JPH055971B2 - - Google Patents

Description

[Detailed description of the invention] 《Industrial application field》 The present invention relates to a caisson construction method.

[Conventional technology] The caisson construction method involves installing a cylindrical caisson made of reinforced concrete with a cutting edge at the bottom on the ground.
This construction method excavates and removes the earth and sand inside the caisson, allowing the caisson to sink until it reaches a designated supporting ground, which then becomes the foundation of the structure. For example, when constructing the foundation of a bridge using this caisson construction method, the lower part of the caisson is used as the foundation and the upper part is removed.
Previously, explosives or breakers were used to separate the upper caisson and remove it.

<<Problems to be Solved by the Invention>> However, as mentioned above, the use of gunpowder and breakers worsens the working environment and also poses problems in terms of work efficiency, such as difficulty in removing crushed concrete blocks.

The present invention has been devised to effectively solve the above problems, and its purpose is to provide a caisson construction method that allows the removal of the upper caisson to be carried out quickly while maintaining a good working environment.

<<Means for Solving the Problems>> In order to solve the above problems, the present invention sequentially constructs an upper caisson on a lower caisson having a cutting edge, and after sinking the lower caisson to the supporting ground, In a caisson construction method in which a caisson is used as the foundation of a structure and the upper caisson is then removed, the upper caisson is composed of a plurality of pre-formed segments, and the segments are used as fasteners when the lower caisson is sunk. After the lower caissons have been fastened to each other in a disassembly manner and the lower caissons have been used as the foundation of the structure, the fasteners are loosened and the segments are sequentially disassembled and removed from the top.

<<Operation>> In the caisson construction method constructed as described above,
Since the upper caisson is constructed of multiple disassembly segments, the segments can be quickly disassembled and transported by simply loosening the fasteners.
Since the segments are reusable, construction costs can be reduced, and since there is no need to use explosives, a good working environment can be maintained.

<<Example>> An example of the present invention will be described below based on the drawings.

Figure 1 shows caisson 1 used as the foundation of the bridge.
The figure shows the state in which it has been sunk from the river bed 2 to a predetermined depth. This caisson 1 is made of reinforced concrete and the second
As shown in the figure, it has a cylindrical shape. The caisson 1 is composed of a lower caisson 1a as its lower half and an upper caisson 1b as its upper half. Upper caisson 1b
consists of a number of segments 3, each segment 3
are removably fastened to each other by bolts 4 and nuts 5, as shown in FIG. This will be explained in more detail below.

A cylindrical temporary cofferdam 6 is driven into the riverbed 2 to a predetermined depth. The upper end of the temporary cofferdam 6 projects slightly upward from the water surface 7 to prevent water from flowing into the inside of the temporary cofferdam 6. A built-up island 8 is constructed inside the temporary cofferdam 6 by removing the water inside and throwing earth and sand into it, and the caisson 1 is sunk from this built-up island 8.

The lower caisson 1a of the caisson 1 has a cutting edge 9 at its lower end, and its length is set to the length of the foundation to be constructed. This blade opening 9 is for reducing sinking resistance.

The upper caisson 1b is constructed by arranging a large number of disassembleable ready-made reinforced concrete segments 3 in the circumferential direction and stacking them in the vertical direction. A recess 17 is formed in the inner wall 3a of the segment 3, as shown in FIG. An insertion hole 18 is formed in the upper and lower side walls 3b of the recess 17 in the vertical direction, and this insertion hole 18 is continuous with an insertion hole 18 of another vertically adjacent segment 3. and a bolt 4 inserted into two consecutive insertion holes 18,
The upper and lower segments 3 are fastened together by a nut screwed onto the tip of the bolt 4. Further, the above-mentioned insertion holes are similarly formed in the left and right side walls of the recess 17, and the left and right segments 3 are fastened to each other by similar bolts and nuts. The lowest segment 3 is the lower caisson 1.
It is fixed with a nut 20 to an anchor bolt 19 protruding from the upper end of a.

Attach sealing material to the upper, lower, left, and right joint surfaces of segment 3 as necessary for waterproofing. This sealing material should be attached to the center of the joint surface as much as possible. Further, the joint portion inside the joint surface may be further filled with caulking material.

The upper caisson 16, which is a temporary wall made up of segments 3, functions as a press-fit bearing wall during sinking, and as a water-stop wall after sinking.

Next, the construction procedure of the caisson construction method of the present invention will be explained one by one. First, as shown in FIG. 1, after constructing the built-up island 8 inside the temporary cofferdam 6, the lower caisson 1a is constructed according to the conventional caisson construction method as described above. The lower caisson 1a may be vertically divided into several lots at the installation position of the island 8 and formed by splicing concrete, or may be formed in advance into one piece. Then, while excavating the inside of the lower caisson 1a,
is gradually lowered, and as the lower caisson 1a progresses, the segments 3 are stacked on top of the lower caisson 1a. This process is repeated in order to sink the lower caisson 1a to the required depth as shown in FIG. This sinking work can be carried out efficiently because the segments 3 can be connected to each other by simply tightening the bolts 4.

Next, as shown in FIG. 4, a bottom plate 13 is formed at the inner bottom of the lower caisson 1a, and filling concrete 11 is filled on top of this bottom plate 13.
A top slab 12 is constructed on the upper end of the bridge as the foundation of the bridge, and a bridge pier 10 is constructed on the top slab 12.

After completing the construction of pier 10, the upper caisson 1b
Segment 3 of is disassembled in order from the top. Segment 3 can be easily disassembled by simply loosening bolt 4. The disassembled segment 3 will be lifted up with a crane and removed. At this time, since the size of the segment 3 is constant, the removal work is easy and efficient. In addition, compared to destruction and removal using conventional breakers, there is no noise, there is no need to construct large-scale, solid work scaffolding, and there are no reinforcing bars on concrete blocks, making removal work very easy. Furthermore, when disassembling the upper caisson 1b, the construction island 8 is excavated and earth is removed accordingly, and when the disassembly of the segment 3 is completed, earth is filled up to two sides of the river bed within the temporary cofferdam 6, as shown in Fig. 5. After this, the temporary cofferdam 6 will be removed and the construction will be completed.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and can be modified in various ways. For example, the cross-sectional shape of the caisson 1 may be oval, rectangular, etc. in addition to being circular. Further, as fasteners for fastening the segments 3 to each other, in addition to bolts and nuts, connecting plates, support beams, etc. may be used in combination.

<<Effects of the Invention>> As described above, in the present invention, the upper caisson to be finally removed is composed of a plurality of segments that can be disassembled, so that the construction, disassembly, and removal of the upper caisson are facilitated, and the construction period can be shortened. Additionally, since no explosives or breakers are used, a good working environment can be maintained.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, in which Fig. 1 is a longitudinal cross-sectional view of the right half of the caisson when the submergence is completed, Fig. 2 is a cross-sectional view taken along the - line in Fig. 1,
FIG. 3 is a detailed sectional view of the part shown in FIG. 1, FIG. 4 is a front view of the pier, and FIG. 5 is a front view of the pier after completion of construction. 1...Caisson, 1a...Lower caisson, 1b
... Upper caisson, 3 ... Segment, 4 ... Bolt, 5 ... Nut, 6 ... Temporary cofferdam, 8 ... Tsukishima, 10 ... Pier.

Claims (1)

[Claims] 1. The upper caisson is successively constructed on top of the lower caisson having the cutting edge portion, and after the lower caisson is sunk to the supporting ground, the lower caisson is used as the foundation of the structure, and then the upper caisson is removed. In the caisson construction method, the upper caisson is composed of a plurality of pre-formed segments, and when the lower caisson is sunk, the segments are removably fastened to each other by fasteners, and the lower caisson is connected to the structure. A caisson construction method characterized in that, after being set as a foundation, the fasteners are loosened and the segments are sequentially disassembled and removed from the top.