EP0493183A1 - Spillway for exceptional floods for barrages comprising et least two spillways - Google Patents

Abstract

In order at less cost to replace particular sluices so as to close off virtually permanently, except during the passage of exceptional floods, all or part of the free spill-over sill (6) of a barrage, the invention provides the arrangement on the sill (6) of the spillway (5) a shutter (10) consisting of at least one solid element (11), said shutter (10) or the shutter elements (11) being made fusible by tilting for a predetermined water load corresponding to a level (N) at most equal to the maximum level (RM) and then allowing the passage of the exceptional floods, smaller floods being discharged by means of another permanent device (7). <IMAGE>

Description

The present invention relates to an exceptional spillway for dams and similar works of the type comprising two flood evacuation devices, one of the two devices being constituted by a spillway threshold whose crest is located at a first predetermined level lower than 'a second predetermined level corresponding to a maximum level or highest water level for which the dam is designed, the difference of said first and second levels corresponding to a predetermined maximum flow of an exceptional flood, and a mobile rise closing said threshold.

The current state of practice in the design and construction of dams means that their drainage structures must be dimensioned for significant flood conditions (millennium or decamillenary for example). Consequently, most of the time, only a very small part of the evacuation capacities of said structures is used. In addition, it is known to regulate the discharges evacuated by the overflow threshold using valves, in particular to increase the capacity for retaining or blocking floods from the dam.

Under these conditions, it is clear that the said valves must close off the entire overflow threshold, but that most of them could remain closed almost permanently in the absence of exceptional floods and only open every 20 or 50 years for example. In the case where the other evacuation device allows the evacuation of the most frequent floods (such as for example bottom, middle bottom or surface evacuators, gated or not, where the water intake of a factory hydroelectric, or any other water drainage device), it is also clear that all of said valves could remain closed almost permanently.

Furthermore, the non-opening of the valves, whatever their nature, remains an important cause of dam failure. These valves therefore have the drawback of poorer operational safety than free overflow thresholds; moreover they are expensive.

Various economic devices have been proposed and already exist for closing a free spillway threshold such as sandbags or cofferdams (also called Flashboards) or other similar shutter devices which require human intervention prior to each flood and therefore present a major operational hazard.

There is also, on certain large embankment dams, a section of fusible dam, leveled at a lower level than that of the rest of the structure and operating according to the principle of the erosion of its constituent materials, erosion which is generated by a extreme rise in the level of the reservoir during a flood of very exceptional importance. The purpose of this fuse dam is in fact to avoid the uncontrolled and catastrophic discharge of an extreme flood on the whole of a structure, by concentrating the effects of the flood on a section specially equipped to break by erosion and thus offer additional evacuation capacity. After the rupture of the fusible dike, major repair work would be necessary to allow normal operation of the structure again. On the other hand, opening a fusible dam can lead to too rapid an increase in the downstream flow.

We also know the fuses increases as described in the previous patent applications of the plaintiff N ° 90 403 592.0 and N ° 90 403 593.8 respectively filed on 14.12.90 and 14.12.90 and both entitled "Spillway spillway for dams and similar structures ". These increases have the advantage of allowing the threshold to be closed at low cost. However, insofar as they are sized to evacuate low or medium flow floods, they must have a lower height than the level of the highest waters.

The problem that the present invention seeks to solve is to close almost permanently, at a cost much lower than that of the valves and at a higher height than before, all or part of a free overflow threshold while allowing , in a completely reliable manner, the evacuation of exceptional floods, without external intervention and without major modification of the structure. The present invention therefore constitutes an economical substitute for the fraction of valves intended solely for discharging the least frequent floods.

To the knowledge of the applicant, it therefore seems that no existing device satisfactorily meets the objectives indicated above, with simple operation and for a moderate investment cost.

According to the present invention, the above-mentioned problem is solved by the fact that the rise comprises at least one rigid and massive rise element, which is placed on the crest of the overflow threshold and is held in place thereon by gravity, said element having a predetermined height at least equal to the difference of the first and second predetermined levels and being dimensioned in size and weight so that the moment of the forces applied by the water to the riser reaches the moment of the forces of gravity which tend to keep the rising element in place on the overflow threshold, and that consequently said rising element is unbalanced when the water reaches a third predetermined level at most equal to the second predetermined level.

Under these conditions, it is clear that all or part of the overflow threshold can be closed by the rising elements. The raising element (s) can be manufactured at a moderate cost compared to the valves and, in the case where they are installed on the threshold of an existing dam, this installation, possibly joined to the installation of the valves, can be made without major modifications to the overflow threshold of the dam, such as we will see it later. It is also clear that for medium-sized floods, as long as the water level does not reach said third predetermined level, which can be determined in practice so as to be equal to or slightly lower than said second predetermined level , i.e. the level of the highest water, the water can be evacuated by valves or other devices sized for the most common flow rates, without this resulting in destruction of the rise and, consequently, without that the spillway ceases to be blocked by said rise. On the other hand, in the case of an exceptional flood, the water level reaches the third predetermined level, one or more rising elements are automatically unbalanced and driven by the water under the sole action of the forces of water, therefore without any external intervention being necessary, thus restoring the threshold to its full evacuation capacity.

Although, theoretically, this is not absolutely essential, a stop of predetermined height is preferably provided on the threshold overflowing at the foot of the raising element, on the downstream side thereof, to prevent it from sliding towards the downstream on the threshold, without however preventing it from tipping over the stop when the level reaches said third predetermined level. Of course, in this case, the height of the stop is taken into account as will be seen below for the dimensioning in size and weight of the raising element or elements.

A seal may be disposed between the overflow threshold and the base of the riser, near the upstream edge of said base. However, such a seal is not absolutely essential if, in the absence of a seal, water leaks between the raising element and the overflow threshold are low and if the area of the overflow threshold on which the said elevation element (s) rests is suitably drained so that no appreciable underpressure can be established under the said elevation element (s). However, as we will see further on, means may be provided for automatically establishing an underpressure under the said elevation element or elements when the water level reaches said third predetermined level, in order to promote the imbalance and tilting of said elevation element (s) at the time where it becomes essential to evacuate an exceptional flood.

The invention can be applied both to the spillway of an existing dam and to that of a dam under construction. In the first case, the crest of the overhanging threshold can be leveled off at a level lower than said first predetermined level and the one or more raising elements are placed on the leveled threshold and seal it off. It is thus possible to obtain greater security than with the undisturbed overflow threshold, since the opening which is obtained after tilting of the elevating element or elements has a greater height than in the case of an undisturbed overflow threshold. , thus allowing to evacuate a higher flood flow than the maximum flow of the exceptional flood for which the dam was originally designed.

Similarly, in the design of a new dam, it will be possible to adopt a greater difference between the first and second predetermined levels (which contributes to increasing safety, or at equal maximum flow, to reducing the cost of works such as couriers) without fear that this would prevent the control of the flows leaving the dam, thanks to the joint use of devices evacuating the most common flows and one or more rising elements in accordance with the present invention.

In these two cases, the choice of the difference between the first and second predetermined levels will result from an optimization between increase in safety, reduction in the cost of the works and possible increase in the cost of the valves located on the spillway.

If several augmentation elements are provided, each augmentation element or a group of elements of rise can be dimensioned so as to tilt for a predetermined water level lower than that to which another element or group of rise elements will tilt, the latter being itself dimensioned so as to tilt for a higher water level lower than that to which a third element or group of rising elements will switch, and so on. In this way, a progressive increase in the evacuation capacity is obtained, if necessary, depending on the extent of the flood.

It will also be noted that, if one or more rising elements have been tilted and driven out by an exceptional flood, they can be easily and economically replaced by other rising elements, without having to carry out major repairs, after the flood has been evacuated.

Other characteristics and advantages will appear during the description which follows of various embodiments of the present invention given by way of example, with reference to the appended drawings in which:

FIG. 1 is a perspective view showing a structure to which the invention can be applied, such as a dam, its exceptional spillway spillway with a free spillway threshold and another spillway intended for the evacuation of common floods and provided with valves.

FIG. 2 is a perspective view showing a structure to which the invention can be applied, such as a dam, its exceptional spillway spillway with a free spillway threshold and another device for discharging water such as a spillway bottom, winnowed or not, or a hydroelectric plant.

FIG. 3a is an elevation view of the exceptional spillway spillway of FIG. 1 or 2, from the downstream side and equipped with a fusible link according to the present invention.

Figure 3b is a plan view of the weir of Figure 3a.

Figure 3c is an elevational view of another weir equipped with a fusible link according to the present invention.

Figures 4a and 4b are views in vertical section explaining the operation of the fusible link.

FIG. 5 is a graph showing the various forces which, in service, can be applied to a riser according to the present invention.

FIG. 6 is a graph representing the variations of the moments of the driving and resistant forces as a function of the height of water above the overflow threshold.

Figure 7 is a vertical sectional view showing a lifting element of the present invention, which is associated with a tilt trigger device.

FIG. 8 is a plan view of a weir provided with another tilt trigger device.

Figures 9a to 9c show in perspective various embodiments of a rising element according to the present invention.

Figures 10 and 11 show in vertical section two other alternative embodiments of the raising element of the invention.

Figure 12 is a perspective view showing two adjacent risers according to another embodiment of the invention.

FIG. 13 is a vertical section view of one of the rising elements in FIG. 12.

FIGS. 14 and 15 are views of the raising element respectively according to the arrows F and G of FIG. 13.

FIGS. 16a and 16b show on a larger scale and in section, a detail of the raising element of FIG. 13.

Figure 17 is a figure similar to Figure 13 and shows an alternative embodiment.

Figure 18 is a plan view of part of the threshold of the spillway in the case of the variant of Figure 17 and before installation of the rising elements.

The structure 1 represented in FIG. 1 and in FIG. 2 can be an embankment dam or a concrete or masonry dam. However, it should be noted that the invention is not limited to the type of dam shown in Figure 1 or in Figure 2, but that on the contrary it can be applied to any type of known dam with a free overflow threshold.

In Figures 1 and 2 the reference number 2 designates the crest of the dam, the number 3 its downstream facing, the number 4 its upstream facing, the number 5 a spillway spillway, the number 6 the threshold of the weir 5, the reference number 7 generally designates a device for discharging common floods. The spillway 5 can be located in the central part of the dam 1 or at the end of it or even excavated on a bank without this altering the possibility of using the invention. In FIG. 2, the discharge device 7 is a conventional device for discharging bottom water. In Figure 1, the discharge device 7 is a spillway threshold equipped with conventional surface valves. However, it goes without saying that the device 7 could be constituted by any other known device for discharging floods without this altering the possibility of using the invention.

In a structure of the type to which the invention applies, the level of the reservoir in the absence of a flood is always less than or equal to the level RN of the crest 8 of the weir 6. The level of the reservoir in the event of flood is always less than or equal to RM or highest water level (PHE).

The present invention makes it possible almost permanently to close the weir 6. For this purpose, the invention provides for having on the overflow threshold 6 a rise 10 constituted by at least one solid element 11, for example five elements 11a - 11e as shown in Figures 3a and 3b, said rise 10 or the elements 11 being made fusible by tilting for a predetermined water load corresponding to a level N at most equal to the maximum level RM and then allowing the passage of the strongest floods.

Of course, the number of elevating elements 11 is not limited to five elements as shown in Figures 3a and 3b, but can be smaller or larger depending on the length of the weir 5 (measured in the longitudinal direction of the dam) . Preferably, the number of elevating elements 11 is chosen so as to obtain low unit masses allowing easy installation and replacement of said elevating elements.

Each rising element 11 has a height H₁ greater than RM, is placed on the overflow threshold 6 and is held thereon by gravity. Preferably, each rising element 11 is retained against any sliding downstream, by a stop 12 located at the foot of the element 11, on the downstream side thereof. The stop 12 can for example be embedded in the threshold 6, as shown for example in Figure 4a, and it can be discontinuous as shown in Figures 3a and 3b. However, if desired, the stop 12 could be continuous. As will be seen below, the height of the stop 12 is predetermined, but it can be variable according to the forces involved and according to the water level from which it is desired to initiate the tilting of each rising element 11.

As shown in FIG. 3b, a conventional seal 13, for example made of rubber, is provided at each of the two ends of the riser 10 between it and the lateral flanks 14 of the weir 5. When the riser 10 is formed by several elements 11, seals 13 are also provided between the vertical side walls, two by two opposite, adjacent elevation elements 11 as is also visible in Figure 3b. Preferably a seal 15 is also provided between the overflow threshold 6 and the base of the elevation elements 11 near the upstream edge 16 of said base as is for example visible in Figures 4a and 4b. As shown in Figure 3b, the seals 13 and the seal 15, when the latter is provided, are arranged in the same vertical plane. Instead of providing the joint 15 or in addition to it, a drainage system can be arranged continuously in the overflow threshold 6, in the zone of the latter underlying upward 10, in order to dry out this area and to avoid that under normal pressure, pressure is applied to the elevating elements 11.

As shown in FIG. 3c, in the case where a dam would have a free overflow threshold as the only device for discharging floods, it is possible to envisage equipping only part of this threshold with one or more valves v and the remaining part of a rising fuse 10 in accordance with the invention. A dam in accordance with the invention is thus obtained with a single overflow threshold 6 with which two evacuation devices are associated, one (7) equipped with at least one valve v for the evacuation of current floods, the another equipped with the 10 fuse riser for evacuation of exceptional floods.

As will be explained below, each rising element 11 is dimensioned so as to be freestanding for a water load lower than a predetermined level N, itself at most equal to the maximum level RM of the highest admissible water in the dam. Thus by supposing for example that said predetermined level is equal to the level RM, as long as the level of water remains lower than the level RM for floods of low or average importance the water is retained by the increases as shown in figure 4a without that the rise is not destroyed.

On the other hand, if the water level reaches, in the aforementioned hypothesis, a predetermined level N equal or slightly lower than the maximum level RM in the case of a heavy flood or exceptional flood or damage in the operation of the device 7, at least one element 11 of the rise 10 is unbalanced under the thrust of the water and rocks around the stop 12 as shown in FIG. 4b and the element or elements 11 which are tilted are evacuated by the water of the flood at least up to the foot of the weir 5, thus allowing the evacuation of the strongest floods. After evacuation of a strong flood having caused the tilting of the rise 10, the water level returns to the level of the normal reservoir RN or to a level still lower. We can possibly provide some spare elements 11, permanently available on the dam site, to allow repair of the surge 10 if necessary. It should however be noted that the non-replacement of one or more elements 11, after an exceptional flood or damage in the operation of the device 7 having caused the tilting of at least one element 11, does not reduce the operational safety of the 'work.

We will now give a numerical example of the design of a fusible link according to the present invention. Usually, the dams and overflow weirs are sized so that the level of the lake (level of the reservoir) reaches the maximum level RM for the exceptional flood envisaged (project flood). This flood may for example be the flood occurring only one year in a thousand (millennial flood).

To fix the ideas, we will assume that the flow of this project flood is for example 900 m3 / s, that the maximum flow reached on average over 50 years, much lower than that of the project flood is 100 m3 / s, that the free overflow threshold 6 on which the rise 10 is placed has a length of 40 m and that the device 7 has an evacuation capacity of 100 m³ / s.

d'après laquelle on peut voir que H est sensiblement égal à 5 m dans l'hypothèse faite plus haut. Toujours dans cette hypothèse, le niveau du seuil 6 du déversoir 5 est arasé à 5 m en dessous du niveau maximal RM pour permettre l'évacuation de la crue millénale. On peut alors équiper le seuil 6 de hausses conformes à la présente invention, dont la hauteur est supérieure ou égale à 5 m.Under these conditions, the height H of the sheet of water necessary to evacuate the flow of the fraction of the project flood that does not evacuate the device 7 corresponds to 20 m³ / s per linear meter of threshold, This height H can be calculated by the following formula: $${\text{Q = 1.8 <figure-callout id="3" label="H" filenames="imgf0002.png" state="{{state}}">H</figure-callout>}}^{\text{3/2}}$$

according to which we can see that H is substantially equal to 5 m in the hypothesis made above. Still in this hypothesis, the level of the threshold 6 of the weir 5 is leveled 5 m below the maximum level RM to allow the evacuation of the millennial flood. The threshold 6 can then be fitted with risers in accordance with the present invention, the height of which is greater than or equal to 5 m.

The tilting of the elevating element or elements 11 and, consequently, their destruction depends on the balance between, on the one hand, the driving moment, that is to say the moment of the forces which tend to overturn the rising element considered, and, on the other hand, the resisting moment, ie the moment of the forces which tend to stabilize said rising element. If a trigger device directly linked to the water level is not provided, to trigger the tilting of the raising element with precision for a predetermined water level, the water height corresponding to the above-mentioned equilibrium cannot be fixed only with a margin of uncertainty of up to 0.2 m. Under these conditions, it is necessary, for safety, to reduce the tilting height of the elevating element or elements 11 by an amount corresponding to this margin of uncertainty, for example 0.2 m. However, this uncertainty can be reduced by providing a trigger device which will be described later with reference to FIG. 7.

FIG. 5 shows the various forces which, in service, can be applied to a lifting element 11 of the present invention. For the description which follows, it will be assumed that the element 11 has a parallelepiped shape and has a width L and a height H₁. In FIG. 5, B denotes the height of the stop 12 above the threshold 6, and z denotes the water level. The driving forces that tend to tilt the elevating element 11 are the thrust P of the water on the upstream face of the elevating element 11 and the underpressure U which is possibly exerted on the base surface of said elevating element and which is due to the existence of possible leaks at the seals or to the presence of a trigger device which will be described later. The resistant force which tends to stabilize the raising element 11 is its self-weight W.

• a/ si : O < z < 3 B : $$\text{P =}\frac{\text{1}}{\text{2}}{\text{. γ}}_{\text{ω}}\text{. z²}$$
  
  $$\text{U =}\frac{\text{1}}{\text{2}}{\text{. γ}}_{\text{ω}}\text{. z . L}$$
  
  $${\text{W = γ}}_{\text{b}}\text{. H₁ . L}$$
  
  $$\text{Mm = 0}$$
  
  $$\text{MmU =}\frac{\text{1}}{\text{3}}{\text{. γ}}_{\text{ω}}\text{. z . L²}$$
  
  $$\text{Mr =}\frac{\text{1}}{\text{2}}{\text{. γ}}_{\text{b}}\text{. H₁ . L² +}\frac{\text{1}}{\text{2}}{\text{. γ}}_{\text{ω}}\text{.z² . (B -}\frac{\text{z}}{\text{3}}\text{)}$$
  
• b/ si : 3 B < z < H₁ $$\text{P =}\frac{\text{1}}{\text{2}}{\text{. γ}}_{\text{ω}}\text{. z²}$$
  
  $$\text{U =}\frac{\text{1}}{\text{2}}{\text{. γ}}_{\text{ω}}\text{. z . L}$$
  
  $${\text{W = γ}}_{\text{b}}\text{. H₁ . L}$$
  
  $$\text{Mm =}\frac{\text{1}}{\text{2}}{\text{. γ}}_{\text{ω}}\text{. z² . (}\frac{\text{z}}{\text{3}}\text{- B)}$$
  
  $$\text{MmU =Mm +}\frac{\text{1}}{\text{3}}{\text{. γ}}_{\text{ω}}\text{. z . L²}$$
  
  $$\text{Mr =}\frac{\text{1}}{\text{2}}{\text{. γ}}_{\text{b}}\text{. H₁ . L²}$$
  

To calculate the values of P, U and W as well as the values of the corresponding motor and resistance moments with respect to the stop 12, two cases should be considered as a function of the water height z above the threshold 6 The values P, U and W and of the corresponding motor and resistance moments are summarized below for the different cases, said values being given per unit of length of the rising element 11.

• a / si: O <z <3 B: $$\text{P =}\frac{\text{1}}{\text{2}}{\text{. γ}}_{\text{ω}}\text{. z²}$$
  
  $$\text{U =}\frac{\text{1}}{\text{2}}{\text{. γ}}_{\text{ω}}\text{. z. L}$$
  
  $${\text{W = γ}}_{\text{b}}\text{. H₁. L}$$
  
  $$\text{Mm = 0}$$
  
  $$\text{MmU =}\frac{\text{1}}{\text{3}}{\text{. γ}}_{\text{ω}}\text{. z. L²}$$
  
  $$\text{Mr =}\frac{\text{1}}{\text{2}}{\text{. γ}}_{\text{b}}\text{. H₁. L² +}\frac{\text{1}}{\text{2}}{\text{. γ}}_{\text{ω}}\text{.z². (B -}\frac{\text{z}}{\text{3}}\text{)}$$
  
• b / si: 3 B <z <H₁ $$\text{P =}\frac{\text{1}}{\text{2}}{\text{. γ}}_{\text{ω}}\text{. z²}$$
  
  $$\text{U =}\frac{\text{1}}{\text{2}}{\text{. γ}}_{\text{ω}}\text{. z. L}$$
  
  $${\text{W = γ}}_{\text{b}}\text{. H₁. L}$$
  
  $$\text{Mm =}\frac{\text{1}}{\text{2}}{\text{. γ}}_{\text{ω}}\text{. z². ((}\frac{\text{z}}{\text{3}}\text{- B)}$$
  
  $$\text{MmU = Mm +}\frac{\text{1}}{\text{3}}{\text{. γ}}_{\text{ω}}\text{. z. L²}$$
  
  $$\text{Mr =}\frac{\text{1}}{\text{2}}{\text{. γ}}_{\text{b}}\text{. H₁. L²}$$
  

In the above-mentioned formulas, P, U, W, L, H₁, B and z have the meanings already indicated above. Mm is the motor moment in the absence of U pressure, MmU is the motor moment in the presence of U pressure, γ _ω is the density of water and γ _b is the average density of l 'rising element, and Mr is the resistant moment.

In the graph in FIG. 6, the plots A, C and D respectively represent the variations of Mr, Mm and MmU as a function of the water height z above the threshold 6. The plots A, C and D have been obtained from the formulas indicated above and for H₁ = 5m, L = 2.6m, B = 0.15m, γ _ω = 10 kNm⁻³ and γ _b = 24 kNm⁻³.

By considering the plots A and C we see that the motor moment Mm (without under-pressure U) reaches the same value as the resistive moment Mr for a value of z approximately equal to 4.8m. In other words, in the absence of an underpressure U the tilting of the rising element 11 will occur when the water level reaches a height of 4.8m above the threshold 6. Similarly, in considering the plots A and D, we see that in the presence of an underpressure U, the motor moment MmU reaches the same value as the resistive moment Mr for a value of z of about 4.4m. The rising elements thus dimensioned will adapt to a threshold whose highest water corresponding to the RM level is 5m. According to the formulas (11) and (13), we see that if we had wanted that, in the absence of U-pressure and without changing the value of the height H₁ of the rising element 11, the tilting of this last occurs for a value of z equal to 4.5m, it would have been necessary to decrease the value of γ _b and / or the value of L and / or the value of B compared to the values indicated above.

From the above, it can be seen that, by an appropriate dimensioning in size and weight of the lifting element 11 and by an appropriate dimensioning of the stopper 12, it is possible to cause the raising element 11 to tilt for a predetermined water level. It can also be seen that if the raising element 11 has been dimensioned to switch to a predetermined water level in the absence of an underpressure at its base and if the seal between the raising element and the threshold 6 is not perfect, an underpressure will be exerted on the base of the raising element, which will cause it to tip over for a water level below the aforementioned predetermined water level. A leak is therefore not catastrophic but rather constitutes a safety factor insofar as it helps the tilting of the lifting element.

This can be used to bring about the tilting of the raising element 11 in an even safer and more precise manner with regard to the level of water at which the tilting occurs. Indeed, it may be advantageous to take measures so that the underpressure U applied to the raising element remains zero or very low as long as the water level remains below a predetermined level, and so that a substantially higher pressure is suddenly applied to the rising element 11 at the instant when the water level reaches said predetermined level, the dimensioning of the elements being such that at this instant the driving moment passes abruptly of a value Mm a little smaller than the value of the moment resistant Mr to a value MmU substantially greater than the value of said resistive moment Mr. For this purpose, one can use for example a trigger device such as that shown in FIG. 7. The trigger device shown in FIG. 7 is essentially constituted by a pressurization pipe 21 which , in normal service, puts the area underlying the rising element 11 in relation to the atmosphere, the upper end 21a of the pressurization pipe 21 being located at a level equal to or lower than the level N for which it is desired the tilting of the elevating element 11 occurs (the difference between the level of the top of the pipe and the level N corresponding to the height of the sheet of water pouring into the pipe and necessary for its filling), The pipe 21 can pass through the elevation element 11 as shown in solid lines in FIG. 7, or it can pass outside of the elevation element 11 as shown in phantom in 21 ′ in the f igure 7, so that its upper end is placed outside the raising element 11. The pressurization pipe can still be partially embedded in the threshold 6 as is also shown in phantom in 21˝ in the figure 7. In the case where several raising elements 11 are provided and must tilt for different water levels, at least one pressurization pipe 21 is associated with each raising element and each pressurization pipe 21 extends upwards up to the level for which each element must switch. Naturally, in this case, the zones of the threshold 6 which are underlying the raising elements which have to tilt for different water levels, must be isolated from each other by seals suitably arranged.

In addition to or as a replacement for the trigger device 21 of FIG. 7, it is possible to envisage implementing another trigger device (FIG. 8) essentially consisting of a pipe 22 which is arranged according to one of the methods indicated above for the pipe 21 and of which the end 23 which is distant from the zone underlying the raising element 11 is connected to a pressurizing device 24 which can be controlled by a tap 25 controlled by an automatic and / or manual control device 26 and which makes it possible to trigger the tilting of the increases when they would have remained stable. The pressurizing device 24 may for example be a reservoir, higher than the threshold 6, containing water, the free surface of which is in contact with the atmosphere. The device 24 can also be a reserve of fluid maintained under pressure. The device 26 may for example be a valve operating handwheel 25, or an automatic control of the valve 25 connected to a sensor of the level of the reservoir or of the flow rate upstream of the reservoir, or a combination of these elements. It is clear that according to the value of the pressure applied by the device 24, the tilting of at least one of the raising elements 11 is only possible from the moment when the water has reached a certain level in the detention. This device facilitates a premature selective tilting of the elevating elements 11 to prevent a very strong flood for example.

This solution must in particular allow, when an exceptional flood is announced, to start emptying the tank in advance by voluntarily and / or automatically causing the tilting of at least one rising element 11 and reducing on the one hand the number of elements which will have to switch during the full effect of the flood on the rise 10, and on the other hand the maximum flow of the flood downstream.

It may be advantageous, in order to improve the safety of an existing structure whose overflow threshold 6 had been initially leveled, depending on an exceptional flood initially chosen, at a level determining the level of the normal reservoir RN, to level the threshold 6 of a few decimeters below its current level (corresponding to RN) and to place on the derased threshold 6 a rising fuse 10 in accordance with the present invention, composed of at least one rising element 11 sized in size and weight as described above to switch around the stop 12 when the water level reaches a predetermined level. Under these conditions, the probability of opening of the increase 10 is not modified but, in the event of an exceptional flood, the flow section available after total destruction of the increase 10 is notably increased for the same water level in the reservoir, which makes it possible to safely evacuate a flood having a flow rate much higher than that of the flood for which the structure was initially dimensioned.

In the above description, it has been assumed that each raising element 11 is constituted by a block having roughly a parallelepiped shape. Each elevation element 11 may consist of a hollow block as shown in FIG. 9a, comprising one or more cells filled with a ballast 32, such as for example sand, gravel or other materials weighing in bulk. A cover (not shown) can be provided for closing the cell or cells 31 after they have been filled with ballast. The embodiment of FIG. 9a is particularly suitable when the rise 10 must comprise several rise elements all having the same height, but having to tilt for different water levels. In this case, it suffices to adjust the weight of each of the elevating elements 11 by an appropriate amount of ballast 32 to obtain the tilting of the corresponding elevating element 11 for the desired predetermined water level N. It also has the advantage of facilitating the installation of the risers 11, which can be placed empty of their ballast on the weir 6 in order to facilitate their handling. Finally, it improves the evacuation of the rises during their tilting since the force of the water can empty them of their ballast and thus reduce their weight.

According to another embodiment of this Invention, each elevating element 11 may consist of an assembly of plates, made of concrete, steel or any other suitable rigid and heavy material. As shown in FIG. 9b, the assembly of plates can comprise a rectangular base plate 33, horizontal or substantially horizontal, and a frontal rectangular plate 34, vertical or making with the vertical an angle α which can reach 30 degrees, which stands from the downstream edge of the base plate 33. It will be noted that, in this case, the weight of the water column situated above the base plate 33 contributes, as a resisting force, to stabilize the element rise until the water level has not reached the predetermined level at which the tilting of said rise element occurs.

As shown in FIG. 9c, the plate assembly can comprise, in addition to the plates 33 and 34, two side plates 30 which are joined by their lower edge to the base plate 33 and by one of their vertical edges to the front plate 34. In the particular arrangement of FIG. 9c the lateral plates 30 have the advantage of limiting the lateral water losses at the start of the tilting, linked to the rupture of the seal 13. It consequently improves the precision of the tilting and avoids any oscillatory phenomenon.

10 shows in vertical section an elevation element 11 similar to those of FIG. 9b or 9c equipped in addition with a pressurization pipe 21 having the same function as that of FIG. 7. In FIG. 10, the horizontal plate 33 is fixed to the front plate 34 so as to be at a distance above the threshold 6, and it comprises, on the upstream side, a flange 33a directed downwards. The seal 15 is disposed between the flange 33a and the threshold 6. Below the plate 33 is thus formed a chamber 35, into which the pipe 21 opens at its lower part. An orifice 36 is provided at the base of the plate 34, the orifice 36 having a smaller section than that of the hose 21.

With the rising element of figure 10, when, in service, the water level is close to the level N, but lower than this, the possible waves on the surface can cause water to enter the pipe 21. These water inlets will partially fill the chamber 35 which, at the same time will empty through the orifice 36. This avoids that a pressure is applied to the plate 33 because of the waves, as long as the water level has not reached the level N at which it is desired that the tilting of the raising element 11 occur. The chamber 35 and the orifice 36 therefore make it possible to increase the precision of the level at which the tilting occurs. Of course, one can provide under the element 11 of FIG. 7 a chamber similar to the chamber 35, as well as a drainage orifice for this chamber similar to the orifice 36.

Figure 11 shows, in vertical section, an elevation element 11 composed of several modules 11g to 11j which are stacked on top of each other. Said modules are made integral two by two by a connecting device 38 preventing the sliding of the upper modules downstream. The device 38 can for example be constituted by hooks, or by an interlocking of the modules one on the other. The modules can all have the same vertical dimension or different vertical dimensions; for example, the upper module 11j has a smaller vertical dimension than those of the other modules. With such a construction of the raising element, the operations of setting up the raising are facilitated. Advantageously, the device 38 can be designed so as to allow the modules to automatically detach in the event of tilting or under the external action of pushers or cables which can be operated, for example from a footbridge (not shown) spanning the weir. The two possible forms of execution of the device 38 already mentioned can fulfill these conditions.

In the embodiment shown in Figures 12 to 15, the parts of the raising element 11 which are identical or have the same object as those described above, are designated by the same reference number.

As indicated in FIGS. 12 and 13, the assembly of plates may comprise a base plate 33, substantially rectangular or trapezoidal, horizontal or substantially horizontal, and a front plate 34, rectangular or trapezoidal, vertical or making an angle with the vertical α up to 30 degrees. As is better visible in FIG. 13a, the lower edge of the front plate 34 is freely engaged in a groove 40 formed in the base plate 33 preferably near its downstream edge. A seal 41 is placed in the groove 40 between the plates 33 and 34. Of course, the front plate 34 can also be rigidly fixed to the base plate 33.

According to the embodiment shown in Figures 12 to 15, the plate assembly comprises at least one tie rod, for example two tie rods 30a which are joined at their ends to the base plate 33 and to the front plate 34. The setting using two tie rods 30a is preferable for the elevating elements 11 of great height, because it allows better transmission of the forces from the front plate 34 to the base plate 33. The tie rods can be made of steel or any other material appropriate. Of course, the tie rod (s) 30a can be replaced by one or more reinforcing plates similar to the plates 30 in FIG. 9c.

As shown in Figures 12 and 13, the base plate 33 is located at a certain distance above the threshold 6 and has, upstream side, a flange 33a directed downwards, downstream side, a flange 33b directed downwards , and on the lateral sides, two flanges 33c also directed downwards, these four flanges resting on a prefabricated frame 42 placed on the threshold 6 previously leveled or designed so appropriate. A layer of mortar 6a of appropriate thickness is then poured over the threshold 6 to coat the frame 42 so that its upper surface is flush with the final level of the threshold, ready to receive the raising element 11. Of course, the four ledges 33a, 33b, 33c can also rest directly on the threshold 6 if the latter has been previously fitted or designed in an appropriate manner.

A seal 15 is disposed between the flanges 33a, 33c and the frame 42 or the threshold 6 as appropriate. Below the plate 33 is thus formed a chamber 35, into which opens at its lower part 21b a pressurization pipe 21 and which makes it possible to favor the tilting with precision of the raising element 11, for a water level equal to the predetermined level N, thanks to the pressurization of the chamber 35, as described above with reference to FIGS. 7 and 10.

An orifice 36 is provided at the base of the downstream rim 33b of the base plate 33 for draining the chamber 35, when the latter is partially filled by the water inlets caused by the waves temporarily submerging the upper end 21a of the pipe 21 or by leaks at the seal 15.

According to the embodiment shown in FIGS. 12, 14 and 15, seals 13, made of rubber or any other suitable material, are provided at each of the lateral ends of the lifting elements 11. The design of the seal 13 must be such that the tilting of an elevating element 11, in the event that the elevation 10 is made up of several elevating elements 11 tilting for different water levels, does not cause the tilting of the other elevating elements 11 .

Figures 16a and 16b show in cross section two possible shapes for the seal 13 meeting this need.

The pressurization pipe 21 can stand vertically above the base plate 33, as shown in FIGS. 12 and 13 or obliquely upstream like the pipe 21 ′ in FIG. 7. The pipe 21 can still be partially embedded in the threshold 6 like the pipe 21˝ in FIG. 7.

In addition to or as a replacement for the pipe 21 in FIGS. 12 to 15, it is possible to envisage using another trigger device (FIGS. 17 and 18) similar to that of FIG. 8 and essentially constituted by a pipe 22 whose end 22a opens into the chamber 35 and the remote end 23 of which is connected to a pressurizing device 24. The pipe 22 can be fitted with a tap 25 controlled by an automatic and / or manual control device 26 as mentioned more high. The pressurizing device 24 may for example be a reservoir, higher than the threshold 6, containing water, the free surface of which is in contact with the atmosphere, or else the reservoir of water from the dam, which is the simplest solution to implement.

As shown in Figures 12, 13 and 17, each raising element 11 is preferably retained against any sliding downstream, by one or more stops 12 fixed or sealed in the threshold 6 or secured to the frame 42. As shown in particular Figures 12 and 17, this device can be supplemented by the installation on the plate 33 of a ballast 32 consisting either of a one-piece element, or of several stacked elements or of bulk materials arranged in a receptacle provided for this purpose. effect. This ballast 32 makes it possible to optimize the balance between the motor moment and the resistant moment, while favoring the production of rising elements 11, each part of which has a low unit weight facilitating handling and assembly.

Although after assembly, the raising element 11 is rigid and solid, the connections between its various constituent parts can be designed and produced so that after the tilting of a raising element 11, each constituting part can separate from others so that to have downstream only parts that are not bulky and easier to recover or leave lost. Thus in particular that in the embodiments of Figures 12 to 18, the tie rods 30a can be attached to the plates 33 and 34, for example by sets of rings and hooks detaching during the tilting of the element of rise. This design is particularly advantageous for large-sized lifting elements because it is also likely to facilitate handling and assembly by using elements of low unit weight.

• 1.- Pour les déversoirs importants, la fabrication et l'installation de ces hausses se révèlent plus économiques que celles de la fraction des vannes qu'elles remplacent et dans le cas le plus général, ne nécessitent pas de modifications majeures de l'ouvrage.
• 2.- Il permet d'obturer de façon quasi permanente et sur une hauteur plus élevée que celle autorisée par les hausses décrites dans les deux demandes de brevets 90403592,0 et 90403593,8 déjà citées, tout ou partie d'un seuil déversant libre, tout en permettant de façon totalement fiable, l'évacuation des crues exceptionnelles, et en règle générale, sans intervention extérieure.
• 3.- Ce dispositif autorise la mise en place d'éléments de hausse de faible largeur conduisant après basculement d'un élément de hausse à une faible augmentation du débit aval.

The raising device of the invention has many advantages:

• 1.- For large spillways, the manufacture and installation of these increases prove to be more economical than those of the fraction of the valves that they replace and in the most general case, do not require major modifications to the structure .
• 2.- It makes it possible to close almost permanently and over a height higher than that authorized by the increases described in the two patent applications 90403592.0 and 90403593.8 already mentioned, all or part of a free overflow threshold , while allowing totally reliable evacuation of exceptional floods, and as a rule, without external intervention.
• 3.- This device authorizes the installation of rising elements of small width leading after tilting of an increasing element to a slight increase in the downstream flow.

It is understood that the embodiments of the present invention which have been described above have been given for purely indicative and in no way limitative, and that many modifications can be easily made by those skilled in the art without departing from the scope of the present invention.

Claims (16)

1.- Exceptional spillway for dams and similar structures of the type comprising two flood evacuation devices (6,7), one of the two devices being constituted by an overflow threshold (6) whose crest (8) is located at a first predetermined level (RN) lower than a second predetermined level (RM) corresponding to a maximum level or highest water level (PHE) for which the dam (1) is designed, the difference between said first and second levels (RN and RM) corresponding to a predetermined maximum flow of an exceptional flood, and a mobile rise (10) closing said threshold (6), characterized in that the rise (10) comprises at least one rise element (11 ) rigid and massive, which is placed on the crest (8) of the overflow threshold (6) and is held in place thereon by gravity, said raising element (11) having a predetermined height at least equal to the difference of first and second predetermined levels e t being dimensioned in size and weight so that the moment of the forces applied by the water to the rising element reaches the moment of the gravitational forces which tend to keep the rising element in place on the overhanging threshold (6) and that consequently said rising element is unbalanced, when the water reaches a third predetermined level (N) at most equal to the second predetermined level (RM). 2.- spillway according to claim 1, characterized in that there is provided a stop (12) of predetermined height (B) on the overflow threshold (6), at the foot of the raising element (11) on the downstream side of it, to prevent it from sliding downstream on said threshold. 3.- spillway according to claim 1 or 2, characterized in that, in the case of an existing weir (5), the crest of the overflow threshold (6) is leveled at a level lower than said first predetermined level (RN ), and in that the raising element (11) is placed on the leveled threshold. 4. Evacuator according to any one of claims 1 to 3, characterized in that a seal (15) is disposed between the overflow threshold (6) and the base of the rising element (11) from the upstream edge (16) of said base. 5. Evacuator according to any one of claims 1 to 4, characterized in that said raising element (11) is in the form of a roughly hollow rectangular block, filled with a ballast (32). 6.- spillway according to any one of claims 1 to 4, characterized in that said raising element is constituted by an assembly of plates (33, 34), which comprises a substantially horizontal base plate (33) and a plate front (34) which makes an angle (α) from 0 to 30 degrees with the vertical and which rises from the base plate (33). 7. Evacuator according to claim 6 characterized in that said raising element comprises side plates (30). 8. Evacuator according to any one of claims 1 to 7, characterized in that it comprises at least one pressurization pipe (21) which, in normal service, puts the zone underlying the raising element ( 11) in relation to the atmosphere, the upper end of the pressurization pipe (21) being located at a level equal to or lower than said third predetermined level (N) and directly above the raising element (11) or upstream of it. 9. Evacuator according to any one of claims 1 to 8, characterized in that a pipe (22) connects the area underlying the raising element (11) to a pressurizing device (24) by through a tap (25), the opening of which is controlled by a control device (26). 10.- spillway according to any one of claims 1 to 9, characterized in that several rising elements (11) are arranged side by side along the ridge (8) of the overflow threshold (6), seals sealing (13) being arranged between the vertical walls mutually facing the adjoining rising elements. 11. Evacuator according to any one of claims 1 to 10, characterized in that the raising elements (11) are dimensioned so that at least one first raising element (11c) is unbalanced when the water reaches said third predetermined level (N₁), the latter being lower than said second predetermined level (RM), that at least one second raising element (11b, 11d) is unbalanced when the water reaches a fourth predetermined level (N₂ ) between the second and third predetermined levels (RM and N₁), and that at least one third rising element (11a, 11e) is unbalanced when the water reaches a fifth predetermined level higher than the fourth level (N₂) and at most equal to the second predetermined level (RM). 12. -Evacuator according to any one of claims 1 to 11, characterized in that a chamber (35) is formed at the base of the raising element (11) between it and the threshold (6) of the weir, and in that an orifice (36) is provided on the downstream side of the raising element for draining said chamber (35). 13.- Evacuator according to claim 12, attached to claim 8 or 9, characterized in that the pipe (21 or 22) opens into said chamber (35). 14.- Evacuator according to claim 1, characterized in that a raising element (11) consists of several parts assembled to each other detachably so as to be able to separate spontaneously after the element is tilted. 15.- spillway according to claim 14, characterized in that the raising element (11) consists of several modules (11g, 11j) stacked on each other and made integral two by two by a connecting device (38 ) preventing any sliding of the upper module downstream. 16. Evacuator according to claims 6 and 14, characterized in that the base plate (33) has a groove (40) in its upper surface, in that the lower edge of the front plate (34) is freely engaged in the groove (40) and in that at least one tie rod (30a) is detachably attached by its ends to the base plate (33) and to the front plate (34).

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