JP2693731B2 - Offshore structure and its installation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an offshore structure constructed in a state of landing on the sea and a method for installing the offshore structure.

[0002]

2. Description of the Related Art Offshore structures constructed in a state of landing on the ocean, except for platform-type structures, are disclosed in JP-A-4-140322 and JP-A-4-1463.
It is constructed or installed so that the entire bottom surface of the structure lands on the seabed like No. 17, etc., and the bottoming state is secured by canceling the buoyancy by the weight of the structure and water ballast, but the entire bottom surface is the seabed. The structure landing on the seashore may change the tidal current in the surrounding sea area, which may affect coastal sediments and disturb the natural ecosystem.

In addition to a large difference in ebb and flow, buoyancy acting on a structure increases when the tide rises during a tsunami or high tide, and therefore a measure for preventing uplifting is required. However, JP-A-4-140322 The method of installing anchors and mooring wires on the seabed, as in JP-A-4-146317, or driving piles as in JP-A-4-146328, increases the scale of construction.

The present invention has been made by paying attention to the problem of the conventional landing structure, and it is an offshore structure that suppresses the influence on the ecosystem and does not require any special fixing means even when the tide rises. And its installation method.

[0005]

According to the present invention, an offshore structure is constructed by a plurality of pillars constructed in the sea and on the pillars.
It is composed of a part of the structure that is submerged in the sea. By floating the structure from the seabed, the tidal current under the structure is not obstructed and the impact on the ecosystem is suppressed.

The structure is composed of a bottom slab that is mounted on a pillar and a side wall that is exposed on the sea and goes around the outer periphery of the bottom slab, and the total weight of the structure is larger than the buoyancy acting on the subsea portion. And the difference in buoyancy are divided by the number of columns and the area of contact with the columns, and the pressure is set to the column in contact with the column.

The offshore structure lands on the seabed only at the pillar portion, and the structure keeps floating from the seabed, so that the natural tidal current is maintained under the bottom slab.

An opening is formed in a part of the side wall of the structure, and the level of the lower end of the opening is located below the tide level at the highest rise.

Since the level of the lower end of the opening is located below the tide level at the time of the highest rise, when the tide level rises after the completion of the offshore structure, seawater automatically enters the inside of the structure from the side wall opening. The seawater that is taken in and acts as a ballast that counteracts the increase in buoyancy that acts on the structure due to the rise in tide level, so it is possible to use a simple means on the pillar without relying on anchors, mooring wires, or piles. It prevents the structure from floating due to buoyancy.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An offshore structure 1 of the present invention, as shown in FIGS. 1 and 2, has a plurality of pillars 2 constructed in the sea, and a structure 3 constructed on the pillar 2 and part of which is submerged in the sea. It is composed of the above-mentioned structure and maintains the tidal current under the bottom surface of the structure 3 and is stable against rising when the tide level rises.

The structure 3 is basically a bottom plate 31 which is placed on the pillar 2.
And the side wall 32 that is exposed on the sea and goes around the outer periphery of the bottom slab 31, and the total weight W of the structure 3 is the buoyancy γ that acts on the subsea part.
V (γ: unit volume weight of seawater, V: volume of the portion where the structure 3 is submerged in the sea), and the difference between the total weight of the structure 3 and the buoyancy (W−γV) between the bottom plate 31 and the pillar 2. Number of columns 2 n
And a size (W−γ
Contact at a pressure of V) / nA (FIG. 3).

As shown in FIG. 4, the pillars 2 are constructed on abandoned concrete 6 which is cast on the sea floor, but if necessary, by means of an earth anchor 7 fixed to the rock below the sea floor to prevent falling or sliding. It is fixed on the sea floor. The pillar 2 is constructed, for example, by using a tubular precast concrete slab 8 that also serves as a formwork on the outer portion thereof, disposing the precast concrete slab 8 on the concrete 6 and then arranging and placing concrete. However, the construction method does not matter.

When the precast concrete slab 8 is used, the precast concrete slab 8 is used in the portion of the pillar 2, and a steel or other tubular temporary formwork 9 for removing seawater is placed on the precast concrete slab 8. Reinforcing steel bars 10 across the precast concrete slab 8 and the formwork 9
After precast concrete slab 8 and formwork 9 were replaced with bentonite in the state where 11 was set and the rebar 10 was stabilized, ground anchor 7 was driven into bedrock, precast concrete slab 8 and formwork 9 It is done by placing concrete 11 inside.

The bottom slab 31 of the structure 3 may be placed on the top of the column 2 while exerting pressures that do not move due to wave forces, but when the pressure is insufficient with respect to the wave forces, the columns 31 are placed. The bottom plate 31 and the pillar 2 are connected to each other by the reinforcing bar 10 arranged in the inside 2. Alternatively, by forming a protrusion on the column 2 and forming a groove into which the protrusion fits on the bottom plate 31, the columns 2 and the bottom plate 31 are engaged with each other in the horizontal direction so that force can be transmitted.

Inside the structure 3 on the bottom plate 31, a part or the whole of the structure 3 is constructed as will be described later, and after towing to the position of the pillar 2, seawater is taken in and settled on the pillar 2. A ballast tank 33 is formed for this purpose, and an opening 321 for taking in seawater inside the structure 3 is formed in the side wall 32 when the tide level rises. The level of the lower end of the opening 321 is located below the tide level which is assumed when the ocean structure 1 is completed and is most elevated.

FIG. 8 shows a case where seawater is taken into the inside of the structure 3 through the opening 321 formed in a part of the side wall 32 when the tide level rises, and the taken seawater is used as a ballast to resist buoyancy. Show the situation.

As the tide level rises, the buoyancy acting on the structure 3 increases, so the structure 3 tries to levitate from the pillar 2.
Due to the presence of the opening 321, seawater is automatically taken into the structure 3 from the opening 321 when the tide level exceeds the level of the lower end of the opening 321, and the taken seawater is buoyant as the tide rises. Therefore, the structure 3 is prevented from being lifted up because it becomes a ballast that cancels out the increased amount. In FIG. 8, seawater is taken into the upper layer of the ballast tank 33, but since the inside of the ballast tank 33 is hollow in the completed state of the marine structure 1, it can also be taken into the ballast tank 33.

The structure 3 is partly or entirely constructed in advance at a place other than the installation site, and then towed to the top of the pillar 2 to take seawater as ballast into the ballast tank 33 formed in the bottom slab 31. It is caused to sink. 7 is composed of the bottom plate 31 and a part of the side wall 32 shown in FIG.
The case where the lower structure 4 which is a part of the structure 3 is previously constructed, the lower structure 4 is sunk, and the lower structure 4 is placed on the pillar 2 and then the upper structure 5 is constructed thereon to complete the structure 3 is shown. . When constructing the upper structure 5 on the lower structure 4, the construction is performed while extracting an amount of seawater commensurate with its weight, and finally the seawater in the ballast tank 33 is removed.

The bottom slab 31 of the structure 3 is placed on the pillar 2 on the plane and the side wall 32, and when a plurality of lower structures 4 are connected to complete the structure 3, as shown in FIG. Connected on the pillar 2. A defect portion 34 is formed on the bottom plate 31 of the portion on the top of the pillar 2, and the bottom plate 31 is connected to each other by the defect portions 34, 34 and is supported by the pillar 2. At the same time, the lower structures 4 and 4 are similarly connected at the abutting portion. Missing part
34, 34 and the butted portion are connected or integrated with each other by removing seawater and cleaning and then arranging reinforcing bars and placing concrete 11.

The connecting structure of the abutting portions of the lower structures 4 and 4 is determined by whether or not the bending moment is transmitted between the bottom plates 31, 31. When transmitting, it is integrated, and when not transmitting, it is simply connected. . Further, when the distance between the columns 2 and 2 is large, the structures 3 and 3 are connected by an expansion joint, but the lower structures 4 and 4 are closed with a waterproof rubber or the like to prevent intrusion of seawater. When the bottom slab 31 is connected to the pillar 2, the reinforcing bar is inserted into the pillar 2 from the defective portion 34 and the concrete 11 is placed to fix the bottom slab 31 to the pillar 2.

After supporting or connecting the lower structure 4 to the pillar 2, the upper structure 5 is formed on the lower structure 4 as shown in FIG.
And the offshore structure 1 is completed.

[0022]

EFFECTS OF THE INVENTION A plurality of pillars constructed in the sea and a structure constructed on the pillars and part of which is submerged in the sea constitute an offshore structure, and the structure is kept floating from the seabed. Therefore, the tidal current under the structure will not be obstructed and the impact on the ecosystem can be suppressed.

Further, since the opening is formed in a part of the side wall of the structure and the level of the lower end of the opening is located below the tide level at the highest rise, the opening of the side wall when the tide level rises. Of buoyancy that can automatically take in seawater from inside the structure into the structure, and act on the taken in seawater on the structure.
Since it can be used as a ballast for canceling the increase due to the rise of the tide level, it does not require special anchoring means such as anchors, mooring wires, or piles, and avoids the situation where the structure on the pillar floats up with a simple means. it can.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an outline of an offshore structure.

FIG. 2 is a cross-sectional view showing an offshore structure.

FIG. 3 is a schematic diagram showing the relationship between the weight of a structure and buoyancy and pressure.

FIG. 4 is an elevational view showing the procedure for constructing a pillar.

FIG. 5 is a perspective view showing a lower structure.

FIG. 6 is a plan view showing a connecting portion of adjacent structures.

FIG. 7 is an elevation view showing the relationship between columns and structures.

FIG. 8 is a schematic diagram showing a situation when the tide level rises.

[Explanation of symbols]

1 ... Offshore structure, 2 ... Pillar, 3 ... Structure, 31 ... Bottom plate, 32 ... Side wall, 321 ... Opening part, 33 ... Ballast tank, 34 ... Missing part, 4 ... Lower part Structure, 5 ... Superstructure, 6 ... Waste concrete, 7 ... Anchor, 8 ...
Precast concrete slab, 9 ... form, 10 ... rebar, 11 ... concrete.

Claims (2)

(57) [Claims] 1. A marine structure comprising a plurality of pillars constructed in the sea and a structure constructed on the pillar and partly submerged in the sea, the structure being a bottom slab mounted on the pillar, and the sea. Exposed to
It consists of side walls that circumscribe the outer circumference of the slab, and the total weight of the structure is greater than the buoyancy acting on its subsea part. It is in contact with the pillar by a large amount of pressure, an opening is formed in a part of the side wall, and the level of the lower end of the opening is located below the tide level when it rises most. Offshore structure. 2. While constructing a plurality of pillars in the sea, after towing part or all of a pre-constructed structure to a predetermined pillar, seawater is taken into the interior of the structure to sink it. The method for installing an offshore structure for mounting the bottom plate on a pillar to complete the offshore structure according to claim 1.