JP2017036623A - Rice field dam system - Google Patents

Abstract

CONSTITUTION: A rice field dam system 10 is the connecting type rice field dam system for regulating a drainage volume from multiple paddies 100 in a mass, and includes multiple individual drain pipes 20 provided in each paddy, a collective drain pipe 22 for connecting each drain pipe with a public drainage 104, and a drainage volume adjusting unit 24 provided in the collective drain pipe. Also, a backflow prevention unit 50 having a float valve body (54) is provided in at least the individual drain pipe included in a paddy of a low paddy height.EFFECT: A rice field dam system can prevent damage from concentrating on a paddy of a low paddy height, even if applied to a paddy area including multiple paddies with different paddy heights.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rice field dam system, and is applied to, for example, a paddy field including a plurality of paddy fields with different surface heights, and prevents flood damage by suppressing the amount of drainage from the paddy field to a public drainage channel when there is a lot of rainfall. It relates to the rice field dam system.

  In recent years, it is said to be a “rice field dam” that prevents flood damage such as river flooding by temporarily storing rainwater that has fallen on paddy fields and draining it gradually into public drainage channels over time. The system is spreading mainly in Niigata Prefecture. In the rice field dam, in general, each of the drainage outlets of the drainage basins provided in each paddy field is individually installed with a falling water amount adjustment plate (orifice plate) with a hole smaller in diameter than the drainage port. The amount of drainage into the drainage channel is suppressed.

  For example, Patent Document 1 discloses an example of a conventional individual type rice field dam. In the technique of Patent Document 1, a vertical plate-shaped water storage amount adjusting plate is used as the falling water amount adjusting plate. This water storage amount adjustment plate is formed so that the upper end height is substantially the same as the water storage water level adapted to the growing state of rice, and a drainage amount adjustment hole is drilled in the lower part.

  In the individual type rice field dam as described above, if the falling water amount adjusting plate is left installed in the drainage basin, there is a risk of hindering normal drainage. For this reason, the falling water amount adjusting plate is generally installed only when there is a lot of rainfall, and is not installed during other normal drainage. However, it takes time and effort to individually attach and detach the falling water amount adjusting plate in each paddy field according to the rainfall.

  Therefore, a connected-type rice field dam system has been proposed as a next-generation type rice field dam. In this rice field dam system, a plurality of paddy fields are defined as one paddy field, and the amount of drainage from the plurality of paddy fields included in the paddy field is collectively regulated.

  Specifically, as shown in FIG. 19, in the connected type rice field dam system 1, a collective drain pipe 4 is provided so as to straddle a plurality of paddy fields 2, and each individual drain pipe 5 provided in each paddy field 2 is provided. The drainage pipe 4 is connected. A drainage amount adjusting unit (adjusting gate) 6 is provided at the downstream end of the collective drainage pipe 4. And when there is much rain, by operating the drainage amount adjustment part 6, the drainage amount from the collective drainage pipe 4 to the public drainage channel 7 is suppressed or drainage is stopped. As a result, the drainage from the paddy field 3 where the rice field dam system 1 is installed is prevented from flowing into the public drainage channel 7 at a time. According to such a connected type rice field dam system 1, it is only necessary to operate the drainage amount adjusting unit 6 provided for each paddy field area 3, so that the work load required for adjusting the drainage amount can be reduced.

JP2012-120510A

  In the connection type rice field dam system, individual drainage pipes provided in each paddy field are connected by a collective drainage pipe. For this reason, when it is applied to a paddy field including multiple paddy fields with different field heights, if the amount of rainfall is greater than the amount of drainage from the collective drainage pipe, There is a risk that damage such as the breakage of the shore will flow into the lower paddy field (backward paddy field) and concentrate on the lower paddy field. For this reason, in the conventional connected-type rice field dam system, maintenance work is performed in advance so as to equalize the surface height of each paddy field so that rainwater is substantially evenly stored in each paddy field. However, since such maintenance work is costly, a rice field dam system that can be directly applied to a paddy field area including a plurality of paddy fields with different surface heights is desired.

  Therefore, the main object of the present invention is to provide a new rice field dam system.

  Another object of the present invention is that even when applied to a paddy field area including a plurality of paddy fields with different paddy field heights, rainwater is substantially evenly stored in each paddy field, and damage is concentrated on paddy fields having a low paddy field height. It is to provide a rice field dam system that can be prevented.

  A first invention is a rice field dam system that is applied to a paddy field area including a plurality of paddy fields having different surface heights and prevents the occurrence of flood damage by suppressing the amount of drainage from the paddy field area to a public drainage channel. A plurality of individual drain pipes provided in each of the rice fields, a collective drain pipe provided so as to straddle the plurality of paddy fields, and connecting a downstream end of the plurality of individual drain pipes and a public drainage channel, downstream of the collective drain pipe It is a rice field dam system provided with the amount adjustment part of drainage provided in a side edge part, and the backflow prevention part provided with respect to the individual drainage pipe with which at least the paddy field whose field height is low is provided.

  In the first invention, the rice field dam system is a connected type rice field dam system including a plurality of individual drain pipes and collective drain pipes, and is applied to a paddy field area including a plurality of paddy fields having different surface heights. And when there is a lot of rainfall, the amount of drainage from a plurality of paddy fields included in the paddy field area is regulated by using a drainage amount adjustment unit provided at the downstream end of the collective drainage pipe. Prevent water damage. In this 1st invention, a backflow prevention part is provided with respect to the individual drainpipe with which the paddy field (paddy field of a low rank part) with a low paddy field height is provided at least.

  According to the first invention, since the backflow prevention unit is provided for the individual drainage pipes of the lower paddy fields, even if the amount of rainfall is greater than the drainage amount from the collective drainage pipes, Thus, the drainage is prevented from flowing back, and rainwater is stored approximately evenly in each paddy field. Therefore, even if it is applied to a paddy field including a plurality of paddy fields with different field heights, it is possible to prevent damage from being concentrated on the lower paddy fields.

  The second invention is dependent on the first invention, and the backflow prevention unit is provided in the valve box connected to the individual drain pipe, in the valve box, and floats up and down according to the water level in the valve box. And a valve seat provided at the upper end of the valve body and having a water passage opening and closing by a float valve body.

  In 2nd invention, a backflow prevention part is provided with the valve box connected to a separate drainage pipe. A float valve body that moves up and down according to the water level in the valve box is accommodated in the valve box. Moreover, the valve seat which has a water flow opening is provided in the upper end part of a valve box. And if the water level in a valve box rises, the reverse flow of the waste_water | drain to a paddy field will be prevented by closing the water flow opening of a valve seat with a float valve body.

  According to the second invention, it is possible to appropriately prevent the backflow of the drainage into the paddy field without requiring power.

  A third invention is dependent on the first or second invention, and the backflow prevention unit is provided in each of the plurality of individual drain pipes.

  In 3rd invention, the backflow prevention part is provided with respect to all the individual drainage pipes also including the individual drainage pipe with which the paddy field with a high paddy field is provided in each of a several separate drainage pipe. If the water level in the public drainage channel is higher than the surface height of each paddy field, backflow of drainage from the public drainage channel to each paddy field can be considered, but for each individual drainage pipe provided in each paddy field By providing the backflow prevention unit, backflow of drainage from the public drainage channel to each paddy field is prevented.

  According to the third aspect of the invention, even when there is a backflow of drainage from the public drainage channel, the rainwater is substantially evenly distributed to each paddy field without causing inequality between the lower paddy field and the higher paddy field. Since it is stored, the paddy field area as a whole is less susceptible to flood damage.

  A fourth invention is a rice field dam system that is applied to a paddy field area including a plurality of paddy fields having different surface heights and prevents the occurrence of flood damage by suppressing the amount of drainage from the paddy field area to a public drainage channel. Multiple drainage pipes provided in each of the paddy fields, and a plurality of collective drainage pipes connecting each of the downstream ends of the individual drainage pipes provided in the paddy fields having the same or substantially the same surface height to the public drainage channel The rice field dam system includes a drainage amount adjusting unit provided at the downstream end of the plurality of collecting drainage pipes and a backflow prevention unit provided at each of the plurality of individual drainage pipes.

  In 4th invention, a rice field dam system is a connection type rice field dam system provided with a several separate drainage pipe and a collective drainage pipe, Comprising: It applies to the paddy field area containing the several rice field from which field height differs. And when there is a lot of rainfall, the amount of drainage from a plurality of paddy fields included in the paddy field area is regulated by using a drainage amount adjustment unit provided at the downstream end of the collective drainage pipe. Prevent water damage. In this 4th invention, a plurality of collective drainage pipes are provided, and each collective drainage pipe is connected to each of the downstream end portions of the individual drainage pipes provided in the paddy field having the same or substantially the same surface height, and a public drainage channel. And connect. Each of the plurality of individual drain pipes is provided with a backflow prevention unit.

  According to the fourth aspect of the present invention, the downstream end portions of the individual drainage pipes provided in the paddy field having a plurality of collective drainage pipes and having the same or substantially the same surface height are connected to each other. The rainwater is stored almost evenly in each paddy field. Therefore, even if it is applied to a paddy field including a plurality of paddy fields with different field heights, it is possible to prevent damage from being concentrated on the lower paddy fields.

  In addition, since a backflow prevention unit is provided for each individual drainage pipe provided in each paddy field, even if the water level of the public drainage channel is higher than the surface height of each paddy field, drainage from the public drainage channel to each paddy field is possible. Back flow is prevented.

  According to the present invention, since the backflow prevention unit is provided for the individual drainage pipes of the lower paddy fields, even if the amount of rainfall is larger than the drainage amount from the collective drainage pipe, the drainage is performed for the lower paddy fields. Is prevented from flowing back, and rainwater is stored approximately evenly in each paddy field. Therefore, even if it is applied to a paddy field including a plurality of paddy fields with different field heights, it is possible to prevent damage from being concentrated on the lower paddy fields.

  The above object, other objects, features, and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

It is an illustration figure which shows the rice field dam system which is one Example of this invention. 1 is a schematic cross-sectional view showing the rice field dam system of FIG. 1 and shows a state where the rice field dam system is viewed from the downstream side in the axial direction of the collective drainage pipe. It is a schematic sectional drawing which shows the rice field dam system of FIG. 1, Comprising: The state which looked at the rice field dam system from the side of the collective drainage pipe is shown. It is an illustration figure which shows the drainage amount adjustment part with which the rice field dam system of FIG. 1 is equipped, Comprising: (A) shows the state at the time of fully opening of a drainage amount adjustment part, (B) shows the state at the time of drainage amount suppression of a drainage amount adjustment part, (C) shows a state when the drainage amount adjusting unit is fully closed. It is sectional drawing which shows the backflow prevention part with which the rice field dam system of FIG. 1 is provided. It is an illustration figure which shows the base part of the backflow prevention part of FIG. It is an illustration figure which shows a mode when there is much rainfall of the rice field dam system of FIG. It is an illustration figure which shows the state which the backflow prevention part of FIG. 5 has closed the water flow opening. It is sectional drawing which shows the backflow prevention part with which the rice field dam system which is another Example of this invention is provided. It is sectional drawing which shows the cross section in the XX line of FIG. It is an illustration figure which shows the backflow prevention part with which the rice field dam system which is further another Example of this invention is equipped, Comprising: (A) is sectional drawing of a backflow prevention part, (B) is the float valve with which a backflow prevention part is provided. It is a perspective view of a body. It is an illustration figure which shows the state which the backflow prevention part of FIG. 11 has closed the water flow opening. It is sectional drawing which shows the backflow prevention part with which the rice field dam system which is further another Example of this invention is provided. It is an illustration figure which shows the state which the backflow prevention part of FIG. 13 has closed the water flow opening. It is sectional drawing which shows the backflow prevention part with which the rice field dam system which is further another Example of this invention is provided. It is an illustration figure which shows the state which the backflow prevention part of FIG. 15 has closed the water flow opening. It is a schematic sectional drawing which shows the rice field dam system which is further another Example of this invention, Comprising: The state which looked at the rice field dam system from the side of the collective drainage pipe is shown. It is an illustration figure which shows the amount of drainage adjustment part with which the rice field dam system of Drawing 17 is equipped, (A) shows the state at the time of full open of the amount of drainage adjustment part, (B) shows the state at the time of drainage amount control of the amount of drainage adjustment part, (C) shows a state when the drainage amount adjusting unit is fully closed. It is an illustration figure which shows the conventional connection type rice field dam system.

  With reference to FIGS. 1-3, the rice field dam system 10 which is one Example of this invention suppresses the amount of drainage from the paddy field 100 to the public drainage channel 104 at the time of heavy rainfall (during heavy rain), That is, it is a system that prevents rain damage such as river flooding by temporarily storing rainwater falling on the paddy field 100 and draining it gradually into the public drainage channel 104 over time.

  The rice field dam system 10 of this embodiment is a connected type rice field dam system including a plurality of individual drain pipes 20 and collective drain pipes 22 and is applied to a paddy field area 102 including a plurality of paddy fields 100 having different surface heights. Thus, the amount of drainage from the plurality of paddy fields 100 included in the paddy field area 102 is collectively regulated. Although depending on the size of one paddy field (cultivated area), the rice field dam system 10 is applied with about 5 to 10 paddy fields 100 as one paddy field area 102. However, for simplification, FIG. 1 shows two paddy fields 100 as one paddy field 102, and FIG. 3 shows four paddy fields 100 as one paddy field 102.

  Hereinafter, the structure of the rice field dam system 10 is demonstrated concretely. As shown in FIG. 1 to FIG. 3, the rice field dam system 10 includes a plurality of individual drain pipes 20 connected to each drainage basin 106 provided in each paddy field 100.

  The drainage basin 106 is also called a water outlet, and is made of synthetic resin or concrete. A conventionally well-known drainage basin 106 is appropriately used. For example, the drainage basin 106 is formed in a rectangular tube shape with a bottom, and is provided on the side surface of the shore 108 on the paddy field 100 side. A wall (front wall) on the paddy field 100 side of the drainage basin 106 is a dam plate 110 that is slidable in the vertical direction. By moving the dam plate 110 up and down, the surface water level is adjusted to a desired set water level. It is possible. Further, the bottom wall of the drainage basin 106 is disposed at the same height position as the rice field or at a height position one step lower, and the drainage port 112 is formed in the bottom wall. The upstream end of the individual drain pipe 20 is connected to the drain port 112.

  The individual drain pipe 20 includes a vertical pipe section 20a extending downward from the drain port 112 and an inclined pipe section 20b inclined at a predetermined downward slope, and appropriately connects a pipe made of a synthetic resin such as hard vinyl chloride, a joint, or the like. It is formed by doing. The inner diameter of the individual drain pipe 20 is, for example, 150 mm. Each of the downstream end portions of the individual drain pipe 5 is connected to the collective drain pipe 22.

  The collective drainage pipe 22 is embedded so as to straddle the plurality of paddy fields 100, and connects the downstream end portions of the plurality of individual drainage pipes 20 to the public drainage channel 104. That is, the drainage discharged from each paddy field 100 to each individual drain pipe 20 is discharged to the public drainage channel 104 through the collective drain pipe 22. The collective drain pipe 22 is formed by appropriately connecting pipes and joints made of synthetic resin such as hard vinyl chloride. The inner diameter of the collective drain pipe 22 is, for example, 600 mm.

  A drainage amount adjusting unit 24 is provided at the downstream end of the collective drainage pipe 22. As shown in FIG. 4, the drainage amount adjustment unit 24 is a sluice for adjusting the amount of drainage discharged from the collective drainage pipe 22 to the public drainage channel 104. The drainage amount adjusting unit 24 includes a rectangular plate-shaped partition member (gate) 28 that moves up and down by operating the handle 26, and a small hole 30 penetrating in the thickness direction is formed at the lower end of the partition member 28. The The diameter of the small hole 30 is, for example, 90 mm.

  In this embodiment, the amount of drainage is adjusted in three stages shown in FIG. 4 by moving the partition member 28 up and down. That is, the partition member 28 is arranged at the uppermost position so that the collective drainage pipe 22 is fully opened (see FIG. 4A), and the small holes 30 of the partition member 28 are located at the bottom of the collective drainage pipe 22. The partition member 28 is disposed in the drainage amount restrained state (see FIG. 4B) in which the drainage amount is restrained to the small hole 30 minutes, and the partition member 28 is disposed in the lowest position, and the collective drainage pipe 22 is closed. The amount of drainage is adjusted in three stages in the fully closed state (see FIG. 4C).

  When such a rice field dam system 10 is applied to a paddy area 102 including a plurality of paddy fields 100 having different surface heights, when the amount of rain is greater than the amount of drainage from the collective drainage pipe 22 when the amount of drainage is suppressed, In some cases, the drainage discharged from each paddy field 100 to the collective drainage pipe 22 flows back into each paddy field 100 through the individual drainage pipe 20. In particular, since the drainage easily flows back to the paddy field 100 having a low paddy field height (low paddy field), the paddy field 100 having a low paddy field height (paddy field having a high paddy field) is compared with the damage occurring in the paddy field 100 having a high paddy field height. There is a risk that damage will concentrate on the paddy field 100 in the area.

  Therefore, in the rice field dam system 10 of this embodiment, the backflow prevention unit 50 is provided (incorporated) for each of the individual drainage pipes 20 to prevent the backflow of drainage to each paddy field 100. In this embodiment, the backflow prevention part 50 is provided at the upstream end of the vertical pipe part 20 a of the individual drainage pipe 20, that is, at the drainage port 112 of the drainage basin 106.

  As shown in FIG. 5, the backflow prevention unit (backflow prevention device) 50 includes a valve box 52 formed in a vertical tubular shape. The valve box 52 is formed of a synthetic resin such as hard vinyl chloride, and is connected to the individual drain pipe 20 to constitute a part of the individual drain pipe 20. Specifically, the valve box 52 includes a substantially cylindrical box main body 52a and a tapered portion 52b that is formed at the lower end of the box main body 52a and decreases in diameter downward. The inner diameter of the box main body 52a is set larger than the inner diameter of the individual drain pipe 20, and is 225 mm, for example. Further, a short cylindrical pipe connecting part 52c is formed at the lower end of the tapered part 52b so as to extend downward, and an annular flange part 52d is formed at the upper end of the box body 52a so as to expand outward. The The pipe connection part 52c is used for connection with the vertical pipe part 20a of the individual drain pipe 20, and the flange part 52d is used for attaching a valve seat 56 described later.

  A float valve body 54 that moves up and down according to the water level in the valve box 52 is accommodated in the box body 52 a of the valve box 52. At this time, the cross-sectional area of the water passage around the float valve element 54 is set to be larger than the cross-sectional area of a water passage 56a described later. The float valve body 54 is formed into a hollow spherical shape with synthetic resin, rubber, metal, or the like. However, the float valve element 54 may be solid as long as it has a specific gravity that can move up and down according to the water level.

  Further, a valve seat 56 having a water flow port 56 a is provided at the upper end portion of the valve box 52. The valve seat 56 is formed in a circular plate shape using synthetic resin or the like, and is detachably fixed to the flange portion 52d of the valve box 52 using bolts or the like. A circular water inlet 56 a is formed at the center of the valve seat 56. The diameter of the water flow port 56a is set to be the same as or slightly smaller than the inner diameter of the individual drain pipe 20, and is, for example, 125 mm. The water passage 56a is opened and closed by a float valve element 54 as will be described later.

  Furthermore, a pedestal 58 is provided at the lower end of the valve box 52 for holding the float valve element 54 with a gap between the valve box 52 and the inner surface during normal drainage. As can be clearly understood from FIG. 6, the pedestal 58 is formed in a tripod base shape having a ring-shaped holding portion 58a and three leg portions 58b extending obliquely downward from the holding portion 58a. The pedestal 58 is formed of a synthetic resin or the like, and is fixedly attached to the upper surface of the tapered portion 52b of the valve box 52 using an adhesive or the like. In addition, the shape of the base 58, for example, the number of the leg parts 58b, etc. can be changed suitably.

  In such a rice field dam system 10, as shown in FIG. 4 (A), the drainage amount adjusting unit 24 is fully opened during normal drainage except when there is a lot of rainfall. And when the water more than the setting water level prescribed | regulated by the weir board 110 of the drainage basin 106 is supplied to the paddy field 100, the surplus water (drainage) is discharged | emitted from the drain outlet 112 to the separate drain pipe 20, and is collected. It is discharged to the public drainage channel 104 through the drainage pipe 22. At this time, as shown in FIG. 5, the float valve body 54 of the backflow prevention unit 50 is placed on the holding unit 58 a of the pedestal 58 by its own weight, and the water flow port 56 a of the valve seat 56 is opened. And since a clearance (water passage) is formed between the float valve body 54 and the inner surface of the valve box 52 by the legs 58b of the pedestal 58, the waste water flowing into the valve box 52 of the backflow prevention unit 50 is The inside of the valve box 52 smoothly flows down.

  On the other hand, when there is a lot of rain (during heavy rain) or when there is a possibility that the amount of rainfall will increase, the manager of the rice field dam system 10 or the like sets the drainage amount adjustment unit 24 to a drainage amount suppression state as shown in FIG. The That is, by draining rainwater that has fallen on the paddy field 100 into the public drainage channel 104 little by little, flood damage such as flooding of rivers is prevented.

  When the amount of rain falling in the paddy field 102 is larger than the amount of drainage from the collective drainage pipe 22 (the small hole 30 of the drainage amount adjusting unit 24) to the public drainage channel 104 in this drainage amount suppression state, as shown in FIGS. Furthermore, the water level in the collective drain pipe 22 increases, and the wastewater that cannot be stored in the collective drain pipe 22 flows back through the individual drain pipe 20. Then, when the drainage flowing back in the individual drain pipe 20 reaches the backflow prevention unit 50 and the water level in the valve box 52 rises, the float valve body 54 rises according to the water level, and the water flow port 56a of the valve seat 56 opens. It is closed by the float valve body 54. Thereby, the backflow of the waste_water | drain from the separate drain pipe 20 to the paddy field 100 is prevented. In particular, by preventing the backflow of drainage to the lower paddy field 100 by the backflow prevention unit 50, it is possible to prevent damage from being concentrated on the lower paddy field 100.

  In addition, in the state where the backflow prevention unit 50 prevents the backflow of drainage, drainage from the paddy field 100 to the individual drainage pipe 20 is stopped at the same time, and rainwater that has fallen on the paddy field 100 is stored in the paddy field 100 as it is. The Further, when the water level in the valve box 52 is lowered by draining into the public drainage channel 104, the float valve body 54 is lowered according to the water level, and the water flow port 56a of the valve seat 56 is opened. Thereby, drainage from the paddy field 100 to the individual drain pipe 20 is resumed.

  In addition, when drainage to the public drainage channel 104 in the state where the drainage amount is suppressed as shown in FIG. 4B is judged to be dangerous, it is necessary to stop draining from the drainage amount suppression state to the public drainage channel 104. When it occurs, as shown in FIG. 4C, the drainage amount adjustment unit 24 is fully closed by an administrator of the rice field dam system 10 or the like. Even in this fully closed state, when the drainage flows backward through the individual drainage pipe 20, the backflow prevention unit 50 prevents the drainage from flowing into the paddy field 100.

  According to this embodiment, for each individual drain pipe 20 provided in each paddy field 100, the backflow prevention unit 50 including the float valve body 54 that closes the water flow port 56a when the water level rises is provided. For this reason, even when the amount of rain is greater than the amount of drainage from the collective drainage pipe 22 to the public drainage channel 104, the drainage is prevented from flowing back to the lower paddy fields 100, and Rainwater is stored almost evenly.

  Therefore, the rice field dam system 10 of this embodiment can be applied as it is to the paddy field area 102 including a plurality of paddy fields 100 having different surface heights without performing maintenance work to equalize the surface height. In addition, even when applied to the paddy field 102 including a plurality of paddy fields 100 having different surface heights, it is possible to prevent damage such as the shoreline from breaking down from concentrating on the paddy field 100 in the lower part.

  Further, if the water level of the public drainage channel 104 becomes higher than the paddy field 100 surface height, the drainage may flow back from the public drainage channel 104 to each paddy field 100. By providing the backflow prevention unit 50 for each of the drain pipes 20, that is, for all the individual drain pipes 20, backflow of drainage from the public drainage channel 104 to each paddy field 100 is also prevented. Therefore, even when there is a backflow of drainage from the public drainage channel 104, rainwater is stored approximately evenly in each paddy field 100 without causing inequality between the lower paddy field 100 and the higher paddy field 100. The paddy field 102 as a whole is less susceptible to flood damage.

  Furthermore, since the mechanism for opening and closing the water flow port 56a using the float valve element 54 is used as the backflow prevention unit 50, it is possible to appropriately prevent the backflow of drainage to the paddy field 100 without requiring power.

  In the above-described embodiment, the float valve body 54 of the backflow prevention unit 50 is formed in a spherical shape and the pedestal 58 is provided at the lower end of the valve box 52. However, the shape of the valve box 52 and the float valve body 54, etc. The configuration of the backflow prevention unit 50 including can be changed as appropriate. Hereinafter, a specific example will be described.

  For example, in the embodiment shown in FIG. 9, a plurality of recesses 52 h that are recessed inward are provided at the lower end of the side wall of the box body 52 a of the valve box 52 so as to be arranged in the circumferential direction. That is, as can be clearly understood from FIG. 10, the lower end portion of the side wall of the box body 52a is formed in a wave shape (flower-shaped cross section) in which unevenness is repeated in the circumferential direction. And the float valve body 54 is hold | maintained in the state which has a clearance gap between the inner surface of the box main body 52a by the recessed part 52h of the box main body 52a. In FIG. 10, six recesses 52h are shown, but the number of recesses 52h is arbitrary. Further, the cross-sectional area of the water passage around the float valve element 54 is set to be larger than the cross-sectional area of the water inlet 56a.

  It is assumed that the wastewater discharged from the paddy field 100 includes floating substances such as straw. However, as in the embodiment shown in FIG. By doing so, it is possible to prevent malfunction of the backflow prevention unit 50 due to clogging of dust.

  Further, for example, in another embodiment shown in FIG. 11, the float valve body 54 of the backflow prevention unit 50 has a conical valve body 54a and a plurality (three in this embodiment) extending obliquely downward from the valve body 54a. ) Leg portion 54b. The valve body 54a may be a hollow body or a solid body as long as buoyancy is appropriately exerted. Further, a meat stealing portion may be formed on the bottom side of the valve main body 54a, and an air pocket may be generated there.

  In the embodiment shown in FIG. 11, during normal drainage, the float valve body 54 of the backflow prevention unit 50 is placed on the tapered portion 52b of the valve box 52 by its own weight, and the water flow port 56a of the valve seat 56 is opened. The And the waste_water | drain which flowed in into the valve box 52 of the backflow prevention part 50 from the paddy field 100 flows down the inside of the valve box 52 smoothly through the clearance gap (water flow path) formed by the leg part 54b.

  On the other hand, when the water level in the valve box 52 rises, for example, when the amount of drainage is suppressed, the float valve body 54 rises according to the water level as shown in FIG. The valve body 54a is closed. Thereby, the backflow of the waste_water | drain from the separate drain pipe 20 to the paddy field 100 is prevented.

  Further, for example, in another embodiment shown in FIG. 13, the float valve body 54 of the backflow prevention unit 50 is formed in a short cylindrical shape (disc shape). The float valve body 54 may be a hollow body, a solid body, or a meat stealing portion formed on the bottom side as long as buoyancy is appropriately exerted. The valve box 52 includes a substantially cylindrical box body 52e. On the side wall of the box body 52e, a branch pipe portion 52f that is also used as a connection portion with the upstream end portion of the individual drain pipe 20 is provided. Furthermore, an annular plate-shaped bottom 52g is provided at the lower end of the box body 52e. As a result, a valve body housing portion for housing the float valve body 54 during normal drainage is formed at the lower end of the box body 52e. Further, a small-diameter drain pipe 60 is connected to the bottom 52g, and a downstream end of the drain pipe 60 is connected to the individual drain pipe 20. And the valve seat 56 which has the water flow port 56a is provided in the upper end of the box main body 52e of the valve box 52. As shown in FIG.

  In the embodiment shown in FIG. 13, during normal drainage, the float valve body 54 of the backflow prevention unit 50 is housed in the valve body housing part of the box body 52e formed below the branch pipe part 52f by its own weight. The water inlet 56a of the valve seat 56 is opened. And the waste_water | drain which flowed in into the valve box 52 of the backflow prevention part 50 from the paddy field 100 is discharged | emitted by the separate drain pipe 20 through the branch pipe part 52f. In addition, the waste water that has entered the valve body housing portion is discharged to the individual drain pipe 20 through the drain pipe 60.

  On the other hand, when the water level in the valve box 52 rises when the amount of drainage is suppressed, the float valve body 54 rises according to the water level as shown in FIG. 14, and the water flow port 56a of the valve seat 56 becomes the float valve body 54. Closed by. Thereby, the backflow of the waste_water | drain from the separate drain pipe 20 to the paddy field 100 is prevented.

  Furthermore, for example, in another embodiment shown in FIG. 15, the float valve body 54 of the backflow prevention unit 50 includes a disk-shaped valve body 54 c. A buoyancy body 54d for increasing the buoyancy of the valve body 54c is provided on the lower surface of the valve body 54c. The buoyancy body 54d is formed of, for example, a foam. An elastic layer 54e such as a rubber plate is provided on the upper surface of the valve body 54c to improve water tightness. Further, a hinge portion 54f is provided on the peripheral portion of the valve body 54c. The valve main body 54c is attached to the valve seat 56 via the hinge portion 54f, and is rotatable in the vertical direction with the hinge portion 54f as a fulcrum.

  In the embodiment shown in FIG. 15, during normal drainage, the float valve body 54 of the backflow prevention unit 50 hangs downward due to its own weight, and the water flow port 56 a of the valve seat 56 is opened. And the waste_water | drain which flowed in into the valve case 52 of the backflow prevention part 50 from the paddy field 100 passes through the inside of the valve case 52, and is discharged | emitted as it is to the separate drainage pipe 20 as it is.

  On the other hand, when the water level in the valve box 52 rises, for example, when the amount of drainage is suppressed, the float valve body 54 rises with the hinge portion 54f as a fulcrum according to the water level, as shown in FIG. 56 a is closed by the valve body 54 c of the float valve body 54. Thereby, the backflow of the waste_water | drain from the separate drain pipe 20 to the paddy field 100 is prevented.

  In each of the above-described embodiments, the backflow prevention unit 50 is provided for all the individual drain pipes 20, but the backflow prevention unit 50 is not necessarily provided for all the individual drain pipes 20. Alternatively, it may be provided only for the individual drain pipe 20 provided in the lower paddy field 100. For example, only for the individual drainage pipe 20 provided in the paddy field 100 having the lowest surface height, or for other individual drainage pipes 20 excluding the individual drainage pipe 20 provided in the paddy field 100 having the highest field height, Or the backflow prevention part 50 can also be provided with respect to the arbitrary several individual drain pipes 20 in the meantime. Thus, by providing the backflow prevention unit 50 for at least the individual drainage pipes 20 included in the lower paddy field 100, the drainage is prevented from flowing back to the lower paddy field 100. Since rainwater is stored substantially evenly with respect to 100, damage can be prevented from concentrating on the paddy field 100 in the lower part.

  Further, in each of the above-described embodiments, only one collective drainage pipe 22 is provided in one paddy field area 102. However, as in the embodiment shown in FIG. It can also be provided.

  As shown in FIG. 17, the system 10 of this embodiment includes a plurality of individual drainage pipes 20 connected to each drainage basin 106 provided in each paddy field 100. Further, a backflow prevention unit 50 is provided at the upstream end of each individual drain pipe 20.

  In this embodiment, two collective drain pipes 22 are provided. Each collective drainage pipe 22 connects each of the downstream ends of the individual drainage pipes 20 provided in the paddy field 100 having the same or substantially the same surface height and the public drainage channel 104. That is, the piping system is divided between the lower paddy field 100 and the higher paddy field 100, and each individual drain pipe 20 provided in the lower paddy field 100 is connected by the collective drain pipe 22 for the lower section. Each of the individual drain pipes 20 provided in the high-level paddy field 100 is connected by a collective drain pipe 22 for the high-level section. The inner diameter of the collective drain pipe 22 is, for example, 300 mm. As described above, by selecting and connecting the individual drain pipes 20 provided in the paddy fields 100 having the same or substantially the same surface height, no pressure difference is generated between the paddy fields 100, and rainwater is generated for each paddy field 100. Are stored substantially evenly.

  In this embodiment, two collective drain pipes 22 are provided, but three or more collective drain pipes 22 are provided, and the piping system is divided into three or more according to the height of the paddy field 100. Is also possible.

  Moreover, the downstream end part of each collective drainage pipe 22 is piped in the vicinity position, and the drainage amount adjustment part 24 is provided there. As shown in FIG. 18, the drainage amount adjustment unit 24 of this embodiment includes a rectangular plate-shaped partition member 28 that moves up and down by operating a handle 26, and the partition member 28 penetrates in the thickness direction 2. Two small holes 30 are formed. The diameter of each small hole 30 is 45 mm, for example.

  In this embodiment, the amount of drainage from the two collective drainage pipes 22 is adjusted to three stages simultaneously by moving the partition member 28 up and down. That is, the partition member 28 is disposed at the uppermost position, and the two collective drainage pipes 22 are fully opened (see FIG. 18A). The partition member 28 is disposed so as to be positioned at the position where the drainage amount from the two collective drainage pipes 22 is suppressed to 30 minutes for each small hole (see FIG. 18B), and the partition member 28 is at the maximum. The amount of drainage is adjusted in three stages in the fully closed state (see FIG. 18C), which is disposed in the lower position and in which each collecting drainage pipe 22 is closed. However, it is also possible to individually provide the drainage amount adjusting unit 24 for the downstream end of each collective drainage pipe 22 and individually adjust the drainage amounts from the two collective drainage pipes 22.

  According to the embodiment shown in FIG. 17, the downstream end portions of the individual drainage pipes 20 provided in the paddy field 100 having a plurality of collecting drainage pipes 22 and having the same or substantially the same surface height are connected to each other. There is no pressure difference between the paddy fields 100, and rainwater is stored in each paddy field 100 substantially evenly. Therefore, even if it applies to the paddy field area 102 including a plurality of paddy fields 100 having different surface heights, it is possible to prevent damage from being concentrated on the paddy field 100 in the lower part.

  Moreover, since the backflow prevention part 50 was provided with respect to each of the individual drainage pipes 20 with which each paddy field 100 is provided, even if the water level of the public drainage channel 104 becomes higher than the field height of each paddy field 100, public drainage Backflow of drainage from the path 104 to each paddy field 100 is prevented.

  In each of the above-described embodiments, the backflow prevention unit 50 is provided at the upstream end of the individual drainage pipe 20 (that is, the drainage port 112 of the paddy field 100). It can also be provided in the middle.

  Further, in each of the above-described embodiments, the backflow prevention unit (backflow prevention device) 50 opens and closes the water flow port 56a using the vertical movement of the float valve body 54, but the mechanism of the backflow prevention unit is It is not limited to the mechanism using such a float valve body 54. For example, the backflow prevention unit may be an electric valve that opens and closes a gate valve and the like electrically. In this case, a water level sensor may be provided in the individual drain pipe 20, and the gate valve may be opened and closed depending on whether or not the water level in the individual drain pipe 20 is equal to or higher than the set water level. The water level sensor can also be provided on the surface, and the gate valve can be opened and closed depending on whether the water level of the surface water is equal to or higher than the set water level.

  Moreover, it can also be set as the remote monitoring system which transmits the detection information of a water level sensor to a centralized management system, and opens and closes a motor operated valve by remote operation based on the detection information. In the case of a remote monitoring system, the drainage amount adjusting unit 24 can also be remotely operated as an electric valve.

  It should be noted that the specific numerical values such as the dimensions mentioned above are merely examples, and can be appropriately changed according to the needs of product specifications and the like.

DESCRIPTION OF SYMBOLS 10 ... Rice field dam system 20 ... Individual drainage pipe 22 ... Collective drainage pipe 24 ... Drainage amount adjustment part 50 ... Backflow prevention part 52 ... Valve box 54 ... Float valve body 56 ... Valve seat 100 ... Paddy field 102 ... Paddy field area 104 ... Public drainage channel 106… drainage 112… drainage

Claims (4)

A rice field dam system that is applied to a paddy field including a plurality of paddy fields with different surface heights and prevents the occurrence of flood damage by suppressing the amount of drainage from the paddy field to a public drainage channel,
A plurality of individual drain pipes provided in each of the plurality of paddy fields,
A collective drainage pipe that is provided so as to straddle the plurality of paddy fields and connects the downstream end of the plurality of individual drainage pipes and the public drainage channel;
A rice field dam system comprising: a drainage amount adjustment unit provided at a downstream end of the collective drainage pipe; and a backflow prevention unit provided for the individual drainage pipe provided in at least the paddy field having a low paddy surface height. The backflow prevention unit is
A valve box connected to the individual drain pipe,
A float valve body that is provided in the valve box and moves up and down in accordance with a water level in the valve box; and a valve seat that is provided at an upper end portion of the valve box and has a water passage opening and closing by the float valve body. The rice field dam system according to claim 1 provided.   The rice field dam system according to claim 1 or 2, wherein the backflow prevention unit is provided in each of the plurality of individual drain pipes. A rice field dam system that is applied to a paddy field including a plurality of paddy fields with different surface heights and prevents the occurrence of flood damage by suppressing the amount of drainage from the paddy field to a public drainage channel,
A plurality of individual drain pipes provided in each of the plurality of paddy fields,
A plurality of collective drainage pipes connecting each of the downstream end portions of the individual drainage pipes provided in a paddy field having the same or substantially the same surface height and the public drainage channel,
A rice field dam system comprising: a drainage amount adjusting unit provided at a downstream end of each of the plurality of collective drainage pipes; and a backflow prevention unit provided at each of the plurality of individual drainage pipes.

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