Caisson construction method

Abstract

To provide a caisson construction method capable of improving adhesion between the cutting edge fitting of a caisson installed at a cutting edge portion and a concrete base.SOLUTION: The caisson construction method includes the following steps: setting, to a cutting edge portion S1, a steel caisson cutting edge fitting 10 that includes an annular outer peripheral frame portion 10a and an annular inner peripheral frame portion 10b that is connected therewith at the bottom, and opens at the top, and in which a groove V, which is concave when viewed from the internal space, is formed extending in the circumferential direction, and tapers outwards towards the bottom end; lowering caisson bodies S2, S3, and S4 constructed on top of the cutting edge portion S1, which has the cutting edge fitting 10 to a predetermined depth and installing the same; and after the sinking, pouring concrete base C into the bottom of the hollow interior to the thickness of covering the groove V formed in the inner peripheral frame portion 10b.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to the caisson method.

Background Art

[0002] When constructing underwater structures or underground structures such as bridge piers and breakwaters, caissons made of concrete or steel are used. A caisson is a cylindrical structure with a rectangular or circular horizontal cross-section of the body. The caisson method is a construction method in which the ground inside the hollow of the caisson body is excavated and sunk, and the caisson body is constructed on top of it repeatedly to construct a foundation structure.

[0003] A foundation structure using a caisson has features such as a large cross-section compared to other foundation structures, so it has high rigidity and small displacement, and both horizontal resistance and vertical bearing capacity can be expected to be large.

[0004] Now, the cutting edge formed at the deepest part of the caisson body that is vertically excavated into the ground and sunk into the ground is protected by a cutting edge metal fitting (caisson cutting edge metal fitting) made of steel plate because the load concentrates during sinking. This cutting edge metal fitting is composed of an annular outer peripheral frame part and an inner peripheral frame part. The inner peripheral frame part has a tapered shape that widens outward toward the lower end, and the contact surface of the inner peripheral frame part with the ground is manufactured so that the surface is smoothed and does not become a resistance during sinking.

[0005] Regarding caissons, for example, the technology described in Patent Document 1 (Japanese Patent No. 6423045) is known.

Prior Art Documents

Patent Documents

[0006] <000​​​​​​​​​​

[0007] Now, the inner circumferential frame of the caisson's cutting edge fittings has a smooth surface, making adhesion with the concrete poured after sinking uncertain. In the open caisson method (a method in which the caisson structure is gradually submerged while excavating the hollow interior), excavation is carried out under atmospheric pressure, and after reaching a predetermined depth, the base concrete is poured onto the bottom surface of the hollow interior. In this case, if the base concrete does not integrate with the caisson's cutting edge fittings, there is a risk that groundwater may flow into the caisson from between the base concrete and the cutting edge fittings.

[0008] Therefore, improving the adhesion between the cutting edge hardware and the base concrete is a challenge.

[0009] The present invention has been made in light of the above-mentioned technical background, and aims to provide a technology that can improve the adhesion between the caisson cutting edge fitting installed at the cutting edge and the base concrete. [Means for solving the problem]

[0010] To solve the above problems, the caisson construction method according to the invention described in claim 1 comprises an annular outer frame portion and a caisson that is connected to the outer frame portion at the lower end and has an opening at the top, A steel caisson cutting edge fitting is made, comprising an annular inner frame that is tapered and widens outward toward the lower end, wherein a groove-forming steel material is attached between the upper inner frame that constitutes the inner frame and the lower inner frame which is spaced apart from the upper inner frame, thereby forming a groove that is concave when viewed from the internal space, extends in the circumferential direction and is continuous around the entire circumference, and the manufactured caisson cutting edge fitting is made The caisson is characterized by being installed at the cutting edge, and while constructing the caisson structure on the upper part of the cutting edge where the caisson cutting edge fitting is installed, sinking it into the ground to a predetermined depth, and then pouring a base concrete to the bottom surface of the hollow interior after sinking, to a thickness that encloses the groove formed in the inner circumferential frame.

[0011] The caisson construction method according to claim 2 is characterized in that, in the invention described in claim 1, soil and sand adhering to the inner space side surface of the inner perimeter frame portion are removed prior to the pouring of the base concrete.

[0012] The caisson construction method according to claim 3 is characterized in that, in the invention described in claim 1, soil and sand adhering to the groove formed in the inner circumferential frame are removed prior to the pouring of the base concrete. [Effects of the Invention]

[0013] According to the present invention, when the poured base concrete is filled into the groove, the base concrete becomes caught in the groove, which improves the adhesion between the caisson cutting edge fitting installed at the cutting edge and the base concrete, thereby improving the watertightness of the interface. [Brief explanation of the drawing]

[0014] [Figure 1] This is an explanatory diagram illustrating the general procedure for constructing a caisson using a caisson cutting edge fitting according to one embodiment of the present invention. [Figure 2] This is a cross-sectional view showing a caisson cutting edge fitting according to one embodiment of the present invention. [Figure 3] This is a cross-sectional view showing the poured base concrete and the groove formed in the inner circumferential frame of the caisson cutting edge fitting. [Figure 4] This is a cross-sectional view showing a modified example of a caisson cutting edge fitting according to one embodiment of the present invention. [Figure 5] This is a cross-sectional view showing another modified example of the caisson cutting edge fitting according to one embodiment of the present invention. [Modes for carrying out the invention]

[0015] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings used to illustrate the embodiments, the same reference numerals are generally used for identical components, and repeated descriptions of such components will be omitted.

[0016] Figure 1 is an explanatory diagram illustrating the general procedure for constructing a caisson using the caisson cutting edge fitting according to this embodiment.

[0017] The caisson construction method of this embodiment is called the open caisson construction method. It is a method in which the caisson body is gradually sunk while excavating the hollow interior of the cylindrical caisson body constructed and installed on the ground by machine (or manually), and after reaching a predetermined depth, the caisson is used as a foundation structure.

[0018] Specifically, after constructing a sinking anchor (not shown) that serves as the sinking reaction force of the caisson body S, the ground G is leveled and the plate P is installed. Then, a cutting edge metalware (caisson cutting edge metalware) 10 composed of an annular outer peripheral frame portion 10a and an inner peripheral frame portion 10b that are connected to each other at the lower end and have an open upper part is installed at the sinking location, and concrete is poured to construct a cutting edge portion S1 that is the caisson body S located at the deepest part of the caisson (Fig. 1(a)). Details of the cutting edge metalware will be described later.

[0019] After constructing the cutting edge portion S1, a press-fitting facility is installed, and the sinking anchor and a press-fitting device (not shown) are connected. Then, after removing the plate P, the sinking anchor is pressed in using the reaction force while excavating the ground in the hollow interior with a clam shell (excavator) T. When the cutting edge portion S1 is sunk to a predetermined depth, an inner formwork and an outer formwork are installed above the cutting edge portion S1, reinforcing bars are arranged between the inner formwork and the outer formwork, and concrete is poured to construct the next lot of caisson body S2 (Fig. 1(b)).

[0020] The press-fitting of the caisson body S while excavating and the construction of the next lot of caisson body S on the upper part of the caisson body S are repeated. In the case shown in the figure, when three caisson bodies S2, S3, and S4 are constructed above the cutting edge portion S1 and the sinking is completed after reaching a predetermined depth, as shown in Fig. 1(c), bottom slab concrete C is poured on the bottom surface of the hollow interior. Then, as shown in Fig. 1(d), contact grout R is injected into the gap between the outer peripheral surface of the caisson body S and the ground, and the construction of the caisson as a foundation structure is completed.

[0021] Now, the steel cutting edge fitting 10 installed at the cutting edge portion S1 located at the deepest part of the cylindrical caisson body S sunk in the ground has, as shown in Fig. 2, an outer peripheral frame portion 10a that is annular in plan view and an inner peripheral frame portion 10b that is also annular in plan view. The outer peripheral frame portion 10a and the inner peripheral frame portion 10b are connected to each other at the lower end and are open at the upper end. The inner peripheral frame portion 10b is tapered so as to widen outward toward the lower end.

[0022] Also, in the space formed by the outer peripheral frame portion 10a and the inner peripheral frame portion 10b, anchor bars W are appropriately arranged to adhere to the placed concrete to increase the strength and integrate the cutting edge fitting 10 with the concrete.

[0023] In the inner peripheral frame portion 10b, a portion that is concave when viewed from the internal space surrounded by this inner peripheral frame portion 10b, that is, a groove portion V, is formed. In the present embodiment, the groove portion V is substantially horizontal and extends in the circumferential direction, and is continuously formed over the entire circumference of the inner peripheral frame portion 10b.

[0024] To explain the groove portion V formed in the inner peripheral frame portion 10b in detail, the inner peripheral frame portion 10b includes an upper inner frame 10b-1 located on the upper side and a lower inner frame 10b-2 provided at a distance from the upper inner frame 10b-1 below the upper inner frame 10b-1. Between the upper inner frame 10b-1 and the lower inner frame 10b-2, a groove steel material 10b-3 for forming the groove portion V is attached. In the case shown in Fig. 2, the groove steel material 10b-3 is a plate-shaped steel material 10b-3a attached so as to straddle the upper inner frame 10b-1 and the lower inner frame 10b-2.

[0025] In this embodiment, since the groove V described above is formed in the cutting edge fitting 10, the aforementioned base concrete C is poured to a thickness that encloses the groove V. When poured in this manner, as shown in Figure 3, the base concrete C is filled into the groove V, causing it to catch on the groove V, thereby improving the adhesion between the cutting edge fitting 10 and the base concrete C. As a result, the watertightness of the interface between the cutting edge fitting 10 and the base concrete C is improved, making it difficult for groundwater to flow into the caisson from between the base concrete C and the cutting edge fitting 10.

[0026] Furthermore, if soil and sand remain attached to the inner perimeter frame 10b when the base concrete C is poured, the adhesion between the cutting edge fitting 10 and the base concrete C will be poor. Therefore, prior to pouring the base concrete C, it is desirable to use an ultrasonic measuring device or the like to investigate the presence and location of soil and sand on the inner space side surface of the inner perimeter frame 10b (i.e., the side to which the base concrete C will be attached) (soil and sand confirmation step), and to remove the soil and sand using a soil and sand removal device or the like (soil and sand removal step).

[0027] Furthermore, as mentioned above, since the base concrete C becomes caught in the groove V, improving the adhesion between the cutting edge fitting 10 and the base concrete C, the soil confirmation process and the soil removal process may be performed only on the groove V, rather than on the wide area of ​​the inner space side of the inner circumferential frame portion 10b.

[0028] Although the invention made by the present inventors has been specifically described above based on embodiments, the embodiments disclosed herein are illustrative in all respects and are not limited to the disclosed art. That is, the technical scope of the present invention should not be interpreted restrictively based on the description in the embodiments above, but rather should be interpreted in accordance with the claims, and includes art equivalent to the art described in the claims and all modifications that do not depart from the gist of the claims.

[0029] For example, the steel material 10b-3 for the groove is not limited to the plate-shaped steel material 10b-3a, but various steel materials capable of forming the groove V can be applied. For example, as shown in Figure 4, an angle steel 10b-3b installed between the upper inner frame 10b-1 and the lower inner frame 10b-2, or as shown in Figure 5, a channel steel 10b-3c installed between the upper inner frame 10b-1 and the lower inner frame 10b-2 can be applied. When applying the angle steel 10b-3b or the channel steel 10b-3c, they should be installed between the upper inner frame 10b-1 and the lower inner frame 10b-2 in a direction that faces the internal space, as shown in the figure.

[0030] Furthermore, the groove V formed in the inner circumferential frame portion 10b does not have to be substantially horizontal, nor does it have to be formed continuously around the entire circumference of the inner circumferential frame portion 10b. However, if it is substantially horizontal and formed continuously around the entire circumference, the adhesion between the cutting edge fitting 10 and the base concrete C will be further improved, and the watertightness of the interface will be further enhanced.

[0031] In this embodiment, four caisson structures S2, S3, and S4 are constructed above the cutting edge S1, which is the deepest part of the caisson structure. However, the number of caisson structures S that are constructed is not limited to four. [Industrial applicability]

[0032] The caisson construction method according to the present invention can be applied when constructing underwater structures such as bridge piers, quays, and breakwaters, as well as various underground structures. [Explanation of symbols]

[0033] 10. Caisson caisson fittings 10a Outer frame section 10b Inner Circumferential Frame 10b-1 Upper inner frame 10b-2 Lower inner frame 10b-3 Steel material for grooves 10b-3a Plate-shaped steel material (steel material for grooves) 10b-3b Angle steel (steel material for grooves) 10b-3c Channel steel (steel material for grooves) C. Base concrete G Ground P dish plate R Contact Grout S Caisson structure S1 Cutting edge section (caisson body) S2, S3, S4 Caisson Structure V groove W anchor rebar

Claims

1. A steel caisson cutting edge fitting comprising an annular outer frame portion and an annular inner frame portion connected to the outer frame portion at its lower end, with an open top and tapered towards the bottom, wherein a groove-forming steel material is attached between the upper inner frame portion constituting the inner frame portion and the lower inner frame provided at a distance from the upper inner frame, thereby forming a groove portion that is concave when viewed from the internal space, extends in the circumferential direction, and is continuous around the entire circumference, the caisson cutting edge fitting is manufactured. The fabricated caisson cutting edge fitting is installed at the cutting edge, The caisson frame is constructed on the upper part of the caisson cutting edge where the aforementioned caisson cutting edge fittings are installed, and is then submerged into the ground to a predetermined depth. After settlement, concrete is poured into the bottom of the hollow interior to a thickness that encloses the groove formed in the inner circumferential frame. A caisson construction method characterized by the following features.

2. Prior to pouring the concrete base, remove any soil and sand adhering to the inner surface of the inner perimeter frame. The caisson construction method according to feature 1.

3. Prior to pouring the concrete base, remove the soil and sand adhering to the groove formed in the inner circumferential frame. The caisson construction method according to feature 1.

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