JPS6143493B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a submerged canopy construction method used when constructing concrete structures underwater, such as bridge foundations and marine construction.

Known construction methods of this type include the open caisson construction method, the new-machine caisson construction method, and the steel pipe lost plate well construction method. Among these construction methods, the new caisson construction method and the open caisson construction method are often applied when the superstructure is subject to large-scale loads. In particular, when the cost of cofferdam construction is extremely high, such as in deep rivers, underwater areas, or areas where waves occur, the caisson can be towed and suspended for construction. Among these, the open caisson method can be applied when the ground conditions are good and is lower cost than the new caisson method, but it is unsuitable when there are obstacles during sinking, such as a layer of cobblestones. The conditions for constructing concrete structures underwater are severe. In this regard, with the new caisson construction method,
Although it is under high pressure, it has the advantage of being able to work dry, ensuring reliable construction, and making the process easy to set up. However, because it is underwater construction, temporary facilities such as building an island or temporary cofferdams are required.

The present invention was made based on the above circumstances, and after driving a cylindrical steel plate cell into underwater ground and attaching a top cover to make it airtight, while maintaining a dry state with the internal pressure above the water depth pressure, By constructing an underwater foundation, we aim to provide a submerged construction method that eliminates the need for large-scale temporary equipment and has the advantage of shortening the work process.

Hereinafter, an example in which the construction method of the present invention is used in conjunction with foundation pile driving will be specifically described with reference to the drawings. First, foundation piles 1 such as concrete piles are driven into the underwater ground to be constructed (see Figure 1). Next, the cylindrical steel plate cell 2 is towed and suspended,
The steel plate cell 2 is brought to the construction site, and the steel plate cell 2 is driven and embedded using a vibro hammer 4 installed on a frame 3 provided at the upper end of the steel plate cell 2 (see FIG. 2). In this case, in order to maintain balance during sinking, it is preferable to provide an interlocking device so that the vibrohammers communicate with each other. Next, a required amount of excavation is performed within the steel plate cell 2, a deep well 5 is installed, and leveled concrete A is constructed underwater (see FIG. 3). Next, the reinforcing bars or steel frame B of the footing, which has been constructed in advance on land, is installed on the concrete A using a crane ship (see Fig. 4). Then, a lid 6 and a lock are attached to the steel plate cell 2 (see FIG. 5). In this state, the inside of the steel plate cell 2 is cut off from the atmosphere, so after starting drainage in the deep well 5, the internal pressure of the cell 2 is increased using a compressor or the like to correspond to the deep water pressure, and the water inside the cell 2 is drained ( (See Figure 6). This makes the inside of the cell 2 dry. Next, footing concrete C is constructed (see Figure 7), and standing concrete D is constructed (see Figure 8). Next, water is poured into the cell 2 to bring the internal pressure to normal pressure, and the deep well drainage is stopped (see Figure 9). Finally, the steel plate cell 2 is separated from the upper part of the footing, and the steel plate cell 2
The lid 6 and the like will be lifted and removed by a crane ship. Similarly, Deep Well 5 will also be eliminated. Next, construct the upper part of the standing concrete (see Figure 10). In this case, in order to separate a portion of the steel plate cell 2, it is preferable to prepare the steel plate cell 2 in advance so that it can be easily separated.

In the above embodiment, the deep well 5 was installed in the soil layer inside the cell 2 to prevent buoyancy, but there is also a method of connecting the foundation pile 1 and the lower part of the steel plate cell 2. There is also a method of suppressing cell 2 with an earth anchor. Further, in this embodiment, the reinforcing bars or steel frame B of the footing were constructed in advance on land and lowered into the cell 2 by a crane ship, but it is of course possible to construct them on site.

As described in detail above, the present invention enables the underwater foundation to be constructed by driving a cylindrical steel plate cell into underwater ground, attaching a top cover to make it airtight, and then maintaining a dry state with internal pressure higher than water depth pressure. It is characterized by the construction of As a result, the following effects can be obtained.

(1) Footing concrete can be constructed dry, resulting in a high-quality structure.

(2) Tsukishima such as the Nimamachitsuku caisson construction method;
There is no need for large-scale temporary equipment such as temporary cofferdams.

(3) Even if the supporting layer is deep, construction is possible within the range where foundation piles can be constructed.

(4) By separating a part of the steel plate cell, it becomes integrated with the footing, increasing the lateral resistance to the ground.
It is also advantageous in terms of earthquake resistance.

[Brief explanation of the drawing]

1 to 10 are schematic side views sequentially illustrating an embodiment of the canopy construction method of the present invention. 2... Steel plate cell, 4... Vibrohammer, 5
...Deep well, 6...lid.

Claims (1)

[Claims] 1 A submersible method in which a cylindrical steel plate cell is cast into the underwater ground, a top cover is attached to make it airtight, and then the underwater foundation is constructed while maintaining a dry state with the internal pressure higher than the water depth pressure. Kan construction method.