Hydraulic and earth engineering – Marine structure or fabrication thereof – In or on frozen media
Reexamination Certificate
2002-12-12
2004-03-30
Lagman, Frederick L. (Department: 3673)
Hydraulic and earth engineering
Marine structure or fabrication thereof
In or on frozen media
C405S195100
Reexamination Certificate
active
06712558
ABSTRACT:
TECHNICAL FIELD
This invention relates to ice composite bodies for use in the construction of fixed or floating structures located in or on water. The invention also relates to a process for the construction of such ice composite bodies.
BACKGROUND ART
Ice composite bodies can be used in warm or cool waters for applications such as bridges, breakwaters, causeways, pontoons, artificial islands, dams, tidal barrages, wave power barrages, harbour walls, wind power farms or aircraft runways.
GB-A 2 071 295 discloses a method of producing a gravity ice platform, made in a floating flexible mould from a spray of ice flakes or chips, which are frozen in solid ice by using supercooled water, cold air or a freezing mixture. The resultant large blocks of ice can be used on their own or a number of the blocks may be joined together to form a desired structure. Because of the large volumes of ice involved these structures will sit stably on the waterbed and are capable of withstanding any forces to which they may be subjected, such as from waves, wind currents or collisions.
A problem with structures of this kind is that the ice will tend to creep when subjected to heavy loading. The method of producing the ice structures will also result in large quantities of dissolved gas and also liquid inclusions being trapped in the ice. This will cause the ice to be unstable under stress.
WO 97/25483 discloses an ice composite body having an inner ice core covered by a protective outer armour layer with means for thermally insulating the ice core therebetween. The ice core is frozen and maintained in the frozen state by means of a system of refrigeration pipes located within the body. The ice composite body provides structures of equal or greater strength than equivalent structures using conventional materials, at a significantly lower cost. However, the strength of the ice composite body is limited by the structure of the outer armour shell. A load acting at a point on the upper surface of the armour shell will tend to cause the surface to bend causing stress in the body.
It is an object of the present invention to provide an ice composite body in which the above cited disadvantages are reduced or eliminated. It is also an object of the present invention to provide a process for the construction of an ice composite body, which will produce an ice composite body having predictable load bearing characteristics.
DISCLOSURE OF INVENTION
Thus, according to the present invention there is provided an ice composite body for use in the construction of fixed or floating structures located in or on water, the body comprising an inner ice constrained core, a protective outer armour shell having side sections and a separate top section, the top section resting freely between the side sections on the ice core in use and being free to move vertically in use, such that any load acting on the top section will be evenly distributed through the body, means for thermally insulating the ice core and means for maintaining the ice core in a frozen condition in use.
As the inner ice core is constrained within the outer armour shell and as the top section rests on the ice core, the ice core is only stressed in compression. This results in an increase in safe design strength relative to known ice composite bodies.
Preferably, the protective outer armour shell has an inner wall and an outer wall with a space therebetween, the space providing the means for thermally insulating the ice core.
Further, preferably, the space is filled with foam insulating material.
The space between the walls provides a degree of insulation on its own but may also be filled with insulating material.
In certain embodiments, strengthening ribs are located at intervals between the inner and outer walls.
The orientation of the strengthening ribs can be chosen depending on the particular application for which the ice composite body is to be used. Thus, where the application is for a road bridge or aircraft runway the strengthening ribs can be orientated along the length of the bridge or runway so as to be located under the wheel track of the vehicles in use, with suitable lateral stiffeners placed between the ribs.
Preferably, the protective outer armour shell has a base section, side sections, and the top section is located between the side sections and is free to move therebetween.
Thus, the top section rests freely on the ice core in use and is free to move in a vertical direction between the side sections while being retained therebetween. The side sections do not bear any of the weight of the top section.
Further, preferably, one of the side sections further comprises a separate closure section removably located on the upper edge thereof, the closure section being located on the side section in use once the top section is in position.
The removable closure section facilitates the construction of the ice composite body. Thus, the top section can be positioned on the inner ice core with the closure section being put in place on the upper edge of the side section thereafter. The top section is then retained between the two side sections.
Suitably, the space between the top section and the side sections contains a filler material, which prevents any of the core ice from entering the space in use.
The filler provides lateral support and also ensures that the top section always exerts its weight vertically on the ice core top.
Preferably, the filler material is an elastomer or an elastomer-modified bitumen.
To ensure that the top section will always exert its weight vertically on the ice core, the filler material should be chosen from materials such as an elastomer or elastomer-modified bitumen with slightly higher strain in shear at the operating conditions of the ice composite body than the compression strain of the ice under the top section loading and having good adhesion to the armour material chosen.
The filler material is also chosen with reference to the width and vertical dimension of the space between the top section and the side sections, so that the adhesion of the filler to and yield shear stress along the armour used, multiplied by the vertical dimension of the space, is greater than the normal compressive loading on the ice in use.
Further, preferably, a stuffing gasket is located at the upper end of the space between the top section and the side sections to limit the loss of filler therefrom.
In use, the stuffing gasket will be depressed into the space by applied pressure or surface traffic pressure, in order to minimise the expression rate of the filler.
Suitably, the ice composite body is provided with means for replacing any filler lost from the space.
Thus, replacement filler can be pumped into the space at a pressure equal to the compression stress on the top of the ice so as to prevent ice from entering into the space and to ensure that the space is always full of filler.
Preferably, the protective outer armour layer is made of concrete material.
Concrete has been found to be a suitable material for structures constantly immersed in water and provides a life span for the ice composite body of over seventy years when suitably constructed.
Preferably, the inner ice core is formed in layers, each layer having been rolled using a roller apparatus which provides a roller pressure in the range of 3.5 to 8 Newtons/mm
2
following formation thereof.
The rolling is carried out in order to orient the strongest axes of the ice crystals of the ice formed in the desired direction. The roller apparatus should exert a compressive pressure above that of the weak ice crystals and below that of the strong ice crystals, typically a roller pressure in the range 3.5-8 Newtons/mm
2
, with the choice of roller pressure being determined by the particular core strength desired by the designer. This rolling process converts the crystal structure in each ice layer into one with the required mix of strong crystals of known orientation and compressive strength. The rolling of the ice layers in this way also ensures that any average load applied to the top s
Fulbright & Jaworski L.L.P.
Lagman Frederick L.
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