Temporary closing structure

Abstract

The buoyancy acting on the temporary cofferdam structure is supported by a simple structure below the upper end surface of the temporary cofferdam structure. [Solution] The temporary cofferdam structure 2 comprises a temporary cofferdam body 21 and a pair of temporary cofferdam brackets 22. The temporary cofferdam body 21 comprises a pair of arms 24 arranged side by side in the left-right direction. The front ends of the pair of arms 24 contact the dam body 91 of the dam 9. The rear ends of the pair of arms 24 are connected at a position spaced apart from the dam body 91 to the rear. The pair of temporary cofferdam brackets 22 protrude from the left-right direction from the sides of the pair of arms 24 of the temporary cofferdam body 21. In the temporary cofferdam structure 2, the buoyancy acting on the temporary cofferdam body 21 is supported by the pair of fixed brackets 96, which are fixed to the dam body 91 and protrude rearward from the dam body 91, by the pair of temporary cofferdam brackets 22 contacting the fixed brackets 96 from below.

Description

Technical Field

[0001] The present invention relates to a temporary cutting structure that surrounds the periphery of a working place in water to form a working space.

Background Art

[0002] Conventionally, when constructing a dam embankment or a bridge pier, etc., a temporary cutting structure has been used to surround the periphery of a working place in water to form a working space. For example, in the case of a dam rehabilitation project for adding a discharge facility to a dam embankment, a temporary cutting structure having a channel-shaped (i.e., U-shaped) planar shape is adhered to the upstream surface of the embankment (see Patent Document 1 and Patent Document 2). Then, by draining the space between the temporary cutting structure and the upstream surface of the embankment (hereinafter, also referred to as "the space inside the temporary cutting structure"), it becomes possible to perform operations such as cutting the embankment in an air environment.

[0003] When the space inside the temporary cutting structure is drained, a buoyancy force corresponding to the amount of drainage acts on the temporary cutting structure. As a structure for preventing the temporary cutting structure from floating due to the buoyancy force, a support framework type and a pedestal concrete type structure are known.

[0004] Also, in Patent Document 1, a structure is disclosed in which a bottom block for preventing floating (for example, a concrete pedestal filled with underwater concrete in a steel formwork) is provided at the lower end of the temporary cutting structure, and the bottom block is fixed to the upstream wall surface of the dam embankment. In Patent Document 2, above the upper end surface of the temporary cutting structure, a floating prevention anchor is fixed to the upstream wall surface of the dam embankment by an anchor bolt, and the buoyancy force acting on the temporary cutting structure is also supported by a washer portion sandwiched between the lower end of the floating prevention anchor and the upper end surface of the temporary cutting structure.

[0005] On the other hand, in Patent Document 3, a caisson made of multiple blocks stacked vertically is fixed to the upstream wall of the dam's embankment. Between the downstream surface of the caisson and the upstream wall of the dam's embankment, a wedge-shaped door stop structure is provided in a side view and fixed to the dam's embankment. The upper end of the door stop structure is provided with a pair of projections that protrude upstream (i.e., extend upstream), and the lower surface (bearing surface) of each projection abuts against the upper surface of the second block from the top of the caisson, thereby supporting the buoyancy acting on the caisson. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2005-139865 [Patent Document 2] Patent No. 5866309 [Patent Document 3] Patent No. 7500012 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] By the way, when bottom blocks for preventing uplift are installed in the temporary cofferdam structure, as described in Patent Document 1, the amount of work done underwater is extremely large, which may increase construction costs and construction time. Also, the uplift prevention anchors and feet described in Patent Document 2 can only be installed when the dam body protrudes above the upper end surface of the temporary cofferdam structure.

[0008] On the other hand, the buoyancy support provided by the door stopper structure described in Patent Document 3 can be implemented even when the dam body does not protrude above the upper end surface of the temporary cofferdam structure. However, this door stopper structure is a structure that integrates the door stopper hardware and the buoyancy support mechanism, making its structure more complex than that of ordinary door stopper hardware. Furthermore, it is necessary to cut out the downstream end of the uppermost block of the caisson, which also complicates the structure of the caisson. In addition, since the bearing surface of the door stopper structure must be in contact with the upper surface of the caisson, the installation position of the door stopper structure is limited.

[0009] This invention has been made in view of the above problems, and aims to support the buoyancy acting on the temporary cofferdam structure with a simple structure below the upper end surface of the temporary cofferdam structure. [Means for solving the problem]

[0010] One aspect of the present invention is a temporary cofferdam structure installed adjacent to a target structure extending upward from below the water surface, surrounding an underwater work area to form a work space, comprising: a temporary cofferdam body having a pair of arms arranged side by side in the left-right direction, with their front ends in contact with the target structure and their rear ends connected at a position spaced apart from the target structure to the rear; and a pair of temporary cofferdam brackets projecting in the left-right direction from the sides of the pair of arms of the temporary cofferdam body. The pair of temporary cofferdam brackets abut from below against a pair of fixed brackets fixed to the target structure and projecting rearward from the target structure, thereby supporting the buoyancy acting on the temporary cofferdam body.

[0011] Aspect 2 of the present invention is a temporary cofferdam structure according to aspect 1, wherein the temporary cofferdam body is a floating structure provided with a sealed space inside that serves as a buoyancy chamber.

[0012] A third aspect of the present invention is a temporary cofferdam structure according to aspect 1 or 2, wherein the target structure is the embankment of a dam. The pair of fixing brackets are fixed to the upstream face of the embankment.

[0013] Aspect 4 of the present invention is a temporary closure structure according to aspect 1 or 2 (or any one of aspects 1 to 3), wherein the temporary closure body is composed of a plurality of structural elements stacked in the vertical direction.

[0014] Aspect 5 of the present invention is a temporary closing structure according to aspect 4, wherein the pair of temporary closing brackets are provided below the uppermost structural element.

[0015] Aspect 6 of the present invention is a temporary cofferdam structure according to aspect 1 or 2 (or any one of aspects 1 to 5), wherein the pair of temporary cofferdam brackets are provided on the side of the pair of arms opposite to the working space. The temporary cofferdam structure further comprises another pair of temporary cofferdam brackets that project left and right from the side of the pair of arms on the working space side. The buoyancy acting on the temporary cofferdam body is also supported by the other pair of fixing brackets by contacting from below another pair of fixing brackets that are fixed to the target structure and project rearward from the target structure.

[0016] Embodiment 7 of the present invention is a temporary cofferdam structure according to Embodiment 1 or 2 (or any one of Embodiments 1 to 6), wherein the contact positions of the pair of temporary cofferdam brackets and the pair of fixed brackets are spaced apart from the target structure toward the rear.

[0017] Embodiment 8 of the present invention is a temporary closure structure according to Embodiment 1 or 2 (or any one of Embodiments 1 to 7), wherein the contact portion between the pair of temporary closure brackets and the pair of fixed brackets constitutes a horizontal plane.

[0018] Aspect 9 of the present invention is a temporary cofferdam structure according to aspect 1 or 2 (or any one of aspects 1 to 8), wherein the upper end surface of the temporary cofferdam body and the upper end surface of the target structure are located at the same position in the vertical direction. [Effects of the Invention]

[0019] According to the present invention, the buoyancy acting on the temporary cutoff structure can be supported with a simple structure below the upper end surface of the temporary cutoff structure.

Brief Description of the Drawings

[0020] [Figure 1] It is a side view of a temporary cutoff structure according to one embodiment. [Figure 2] It is a plan view of the temporary cutoff structure. [Figure 3] It is a side view showing an enlarged view of the vicinity of the temporary cutoff bracket. [Figure 4] It is a plan view showing an enlarged view of the vicinity of the temporary cutoff bracket.

Embodiments for Carrying Out the Invention

[0021] FIG. 1 is a side view showing a temporary cutoff structure 2 according to one embodiment of the present invention. FIG. 2 is a plan view showing the temporary cutoff structure 2. The temporary cutoff structure 2 is installed adjacent to a target structure extending from below the water surface 97 upward, and surrounds the working area under water to form a working space 90.

[0022] In the example shown in FIGS. 1 and 2, the target structure is the embankment 91 of the dam 9. The right side in FIG. 1 is the downstream side, and the left side is the upstream side (i.e., the reservoir side). In the following description, the downstream side and the upstream side of the dam 9 are also referred to as the "front side" and the "rear side", respectively. Also, the left-right direction in FIG. 2 is simply referred to as the "left-right direction". The left-right direction is a horizontal direction perpendicular to the front-rear direction. The temporary cutoff structure 2 is installed on the upstream wall surface (hereinafter also referred to as the "upstream surface 92") of the embankment 91, and is used, for example, in a dam rehabilitation project for adding discharge facilities to the embankment 91 of the dam 9. The upstream surface 92 is an installation target surface that extends along the left-right direction on the embankment 91. The upstream surface 92 may be substantially planar or curved.

[0023] The temporary cofferdam structure 2 comprises a temporary cofferdam body 21 and a plurality of temporary cofferdam brackets 22. The temporary cofferdam body 21 is a structure that forms a working space 90 on the upstream side of the embankment 91 by being fixed to the embankment 91 in contact with a door stopper 95 provided on the upstream face 92 of the embankment 91. The door stopper 95 is a substantially flat plate-shaped member that runs along the upstream face 92 of the embankment 91 and is fixed to the upstream face 92 of the embankment 91 by anchor bolts or the like. The shape of the door stopper 95 when viewed from the upstream side to the downstream side (i.e., the shape of the door stopper 95 when viewed from the rear) is, for example, a substantially rectangular frame shape. In the following, the door stopper 95 may also be considered as part of the embankment 91 in the explanation.

[0024] The temporary closure body 21 has a channel-shaped (i.e., roughly U-shaped) form in plan view. The temporary closure body 21 comprises a pair of arms 24, an arm connecting section 25, and a base 26. The pair of arms 24 are arranged side by side in the left-right direction in plan view. The arm connecting section 25 connects the rear ends (i.e., the upstream ends) of the pair of arms 24. The base 26 is connected to the arm connecting section 25 and the lower ends of the pair of arms 24, and covers the area below the work space 90. The temporary closure body 21 has a shape that is roughly symmetrical with respect to a virtual plane that passes through the center of the arm connecting section 25 in the left-right direction and is perpendicular to the left-right direction.

[0025] The pair of arms 24 are roughly rectangular parallelepiped-shaped portions that extend in the vertical and front-to-back directions (i.e., roughly perpendicular to the left-to-right direction). The pair of arms 24 are a pair of side wall portions that face each other while being spaced apart from each other in the left-to-right direction. In the example shown in Figure 2, the shape of each arm 24 in plan view is roughly rectangular, extending roughly parallel to the front-to-back direction. The front ends of the pair of arms 24 contact the upstream surface 92 of the dam body 91. Specifically, the front ends of the pair of arms 24 (i.e., the downstream ends) indirectly contact the upstream surface 92 of the dam body 91 via the door stop 95.

[0026] In the example shown in Figure 1, the upstream surface 92 is an inclined surface that slopes forward (i.e., downstream) as it extends upward. Therefore, the front end surfaces of the pair of arm sections 24 are also inclined surfaces that slope forward as they extend upward. Note that the upstream surface 92 is not limited to the inclined surface described above, and may be, for example, a vertical surface substantially parallel to the vertical direction. Also, in the example shown in Figure 1, the upper end surfaces 210 of the pair of arm sections 24 (i.e., the upper end surfaces 210 of the temporary cofferdam body 21) and the upper end surface 910 of the dam body 91 are located at approximately the same position in the vertical direction. Specifically, the vertical distance between the upper end surface 210 of the temporary cofferdam body 21 and the upper end surface 910 of the dam body 91 is, for example, 0.5 m or less, and preferably about 0 m.

[0027] The arm connection portion 25 is a roughly rectangular parallelepiped-shaped portion that extends in the vertical and horizontal directions (i.e., extends roughly perpendicular to the front-to-back direction). The arm connection portion 25 is a rear wall portion that extends along the left-to-right direction at a position spaced rearward from the upstream face 92 of the dam body 91. In the example shown in Figure 2, the shape of the arm connection portion 25 in plan view is a roughly rectangular shape that extends roughly parallel to the left-to-right direction. The arm connection portion 25 is connected to the rear ends (i.e., the upstream ends) of a pair of arm portions 24 at a position spaced rearward from the upstream face 92 of the dam body 91. In other words, the rear ends of a pair of arm portions 24 are indirectly connected to each other via the arm connection portion 25.

[0028] The rear end surface 251, which is the upstream surface of the arm connection portion 25, is the rear end surface of the temporary cofferdam body 21 and also the rear end surface of the temporary cofferdam structure 2. In the examples shown in Figures 1 and 2, the rear end surface 251 of the arm connection portion 25 is a substantially vertical surface substantially perpendicular to the front-rear direction. It is preferable that the rear end surface 251 of the arm connection portion 251 is a substantially vertical surface at least in the central part in the left-right direction. The shapes of the pair of arms 24 and the arm connection portion 25 can be changed in various ways. For example, the shape of the pair of arms 24 and the arm connection portion 25 in plan view may be such that the corner opposite to the working space 90 at the connection portion between each arm 24 and the arm connection portion 25 is cut off at an angle. Also, the rear end surface 251 of the arm connection portion 25 does not necessarily have to be a vertical surface; for example, it may be an inclined surface substantially parallel to the upstream surface 92 of the dam body 91.

[0029] The base portion 26 is a roughly rectangular or flat portion having an upper end surface that is roughly vertical in the vertical direction. The shape of the upper end surface of the base portion 26 in a plan view is roughly rectangular. The upper end surface of the base portion 26 extends in the left-right direction over the entire length between the pair of arm portions 24, and extends in the front-back direction over the entire length of each arm portion 24. The lower ends of the pair of arm portions 24 and the lower ends of the arm connection portions 25 are watertightly connected to the base portion 26.

[0030] The roughly rectangular space enclosed by the pair of arms 24, arm connecting portion 25, and bottom portion 26 of the temporary cofferdam body 21, and the upstream surface 92 of the dam body 91, is the aforementioned working space 90. The bottom surface of the working space 90 is the upper end surface of the bottom portion 26. In the following description, the side of the temporary cofferdam body 21 facing the working space 90 will also be called the "inside," and the side of the temporary cofferdam body 21 opposite the working space 90 will also be called the "outside."

[0031] In the temporary cofferdam body 21, the inner sides of the pair of arms 24 (i.e., the sides facing the work space 90) and the inner sides of the arm connection parts 25 are covered with watertight skin plates. The outer sides of the pair of arms 24 (i.e., the sides opposite the work space 90) and the outer sides of the arm connection parts 25 are also covered with watertight skin plates. A sealed space, which serves as a buoyancy chamber, is provided inside the temporary cofferdam body 21 (i.e., between the inner and outer skin plates). The temporary cofferdam body 21 is a floating structure capable of floating on the water surface 97. In other words, the temporary cofferdam structure 2 is a floating temporary cofferdam structure. In the temporary cofferdam structure 2, water can be injected into and drained from the buoyancy chamber. The buoyancy chamber also functions as a ballast tank for storing ballast water. The amount of buoyancy and the orientation of the temporary cofferdam structure 2 can be adjusted by injecting and draining water into the buoyancy chamber.

[0032] The length of the temporary cofferdam body 21 in the front-to-back direction is, for example, 3m to 10m. The width of the temporary cofferdam body 21 in the left-to-right direction is, for example, 5m to 20m. The height of the temporary cofferdam body 21 in the vertical direction is, for example, 5m to 50m. The weight of the temporary cofferdam body 21 is, for example, 5t to 500t. The width of each arm section 24 in the left-to-right direction, and the width of the arm connection section 25 in the front-to-back direction at its left-to-right center are, for example, 0.5m to 2m. The vertical height from the water surface 97 to the lower end of the temporary cofferdam structure 2 is, for example, 3m to 60m. The size and weight of the temporary cofferdam structure 2 can be changed in various ways.

[0033] The temporary cofferdam body 21 is composed of multiple structural elements (hereinafter also referred to as "blocks 23") that are stacked and connected in the vertical direction. Two adjacent blocks 23 in the vertical direction are connected by connecting members (not shown). A watertight packing (not shown) is sandwiched between each pair of adjacent blocks 23 in the vertical direction, and the two blocks 23 are connected in a watertight manner. The vertical height of each block 23 is, for example, 0.5m to 4m. The weight of each block 23 is, for example, 2t to 50t. The size and weight of the blocks 23 can be varied.

[0034] In the example shown in Figure 1, the temporary cofferdam body 21 is composed of six layers of blocks 23 stacked vertically. The water level 97 at the dam's normal full water level is located, for example, at the same vertical position as the vertical center of the uppermost layer of block 23. The boundary between each pair of adjacent blocks 23 in the vertical direction is approximately a horizontal plane (i.e., a plane approximately perpendicular to the vertical direction). The shape of the boundary and the number of layers of blocks 23 can be varied. For example, if the rear end surface 251 of the arm connection 25 is an inclined surface approximately parallel to the upstream surface 92 of the dam body 91, the boundary between each pair of adjacent blocks 23 in the vertical direction may be a plane approximately perpendicular to the upstream surface 92 of the dam body 91.

[0035] The shape of each block 23 in plan view is channel-shaped (i.e., roughly U-shaped). Each block 23 comprises a part that constitutes the pair of arm sections 24 described above, and a part that constitutes the arm connection section 25. In each block 23, for example, the front end of the part that constitutes the pair of arm sections 24 is connected to the upstream face 92 of the dam body 91 via a stopper 94 (also called a tightening fitting) (see Figure 4), which will be described later.

[0036] Each block 23, for example, is provided with multiple buoyancy chambers as described above. In each block 23, the multiple buoyancy chambers are arranged horizontally. In the temporary cofferdam structure 2, it is possible to individually fill and drain the multiple buoyancy chambers. Note that a block 23 may be provided with only one buoyancy chamber. Furthermore, the temporary cofferdam structure 2 may include blocks 23 that do not have buoyancy chambers.

[0037] In the temporary cofferdam structure 2 illustrated in Figures 1 and 2, four temporary cofferdam brackets 22 are provided. The four temporary cofferdam brackets 22 are located below the upper end surface 210 of the temporary cofferdam body 21 and below the upper end surface 910 of the dam body 91. The vertical positions of the four temporary cofferdam brackets 22 are approximately the same.

[0038] Two of the four temporary fastening brackets 22 protrude from the outer sides (hereinafter also referred to as "outer sides 241") of the pair of arms 24 of the temporary fastening body 21 in the left-right direction. The other two of the four temporary fastening brackets 22 protrude from the inner sides (hereinafter also referred to as "inner sides 242") of the pair of arms 24 of the temporary fastening body 21 in the left-right direction. In other words, the temporary fastening structure 2 comprises a pair of temporary fastening brackets 22 that protrude from the outer sides 241 of the pair of arms 24 in the left-right direction, and another pair of temporary fastening brackets 22 that protrude from the inner sides 242 of the pair of arms 24 in the left-right direction.

[0039] Specifically, in the right arm 24 of the pair of arms 24 shown in Figure 2, one temporary fastening bracket 22 protrudes from the outer surface 241 to the right in a direction approximately parallel to the left, and the other temporary fastening bracket 22 protrudes from the inner surface 242 to the left in a direction approximately parallel to the left. Also, in the left arm 24 of the pair of arms 24 shown in Figure 2, one temporary fastening bracket 22 protrudes from the outer surface 241 to the left in a direction approximately parallel to the left, and the other temporary fastening bracket 22 protrudes from the inner surface 242 to the right in a direction approximately parallel to the left.

[0040] In the example shown in Figure 2, a pair of temporary fastening brackets 22 protruding from the outer surfaces 241 of a pair of arm portions 24 in the left-right direction are positioned at approximately the same location in the front-rear direction. Additionally, another pair of temporary fastening brackets 22 protruding from the inner surfaces 242 of the pair of arm portions 24 are positioned at approximately the same location in the front-rear direction. In the example shown in Figure 2, all four temporary fastening brackets 22 are positioned at approximately the same location in the front-rear direction.

[0041] Each temporary fastening bracket 22 may be provided on any of the multiple blocks 23 that make up the temporary fastening body 21, but preferably it is provided below the uppermost block 23 of the multiple blocks 23. That is, it is preferable that the upper end of each temporary fastening bracket 22 is located below the upper end surface of the second block 23 from the top.

[0042] The four temporary closing brackets 22 are provided, for example, on the second block 23 from the top among the multiple blocks 23. Specifically, the upper end of each temporary closing bracket 22 is located at the same position as the upper end surface of the second block 23 from the top, or below that upper end surface. The lower end of each temporary closing bracket 22 is located at the same position as the lower end surface of the second block 23 from the top, or above that lower end surface. In the example shown in Figure 1, the lower end of the temporary closing bracket 22 is located at approximately the same position as the lower end surface of the second block 23 from the top, and the upper end of the temporary closing bracket 22 is located at approximately the same position as the vertical center of the second block 23 from the top. Note that the four temporary closing brackets 22 may also be provided below the second block 23 from the top.

[0043] Figure 3 is a magnified side view showing the vicinity of the temporary fastening bracket 22 provided on the arm portion 24 in Figure 1. Figure 4 is a magnified plan view showing the vicinity of the two temporary fastening brackets 22 provided on the right arm portion 24 in Figure 2. The structure shown in Figures 3 and 4 is substantially the same for the area near the left arm portion 24 in Figure 2.

[0044] Each temporary fastening bracket 22 has, for example, a flange that is substantially perpendicular in the vertical direction and a web that is substantially perpendicular in the front-rear direction, and is a member with an H-shaped or I-shaped longitudinal cross-section. The temporary fastening bracket 22 is fixed to the arm portion 24 of the temporary fastening body 21 by welding or the like. The shape of the temporary fastening bracket 22 can be changed in various ways. For example, the temporary fastening bracket 22 may be a flat plate-shaped member that is substantially perpendicular in the front-rear direction, or a substantially columnar member that extends substantially parallel in the left-right direction.

[0045] The four temporary cofferdam brackets 22 each abut from below against four fixed brackets 96 that protrude rearward (i.e., upstream) from the upstream face 92 of the dam body 91. The vertical positions of the four fixed brackets 96 are approximately the same. Each fixed bracket 96 comprises, for example, a protruding portion 961 and a base portion 962. The base portion 962 is a substantially flat plate-shaped member along the upstream face 92 of the dam body 91, or a substantially rectangular parallelepiped-shaped member extending vertically along the upstream face 92. The base portion 962 is fixed to the upstream face 92 of the dam body 91 by anchor bolts or the like. When viewed from the upstream side to the downstream side, the shape of the base portion 962 is, for example, substantially rectangular. The base portion 962 is a member that has thickness in the vertical and horizontal directions relative to the protruding portion 961, and is firmly connected to the upstream face 92 of the dam body 91. Furthermore, the shape of the base portion 962 can be changed in various ways, and is not limited to, for example, a member that has thickness in the vertical and horizontal directions relative to the protruding portion 961.

[0046] The projection 961 protrudes rearward from the upstream surface of the base portion 962. The projection 961 extends, for example, to the downstream surface of the base portion 962 and is fixed to the base portion 962 by welding or the like. The projection 961 is, for example, a member having a flange that is substantially perpendicular in the vertical direction and a web that is substantially perpendicular in the left-right direction, and has an H-shaped or I-shaped longitudinal cross-section. The shape of the projection 961 can be changed in various ways. For example, the projection 961 may be a flat plate-shaped member that is substantially perpendicular in the left-right direction, or a substantially columnar member that extends substantially parallel in the front-rear direction. Alternatively, two base portions 962 may be provided arranged vertically, and a truss-structure projection 961 may be provided that is connected to the two base portions 962. The lengths of the four projections 961 in the front-rear direction are substantially the same, and the lengths of the four fixing brackets 96 in the front-rear direction are also substantially the same. Note that the base portion 962 may be omitted in the fixing brackets 96.

[0047] In the example shown in Figure 4, the fixing bracket 96 located on the inside of the arm portion 24 (i.e., on the side facing the workspace 90) is spaced to the left (i.e., inward) from the inner surface 242 of the arm portion 24. The fixing bracket 96 located on the outside of the arm portion 24 (i.e., on the side opposite to the workspace 90) is spaced to the right (i.e., outward) from the outer surface 241 of the arm portion 24. In a plan view, each fixing bracket 96 does not overlap the temporary closure body 21 in the vertical direction.

[0048] In the examples shown in Figures 3 and 4, each temporary cofferdam bracket 22 abuts against the fixed bracket 96 at a position spaced rearward (i.e., upstream) from the upstream surface 92 of the dam body 91. In other words, the contact position between the temporary cofferdam bracket 22 and the fixed bracket 96 is spaced rearward from the upstream surface 92 of the dam body 91. At this contact position, the contact area between the upper surface 220 of the temporary cofferdam bracket 22 and the lower surface 960 of the protruding portion 961 of the fixed bracket 96 preferably forms a substantially horizontal plane that is substantially perpendicular in the vertical direction. In this embodiment, the upper surface 220 of the temporary cofferdam bracket 22 and the lower surface 960 of the protruding portion 961 of the fixed bracket 96 at this contact position are substantially horizontal planes, and the upper surface 220 of the temporary cofferdam bracket 22 and the lower surface 960 of the fixed bracket 96 are in surface contact.

[0049] In the example shown in Figure 3, the upper end of the protruding portion 961 of the fixed bracket 96, which is in contact with the temporary fastening bracket 22, is located below the upper end surface of the second block 23 from the top. Note that the temporary fastening bracket 22 and the fixed bracket 96 are not fixed to each other, for example, nor are they connected by a connecting member or the like.

[0050] In the example shown in Figure 4, a stopper 94 is provided between the outer surface 241 of the arm portion 24 and the fixing bracket 96 located on the outside of the temporary closing body 21, connecting the temporary closing body 21 and the door stopper 95. Therefore, the lateral distance between the fixing bracket 96 on the outside of the temporary closing structure 2 and the outer surface 241 of the arm portion 24 is greater than the lateral distance between the fixing bracket 96 on the inside of the temporary closing structure 2 and the inner surface 242 of the arm portion 24. Also, the lateral length of the temporary closing bracket 22 protruding from the outer surface 241 of the arm portion 24 is longer than the lateral length of the temporary closing bracket 22 protruding from the inner surface 242 of the arm portion 24.

[0051] In the temporary cofferdam structure 2, stoppers 94 are provided in each block 23 of the temporary cofferdam body 21. The temporary cofferdam structure 2 is fixed to the upstream face 92 of the dam body 91 via door stoppers 95 by a plurality of stoppers 94 arranged in the vertical direction. The stoppers 94 are, for example, a connecting structure including anchor bolts that extend substantially parallel in the front-rear direction. The shape and structure of the stoppers 94 can be changed in various ways. For example, the stoppers 94 may extend diagonally with respect to the front-rear direction and be fixed to the upstream face 92 of the dam body 91.

[0052] Next, an example of the installation process for the temporary cofferdam structure 2 on the dam body 91 will be described. When the temporary cofferdam structure 2 is installed on the upstream side of the dam body 91, first, the four fixing brackets 96 are fixed to the upstream face 92 of the dam body 91. In addition, the parts of the temporary cofferdam structure 2 excluding the uppermost block 23 (hereinafter also referred to as the "assembly") are assembled on the water surface 97 of the dam. Subsequently, the assembly is transported to the installation position while suspended on the water surface 97 by a crane barge or the like. The assembly abuts against the upstream face 92 of the dam body 91 via a door stopper 95 and is fixed to the dam body 91 by the stopper 94 described above. The four temporary cofferdam brackets 22 of the assembly are located below the four fixing brackets 96 of the dam body 91 and abut against the protruding parts 961 of the four fixing brackets 96 from below.

[0053] Next, the uppermost block 23 is stacked on top of the assembly and connected to it. The uppermost block 23 abuts against the upstream surface 92 of the dam body 91 via the door stopper 95 and is fixed to the dam body 91 by the stopper 94. After that, the water in the work space 90 is drained, and work can be carried out in an air-filled environment.

[0054] When the working space 90 is drained, a buoyant force equivalent to the amount of drained water acts on the temporary cofferdam structure 2. In the temporary cofferdam structure 2, a pair of temporary cofferdam brackets 22 that protrude left and right from the outer surfaces 241 of a pair of arm portions 24 contact a pair of fixed brackets 96 that are located at the same position in the left and right direction from below. As a result, the buoyant force acting on the temporary cofferdam body 21 is supported by the pair of fixed brackets 96.

[0055] Furthermore, another pair of temporary fastening brackets 22 that protrude laterally from the inner surfaces 242 of the pair of arm portions 24 abut from below against another pair of fixed brackets 96 located at the same position in the left-right direction. As a result, the buoyancy acting on the temporary fastening body 21 is also supported by the other pair of fixed brackets 96. Note that if the buoyancy acting on the temporary fastening body 21 is relatively small, one of the two temporary fastening brackets 22 provided on each arm portion 24 may be omitted.

[0056] As described above, the temporary cofferdam structure 2 is installed adjacent to the target structure (in the above example, the embankment body 91 of the dam 9) that extends from below to above the water surface 97, and surrounds the underwater work area to form a work space 90. The temporary cofferdam structure 2 comprises a temporary cofferdam body 21 and a pair of temporary cofferdam brackets 22. The temporary cofferdam body 21 comprises a pair of arms 24 arranged side by side in the left-right direction. The front ends of the pair of arms 24 are in contact with the target structure. The rear ends of the pair of arms 24 are connected at a position spaced apart from the target structure to the rear. The pair of temporary cofferdam brackets 22 project in the left-right direction from the sides of the pair of arms 24 of the temporary cofferdam body 21 (i.e., the outer surface 241 or the inner surface 242). In the temporary cofferdam structure 2, the buoyancy acting on the temporary cofferdam body 21 is supported by the pair of fixing brackets 96, which are fixed to the target structure and protrude rearward from the target structure, with the pair of temporary cofferdam brackets 22 contacting them from below.

[0057] This allows the buoyancy acting on the temporary cofferdam structure 2 to be supported by a simple structure below the upper end surface 210 of the temporary cofferdam structure 2. As a result, unlike structures that support buoyancy by an anti-uplift member extending upward from the upper end surface 210 of the temporary cofferdam body 21 (so-called support frame type), the buoyancy acting on the temporary cofferdam structure 2 can be supported even when the target structure does not substantially extend above the upper end surface 210 of the temporary cofferdam body 21. Therefore, the structure of the temporary cofferdam structure 2 is particularly suitable when the upper end surface 210 of the temporary cofferdam body 21 and the upper end surface of the target structure (in the above example, the upper end surface 910 of the embankment body 91) are located at the same position in the vertical direction.

[0058] Furthermore, in the temporary cofferdam structure 2, unlike the structure in which the upper end of the door stop extends above the temporary cofferdam structure 2 to support buoyancy, the structure of the door stop 95 can be simplified and lightened. Moreover, compared to the structure with a concrete base to prevent floating as described above (the so-called base type), the amount of work done underwater can be reduced, and construction costs and construction time can be reduced.

[0059] As described above, the temporary cofferdam body 21 is preferably a floating structure with a sealed space inside that serves as a buoyancy chamber. This eliminates the need for a structure to temporarily support the weight of the temporary cofferdam structure 2 when it is installed, unlike the support frame type and the pedestal type, thus simplifying the work involved in installing the temporary cofferdam structure 2.

[0060] As described above, the target structure is the embankment 91 of the dam 9, and it is preferable that the pair of fixing brackets 96 are fixed to the upstream face 92 of the embankment 91. As described above, the temporary cofferdam structure 2 can support buoyancy with a simple structure, and is therefore particularly suitable for construction work on the embankment 91 of the dam 9, where the water depth at the work site is relatively deep and the buoyancy support structure tends to be more complex compared to other construction work (i.e., construction work other than the dam embankment).

[0061] As described above, it is preferable that the temporary cofferdam body 21 is composed of multiple structural elements (i.e., blocks 23) stacked in the vertical direction. This makes it easier to transport the components constituting the temporary cofferdam body 21 to the work site, and also makes it easier to assemble the temporary cofferdam body 21 at the work site.

[0062] As described above, it is preferable that the pair of temporary cofferdam brackets 22 be provided below the uppermost block 23. This allows for a relatively large vertical distance between the pair of fixed brackets 96 that abut the pair of temporary cofferdam brackets 22 and the upper end of the target structure (in the above example, the embankment 91). As a result, the fixing strength of the pair of fixed brackets 96 to the target structure can be sufficiently large.

[0063] Furthermore, it is even more preferable that the pair of temporary cofferdam brackets 22 be provided on the second block 23 from the top among the multiple blocks 23. This allows the counterclockwise moment in Figure 1 due to horizontal water pressure to be greater than the clockwise moment in Figure 1 due to buoyancy, with the contact surface between the temporary cofferdam bracket 22 and the fixed bracket 96 as the center of rotation, thereby improving the stability of the support of the temporary cofferdam structure 2.

[0064] Furthermore, it is preferable that the upper ends of the protruding portions 961 of the pair of fixed brackets 96, which are in contact with the pair of temporary fastening brackets 22, are located below the upper end surface of the second block 23 from the top. This allows for an even greater vertical distance between the pair of fixed brackets 96 and the upper end of the target structure. As a result, the fixing strength of the pair of fixed brackets 96 to the target structure can be further increased.

[0065] As described above, it is preferable that the contact points between the pair of temporary cofferdam brackets 22 and the pair of fixed brackets 96 are spaced apart from the target structure towards the rear. This reduces the distance in the front-rear direction between the center of the buoyancy acting on the temporary cofferdam structure 2 and the contact points, compared to the case where the contact points are in close contact with the target structure. As a result, the stability of the support of the temporary cofferdam structure 2 by the pair of fixed brackets 96 can be improved.

[0066] As described above, it is preferable that the contact area between the pair of temporary cofferdam brackets 22 and the pair of fixed brackets 96 forms a horizontal plane. This improves the stability of the support of the temporary cofferdam structure 2 by the pair of fixed brackets 96 compared to when the contact area is inclined with respect to the horizontal plane.

[0067] In the example described above, the pair of temporary cofferdam brackets 22 are provided on the side of the pair of arms 24 opposite to the working space 90 (i.e., the outer surface 241). Preferably, the temporary cofferdam structure 2 further comprises another pair of temporary cofferdam brackets 22 that project laterally from the side of the pair of arms 24 facing the working space 90 (i.e., the inner surface 242). These other pair of temporary cofferdam brackets 22 abut from below against another pair of fixed brackets 96 that are fixed to the target structure and project rearward from the target structure. As a result, the buoyancy acting on the temporary cofferdam body 21 is also supported by these other pair of fixed brackets 96.

[0068] In this way, by supporting buoyancy on both the left and right sides of each arm 24, it is possible to suppress the acting of a twisting load on the arm 24 (i.e., a moment around an axis oriented in the front-rear direction). This suppresses the increase in weight of the arm 24 required to cope with such loads. Furthermore, compared to the case where only a pair of temporary fastening brackets 22 are provided, the load acting on each temporary fastening bracket 22 and each fixed bracket 96 can be reduced. Therefore, each temporary fastening bracket 22 and each fixed bracket 96 can be made smaller and lighter.

[0069] Various modifications are possible to the temporary closing structure 2 described above.

[0070] For example, the contact position between the temporary cofferdam bracket 22 and the fixed bracket 96 may be substantially in contact with the upstream surface 92 of the dam body 91.

[0071] The contact area between the temporary fastening bracket 22 and the fixed bracket 96 does not necessarily have to be surface contact. For example, a plurality of spherical bearings arranged in a matrix in a two-dimensional manner may be provided on the upper surface 220 of the temporary fastening bracket 22, and the lower surface 960 of the fixed bracket 96 may be in contact with these plurality of spherical bearings. Even in this case, the contact area between the temporary fastening bracket 22 and the fixed bracket 96 forms a horizontal plane, and therefore, compared to the case where the contact area is inclined with respect to the horizontal plane as described above, the stability of the support of the temporary fastening structure 2 by the pair of fixed brackets 96 can be improved. Note that the contact area between the temporary fastening bracket 22 and the fixed bracket 96 does not necessarily have to form a horizontal plane and can be modified in various ways, such as being inclined with respect to the horizontal plane. Furthermore, the spherical bearings described above may be arranged linearly on the upper surface 220 of the temporary fastening bracket 22, or only one spherical bearing may be provided.

[0072] The installation position of the stoppers 94 connecting each block 23 of the temporary cofferdam body 21 to the dam body 91 is not limited to the above example and can be changed in various ways. For example, in a plan view, the stopper 94 may be positioned between the inner surface 242 of the arm portion 24 and the fixed bracket 96 located inside the temporary cofferdam body 21. In this case, the lateral distance between the fixed bracket 96 inside the temporary cofferdam body 21 and the inner surface 242 of the arm portion 24 is greater than the lateral distance between the fixed bracket 96 outside the temporary cofferdam body 21 and the outer surface 241 of the arm portion 24. Also, the lateral length of the temporary cofferdam bracket 22 protruding from the inner surface 242 of the arm portion 24 is greater than the lateral length of the temporary cofferdam bracket 22 protruding from the outer surface 241 of the arm portion 24. Furthermore, the stopper 94 provided on the second block 23 from the top may be positioned above or below the fixed bracket 96 and the temporary cofferdam bracket 22.

[0073] The lateral distance between the outer fixing bracket 96 of the temporary fastening structure 2 and the outer surface 241 of the arm portion 24 may be smaller than, or approximately the same as, the lateral distance between the inner fixing bracket 96 of the temporary fastening structure 2 and the inner surface 242 of the arm portion 24. Also, the lateral length of the temporary fastening bracket 22 protruding from the outer surface 241 of the arm portion 24 may be shorter than, or approximately the same as, the lateral length of the temporary fastening bracket 22 protruding from the inner surface 242 of the arm portion 24.

[0074] The upper end of the protruding portion 961 of the fixed bracket 96, when in contact with the temporary fastening bracket 22, may be located above the upper end surface of the second block 23 from the top, or at approximately the same position vertically as the upper end surface. The upper end of the temporary fastening bracket 22 may also be located above the upper end surface of the second block 23 from the top, or at approximately the same position vertically as the upper end surface.

[0075] The temporary closing bracket 22 does not necessarily have to be installed on the second block 23 from the top; it may be installed on a block 23 below the second block 23 from the top. Alternatively, the temporary closing bracket 22 may be installed on the topmost block 23.

[0076] As described above, if the positions of the four temporary fastening brackets 22 in the front-rear and up-down directions are substantially the same, then in each arm portion 24, the temporary fastening brackets 22 protruding from the outer surface 241 and the temporary fastening brackets 22 protruding from the inner surface 242 may be continuous within the internal space of the arm portion 24. In other words, a single member may be provided that penetrates the arm portion 24 in the left-right direction and extends from the arm portion 24 to both sides, and the two temporary fastening brackets 22 protruding from the outer surface 911 and inner surface 242 of the arm portion 24 may be the ends of this single member.

[0077] The positions of the four temporary fastening brackets 22 in the front-to-back direction do not necessarily have to be the same; they may be different. Similarly, the lengths of the four fixed brackets 96 in the front-to-back direction do not necessarily have to be the same; they may be different. Furthermore, the positions of the four temporary fastening brackets 22 in the vertical direction do not necessarily have to be the same; they may be different. Similarly, the positions of the four fixed brackets 96 in the vertical direction do not necessarily have to be the same; they may be different. For example, a pair of temporary fastening brackets 22 protruding from the outer surface 241 of a pair of arm portions 24 may be located at the same position to each other in the vertical direction, while another pair of temporary fastening brackets 22 protruding from the inner surface 242 of a pair of arm portions 24 may be located at a different position in the vertical direction than the pair of temporary fastening brackets 22 mentioned above, but at the same position to each other in the vertical direction.

[0078] In the above description, the temporary cofferdam structure 2 is provided with two pairs of temporary cofferdam brackets 22, but it is not limited to this. For example, in the temporary cofferdam structure 2, three or more pairs of temporary cofferdam brackets 22 may be provided on a pair of arm portions 24, and the buoyancy acting on the temporary cofferdam body 21 may be supported by the three or more pairs of temporary cofferdam brackets 22 contacting three or more pairs of fixed brackets 96 from below. Alternatively, a pair of temporary cofferdam brackets 22 may be provided projecting in the left-right direction from the side of the pair of arm portions 24 facing the work space 90 (i.e., the inner surface 242). More preferably, the structure may further include another pair of temporary cofferdam brackets 22 projecting in the left-right direction from the side of the pair of arm portions 24 opposite to the work space 90 (i.e., the outer surface 241).

[0079] In the temporary fastening structure 2, only a pair of temporary fastening brackets 22 may be provided on the pair of arm portions 24. In this case, the temporary fastening brackets 22 may be provided on each outer surface 241 of the pair of arm portions 24, or on each inner surface 242 of the pair of arm portions 24. Alternatively, the temporary fastening brackets 22 may be provided on the outer surface 241 of one arm portion 24 and on the inner surface 242 of the other arm portion 24.

[0080] The temporary closure body 21 does not necessarily have to be composed of multiple blocks 23 stacked in the vertical direction; for example, it may be a single continuous member.

[0081] The temporary cofferdam body 21 does not necessarily have to be a floating structure with a buoyancy chamber inside. In other words, the temporary cofferdam structure 2 is not necessarily limited to a floating temporary cofferdam structure. For example, if the temporary cofferdam structure 2 has a structure in which the skin plate is omitted from the outer side surface of the temporary cofferdam body 21, the temporary cofferdam structure 2 will be placed on a steel base or the like provided on the upstream surface 92 of the dam body 91 and will be in contact with the upstream surface 92 of the dam body 91. Even in this case, the buoyancy generated when the working space 90 is drained will be supported by the fixed bracket 96 that contacts the temporary cofferdam bracket 22 from above, in substantially the same manner as described above. As a result, as described above, the buoyancy acting on the temporary cofferdam structure 2 can be supported with a simple structure below the upper end surface 210 of the temporary cofferdam structure 2. In this case, the fixed bracket 96 can also be attached to the dam body 91 after the temporary cofferdam structure 2 has been placed on the steel base or the like. As a result, the relative position between the fixed bracket 96 and the temporary tie-down bracket 22, etc., can be easily adjusted. Furthermore, the degree of freedom in selecting the construction method can be improved.

[0082] The upper end surface 910 of the dam body 91 of dam 9 does not necessarily have to be located at approximately the same vertical position as the upper end surface 210 of the temporary cofferdam structure 2; for example, it may be located above the upper end surface 210 of the temporary cofferdam structure 2.

[0083] The structure on which the temporary cofferdam structure 2 is installed is not necessarily limited to the dam body 91 of the dam 9, but may be any structure that extends from below the water surface upward (for example, a bridge pier that penetrates the water surface, or a strut of an offshore floating structure).

[0084] The configurations in the above embodiments and each modified example may be combined as appropriate, as long as they do not contradict each other. [Explanation of symbols]

[0085] 2. Temporary Closure Structure 9 dams 21 Provisional Deadline 22 Temporary closing bracket 23 blocks 24 Arm 90 workspace 91 Embankment body 92 Upstream side 96 Fixing bracket 97 Water surface 210 Upper end surface (of the temporary fastening body) 241 External surface 242 Inner surface 910 (Upper end face of the dam)

Claims

1. A temporary cofferdam structure is installed adjacent to a target structure that extends upward from below the water surface, and surrounds the underwater work area to form a work space. A temporary cofferdam body comprising a pair of arms arranged side by side in the left-right direction, the front ends of which contact the target structure and the rear ends of which are connected at a position spaced apart from the target structure to the rear, A pair of temporary fastening brackets protruding from the sides of the pair of arms of the temporary fastening body, Equipped with, A temporary cofferdam structure in which a pair of temporary cofferdam brackets abut from below against a pair of fixing brackets fixed to the target structure and protruding rearward from the target structure, thereby supporting the buoyancy acting on the temporary cofferdam body.

2. A temporary closing structure according to claim 1, The aforementioned temporary cofferdam body is a floating structure having a sealed space inside that serves as a buoyancy chamber, which is a temporary cofferdam structure.

3. A temporary closing structure according to claim 1 or 2, The aforementioned structure is the embankment of a dam. The pair of fixing brackets are a temporary cofferdam structure fixed to the upstream face of the dam body.

4. A temporary closing structure according to claim 1 or 2, The temporary closure body is a temporary closure structure composed of multiple structural elements stacked in the vertical direction.

5. A temporary closing structure according to claim 4, The pair of temporary cofferdam brackets are provided below the uppermost structural element, forming a temporary cofferdam structure.

6. A temporary closing structure according to claim 1 or 2, The pair of temporary fastening brackets are provided on the side of the pair of arms opposite to the working space, The temporary fastening structure further comprises another pair of temporary fastening brackets that protrude left and right from the sides of the pair of arms on the working space side, A temporary cofferdam structure in which the buoyancy acting on the temporary cofferdam body is also supported by the other pair of fixing brackets, which are fixed to the target structure and protrude rearward from the target structure, by contacting the other pair of temporary cofferdam brackets from below.

7. A temporary closing structure according to claim 1 or 2, A temporary cofferdam structure in which the contact positions of the pair of temporary cofferdam brackets and the pair of fixed brackets are spaced apart from the target structure toward the rear.

8. A temporary closing structure according to claim 1 or 2, The contact area between the pair of temporary cofferdam brackets and the pair of fixed brackets constitutes a horizontal plane, forming a temporary cofferdam structure.

9. A temporary closing structure according to claim 1 or 2, A temporary cofferdam structure in which the upper end surface of the temporary cofferdam body and the upper end surface of the target structure are located at the same position in the vertical direction.

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