JPH0132335B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for constructing a multi-tiered caisson embankment constructed by stacking caissons on the seabed.

Conventionally, when constructing a caisson embankment, the upper and lower caissons were connected by first lowering and fixing the lower caisson 1 on the seabed ground 2, and then pouring water into the upper caisson 3 while attaching the suspension wires, as shown in Figure 1. Let it settle while loosening, stack it on the lower caisson 1, and connect the joint protrusion 4 provided on the upper surface of the lower caisson 1.
This was done by fitting the joint recess 5 provided on the lower surface of the upper caisson 3.

However, such a joining method has the following drawbacks.

(b) In order to install the lower caisson 1 on the seabed ground 2, it is necessary to remove the unevenness of the seabed ground 2.
Furthermore, the submarine ground 2 has the disadvantage that it requires support strength commensurate with the weight of the caisson.

(b) The work is mainly done on-site and has the drawback of being easily influenced by sea conditions such as waves and weather.

(c) In multi-tiered caisson embankments, it is common to use the embankment's own weight to resist sliding and overturning, and the cross section of the embankment body is determined by the size of the design load, so if the design load is excessive. Upper caisson 3
However, it requires a large cross-sectional area, which is uneconomical.

The object of the present invention is to be able to join the upper and lower caissons without being affected by the topography of the seabed, to select a location that is not affected by weather or sea conditions, and to reduce the cross-sectional area of the upper caissons. An object of the present invention is to provide a method for constructing a multi-tiered caisson embankment that can suppress expansion.

In order to achieve the above object, the present invention has a configuration in which an upper caisson is stacked on a lower caisson, and a joint protrusion protruding from the upper plate of the lower caisson and a connecting protrusion provided on the bottom plate of the upper caisson are provided. In the caisson joining method in which prestressed steel members are suspended in advance at multiple locations on the upper plate of the lower caisson, and at the lower end of each of the prestressed steel members in the lower caisson, In addition to the bearing block and bearing plate, grout receiving molds are supported in advance, the lower caisson is floated on water, and water is poured into the lower caisson with the floating means attached to the lower caisson. The lower caisson is submerged to a required water depth and held suspended in the water by the floating means, and the upper caisson is lowered onto the lower caisson while water is poured into the upper caisson. The lower caisson is drained by fitting the joint recesses to increase buoyancy and the upper caisson is stacked on the lower caisson, and then the upper caisson is drained to substantially empty the water in the upper caisson. The prestressed steel members, which were previously suspended and supported on the upper plate of the lower caisson, are pulled up into the upper caisson through the through holes previously drilled in the bottom plate of the upper caisson, and the tightening work is performed. A method of constructing a multi-tiered caisson embankment is characterized by the following.

Next, an embodiment of the method for constructing a multi-tiered caisson embankment according to the present invention will be described in detail with reference to the drawings. First, in the present invention, as shown in FIG. 2, a plurality of through holes 6 are provided in advance in the upper plate 1A of the lower caisson 1, and using these through holes 6, prestressing (hereinafter abbreviated as PC) is applied to the upper plate 1A in advance. The steel materials 7 are each suspended and supported. The PC steel material 7 of this example is
It has a structure in which a PC steel wire 7B is housed within a sheath pipe 7A. At the lower end of the PC steel material 7, the PC steel wire 7B
A bearing block 8 crimped to the lower end, a bearing plate 9 supported on the bearing block 8 fitted around the outer periphery of the PC steel wire 7B, and a supporting material such as a round steel under the bearing plate 9. A grout receiving frame 11 supported via a grout 10 is provided in advance. A temporary cover 12 is attached in advance to the upper end of the PC steel material 7, and by locking this temporary cover 12 to the upper plate 1A of the lower caisson 1, the PC steel material 7 is suspended and supported by the upper plate 1A. . The upper plate 1 is placed so as to surround the temporary lid 12 that is locked to the upper plate 1A.
A ring-shaped gasket 13 is attached in advance to the upper surface of A.

The lower caisson 1 is floated in water, and as shown in FIG.
With a plurality of sets attached, the lower caisson 1 is submerged to a required water depth while water 15 is injected into the lower caisson 1, suspended in the water by the buoyancy of each floating means 14, and maintained in that state. Floating body 14B
is moored with an anchor 17 via a mooring rope 16.

Next, the upper caisson 3 is suspended by the hanging wire 20 of the crane 19 of the crane ship 18, and while water 21 is injected into it, it is lowered onto the lower caisson 1, and the upper caisson 3 is placed on the joint projection 4 of the lower caisson 1. Then, the upper caisson 3 is stacked on the lower caisson 1 by fitting the joint recesses 5 of the lower caisson 1 to drain the water inside the lower caisson 1 and increasing the buoyancy.

In this state, as shown in FIG.
and the through hole 22 pre-drilled in the bottom plate 3A of the upper caisson 3 are aligned, and the gasket 13 of the upper plate 1A of the lower caisson 1 is brought into contact with the bottom plate 3A of the upper caisson 3 and passes through the through holes 6, 22. The infiltration of seawater is prevented. In this state, the upper caisson 3 is drained to make the water 21 in the upper caisson 3 almost empty, and a diver enters the upper caisson 3 to open the temporary cover 23 blocking the through hole 22. It is suspended from the upper plate 1A of the lower caisson 1.
Pass the PC steel material 7 through the through hole 22 into the upper caisson 3
Lift it inside. Tension is applied to the lifted PC steel wire 7B to make it temporarily tense, and as shown in FIG. 5, it is temporarily fixed with a fixing fitting 25 via a bearing plate 24. In this state, the bearing pressure plate 9 at the lower end of the PC steel material 7 is brought into contact with the upper version 1A of the lower caisson 1, and the upper end of the grout receiving mold frame 11 is also brought into contact with the upper version 1A of the lower caisson 1. After the primary fixation of all the PC steel materials 7 is completed, main tensioning is performed on each PC steel wire 7B to completely fix it, and the upper end of each PC steel wire 7B is cut at a predetermined position. Thereafter, grout 26 is inserted into the through hole 22 from a grout injection hole (not shown).
inject. This grout 26 has through holes 22, 6
Grout material receiving mold frame 1 filled inside and at the lower end
1 is also filled. The fixing fitting 25 at the upper end is covered with mortar 27.

After the joining work of the upper and lower caissons 1 and 3 is completed, these caissons 1 and 3 are towed to the site by a towboat, and the upper and lower caissons 1 and 3 are filled with sand and the like and are sunk in the installation location.

In particular, when the lower caisson 1 and the upper caisson 3 are joined together using the prestressed steel material 7 in this manner, the relaxation caused by the tension of the prestressed steel material 7 can be effectively utilized. That is, when tensioning the PC steel material 7, the tension force decreases due to loosening during fixing, creep of concrete, etc. Therefore, it is common to consider the prestress loss in advance, but the amount is twice the design prestress, and the PC steel material 7 is required to have more proof strength than necessary, which is uneconomical.
On the other hand, in the case of the present invention, when a horizontal force due to waves or the like acts on the upper caisson 3, a tensile force due to the horizontal force is applied to the PC steel material 7 in addition to the tensile force due to tension. Therefore, the PC steel material 7 must be able to withstand both types of tensile forces. As described above, the PC steel material 7 used in multi-tiered caissons such as two-tiered caissons has the disadvantage that it is necessary to take into account the increase in tensile force due to horizontal force in the set yield strength, and that the prestress loss due to relaxation is large. In order to reasonably satisfy this requirement in terms of design, it is sufficient to make the prestress loss amount and the required tensile strength due to horizontal force approximately equal. In this way, each other's weaknesses can be compensated for, relaxation can be effectively utilized in the design, and uneconomical effects of the PC steel material 7 can be prevented.

In the above embodiment, the caissons are stacked in two stages, but the present invention can be similarly applied to multi-stage stacking of two or more stages.

As explained above, in the caisson joining method according to the present invention, the lower caisson is joined while suspended in the water by a floating means without touching the bottom of the water. There are advantages that are not factors. Further, according to such a joining method, the work can be performed in a yard such as a bay or an inlet, and the joining work can be performed without being affected by weather or sea conditions. Therefore, the on-site work is greatly shortened, so when applied to a breakwater, it becomes possible to construct it considerably offshore. Furthermore, in the present invention, since the upper and lower caissons are joined by a prestressed steel material, the tensile strength of this prestressed steel material can be expected, making it possible to bear most of the resistance against overturning.
In addition, the tension of the prestressing steel is added to the weight of the upper caisson, and therefore the frictional resistance against sliding of the upper caisson is expected to increase, and the resistance moment against overturning is expected to increase. As a result, there is no need to increase the cross-sectional area of the upper caisson to resist sliding or overturning of the upper caisson, and there is an advantage that the upper caisson can be manufactured with an economical cross-sectional area. Furthermore, according to the present invention, by making the prestress loss amount of the prestressed steel material approximately equal to the required tensile strength due to the horizontal force acting on the upper caisson,
They can compensate for each other's weaknesses, make effective use of the relaxation of prestressed steel, and prevent the uneconomical effects of prestressed steel. Moreover, in the present invention,
Since the prestressing steel material is suspended and supported from the upper part of the lower caisson in advance, there is no need for workers to enter the lower caisson during joining work, ensuring work safety. In addition, in addition to the bearing block and bearing plate, a grout receiving form is supported in advance under the PC steel material, so tensioning and fixing work can be carried out quickly.

[Brief explanation of drawings]

Fig. 1 is a vertical sectional view showing the state of joining of the conventional upper and lower caissons, Fig. 2 is a sectional view of essential parts showing the state in which the prestressing steel material is suspended from the upper plate of the lower caisson used in the present invention, and Fig. 3 is the present invention. Explanatory diagrams, FIGS. 4 and 5, showing an example of the implementation state of the caisson joining method according to
The figure is a cross-sectional view of the main part required for the joining process of the upper and lower caissons according to the present invention. 1...Lower caisson, 1A...Upper plate, 3...Upper caisson, 4...Joint protrusion, 5...Join recess,
6...Through hole, 7...PC steel material, 7A...Sheath pipe, 7B...PC steel wire, 8...Bearing block, 9
... Bearing plate, 10 ... Support material, 11 ... Grout material receiving formwork, 12 ... Temporary lid, 13 ... Gasket, 14A ... Cylinder, 14B ... Floating body, 14 ...
...Floating means, 15...Water, 16...Mooring line, 17
... Anchor, 18 ... Crane ship, 19 ... Crane, 21 ... Water, 22 ... Through hole, 23 ...
Temporary lid, 24... bearing plate, 25... anchoring fitting, 26... grout, 27... mortar.

Claims (1)

[Claims] 1 Stack the upper caisson on top of the lower caisson,
In the caisson joining method of fitting and joining a joining protrusion protruding on the upper version of the lower caisson and a joining recess provided on the bottom version of the upper caisson, the upper version of the lower caisson is preliminarily provided with a plurality of joint protrusions. A prestressed steel material is suspended at a location, and a grout receiving form is supported in advance at the lower end of each prestressed steel material in the lower caisson in addition to a bearing block and a bearing plate, and the lower caisson is suspended. is floated on water, and with a floating means attached to the lower caisson, water is poured into the lower caisson, the lower caisson is submerged to a required water depth, and suspended in the water by the floating means, and the upper caisson is While pouring water into the caisson, the upper caisson is lowered onto the lower caisson, and the joint recess is fitted onto the joint protrusion to drain water from the lower caisson, increasing buoyancy and lowering the upper caisson to the lower caisson. Then, the upper caisson is drained so that the water in the upper caisson is almost empty, and each of the prestressed steel members, which had been previously suspended and supported on the upper plate of the lower caisson, is placed on the upper caisson. A method for constructing a multi-tiered caisson embankment, characterized in that the caisson is pulled up into the upper caisson through each through-hole previously drilled in the bottom plate of the caisson to carry out the tightening work.