JPH057493B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for sinking a steel floating body on the ground below the water surface to serve as a manufacturing base for prefabricated steel sheet pile cells.

(Prior Art) Conventionally, most prefabricated steel sheet pile cells, apart from small ones, have been manufactured using an offshore assembly yard method. This method uses steel pipe piles (diameter
700 to 800 mm) was poured into the seabed, and the steel sheet piles were delivered from the ship to a tower crane, and the steel sheet piles were assembled in a circular pattern along the guide frame to complete the cell. In that case, after the construction is completed, that is, after the required number of steel sheet pile cells have been completed, these foundations will have to be dismantled and another foundation will have to be constructed in a new construction area, which will not only increase the construction cost but also increase the construction period. It was becoming inevitable that the period would be extended.

Therefore, there is an idea to sink steel floating bodies, such as floating docks (see Japanese Patent Publication No. 58-43531) used in caisson construction, into the seabed and use them as a manufacturing base for prefabricated steel sheet pile cells. . However, in this case, if the steel floating body were simply sunk to the seabed, local loads would be applied to the floating body due to the undulations of the seabed ground, and when the heavy weight of the steel sheet pile cells was added to this, the floating body itself would be destroyed.
Not only would this cause a serious hindrance to the construction work, but there was also a risk that the floating structure would not be able to be reused.

(Objective of the Invention) The present invention is intended to solve the above-mentioned problems, and it is possible to maintain a steel floating body used as a manufacturing base for prefabricated steel sheet pile cells without damaging the bottom surface even if the ground beneath the water surface is uneven. The purpose is to provide a method for reliably submerging it on the ground below the water surface.

(Structure of the Invention) In order to achieve the above object, the method of the present invention provides a hollow box-shaped steel floating body having a support base for supporting a working machine for manufacturing prefabricated steel sheet pile cells on the upper surface. By attaching a skirt that surrounds the surrounding area and protruding downward from the bottom surface of the floating body, and injecting water into the inside of the steel floating body at a predetermined position, the floating body is prevented from submerging the upper part of the support base. The skirt is scuttled and landed on the ground below the water surface, and then passed through a shaft provided in the steel floating body into a space surrounded by the bottom surface of the steel floating body, the inner surface of the skirt, and the ground below the water surface. At the same time as the sand flows in, the water in the space is discharged from another shaft provided in the steel floating body, and the space is filled with sand, dispersing the reaction force from the ground below the water surface, and It is characterized by protecting the bottom surface of the floating body.

(Example) An example of the method of the present invention will be described below with reference to the drawings.

FIG. 1 shows a floating dog (hereinafter simply referred to as a dog) 1 as a steel floating body used in carrying out the method of the present invention. The dog 1 is a large steel floating body with a square plan and a hollow interior, with support stands 3 erected extending parallel to both sides of the work deck 2, and its length and width are 30 m. The height of the support stand 3 is such that when the dog 1 itself is sunk on the ground below the water surface, the crane 4 supported on the upper deck of the support stand 3 protrudes from the water surface by a predetermined length or more.

A steel skirt 5 that contacts and surrounds the outer wall of the dog 1 is disposed at the lower part of the dog 1 so as to be slidable along the outer wall surface of the dog 1 and to protrude by a predetermined length from the bottom surface of the dog 1. Further, a water supply channel 6 is provided in the lower part of the dog 1, and this water supply channel 6 is opened and closed by operating a valve (not shown).

On the working deck 2 of the dog 1, a plurality of vertical shafts 7 with lids are provided at intervals. Among these, the shaft 7 on one end side is used as a drainage channel, and the other shaft 7
is used as a sand guideway. However, the number and arrangement of these vertical shafts 7 are determined depending on the degree of inflow of sand through the vertical shafts depending on the hardness and softness of the ground at the site where the dog 1 is to be sunk.

Further, a manual sensor 8 is provided at an appropriate location on the working deck 2 of the dog 1, as will be described later, to detect whether or not the lower side of the sunken dog 1 is filled with sand. This sensor 8 has a plate part 8b at the tip of a screw with a handle 8a, and whether the sensor 8 itself rotates toward the bottom of the dog 1 from a state where the plate part 8b is brought into close contact with the bottom surface of the dog 1 or not. This is used to measure the porosity of the sand.

To sink the dog 1 described above, first, as shown in FIG. 1, the dog 1 is towed to the site where it is to be sunk. In this case, the guiding frame 9 is placed on the working deck 2 of the dog 1 in advance, taking into consideration the economic efficiency of the prefabricated steel sheet pile cell construction method.

Then, at the site, the dog 1 is scuttled while being kept horizontal by injecting water into the inside of the dog 1 through the water supply channel 6, and the water is scuttled to match the undulating shape of the ground E under the water at the site, as shown in Figure 2. A skirt 5 protrudes from the bottom surface of the dog 1 by a predetermined length so that the high part of the ground E does not hit the bottom surface of the dog 1 during sinking, and its tip is bitten into the ground E to land. If the dog 1 is tilted due to the surface shape of the ground E upon landing, water is further poured into the dog 1 through the water supply channel 6 to provide horizontality.

Thereafter, as shown in Fig. 3, the fluidized sand 10 is flowed into the lower side of the dog 1 from one of the plurality of shafts 7 in the working deck 2 portion, the lid of which is opened as a sand channel. As a result, the water in the space S surrounded by the bottom surface of the dog 1, the inner surface of the skirt 5, and the ground E is discharged from the vertical shaft 7 on the other side with the lid opened as a drainage path by the volume of the inflowing sand 10. By sequentially introducing the fluidized sand through the vertical shaft 7, water in the space S is replaced with sand.

The filling of the sand 10 into the space S is carried out by starting from a state in which the tip plate portions 8b of the plurality of sensors 8 are brought into close contact with the bottom surface of the dog 1, as shown in FIG.
The judgment is made based on whether or not the sand itself rotates and is introduced toward the 10th layer of sand. When the sensor 8 moves downward, that part is further filled with sand 10.

Through the above steps, the dog 1 is integrated with the ground E through the layer of sand 10. Moreover, the ground E has undulations.
The high part of the dog 1 does not touch the bottom of the dog 1, and the reaction force from the ground E is dispersed by the layer of sand 10 that supports the bottom of the dog 1.
There is no damage to the bottom at all.

After the dog 1 is sunk, the crane 4 and guide frame 9
A cylindrical cell is assembled around the guiding frame 9 using a large number of straight steel sheet piles, and this cell is transported to a predetermined site by a hoist and installed.

After repeating the above cell manufacturing work to manufacture a predetermined number of cells, air is forced into the layer of sand 10 under the dog 1 through the vertical shaft 7 of the dog 1, as shown in FIG. The water inside the dog 1 is forcibly discharged through the water supply channel 6 by a drainage pump, and the dog 1 is floated. As shown in FIG. 6, the dog 1 floating on the water surface can be reused as an original floating dog or as a prefabricated base.

(Effects of the Invention) As explained above, according to the method of the present invention, even if the ground below the water surface is undulating, the undulating ground is covered with a sand layer, and the steel floating body is scuttled by water injection through the sand layer. Since it is integrated with the ground beneath the water surface, there is no local load applied to the bottom of the steel floating body, and even if the floating body is used as a manufacturing base for prefabricated steel sheet pile cells, there is no risk of it breaking. This has the effect of allowing the production of products to be carried out safely.

[Brief explanation of the drawing]

Figures 1 to 4 are views showing one embodiment of the present invention, in which Figure 1 is an elevational view showing the floating dog before it is sunk, and Figure 2 is an elevational view showing the floating dog after it is scuttled. An elevation view showing the skirt landing on the ground below the water surface; Figure 3 is a partially cutaway elevation view showing the state in which sand is flowing into the lower side of the floating dog; A partially cut-away elevation view showing the condition in which the bottom side of the dog is filled with sand. Figure 5 is an elevation view showing the state of the submerged floating dog just before it is floated. Figure 6 is the floating dog that has surfaced. FIG. 1...Floating dog (steel floating body), 5...
Skirt, 6... Water supply channel, 7... Vertical shaft, 8... Sensor, 10... Sand, 11... Barge, E... Ground beneath the water surface,
S...The space below the floating dog formed when it is submerged.

Claims (1)

[Claims] 1. A hollow box-shaped steel floating body having a support base on the upper surface for supporting a working machine for producing prefabricated steel sheet pile cells is provided with a skirt surrounding the floating body and protruding downward from the bottom surface of the floating body. By injecting water into the inside of the steel floating body at a predetermined position, the floating body is scuttled so that the upper part of the support base is not submerged in water, and the skirt is landed on the ground below the water surface, and then Sand is introduced into the space surrounded by the bottom surface of the steel floating body, the inner surface of the skirt, and the ground below the water surface through a shaft provided in the steel floating body, and the water in the space is drained into the steel floating body. A method for sinking a steel floating body into the ground below the surface of the water, characterized by discharging sand from another vertical shaft provided in the space and filling the space with sand.