JP2013091969A - Cofferdam structure of dam body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive cofferdam structure with proper workability by reducing a dead space of an inner space.SOLUTION: A cofferdam structure 100 for use in construction of a through-hole in an existing dam body 1 includes a cylindrical body 20, one opening 21 of which abuts on an upstream surface 3 of the dam body so as to surround a position 4a where the through-hole 2 is to be opened, and a semielliptic dome body 10 which closes the other opening 22 of the cylindrical body 20 and the cross-section of which assumes a convex shape to the upstream side of the dam body.

Description

  The present invention relates to a temporary closing structure for a dam dam body, and specifically relates to a technique for a temporary closing structure that is low in cost and has good workability by reducing dead space in the interior.

  Through holes in the dam body of the existing dam for the purpose of securing a sediment discharge path on the upstream side of the dam body, a new water discharge path for the purpose of increasing flood control capacity, or a small hydroelectric generator installation area The number of cases of building is increasing. Conventionally, when constructing a through-hole in an existing dam body, a large-scale temporary cut-off work has been carried out to reach the bottom of the water upstream of the dam body, and the inside of the cut-off structure has been dried up to drill the through-hole. It was. However, such a method has a problem that the temporary deadline structure becomes large and the construction period and construction cost increase. Therefore, as a technology that enables temporary closing of dam water areas at a small scale and low cost, for example, a temporary closing structure (Patent Document 1) in which a spherical water blocking wall is attached to the surface of the dam dam body is proposed. Has been.

JP 2004-263380 A

  However, when adopting the above-mentioned conventional temporary closing structure for actual construction, hemispherical water stoppage is ensured while placing materials such as gates and space for various operations in the interior of the hemispherical water stop wall. In order to completely cover the opening of the through hole with the opening of the wall, it is necessary to make the opening of the hemispherical water blocking wall considerably larger than the opening of the through hole. In that case, a large dead space is generated in the peripheral portion of the hemisphere, and the inner space is increased accordingly. For this reason, when the inside of the hemispherical water blocking wall is drained, a large buoyancy is applied to the temporary closing structure, and countermeasures are required. In addition, since the hemispherical water blocking wall itself becomes large, the costs and labor of manufacturing, transporting, and installing the hemispherical water blocking wall are also increased.

  Accordingly, an object of the present invention is to provide a temporary closing structure with low cost and good workability by reducing the dead space in the interior.

  The temporary closing structure of the dam dam body of the present invention that solves the above problems is a temporary closing structure used when constructing a through hole in an existing dam dam body, and one opening surrounds the planned opening position of the through hole. The cylindrical body is in contact with the upstream surface of the dam body, and the other opening of the cylindrical body is closed, and a semi-elliptical dome body having a convex section on the upstream side of the dam body is characterized.

  According to such a provisional deadline structure, the cylindrical body is installed so as to surround the planned opening position of the through hole, and the minimum necessary space for placing materials and equipment such as an opening / closing gate of the through hole or for various operations is provided. Only the dam dam body upstream surface extends in the upstream direction. In addition, the opening on the upstream side of the dam bank in the cylindrical body is closed not by a hemisphere but by a flat dome having a semi-elliptical cross section.

  Due to such a structure, there is no dead space generated in the peripheral portion of the hemispherical water blocking wall in the prior art, and the volume of the inner space can be reduced by that amount compared to the conventional temporary closing structure. Due to the reduction of the internal air, the buoyancy generated in the temporary closing structure when draining the water in the internal air is also reduced as compared with the prior art, and the burden of measures against buoyancy is reduced. In addition, the size and weight of the temporary closing structure itself are also reduced as compared with the prior art, and the costs and labor of manufacturing, transporting, and installing the temporary closing structure can be made smaller than before. Further, by closing the opening end of the cylindrical body with the dome body, the strength of the cylindrical body integrated with the dome body also becomes appropriate, and the external force due to water pressure can be appropriately resisted. Further, such a cylindrical body has a high resistance to external water pressure in the radial direction. ADVANTAGE OF THE INVENTION According to this invention, the temporary deadline structure with favorable workability can be provided at low cost by reducing the dead space of inner space.

  In the temporary closing structure of the dam dam body, a ring-shaped rib member may be provided on the outer peripheral surface of the cylindrical body. According to this rib material, the cylindrical body that tends to be a weak point against an external force due to water pressure is appropriately reinforced, and as a result, the thickness of the cylindrical body itself (before the rib material is attached) is reduced to reduce the weight of the cylindrical body. I can do it. A lightweight cylindrical body can be easily transported and installed, and the cost and labor for that purpose can be reduced.

  Further, in the temporary closing structure of the dam dam body, the rib material may have a connection structure with an anchor placed on the ground upstream of the dam dam body. Assume that anchors are placed in the foundation ground at the bottom of the dam body upstream. In this case, a connecting tool such as a hook provided at the tip of the wire extending from the anchor is connected to a connection receiving jig (eg, hooking ring or hole) provided in the rib material, and the rib material and the anchor are connected. If such a connection structure is adopted, it is possible to prevent the temporary fastening structure from being lifted by taking a reaction force against the anchor in the ground against the buoyancy generated when draining the water in the temporary fastening structure.

  In the temporary closing structure of the dam dam body, the cylindrical body and the dome body may be detachably fixed. The end surface of one opening of the cylinder (the opening that contacts the upstream surface of the dam dam body and surrounds the planned opening of the through hole) is such that the upstream surface of the dam dam body is the bottom It is necessary to process according to the angle which stands more. On the other hand, since the angle at which the dam dam body upstream surface stands from the bottom of the dam varies from dam to dam, if the cylindrical body and the dome body are integrated, the entire temporary cutoff structure including the dome body is used up for each dam. End up. However, when the cylindrical body and dome body are detachably fixed, the dome body is separated from the original cylindrical body and diverted to another dam cylinder body, even if the cylindrical body has a dedicated structure for each dam. It becomes possible to suppress the manufacturing cost of the temporary closing structure as a whole.

  In the temporary closing structure of the dam dam body, the cross-sectional shape of the dome body may be a substantially semi-ellipse formed by joining two types of arcs having different radii. Processing a member having a predetermined strength, such as a steel material, so that the cross-sectional shape thereof becomes an accurate elliptical shape is likely to be troublesome and costly. Therefore, the semi-ellipse adopted as the cross-sectional shape of the dome body is also formed into a semi-elliptical cross-sectional shape by connecting two kinds of arcs having different radii such as a small arc near the dome body peripheral edge and a large arc near the top of the dome body. If so, it is possible to reduce labor and cost when manufacturing the dome body.

  ADVANTAGE OF THE INVENTION According to this invention, the temporary deadline structure with favorable workability can be provided at low cost by reducing the dead space of inner space.

It is a general view which shows the structural example of the temporary closing structure in this embodiment. It is an exploded view which shows the structural example of the temporary closing structure in this embodiment. It is a figure which shows the cross-sectional shape example of the dome body in this embodiment. It is a figure which shows the construction procedure 1 of the temporary closing structure in this embodiment. It is a figure which shows the construction procedure 2 of the temporary closing structure in this embodiment. It is a figure which shows the construction procedure 3 of the temporary closing structure in this embodiment. It is a figure which shows the construction procedure 4 of the temporary closing structure in this embodiment. It is a figure which shows the construction procedure 5 of the temporary closing structure in this embodiment. It is a figure which shows the construction procedure 6 of the temporary closing structure in this embodiment. It is a figure which shows the construction procedure 7 of the temporary closing structure in this embodiment.

  Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an overall view showing a structural example of a temporary closing structure of a dam dam body in the present embodiment, and FIG. 2 is an exploded view showing a structural example of the temporary closing structure. The temporary closing structure 100 in the present embodiment is a temporary closing structure on the upstream side of the dam body used in the construction of the through hole 2 such as a sand pit in the dam body 1 of the existing dam. As shown in FIGS. 1 and 2, the temporary cutoff structure 100 of the present embodiment is configured by a dome body 10 and a cylindrical body 20.

  The cylindrical body 20 has one opening 21 in contact with the upstream surface 3 of the dam bank via the water blocking material 7 and surrounds the planned opening position 4 a of the through hole 2. Therefore, the diameter of the opening 21 of the cylindrical body 20 is larger than the diameter of the opening 4 of the through hole 2. The other opening 22 of the cylindrical body 20 is closed by the dome body 10. An air supply valve 27 and a manhole 28 are provided at the upper outer periphery of the cylindrical body 20, and a drainage valve 29 is provided at the lower outer periphery.

  The air supply valve 27 is connected to an air supply device on the bank body 2 via an appropriate air supply path, and is a valve for guiding air to the cylindrical body 20, that is, the inner space 25 of the temporary cutoff structure 100. The manhole 28 is an opening / closing port serving as an entrance / exit of a worker who performs work in the inner space 25 of the temporary closing structure 100. The manhole 28 includes a valve (not shown), and can be opened and closed between the inner space 25 and the outside of the manhole. The drain valve 29 is a valve for draining water from the inner space 25 of the temporary closing structure 100 to the outside.

  The protruding length 26 (FIG. 2) on the upstream side of the dam dam body of the cylindrical body 20 is a minimum space required for placing materials and equipment such as an opening / closing gate of the through hole 2 or for various operations. The length is as long as it is secured in the inner space of the cylindrical body 20.

  On the other hand, the dome body 10 is closed by bringing the other opening 22 of the cylindrical body 20 and its own opening 11 into contact with each other in a watertight manner, and the cross section is convex on the upstream side of the dam dam body. It has a structure. As the semi-elliptical cross-sectional shape of the dome body 10, a combination of two arcs having different radii is adopted in the present embodiment, but a mathematically accurate semi-ellipse or semi-circle is flattened. Also included are continuous curves.

  As shown in FIG. 2, in the opening 11 of the dome body 10, a flange 12 having an appropriate width is provided on the end surface that is in watertight contact with the end surface of the opening 22 of the cylindrical body 20. On the other hand, the end face of the opening 22 of the cylindrical body 20 is also provided with a flange 23 that also serves as the rib member 30. The cylindrical body 20 and the dome body 10 are integrally fixed by joining the flange 12 and the flange 23 in a state of being in watertight contact with each other. When joining the flanges, a water-stopping material such as butyl rubber is sandwiched between the contact surfaces, and the flanges are fastened with bolts or the like so as to be detachable.

  As described above, in the temporary cutoff structure 100 of the present embodiment, the cylindrical body 20 and the dome body 10 are detachably fixed by means such as bolt fastening via the flange 12 and the flange 23. The end surface of one opening 21 of the cylindrical body 20 (opening that contacts the upstream surface 3 of the dam dam body and surrounds the opening 4 of the through hole 2) is arranged so that the cylindrical body 20 is substantially parallel to the foundation ground 5 of the water bottom. It is necessary to process according to the angle at which the dam dam body upstream surface 3 is erected from the bottom of the water. On the other hand, since the angle at which the dam dam body upstream surface 3 stands up from the bottom of the dam is different for each dam, when the cylindrical body 20 and the dome body 10 are an integral object, the entire temporary cut-off structure 100 including the dome body 10 can be It will be used up every time. However, when the cylindrical body 20 and the dome body 10 are detachably fixed as in the present embodiment, the cylindrical body 20 has a semi-elliptical cross section even if it is a dedicated structure for each dam. Therefore, the dome body 10 having a high manufacturing cost can be separated by unfastening the bolt fastening with the original cylindrical body 20, and can be diverted to a cylindrical body for another dam.

  A ring-shaped rib member 30 is provided on the outer peripheral surface 24 of the cylindrical body 20. The rib member 30 is a stiffener for the cylindrical body 20. By providing such a rib member 30, the thickness of the cylindrical body itself can be reduced (before the rib member 30 is attached), and the weight of the cylindrical body 20 can be reduced. The weight-reduced cylindrical body 20 can be easily transported and installed, and the cost and labor for that purpose can be reduced.

  Further, as illustrated in FIG. 1, for example, anchors placed on the foundation ground 5 on the bottom of the dam dam body upstream at the lower ends of the rib member 30 also serving as the flange 23 and the rib member 30 adjacent thereto. If it has the connection structure 31 with 60, it is suitable. The connection structure 31 exemplified in this embodiment includes a skirt-like plate 32 in which the lower end of the rib member 30 extends downward, and a hooking hole 33 provided in the plate 32. In this case, the hook 61 provided at the tip of the anchor 60 (wire extending from) placed in the foundation ground 5 is hooked into the hooking hole 33 provided in the connection structure 31 described above, The rib member 30 and thus the cylindrical body 20 and the anchor 60 can be connected. If such a connection structure 31 is adopted, the buoyancy generated when draining the water in the temporary closing structure is counteracted by the anchor 60 in the foundation ground 5 to suppress the floating of the temporary closing structure 100. I can do it.

  The cross-sectional shape of the convex portion 15 in the dome body 10 is preferably a substantially semi-elliptical shape in which two types of arcs having different radii are combined. FIG. 3 shows an example of a cross-sectional shape of the dome body 10 in the present embodiment. In the example of FIG. 3, the cross-sectional shape of the convex portion 15 of the dome body 10 is approximately semi-elliptical, and the ratio of the major axis to the minor axis is major axis: minor axis = 1: 0.5. However, the convex portion 15 of the dome body 10 needs to be manufactured by press bending of a steel plate, and in order to manufacture this as a standard ellipse, a mold whose curvature radius is continuously changed is required. It is uneconomical. Therefore, in this embodiment, the cross section of the approximate ellipse obtained by combining two arcs having different radii is the cross sectional shape of the convex portion 15. In the example of FIG. 3, in the cross section of the dome body 10, a small arc with a radius a is arranged on the line segment X near the contact surface with the cylindrical body 20, and a large arc with a radius A is arranged on the other line segment Y, These arcs are combined to form a semi-elliptical cross-sectional shape.

  In the temporary closing structure 100 having the above-described structure, the cylindrical body 20 having the opening 21 covering the entire opening 4 of the through hole 2 is used for placing materials and equipment such as an opening / closing gate of the through hole 2 or various types. It is installed in a form extending in the upstream direction from the upstream surface 3 of the dam dam body by the minimum necessary space for work. Moreover, the opening 22 on the upstream side of the dam dam body in the cylindrical body 20 is closed not by the hemisphere but by the flat dome body 10 having a semi-elliptical cross section. Therefore, the dead space which is a problem in the prior art can be greatly reduced. Since the inner space 25 is reduced by the amount of the dead space, the buoyancy generated in the temporary closing structure 100 when draining the water in the inner space is reduced as compared with the conventional case, and the burden of measures against buoyancy is reduced. In addition, the size and weight of the temporary closing structure itself are also reduced as compared with the prior art, and the costs, labor, and labor of manufacturing, transporting, and installing the cylindrical body 20 and the dome body 10 constituting the temporary closing structure 100 are also smaller than before. And can.

  In the construction of the through hole 2, the temporary closing structure 100 is installed in advance at the position of the opening 4 on the upstream side of the through hole 2 (expected opening position 4 a), and the water existing in the inner space 25 of the temporary closing structure 100 is drained. As a result, the temporary closing structure 100 is pressed against the upstream surface 3 of the dam dam body, and a work space is secured.

  Next, the construction procedure of the temporary closing structure 100 of this embodiment will be described in detail. 4-10 is a figure which shows each construction procedure 1-7 of the temporary closing structure in this embodiment, respectively. First, as shown in FIG. 4, the temporary cutoff structure 100 is suspended from the upper part of the dam body by a crane 80 and is submerged to a place (on an underwater temporary gantry) where the discharge pipe 48 is located on the upstream surface 3 of the dam body. (Procedure 1). In addition, a closed gate door body 49 (FIG. 9) of a discharge pipe outlet is placed in advance in the inner space 25 of the temporary closing structure 100, both of which are large in size and weight, and are carried together to the site. It is impossible to do. Therefore, after completion of the inspection at the factory, these are divided and transported to the construction site and assembled near the dam body (not shown). Moreover, the anchor 60 is previously installed in the installation position of the temporary closing structure 100 in the foundation ground 5 on the upstream side of the dam body by diving work or the like.

  Further, as shown in FIG. 5, watertight processing such as sandwiching and fixing between the opening 21 of the cylindrical body 20 and the dam body upstream surface 3 in the temporary closing structure 100 with a waterstop material is performed (procedure 2). In addition, the anchor 60 that has been placed in advance is connected to a connection structure 31 provided in the lower portion of the temporary cutoff structure 100, and the temporary cutoff structure 100 and the anchor 60 are connected via the connection structure 31.

  Subsequently, as shown in FIG. 6, the manhole tube 8 is suspended from the dam body by a crane 81 and connected to the manhole 28 of the temporary closing structure 100, and another manhole is connected to the upper end of the manhole tube 8 connected to the manhole 28. The tubes 8 are sequentially connected (procedure 3). In installing the manhole tube 8, a work table ship 40 is floated in the water area upstream of the dam body, an operator is placed, the manhole tube 8 suspended by the crane 81 is positioned, the manhole 28 and the manhole tube 8 are connected, In addition, the manhole tube 8 is connected to each other. The manhole pipe 8 is temporarily fixed to the dam body upstream surface 3 with an appropriate tipping prevention material 9 such as a steel bar.

  Next, as shown in FIG. 7, the air supply hose 42 is extended from the pump 41 installed on the work table ship 40 and connected to the air supply valve 27 of the temporary cutoff structure 100, so that the inner space 25 of the temporary cutoff structure 100 is obtained. The supply of pressurized air to is started (procedure 4). At the same time, the drain valve 29 of the temporary closing structure 100 is opened, and the water existing in the inner space 25 of the temporary closing structure 100 is discharged along with the air filling by the above-described supply air, and the inner space 25 is brought into a dry state. To do. When air bubbles start to be ejected from the drain valve 29 of the temporary closing structure 100 during the above-described supply of pressurized air, it means that the drainage valve 29 and the air supply valve 27 are completely drained. Is closed, the valve of the manhole 28 is opened, the pressurized air is gradually released, and the inner space 25 is set to atmospheric pressure. Thus, the inner space 25 becomes atmospheric pressure, and the temporary cutoff structure 100 is pressed against the upstream surface 3 of the dam body by water pressure, and is held at the underwater position by the connection of the anchor 60 and the connection structure 31.

  When draining the water in the inner space 25, a submersible pump set in advance in the inner space 25 is operated with the above-described air supply valve 27 and drain valve 29 closed, and the upper end of the manhole pipe 8 is operated. Alternatively, a method of draining water may be employed.

  The buoyancy generated when draining the interior of the temporary closing structure 100 is much larger than the air weight of the temporary closing structure 100. On the other hand, if the temporary closing structure 100 is pressed against the dam dam body upstream surface 3 by water pressure, a frictional force is generated between the dam body upstream surface 3 and the temporary closing structure 100 to reduce buoyancy. Since this buoyancy is generated when pressure air is sent to the inner space 25 in order to discharge the water in the inner space 25, a reduction in buoyancy due to the frictional force cannot be expected. Therefore, the load assumed for the anchor 60 is set to be equal to or larger than the total buoyancy applied to the temporary cutoff structure 100. In addition, since the period in which this buoyancy countermeasure is required is only during work by an operator in the inner space 25 of the temporary closing structure 100, it is designed as a temporary anchor. Such an anchor 60 can employ a stranded wire of PC steel.

  Subsequently, as shown in FIG. 8, a management corridor 43 is provided above the uppermost manhole pipe 8 among the connected manhole pipes 8. It enters the inner space 25 of the temporary cutoff structure 100 through the manhole tube 8 and the manhole 28 (procedure 5). The worker who enters the inner space 25 confirms that the inner space 25 is in a drained state. On the other hand, it is assumed that an appropriate excavator such as a loader 85 excavates the through hole 2 from the downstream side of the bank body. After confirming the drainage completion state of the inner space 25, the loader 85 performs excavation of a portion left between the inner space 25 of the temporary closing structure 100 and the drilled through hole 2.

  When this excavation is completed and the inner space 25 and the through hole 2 of the temporary closing structure 100 are penetrated, as shown in FIG. 9, the installation of the closing gate door body door 47 and the bell mouth 46 and the air pipe 45 are performed. (Procedure 6). In this case, the closed gate door body door stop 47 and the bell mouth 46 previously placed in the inner space 25 of the temporary closing structure 100 are installed on the bank body 1, and the discharge pipe from the downstream of the bank body in the through hole 2. 48 is carried in, and the discharge pipe 48 is connected to the closed gate door body 49 and the bell mouth 46. Further, the closed gate door body 49 is connected to the door 47 for the closed gate door body and the bell mouth 46.

  After this connection is completed, concrete is placed in a predetermined region such as a gap between the discharge pipe 48 and the inner wall of the through hole 2. In addition, the worker who has been working in the inner space 25 of the temporary closing structure 100 is made to leave on the work table boat 40 on the water or the management corridor 43 through the manhole pipe 8.

  Subsequently, the air supply valve 28 and the drain valve 29 are opened, and the inner space 2 of the temporary closing structure 100 is filled with water. Further, as shown in FIG. 10, the manhole pipe 8 connected to the manhole 28 is sequentially removed, the connection between the temporary closing structure 100 and the anchor 60 is released, and the temporary closing structure 100 is also lifted by the crane 80 and removed. (Procedure 7).

  As described above, according to the present embodiment, it is possible to provide a temporary closing structure with low cost and good workability by reducing the dead space in the sky.

  Although the embodiment of the present invention has been specifically described based on the embodiment, the present invention is not limited to this, and various modifications can be made without departing from the scope of the invention. For example, in the temporary closing structure of the above embodiment, the cylindrical body and the dome body can be separated from each other, but a structure in which both are integrally welded may be adopted. Further, when a means other than an anchor is employed as a countermeasure against buoyancy acting on the temporary closing structure, it is not necessary to provide the above-described connecting structure on the rib member. Further, if the cylindrical body has a strength capable of sufficiently resisting the external pressure, it is not necessary to provide a rib material.

DESCRIPTION OF SYMBOLS 1 Bank body 2 Through-hole 3 Dam dam body upstream surface 4 Opening 4a Through-hole planned opening position 5 Foundation ground 7 Water stop material 10 Dome body 11 Opening 12 Flange 15 Protruding part 20 Cylindrical body 21 One opening 22 The other opening 23 Flange 24 Outer peripheral surface 25 Inner air 26 Projection length 27 Air supply valve 28 Manhole 29 Drain valve 30 Rib material 31 Connection structure 32 Plate 33 Hooking hole 45 Air pipe 46 Bell mouth 47 Closed gate door door 48 Discharge pipe 49 Closed gate door body 60 Anchor 61 Hook 100 Temporary closing structure

Claims (5)

It is a temporary deadline structure used when constructing a through hole in an existing dam body.
A cylindrical body that abuts the dam dam body upstream surface so that one opening surrounds the planned opening position of the through hole;
A semi-elliptical dome that closes the other opening of the cylindrical body and has a cross-section projecting upstream of the dam dam body;
A temporary closing structure of a dam body characterized by comprising In claim 1,
A temporary closing structure for a dam dam body, characterized in that a ring-shaped rib member is provided on the outer peripheral surface of the cylindrical body. In claim 2,
A temporary closing structure for a dam dam body, wherein the rib member has a connection structure with an anchor placed on the ground upstream of the dam dam body. In any one of Claims 1-3,
A temporary closing structure for a dam dam body, wherein the cylindrical body and the dome body are detachably fixed. In any one of Claims 1-4,
A cross-sectional shape of the dome body is a substantially semi-ellipse formed by joining two types of arcs having different radii, and a temporary closing structure of a dam dam body.

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