Controlled yield-point flashboard

Abstract

A controlled yield-point flashboard (1) for a hydraulic structure, comprising: a trough (2) having a frontal surface comprising a bottom edge (12), the trough (2) being able to be arranged on the sill (30) of a spillway of the hydraulic structure in a nominal position such that the bottom edge (12) is in contact with the sill (30), the trough (2) being able to pivot under the action of external forces (F, G) about an axis (Z) defined by at least one abutment (32) arranged on the sill (30), up to an angle (α) smaller than a critical tilting angle, the angle (α) causing the bottom edge (12) of the frontal surface to be raised above the sill (30); and a seal (16) mounted on the frontal surface, the seal (16) being movable in translation relative to the frontal surface in order to guarantee sealing between the bottom edge (12) and the sill (30) of the spillway of the hydraulic structure not only when the trough (2) is in the nominal position but also when the trough is pivoted by the angle (α) smaller than the critical tilting angle.

Description

Increased fuse technical field

[0001] This disclosure relates to hydraulic structures, such as dams, dikes, and river weirs. Specifically, this disclosure concerns fusible weirs, devices that retract in the event of an exceptional flood. Previous technique

[0002] Document FR 2 656 354 B1 introduces the concept of a fusible weir. This passive device comprises a module placed on the sill of a hydraulic structure's spillway, forming a barrier that raises the dam's spillway crest. During most floods, water flows over the fusible weirs, which act as a free-spilling sill. Each module consists of three parts: the trough, the pressure chamber, and the feed shaft. A seal ensures the system's watertightness, and drains clear the chamber in case of accidental filling. Stops located downstream of the module keep the fusible weir in place on the spillway. In the event of an exceptional flood, i.e., when the water level exceeds a predetermined critical height, the chamber of a weir is filled with water. Pressure builds up beneath the weir, creating a destabilizing moment that causes it to tip downstream.As the water rises, the fusible risers switch over one after the other, each configured to switch over at a different critical height.

[0003] The reliability of such a device depends in part on supplying the chamber when the water level reaches the wellhead. To prevent obstruction of the supply to the chamber, document EP 2 215 308 B1 describes the concept of a protected well. This particular design proposes supplying the pressure chamber via a baffle that is invisible from the outside.

[0004] As long as the water level remains below the wellhead, the fusible risers are susceptible to reversible rotation around the axis formed by the stops, a rotation caused by an additional force. Such rotation generates water leaks downstream of the fusible risers, and the partial pressurization of the chamber reduces the module's stability margin. Although this apparent unreliability of the safety system is temporary—since the riser returns to its position when the additional force exerted by external elements ceases—it is undesirable. When the additional force disappears, the fusible riser returns to its nominal position. Since the water leakage rate can be significant, this is generally unacceptable.

[0005] Therefore, there is a need to eliminate this leakage flow and the partial pressurization of the chamber caused by the rotation of the fusible riser for the loading case described above. Summary

[0006] This disclosure addresses that situation.

[0007] A fusible weir for hydraulic structures is thus proposed, comprising a trough having a front surface including a lower edge, the trough being able to be placed on the sill of a spillway of the hydraulic structure in a nominal position such that the lower edge is in contact with the sill, the trough being able to pivot under the action of external forces around an axis defined by at least one stop placed on the sill, up to an angle strictly less than a critical tilting angle, an angle causing the lower edge of the front surface to rise away from the sill;and a sealing gasket mounted on the front surface, the sealing gasket being movable in translation relative to the front surface to ensure a seal between the lower edge and the sill of the weir of the hydraulic structure not only when the trough is in the nominal position but also when the trough is pivoted from the lower angle to the critical tilting angle.;

[0008] The inventors of this document have established that the expansion of ice that can form on the surface of the water in a hydraulic structure can create an additional force (added to the water pressure) on the fusible link. This additional force can be sufficient to cause the link to rotate by a few degrees, resulting in water leaks downstream and / or from the reservoir to the pressure chamber. The movable seal ensures the fusible link remains watertight even when in an inclined position. To a lesser extent, other forces, such as seismic forces, can cause the fusible link to rotate. The movable seal also ensures watertightness under this type of load.

[0009] The term "spillway riser" refers to an element that can have various shapes or sizes and that obstructs the flow of water. The riser is designed to be placed, without fixing, on the sill of a hydraulic structure's spillway. Once installed, the riser assumes a position, referred to in this document as the nominal position. This is a stable, equilibrium position as long as the water level remains below a critical height. The presence of the riser allows for raising the permissible water level (and therefore the capacity) of the hydraulic structure. The riser is considered a fusible element because it acts as a safety feature in the event of a flood. To this end, a mechanism allows the riser to be tilted if the water level exceeds the critical height, which can correspond to a 100-year or 1,000-year flood. At such a water level, the fusible riser deviates from its nominal position and tilts off the spillway sill.The rise disappears in the floodwater flow downstream of the spillway.

[0010] The term "trough" refers to the solid, main component of the weir. The trough comprises a frontal surface, which faces upstream and is in contact with the water. The frontal surface has a lower edge, generally straight, which rests on the weir crest in the weir's nominal position.

[0011] One or more stops are generally provided downstream of the trough. These stops are fixed to the sill and extend beyond the sill to prevent the trough from sliding on the sill.

[0012] Under normal conditions, the trough is subjected to three forces: its own weight, water pressure, and the resistance of the sill and abutment. As mentioned above, additional forces (ice, earthquakes, etc.) can disrupt this equilibrium. The trough can then pivot and find another Equilibrium position. In this intermediate inclined position, the lid is in contact with the stop(s), but the lower edge of the front surface is raised. In this temporary equilibrium position, four forces act on the lid: its own weight, the water pressure, the resistance of the sill and the stop, and the additional force. Due to the continued contact between the lid and the stops, the lid moves from the nominal position to the intermediate inclined position by rotating around an axis defined by the stops (for example, by an upper edge of the stops).

[0013] This intermediate inclined position is reversible: when the additional force ceases, the riser returns to its nominal position.

[0014] The angle of rotation of the riser in the intermediate inclined position is less than the critical angle, which is the angle that triggers the tipping and obliteration of the riser in the event of an exceptional flood.

[0015] The features described in the following paragraphs may optionally be implemented independently of each other or in combination with each other.

[0016] A rail that can extend parallel to the lower edge is fixed to the trough, and the joint is movable under the action of an elastic element interposed between the rail and the joint.

[0017] The joint can be fixed to a slide, which itself moves in translation within the rail under the action of the elastic element.

[0018] At least one sealing lip can be placed between the slide and the rail.

[0019] The joint can move in translation under its own weight.

[0020] The trough may include a lateral surface provided with a lower edge, the riser comprising a second seal movable in translation or rotation relative to the lateral surface.

[0021] The joint can have a length between 50 cm and 30 m and / or a translational stroke between 5 cm and 5 m.

[0022] The critical angle has c can be between 10° and 20°. The design of the riser (dimensions, mass distribution, geometry of the pressurization chamber, etc.) determines the critical tilt angle. The lower angle α varies continuously depending on the forces acting on the riser, while remaining strictly below the critical angle α c The seal's translational stroke is consistent with these angular variations. In other words, the seal's stroke is such that a watertight seal is guaranteed for any inclination strictly less than the critical tilt angle of the riser.

[0023] The rise may further include hydraulic communication means configured to supply a trough pressure chamber with water when the water level of the hydraulic structure exceeds a critical water height, the pressure chamber being configured to, once filled with water, exert sufficient negative pressure to trigger the tipping and / or lifting of the trough, thereby removing the trough from the weir sill of the hydraulic structure.

[0024] This disclosure also relates to a method of using a fusible riser as described previously, the method comprising a step of rotating the fusible riser and a subsequent step of translating the sealing gasket.

[0025] By "subsequent," we mean that the rotation of the trough triggers, potentially with a slight delay, the translation of the seal. The two steps may be simultaneous or may at least overlap in time. The seal may translate as soon as the trough rotation begins, and / or the translation of the seal may cease when the trough reaches its intermediate equilibrium position. Brief description of the drawings

[0026] Other features, details, and advantages will become apparent upon reading the detailed description below and analyzing the attached drawings, on which:

[0027] [Fig. 1] shows an isometric view of a fusible riser.

[0028] [Fig. 2] illustrates the process of reversing the rise in the event of an exceptional flood.

[0029] [Fig. 3] represents a rotation of a known rise under the action of an external force.

[0030] [Fig. 4] represents a rotation of a rise according to the present disclosure under the action of an external force.

[0031] [Fig. 5] shows a detailed view of a movable joint design. Description of the implementation methods

[0032] The figures schematically depict the invention. Some dimensions may be exaggerated for clarity. Upstream and downstream refer to the direction of water flow.

[0033] Figure 1 shows an isometric view of a fusible riser 1. The riser 1 comprises a trough 2. The trough 2 is a solid element, for example made of concrete, possibly reinforced. In the example shown, the trough 2 has a base 2.1, a bottom wall 2.2, and two side walls 2.3, 2.4.

[0034] The side walls 2.3, 2.4 can stand vertically and perpendicular to the base 2.1. The downstream wall 2.2 can be inclined, rising as it moves downstream, and can form an angle of approximately 120° with the base. The trough 2 can naturally take other forms.

[0035] A frontal surface 4 is formed by the base 2.1 and the lateral walls 2.3, 2.4. The water that accumulates in the hydraulic structure comes into contact with this surface 4 and enters a space 6 delimited by the lateral walls 2.3, 2.4 and by the downstream wall 2.2. If the water level increases, the water can overflow above the top surface 8 of the trough 2.

[0036] The trough 2 is placed on the sill 30 of a weir in a hydraulic structure. The sill 30 can be substantially flat and horizontal. Several troughs 2 are arranged contiguously to cover the entire width of the weir. The lateral surface 10 of the side wall 2.4 can thus come into contact with a neighboring trough (not shown). In addition to the fusible weirs, which are passive devices, the weir can be equipped with mechanized gates.

[0037] The frontal surface 4 has a lower edge 12 which is in contact with the weir sill 30. The lateral surface 10 has a lower edge 14 also in contact with the weir sill 30.

[0038] A seal 16 is fixed to the front surface 4 in a lower part, i.e. in the vicinity of the lower edge 12. A second seal (not shown) can be disposed at the lower edge 14 of the lateral surface 10.

[0039] The length of the lower edge 12, and therefore that of the joint 16, can be between 50 centimeters and 30 meters. The trough 2 can be several meters high.

[0040] Figures 2A to 2C illustrate the general operating principle of a fusible riser 1 using a cross-sectional view.

[0041] In Figure 2A, the riser 1 is in its nominal position, that is, the position it initially assumes and maintains stably under normal conditions (no additional force or exceptional flooding). The trough 2 includes a pressurization chamber 18. The chamber 18 is connected to a well 20 via fluidic communication means 22. The assembly is represented simply with a parallelepiped chamber and straight conduits acting as fluidic communication means, but in reality, it can be more complex. The well 20 is open at its top to allow water to enter when the water level corresponds to a critical height Hc above the sill 30.

[0042] Under normal conditions, the water is retained at least in part by the downstream wall 2.2 of the trough 2. The water can flow downstream without unbalancing the trough 2, when the water level is greater than the height of the downstream wall 2.2, without however exceeding the critical height Hc.

[0043] To prevent trough 2 from sliding on threshold 30 under the action of water, one or more stops 32 may be provided in contact with the base of trough 2.

[0044] Figure 2B shows an exceptional situation, namely a flood that causes the water level to rise above the critical height Hc. Under these conditions, water enters well 20 and feeds the pressure chamber 18. A drain can prevent the unintentional accumulation of water in chamber 18. However, when the flow rate of water entering chamber 18 is significant (in the case of a flood, it is much greater than the drain's discharge capacity), chamber 18 fills and exerts pressure (also called negative pressure by hydraulic engineers) on trough 2.

[0045] As shown in Figure 2C, the shape of trough 2 is such that the pressure exerted by chamber 18 initiates the tilting of trough 2. Trout 2 is shown in an inclined position at a critical angle α c In Figure 2C, the angle beyond which trough 2 tips over and lifts off the sill to allow the water to drain. The critical angle has cDepending on the geometry and mass distribution of trough 2, it can be between 10° and 20°.

[0046] The spillway can be equipped with several troughs 2 which have respective critical heights Hc, which leads the troughs to tip successively, thus smoothing the effects of the flood downstream of the hydraulic structure.

[0047] Figure 3A illustrates a trough 2 of the prior art in its nominal position. Figure 3B shows that external elements, here ice G which can form on the water surface, can apply a force F to the trough 2. The expansion of the ice tends to rotate the trough 2 around an axis Z perpendicular to the figure and supported by the stop 32, by an angle denoted α. This angle is less than the critical angle α cof figure 2C, which would cause trough 2 to tip. Therefore, trough 2 does not tip under the action of ice G but adopts a (temporary) equilibrium position, inclined relative to its nominal position. In this position, downstream water leaks are possible, with water rushing under the lower edge of the front surface and, in particular, under the seal 20, which is fixed to the trough in existing trough geometries.

[0048] Figure 4A illustrates a trough 2 of this disclosure in its nominal position. Figure 4B shows the trough under ice stress and illustrates that the seal 20 is movable in translation parallel to the front surface, downwards. The movement of the seal 20 compensates for the rotation of the trough 2 to ensure a seal and prevent water leakage downstream. The stroke of the seal, that is, the distance between the highest and lowest positions of the seal, can range from 5 centimeters to 5 meters.

[0049] Figure 5 shows an example of the design of the mechanism allowing the mobility of the sealing gasket 16 in a cross-section.

[0050] The seal 16 can be made of an EPDM (ethylene-propylene-diene monomer) type elastomer. Its profile can generally be rectangular. It may have a lower lip oriented upstream, that is to say away from the front surface 4.

[0051] The seal 16 can be a single piece or can be made up of several seal sections carefully positioned in contact with each other.

[0052] A rail 24 can be fixed to the front surface 4 of the trough 2. The rail 24 extends parallel to the lower edge 12. The rail 24 may have a U-shaped cross-section, open at the bottom. Elastic means 26 can be interposed between the rail 24 and the seal 16 to force the seal downwards as soon as the trough 2 pivots out of its nominal position. When the trough 2 returns to its nominal position, the contact between the seal 16 and the threshold 30 pushes the seal 16 upwards.

[0053] In the illustrated example, a metal slide 17 clamps an upper part of the joint 16. The slide 17 extends parallel to the rail 24. The presence of the slide 17 allows the elastic means 26 to avoid applying force directly to the joint 16.

[0054] The elastic means 26 can be of a suitable nature and stiffness to ensure the downward vertical translation of the seal 16 during rotation of the trough (see Figures 4A and 4B). The elastic means 26 can, for example, consist of helical springs, Belleville washers, spring steel strips, or elastomeric materials.

[0055] Water can enter the gap 19 between the rail 24 and the slide 17. It is therefore advantageous to provide a sealing lip 28 to prevent water leaks downstream.

[0056] The rail may optionally be drilled with holes to facilitate the circulation of water in and out of the gap 19 (or at least to balance water pressures), so as not to impede the movement of the joint.

[0057] This mechanism allows the seal to be deployed downwards passively and reliably during the rotation of the trough.

[0058] In an alternative not shown, the joint is mobile under its own weight. To this end, the joint can be appropriately ballasted, depending on the water level (and therefore the Archimedes' pressure) of the hydraulic structure.

[0059] In an unillustrated variant, the deployment of the joint is achieved by mechanized means, upon detection of a rotation of trough 2 by a geometric sensor such as an inclinometer.

[0060] The kinematics of the joint's deployment can be more or less complex. In the illustrated example, the joint undergoes a simple translation. Other kinematics are possible, such as a rotation around the lower edge 12.

[0061] An identical type of joint can be placed at the lower edge 14 of the lateral surface 6. This second joint can be movable in translation or possibly in rotation, for example around the Z axis. It can thus deploy in rotation in the opposite direction to the rotation of the trough 2. The second joint can have a length between 50 cm and 30 m and / or a translational stroke between 5 cm and 5 m and / or a rotational stroke between 1° and 15°.

Claims

Demands

1. Fuse riser (1) for a hydraulic structure comprising: a trough (2) having a frontal surface (4) including a lower edge (12), the trough (2) being able to be disposed on the sill (30) of a spillway of the hydraulic structure in a nominal position such that the lower edge (12) is in contact with the sill (30), the trough (2) being able to pivot under the action of external forces (F) about an axis (Z) defined by at least one stop (32) disposed on the sill (30), up to an angle (a) strictly less than a critical angle (a c) of tipping, angle (a) causing the lower edge (12) of the front surface (4) to rise away from the sill (30); and a sealing gasket (16) mounted on the front surface (4), the sealing gasket (16) being movable in translation relative to the front surface (4) to ensure a seal between the lower edge (12) and the sill (30) of the spillway of the hydraulic structure not only when the trough (2) is in the nominal position but also when the trough is pivoted by the angle (a) less than the critical angle (cic) of tipping.

2. Fuse riser (1) according to claim 1, wherein a rail (24) extending parallel to the lower edge (12) is fixed to the trough (2), and wherein the joint (16) is movable under the action of an elastic element (26) interposed between the rail (24) and the joint (16).

3. Fuse riser (1) according to the preceding claim, wherein the seal (16) is fixed to a slide (17), itself movable in translation in the rail (24) under the action of the elastic element (26).

4. Fuse riser (1) according to the preceding claim, wherein at least one sealing lip (28) is disposed between the slide (17) and the rail (24).

5. Fuse riser (1) according to claim 1, wherein the joint (16) is movable in translation under its own weight.

6. Fusible riser (1) according to any one of claims 1 to 5, wherein the trough (2) comprises a lateral surface (10) provided with a lower edge (14), the riser (1) comprising a second sealing joint movable in translation or rotation relative to the lateral surface.

7. Fuse riser (1) according to any one of claims 1 to 6, wherein the joint has a length between 50 cm and 30 m and / or a translational stroke between 5 cm and 5 m.

8. Fuse riser (1) according to any one of claims 1 to 7, wherein the critical angle (a c The tilt angle is between 10° and 20°.

9. Fuse riser (1) according to any one of claims 1 to 8, further comprising hydraulic communication means (20, 22) configured to supply a negative pressure chamber (18) of the trough (2) with water when the water level of the hydraulic structure exceeds a critical water height (Hc), the negative pressure chamber (18) being configured to, once filled with water, exert a negative pressure sufficient to trigger the tipping and / or lifting of the trough (2), thus causing the removal of the trough (2) from the sill (30) of the spillway of the hydraulic structure.

10. Method of using a fusible riser according to any one of claims 1 to 9, the method comprising a step of rotating the fusible riser and a subsequent step of translating the sealing gasket.

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