JPH11310911A - Footing caisson and installation method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a footing caisson whose bending rigidity is heightened as a whole, having high sliding resistance force, also preventing corrosion of a steel plate, and being easily manufactured. SOLUTION: A vertical steel plate 12 is so formed that the middle part thereof is formed in the shape of a slope and that the lower part is formed in a fan-shape with a moderate curvature, and it is used for a footing section 20 as it is. The vertical steel plate 12 is connected to a bottom slab steel plate 13 to constitute a closed curve. A frame 14 is finished inside a space formed of the bottom slab steel plate 13 and vertical steel plate 12, and concrete is cast in the whole area of the circumferential surface in the space. Mortar injecting pipes 21 passing through the bottom from the upper surface are arranged at specific intervals. By the constitution, stress concentration to the root of the footing can be relaxed as compared with the conventional hybrid caisson, and since tensile stress occurring in the concrete can be relaxed, durability is promoted. Since no asphalt mat is laid on the bottom, it is easily manufactured. Since the whole circumferential surface is covered with concrete, corrosion of the steel plate can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a footing caisson used, for example, as a breakwater, and a method for installing the footing caisson.

[0002]

2. Description of the Related Art As a conventional heavy-weight caisson 1 used as a breakwater, it is advantageous to have a large weight, and as shown in FIG. 12, a reinforced concrete caisson 1a and an asphalt mattress 1b are entirely reinforced concrete. 1c
Was made into a box shape.

[0003] First of all, since the weight is large, FIG.
As shown in FIG. 3 (a), it is necessary to improve the ground of the seabed 2 so as not to sink. As shown in FIG. 13C, land subsidence occurs, so that the height of the mound 3 needs to be increased. When the installation location is shallow, the marine crane and floating dock are required for towing to the installation location and sinking at the installation location, and installation is difficult (see FIG. 13D). There is a problem to say. In addition, 4 in FIG. 13 indicates a ground improvement unit.

[0004] In addition, reinforced concrete is liable to crack and a long caisson 1 cannot be manufactured.
A short caisson 1 as shown in FIG. However, when the short caissons 1 are joined, differential settlement is likely to occur. The frequency of towing and installation to the installation location increases. Since the wave force acting on the caisson cannot be averaged, each caisson is easily destroyed by the wave force. There is a problem to say.

Recently, instead of reinforced concrete, as shown in FIG. 14, a steel plate is used inside the outer wall 5a and on the back side of the vertical partition 5b, the horizontal partition 5c, and the bottom plate 5d to reduce the thickness of the member. A caisson (hereinafter, referred to as a “hybrid caisson”) 5 having a hybrid structure that is reduced in size to achieve weight reduction and easy manufacturing has been considered. Since the hybrid caisson 5 can be manufactured with a small weight and a long caisson, the problem of the heavy caisson 1 described with reference to FIG. 13 can be solved. Note that 5e in FIG. 14 indicates footing.

That is, since the hybrid caisson 5 is small in weight, it is not necessary to improve the ground on the seabed 2 (see FIG. 15A). In addition, since the amount of land subsidence is small, the height of the mound 3 is increased. No need (Fig. 15
(C)). Furthermore, even when the water depth of the installation location is shallow, towing to the installation location and sinking at the installation location can be easily performed (see FIG. 15D).

Further, as shown in FIG. 15B, since a long caisson 5 can be manufactured, uneven settlement is unlikely to occur.
The frequency of towing and installation to the installation location is reduced.
Further, since the wave force acting on the caisson 5 can be averaged, the caisson 5 is hardly destroyed by the wave force.

[0008]

However, this hybrid caisson 5 still has the following problems. As shown in FIG. 14, since the wall surface and the bottom surface are flat, there is a problem that the bending rigidity with respect to the load is reduced.

The conventional hybrid caisson 5
As shown in FIG. 16, in the lower part, a vertical steel plate 5aa forming the inside of the outer wall 5a and a bottom plate steel plate 5f forming the back side of the bottom plate 5d are joined at a right angle, and reinforced concrete 5g is provided with a stud dowel 5h. The structure is mechanically connected via That is, the vertical outer wall 5a and the footing 5e of the bottom plate 5d are mounted at right angles.

At the corner between the outer wall 5a and the footing 5e, two types of reaction forces + P and -P are generated when a wave force or a drag wave acts as shown in FIGS. When the wave force acts on the hybrid caisson 5 as shown in FIG. 17A, the footing 5e on the rear side (opposite to the sea) has a bottom plate steel plate 5f as shown in FIG. 17C. A reaction force + P that generates a tensile force is generated. As shown in FIG. 18 (a), the footing 5e on the front side (sea side) of the hybrid caisson 5 exerts a tensile force on the concrete surface on the upper surface of the footing 5e by water pressure as shown in FIG. 18 (c). The generated reaction force -P is generated. 17 (b) and FIG.
When a negative pressure due to the drawing wave is generated on the wall surface of the hybrid caisson 5 as shown in (b), a reaction force opposite to that described above is generated in the footing 5e.

Since the steel plate has a large tensile strength and the concrete is strong against the compressive force, as shown in FIG. 17 (c), it is very suitable when the tensile force acts on the bottom plate steel plate 5f and the compressive force acts on the concrete. It can be said that the structure is
Conversely, as shown in FIG. 18 (c), when a tensile force acts on concrete, concrete has a disadvantageous structure because it is weak in tension.

Also, since a bending moment M is generated at the root of the footing 5e as shown in FIG. 16, a large stress is generated at the root by the bending moment M. Normally, design considerations are made to reduce the stress by installing reinforcing ribs, but it is unavoidable that the stress is concentrated at the root. In particular, when tensile stress is generated on the upper surface of the concrete at the root, as shown in FIG. 18C, cracks C, which are factors that deteriorate the durability of the concrete, are likely to occur.

The caisson has a certain weight so that it does not move from the installation place even if it receives a wave force. However, the hybrid caisson 5 has a light weight as described above, so that the caisson has a resistance against the wave force. Decrease. Therefore, in the hybrid caisson 5, the asphalt mat 5i is laid at the bottom in order to increase the levee length to average the wave force, or to increase the footing 5e to increase the sliding resistance with the mound 3 ( 14 and 11
(A)).

In order to lay the asphalt mat 5i, as shown in FIG.
19 (b), the molten asphalt 5ia is spread over it, and when the molten asphalt 5ia is hardened, a step of inverting again as shown in FIG. 19 (c) is required. become. After turning over again, as shown in FIG. 19 (c), reinforcement is applied to the bottom slab 5d, and concrete is poured in as shown in FIG. 19 (d), and then shown in FIG. 19 (e). Thus, the side wall and the partition block are mounted.

As described above, when manufacturing the hybrid caisson 5, it is necessary to invert the bottom plate 5d twice, but when the length of the bottom plate 5d reaches 100 m, this inversion operation becomes very difficult. . In addition, since asphalt has water permeability, the hybrid caisson 5 has a problem that the steel sheet cannot be prevented from being corroded by seawater.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described conventional problems.
It is an object of the present invention to provide a footing caisson which has a high sliding resistance, can prevent corrosion of a steel plate, and is easy to manufacture, and a method of installing the footing caisson.

[0017]

In order to achieve the above-mentioned object, a footing caisson of the present invention has an intermediate portion formed with a slope or a curved surface, and a lower portion formed in a divergent shape with a gentle curvature, and the footing portion is formed as it is. The vertical steel plate formed is connected to the bottom plate steel plate to form a closed curved surface, concrete is poured over the entire outer peripheral surface of the space formed by these two steel plates, and a mortar injection pipe that penetrates from the top surface to the bottom surface is arranged. And And by doing in this way, while reducing a wave force, the relaxation of the tensile force which acts on concrete, and corrosion of a steel plate, it can manufacture easily.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION
The vertical steel plate, the middle part is a slope or curved surface, the lower part is formed in a divergent shape with a gentle curvature, and after forming a footing part as it is, it is connected to the bottom plate steel plate to form a closed curved surface, and perpendicular to these bottom plate steel plates Inside the space formed by the steel plate, a frame or bulkhead steel plate is installed, and concrete is poured into the entire outer peripheral surface of the space, and a mortar injection pipe penetrating from the top surface to the bottom surface at a required interval. It is the one that exists and is arranged.

In the footing caisson of the present invention, since the middle portion of the vertical steel plate is inclined by a slope or a curved surface, when a wave force acts, the wave force can be reduced.

In the footing caisson of the present invention,
The lower part of the vertical steel plate is formed in a divergent shape with a gentle curvature, and it is connected to the bottom plate steel plate after forming the footing part as it is, so if a tensile force acts on the concrete, these vertical steel plate or bottom plate The steel plate reduces the tensile force, and the durability is improved.

In the footing caisson of the present invention,
Since concrete is cast on the entire outer peripheral surface, corrosion of the steel plate can be effectively prevented.

The footing caisson of the present invention is installed by towing to a predetermined installation position and sinking, and then injecting mortar between the bottom of the footing caisson and the mound through a mortar injection pipe. During this installation,
If the concrete around the mortar pouring pipe on the bottom of the footing caisson is not cast, the mortar can be well penetrated into the mound.

Further, when a stiffening material is provided in the footing portion of the footing caisson of the present invention described above,
The flexural rigidity of the entire caisson is greater.

[0024]

FIG. 1 is a perspective view of a footing caisson according to the present invention.
Description will be made based on the embodiment shown in FIG. FIG. 1 is a partially cutaway view of a first embodiment of a footing caisson of the present invention, FIG. 2 is a partially cutaway view of a second embodiment of a footing caisson of the present invention, and FIG. FIG. 4 is a detailed view showing the structure of the footing caisson of the footing caisson shown in FIG. 4, FIG. 4 is an explanatory view of the lower part of the footing caisson shown in FIG. 2, and FIG. 5 is an explanatory view of the force acting on the footing part of the footing caisson shown in FIG. a) the acting force on concrete when a + P reaction force is generated, (b) the acting force on concrete when a -P reaction force is generated, and (c) when the + P reaction force is generated. (D) is a diagram showing the acting force on the steel plate and concrete when a -P reaction force is generated, and FIG. 6 is a diagram showing an example of a reinforcing structure in the footing portion. a) Fig. 1 In the case of the footing caisson shown, (b) is a perspective view of the structure corresponding to claim 2 in the case of the footing caisson shown in FIG. 2, FIG. 8 is an explanatory view of the installation state of the caisson, and (a) is a conventional view. (B) to (d) are explanatory diagrams in the case of using the footing caisson of the present invention in the case where the structure according to claim 2 is employed, and FIGS. FIG. 10 is a perspective view of a footing caisson corresponding to claim 3 in which a stiffener is provided in the footing portion, and FIG. 10 is a view similar to FIG. 3 of a footing caisson corresponding to claim 3 in which a stiffener is provided in the footing portion. FIG. 11 is a view for explaining a feature of a footing caisson corresponding to claim 3 in which a stiffener is provided in the footing portion.

1 to 11, reference numeral 11 denotes a footing caisson of the present invention. In the first embodiment shown in FIG.
The middle part of the vertical steel plate 12 is an oblique flat surface, and the lower part is formed in a divergent shape with a gentle curvature.
After it is set to 0, it is connected to the bottom plate steel plate 13 to form a closed curved surface.

On the other hand, in the second embodiment shown in FIG. 2, the middle portion of the vertical steel plate 12 is formed into a curved surface, and the lower portion is formed into a divergent shape having a gentle curvature. To form a closed curved surface.
That is, in the first embodiment shown in FIG. 1, the wall surface receiving the wave force is a flat surface, while in the second embodiment shown in FIG. 2, the wall surface receiving the wave force is formed entirely as a cylindrical curved surface. .

When the first embodiment shown in FIG. 1 is compared with the second embodiment shown in FIG. 2, FIG. 2 has a higher rigidity as a whole and is advantageous for a long caisson structure. In addition, the curved surface can reduce the height of the wave crawling on the wall surface, so that the wave pressure can be reduced.

Further, the footing caisson 11 of the present invention shown in FIG. 1 and FIG.
The lower part of the vertical steel plate 12 is formed in a divergent shape with a gentle curvature so as to form a closed curved surface with the footing 2.
After reaching zero, it is turned around and connected to the bottom plate steel plate 13, and the root of the footing 20 forms a gentle curved surface as shown in FIG. 3 and has a larger section modulus than the conventional hybrid caisson. doing. Therefore, stress concentration on the root of the footing 20 is reduced, and durability is improved.

A frame 14 in the first embodiment shown in FIG. 1 and a frame 14 in the second embodiment shown in FIG. 14 instead of bulkhead steel plate 1
5 are furnished. In addition, concrete 17 is cast over the entire outer peripheral surface of the space formed by the bottom slab steel plate 13 and the vertical steel plate 12 after reinforcing bars 16 are arranged (see FIG. 3). Reference numeral 18 denotes a number of stud dowels arranged on the outer peripheral surface of the vertical steel plate 12 or the bottom slab steel plate 13, and reference numeral 19 denotes a reinforcing member arranged on the inner peripheral surface of the vertical steel plate 12 or the bottom slab steel plate 13.

Further, the footing caisson 11 of the present invention is not limited to the above-mentioned one, and the footing caisson 1 described above is used.
As shown in FIGS. 9 and 10, for example, a stiffener 24 is formed on the footing 20 portion of FIG. 1 by forming one side surface along the footing 20 portion and the other side surface as a straight line connecting the width direction end surfaces of the upper and lower surfaces of the footing caisson 11. May be provided.

When such a stiffener 24 is provided,
Since the bending rigidity of the entire footing caisson 11 becomes larger, as shown in FIG. 10A, the width B of the bottom slab is smaller than that of the footing caisson 11 without the stiffener 24 shown in FIG. Can be increased, and the width a in the depth direction of the footing caisson 11 can be reduced, so that it is possible to cope with a deep water caisson having a water depth of about 30 m.

In addition, when the stiffener 24 is provided, the frame 14 can be simplified and the number of bulkhead steel plates 15 can be reduced. This stiffener 24
Even if it is a plate shape as shown in FIG.
The cross section as shown in FIG. 9B may be trapezoidal.

In the above-described footing caisson 11 of the present invention, since the entire outer peripheral surface is covered with the concrete 17, the lower side of the bottom slab is inevitably covered with the concrete 17, so that the bottom plate steel plate 13 and the vertical plate 12 Corrosion can be prevented.

The concrete 17 to be poured over the entire outer peripheral surface of the space formed by the bottom plate steel plate 13 and the vertical steel plate 12 is not particularly limited. However, if high-fluidity concrete is adopted, the entire process can be poured in one day. So you can
The time required for manufacturing can be reduced.

A mortar injection pipe 21 penetrates from the top to the bottom of the footing caisson 11 of the present invention.
They are arranged at required intervals in the longitudinal direction.

The footing caisson 11 of the present invention has the above-described configuration, and when it receives a wave force, as described above, two kinds of reaction forces of + P and -P are generated. When such reaction forces + P and −P are generated, two types of resistance cross sections are generated in the footing caisson 11 of the present invention.

That is, with respect to the reaction force + P, the concrete 17 on the upper surface side of the footing 20 has a structure shown in FIG.
As shown in FIG.
A tensile force acts on the surface of the concrete 17 on the bottom surface side. On the contrary, as shown in FIG. 5B, a tensile force acts on the concrete 17 on the upper surface side of the footing 20 against the reaction force −P, while the concrete 17 on the bottom surface side of the footing 20. Then, a compressive force acts.

On the other hand, the vertical steel plate 12 located on the top surface side of the footing 20 and the bottom plate steel plate 1 located on the bottom surface side of the footing 20
In No. 3, a compressive force acts on the bottom slab steel plate 13 with respect to the reaction force + P as shown in FIG. 5C, thereby relaxing the stress caused by the tensile force acting on the concrete 17 surface. In addition, as shown in FIG. 5D, a compressive force acts on the vertical steel plate 12 with respect to the reaction force -P, so as to reduce the stress due to the tensile force acting on the concrete 17 surface.

That is, the footing caisson 11 of the present invention.
Then, the tensile force generated in the concrete 17 is relieved and the durability is improved by generating a resistance force that effectively utilizes the respective excellent material properties such as the compressive force of the concrete 17 and the tensile force of the steel plate. ing.

FIG. 6 shows an example of shear reinforcement at the footing 20 portion. In the case where the inside is constituted by the frame 14 as shown in FIG. 1, as shown in FIG. The reinforcing panel 14a is attached to the frame 14, and the shearing force generated in the footing 20 is transmitted to the frame 14 via the reinforcing panel 14a so that the frame 14 bears the shearing force.

In the case where the bulkhead steel plate 15 is internally provided as shown in FIG. 2, the shearing force generated in the footing 20 by the bulkhead steel plate 15 is reduced as shown in FIG. 6B. Take charge. By doing so, in the footing caisson 11 of the present invention,
It will have a very high shear strength.

Such a footing caisson 1 of the present invention
In order to install the mortar 23, the mortar 23 is towed to a predetermined installation position, and after sinking at the installation position, the mortar 23 is injected between the bottom of the footing caisson 11 and the mound 3 through the mortar injection pipe 21. And the footing caisson 11 are directly connected by a mortar 23.

At the time of pouring the mortar 23, as shown in FIG. 7, if the concrete 17 is not cast around the mortar pouring pipe 21 on the bottom surface of the footing caisson 11, the pouring is performed. Mortar 2
3 is the height of the mortar injection pipe 21 and the mortar 2
Due to the specific gravity of the mound 3, it is extruded with a sufficient pressure, so that the inside of the mound 3 can be satisfactorily permeated. The penetration of the mortar 23 is stopped when the penetration force and the resistance force are balanced, but the mortar 23 has a trumpet shape as shown in FIG.
The mortar 23 can be formed into an appropriate shape such as an inverted funnel shape as shown in FIG. 8C or a disk shape as shown in FIG.
Can be adjusted.

By doing so, in the footing caisson 11 of the present invention, a sufficient shearing force can be obtained even when a shearing force acts on the bottom surface of the footing caisson 11 by the wave force as shown in FIG. be able to.

[0045]

As described above, the footing caisson of the present invention can reduce the stress concentration at the root of the footing and reduce the tensile stress generated in the concrete, as compared with the conventional hybrid caisson. As a result, durability can be improved.

Further, when a stiffening material is provided in the footing portion of the footing caisson of the present invention, the bending rigidity of the entire caisson becomes larger, so that it can cope with a deep water caisson and simplify the frame. In addition, the number of bulkhead steel sheets can be reduced.

Further, since the footing caisson of the present invention does not have an asphalt mat on the bottom surface unlike the conventional hybrid caisson, it can be easily manufactured. Moreover, since the footing caisson of the present invention covers the entire outer peripheral surface with concrete, corrosion of the steel plate can be prevented.

Further, the method of installing a footing caisson according to the present invention is not limited to simply mounting on a mound as in the conventional installation of a hybrid caisson, but the footing caisson is directly connected to the mound with a mortar. High shear force can be obtained.

[Brief description of the drawings]

FIG. 1 is an overall view of a first embodiment of a footing caisson according to the present invention, partially cut away.

FIG. 2 is an overall view of a second embodiment of a footing caisson according to the present invention, partially cut away.

FIG. 3 is a detailed view showing a structure of a footing portion of the footing caisson shown in FIG. 2;

FIG. 4 is an explanatory diagram of a lower portion of the footing caisson shown in FIG. 2;

5A and 5B are explanatory diagrams of a force acting on a footing portion of the footing caisson shown in FIG. 2, wherein FIG. 5A is a force acting on concrete when a + P reaction force is generated, and FIG.
(C) is the force acting on the steel plate and the concrete when a + P reaction force is generated, and (d) is the steel force when the -P reaction force is generated. It is a figure which shows the acting force to concrete.

6A and 6B are diagrams illustrating an example of a reinforcing structure in a footing portion, and FIG. 6A illustrates a case of the footing caisson illustrated in FIG.
(B) shows the case of the footing caisson shown in FIG.

FIG. 7 is a perspective view of a structure corresponding to claim 2;

8A and 8B are explanatory diagrams of a caisson installation state, where FIG. 8A shows a case where a conventional hybrid caisson is used, and FIGS.
(D) is an explanatory view in the case where the footing caisson of the present invention is used in the case where the structure corresponding to claim 2 is adopted.

9 (a) and 9 (b) are perspective views of a footing caisson according to claim 3, wherein a stiffener is provided in the footing portion.

FIG. 10 is a view for explaining features of a footing caisson corresponding to claim 3, wherein a stiffener is provided in the footing portion;
(A) is a view as viewed from the front, (b) is a view as viewed from the plane of (a), (c) is a view as viewed from the front of a footing caisson without a stiffener in the footing portion, (d) is a view of (c) viewed from the plane.

FIG. 11 is a view similar to FIG. 3 of a footing caisson corresponding to claim 3, wherein a stiffener is provided in the footing portion.

FIG. 12 is an explanatory view of a conventional heavy caisson.

13 (a) to 13 (d) are diagrams for explaining the problems of the conventional heavy caisson.

FIG. 14 is an explanatory diagram of a conventional hybrid caisson.

FIGS. 15 (a) to (d) are diagrams for explaining the advantages of the hybrid caisson which solves the problems of the conventional heavy caisson.

FIG. 16 is a view for explaining a lower structure of a conventional hybrid caisson.

FIG. 17 is a view for explaining a force generated in the outer wall and the footing with respect to the reaction force + P when a wave force or a pulling wave acts on a conventional hybrid caisson. FIG. 17A shows a reaction force when a wave force acts. FIG. 4B is a diagram illustrating a position where + P is generated, FIG. 4B is a diagram illustrating a position where a reaction force + P is generated when an underflow is applied, and FIG. 4C is a diagram illustrating a force generated in footing.

18A and 18B are diagrams illustrating a force generated at a corner portion between an outer wall and a footing and the like with respect to a reaction force −P generated by water pressure when a wave force or a pulling wave acts on a conventional hybrid caisson, and FIG. Is a diagram illustrating a position where the reaction force -P is generated by the water pressure when the wave force is applied, and (b) is a diagram illustrating a position where the reaction force -P is generated by the water pressure when the wave is applied; (c) is a diagram for explaining the force generated at the footing and the force generated at the corner between the outer wall and the footing.

19 (a) to (e) are diagrams for explaining a method of manufacturing a conventional hybrid caisson in order.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Footing caisson 12 Vertical steel plate 13 Bottom plate steel plate 14 Frame 15 Bulkhead steel plate 17 Concrete 20 Footing 21 Pipe for mortar injection 23 Mortar 24 Stiffener

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Tanaka 1-7-89 Minami Kohoku, Suminoe-ku, Osaka-shi, Osaka Inside Hitachi Zosen Corporation (72) Inventor Masamichi Uchida 1-chome, Minami-Kohoku, Suminoe-ku, Osaka-shi, Osaka 7-89 Hitachi Zosen Corporation

Claims (4)

[Claims] 1. A vertical steel plate, the middle portion of which is a slope or a curved surface,
The lower part is formed in a divergent shape with a gentle curvature and forms a footing part as it is, then connected to the bottom plate steel plate to form a closed curved surface, inside the space formed by these bottom plate steel plate and vertical steel plate, there is a frame or A footing caisson that is equipped with a bulkhead steel plate, casts concrete over the entire outer peripheral surface of the space, and arranges mortar injection pipes that penetrate from the top to the bottom at the required intervals. . 2. A footing caisson according to claim 1, wherein concrete is not cast around the mortar pouring pipe on the bottom surface of the footing caisson. 3. A footing caisson according to claim 1, wherein a stiffening material is provided at the footing portion of the footing caisson. 4. A mortar is injected through a mortar injection pipe between the bottom of the footing caisson and the mound after the footing caisson according to any one of claims 1 to 3 is sunk at a predetermined installation position. How to install a footing caisson.