Hydraulic and earth engineering – Bank – shore – or bed protection – Wave or flow dissipation
Patent
1991-01-17
1992-01-14
Taylor, Dennis L.
Hydraulic and earth engineering
Bank, shore, or bed protection
Wave or flow dissipation
405 16, 405 25, 405 30, E02B 304, E02B 306
Patent
active
050805266
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to erosion protection structures primarily for use in artificial barrier reefs to provide sheltered harbours.
Artificial barrier reefs are in use in many areas and they are typically made up of a plurality of erosion protection units collected together to form a mass. The erosion protection units are typically solid concrete members. Many different shapes of erosion protection units are produced but the most common shapes used are tetrapods and quadrapods which are illustrated in FIG. 1 of the accompanying drawings.
Tetrahedral solid blocks and hollow tetrahedral blocks are also produced. However, neither of these designs has proved as popular and effective as tetrapods or quadrapods.
SUMMARY OF THE INVENTION
According to the invention there is provided an erosion protection unit, comprising a tetrahedral frame comprising six outer elongate members arranged in the outline of a tetrahedron, and a triaxial central strut arrangement comprising of three struts arranged mutually perpendicular to one another and passing through the geometric centre of the tetrahedron, such that each outer member is braced by a strut passing from its centre to the centre of a second opposite outer member.
Preferably the structure is a regular tetrahedron such that each face of the tetrahedral frame describes an equilateral triangle.
The erosion protection unit can be installed singly or in multipals in a regular packed formation, with open spacing, or preferably in a random interrelationship. The application includes the formation of artificial barrier reefs, retention of land slip, flow retarding and diverting barriers, deadman anchorage, support stools, erosion shielding and blast shielding.
The tetrahedral arrangement is extremely effective at resisting displacement by force applied at any point and ensures that the structure functions equally effectively regardless of its orientation.
Because the unit is not a solid unit but is a frame, when the units are randomly arranged, the units often interlock to increase the normal high level of self stability of the individual units.
Moreover, because the structure is a frame structure, but has great stability, the unit can give greater stability than a solid unit of the same mass. Moreover, the central strut arrangement increases the wave energy dissipation of the unit to give a much stronger structure than the simple hollow tetrahedron.
The central triaxial bracing lying with mutually perpendicular axes provides a very stable arrangement which relieves stress within the outer members.
The reduction in sectional area of the units as a result of the centre bracing results in approximately 50% material and weight saving compared with tetrapods and quadrapods in artificial barrier reef collection.
Preferably the frame is made of a settable composition which is more preferably concrete. Preferably the centre strut arrangement is integrally mounted with the six outer frame members.
It is possible for a single unit to be cast in concrete using four identical mould sections. In order to do this, preferably the six outer members are substantially circular in cross-section but not completely circular in cross-section to allow for mould simplicity and demoulding convenience.
In this way the mould can be made up of four identical sections one of which would form the base and the other three forming the sides of the unit.
Such a mould structure allows a unit to be cast through one opening at the apex and would be entirely self-venting.
BRIEF DESCRIPTION OF THE DRAWINGS
Examples of an erosion protection unit and a mould to make it will now be described and contrasted with the prior art, with reference to the accompanying drawings, in which:
FIG. 1 is a schematic perspective view of a selection of erosion protection units of the prior art;
FIG. 2 is a perspective view of an erosion protection structure in accordance with the invention;
FIGS. 3A and 3B depict the axial relationship of the frame work of the unit;
FIG. 4 is a schematic perspective v
REFERENCES:
patent: 1875668 (1932-09-01), Sheldon
patent: 2835112 (1958-05-01), Monnet
patent: 2844005 (1958-07-01), Rehfeld
patent: 3204721 (1965-09-01), Park
patent: 3380253 (1968-04-01), Vita
patent: 3417533 (1968-12-01), Sparling
patent: 3974611 (1976-08-01), Satterthwaite
patent: 4431337 (1984-02-01), Iwasa
patent: 4711057 (1987-12-01), Lew et al.
Dunlop Limited
Ricci John A.
Taylor Dennis L.
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