JPH0223627Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field of the invention] The invention is a movable and fixed underwater structure for extracting seabed mineral resources such as oil and natural gas, and more specifically, It concerns the lower structure.

[Prior Art] Mobile and fixed underwater structures for extracting seabed mineral resources such as oil and natural gas usually have three or four substructures called legs that are submerged to the bottom, and are equipped with drilling equipment and residences. Those equipped with an upper structure containing equipment, etc. are in practical use.

FIG. 1 is a perspective view showing a main part of a leg of a movable and fixed underwater structure. This leg 1 has three pillars 2, 2
a and 2b are connected in a truss shape, and a plate 3,
3a, 3b are fixed and the pillars 2, 2a, 2b and the plate 3,
A spout tank 4 is attached to the lower surfaces of 3a and 3b by adhesive or the like to form a closed type leg.

Three to four legs 1 configured in this way are sunk into the sea, each of the spat tanks 4 are brought to the bottom, and an upper structure is constructed near the sea surface (after the upper structure is attached to the leg, the lower structure is sunk). Sometimes). When each leg 1 is installed on the seabed in this manner, most of each spat tank 4 will be buried in the sand due to the weight of the leg 1 itself and the superstructure.

Generally, when a tidal current collides with an obstacle on the seabed, its velocity distribution is as shown in Figure 2.
The closer it is to the surface, the smaller it is, and the higher it is, the larger it is, so when it collides with the obstacle 1a, a downward flow is generated. Therefore, in a structure consisting of closed legs, leg 1
When the current collides with the plates 3, 3a, and 3b installed at the bottom of the leg, the downward flow generated by this becomes a vortex as shown in Figure 3, and a horseshoe-shaped wash is created around leg 1 as shown by diagonal lines. A large hole 5
A was formed and leg 1 became unstable, posing a safety problem.

[Purpose of the invention] The present invention was made to solve the above-mentioned conventional problems.It prevents scouring by installing anti-scouring works around the legs, and eliminates the safety concerns. The purpose is to eliminate the

[Summary of the invention] The scour prevention device for movable and fixed underwater structures according to the present invention has a cylindrical scour prevention mechanism arranged on the outside of the spat tank, and a cylindrical scour prevention mechanism arranged on the surrounding wall to correspond to the flow velocity distribution of the tidal current. This type has a small opening, and a larger opening as it approaches the seabed, and a sliding mechanism that allows the anti-scouring mechanism to circumscribe the legs and move up and down.

[Embodiment of the invention] FIG. 4 is a perspective view of an embodiment of the invention. In addition,
The same or equivalent parts as in Figure 1 are given the same reference numerals.
The explanation will be omitted. 6 has an inner diameter that is the same as or slightly larger than the longest part of the spat tank 4 (usually about 10 m),
It is a cylindrical anti-scouring structure with a large number of holes 7 provided in the peripheral wall, and is arranged to surround the leg 1. In addition,
The hole 7 is formed with a small diameter at the top and a larger diameter closer to the seabed, taking into account the flow velocity distribution in the boundary layer. This scour prevention work 6 is, for example, the fifth
As shown in the figure, it is mounted so that it can move up and down with wires etc. along the rails 8, 8a, 8b provided on each pillar 2, 2a, 2b, and until the leg 1 bottoms out, it is attached to the spat tank 4. It is pulled upwards, and is lowered when the spat tank 4 reaches the bottom.

According to the results of experiments, the present invention configured as described above has a large number of holes 7 in the peripheral wall of the scour prevention work 6, and the tidal current flows through these holes 7. There will be no resistance. In addition, the speed of the current is divided into two parts, one passing through the hole 7 and the other flowing around the scouring prevention work 6, and becomes slower. Furthermore, the horseshoe-shaped hole 5a, which is considered to be the main cause of scouring, also slows down. , the velocity distribution after the current collides with the plates 3, 3a, and 3b has a smaller slope as shown in Fig. 6 because the size of the hole 7 changes up and down.
Since downward flow is less likely to occur, the horseshoe-shaped scour area is also reduced.

For this reason, the outside of the scour prevention work 6 is slightly scoured 5.
However, there is no possibility that a large hole will be formed around the leg 1 as in the conventional case.

The above explanation shows the case where a large number of round holes are provided in the peripheral wall of the scour prevention work, but the shape of the holes may be selected as appropriate, such as square, diamond, or oval. The moving means are not limited to those shown in the drawings, and various mechanisms can be implemented.

[Effects of the invention] As is clear from the above explanation, the present invention has a cylindrical scour around the bottom of the closed leg, with a small hole in the upper part and a large hole near the seabed in accordance with the flow velocity distribution. Since the preventive work is provided to prevent the lower surface of the leg and its surroundings from being scoured, safety concerns can be eliminated and a solid upper structure can be provided.

Furthermore, since the scour prevention work is configured to be movable up and down, it is easy to install the legs and the scour prevention work, which has great practical effects.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing the main parts of a conventional leg;
3 and 3 are explanatory diagrams of the scour action, FIG. 4 is a perspective view showing the main parts of the embodiment of the present invention, and FIG.
The plan view of the figure and FIG. 6 are explanatory diagrams of the operation of the present invention. 1... Leg, 2, 2a, 2b... Pillar, 3, 3
a, 3b...Plate, 4...Sput tank, 6...
Scour prevention work, 7...hole.

Claims (1)

[Claims for Utility Model Registration] A plurality of legs are formed by connecting a plurality of columns in a truss shape, attaching a plate to the bottom thereof, and fixing a spat tank to the bottom surface of the plate and said column, and sinking the legs to the bottom of the sea, In a fixed underwater structure in which superstructures are provided on these legs, small openings are arranged on the outside of each spout tank and correspond to the flow velocity distribution of the tidal current, and a small opening is formed at the top, and a large opening is opened as it approaches the seabed. A scour prevention device for a movable and fixed underwater structure, comprising a cylindrical scour preventer having an opening, and a slide mechanism in which the scour preventer circumscribes a leg and can move up and down. .