JP2009150091A - Sand basin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sort out the earth and sand flowing into a sand basin according to the particle sizes and materialize efficient discharge of the sand through a sand discharging pipe. <P>SOLUTION: The sand basin 1 includes a bottom structure 20 having larger depths toward the lower stream of a flow passage 4, and sand discharging pipes 7 respectively installed on predetermined different depth positions of the bottom structure 20. The sand discharging pipes 7 respectively have openings 5 having larger diameters as the positions get shallower. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sand settling basin that sinks earth and sand flowing in from a water intake of a hydroelectric power plant, and in particular, relates to a technique for classifying and efficiently discharging earth and sand accumulated at the bottom of a sand settling basin according to particle size. .

Sand and sand etc. flow into the waterway that supplies the river water to the hydroelectric power plant, so a part of the waterway is widened in the middle of the waterway to reduce the flow rate of the water and sink the sand and sand in the running water. Is provided. As a sand discharging technique for discharging the earth and sand accumulated at the bottom of the sand basin, the present inventors, for example, in Patent Document 1, a method of installing a vortex sand pipe having a slit at the bottom of the sand basin Disclosed. This is because the vortex sand pipe installed at the bottom of the sand settling basin is provided with a plurality of slits at predetermined intervals, and the sediment accumulated on the vortex sand pipe is sucked into the vortex sand pipe through the slits. It is discharged downstream. At this time, as shown in FIG. 12, the earth and sand deposited on the vortex sand discharge pipe is discharged in a mortar shape according to the angle of repose θ in water.
JP 2005-146603 A

  For example, the diameter of the opening of the sand discharge pipe installed in the sand basin is set based on the average particle size of the sediment deposited in the sand basin. However, the particle size of the earth and sand actually flowing into the sand basin varies, and if sand with a particle size larger than the setting flows into the sand basin, the opening of the sand discharge pipe that cannot suck it will be clogged. there were. On the other hand, in order to prevent the clogging of the opening, if the diameter of the opening is too large, the negative pressure acting on the opening from the inside of the sand discharging pipe is weakened, and the sand discharging range by the sand discharging pipe is narrowed. Occurs.

  Therefore, the present invention has been made in view of the above-described problems, and an object of the present invention is to classify the earth and sand flowing into the sand settling basin according to the particle size and to realize efficient sand removal using a sand discharging pipe.

  A sand basin of the present invention that solves the above problem is a sand basin provided in a flow path, and has a bottom structure with a depth increasing toward the downstream of the flow path, and has different depths in the bottom structure. It is characterized in that a sand discharge pipe having an opening having a larger diameter is installed at a predetermined location as the depth of each predetermined location is shallower.

  Further, in the sand basin, the bottom structure increases the depth stepwise toward the downstream of the flow path to form a staircase structure including a plurality of steps, and the sand discharge pipe is connected to the staircase. The structure may be configured and installed at a plurality of steps having different depths.

  Moreover, the said sand basin WHEREIN: The said bottom part structure is provided with a recessed part in the predetermined location of different depth, and it is good also as what installed the said sand removal pipe | tube in the said several recessed part from which a depth mutually differs.

  Further, in the sand basin, the bottom structure is provided with a screen provided with a plurality of slits having a larger opening width as the depth of the installation location of the sand discharge pipe is shallower on the downstream side of the sand discharge pipe. It is good also as.

  In the sand basin, the sand removal pipe may include an opening / closing material that opens and closes the opening.

  In addition, a flow velocity measuring device is installed in the flow channel, the flow velocity of the water flow flowing through the flow channel is measured, and the aperture diameter of the vortex sand pipe is enlarged or reduced according to the flow velocity value output from the flow velocity measuring device. Control may be performed. In this case, the control device in the vortex sand pipe obtains the measured value from the flow velocity measuring device, and when the obtained measured value (= flow velocity) exceeds a predetermined upper limit value, the aperture diameter is predetermined. On the other hand, when the measured value (= flow velocity) falls below a predetermined lower limit, the opening / closing material is controlled to reduce the aperture diameter by a predetermined amount.

  In addition, the flow velocity measuring device is installed at each installation location of the vortex sand removal pipe, the flow velocity around the vortex sand removal tube is measured, and the flow velocity around the vortex sand removal tube output by the flow velocity measurement device is measured. Therefore, control may be performed to enlarge or reduce the aperture diameter for each vortex sand pipe. In this case, the control device in each vortex sand pipe acquires the measurement value from the flow velocity measuring instrument connected to itself, and the measurement value (= flow velocity) acquired here exceeds the predetermined upper limit value. The opening / closing material is controlled to enlarge the opening diameter by a predetermined amount, and when the measured value (= flow velocity) falls below a predetermined lower limit, the opening diameter is reduced by a predetermined amount.

  Furthermore, the screen may be provided on the back surface of the slit (a surface on the downstream side of the slit), and may include an opening / closing material that opens and closes the slit, and a control device that controls the opening / closing operation of the opening / closing material. . In this case, similarly to the above-described caliber control of the vortex sand pipe, it can be assumed that control is performed to enlarge or reduce the aperture diameter for each screen according to the measurement value (= flow velocity) of the flow velocity measuring device (each The control device in the screen acquires the measurement value from a flow velocity measuring instrument connected to the screen, and when the acquired measurement value (= flow velocity) exceeds a predetermined upper limit value, the aperture diameter is set to a predetermined amount. On the other hand, when the measured value (= flow velocity) falls below a predetermined lower limit, the opening / closing material is controlled to reduce the aperture diameter by a predetermined amount).

  In addition, the problems disclosed by the present application and the solutions thereof will be clarified by the embodiments of the present invention and the drawings.

  According to the present invention, the earth and sand flowing into the sand settling basin are classified according to the particle diameter, and efficient sand removal by the sand discharge pipe is realized.

--- Structure of sand basin ---
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a view showing a sand basin according to this embodiment. The sand basin 1 in this embodiment is provided in the flow path 4 which guides the water flow which flows in from the intake port of a hydroelectric power station to a generator, for example. Since such a sand basin 1 expresses the effect | action which suppresses the flow velocity of the water flow which flows through the said flow path 4 suitably, and promotes sedimentation of the earth and sand 2, the earth and sand 2 will accumulate on the bottom part. In order to suppress the flow velocity of the water flow, the depth of the sand basin 1 should be deeper than that of the channel 4, so that the depth of the bottom portion is larger than the channel 4 connected to the sand basin 1.

  The sedimentation basin 1 according to this embodiment that classifies the earth and sand 2 for each particle diameter has a bottom structure 20 in which the depth increases toward the downstream side of the flow path 4. In the example of FIG. 1, the depth is increased stepwise toward the downstream side of the flow path 4, and a bottom structure 20 formed by a staircase structure 21 including a plurality of steps 22 is assumed. In the predetermined portion of the bottom structure 20 at different depths, that is, in the step 22 in the example of FIG. A vortex sand pipe is installed.

  For example, the step 22a having the shallowest depth in the staircase structure 21 has the maximum flow velocity between three steps, and the step 22b having a depth deeper than the step 22a and shallower than the downstream step 22c is between the three steps. In step 22c having the deepest depth in the staircase structure 21, the flow velocity is minimum between the three steps. This affects the particle size of the sediment 2 deposited in each step 22, and the particle size of the sediment in each step is: step 22a (minimum depth and maximum flow velocity)> step 22b (intermediate depth and intermediate flow velocity)> The relationship is step 22c (maximum depth and minimum flow velocity).

  Therefore, the relationship between the particle size of the sediment in each step is also reflected in the diameter of the opening 5 in the vortex sand pipe 7, and the diameter of the opening 5 in each step is the step 22a (minimum depth and maximum flow velocity). )> Step 22b (Intermediate depth and flow velocity intermediate)> Step 22c (Maximum depth and minimum flow velocity).

  Next, the vortex sand pipe 7 will be described. FIG. 2 is a plan view showing the overall structure of the vortex sand pipe 7 according to the present embodiment, and FIG. 3 is a view taken along the line AA ′ of FIG. Moreover, FIG. 4 is a figure which shows the pipe structure of the vortex sand removal pipe 7 which concerns on this embodiment, and FIG. 5 is a figure which shows the opening / closing material 9 which concerns on this embodiment. As shown in FIGS. 2 and 3, the vortex sand pipe 7 for discharging the sediment 2 deposited in the sand basin 1 is installed in the bottom structure 20 of the sand basin 1 and has a plurality of openings 5 through which the sand 2 flows. And an opening / closing member 9 that is slidably inserted into the vortex sand pipe 7 and that allows the opening 5 to be opened and closed. Further, a control device 11 for sliding the opening / closing member 9 against the vortex sand discharge pipe 7 is provided in a housing structure of the sand basin 1 so that the opening 5 can be opened and closed (of course, the vortex sand removal). The tube 7 may include the control device 11 integrally).

  As shown in FIG. 4, the vortex sand discharge pipe 7 is a cylindrical pipe having a plurality of openings 5 in the axial direction as a pipe structure. For example, a steel pipe is used in this embodiment. In the present embodiment, the opening 5 of the vortex sand pipe 7 is calculated by design in advance, for example, a predetermined width W: 5 cm, a predetermined length L: 20 cm, a distance between centers: a predetermined interval P (described later) The size is set such that 100 cm, which is half of the above, and a predetermined diameter D: 20 cm.

  The opening / closing material 9 is inserted into the inner space of such a tube structure. As shown in FIG. 5, the opening / closing member 9 is a cylindrical tube having a plurality of slits 10 in the axial direction. In the present embodiment, for example, a steel tube is used. In the present embodiment, the length and width of the slit 10 of the opening / closing material 9 are the same as the opening 5 of the vortex sand removal pipe 7, and the distance between the centers is, for example, a predetermined interval P of 200 cm. The predetermined length L, the predetermined width W, and the predetermined interval P of the openings 5 and 10 of the vortex sand pipe 7 and the opening / closing material 9 are the diameter of the vortex sand pipe 7 and the sand that can be discharged. It is calculated by design based on the amount, the particle size of the earth and sand 2 and the like, and is appropriately changed according to each site condition.

  The control device 11 for controlling the opening / closing material 9 of the vortex sand discharging pipe 7 has one end connected to the end of the opening / closing material 9 and slides the opening / closing material 9 in the axial direction with respect to the vortex sand discharging pipe 7. A sliding means 13 that moves and a driving means 15 that drives the sliding means 13 are provided. In the present embodiment, the sliding means 13 uses a hydraulically extendable cylinder, and the driving means 15 uses a hydraulic pump that generates an operating pressure of the cylinder. Then, the opening / closing material 9 is slid in the axial direction, and the position of the slit 10 of the opening / closing material 9 and the position of the opening 5 of the vortex sand removal pipe 7 are matched to each other. 2 is allowed to flow into the vortex sand pipe 7 and discharged.

---- Other structural examples ---
As the structure of the sand basin 1, the following can be assumed in addition to the above-described form. FIG. 6 is a view showing another structural example 1 of the sand basin. Here, for example, it is assumed that the bottom structure 20 of the sand basin 1 forms an inclined structure 30 in which the depth gradually increases toward the downstream of the flow path 4. At this time, the sand basin 1 is provided with recesses 23 at predetermined locations at different depths in the inclined structure 30. The concave portion 23 serves to retain and deposit the earth and sand 2 flowing down on the inclined structure 30 while being inclined. The sediment 2 deposited here is discharged by installing the vortex sand pipe 7 in the corresponding recess 23. Therefore, each recess 23 is provided with a vortex sand removal pipe 7.

  As still another structural example, a sand basin 1 in which a screen 26 is installed on the downstream side of the vortex sand pipe 7 can be assumed. FIG. 7 is a view showing another structural example 2 of the sand basin. In this case, the bottom structure 20 of the sand basin 1 is provided with a screen 26a at the rear edge 21d of the step 22a on the downstream side of the vortex sand pipe 7. The screen 26a keeps the movement of the sediment 2 flowing down along the slope of the bottom structure 20 from the upstream by the slit 25a for the particle size that settles according to the flow velocity in the step 22a. Therefore, the opening width 24a of the slit 25a is the maximum between steps corresponding to the flow velocity (the fastest between steps 22a to 22c) according to the depth of the step 22a.

  On the other hand, among the earth and sand 2 having a particle diameter that has passed through the slit 25a of the screen 26a, the particle diameter that settles according to the flow velocity at the downstream step 22b is set up on the rear edge of the step 22b. The slit 25b is used. Therefore, the opening width 24b of the slit 25b is intermediate between steps corresponding to the flow velocity according to the depth of the step 22b (intermediate between steps 22a to 22c).

  Similarly, among the earth and sand 2 having a particle size that has passed through the slit 25b of the screen 26b, the particle size that settles in accordance with the flow velocity at the downstream step 22c is erected on the trailing edge of the step 22c. It is fastened by a slit 25c of the screen 26c. Therefore, the opening width 24c of the slit 25c is the minimum between steps corresponding to the flow velocity (minimum between steps 22a to 22c) according to the depth of the step 22c.

  The screen 26 is disposed on the rear surface of the slit (the surface on the downstream side of the slit), and an opening / closing member 28 for opening and closing the slit 25, and the opening / closing member 29 in the lateral direction (in the drawing). And a controller 29 that controls the opening / closing operation of the slit by sliding in the direction of the arrow). At this time, the opening / closing material 28 has the same opening as the slit 25, and the opening of the slit 25 can be appropriately narrowed by its own non-opening portion by sliding the back surface of the slit. Further, the control device 29 is provided at the upper end of the screen 26 and has a rail on its bottom surface for allowing the slide to slide while gripping the upper end of the opening / closing material 28. For example, a pulley or a ball bearing is provided on the inner surface of the rail, and an appropriate protruding piece at the upper end of the opening / closing material is gripped while being bitten by the pulley or the ball bearing. The control device 29 is also provided with a drive device such as a motor for driving the pulley and the ball bearing.

  By installing such a screen 26 on the bottom structure 20, classification at a predetermined location (step 22 or recess 23) for each depth is performed more efficiently.

---- Sand removal treatment ---
Next, a sand discharging method using the vortex sand discharging pipe 7 in the sand basin 1 described above will be described. FIG. 8 is a diagram illustrating Example 1 of the sand removal method according to the present embodiment. For example, a case will be described in which, in a predetermined step 22 in the sand basin 1 having an extension of 10 m, a width of 2 m, and a water depth of 2 m, the sediment 2 having a thickness of 30 cm is deposited and the average particle size of the sediment is 1 mm. .

First, the effective vortex tube length is calculated by the following formula.
From the continuity formula:
dQ / dx = q (Formula 1)
From the equation of motion,
β / gA2 · dQ2 / dx + d (p / w + z) / dx−U / gA · dQ / dx + fQ2 / 2gDA2 = 0 (Formula 2)

Here, Q: flow rate in the vortex tube (m3 / s), q: inflow per unit length flowing into the vortex tube (m2 / s), U: cross-sectional average flow velocity (m / s) in the vortex tube, A : Cross-sectional area of vortex tube (m2), x: Downstream distance (m) along vortex sand pipe 7 axis, g: Gravitational acceleration (m2 / s), P: Pressure at center of tube (Pa), w : Unit volume weight of fluid (kg / m3), z: height of tube center axis from reference plane (m), D: tube diameter (m), f: coefficient of friction.

  The effective vortex tube length in this embodiment calculated from Equation 1 and Equation 2 is 8.2 m, and the slit is 9 for each of the vortex sand discharge tube 7 and the opening / closing material 9 based on the predetermined length L and the predetermined interval P. And 5 each.

Next, the control device 11 is operated to slide the opening / closing member 9 in the axial direction, so that the position of the slit 10 of the opening / closing member 9 and the position of the opening 5a of the vortex sand pipe 7 are matched. At this time, all the openings 5b adjacent to the opened opening 5a are closed. Then, the earth and sand 2 above the opening 5 a is discharged into the vortex sand discharge pipe 7. By this first sand removal, approximately 0.25 m ^{3 of} sand and sand 2 in a mortar-like range with the angle of repose θ underwater of 30 ° to 40 ° facing upward is removed.

  FIG. 9 is a diagram illustrating Example 2 of the sand removal method according to the present embodiment. As shown in FIG. 9, the control device 11 is operated again to slide the opening / closing material 9 in the axial direction (right direction in the drawing), and the position of the slit 10 of the opening / closing material 9 and the first sand removal described above are performed. The position of the opening 5b adjacent to the position of the opening 5a of the vortex sand pipe 7 that has been opened is made coincident. At this time, all the openings 5a of the vortex sand pipe 7 opened at the time of the first sand removal are closed. And the earth and sand 2 etc. above the opening 5b opened this time are discharged into the vortex sand pipe 7. As in the first time, sand removal in the mortar-shaped range with an angle of repose θ underwater of 30 ° to 40 °, etc. 2 is removed by the second sand removal, and sand removal is performed in the first and second times. The total amount is about 0.5 m3. In these two times of sand removal, most of the earth and sand 2 accumulated above the vortex sand pipe 7 flows into the vortex sand pipe 7 through the openings 5 and 10 and is discharged.

  Thus, according to this embodiment, the earth and sand flowing into the sand settling basin are classified according to the particle diameter, and efficient sand removal by the sand discharge pipe is realized.

  As mentioned above, although embodiment of this invention was described concretely based on the embodiment, it is not limited to this and can be variously changed in the range which does not deviate from the summary.

It is a figure which shows the sand basin which concerns on this embodiment. It is a top view which shows the whole structure of the eddy sand pipe which concerns on this embodiment. It is an AA 'arrow line view of FIG. It is a figure which shows the pipe structure of the vortex sand removal pipe concerning this embodiment. It is a figure which shows the opening / closing material which concerns on this embodiment. It is a figure which shows the other structural example 1 of a sand basin. It is a figure which shows the other structural example 2 of a sand basin. It is a figure which shows Example 1 of the sand removal method which concerns on this embodiment. It is a figure which shows Example 2 of the sand removal method which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sedimentation basin 2 Sediment etc. 3 Eddy sand removal apparatus 4 Flow path 5 Opening (of vortex sand removal pipe) 7 Eddy sand removal pipe 9 Opening and closing material 10 Opening material (of opening and closing material) 11 Control device 13 Sliding means 15 Driving means 20 Bottom Structure 21 Step structure 22 Step 23 Recess 24 Opening width 25 (slit) Slit 26 Screen 30 Inclined structure W Predetermined width L Predetermined length P Predetermined distance D Predetermined diameter

Claims (5)

A sand basin provided in the flow path,
Having a bottom structure with an increased depth toward the downstream of the flow path;
A sand basin characterized in that a sand discharge pipe having an opening having a larger diameter is installed at a predetermined location at a different depth in the bottom structure as the depth of each predetermined location is shallower. The bottom structure increases the depth stepwise toward the downstream of the flow path, and forms a step structure composed of a plurality of steps.
2. The sand basin according to claim 1, wherein the sand discharge pipe is installed in a plurality of steps that form the staircase structure and have different depths. The bottom structure is provided with a recess at a predetermined location at a different depth,
The sand settling basin according to claim 1 or 2, wherein the sand discharge pipe is installed in the plurality of concave portions having different depths.   The bottom structure is characterized in that, on the downstream side of the sand removal pipe, a screen having a plurality of slits having a large opening width is erected as the depth of the installation location of the sand removal pipe is shallower. The sand basin according to any one of claims 1 to 3.   The sand basin according to any one of claims 1 to 4, wherein the sand discharge pipe includes an opening / closing material that opens and closes the opening.

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