JP5789489B2 - Temporary deadline structure of dam body - Google Patents

Description

  The present invention relates to a temporary closing structure of a dam dam body, and specifically relates to a technique of a temporary closing structure that can reliably cope with buoyancy acting during construction.

  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

In the above-described conventional temporary cutoff structure technology, the underwater hemispherical water blocking wall is pressed against the dam dam body by water pressure, and a frictional force is generated between them. It is based on the premise that the water wall will be fixed. On the other hand, when such a conventional temporary closing structure is adopted in actual construction, the inventors have found that a hemispherical water blocking wall drained from inside has a much larger buoyancy than its own aerial weight. Has been obtained. Moreover, since this buoyancy is generated when draining the inside of the hemispherical water blocking wall before the above-mentioned friction force is sufficiently exerted, it is expected that the buoyancy is countered by the friction force. It is a danger.
On the other hand, when the peripheral part of the temporary closing structure is fixed by driving an anchor to the dam dam body around the through hole, when the large buoyancy as described above is applied to the temporary closing structure, the anchor receiving the buoyancy There is also a concern that the dam dam around the through hole may be damaged by the reaction force.
That is, in the prior art, countermeasures have not been sufficiently taken into account for buoyancy applied to the temporary closing structure during construction.

  In view of this, an object of the present invention is to provide a technique of a temporary closing structure that can reliably cope with buoyancy acting during construction.

  The temporary closing structure of the dam dam body of the present invention that solves the above-mentioned problem is a temporary closing structure used when constructing a through hole in an existing dam dam body, and the upstream surface of the dam dam body so as to surround the planned opening position of the through hole The dome body is in contact with the dome body, and the anchor is connected to the dome body.

  According to such a temporary closing structure, the dome body can be prevented from being lifted against the buoyancy generated when the water in the dome body is drained by reacting with the anchor that has been placed. The anchor connected to the dome body is assumed to be driven at the bottom of the water on the upstream side of the dam body. As the water bottom, in addition to the water bottom ground on the upstream side of the dam dam body, a predetermined structure capable of placing an anchor such as the bottom of the dam body upstream side of the dam dam body is included.

  In the case of the above structure, a hook or other connecting tool provided at the tip of the wire extending from the anchor is connected to a connection receiving jig (eg, hooking ring or hole) provided on the outer periphery of the dome body, and the dome body and the anchor are connected. Let ADVANTAGE OF THE INVENTION According to this invention, the temporary closing structure which can respond reliably to the buoyancy which acts at the time of construction can be provided.

  ADVANTAGE OF THE INVENTION According to this invention, the temporary closing structure which can respond reliably to the buoyancy which acts at the time of construction can be provided.

It is a general view which shows the structural example of the temporary closing structure 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. 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 FIG. 1, the provisional deadline structure 100 of the present embodiment includes a dome body 10 having a semi-elliptical structure whose cross section is convex on the upstream side of the dam dam body, and a water bottom that is the dome body 10 and the water bottom 5. It is comprised with the anchor 60 which connects the ground (henceforth the water bottom ground 5).

  The dome body 10 has an opening 21 that abuts the dam dam body upstream surface 3 via a water blocking material 7 and surrounds the planned opening position 4 a of the through hole 2. An air supply valve 27 and a manhole 28 are provided at the upper outer periphery of the dome body 10, and a drain 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 through an appropriate air supply path, and is a valve for guiding air to the inner space 25 of the dome body 10, that is, 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.

  A ring-shaped rib member 30 is provided on the outer peripheral surface 24 of the dome body 10. This rib member 30 is a stiffener for the dome body 10. By providing such a rib member 30, the thickness of the dome body 10 itself can be reduced (before the rib member 30 is attached), and the dome body 10 can be reduced in weight. The weight-reduced dome body 10 can be easily transported and installed, and the cost and labor for that purpose can be reduced.

  The lower end of the rib member 30 has a connection structure 31 with an anchor 60 placed on the water bottom ground 5 on the upstream side of the dam dam body. 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 water bottom ground 5 is hooked into the hooking hole 33 provided in the connection structure 31 described above, The rib member 30 and thus the dome body 10 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 cutoff structure is counteracted by the anchor 60 in the water bottom ground 5 to suppress the floating of the temporary cutoff structure 100. I can do it.

  The anchor 60 has a structure in which a steel material or the like is inserted and fixed in a hole 6 provided in the water bottom ground 5, and includes an anchor body 120, a tension portion 130, and an anchor head 140. Among them, the anchor body 120 directly transmits the tensile force applied to the anchor 60 to the water bottom ground 5 and is formed by injecting grout into the hole 6. The tension portion 130 is a portion that transmits the tensile force from the anchor head 140 to the anchor body 120, and is a tendon made of a PC steel rod, a PC steel strand, a multiplex PC steel strand, a continuous fiber reinforcement, or the like. 131 and a sheath 132 having a function of preventing corrosion of the tendon 131 and preventing friction loss. The anchor head 140 includes a fixing tool 141 of the tendon 131 and a support plate 142 that supports the fixing tool 141 and transmits the load to the water bottom ground 5.

  In addition, in this embodiment, although the water bottom ground 5 is illustrated as a water bottom part of the dam dam body upstream side which is the placement destination of the anchor 60, as this water bottom part, the dam body 1 upstream of the dam dam body is illustrated. It is assumed that a predetermined structure such as a bottom portion on which the anchor 60 can be driven is also included.

  In constructing the through hole 2, the dome body 10 is installed in advance at the position of the upstream opening 4 in the through hole 2 (expected opening position 4 a) and connected to the anchor 60, and is present in the inner space 25 of the dome body 10. By draining the water to be used, the dome body 10 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. 2-8 is a figure which shows each construction procedure 1-7 of the temporary closing structure in this embodiment, respectively. First, as shown in FIG. 2, the dome body 10 is suspended from the upper part of the dam body by a crane 80 and submerged to a place (on the temporary gantry in water) where the discharge pipe 48 is located at the upstream side 3 of the dam body ( Procedure 1). In addition, a closed gate door body 49 (FIG. 8) or the like of a discharge pipe mouth is placed in advance in the inner space 25 of the dome body 10, both of which are large in size and weight, and are carried into the site integrally. It is impossible. 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). In addition, an anchor 60 is installed in advance at the installation position of the dome body 10 in the water bottom ground 5 on the upstream side of the bank body by diving work or the like.

  The anchor 60 is placed in the following procedure. First, a hole 6 having a predetermined diameter for anchor insertion is drilled by a boring machine, and the tendon 131 and the sheath 132 are inserted into the formed hole 6. After insertion of the tendon 131 and the sheath 132, a grout is injected into the hole 6 as the anchor body 120. After the injected grout reaches a predetermined strength, tension is applied to the tension portion 130. In addition, the support plate 142 is inserted through the upper end of the tension portion 130, and then the tension portion 130 and the anchor head 140 are integrally formed by the fixing tool 141, and the anchor 60 is completely driven.

  Following the procedure 1, as shown in FIG. 3, a watertight process such as sandwiching and fixing the opening 21 of the dome body 10 and the upstream surface 3 of the dam body with a water-stopping material in the temporary closing structure 100 is performed (procedure) 2). In addition, the anchor 60 that has been placed in advance as described above is connected to the connection structure 31 provided in the lower portion of the dome body 10, and the dome body 10 and the anchor 60 are connected via the connection structure 31. These operations are carried out in cooperation with underwater work by divers.

  Subsequently, as shown in FIG. 4, the manhole pipe 8 is suspended from the dam body by a crane 81 and connected to the manhole 28 of the dome body 10, and another manhole pipe is connected to the upper end of the manhole pipe 8 connected to the manhole 28. 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. 5, 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 dome body 10, and the dome body 10 is connected to the inner space 25. Supply of pressurized air is started (procedure 4). At the same time, the drain valve 29 of the dome body 10 is opened, and the water present in the inner space 25 of the dome body 10 is discharged along with the air filling by the above-mentioned supply air, thereby making the inner space 25 dry. When air bubbles start to be ejected from the drain valve 29 of the dome body 10 during the above-mentioned supply of pressurized air, it means that the drainage valve 29 and the air supply valve 27 are completely discharged. Then, the valve of the manhole 28 is opened and the pressure air is gradually released, and the inner space 25 is set to atmospheric pressure. Thus, the inner space 25 becomes atmospheric pressure, and the dome body 10 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.

  Note that the buoyancy generated when draining the inner space 25 of the dome body 10 is much larger than the weight of the dome body 10 in the air. For example, the inventors have found that when a dome body 10 having an opening with a diameter of 10000 mm is installed at a water depth of 17 m, the buoyancy of about 18000 kN exceeds the air weight of the dome body 10. On the other hand, if the dome body 10 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 dome body 10 to reduce buoyancy. Is generated when the water in the inner space 25 is discharged before the above-described frictional force is sufficiently exerted, and therefore it is dangerous to expect to resist buoyancy by the above-described frictional force. Therefore, the load assumed for the anchor 60 is set to be equal to or larger than the total buoyancy applied to the dome body 10. Further, since the period during which this buoyancy countermeasure is required is only during work by the worker in the inner space 25 of the dome body 10, it is designed as a temporary anchor. Such an anchor 60 can employ a stranded wire of PC steel.

  Subsequently, as shown in FIG. 6, 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 dome body 10 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 air 25, the loader 85 performs excavation of a portion left between the inner air 25 of the dome body 10 and the drilled through hole 2.

  When this excavation is completed and the inner space 25 and the through hole 2 of the dome body 10 penetrate, the installation of the closed gate door body door 47 and the bell mouth 46 and the installation of the air pipe 45 are performed as shown in FIG. Installation is performed (procedure 6). In this case, the door 47 for the closed gate door body and the bell mouth 46 previously placed in the inner space 25 of the dome body 10 are installed on the bank body 1, and the discharge pipe 48 from the downstream side of the bank body in the through hole 2. 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 dome body 10 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 27 and the drain valve 29 are opened, and the inner space 25 of the dome body 10 is filled with water. Further, as shown in FIG. 8, the manhole tube 8 connected to the manhole 28 is sequentially removed, the connection between the dome body 10 and the anchor 60 in the temporary closing structure 100 is released, and the dome body 10 is also moved by the crane 80. Lift and remove (Procedure 7).

  Thus, according to the present embodiment, it is possible to provide a temporary closing structure that can reliably cope with buoyancy acting during construction.

  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.

DESCRIPTION OF SYMBOLS 1 Bank body 2 Through-hole 3 Dam dam body upstream surface 4 Opening 4a Planned opening position of through-hole 5 Water bottom ground (water bottom)
6 hole 7 water stop material 10 dome body 21 opening 24 outer peripheral surface 25 inner air 27 air supply valve 28 manhole 29 drainage valve 30 rib material 31 connection structure 32 plate 33 hooking hole 45 air pipe 46 bell mouth 47 for closed gate door body 48 per door 48 discharge pipe 49 closed gate door body 60 anchor 61 hook 100 temporary closing structure 120 anchor body 130 tension part 131 tendon 132 sheath 140 anchor head 141 fixing tool 142 bearing plate

Claims (1)

It is a temporary deadline structure used when constructing a through hole in an existing dam body.
A dome body in which the opening contacts the upstream surface of the dam dam body so as to surround the planned opening position of the through hole;
An anchor placed on the bottom of the dam body upstream and connected to the dome body;
A temporary closing structure of a dam body characterized by comprising

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