Joint structure between temporary cofferdam panels and temporary cofferdam construction method

Abstract

To provide a prestress joint structure between temporary cofferdam panels and a temporary cofferdam construction method, which can reduce the size of at least a bracing beam material by applying prestress in a circumferential direction, thereby making a cofferdam area smaller than a conventional cofferdam area.SOLUTION: In a joint structure 1 between temporary cofferdam panels for joining temporary cofferdam panels 2 that are installed around an existing underwater structure and are sealed off so that water does not enter an interior thereof to create a work space, a tendon 3 is inserted into a joint between the temporary cofferdam panels 2 in a horizontal direction, and prestress is introduced in the horizontal direction into the joint between the temporary cofferdam panels 2 by the tendon 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a joint structure between temporary cofferdam panels and a temporary cofferdam construction method using the same, and more particularly to a prestressed joint structure between temporary cofferdam panels that can resist external forces while reducing panel thickness by improving the joint structure between temporary cofferdam panels, and a temporary cofferdam construction method using the same. [Background technology]

[0002] In order to investigate, repair, or reinforce existing underwater structures (bridge piers and foundations) in rivers, etc., it is essential to install temporary cofferdam panels as temporary construction to seal off the surrounding area. For this reason, the applicant developed the STEP (registered trademark) method, a steel panel temporary cofferdam construction method in which divided cofferdam steel plates (steel panels) are assembled around the structure, sunk into the riverbed, and pressed into the required depth using a press-in jack. In combination with the press-in, soil and sand within the cofferdam steel plates are excavated, and after installing watertight treatment and shoring, the cofferdam steel plates are drained to ensure a dry work space.

[0003] Patent Document 1 discloses a temporary cofferdam construction method for an existing underwater structure, which was developed by the applicant, comprising: a reaction bracket installation step of installing a reaction bracket on top of the existing underwater structure to obtain a reaction force from the existing underwater structure when the temporary cofferdam is pressed into the underwater ground; and a temporary cofferdam pressing-in / excavation step of pressing the temporary cofferdam into the underwater ground with a press-in jack while obtaining a reaction force from the existing underwater structure with the reaction bracket, and excavating the underwater ground inside the temporary cofferdam, in which the temporary cofferdam is lowered while being guided by a guide bracket having a roller member or a sliding member at its tip that comes into contact with the temporary cofferdam (see claim 1 in the scope of claims of Patent Document 1, paragraphs

[0021] to

[0055] of the specification, and Figures 1, 4 to 21 of the drawings, etc.).

[0004] However, the temporary cofferdam structure used in the cofferdam method for existing underwater structures in Patent Document 1 was made of thick, heavy steel plates to provide a certain level of strength to withstand external forces such as the stress during pressurization and water and earth pressure. Furthermore, the panels of the temporary cofferdam structure were firmly bolted together to withstand the earth and water pressure acting on the joints, and bracing beams were installed as support. This meant that the cofferdam structure's cofferdam area was larger due to the bracing beams installed, which in turn increased the force required to withstand the river's water flow. This created the problem of having to increase the thickness of the temporary cofferdam structure and strengthen the bolt connections.

[0005] Furthermore, Patent Document 2 discloses a temporary cofferdam structure that is erected on the foundation of an underwater structure, has anchors that are installed so as to penetrate vertically between a plurality of annular assemblies, introduce tension and are fixed to the uppermost annular assembly, and the annular assemblies are made by dividing an annular body of a predetermined height into a plurality of precast panel units that are connected together with vertical sealing materials between the circumferential ends (see claim 1 in the scope of claims of Patent Document 2, paragraphs

[0017] to

[0036] in the specification, and Figures 1, 3, 5, etc. in the drawings).

[0006] However, the temporary cofferdam structure described in Patent Document 2 is prestressed in the vertical direction, so it can withstand horizontal shear forces to a certain extent, but it is not prestressed in the circumferential direction, so the only way to withstand shear forces acting between the temporary cofferdam panels is with bolt connections, and bracing beams are required as support to withstand the water flow.As a result, the cofferdam area increases due to the installation of the bracing beams, and the force resisting the river water flow also increases, so it was not possible to solve the problem of having to increase the thickness of the temporary cofferdam structure and strengthen the bolt connections. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6010070 [Patent Document 2] Patent No. 4374939 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention was devised in view of the above-mentioned problems, and its purpose is to provide a prestressed joint structure between temporary cofferdam panels that can reduce the size of at least the bracing beams by applying prestress in the lateral direction, thereby making the cofferdam area smaller than that of conventional cofferdam panels. [Means for solving the problem]

[0009] The prestressed joint structure between temporary closure panels of the first invention is a joint structure between temporary closure panels that joins panels of temporary closure panels that are installed around existing underwater structures to seal off the interior to prevent water from entering and create a work space, and is characterized in that tension members are inserted into the horizontal joints between the temporary closure panels, and prestress is introduced horizontally into the joints between the temporary closure panels by the tension members.

[0010] The prestressed joint structure between temporary closure panels according to the second invention is characterized in that, in the first invention, the vertical joints between adjacent temporary closure panels in the horizontal direction are not bolted.

[0011] The temporary cofferdam construction method according to the third invention is a temporary cofferdam construction method in which a temporary cofferdam body joined by the joining structure of temporary cofferdam panels as described in claim 1 or 2 is installed around an existing underwater structure to create a dry work space, characterized in that multiple temporary cofferdam panels are tensioned and prestressed with tendons to integrate them, and the temporary cofferdam body is assembled and constructed.

[0012] The temporary cofferdam construction method according to the fourth invention is the third invention, characterized in that no bracing beam members are installed inside the temporary cofferdam body. [Effects of the Invention]

[0013] According to the inventions of claims 1 to 4, compressive force acts on the vertical joint surfaces between the temporary cofferdam panels, helping to resist external forces, making bracing beams unnecessary, or at least reducing the size of the bracing beams and making the cofferdam area smaller than conventional cofferdam areas. This reduces river obstruction and enables the use of thinner steel plates for the temporary cofferdam panels, reducing the size and number of stiffeners, thereby reducing the manufacturing costs of the temporary cofferdam panels. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a horizontal cross-sectional view showing a joining structure between temporary cofferdam panels according to this embodiment. [Figure 2] FIG. 2 is a perspective view mainly showing a temporary cofferdam panel of the joint structure. [Figure 3] FIG. 3 is a process explanatory diagram showing the cofferdam assembly and press-in process of the cofferdam construction method according to this embodiment. [Figure 4] FIG. 4 is a process explanatory diagram showing the process of excavating inside the cofferdam in the cofferdam construction method according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of a joining structure between temporary cofferdam panels and a temporary cofferdam construction method according to the present invention will be described in detail with reference to the drawings.

[0016] [Joint structure between temporary cofferdam panels] First, a joint structure 1 for temporary cofferdam panels according to an embodiment of the present invention (hereinafter simply referred to as the joint structure 1) will be described with reference to Figures 1 and 2. Figure 1 is a horizontal cross-sectional view showing the joint structure 1 for temporary cofferdam panels according to this embodiment, and Figure 2 is a perspective view showing mainly a temporary cofferdam panel 2 of the joint structure 1. As shown in Figure 1, this joint structure 1 is composed of a plurality of temporary cofferdam panels 2, 2, which serve as temporary cofferdam bodies, and tendons 3 that tension the panels and apply lateral prestress to the joints between the vertical surfaces of the temporary cofferdam panels 2, 2. Here, the lateral direction does not have to be strictly horizontal, but refers to the inclusion of a horizontal vector component of the prestress between the vertical surfaces of the temporary cofferdam panels 2, 2.

[0017] (Temporary closing panel) As shown in Figures 1 and 2, the temporary cofferdam panel 2 is composed of a temporary cofferdam body 20 made of steel plate that blocks water, a plurality of stiffeners 21 attached to the inner surface of the temporary cofferdam body 20 to prevent deformation when an external force acts on the temporary cofferdam body 20, an upper flange 22 attached along the upper end of the temporary cofferdam body 20, and a lower flange 23 attached along the lower end of the temporary cofferdam body 20. This temporary cofferdam panel 2 is made up of multiple panels, each 250 mm to 350 mm thick overall, connected together to form the temporary cofferdam body 10, which can be installed around an existing underwater structure to seal it off and prevent water from entering inside, creating a work space.

[0018] The temporary cofferdam body 20 according to this embodiment is made of curved steel plates of a predetermined thickness that are arc-shaped in plan view, as shown in Figures 1 and 2. Of course, the thickness, size, shape, etc. of the temporary cofferdam body 20 are determined by appropriate structural design depending on the shape and size of the underwater structure to be installed, the water depth, and the strength of the water current.

[0019] The stiffeners 21 are made of shaped steel such as I-beams or H-beams, and are welded vertically to the inner circumferential surface of the temporary cofferdam body 20, which is made of the curved steel plate described above. In the illustrated embodiment, three stiffeners 21 are attached, but this number can be appropriately determined by structural design depending on the external force acting and the thickness of the stiffeners 21, etc., and since the temporary cofferdam panels 2 are connected to each other in the horizontal direction, it is sufficient that at least two stiffeners are attached along the left and right ends of the temporary cofferdam body 20.

[0020] As shown in FIG. 2, the stiffener 21 has a plurality of insertion holes 24 drilled at least at two locations, at the top and bottom, through which the tension members 3 described below are inserted.

[0021] As shown in FIG. 2, the upper flange 22 and the lower flange 23 have the same shape and are made of a strip-shaped steel plate of a predetermined thickness that corresponds to the curved shape (curvature) of the inner peripheral surface of the temporary cofferdam body 20.

[0022] As will be described later, when the reaction force of the press-fitting of the temporary closing panel 2 is taken from the earth anchor, the upper flange 22 and the lower flange 23 are provided with insertion holes (not shown) through which tendons connected to the earth anchors can be inserted.

[0023] (Tension material) The tendon 3 according to this embodiment is a PC steel strand such as a PC steel wire. However, the tendon according to the present invention may also be a continuous fiber reinforced material, which is a composite material made by combining carbon fiber, aramid fiber, or glass fiber with epoxy resin, vinyl ester resin, or the like.

[0024] [Joint structure between temporary cofferdam panels] Next, a temporary cofferdam construction method according to an embodiment of the present invention will be described with reference to Figures 3 and 4. In the temporary cofferdam construction method according to this embodiment, a temporary cofferdam body, which is a temporary structure, is constructed around a pier P1 of an existing bridge spanning a river, which is an existing underwater structure, and is made up of the above-mentioned temporary cofferdam panels joined together by a joint structure 1.

[0025] (Temporary cofferdam assembly and press-fit process) As shown in Figure 3, the cofferdam construction method according to this embodiment involves a cofferdam assembly and press-in process in which a cofferdam, which is a temporary structure, is assembled and pressed in using a press-in device. Figure 3 is a process explanatory diagram showing the cofferdam assembly and press-in process of the cofferdam construction method according to this embodiment.

[0026] First, above the water surface of the river, the aforementioned multiple temporary cofferdam panels 2 are tensioned and prestressed with tendons 3 to unite them, and then assembled to form the cylindrical temporary cofferdam body 10. The ends of the tendons 3 are hooked and fixed into the insertion holes 24 of the stiffeners 21 with fixing devices (not shown) (see also Figure 2).

[0027] In this process, instead of joining the panels with bolts as in the past, horizontally adjacent temporary cofferdam panels 2 are integrated by tensioning them with tendons 3, which reduces the time required to tighten the bolts and significantly improves work efficiency. Of course, adjacent temporary cofferdam panels 2 can also be temporarily fastened together with bolts before tensioning them with tendons 3.

[0028] Furthermore, in the temporary cofferdam body 10, the temporary cofferdam panels 2 are tightly integrated by tensioning and prestressing them with the tendons 3, so the temporary cofferdam body 20 can be made thin and the size and number of the stiffeners 21 can be reduced, reducing the cost of the temporary cofferdam panels 2. Furthermore, unlike conventional temporary cofferdam construction methods, the temporary cofferdam body 10 does not require the installation of bracing beams. Since the size of the bracing beams can at least be reduced, the overall size of the temporary cofferdam body 10 can be reduced, thereby reducing the cofferdam area and the force resisting the river water flow.

[0029] Next, the temporary cofferdam 10 is lowered below the river water surface under its own weight, and the temporary cofferdam 10 is added to the upper part (above) of the temporary cofferdam by prestressing the temporary cofferdam panels 2 together with the tendons 3 in the same manner as described above, either above or underwater. By repeating this process of adding and lowering temporary cofferdams 10, the lower ends of the temporary cofferdams 10 are seated on the riverbed (bottom of the water), and a cylindrical temporary cofferdam 10 is constructed, extending from above the water surface to the bottom. As shown in Figure 3, the lowest part of the temporary cofferdam 10 has a triangular cross section with a sharp cutting edge at the bottom end to reduce resistance when the ground is pressed in.

[0030] After that, a press-in device P consisting of multiple hydraulic jacks is installed on the existing pier P1 above the water surface, which is fixed with anchors or the like to obtain reaction force from the existing pier P1. Then, this press-in device P presses the cylindrical temporary cofferdam 10 into the ground of the riverbed (bottom) via pressure steel members 4 suspended across the top end of the temporary cofferdam 10. The depth to which the temporary cofferdam 10 is pressed in is slightly deeper than the top surface of the existing caisson foundation F1, as shown in Figure 3.

[0031] The timing for installing the press-in device P may be during the construction of the temporary cofferdam 10 or in the preparation stage before construction. In short, the press-in device P may be constructed at any time as long as it is constructed before the temporary cofferdam 10 is pressed into the ground. In addition, the reaction force when pressing the temporary cofferdam 10 into the ground does not have to be obtained from the pier P1, which is an existing structure, as shown in the figure, but may be obtained from an earth anchor buried in the ground or foundation, as in Patent Document 2.

[0032] Furthermore, although a cylindrical shape has been exemplified as the temporary closure body 10 in this embodiment, the temporary closure body in accordance with the present invention is not limited to a cylindrical shape, and may have any shape such as an oval, elliptical, or rectangular horizontal cross section that can ensure a predetermined distance around the pier P1, which is an existing underwater structure.

[0033] (Excavation process inside the cofferdam) Next, as shown in Figure 4, in the cofferdam method according to this embodiment, an excavation step is carried out in which the soil and sand above the existing caisson foundation F1 and inside the temporary cofferdam 10 that was assembled and pressed in in the previous step is excavated and removed while leaving the water inside the temporary cofferdam 10 without draining it to the bottom. Figure 4 is a process explanatory diagram showing the excavation step inside the cofferdam in the cofferdam method according to this embodiment.

[0034] In this process, a diver dives into the water inside the temporary cofferdam 10 and excavates the soil covering the existing caisson foundation F1 below the waterline, as well as the soil and sand accumulated on top of it, until the top surface of the existing caisson foundation F1 is exposed. After that, a suction pump, dredging bucket, backhoe, etc. are used to remove the excavated soil and sand to the outside of the temporary cofferdam 10, creating a dry work space for investigating and repairing / reinforcing the existing underwater structures, such as the pier P1 and the existing caisson foundation.

[0035] According to the joint structure 1 between temporary cofferdam panels and the temporary cofferdam construction method of this embodiment described above, by applying prestress in the lateral direction, a compressive force acts on the vertical joint surfaces of the temporary cofferdam panels 2, which helps resist external forces and makes bracing beams unnecessary, or at least reduces the size of the bracing beams, making the cofferdam area smaller than conventional cofferdam areas. This makes it possible to further reduce river obstruction.

[0036] Furthermore, according to the joining structure 1 between temporary closure panels and the temporary closure construction method of this embodiment, the temporary closure panels 2 are firmly integrated together, so that the temporary closure body 20 can be made thinner and the size and number of the stiffeners 21 can be reduced, thereby reducing the manufacturing cost of the temporary closure panels 2.

[0037] In addition, with the conventional resistance method using bolt joints and bracing beams, external forces are resisted by the shear resistance force generated by the bolt bearing pressure, so resistance occurs after deformation has occurred and deformation cannot be suppressed. However, with the joint structure 1 between temporary cofferdam panels and the temporary cofferdam construction method according to this embodiment, prestress pressure is applied to the joints of the temporary cofferdam panels 2 by the tendons 3, so resistance action is expected from the moment the change occurs, making it possible to suppress deformation compared to existing methods.

[0038] Although the cofferdam construction method according to the embodiment of the present invention has been described in detail above, the above-mentioned and illustrated embodiments are merely specific embodiments for carrying out the present invention, and therefore the technical scope of the present invention should not be interpreted as being limited by them. [Explanation of symbols]

[0039] 10: Temporary cofferdam 1: Joint structure (between temporary closing panels) 2: Temporary closing panel 20: Temporary closing body 21: Stiffener 22: Upper flange 23: Lower flange 24:Through hole 3: Tensile material 4: Pressure steel P: Press-fitting device P1: Existing pier F1: Existing caisson foundation

Claims

1. A joint structure for joining temporary cofferdam panels that are installed around an existing underwater structure to seal off the inside and create a work space, Tendons are inserted into the joints between the temporary cofferdam panels in the horizontal direction, and prestress is introduced into the joints between the temporary cofferdam panels in the horizontal direction by the tendons. A joint structure between temporary closing panels characterized by the above.

2. The vertical joints between adjacent panels of the temporary cofferdam panel in the horizontal direction shall not be bolted.

2. The joining structure for temporary closing panels according to claim 1,

3. A temporary cofferdam construction method in which a temporary cofferdam body joined by the joining structure of temporary cofferdam panels according to claim 1 or 2 is installed around an existing underwater structure to construct a dry work space, The temporary cofferdam body is constructed by assembling multiple cofferdam panels together using tensioning materials to apply prestress to them. A temporary cofferdam construction method characterized by the following.

4. Do not install bracing beams inside the temporary cofferdam. The temporary cofferdam construction method according to claim 3, characterized in that:

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