JP2006328811A - Construction method of sand discharge facility using temporary drainage channel in dyke - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a construction method capable of efficiently constructing a sand discharge facility for discharging sediment in a reservoir of a dam to the downstream side at a relatively low cost.
SOLUTION: A step of removing concrete from a temporary drainage channel which is provided in a dam body as a temporary drainage channel at the time of dam construction and is filled with concrete after the dam construction, and a temporary drainage which is filled with concrete A step of forming an opening upstream of the road, a step of forming a work space around the upstream opening prior to the step of forming the upstream opening, and a discharge for passing the sediment through the tunnel from which the concrete has been removed. Forming a passage and providing a means for opening and closing the discharge passage in order to adjust the discharge flow rate of the water containing the deposit.
[Selection] Figure 1

Description

  The present invention relates to a construction method for facilities for suppressing the progress of sedimentation by discharging sand centered on low-density turbidity in a reservoir of a dam.

  In the dam, sediment and muddy water flow into the reservoir from upstream, and sediment such as mud and sediment accumulates on the bottom of the dam. The dam is designed after the capacity of such deposits is calculated in advance. However, due to factors such as unexpected changes in the natural environment, the capacity of sediments may exceed the expected level.

As an apparatus for removing such deposits from a reservoir, for example, Japanese Patent Application Laid-Open No. 10-118698 (Patent Document 1) describes an underwater working machine with a bucket wheel that can travel on the bottom of a water. In this apparatus, sediment is fluidized, taken into a sediment separator together with water, and separated according to the particle size of the earth and sand.
Japanese Patent Laid-Open No. 2001-20318 (Patent Document 2) discloses that a pump dredger provided in a reservoir has a suction pump that continuously sucks sediment from the bottom of the water and sends it to a vibrating fluid through a feed pipe. A device for feeding is described.
JP-A-10-118698 JP 2001-20318 A

The above-mentioned conventional sediment removal equipment takes the sediment into the separation equipment, removes sludge, and sorts it by the particle size of earth and sand, etc., and does not intend to discharge the sediment actively downstream. .
That is, some rivers downstream of the dam have a riverbed drop or coastal erosion near the mouth of the river, and there is concern about the impact of dams such as mud and sediment. Therefore, depending on the location, it is required to positively release the sediment downstream.

  In view of the current situation as described above, the object of the present invention is to provide a sand discharge facility that suppresses the progress of sedimentation in a reservoir at a relatively low cost by efficiently discharging a low-density turbid flow mainly flowing into the reservoir. The object is to provide a construction method that can be constructed efficiently.

In order to solve the above problems, in the present invention, the step of removing the concrete from the temporary drainage channel that is provided in the levee body as a temporary drainage channel at the time of dam construction and filled with concrete after the dam construction, The step of forming an opening on the upstream side of the temporary drainage channel filled with concrete, the step of forming a work space surrounding the upstream side opening prior to the step of forming the upstream side opening, and the concrete were removed. In an existing dam, comprising: a step of forming a discharge passage for allowing sediment to pass through the tunnel; and a step of providing means for opening and closing the discharge passage to adjust the discharge flow rate of water containing the deposit. A construction method for sand removal equipment is provided.
In the present invention, by removing the concrete of the temporary drainage channel filled with concrete after the dam construction, the tunnel is formed in the dam dam body, and the discharge passage is formed in this tunnel. Reinforcing bars at the time of constructing the temporary drainage channel are left in the inner periphery of this tunnel, so that complicated steps such as newly installing reinforcing bars can be omitted, construction time can be shortened, construction cost Can be suppressed. In addition, since the work space is formed around the upstream opening, an opening should be formed upstream of the temporary drainage tunnel filled with concrete without draining from the reservoir and lowering the water level. Therefore, construction work of the sand removal facility can be carried out while continuing to use the reservoir of the existing dam.

In the present invention, in the step of forming the work space, a cylindrical structure is formed along the dam body so as to form a cylindrical space that communicates vertically from the planned opening formation location on the upstream side of the dam body to the reservoir water surface. The water inside the cylindrical structure may be drained, and the cylindrical structure may be formed watertight so as not to be submerged from the reservoir. If a cylindrical structure that communicates vertically along the bank is provided in this way, materials and construction equipment can be carried in relatively easily by being suspended by a lifting machine installed at the top of the dam bank. be able to.
In the cylindrical structure, a box having only a bottom plate or a bottom plate and a side wall is installed at the bottom, a side wall member or a tubular body is suspended on the bottom plate or the box, and the side wall member or the tubular body is suspended. It can be constructed by repeating the lowering step and bonding. A side wall member is comprised with the board | plate material formed in semicircular arc shape or U-shape, this is attached to the side of a dam body watertight, and forms cylindrical space inside.

  In the present invention, in the step of forming the discharge passage, an opening member is provided on the upstream side of the tunnel after the concrete is removed, a plurality of pipes are carried into the tunnel, and the pipes are connected to each other. Concrete can be filled in the gap between the tube body and the opening member.

Further, in the present invention, when the use of the tunnel provided as a temporary drainage channel in the dam body for the construction of the dam is completed, the temporary drainage channel is not closed after filling the concrete with the concrete without filling the temporary drainage channel. An opening member is provided on the upstream side, a plurality of pipes are carried into the temporary drainage channel, the pipes are connected to each other, and concrete is filled in a gap between the temporary drainage channel, the plurality of pipes, and the opening member. The construction method of the sand discharge facility characterized by this is provided.
The present invention is a construction method in which a tunnel provided as a temporary drainage channel for dam construction is diverted to a sand discharge facility without being filled with concrete after use as a temporary drainage channel. Reinforcing bars at the time of temporary drainage channel construction are left in the part, and complicated processes such as newly installing reinforcing bars can be omitted, the construction period can be shortened, and construction costs can be reduced. Can do. In addition, since the construction of the sand removal facility is performed before the dam reservoir is put into service, there is no need to surround the upstream opening with a temporary deadline, which also shortens the construction period and reduces construction costs. It becomes possible.

According to the invention described in claim 1, by removing the filled concrete from the temporary drainage channel filled with concrete after the dam construction, a tunnel is formed in the dam body, and a discharge passage is formed in the tunnel. Therefore, sand removal equipment can be constructed efficiently at a relatively low cost.
In general, these temporary drainage channels are often installed at a relatively low position of the dam, and are installed at a position suitable for efficiently discharging the low-density turbidity flow. Since the inflow of low-density turbidity into the reservoir is the largest during floods, operating the sand removal facility during flood control effectively discharges sediments downstream and suppresses sedimentation in the reservoir.
In addition, these operations provide a function close to the function of a natural river where sediment from the upstream flows down in the event of a flood.

  Further, according to the invention described in claim 4, since the construction for converting the tunnel provided as a temporary drainage channel for the construction of the dam to the sand removal facility is performed before the start of the operation of the dam reservoir, the construction period is further increased. Shortening and construction cost control are possible.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited thereto.

<First embodiment>
[Outline of construction method of sand removal equipment]
The construction method of the sand removal facility according to the present invention is provided in the levee body as a temporary drainage channel when constructing an existing dam, and after the dam construction, the filled concrete is removed from the temporary drainage channel that is filled with concrete and blocked. It is characterized by the formation of a discharge passage for removing sediment and allowing the sediment to pass through it. The main steps are the installation process of the upstream temporary deadline, the removal process of the filled concrete, and the formation of the upstream opening. Including a process, a process for forming a discharge passage, a process for installing an opening / closing means for the discharge path, and the like, a process for constructing a downstream valve chamber, a process for installing a main discharge valve and a sub-discharge valve, a process for constructing a downstream water conduit, An installation process such as a sweep pipe is also performed.

[Upstream temporary deadline installation process]
As shown in FIGS. 1 (a) to 1 (c), the upstream side temporary closing line 10 surrounds the upstream opening with a temporary closing line to secure a working space, and the dam dam body 11 is provided upstream of the discharge passage. It is installed prior to the step of forming the side opening.
As shown in FIG. 1A, first, a lifting machine such as a crawler crane 12 is installed on the top of the dam dam body 11, and a guide member such as a guide rail (not shown) is suspended by the crawler crane 12. Lower and fix the guide member along the upstream side of the dam body by diving. Next, the caisson member 13 is suspended by the crawler crane 12, the caisson member 13 is poured into the reservoir 14 while being submerged, and further suspended near the upstream opening along the guide member. Secure to the side. The caisson member 13 constitutes the lowermost end portion of the provisional deadline, has a bottom plate, has no side wall at the portion contacting the side surface of the levee body, and has a side wall on the other surface. it can.
Similarly, the other caisson members 15 are suspended by the crawler crane 12 and sequentially stacked on the caisson member 13 at the lowermost end, whereby the upstream temporary cutoff 10 can be constructed. In addition, the caisson member 15 in the second and subsequent stages is a member in which a plate material is formed in an arc-shaped cross section or a U-shaped cross section, and does not have a plate material at a position that contacts the side surface of the dam dam body 11. .
After the installation of all the caisson members 13 and 15 is completed, or each time the caisson members 13 and 15 are installed, the gap between the dam dam body 11 and the side surfaces of the caisson members 13 and 15 is closed by the water stop material 16. As shown in FIG. 1B, after the caisson members 13 and 15 are completely installed, if the water inside is gradually drained while confirming the water stoppage, the installation process of the upstream temporary cutoff 10 is completed.
The lower end of the upstream temporary cutoff line 10 is slightly lower than the position where the upstream opening is to be formed, for example, about 1 m lower than the lower end of the upstream opening so as not to interfere with the formation of the upstream opening. The Further, the upper end of the upstream temporary cutoff 10 is set to a position that is about 1 m higher than the operating water level of the reservoir 14 so that the inside of the temporary cutoff does not flood even when the water surface fluctuates due to the height of wind waves.

[Removal process of filled concrete]
In the process of removing concrete from the temporary drainage channel, it is necessary not to give a harmful impact or vibration to the dam body 11. For this reason, explosives are not used, and excavation is performed using static crushing agents containing expansion materials and machines. Although not shown, the excavation method using a machine is, for example, drilling a plurality of holes in a removal target location, splitting the concrete between the holes using a hydraulic splitting device, etc., and then concrete in the depth direction of the holes. Drilling. While carrying out the crushed concrete to the work gantry 17 provided on the downstream side of the dam body 11, the above steps are repeated.
It should be noted that most of the concrete excavation work is performed from the downstream side of the dam body 11, and therefore, the concrete removal process is performed as shown in FIGS. 1 (a) to 1 (c). It is possible to carry out in parallel with the installation process of the deadline 10, and after completion of the upstream temporary deadline 10, it is also possible to carry out only penetration of the dam dam body 11 to the upstream side.

[Upstream side opening formation process]
Proceed with the concrete removal work from the downstream side of the dam body, and when the thickness of the existing concrete left on the upstream side is reduced to, for example, about 500 mm, this part is removed by digging from the upstream side of the dam body. be able to. After the upstream opening is formed in this way, the concrete is removed by widening the opening so that the diameter of the opening increases toward the upstream side. ) And a gate door contact member, and concrete is filled around the bell mouth. In this concrete filling operation, a concrete pump car is disposed at the top of the dam body, and high fluidity concrete is placed through a pipe extending from here to around the bell mouth. In addition to this, an air pipe that ejects air from the tip nozzle, a sweep pipe that ejects water from the tip nozzle, a water control gate (not shown, means for opening and closing the discharge passage), a water stop plate, etc. Install. The attachment of these members can be performed inside the upstream temporary cutoff by suspending materials and equipment in the upstream temporary cutoff by a crawler crane at the top of the dam dam body.

[Formation process of discharge passage]
As shown in FIG. 2, a steel pipe 21 as a discharge pipe is installed in a tunnel 20 formed by removing concrete from a temporary drainage channel. The installation of the discharge pipe is carried out by an entrained steel pipe method that does not require welding work from the outer periphery. The entrainment steel pipe method is a known technique, in which a steel plate is wound into a steel tube and reduced in diameter, fixed in this reduced diameter state, transported to an installation location, expanded in the installation location, and axially and circumferentially. It is a method of joining.
That is, in order to form a discharge passage, a steel mount 22 for retracting the steel pipe 21 and fixing the installation is installed in the tunnel 20 after the concrete is removed. Then, a winch 23 is installed on the downstream work gantry 17, an index rope 24 is extended from the winch 23 into the tunnel 20, is folded around a pulley 25 provided in the vicinity of the upstream opening, and is turned downstream of the tunnel 20. Extend outside. The entrained steel pipe 21 is installed on a steel mount 22 by a lifting machine 26 such as a crane, connected to an indexing rope 24 and pulled by a winch 23, and the entrained steel pipe 21 is sequentially introduced from the upstream side in the tunnel 20 to the steel mount. 22 at a predetermined position. The rolled steel pipe 21 is expanded in diameter at a predetermined position, and fixed in the pipe axis direction by welding. When the entrained steel pipe 21 is repeatedly installed on the steel mount 22, pulled, and welded in the pipe axis direction, and the circumferential joint between adjacent steel pipes 21 is fixed by welding, the discharge pipe 29 shown in FIG. 3 is formed. can do.
Next, highly fluid concrete is placed in the gap between the discharge pipe 29 and the tunnel 20. In this concrete placing work, a concrete pump car 27 is disposed on the work gantry 17, and a pipe 28 is extended from there to a predetermined position through a gap between the discharge pipe 29 and the tunnel 20, and highly fluid concrete is placed.

[Installation process of opening / closing means for discharge passage]
As a means for opening and closing the discharge passage, as shown in FIG. 4, a main gate 32 and a sub-gate 33 are installed in the downstream opening of the discharge pipe 29 in addition to the water control gate 31 provided in the shed portion.
The main gate 32 is a tensile radial gate having a structure in which water pressure is applied as a tensile load, and the muddy flow containing a large amount of earth and sand can be stably shut off with little biting of the earth and sand. Above the main gate 32 and the sub gate 33, a gate operation chamber 34 for installing devices such as an opening / closing device, a hydraulic device, and an operation panel for operating the gate is provided. Also, a downstream water conduit (not shown) is appropriately constructed on the downstream side of the tensile radial gate. The water control gate 31 provided at the mouth portion is provided with a sweeping device that forcibly flushes the sediment at the gate door by a jet jet in order to prevent opening and closing troubles due to sediment accumulation and biting. The jet jet is a mechanism for guiding water from the reservoir to the vicinity of the bottom surface of the water control gate 31 through a pipe from a centrifugal pump 36 provided in the inspection gallery 35.
The tensile radial gate is a gate whose door body is formed in an arc shape, and is provided with a rotating shaft, a bearing, and a leg so as to open and close by rotating about the center of the arc. In the tension radial gate, the rotation shaft is arranged on the upstream side of the arcuate door so that the water pressure acts as a tensile load. Also, in this embodiment, the cylinder for opening and closing the door body is arranged below the door body so that the door body opens when the opening and closing cylinder is extended, and the door body closes when the opening and closing cylinder contracts To do.

  As described above, in the construction method of the sand discharge facility according to the present invention, when an existing dam is constructed, it is provided as a temporary drainage channel in the levee body. The tunnel after the removal of concrete is left with reinforcing bars when constructing a temporary drainage channel, and a new reinforcing bar is provided. The complicated process can be omitted, and the construction period can be shortened and the construction cost can be reduced. Moreover, since the work space is formed around the upstream opening, the sand discharge facility can be constructed while using the reservoir.

[Method for removing deposits]
Next, the deposit removal method will be described with reference to FIG.
When the sediment removal operation is not performed, the water control gate 31 in the sand removal facility is closed, and the main gate 32 and the sub-gate 33 are in an open state. The sub-gate 33 is always kept open.
When starting the deposit removal operation, the main gate 32 is closed and the discharge pipe 29 between the water control gate 31 is filled with water as preparation. This is for suppressing negative pressure acting in the discharge pipe 29 when the water control gate 31 is released. When the discharge pipe 29 is sufficiently filled with water, the water control gate 31 is raised and opened, and then the main gate 32 is opened. Thereby, the sediment accumulated at the bottom of the reservoir 14 is discharged to the downstream conduit through the discharge pipe 29.
When the sediment is discharged, all of the water control gate 31, the main gate 32, and the sub-gate 33 are open. However, when the discharge of the sediment is finished, the main gate 32 is closed to reduce the water flow. stop. Next, when the water control gate 31 is lowered so that a slight gap remains and the main gate 32 is opened again, a strong water flow (flushing) is generated, and the sediment accumulated in the discharge pipe 29 can be washed away. When the earth and sand are sufficiently washed, the main gate 32 is closed to stop the flow of water, and the flushing operation is finished. At this time, the water control gate 31 has a slight gap left at the lower end, and earth and sand are collected in the door groove portion at the lower end. Remove. After cleaning the door groove, the water control gate 31 is lowered and completely closed, and then the main gate 32 is opened. At this time, if some earth and sand remain in the discharge pipe, the water control gate 31 is opened again with a little gap, and the earth and sand are washed away by a strong water flow (flushing) to return to the normal state.

<Second Embodiment>
[Outline of construction method of sand removal equipment]
In the second embodiment, the tunnel provided in the levee body as a temporary drainage channel when constructing a dam is not closed by concrete filling after the use as the temporary drainage channel is finished, and this is used as a sand discharge facility. The main method includes a process for forming an upstream opening, a process for forming a discharge passage, a process for installing a means for opening and closing the discharge passage, and a process for constructing a downstream valve chamber, The installation process of the main discharge valve and the secondary discharge valve, the construction process of the downstream conduit, and the installation process of the headpipe etc. are also carried out. In addition, illustration is abbreviate | omitted in 2nd embodiment, and it demonstrates with reference to 1st embodiment as needed.

[Upstream side opening formation process]
In a tunnel provided as a temporary drainage channel during the construction of a dam, when the use as a temporary drainage channel ends, an opening member (Bellmouth) that expands the diameter upstream to the upstream opening part of the dam body, that is, the mouth part A gate door stop member is provided, and concrete is filled around the bell mouth. This concrete filling work and other work such as air jet nozzle, air pipe, water jet nozzle, scavenging pipe, water control gate, water stop plate, and the like are performed by the same method as in the first embodiment.

  Subsequent to the above-described steps, [the discharge passage forming step] and [the discharge passage opening / closing means installation step] are performed. Since these steps are performed in the same manner as in the first embodiment, further explanation is omitted here.

It is the figure which showed roughly the installation process of the upstream temporary deadline concerning this invention. It is the figure which showed roughly the removal process of the filling concrete concerning this invention. It is the figure which showed schematically the formation process of the discharge channel concerning this invention. It is sectional drawing of the discharge passage concerning this invention.

Explanation of symbols

10 Upper Temporary Deadline 11 Dam Embankment 13 Caisson Member 14 Reservoir 15 Caisson Member 29 Discharge Pipe

Claims (4)

  At the upstream side of the temporary drainage channel filled with concrete, the process of removing concrete from the temporary drainage channel that is provided in the levee body as a temporary drainage channel at the time of dam construction and filled with concrete after the dam construction Prior to the step of forming the upstream side opening, forming a work space around the upstream side opening, and a discharge passage for allowing the sediment to pass through the tunnel from which the concrete has been removed. A method for constructing a sand discharge facility in an existing dam, comprising: a step of forming; and a step of providing means for opening and closing a discharge passage in order to adjust a discharge flow rate of water containing deposits.   In the step of forming the working space, a tubular structure is formed along the dam body in a vertical communication from an opening formation planned location on the upstream side of the dam body to the reservoir water surface, and the tubular structure body is formed from the reservoir in the interior. 2. The construction method of sand removal equipment in an existing dam according to claim 1, wherein the construction is watertight so as not to be submerged and the water is drained from the inside of the cylindrical structure.   In the step of forming the discharge passage, an opening member is provided on the upstream side of the tunnel after the concrete is removed, and a plurality of pipes are carried into the tunnel to connect the pipes to each other. 2. The construction method for sand removal equipment in an existing dam according to claim 1, wherein concrete is filled in a gap between the opening member and the opening member.   When the use of a tunnel provided as a temporary drainage channel for the construction of a dam is completed, the temporary drainage channel is opened upstream of the temporary drainage channel after or during dam construction without blocking the temporary drainage channel by filling with concrete. A member is provided, a plurality of pipes are carried into the temporary drainage channel, the pipes are connected to each other, and concrete is filled in a gap between the temporary drainage channel, the plurality of pipes, and the opening member. Construction method of sand removal equipment.

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