a diver by using a GPS surveying instrument and an optical surveying instrument. When the marks M are arranged, the positions of the bottom of water B, at each of which the pivot anchor 90 is to be installed, can be thereby grasped with ease by visually recognizing the flags on the water surfaces .

[0056] In the pivot anchor hammering (driving) step S2, the pivot anchor 90 is hammered at (driven into) the position of the bottom of water B indicated by the mark M. An example of the specified procedure is as follows.

[0057] At first, the work boat 100 is moved to the position of the mark M, and the work boat 100 is stopped in a state in which the mark M is positioned at the inside of the cutout IS of the barge 1 and the cutout 2S of the lifting structure 2 (Fig. 4(a)). In this situation, the front-back direction of the work boat 100 is allowed to coincide with the inclination direction of the bottom of water B.

[0058] Subsequently, as depicted in Fig. 4(b), the upper end portion of a hammering rod (a drive rod) 93 is retained by a hydraulic hand breaker 50. Further, the lower end portion of the hammering rod 93 is inserted into the hole 91h (Fig. 8(a)) of the anchor portion 91 of the pivot anchor 90, and the anchor portion 91 is pushed into the position of the bottom of water B indicated by the mark M. In this situation, the direction of rotation of the rod portion 92 is allowed to coincide with the front-back direction of the work boat 100 (i.e., the direction in which the cutout 2S of the lifting structure 2 extends and the direction of rotation of the hollow hydraulic jack 23).

[0059] After that, when the hydraulic hand breaker 50 and the hydraulic power unit 40 on the barge 1 are connected by a hydraulic hose (not depicted) to operate the hydraulic hand breaker 50 so that the pressing force is applied vertically in the downward direction, the hydraulic hand breaker 50 hammers the anchor portion 91 of the pivot anchor 90 vertically in the downward direction (Fig. 4(c)). After the hammering is completed, the hydraulic hand breaker 50 and the hammering rod 93 are removed.

[0060] Note that in the method for installing the pivot anchor of this embodiment, a ring portion 92c is provided at the end portion of the rod portion 92 of the pivot anchor 90, and the lifting rod 94 made of metal is detachably connected to the ring portion 92c. The lifting rod 94 is connected to the rod portion 92 by, for example, engaging a hook or the like with the ring portion 92c, the hook being provided at one end of the lifting rod 94 and being equipped with a lock.

[0061] In the lifting structure arranging step S3, the lifting structure 2 is arranged at the bottom of water B in order to lift the pivot anchor 90 by using the hollow hydraulic jack 23.

[0062] Specifically, at first, the barge 1 is slightly moved frontwardly to make the adjustment so that the lifting rod 94, which extends substantially vertically, is disposed closely to the central axis A of the hollow cylinder 231 of the hollow hydraulic jack 23.

Subsequently, the wire W is let out by the winch 15 of the barge 1 to move the lifting structure 2 downwardly. The lifting rod 94 is allowed to pass through the hole 231h of the hollow cylinder 231 of the hollow hydraulic jack 23 (Fig. 5(d)), and the reaction force plate 21 is grounded on the bottom of water B (Fig. 5(e)).

[0063] In this situation, when the lifting rod 94 is passed through the hole 231h of the hollow cylinder 231, the upper end portion of the lifting rod 94 is introduced into the hole 231h via the cutout 2S, the guide space GS, and the through-hole H.

[0064] The rod portion 92 of the pivot anchor 90 is rotatable in the front-back direction of the work boat 100, i.e., the direction in which the cutout 2S extends. The lifting rod 94, which is connected to the rod portion 92 by the aid of the ring portion 92c, is also rotatable in the same manner. Therefore, the upper end of the lifting rod 94 can be easily introduced into the cutout 2S by rotating the lifting rod 94 in the direction in which the cutout 2S extends. After that, the upper end of the lifting rod 94 can be easily introduced into the guide space GS via the space between the leg 221a and the leg 221c.

[0065] Further, when the upper end of the lifting rod 94 is introduced from the guide space GS into the hole 231h, then the guide space GS is visually recognized from the spaces between the legs 221a to 221d, the upper end of the lifting rod 94 is easily guided into the through-hole H, and then the upper end of the lifting rod 94 can be easily guided to the hole 231h.

[0066] As depicted in Figs. 5(d) and 5(e), if the bottom of water B is inclined so that the depth of water on the back side of the work boat 100 is deeper than the depth of water on the front side, the front end side of the reaction force plate 21 is firstly brought in contact with the bottom of water B when the reaction force plate 21 is grounded on the bottom of water B. After that, the reaction force plate 21 is inclined as the back end side is further moved downwardly, and the back end side is finally brought in contact with the bottom of water B.

Accordingly, the reaction force plate 21 is grounded while making tight contact with the inclined bottom of water B.

[0067] The work boat 100 is arranged so that the front-back direction thereof is directed in the inclination direction of the bottom of water B. Therefore, the direction of rotation of the hollow hydraulic jack 23 is also coincident with the inclination direction of the bottom of water B. Therefore, the reaction force plate 21 can be grounded on the inclined bottom of water B, while vertically retaining the central axis A of the hollow cylinder 231 of the hollow hydraulic jack 23 by rotating the hollow hydraulic jack 23 in response to the inclination of the reaction force plate 21.

[0068] In the rod portion lifting step S4, the lifting rod 94 is lifted by using the hollow hydraulic jack 23, and the pivot anchor 90 is fixed to the bottom of water B.

[0069] Specifically, at first, the hollow hydraulic jack 23 and the hydraulic power unit 40 on the barge 1 are connected to one another by the hydraulic hose (not depicted). Accordingly, it is possible to apply the hydraulic pressure to the inside of the hollow cylinder 231. Further, the hollow hydraulic jack 23 and the hydraulic gauge G arranged on the barge 1 are also connected to one another by the hydraulic hose (not depicted). Accordingly, the load, which is applied to the piston in the hollow cylinder 231 as well as the socket portion 232 can be read by the hydraulic gauge G arranged on the barge 1.

[0070] When the rod portion 92 of the pivot anchor 90 is lifted, as depicted in Fig. 2(b), two wedge-shaped sandwitching members 233 are arranged in the socket 232 so that the lifting rod 94, which is connected to the rod portion 92, is sandwitched by the sandwitching members 233. For example, the wedge-shaped sandwitching member 233 has such a shape that a circular truncated cone is divided into two along with the central axis. In the state in which the wedge-shaped sandwitching members 233 are arranged in the socket 232, the outer surface 233o is brought in contact with the inner surface 232i of the socket 232, and the inner flat surface 233i is brought in contact with the lifting rod 94.

[0071] In this arrangement, the inner flat surface 233i of the wedge-shaped sandwitching member 233 is processed so that the sliding movement is suppressed with respect to the lifting rod 94. Therefore, when the socket 232 is moved upwardly in this state, then the two wedge-shaped sandwitching members 233, which are arranged while sandwitching the lifting rod 94, are pressed inwardly in the radial direction by the inner circumferential surface 232i of the socket 232 having diameters decreased gradually downwardly, and the lifting rod 94 is sandwitched more rigidly or tightly. The wedge-shaped sandwitching members 233 are also pressed upwardly simultaneously therewith. Therefore, the lifting rod 94, which is sandwitched by the wedge-shaped sandwitching members 233, is also lifted upwardly. Accordingly, the rod portion 92, which is connected to the lifting rod 94, is lifted, the anchor portion 91 of the pivot anchor 90 is pivoted, and the pivot anchor 90 is fixed to the bottom of water B (Fig. 5(f)).

[0072] When the rod portion 92 is lifted, the rod portion 92 and the lifting rod 94 are moved upwardly. The ring portion 92c of the rod portion 92 and the hook equipped with the lock of the lifting rod 94 connected thereto are moved upwardly in the cutout 2S and the guide space GS. In this way, the provision of the guide space GS suppresses the collision between the hollow cylinder 231, and the ring portion 92c and the hook equipped with the lock.

[0073] Note that when the rod portion 92 is lifted, the value of the load indicated by the hydraulic gauge G is checked on the barge 1. If the value of the load indicated by the hydraulic gauge G suddenly rises, it is possible to estimate that the anchor portion 91 pivots, and the pivot anchor 90 is fixed to the bottom of water B. The communication, which is made from an operator who confirms the sudden rise of the value of the load indicated by the hydraulic gauge G on the barge 1 to a diver who operates the hollow hydraulic jack 23 in the water, can be performed by using, for example, the wireless communication in water. It is possible to correctly grasp the value of the hydraulic gauge G even when the visibility is not satisfactory in the water, by arranging the hydraulic gauge G on the barge 1 as described above.

[0074] In the withdrawal resistance measuring step S5, it is confirmed whether or not the pivot anchor 90 is installed at the bottom of water B while having the sufficient withdrawal resistance.

[0075] In the withdrawal resistance measuring step S5, the hollow hydraulic jack 23 and the wedge-shaped sandwitching members 233, which have been used in the rod portion lifting step S4, are used as they are. For example, if it is desired that 40 kN is possessed as the withdrawal resistance, the hydraulic pressure of the hollow hydraulic jack 23 is raised to confirm that the value of the load indicated by the hydraulic gauge G arrives at 40 kN. In this procedure, if the value of the load indicated by the hydraulic gauge G arrives at 40 kN without withdrawing or extracting the pivot anchor 90, it is possible to judge that the pivot anchor 90 is installed at the bottom of water B while having the sufficient withdrawal resistance (40 kN). On the other hand, if the anchor portion 91 is lifted without allowing the value of the load indicated by the hydraulic gauge G to arrive at 40 kN, it is possible to judge that the pivot anchor 90 does not have the sufficient withdrawal resistance (40 kN).

[0076] If it is confirmed that the installed pivot anchor 90 has the sufficient withdrawal resistance, the arrangement of one pivot anchor 90 is completed. The lifting structure 2 is moved upwardly by winding up the wire W by means of the winch 15, and the work boat 100 is moved to the position indicated by the next mark M. After the work boat 100 is moved to the next mark M, the second pivot anchor 90 is installed by repeating the step S2 to the step S5 described above.

[0077] The effects of the lifting structure 2, the work boat 100, and the method for installing the pivot anchor of this embodiment are summarized below.

[0078] In the case of the lifting structure 2 of this embodiment, the hollow hydraulic jack 23 is rotatably connected with respect to the reaction force plate 21.

Therefore, it is possible to more reliably lift the rod portion upwardly by using the hollow hydraulic jack (lifting apparatus) 23 at a high operation efficiency, irrelevant to the state of the bottom of water.

[0079] Specifically, for example, according to the findings of the inventor of the present invention, when the anchor portion of the pivot anchor is hammered into the bottom of water, then the rod portion not necessarily extends perpendicularly to the bottom of water, but the rod portion may have various angles other than 90° with respect to the bottom of water. In particular, when the rod portion is installed vertically at the bottom of water which is an inclined surface, the rod portion is not perpendicular to the bottom of water.

[0080] In the case of the lifting structure 2 of this embodiment, the hollow hydraulic jack 23 is connected rotatably with respect to the reaction force plate 21. Therefore, even in the case of the inclined bottom of water, the hollow hydraulic jack 23 can be arranged vertically, and the bottom surface of the reaction force plate 21 can be grounded while being brought in tight contact with the bottom of water. Further, the rod portion, which is not perpendicular to the bottom of water, can be easily pulled by the lifting structure 2 arranged as described above.

[0081] In the case of the lifting structure 2 of this embodiment, the guide space GS is defined under or below the hole 231h of the hollow cylinder 231 of the hollow hydraulic jack 23, and the guide space GS and the cutout 2S are communicated with each other. Therefore, when the lifting rod 94 is passed through the hole 231h, the cutout 2S and the guide space GS can be used as the guides. The end portion of the lifting rod 94 can be easily introduced into the hole 231h even in the water in which the visibility is unsatisfactory.

[0082] Further, the lifting structure 2 of this embodiment has the guide space GS between the reaction force plate 21 and the lower end portion of the hole 231h of the hollow cylinder 231 of the hollow hydraulic jack 23. Therefore, even when the ground is soft or not firm, and the rod portion 92 is greatly moved upwardly upon the lifting, then the ring portion 92c, which is provided at the end portion of the rod portion 92, hardly collides with the hollow hydraulic jack 23.

[0083] In the case of the lifting structure 2 of this embodiment, the lifting operation is performed for the rod portion 92 in the state in which the hollow hydraulic jack 23 is supported by the reaction force plate 21. The reaction force (force to press the bottom of water B), which is generated when the rod portion 92 is lifted, is applied to the bottom of water via the bottom surface of the reaction force plate 21 having a large areal size.

Therefore, even when the force, which is required to lift the rod portion 92, is relatively large, the force, which is applied per unit area of the bottom of water, is small. Even when the bottom of water is soft and weak, it is possible to stably receive the reaction force which is generated when the rod portion 92 is lifted. In other words, it is possible to lift the rod portion 92 without causing, for example, the penetration of the hollow hydraulic jack 23 into the bottom of water.

[0084] The lifting structure 2 of this embodiment is constructed such that the hollow hydraulic jack 23 and the reaction force plate 21 are integrally connected to one another. Therefore, no labor is required to arrange the hollow hydraulic jack 23 on the reaction force plate 21 in the water. Further, the reaction force plate 21 and the hollow hydraulic jack 23 can be simultaneously moved and/or arranged by using the barge 1.

[0085] The lifting structure 2 of this embodiment makes it possible to avoid the curling or rolling up of mud and/or slime from an area of the bottom of water B around the place of operation, by the reaction force plate 21. Thus, it is possible to secure the visibility of the diver.

[0086] The work boat 100 of this embodiment also provides the same effects as those of the lifting structure 2, because the work boat 100 is provided with the lifting structure 2. Further, the work boat 100 of this embodiment uses the barge 1 which has a light weight and which has a shallow draft. Therefore, for example, the work boat 100 can also advance to a shoal having a depth of water of about 70 centimeters. It is possible to appropriately perform the operation for hammering/withdrawing piles and anchors at the shoal.

[0087] The work boat 100 of this embodiment has the barge 1 which has the cutout IS and which has the substantially U-shaped form as viewed in a plan view, and the reaction force plate 21 which has the cutout 2S and which has the substantially U-shaped form as viewed in a plan view. The cutout IS and the cutout 2S have the areas overlapped with each other as viewed in a plan view. Therefore, according to the work boat 100 of this embodiment, the work boat 100 can be arranged just over the mark M by positioning the mark M in the cutouts IS, 2S.

The pivot anchor 90 can be correctly hammered at the position of the bottom of water B indicated by the mark M.

[0088] The method for installing the pivot anchor of this embodiment also provides the same or equivalent effects as those of the work boat 100, because the work boat 100 is used.

[0089] Modified embodiments may be adopted as follows in relation to the lifting structure 2, the work boat 100, and the method for installing the pivot anchor of this embodiment.

[0090] It is not necessarily indispensable that the lifting structure 2 is connected to the barge 1. It is also possible to use a lifting structure 2 having no barge 1, while moving the lifting structure 2 by a crane barge or the like.

[0091] In the lifting structure 2 of the embodiment described above, the reaction force plate 21 has the substantially U-shaped form having the cutout 2S. However, the shape of the reaction force plate 21 is not limited thereto. The reaction force plate 21 may have a substantially O-shaped form in which an opening is provided at a central portion of a rectangle or a square. Other than the above, it is possible to obtain a usable reaction force plate by providing an opening or a cutout having any shape for a plate member having any shape. Further, it is not necessarily indispensable that one sheet of the reaction force plate is used. It is also allowable to provide a plurality of sheets of plate portions connected to the connecting portion 22 or the hollow hydraulic jack 23. That is, any number of reaction force plates may be used, and the reaction force plate may have any shape, provided that the reaction force can be provided for the hollow hydraulic jack 23.

[0092] In the lifting structure 2 of the embodiment described above, the bottom surface 211 of the reaction force plate 21 may be a flat surface. However, there is no limitation thereto. For example, protrusions/recesses may be provided on the bottom surface 211 as means (structures) for preventing slippage. Further, a square pillar made of wood or metal may be fixed, as means (structures) for preventing slippage, to a part (for example, a part disposed along the outer edge) of the bottom surface 211 of the reaction force plate 21 so that the longitudinal direction extends along the reaction force plate 21.

[0093] In the lifting structure 2 of the embodiment described above, the slit S of the vertical plate portion 223 of the connecting portion 22 is circular arc-shaped, and the center So of the circular arc is disposed in the plane including the bottom surface 211 of the reaction force plate 21. However, there is no limitation thereto. Although any position can be adopted for the position of the center So, it is more preferable that the position of the center So is disposed on the side of the bottom surface 211 of the reaction force plate 21 opposite to the side on which the slit S (and the hollow hydraulic jack 23) is positioned or located, that is, on the side of the bottom surface 211 on which the slit S and the hollow hydraulic jack 23 are not positioned or located. More specifically, it is preferable that the shape of the slit S is determined so that the center So is disposed in the vicinity of the center of rotation of the pivot anchor 90 (i.e., the connecting portion 91P) during the use.

[0094] In the lifting structure 2 of the embodiment described above, the legs 221a to 221d of the connecting portion 22 extend upstandingly from the reaction force plate 21. However, there is no limitation thereto. The legs 221a to 221d may be inclined with respect to the reaction force plate 21. The lifting structure 2, in which the legs 221a to 221d of the connecting portion 22 are inclined with respect to the reaction force plate 21, can be preferably used for the bottom of water having a larger angle of inclination.

[0095] Further, the lengths of the legs 221a to 221d and/or the angles of the legs 221a to 221d with respect to the reaction force plate 21 may be changeable. If the lengths of the legs 221a to 221d are changeable, the following situations arise. That is, if the ground of the bottom of water is soft, then the legs 221a to 221d are lengthened so that the large upward movement of the ring portion 92c of the rod portion 92 is allowed. Further, when the lifting structure 2 is not used, then the legs 221a to 221d are shortened, and it is possible to realize a compact size of the lifting structure 2. If the angles of the legs 221a to 221d are changeable, the angles can be adjusted in response to the angle of inclination of the bottom of water. Therefore, the lifting structure 2 can be used for the bottoms of water having various angles of inclination.

[0096] The connecting portion 22 may be detachable with respect to the reaction force plate 21. Accordingly, it is possible to exchange the reaction force plate 21 depending on the firmness or hardness of the ground of the bottom of water. If the ground of the bottom of water is soft and weak, the reaction force plate 21 having a large areal size is used. If the ground of the bottom of water is firm, the reaction force plate 21 having a small areal size is used. Note that a ring or the like, which is usable to engage a hook of a crane or the like, may be provided for the reaction force plate 21 so that the reaction force plate 21, which is separated from the connecting portion 22, can be easily moved.

[0097] The gaps between the legs 221a to 221d of the connecting portion 22 may be closed by plates or the like. In this case, the gaps may be closed by using transparent plates so that the guide space GS can be visually recognized from the outside.

[0098] In the lifting structure 2 of the embodiment described above, the connecting portion 22 is constructed by the four legs 221a to 221d, the horizontal plate portion 222, and the vertical plate portions 223. However, there is no limitation thereto. The connecting portion 22 may have any structure which provides the predetermined guide space between the reaction force plate 21 and the hollow hydraulic jack 23 and which rotatably (swingably, pivotally) connects the reaction force plate 21 and the hollow hydraulic jack 23. Specifically, for example, the horizontal plate portion 222 and the vertical plate portions 223 may be supported by a cylindrical or conical cylindrical stand portion in place of the four legs 221a to 221d. In this case, the guide space is defined on the inner side of the tubal stand portion.

[0099] The dimension in the upward-downward direction (direction perpendicular to the reaction force plate 21) of the guide space defined by the connecting portion 22 is desirably such a dimension that the ring portion 92c, which is moved upwardly when the rod portion 92 is lifted, is not brought in contact with the hollow hydraulic jack 23. Specifically, the dimension may be, for example, about 50 cm to 150 cm.

[00100] The diameter in the plane parallel to the reaction force plate 21, of the guide space defined by the connecting portion 22 desirably has such a dimension that the ring portion 92c, which is moved upwardly from the lower position when the rod portion 92 is lifted, can pass through the interior of the guide space in a well-suited manner. Specifically, for example, as depicted in Fig. 6, when the hollow hydraulic jack 23 is inclined with respect to the perpendicular direction of the reaction force plate 21, if the guide space is a guide space GS1 having a diameter dl which is approximately the same as the outer diameter D of the hollow hydraulic jack 23, then it is feared that the ring portion 92c of the rod portion 92 may collide with the outer circumferential wall (for example, the plates between the legs 221a to 221d or the cylindrical or conical cylindrical stand portion) for defining the guide space GS1, and the upward movement may be inhibited.

[00101] On the other hand, if the guide space is a guide space GS2 having a diameter d2 which is larger than the outer diameter D of the hollow hydraulic jack 23, the ring portion 92c of the rod portion 92 is moved upwardly in a well-suited manner in the guide space GS2 without colliding with the outer circumferential wall for defining the guide space GS2. Thus, it is desirable that the diameter of the guide space is larger than the outer diameter D of the hollow hydraulic jack 23. It is more desirable that the diameter of the guide space is about 1.2 to 2 times the diameter D of the hollow hydraulic jack 23. Note that it is enough that the relationship of magnitude between the outer diameter D of the hollow hydraulic jack 23 and the diameter of the guide space holds at least in the direction of rotation of the hollow hydraulic jack 23.

[00102] In the lifting structure 2 of the embodiment described above, it is also allowable that the connecting portion 22 does not define the guide space GS. For example, as depicted in Fig. 7, such a connecting portion has the following structure. That is, the legs 221a to 221d are not possessed, and the horizontal plate portion 222 is directly attached to the reaction force plate 21. Further, it is also allowable that the connecting portion 22 does not have the horizontal plate portion 222. In this case, the connecting portion 22 has such a structure that the vertical plate portions 223 are directly attached to the reaction force plate 21. Other than the above, in place of the connecting portion 22, a portion described below may be used as the connecting portion. That is, a portion having any structure in which the hollow hydraulic jack 23 and the reaction force plate 21 are connected so that the bottom surface of the reaction force plate 21 is rotatable (swingable, pivotal) with respect to the central axis A. A lifting structure, in which the guide space is not formed, may be preferably used, for example, for lifting a rod portion 92 which does not have the ring portion 92c.

[00103] In the lifting structure 2 of the embodiment described above, the hollow hydraulic jack 23 is connected to the connecting portion 22 so that the hollow hydraulic jack 23 is rotatable in only one predetermined direction. However, there is no limitation thereto. A ball joint or the like may be used for the connection between the hollow hydraulic jack 23 and the reaction force plate 21, and the hollow hydraulic jack 23 may be rotatable about an arbitrary axis horizontal to the reaction force plate 21. According to this construction, when the lifting structure 2 is arranged at the bottom of water, it is unnecessary to make the adjustment so that the direction of rotation of the hollow hydraulic jack 23 is coincident with the direction of inclination of the bottom of water.

[00104] In the lifting structure 2 of the embodiment described above, the hollow hydraulic jack 23 is used as the lifting apparatus. However, there is no limitation thereto. It is enough that the lifting apparatus is an apparatus capable of lifting any member such as the rod portion 92 or the like installed at the bottom of water in the direction directed to the water surface. It is also possible to use, for example, a chain block or a winch in place of the hollow hydraulic jack 23.

[00105] In the work boat 100 of the embodiment described above, the wire W is connected to the reaction force plate 21 at the position of the center of gravity of the lifting structure 2. Therefore, it is possible to stably perform the floating and the downward movement of the lifting structure 2 by using one wire. However, the connection between the barge 1 and the lifting structure 2 may be performed by using a plurality of wires W. Further, as for the moving mechanism, a mechanism such as Lever Brock (trade name) or the like, with which the wire W is wound manually, may be used, in place of the winch 15.

[00106] In the method for installing the pivot anchor of the embodiment described above, the hammering of the pivot anchor 90 is performed on the barge 1. However, the hammering of the pivot anchor 90 may be performed in the water. For example, the hammering of the pivot anchor 90 may be performed by using a work boat disclosed in Patent Document 2.

[00107] In the method for installing the pivot anchor of the embodiment described above, the lifting rod 94 is connected to the rod portion 92 of the pivot anchor 90, and the rod portion 92 is lifted by the aid of the lifting rod 94 by using the hollow hydraulic jack 23. However, there is no limitation thereto. A wire may be used in place of the lifting rod 94. Alternatively, the rod portion 92 may be directly lifted by the hollow hydraulic jack 23 without using the lifting rod 94.

[00108] In the embodiment described above, the method for installing the pivot anchor by using the work boat 100 has been explained. However, it is also possible to use the lifting structure 2 or the work boat 100 when the pile, the anchor or the like, which has been already installed, is extracted or withdrawn. In particular, the lifting structure 2 or the work boat 100 can be preferably used to extract or withdraw the pile or the anchor which is installed while being inclined from the perpendicular state with respect to the bottom of water.

[00109] The present invention is not limited to the embodiments described above as long as the feature of the present invention is maintained. Other modes or forms, which are conceivable within the scope of the technical concept of the present invention, are also included in the scope of the present invention.

[00110] The present invention can be also defined as any of embodiment 1 to embodiment 12 described below. Each of embodiment 1 to embodiment 12 has features listed under the title of <Embodiment>. <Embodiment 1> A lifting structure for lifting an object installed at a bottom of water, the lifting structure comprising: a lifting apparatus which has a lifting axis and which lifts the object along the lifting axis; a reaction force plate which has a bottom surface configured to press the bottom of water in a case that the object is lifted by the lifting apparatus; and a connecting portion which connects the lifting apparatus and the reaction force plate so that the bottom surface is rotatable with respect to the lifting axis. <Embodiment 2>

The lifting structure according to embodiment 1, wherein : a penetrating portion which ranges between the bottom surface of the reaction force plate and an upper surface of the reaction force plate opposed to the bottom surface is formed in the reaction force plate; and the lifting apparatus and the reaction force plate are connected so that the lifting apparatus lifts the object via the penetrating portion. <Embodiment 3>

The lifting structure according to embodiment 2, wherein the penetrating portion is a cutout which extends from an edge of the reaction force plate. <Embodiment 4>

The lifting structure according to any one of embodiments 1 to 3, wherein the connecting portion defines a guide space adopted to guide the object to the lifting apparatus, between the lifting apparatus and the reaction force plate. <Embodiment 5>

The lifting structure according to embodiment 4, wherein the connecting portion includes a plurality of legs which extend upstandingly from the reaction force plate, and a plate portion which is retained in parallel to the reaction force plate by the legs and which has an opening; and the guide space is defined among the plurality of legs, the plate portion, and the reaction force plate. <Embodiment 6>

The lifting structure according to embodiment 4 or 5, wherein the connecting portion is configured such that a dimension of the guide space in a direction orthogonal to the bottom surface of the reaction force plate is changeable . <Embodiment 7>

The lifting structure according to any one of embodiments 1 to 6, wherein the connecting portion and the reaction force plate are detachable. <Embodiment 8>

The lifting structure according to any one of embodiments 1 to 7, wherein the lifting apparatus, which is rotatable with respect to the reaction force plate, has a center of rotation which is disposed in a plane including the bottom surface of the reaction force plate or on a side of the plane opposite to a side on which the lifting apparatus is positioned. <Embodiment 9>

The lifting structure according to any one of embodiments 1 to 8, wherein the lifting apparatus is a hollow hydraulic jack. <Embodiment 10> A work boat for lifting an object installed at a bottom of water, the work boat comprising: a barge which is configured to move on water; the lifting structure as defined in any one of embodiments 1 to 9 which is connected movably with respect to the barge; and a moving mechanism which moves the lifting structure with respect to the barge. <Embodiment 11> A method for installing a pivot anchor wherein the pivot anchor, which has an anchor portion and a rod portion connected pivotably to the anchor portion, is installed at a bottom of water, the method for installing the pivot anchor comprising: driving the anchor portion into the bottom of water; arranging the lifting structure as defined in any one of embodiments 1 to 9 at the bottom of water by grounding the reaction force plate of the lifting structure on the bottom of water; and lifting the rod portion by the lifting apparatus of the lifting structure to pivot the anchor portion. <Embodiment 12>

The method for installing the pivot anchor according to embodiment 11, wherein the arranging of the lifting structure at the bottom of water includes engaging the lifting apparatus and the rod portion, and rotating the reaction force plate with respect to the lifting apparatus to ground the reaction force plate on the bottom of water.

INDUSTRIAL APPLICABILITY

[00111] According to the lifting structure, the work boat, and the method for installing the pivot anchor of the present invention, it is possible to easily perform the operation for withdrawing the pile or the anchor and the operation for installing the pivot anchor, even in a disadvantageous operation environment in which the bottom of water is inclined. Therefore, according to the lifting structure, the work boat, and the method for installing the pivot anchor of the present invention, it is possible to further facilitate the effective utilization of the space on the water.

DESCRIPTION OF REFERENCE NUMERALS

[00112] 100: work boat, 1: barge, 11: upper board, 12: float, 13: mast, 14: outboard motor, 15: winch, IS: cutout, 2: lifting structure, 21: reaction force plate, 22: connecting portion, 23: hollow hydraulic jack, 40: hydraulic power unit, 50: hydraulic hand breaker, 90: pivot anchor, W: wire.

Claims

1. A lifting structure for lifting an object installed at a water floor, the lifting structure comprising: a lifting apparatus which has a lifting axis and which lifts the object along the lifting axis; a reaction force plate which has a bottom surface configured to press the water floor in a case that the object is lifted by the lifting apparatus; and a connecting portion which connects the lifting apparatus and the reaction force plate so that the bottom surface is rotatable with respect to the lifting axis, wherein the lifting apparatus, which is rotatable with respect to the reaction force plate, has a center of rotation which is disposed in a plane including the bottom surface of the reaction force plate or on a side of the plane opposite to a side on which the lifting apparatus is positioned.

2. The lifting structure according to claim 1, wherein the center of rotation of the lifting apparatus is disposed on a side of the plane, which includes the bottom surface of the reaction force plate, opposite to the side on which the lifting apparatus is positioned.

3. The lifting structure according to claim 1 or 2, wherein: a penetrating portion which ranges between the bottom surface of the reaction force plate and an upper surface of the reaction force plate opposed to the bottom surface is formed in the reaction force plate; and the lifting apparatus and the reaction force plate are connected so that the lifting apparatus lifts the object via the penetrating portion.

4. The lifting structure according to claim 3, wherein the penetrating portion is a cutout which extends from an edge of the reaction force plate.

5. The lifting structure according to claim 4, wherein the connecting portion connects the lifting apparatus and the reaction force plate such that the lifting apparatus rotates along a direction in which the cutout extends .

6. The lifting structure according to any one of claims 1 to 5, wherein the connecting portion defines a guide space adopted to guide the object to the lifting apparatus, between the lifting apparatus and the reaction force plate.

7. The lifting structure according to claim 6, wherein the connecting portion includes a plurality of legs which extend upstandingly from the reaction force plate, and a plate portion which is retained in parallel to the reaction force plate by the legs and which has an opening; and the guide space is defined among the plurality of legs, the plate portion, and the reaction force plate.

8. The lifting structure according to claim 6 or 7, wherein the connecting portion is configured such that a dimension of the guide space in a direction orthogonal to the bottom surface of the reaction force plate is changeable .

9. The lifting structure according to any one of claims 1 to 8, wherein the connecting portion and the reaction force plate are detachable.

10. The lifting structure according to any one of claims 1 to 9, wherein the lifting apparatus is a hollow hydraulic jack.

11. A work boat for lifting an object installed at a water floor, the work boat comprising: a barge which is configured to move on water; the lifting structure as defined in any one of claims 1 to 10 which is connected movably with respect to the barge; and a moving mechanism which moves the lifting structure with respect to the barge.

12. A method for installing a pivot anchor wherein the pivot anchor, which has an anchor portion and a rod portion connected pivotably to the anchor portion, is installed at a water floor, the method for installing the pivot anchor comprising: driving the anchor portion into the water floor; arranging the lifting structure as defined in any one of claims 1 to 10 at the water floor by grounding the reaction force plate of the lifting structure on the water floor; and lifting the rod portion by the lifting apparatus of the lifting structure to pivot the anchor portion.

13. The method for installing the pivot anchor according to claim 12, wherein the arranging of the lifting structure at the water floor includes engaging the lifting apparatus and the rod portion, and rotating the reaction force plate with respect to the lifting apparatus to ground the reaction force plate on the water floor.