| GBi final s 7 WO 2011/121273 PCT/GB2011/000391 3 Claims 1. A flood protection structure comprising a barrier hingedly connected along its lower edge to a foundation, wherein the barrier has a buoyancy chamber which causes the barrier to have a neutral buoyancy when immersed in water, and a balance mechanism which allows the position of the centre of gravity of the barrier to be moved relative to its centre of buoyancy both towards the hinged lower edge and towards a distal end opposite to me hinged lower edge; wherein the barrier is raised from a lowered at rest position to a raised in use position by moving the centre of gravity of the barrier towards the Hinged lower edge, such that the distal end raises as the water level increases to an in use position where the barrier is maintained by the increased water level; the barrier is lowered by moving the balance mechanism in a second direction opposite to the first direction towards the distal end, thereby moving the centre of gravity closer to the distal end, so that the barrier descends to a lowered at rest position below the water surface. |
Description
A barrier for protection against flooding, incorporating the following pair of essential features which, operating together, enable it by rotation about its lower bottom edge to be lowered to, and rest upon the surface beneath a body of water while the surface of the water above is at a safe level, and to be raised to a position so as to retain the water on one side of it at a safe level while retaining water on its other side to a higher level:
A - a buoyancy chamber the internal volume of which is such that the weight of the barrier is equal to the weight of the volume of water displaced by it when fully immersed, and the position of which within the barrier is such that its centre of buoyancy is above and towards the upper crest of the barrier relative to its centre of mass, excluding any mass of the barrier' s 'balancing mechanism' movable relatively to that mass centre, and:
B - a balancing mechanism enabling the centre of gravity of the barrier as a whole to be moved towards or away from the barrier's crest across the vertical through the centre of buoyancy to provide a turning moment either to lower, or raise the barrier.
The operation and operating principle of the barrier are illustrated in figure one, attached.
The totally immersed barrier, having a density the same as that of the liquid in which it is immersed, floats 'weightlessly' within the liquid, its 'free' attitude being determined by its centre of buoyancy being vertically above its centre of gravity. For erection, or maintenance, it is, therefore, very light, easy to move, manoeuvre and manipulate, and imposes almost no load upon its foundation, or, when lowered, upon the bed material.
When hinged to any suitable structural foundation along it lower bottom edge, its required attitude is achieved by appropriate adjustment of the 'balancing' mechanism. When lowered, it thus rests only lightly upon the 'bed' , or 'floor' of the body of liquid in which it is immersed. Similarly, at the hinge very little resistance to rotation should be encountered during raising or lowering.
When functioning as a barrier against flooding, the flood wave, or tidal surge, itself, provides both the horizontal force and moment required to maintain the barrier in the raised position, provided that in the fully raised position it is inclined towards the wave, or surge. The barrier acts as a cantilever, transferring only the differential hydrostatic force and moment directly to the foundation as internal transverse shear, longitudinal compression and bending moment. The resulting pressure of the base of the barrier upon the inclined face of the foundation provides an effective seal.
As the flood or surge subsides, the barrier accordingly rotates to float with its crest just submerged when the water levels either side equate. Lowering the barrier to rest upon the 'bed', or 'floor' is achieved by appropriate mechanical adjustment of the balancing mechanism.
The barrier may be of any structural material possessing the necessary strength in
compression, shear and flexure at safe working stresses, resistance to fatigue, and to corrosion, whether inherently, by surface treatment, or application of a surface coating, having due regard to durability, environmental and other economic considerations. The structural section may be any allowing of the two essential features of buoyancy chamber and balancing mechanism, having a section modulus such that all stresses within the material shall comply with applicable safe limits, having regard to economic factors of quantities of material, simplicity, speed and ease of manufacture, fabrication, assembly and installation, as also any environmental, or aesthetic restraints that might be imposed.
Alternative forms of balancing mechanism to that illustrated schematically, namely, an encased, motorised weight mounted on a shaft, its position along the shaft adjustable by 'worm gearing', 'pulleys and wires', or other suitable mechanical means, are possible. Some possible alternatives are:
an auxiliary buoyancy chamber at the upper, crest end of the barrier, in balance when partially filled, and alternately exhausted or flooded to raise or lower the barrier;
the essential buoyancy chamber, itself, may be mounted so as to be movable along the central
'axis' of the barrier to move the centre of buoyancy across the centre of gravity;
small auxiliary buoyancy chambers of equal volume at each end of the essential chamber both half filled with a suitably non-corrosive liquid when in balance, all their combined content being alternately transferred to the lower, or upper chamber to raise, or lower the barrier.
Important objectives of the operating principle described are, firstly, to rninimise the energy and power needed to raise and lower the barrier, and secondly, to ensure that the barrier remains fully raised and effective for the duration of a flood, or surge, without need of external support or intervention should some failure, malfunction, or other suchlike emergency occur, as the barrier, once raised, is supported by the flood, or surge, itself.