GATE FOR FREE SPILLWAY WEIRS

Abstract

A gate is provided with a barrier capable of retaining water with a central barrier wall that is inclined in a direction away from the water, a bottom structure beneath the water that is capable of delimiting by a weir a bottom chamber filled with air and holding the barrier in its water retaining position by the water pressure exercised on said bottom structure, and an inlet extending beyond the retaining level of the barrier with an upper opening that allows water to flood the bottom chamber so as to offset the water pressure on the bottom structure and thereby allow a tipping of the gate, wherein a wall structure forms a wall chamber on the central barrier wall, wherein the wall chamber is capable of being flooded so as to assist the tipping of the gate.

Description

TECHNICAL FIELD

The invention relates to a gate for free spillway weirs according to the preamble of claim 1.

BACKGROUND ART

Excluding means involving a major risk such as sandbags, flashboards and fuse plugs, the current practice when designing overspill dams is such that the designer has to choose between free, gated and fuse gated spillways.

Free spillways are extremely reliable but do not allow operating dams to their full storage capacity.

Gated spillways, such as conventional and inflatable gates, allow operating dams to their full storage capacity but are not fully reliable, because 30% of gate dam failures are due to a malfunctioning of gates.

A particular type of floodgates is known as fusegates, which are arranged side-by-side on a weir to form a watertight barrier in order to store water. In case of huge floods, they are configured to automatically tip and be washed away in order to protect the dam from being overtopped and/or to prevent the flooding of the reservoir banks. Typically, each gate is configured to tip at a predetermined flood level, so that multiple gates can be configured to gradually open as the flood level is rising.

Therefore, fusegate spillways are the preferred choice when the probability of an overturning of the gate is low. However, it is particularly desirable to reduce the effect of abnormal loads, such as floating debris, or external parameters, such as civil engineering spillway tolerances, on the reliability of the gate. It is also particularly desirable to be in a position to precisely set the gate stability.

U.S. Pat. No. 5,032,038 (A) discloses a fusegate on the sill of a spillway comprising at least one heavy element, said fusegate being capable of resisting the water loads when spilling moderate heads (for discharging the floods of shorter recurrence intervals) by virtue of their own weight but breaching by overturning at a predetermined head corresponding to a level not higher than a predetermined maximum water level in order to discharge larger floods.

EXTENDED DESCRIPTION OF THE INVENTION

The problem solved by the present invention is to further develop a gate for free spillway weirs according to the preamble of claim 1, so that the gate is improved with respect to its stability.

This problem is solved by a gate for free spillway weirs comprising the features of claim 1. Preferable embodiments are set forth in the dependent claims.

The gate for free spillway weirs according to the invention comprises a barrier capable of retaining a body of water at a predetermined retaining level with a central barrier wall that is inclined in a direction away from the body of water, a bottom structure beneath the body of water that is capable of delimiting by a weir a bottom chamber filled with air and holding the barrier in its water retaining position by the water pressure exercised on said bottom structure, and an inlet extending beyond the retaining level of the barrier with an upper opening beneath a predetermined flood level that allows water to flood the bottom chamber so as to offset the water pressure on the bottom structure and thereby allow a tipping of the gate, wherein a wall structure forms a wall chamber on the central barrier wall, wherein the wall chamber is capable of being flooded so as to assist the tipping of the gate. Compared to conventional fusegates, such a gate is more stable at all water levels, because it requires the additional overturning moment of the water inside the wall chamber. Therefore, the gate is less likely to accidently tip when heavy objects, e.g. tree trunks, traveling with the current at flood levels between the retaining and the flood level hit the gate.

It is particularly advantageous that the wall chamber of the gate is capable of being flooded in association with the bottom chamber. Thus, the additional overturning moment on the central barrier wall due to the water flooding the wall chamber can be controlled.

Preferably, the gate is capable of tipping when flood water has filled the wall chamber to at least a predetermined level. Depending on the predetermined level, the quantity of water inside the wall chamber necessary for the gate to tip can be set. The higher the quantity of water required is, the more stable the gate is up to the flood level, whereas the lower the quantity of water required is, the faster and more reliably the gate turns.

Further advantageous is that the inlet of the gate is capable of filling the wall chamber and then the bottom chamber. In this way, the necessary additional overturning moment of the water inside the wall chamber is achieved before the bottom chamber is filled, which leads to a faster tipping of the gate once the bottom chamber is filled.

It is particularly advantageous that a partitioning structure of the gate divides the space within the wall structure into the wall chamber and flow-through means leading to the bottom chamber. The main reason for this is to improve the compactness of the gate and integrate this necessary component together with the wall chamber into one easily sealable wall structure.

Preferably, the partitioning structure is a partitioning wall extending upwards inside the wall structure. Such a partitioning wall is sufficient to efficiently delimit a wall chamber inside the wall structure.

Further advantageous is that the wall structure extends from the top of the central barrier wall in a direction towards the bottom chamber. Since the top of the inclined central barrier wall is farthest from the tipping axis of the gate, it is desirable to increase the lever of the flooded wall chamber by placing it at the top of the central barrier wall in order to maximize the achievable overturning moment.

It is further advantageous that the wall structure extends substantially along the entire central barrier wall. Thus, the capacity of the wall chamber can be further maximized, which results in a greater additional overturning moment.

Preferably, the wall chamber extends substantially in parallel to the central barrier wall. Thereby, the direction of the hydrostatic force of the body of water corresponds to the inclination of a conventional gate without the wall chamber.

Further advantageous is that the inlet is integral with the wall structure. Thereby, the inlet can lead water directly to the wall chamber.

Particularly advantageous is that the wall structure is integral with the bottom structure. Such an arrangement renders the gate very compact and also offers the possibility to maximize the capacity of the wall chamber in a downward direction.

Preferably, a top plate of the bottom chamber constitutes a bottom of the wall chamber. Such a close arrangement of bottom and wall chamber benefits the compactness of the gate and at the same time maximizes the capacity of both chambers.

It is further advantageous that the bottom chamber is capable of being filled with water from the wall chamber through a hole in the top plate. The positive effect is that external connecting means leading from one chamber to the other are not necessary.

Particularly advantageous is that the wall chamber has a drain hole that is capable of releasing water in case of rain, spindrift or wave to the bottom chamber or to the outside of the gate away from the body of water. Such a drain hole prevents the wall chamber from being accidentally filled with water and flooded before the actual flood conditions occur.

It is further advantageous that the bottom chamber has a drain hole that is capable of releasing water to the outside of the gate away from the body of water with a significantly lower maximum water throughput than the water throughput for flooding the wall chamber and the bottom chamber, and wherein the section of the drain hole of the wall chamber is smaller than the section of the drain hole of the bottom chamber. The advantage of this is that such a drain hole is big enough to remove water accidentally entered through the inlet, e.g. rain water, and at the same time small enough to not affect the functioning of the gate at flood conditions.

Preferably, a ballast block on top of the bottom structure assists the holding of the barrier in its water retaining position. The ballast block allows the gate to be stably installed on the weir when the body of water is still absent. Also, such ballast blocks can be easily made in different sizes, materials and weights such that each gate depending on the flood level at which it is intended to tip can be balanced precisely by a balance block while the more complex structures of the gate, e.g. the bottom structure, remain basically unchanged.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows an embodiment of the gate in a perspective view.

DESCRIPTION OF THE EMBODIMENT

FIG. 1 shows a steel gate 1 on a flat free spillway weir 2 in an upright, water retaining position. The gate 1 has, as a main component, a barrier 3 with an U-shape being open towards a body of water W and extending upwards to a predetermined retaining level RL. The barrier 3 is formed by a central barrier wall 4 that is inclined in a direction away from the body of water W and two side barrier walls 5, 6 that are perpendicular to the weir 2. Toe abutments 100 are fixedly connected to the weir 2 and abut against the central barrier wall 4 on its side facing away from the body of water W.

A bottom structure 7 is located within the barrier 3 at a lower portion of the gate 1 and close to the weir 2. The bottom structure 7 has: a top plate 9 that extends in parallel to the weir 2 and along the barrier 3; and a back plate 10 that extends from the free end of the top plate 9 along the free ends of the side barrier walls 5, 6 to the weir 2. A ballast block 11 is placed on top of the top plate 9 at its free end. The bottom structure 7 is watertightly welded to the barrier 3 such that it delimits a bottom chamber 8 by the weir 2 and the barrier 3. The bottom chamber 8 has two holes 20, 22: a drain hole 22 cut out in the bottom of the central barrier wall 4; and a hole 20 in the top plate 9 close to the central barrier wall 4.

A wall structure 12 extends from the top plate 9 of the bottom structure along the central barrier wall 4. The wall structure 12 has: a wall plate 15 that extends from the top plate 9 upwards between the side barrier walls 5, 6 and substantially in parallel to and along the entire central barrier wall 4 to the top edge of the central barrier wall 4; and a partitioning wall 16 that extends from the top plate 9 upwards between the central barrier wall 4 and the wall plate 15 and in parallel to the side barrier walls 5, 6 to a predetermined height. The wall structure 12 is watertightly welded to the top plate 9, the side barrier walls 5, 6 and the upper edge of the central barrier wall 4. The partitioning wall 16 is displaced towards the one side barrier wall 5 and divides the space inside the wall structure 12 into a bigger wall chamber 13 and a smaller flow-through shaft 14. The wall chamber 13 and the flow-through shaft 14 are connected through a bigger opening between the upper edge of the partitioning wall 16 and the wall plate 15 and a smaller drain hole 21 cut-out in the bottom of the partitioning wall 16. The hole 20 in the top plate 9 leads to the flow-through shaft 14 and thereby connects the wall chamber 13 and the bottom chamber 8.

An inlet 17 extends upwards from the top of the wall structure 12 and symmetrically to the side barrier walls 5, 6. The inlet 17 is welded to the wall plate 15 and has an upper opening 18 beneath a predetermined flood level FL and a lower opening 19 leading through the wall plate 15 to the wall chamber 13.

The operation of the gate of the first embodiment is as follows:

When the level of the body of water W is below a flood level FL, the gate 1 shown in FIG. 1 is in the upright position. In this position, the water pressure of the body of water W exercised on the bottom structure 7 is enough to press the bottom structure 7 against the weir 2 and thereby hold the gate 1 in its upright position. As soon as the body of water has reached the predetermined flood level FL, water enters through the upper opening 18 of the inlet 17 and fills through the lower opening 19 of the inlet 17 the wall chamber 13. When the water inside the wall chamber 13 has reached the predetermined height of the partitioning wall 16, it overflows the upper edge of the partitioning wall 16 and flows through the flow-through shaft 14 and the hole 20 in the top plate 9 into the bottom chamber 8. As the bottom chamber 8 is filled, the water pressure on the bottom structure 7 holding the gate 1 is being offset. Thus, the hydrostatic pressure of the body of water W acting on the wall plate 15 and the additional overturning moment of the filled wall chamber 13 cause the gate 1 to tip over the toe abutments 100.

Claims

1. A gate for free spillway weirs, comprising:

a barrier capable of retaining a body of water at a predetermined retaining level with a central barrier wall that is inclined in a direction away from the body of water;

a bottom structure beneath the body of water that is capable of delimiting by a weir a bottom chamber filled with air and holding the barrier in its water retaining position by the water pressure exercised on said bottom structure; and

an inlet extending beyond the retaining level of the barrier with an upper opening beneath a predetermined flood level that allows water to flood the bottom chamber so as to offset the water pressure on the bottom structure and thereby allow a tipping of the gate; a and a wall structure forming a wall chamber on the central barrier wall, wherein the wall chamber is capable of being flooded so as to assist the tipping of the gate

wherein the inlet is integral with the wall structure and leading directly to the wall chamber.

2. A gate according to claim 1, wherein the wall chamber is capable of being flooded in association with the bottom chamber.

3. A gate according to claim 1, wherein the gate is capable of tipping when flood water has filled the wall chamber to at least a predetermined level.

4. A gate according to claim 1, wherein the inlet is capable of filling the wall chamber and then the bottom chamber.

5. A gate according to claim 1, wherein a partitioning structure divides the space within the wall structure into the wall chamber and flow-through means leading to the bottom chamber.

6. A gate according to claim 5, wherein the partitioning structure is a partitioning wall extending upwards inside the wall structure.

7. A gate according to claim 1, wherein the wall structure extends from the top of the central barrier wall in a direction towards the bottom chamber.

8. A gate according to claim 1, wherein the wall structure extends substantially along the entire central barrier wall.

9. A gate according to claim 1, wherein the wall chamber extends substantially in parallel to the central barrier wall.

10. A gate according to claim 1, wherein the inlet is integral with the wall structure.

11. A gate according to claim 1, wherein the wall structure is integral with the bottom structure.

12. A gate according to claim 11, wherein a top plate of the bottom chamber constitutes a bottom of the wall chamber.

13. A gate according to claim 12, wherein the bottom chamber is capable of being filled with water from the wall chamber through a hole in the top plate.

14. A gate according to claim 1, wherein the wall chamber has a drain hole that is capable of releasing water in case of rain, spindrift or wave.

15. A gate according to claim 14, wherein the bottom chamber has a drain hole that is capable of releasing water to the outside of the gate away from the body of water with a significantly lower maximum water throughput than the water throughput for flooding the wall chamber and the bottom chamber, and wherein the section of the drain hole of the wall chamber is smaller than the section of the drain hole of the bottom chamber.