JPS6149029A - Underwater foundation fixer - Google Patents

Abstract

PURPOSE:To easily push anchors into the bottom ground under water by a method in which annular anchors are set on the bottom ground under water, and water in the anchors is sucked and discharged in such a way as to enable the anchors to be pushed into the bottom ground readily. CONSTITUTION:An annular anchor 1 is set on the water-permeable layer 23 of the bottom ground 2 under water, and water in the anchor 1 is sucked and discharged through a suction hose 21. Whereupon, the inside of the anchor 1 becomes of a negative pressure and the anchor 1 is pushed into the bottom ground 2 by water pressures acting on the upside of the anchor 1. A pile 3 is penetrated into the center of the anchor 1 and driven into the ground, and a grout 14 is injected between the pile 3 and the anchor 1 to fix the pile 3 and the anchor 1. A tension leg 11 extended out downwards from a floating structure is connected to the anchor 1 through connectors 18.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a fixing device for an underwater foundation that is subjected to a pulling force.

[Prior art]

BACKGROUND ART Conventionally, as underwater (undersea) foundations that are subjected to pull-out force, drag foundations and gravity foundations are known. The M type utilizes the frictional resistance of the ground and the ground, while the latter uses the weight of a huge concrete block or steel structure to resist the pulling force.

Pocket foundations are not affected much by ground conditions, but gravity foundations tend to sink unless the ground is solid, so they are not often used.

FIG. 11 shows the foundation of a fixed jacket structure used for oil production, etc., in which the main support pile 6 is inserted into the steel pipe pillar 5 of the jacket structure 4 and is driven into the underwater ground 2. Skirt piles 9 are inserted into the cylindrical pile fixing member 8 fixed around the lower part of the jacket structure and driven into the underwater ground 2, and the pillars 5 and the main support piles 6
The pile fixing member 8 and the skirt pile 9 are connected by a grout material injected between them.

In addition, Figure 12 shows the tension leg platform (TLP)' (r), which is the base of the floating marine structure, and Figure 13 shows an enlarged view of the foundation of the TLP, with multiple cylindrical structures surrounding it. The lower end of a tensile membrane 11 made of wire strands, pipes, etc. is connected to the central part of the basic body 10 provided with the anti-fixation member 8, and the upper end of the tensile membrane 11 is connected to the floating structure 12, and the upper end of the tensile membrane 11 is connected to the floating structure 12. The pile 3 inserted into the fixing member 8 and driven into the underwater ground 2 and the pile fixing member 8
A bonding grout material 14 made of mortar is injected and filled between the two.

However, in the TLP, a large buoyancy force of several tens of tons acts on the floating structure 12 due to wave force and tidal current force during a typhoon, and the buoyancy force is transmitted to the foundation via the tensile membrane 11 as a pulling force.

The lower part of the floating structure 12 at T L P sinks into the sea under the initial tension of the tensile membrane 11, and the floating structure 12 does not sink even if its buoyancy is reduced by waves. If the floating structure 12 sinks, the tensile membrane 11
is loosened, the wave passes through, and when tensile force acts on the tensile membrane 11 again, a large impact force (slack phenomenon) occurs. Therefore, a feature of TLP is that the lower part of the floating structure 12 is forcibly sunk in advance by the tensile membrane 11 in order to prevent the slack phenomenon from occurring.

For this reason, 3,000 yen per foundation at all times, and 7 yen per foundation during storms.
A pull-out force of approximately 1,000 mm is applied, and the period fluctuates due to waves, so the tensile membrane and other constituent members deteriorate due to fatigue.

The use of pile foundations is no exception; the ground around the piles deteriorates due to cyclic loads, which can cause the piles to fall out due to reduced bearing capacity. It is said that the ground's bearing capacity will recover during the period of Shizakugakure, but the loss of the piles will not recover. In order to prevent the piles from falling out, it is possible to use long piles with an extremely large diameter (2 to 3 m), but in this case, large-scale construction equipment is required and the construction cost becomes extremely high, making it uneconomical. Not on target.

[Purpose and structure of the invention]

The purpose of this invention is to provide an underwater foundation fixing device that can advantageously solve the above-mentioned problems. It is installed on the underwater ground 2, and a pile 6 is fixed to the anchor member 1, and in an emergency such as during a rough sea condition, the water in the anchor member 1 is drained, and the anchor member 1 is fixed by the water pressure acting on the upper surface of the anchor member. The underwater foundation fixing device is characterized by pushing a pile 6 into the underwater ground 2.

〔Example〕

Next, the present invention will be explained in detail using illustrated examples.

1 and 2 show an underwater foundation fixing device used when carrying out the present invention, in which a circular steel outer cylinder 1 is attached to the outer and inner edges of a circular annular steel upper end plate 15.
6 and the upper ends of the steel inner cylinder 17 are fixed in a water-tight manner to form a box-shaped anchor member 1 with an open bottom. placed at the corner of the polygon,
The side portion of each anchor member 1 is connected to a steel connecting member 18 to constitute a basic structure 19, and the floating structure 12 and the connecting member 18 are connected to a tensile membrane 1 made of wire strands or the like.
The suction port of the suction pump 2° mounted and fixed on the floating structure 12 and the discharge port provided on the upper part of the anchor member 1 are connected via an on-off valve (not shown) and a suction port. are connected via a hose 21.

It should be noted that the pump 2o is not operated all the time, but is operated only during installation, during a storm, or when pushing in a pile that has been removed to restore it.

When constructing an underwater foundation using the underwater foundation fixing device, first, as shown in FIG. After the anchor member 1 is installed, the water inside the anchor member 1 is sucked and discharged by the pump 20. In this way, as shown in FIG.
It's pushed to 6. If the levelness of the foundation structure 19 is out of order at this point, the levelness of the foundation structure 19 is corrected by changing the amount of suction from within each anchor member to adjust the amount of subsidence. Note that when the anchor member 1 is pushed into the water-permeable layer 26, water enters the anchor member at a considerable speed, so a large pumping capacity is required. When the lower end of the anchor member 1 reaches the impermeable layer 24,
Almost no water will enter into the anchor member 1, so if the pump 20e is operated in this state, the pressure inside the anchor member 1 will be reduced, and the anchor member 1 will be strengthened by the water pressure acting on its two sides. Pushed in.

After the anchor member 1 is pushed into the impermeable layer 24 as shown in FIG. 5, as shown in FIG. 2, as shown in FIG.
and the anchor member 1, fix the anchor member 1 and the pile 3 with the grout material 14, and then
As shown in the drawings and FIG. 8, the tension legs 11 made of wire strands let out from the floating structure 12 downward are connected to the connecting members 18 in the basic structure 19.

Figure 9 shows a state in which the underwater foundation is slightly raised from its initial position (dotted line) due to creep due to constant loads and deterioration of ground bearing capacity due to cyclic loads during the service life of the marine structure (approximately 60 years). 10 shows a state in which the underwater foundation has been restored to its initial position by applying a suction force within the anchor member 1.

One of the advantages of this invention is that the foundation is easy to install. A typical TLP submarine foundation structure has a 10m insole, but it is not easy to lay it horizontally on the submarine ground.

Next, the advantages of this invention will be shown with specific numerical values.

In a relatively shallow sea area with a depth of 600 m, the diameter of the pile was set to 1524 mm.
+=+n and the diameter of the anchor member 'e400 Qwn, it is possible to expect an anchor member pushing force of 3222) by suctioning and discharging the water within the anchor member. If the pile penetration length is 60 holes and the frictional force between the pile and the soil is 0.8 kg/crn, the frictional resistance of the pile is 229.
8) This is smaller than the pushing force of the anchor member, so the pile can be easily pushed in by the pushing force of the anchor member.

Furthermore, at a water depth of 600 m, if the diameter of the pile is set to 2032y=m and the diameter of the anchor member is set to 4000 mm, the pushing force of the anchor member will increase to 5594). can be pushed in very easily.

In the case of the above embodiment, the horizontality of the foundation structure can be easily corrected by changing the amount of suction from each anchor member. Furthermore, the present invention can be implemented not only for the foundations of floating marine structures but also for the foundations of fixed marine structures.

[Effects of the Invention] According to the present invention, a box-shaped anchor member 1 with an open lower part is installed on the underwater ground 2, and the anchor member 1
The pile 3 is fixed to the ground, the water in the anchor member 1 is drained, and the anchor member 1 and the pile 3 are pushed into the underwater ground 2 by the water pressure acting on the upper surface of the anchor member, so it can be done by extremely simple means. The box-shaped anchor member 1 and the pile 6 fixed thereto can be easily pushed into the underwater ground 2, and furthermore, after the anchor member 1 and the pile 6 are pushed into the underwater ground 2, the load is constantly applied. The anchor member is supported by the pile 6, and in response to dynamic pullout force in an emergency such as a typhoon, suction force is applied within the anchor member to apply pushing force due to water pressure. It is possible to strongly counter the dynamic pulling force in an emergency by adding a pulling resistance of Or, if an indirectly connected anchoring member such as a tension leg becomes loose, a suction force is applied within the anchor member, and water pressure acting on the top surface of the anchor member is used to loosen the pile and anchor member. Since it can be pushed back and recovered, it is possible to eliminate slack in the anchoring member, thereby providing a highly reliable foundation, and when the piles and anchor members are pulled up, they can be pushed back and recovered. Since it can be recovered, there is no need to use extremely long piles with large diameters, which provides benefits such as economical construction.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view showing an underwater foundation fixing device according to an embodiment of the present invention, and FIG. 2 is a partially vertical perspective view showing an enlarged part of the device. Figures 6 to 8 are vertical side views showing the underwater foundation construction sequence, Figure 9 is a vertical side view showing the underwater foundation lifted from its initial position, and Figure 10 is the restoration of the underwater foundation to its initial position. FIG. FIG. 11 is a perspective view showing the foundation of a conventional jacket structure, FIG. 12 is a perspective view showing a conventional TLPI, and FIG. 13 is a vertical sectional side view showing the foundation of the TLPK. In the figure, 1 is a box-shaped anchor member, 2 is underwater ground,
6 is a pile, 11 is a tensile membrane, 12 is a floating structure, 14 is a bonding grout material, 18 is a steel connection material, 19 is a foundation structure,
20 is a suction pump, 21 is a suction hose, 22 is a wire rope, 23 is a permeable layer, and 24 is an impermeable layer.

Claims (1)

[Claims] A box-shaped anchor member 1 with an open bottom is installed on the underwater ground 2, and a resistor 3 is fixed to the anchor member 1,
An underwater foundation fixing device characterized in that the water in the anchor member 1 is discharged during rough sea conditions, and the anchor member 1 and the pile 3 are pushed into the underwater ground 2 by the water pressure acting on the upper surface of the anchor member.