Settling basin

Abstract

To provide a settling basin capable of flushing sand with sand flushing water while suppressing residual sand even if the basin has a curved portion.SOLUTION: A settling basin 1 is provided in a flow path Y and has a curved section B. A wall-shaped or stripe-shaped fluid guide 10 is provided in the curved section B. The direction of the fluid guide 10 is the same as the direction of the curved section B. The height of the fluid guide 10 is lower than the set water depth during sand flushing, and preferably corresponds to 20% to 80% of the set water depth during sand flushing.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a settling basin for settling sediment that flows into a hydroelectric power plant from an intake or the like. [Background technology]

[0002] 2. Description of the Related Art A known example of a sediment discharge device for a water intake sedimentation basin for hydroelectric power generation is described in Japanese Patent Laid-Open Publication No. 4-371606 (Patent Document 1). This device is equipped with a plurality of water channels 15a to 15e formed by partition walls 14 that extend over the entire surface of the settling basin 1 along the water flow to the vicinity of the sand flushing channel 7, and a sand-floating gate 17 that stirs up the settled sand. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 4-371606 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned device, the water flow in the grit basin is completely separated by the water channels 15a-15e, so the flow velocity in each water channel 15a-15e is faster on the inside than when it is not separated by the water channels 15a-15e, and the settling of sediment is suppressed due to the reduced flow velocity. In the above-mentioned device, the dancing sand gate 17 travels along one of the water channels 15a-15e, forcibly discharging the stirred-up sediment. Therefore, the above-mentioned device requires the provision of the dancing sand gate 17, and energy and costs are required for its travel and maintenance. Furthermore, if a curved portion is provided in the grit basin due to topographical constraints, additional costs will be required in waterways 15a to 15e and dance sand gate 17 to accommodate the curved portion.

[0005] The main object of the present invention is to provide a settling basin which, even if it has a curved section, allows sand to be removed using sand-removal water while suppressing residual sand. [Means for solving the problem]

[0006] This specification discloses a settling basin. The settling basin may be provided in a flow path. The settling basin may have a curved section. A wall-shaped or strip-shaped fluid guide may be provided in the curved section. The direction of the fluid guide may be the same as the direction of the curved section. The height of the fluid guide may be lower than the set water depth during sand flushing. Effect of the Invention

[0007] The main effect of the present invention is to provide a settling basin which, even if it has a curved section, allows sand to be flushed out using sand flushing water while suppressing residual sand. [Brief description of the drawings]

[0008] [Figure 1] 1 is a perspective view of a settling basin and its surrounding area according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a top view of FIG. [Diagram 3] FIG. 3 is an enlarged view of a curved portion and its surrounding area in FIG. [Figure 4] FIG. 2 is a cross-sectional end view of the fluid-guiding portion in FIG. 1; [Diagram 5] 13 is a photograph of a curved portion and its surrounding area after sand has been flushed out in a model according to a comparative example. [Figure 6] 13 is a photograph of a curved portion and its surrounding area after sand has been flushed out in the model according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described together with modified examples with reference to the accompanying drawings. It should be noted that the embodiment is not limited to the following examples and modified examples.

[0010] Fig. 1 is a perspective view of the settling basin 1 and its surroundings according to this embodiment, and Fig. 2 is a top view of the settling basin 1 and its surroundings. The settling basin 1 is provided in a hydroelectric power plant. However, the settling basin 1 may also be provided in a place other than a hydroelectric power plant.

[0011] The grit basin 1 has a first straight section F1, a curved section B, and a second straight section F2. The bottoms of the first straight section F1, the curved section B, and the second straight section F2 are flat. However, at least any of the bottoms does not have to be flat. The settling basin 1 is provided in the flow path Y, and is arranged between the water intake channel T and the water headrace U. The settling basin 1, the water intake channel T, and the water headrace U are provided in at least one of a valley-like topography and a rock tunnel. The settling basin 1 has a curved portion B due to at least one of topographical constraints and land acquisition constraints. The settling basin 1 may have a curved portion B even if there are other constraints or no constraints.

[0012] The intake channel T passes water from a river. The intake channel T has a bulkhead BH, a plurality (two) of water channels T1 and T2, and a plurality (two) of intake channel gates GT1 and GT2. The bulkhead BH is a wall extending in the same direction as the water flow. The height of the bulkhead BH is higher than the maximum water depth in the design. Note that a plurality of bulkheads BH may be provided, or the bulkhead BH may be omitted. The water channel T1 is formed in front of the bulkhead BH. The water channel T2 is formed behind the bulkhead BH. The water channels T1 and T2 pass water from the river. The bulkhead BH may be provided in a part of the upstream side of the intake channel T. In this case, the water channels T1 and T2 join in the downstream part of the intake channel T. Also, only one water channel T1 or T2 may be provided, or three or more water channels T1 and T2 may be provided. The intake channel gate GT1 is provided in the upstream portion of the waterway T1, in front of the bulkhead BH. The intake channel gate GT1 adjusts the amount of water introduced from the river into the waterway T1. When the amount introduced is zero, the intake channel gate GT1 is closed and blocks the water from the river. The intake channel gate GT2 is provided in the upstream portion of the waterway T2, in the rear of the bulkhead BH. The intake channel gate GT2 adjusts the amount of water introduced from the river into the waterway T2. When the amount introduced is zero, the intake channel gate GT2 is closed and blocks the water from the river. By providing the intake channel gates GT1 and GT2 on both sides of the bulkhead BH, it is easier to ensure the necessary strength for the intake channel gates GT1 and GT2, and the intake channel gates GT1 and GT2 do not need to be large-scale, compared to when there is no bulkhead BH and only one intake channel gate is provided. Incidentally, only one intake channel gate GT1, GT2 may be provided, three or more may be provided, or the intake channel gates GT1, GT2 may be omitted. The most downstream portion of the intake channel T, that is, the most downstream portions of the channels T1 and T2, are connected to the first straight portion F1 of the grit basin 1.

[0013] The headrace U is connected to a water turbine of a generator. The headrace U has a step portion (not shown). The bottom of the headrace U on the downstream side of the step portion is located higher than the bottom of the headrace U on the upstream side of the step portion. The most upstream portion of the water conduit U is connected to the second straight section F2 of the grit basin 1.

[0014] An inspection path E is provided above the center of the width of the settling basin 1, the intake channel T, and the water conduit U. Inspection path E is a path that inspectors walk on, and is connected to the top surface of bulkhead BH. The top surface of bulkhead BH also serves as a connecting path to inspection path E. The inspection path E is supported by multiple pillars P. Each pillar P is cylindrical and protrudes upward from the center in the width direction at the bottom of the grit basin 1, the intake channel T, and the water headrace U. Note that some or all of the pillars P do not have to be cylindrical, and do not have to be located in the center in the width direction. When the settling basin 1, the water intake channel T and the water headrace U are installed in a valley, it is difficult to form the inspection path E at low cost on the edges because the edges are cliff-like, and when they are installed in a tunnel in bedrock, it is difficult to secure space for the inspection path E, so the inspection path E is installed above the settling basin 1, the water intake channel T and the water headrace U. As each pillar P is formed in the center in the width direction of the settling basin 1, the water intake channel T and the water headrace U, the water flow in the settling basin 1, the water intake channel T and the water headrace U is less disturbed and is smoother than with other arrangements of pillars P.

[0015] The curved section B of the settling basin 1 is located between the first straight section F1 and the second straight section F2. The second straight portion F2 is longer than the first straight portion F1. The first straight portion F1 may be longer than the second straight portion F2, may be omitted, or may be treated as a part of the intake channel T. The orientation of the grit basin 1 and its surroundings is defined as follows. That is, the direction of the second straight section F2 is the front-to-rear direction, the downstream side, i.e. the water turbine side, is the front side, and the upstream side, i.e. the curved section B side, is the rear side. Also, the up-down direction is defined according to the actual up-down direction, with the ground side being the bottom side and the air side being the top side. Furthermore, the right side when facing forward is defined as the right side, and the left side when facing forward is defined as the left side. The first straight portion F1 extends to the left and right. The curved portion B connects the most downstream portion, ie, the right end portion, of the first straight portion F1 and the most upstream portion, ie, the rear end portion, of the second straight portion F2. The first straight portion F1, the curved portion B, and the second straight portion F2 each have a gradient that decreases toward the downstream side. In other words, the first straight portion F1, the curved portion B, and the second straight portion F2 each have a gradient that decreases from the upstream side to the downstream side. Note that the gradient of at least one of the first straight portion F1, the curved portion B, and the second straight portion F2 may be omitted.

[0016] The first straight portion F1 and the curved portion B have a plurality (five) of flow guides 10. The number of flow guides 10 provided may be four or less, or six or more. 3 is a top view of the curved portion B and its surroundings, and FIG. Each of the fluid guides 10 is wall-like or striated. Each of the fluid guides 10 extends along the boundary lines and imaginary center lines of the first straight section F1 and the curved section B. The extension direction of each of the fluid guides 10 is the same as the boundary lines and imaginary center lines of the first straight section F1 and the curved section B. The portion between adjacent flow guides 10 or between the boundary between adjacent flow guides 10 and the grit basin 1 is a lane L. There are six lanes L due to the five flow guides 10. Here, the lane located on the innermost side of the curve is the first lane, the lane adjacent to this on the outer side of the curve is the second lane, and so on up to the sixth lane. The shape of part or all of the fluid guide 10 is not limited to a wall-like or striated shape. Furthermore, part or all of the fluid guide 10 does not have to be along the boundary lines on both sides and the imaginary center line of the curved section B. In addition, the part of one or more fluid guides 10 arranged in the first straight section F1 may be omitted. That is, the fluid guide 10 may be arranged only in the curved section B. Alternatively, one or more fluid guides 10 may be arranged so as to extend over a part of the curved section B. Furthermore, one or more fluid guides 10 may be arranged so as to extend over a part or all of the second straight section F2.

[0017] Each of the fluid guides 10 is provided at the bottom of the first straight portion F1 and the curved portion B. Each of the fluid guides 10 protrudes upward with respect to the adjacent portions of the first straight portion F1 and the bottom of the curved portion B. The width W and height H of each fluid guide 10 are constant. The height H of each fluid guide 10 is equal to or less than the width W. The width W of each fluid guide 10 is approximately 1 / 60 to 1 / 100 of the width of the first straight section F1 or the curved section B. The width W and height H of each fluid guide 10 may be other than those described above. For example, the width W and height H of some fluid guides 10 may be different from the width W and height H of other fluid guides 10. Furthermore, the width W and height H of one or more fluid guides 10 do not have to be constant.

[0018] The five fluid guides 10 are arranged in the width direction of the first straight section F1 or the curved section B. The distance between adjacent fluid guides 10 is constant. The distance between the inner end edge of the first straight section F1 or the curved section B, i.e., the end edge from the rear side to the right side, and the fluid guides 10 adjacent to the inner end edge, is the same as the distance between adjacent fluid guides 10. The distance between the outer end edge of the first straight section F1 or the curved section B, i.e., the end edge from the front side to the left side, and the fluid guides 10 adjacent to the outer end edge, is the same as the distance between adjacent fluid guides 10. That is, the widths of the first lane L1 to the sixth lane L6 are similar to each other. The central flow guide 10 is disposed at the center in the width direction of the first straight portion F1 or the curved portion B. The central flow guide 10 is integrated with the lower end portion of the pillar P. The arrangement of the one or more flow guides 10 is not limited to the above. For example, the widths of the first lane L1 and the sixth lane L6 may be different from the widths of the second lane L2 to the fifth lane L5. The central flow guide 10 may be considered to be divided by the lower end of the pillar P.

[0019] The inner end edge and the outer end edge of the curved portion B are concentric quadrant arc shapes. The inner end edge and the outer end edge of the curved portion B do not have to be concentric quadrant arcs. For example, the inner end edge and the outer end edge do not have to be concentric. Furthermore, the length of at least one of the inner end edge and the outer end edge may be less than the length of the quadrant arc or may exceed the length of the quadrant arc. At least one of the inner end edge and the outer end edge does not have to be arc-shaped.

[0020] The second straight portion F2 has a second straight portion main body M and a stepped-down portion Z. The second straight portion main body M is the portion upstream of the stepped-down portion Z. The step-down portion Z is a portion that is one step lower than the second straight portion main body M. The step-down portion Z is disposed at the most downstream portion, i.e., the front end portion, of the second straight portion F2. The step-down portion Z is connected to the water channel U. The bottom of the stepped-down portion Z is lower than the bottom of the second straight portion main body M. The step-down portion Z extends across the entire most downstream portion of the second straight portion F2 in the width direction, i.e., the left-right direction. Note that the step-down portion Z does not have to extend across the entire most downstream portion of the second straight portion F2 in the width direction. For example, the step-down portion Z may be located on the left side of the most downstream portion of the second straight portion F2. The step-down portion Z may be omitted.

[0021] A sand discharge return structure R is connected to the boundary of the settling basin 1 on the side of the water conduit U. That is, the sand discharge return structure R is connected to the front end of the settling basin 1. The sand discharge return structure R has a sand discharge path D and a sand discharge path gate GD. The sand flushing channel D is connected to a river. The sand flushing channel D has a sand flushing channel main body DB and a lead-out section DG. The sand flushing channel body DB has a gradient that decreases as it approaches the river. The most upstream part of the sand flushing channel body DB, i.e., the right end, is connected to the left side of the step-down section Z of the settling basin 1. The bottom of the right end of the sand flushing channel body DB is continuous with the bottom of the step-down section Z. The outlet portion DG is connected to the most downstream portion, i.e., the left end portion, of the sand discharge channel body DB. The outlet portion DG does not have a slope. The sand discharge gate GD adjusts the amount of water introduced from the settling basin 1 to the sand discharge gate D. When the amount of water introduced is 0, the sand discharge gate GD is closed and blocks the water from the settling basin 1.

[0022] During power generation, which is the normal operation of a hydroelectric power plant, water from the river is taken in through intake channel T to grit basin 1 and supplied to the generator's water turbine via headrace U. The water turns the water turbine, generating electricity. The water flow rate during power generation is designed and set to be relatively high, for example, 10 t / s (tons per second). The height of the water flow, i.e., the water depth, during power generation is relatively high depending on the flow rate, for example, 154 cm (centimeters). During power generation, at least one of the intake channel gates GT1 and GT2 is open, and the sand flushing channel gate GD is closed. Sediment contained in the water from the river sinks and accumulates at the bottom in the settling basin 1. Because the headrace channel U has a step, it is difficult to flush the sediment accumulated at the bottom, i.e., sediment, downstream beyond the step. In addition, in the vertical direction, most or all of each of the flow guides 10 is located below the downstream side of the step of the water guide U. This prevents each of the flow guides 10 from interfering with the water flow during power generation.

[0023] Sediment increases over time and may impede sedimentation and water flow, so it must be discharged from the sedimentation basin 1. Discharge of sediment, i.e., flushing, is performed at predetermined times (e.g., every few months) by passing water through the sedimentation basin 1. Note that flushing may also be performed temporarily when a landslide occurs upstream of the river, for example. During sand flushing, the opening degree of at least one of the intake channel gates GT1 and GT2 is designed and set to be narrower than that during normal times. With such an opening degree, the flow rate of river water taken into the intake channel T as sand flushing water is set to be smaller than that during normal times, for example, 1.3 t / s. The set water depth of the sand flushing water in the intake channel T, the grit basin 1, and the headrace U during sand flushing is determined according to the set flow rate during sand flushing. The set water depth during sand flushing is, for example, 20 cm. Due to the step portion of the headrace U, a relatively small flow rate of running water does not flow into the headrace U. A headrace gate may be provided at the boundary between the grit basin 1 and the headrace U and closed during sand flushing. The set flow rate during sand flushing may be set to have a plurality of steps. Furthermore, the set water depth may be different from each other in at least any two of the intake channel T, the grit basin 1, and the headrace U. During sand flushing, the sand flushing gate GD is opened. Therefore, water from the river during sand flushing, i.e., sand flushing water, flows from the intake channel T through the grit basin 1, passes through the sand flushing channel D, and returns to the river. The sand flushing water is shallower than normal water and carries with it the sediment. The sand flushing water flushes out the sediment.

[0024] Each of the flow guides 10 changes the flow of the sand flushing water compared to the case where each of the flow guides 10 is not provided. The direction of flow of the sand flushing water at the lower part is the direction of each fluid guide 10. On the other hand, the direction of the upper flow of the sand flushing water is divided into the direction of each guide fluid 10, the direction overcoming each guide fluid 10 from inside to outside, and the direction overcoming each guide fluid 10 from outside to inside. The upper flow of the sand flushing water is distributed into a flow C1 along each guide fluid 10, a flow C2 overcoming each guide fluid 10 from inside to outside, and a flow C3 overcoming each guide fluid 10 from outside to inside. In the curved section B, the flows C2 and C3 overcoming each guide fluid 10 are generated more frequently than in the first straight section F1. That is, in the curved section B, the distribution ratio of the flows C2 and C3 overcoming each guide fluid 10 to the distribution ratio of the flow C1 along each guide fluid 10 is larger than in the first straight section F1 and the second straight section F2. At the curved portion B, centrifugal force generates more flow C2 that overcomes each of the flow guides 10 from the inside to the outside than flow C3 that overcomes each of the flow guides 10 from the outside to the inside. For example, at curved section B, the flow C2 moving from the upper side of the first lane L1 to the upper side of the adjacent outer second lane L2 occurs more than the flow C3 moving from the upper side of the second lane L2 to the upper side of the first lane L1.

[0025] The height H of each guide 10 is set lower than the set water depth during sand flushing, from the viewpoint of generating a flow C1 along each guide 10 and flows C2, C3 over each guide 10. Furthermore, from the viewpoint of appropriately allocating the flow C1 along each guide 10 and the flows C2, C3 overflowing each guide 10, the height H of each guide 10 is preferably a height equivalent to 20% to 80% of the set water depth during sand flushing, more preferably a height equivalent to 40% to 70% of the set water depth during sand flushing, and even more preferably a height equivalent to 50% to 60% of the set water depth during sand flushing. If the height H of each guide 10 is too small relative to the set water depth during sand flushing, only a small amount of flow C1 along each guide 10 is generated. If the height H of each guide 10 is too large relative to the set water depth during sand flushing, only a small amount of flow C2, C3 overflowing each guide 10 is generated.

[0026] In this way, by installing each of the fluid guides 10 lower than the set water depth during sand flushing, water flows C1 to C3 are generated in multiple directions. These multiple directional flows C1 to C3 increase the amount of sediment entrained during sand flushing compared to the case of a unidirectional water flow, and the amount of sediment discharged increases, improving the sand flushing rate. The sand flushing rate corresponds to the ratio of the volume of discharged sediment to the volume of sediment in the settling basin 1 just before sand flushing, i.e., the sand flushing volume, and is expressed by the following formula (1). The unit of the sand flushing rate is %, and the sand flushing volume can also be obtained by subtracting the volume of sediment remaining in the settling basin 1 just after sand flushing is completed from the volume of sediment in the settling basin 1 just before sand flushing. Sand flushing rate = sand flushing volume / volume of soil just before sand flushing × 100 (1)

[0027] The grit basin 1 has the following effects. That is, the settling basin 1 is provided in a flow path Y and has a curved section B. A wall-shaped or strip-shaped fluid guide 10 is provided in the curved section B. The direction of the fluid guide 10 is the same as the direction of the curved section B. The height H of the fluid guide 10 is lower than the set water depth during sand flushing. Therefore, a settling basin 1 is provided in which, even if it has a curved portion B, sand can be discharged using sand discharge water at a high sand discharge rate while suppressing residual sand.

[0028] Moreover, the height H of the fluid guide 10 corresponds to 20% to 80% of the set water depth during sand flushing. Therefore, the flows C1 to C3 in multiple directions are generated more effectively, and residual sand is further suppressed. Furthermore, a plurality of flow guides 10 are provided, so that flows C1 to C3 in a plurality of directions are generated in each flow guide 10, further suppressing residual sand. Furthermore, the fluid guide 10 is integrated with the lower end of the pillar P. Therefore, the pillar P necessary for the inspection path E and the like and the fluid guide 10 effective in suppressing residual sand are integrated, and the settling basin 1 has an efficient configuration.

[0029] In addition, the curved section B has a gradient that decreases from the upstream side to the downstream side. Therefore, the gradient, together with the flow guide 10, promotes sand flushing, and further suppresses residual sand. Moreover, the settling basin 1 further has a second straight section F2. The second straight section F2 is connected to the downstream side of the curved section B. The second straight section F2 has a step-down section Z that is lower than the upstream side. Therefore, in the settling basin 1 having the curved section B and the second straight section F2, residual sand is further suppressed. Furthermore, the flow path Y is connected to a river and a water turbine of a hydroelectric power plant. Therefore, a grit basin 1 having excellent sand flushing properties is provided in the hydroelectric power plant. EXAMPLES

[0030] Next, a description will be given of a model of the present invention based on the above-mentioned embodiment, and a comparative example based on a model not belonging to the present invention. The present invention is not limited to the following examples. Depending on how the present invention is interpreted, an example may be a comparative example, and a comparative example may be an example.

[0031] A 1 / 10 scale model was created as an example of the intake channel T, the grit basin 1, the section of the water conduit U from its connection with the grit basin 1 to the step section, and the sand flushing channel D. This model was designed to fit a valley adjacent to an actual river. If construction is carried out using this model, the grit basin 1 and its adjacent sections can be installed at a lower cost than if the grit basin 1 did not have the curved section B. The dimensions of the various parts of the model are as follows. When constructing on the actual terrain according to this model, the dimensions will be 10 times larger than the following.

[0032] The difference in elevation between the boundary between the intake channel T and the first straight section F1, i.e., the most upstream part of the first straight section F1, and the boundary between the curved section B and the second straight section F2, i.e., the most downstream part of the curved section B, is 5 cm. The most downstream part of the curved section B is lower than the most upstream part of the first straight section F1. The gradient from the most upstream part of the first straight section F1 to the most downstream part of the curved section B is constant. The radius of the outer edge of curve section B is 1.2 m (meters). The height H of each flow guide 10 is 1 cm. The width W of each flow guide 10 is 1 cm.

[0033] The length of the second straight portion main body M in the front-rear direction from the most upstream portion to the most downstream portion is 4 m. The difference in elevation between the most upstream and most downstream portions of the second straight portion main body M is 10 cm. The most downstream portion of the second straight portion main body M is lower than the most upstream portion. The gradient from the most upstream portion to the most downstream portion of the second straight portion main body M is constant and is 1:40. The length of the step-down portion Z in the front-to-rear direction is 25 cm. The vertical step between the step-down portion Z and the most downstream part of the second straight portion main body M is 5 cm. The step-down portion Z is lower than the most downstream part of the second straight portion main body M. There is no gradient in the step-down portion Z.

[0034] The length of sand flushing channel D in the left-right direction is 2.05 m. The width of sand flushing channel D in the front-to-back direction is 20 cm. The left-right length of the sand discharge channel main body DB is 1.65 m. The left-right length of the outlet section DG is 40 cm. The difference in elevation between the boundary between the step-down section Z and the sand discharge channel D, i.e., the upstream-most part of the sand discharge channel main body DB, and the downstream-most part of the sand discharge channel main body DB, is 10 cm. The downstream-most part of the sand discharge channel main body DB is lower than the upstream-most part of the sand discharge channel main body DB. The gradient from the upstream-most part to the downstream-most part of the sand discharge channel main body DB is constant, at 1:17.

[0035] Also, a comparative model was created which was similar to the example model except that it did not have any of the fluid guides 10 .

[0036] Hydraulic experiments were then carried out by the experimenters using these models. In the hydraulic experiment, the experimenter first piled sand on the model. More specifically, the experimenters subjected the model to a water flow that was equivalent to the flow rate required for generating electricity, and that contained sand.

[0037] In hydraulic experiments, if the Reynolds number Re and Froude number Fr are made to match those of the actual object, the scale model can perfectly simulate the actual object. However, it is realistically difficult to make both the Reynolds number Re and Froude number Fr match those of the actual object. Usually, in experiments on rivers and waterways, the effect of gravity is stronger than that of viscosity, so Re is sufficiently large compared to Fr that the effect of Re can be almost ignored. Therefore, in experiments on rivers and waterways, Froude's law of similarity is applied, which matches Fr between the model and the actual object. In this hydraulic experiment, the experimenters also used Froude's law of similarity. In Froude's law of similarity, if the scale of the model is 1 / n, the length is 1 / n. Also, the time is 1 / n. 1 / 2 Furthermore, the flow rate is 1 / n 1 / 2 Furthermore, the flow rate is 1 / n 5 / 2 In addition, the pressure is 1 / n. Also, the Manning roughness coefficient is 1 / n 1 / 6 In this hydraulic experiment, n=10. Therefore, in order to accurately simulate the model here, the flow rate during power generation is set to 1 / 10 of 10t / s. 5 / 2 This amounts to approximately 31.6 kg / s. The diameter of the sand particles is about 1 / 10 of the actual diameter, and the volume of sand contained in the water flow equivalent to that during power generation is about 1 / 1000 of the actual volume. The experimenter let a water flow containing sand equivalent to that during power generation continue for 3.16 hours, causing sand to accumulate in the model of the embodiment and the model of the comparative example. The water depth of the water flow equivalent to that during power generation was about 22.5 cm, which corresponds to the set water depth during power generation, and in reality it was about 20 cm to 25 cm in all models. Here, the actual water depth value has a range because the water flow is choppy, and the same applies below. The average of the actual water depth values ​​during power generation was about the set water depth during power generation. In addition, the experimenter measured the volume of sand accumulation in each model after the water flow equivalent to that during power generation had finished.

[0038] Next, the experimenter applied a water flow equivalent to that required for sand flushing to each model and performed sand flushing. The flow rate during sand discharge is 1 / 10 of 1.3t / s 5 / 2 The result was approximately 4.11 kg / s. The water depth of the water flow equivalent to sand flushing, which corresponds to the set water depth during sand flushing, is approximately 3 cm, and in reality it was between 2 cm and 4 cm in all models. The actual water depth during sand flushing was averaged to be approximately the set water depth during sand flushing. Furthermore, sand is not included in the water flow equivalent to sand flushing. The water flow equivalent to sand flushing took 0.95 hours to flow in each model. Furthermore, after the water flow equivalent to sand flushing had finished flowing, the experimenters measured the volume of remaining sediment, i.e., residual sand, in each model. Figure 5 shows a photograph of the curved section and its surrounding area after sand removal in the comparative example. In this photograph, remaining white sand can be seen in curved section B and other areas. A photograph of the curved section and its surrounding area of ​​the example after sand removal is shown in Figure 6. In this photograph, a small amount of remaining white sand is visible in curved section B and other areas, with a smaller volume than in the comparative example.

[0039] The experimenters then calculated the sand flushing rate for each model. The sand flushing rate in the comparative example model was 81.8%. The sand flushing rate in the example model was 93.7%.

[0040] The comparative model discharges more sand due to the gradient in curved section B and the formation of step-down section Z than when these gradients and formations are not present. In particular, the formation of step-down section Z promotes sand discharge in the second straight section F2. However, as shown in Figure 5, even if a gradient is provided in curved section B, residual sand still remains. In contrast, the sand flushing performance of the model of the embodiment is improved, particularly in curved section B, by the installation of each fluid guide 10. This improvement in sand flushing performance is believed to be due to the multi-directional flows generated by each fluid guide 10. In the model of the embodiment, the installation of each fluid guide 10 improves the sand flushing rate by 10 points or more compared to the model of the comparative example, and an excellent sand flushing rate of over 90% is obtained. [Explanation of symbols]

[0041] 1·· Grit basin, 10·· Conducting fluid, B·· Curved section, C1·· Flow (in the same direction as the conducting fluid 10), C2·· Flow (overcoming the conducting fluid 10 from the inside to the outside), C3·· Flow (overcoming the conducting fluid 10 from the outside to the inside), F·· Second straight section (straight section), H·· Height (of the conducting fluid 10), P·· Pillar, Y·· Flow path.

Claims

1. A grit basin provided in a flow path, It has a curved section, A wall-shaped or stripe-shaped fluid guide is provided in the curved portion, The direction of the fluid guide is the same as the direction of the curved portion, The height of the guide fluid is lower than the set water depth during sand removal. A settling basin characterized by

2. The height of the guide fluid corresponds to 20% to 80% of the set water depth during sand discharge.

2. The settling basin according to claim 1 .

3. The fluid guide is provided in plurality.

2. The settling basin according to claim 1 .

4. The fluid guide is integral with the lower end of the column.

2. The settling basin according to claim 1 .

5. The curved portion has a gradient that decreases from the upstream side to the downstream side.

2. The settling basin according to claim 1 .

6. Further, it has a straight portion, The straight portion is connected to the downstream side of the curved section, It has a step-down section that is lower than the upstream side 2. The settling basin according to claim 1 .

7. The flow path is connected to a river and to a water turbine of a hydroelectric power station.

2. The settling basin according to claim 1 .

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