This invention relates to an armour block for breakwater and coastal protection. Breakwater resist wave action to create tranquil conditions inside a harbour basin. Sea walls protect the coast against erosion.
Coastal erosion is a common and wide spread natural phenomenon in coastal stretches due to relentless action of waves. Armour blocks are used to protect a structure form the attack of waves. An important feature of these annour units are that they inter-lock with each other to provide an integral, but flexible resisting body to resist wave action. The main principle of the armour block is to dissipate the energy of the impinging waves without having to withstand the full wave force.
A large number of armour blocks have been developed during the last century. The success of the armour block depends on the wave dissipating capacity of the unit. Researchers are at work all over the world to develop more efficient armour units.
The object of this invention is to develop an annour block for effectively combating the wave force acting thereon.
Armour blocks developed by this invention is useful for harbour engineering. Harbours, as the word indicates, are to create harboured or calm waters. The most important harbour structure is the breakwater. Breakwaters are constructed in the sea to resist the energy of the oncoming waves, so that the waters in the basin in the lee of the structure will be tranquil. The harbour basin could then be utilized Tor handling of ocean going vessels for loading/unloading of cargo. But on the other hand, breakwaters should be able to resist the waves without undergoing distress themselves. The usual type of structure for a breakwater is called rubble mound. This is in the shape of a trapezium. The inner layers of the trapezium are made up of rock stones of

various sizes. The size of the stones will increase towards the outer periphery. Predominant wave action will be on the side slope facing the sea. The stones on this side will be protected by concrete armour blocks. The blocks will be subjected to relentless onslaught of waves. The dynamic force imparted by a wave on an object is very high. Besides, waves impinge on the structure once in every ten seconds or so. In this environment, any kind of blocks placed on the side slopes can hardly be stable. So, wave energy has to be dissipated. The methodology adopted is to pulverize the wave energy and send it in various directions. Based on this principle, during the last few decades, various shapes of armour blocks have been developed. Efficiency of the block is generally characterized by its Hudson's stability number or KQ value. The invention relates to a new type of armour block. Studies to establish its stability number for various parameters have been completed in a wave flume. According to these results, the Kd value of the block is very high. The block also has excellent interlocking characteristics, which means that each block does not act individually but are locked together due to the advantage of its shape. Hudson's formula is used world wide for finding out the weight of the armour block required. For the same wave height and side slope, the weight of the armour block is decided by Hudson's formula. The higher the Kd value, the lower will be weight of the armour block required. This armour block according to the present invention will reduce the size of the armour blocks in breakwaters considerably.
This invention relates to an armour block for breakwater and coastal protection, comprising a central member and two mutually perpendicular members on the extremes of said central member, all said members being octogonal in cross section, each of said perpendicular members being tapered towards their respective ends.
These blocks may be made of concrete or any other water impermeable and water resistant material. The three dimensional shape of the armour blocks

according to this invention provides high interiocking characteristics and makes the block resistant to dislodgement during wave action.
This invention will now be described with reference to the figures shown in the accompanying drawings.
Figure I shows the armour block according to this invention.
Figures 2 to 4 are different views of the armour block from three different directions.
According to figures 1 to 4, M, and M2 are the mutually perpendicular members on either end of the central member C. The cross section of all the members is hexagonal and the taper at M| and M2 are indicated generally by the letter T. Dimensions marked in the drawings are only illustrations. The basic overall dimension is C and the other dimensions are features thereof which are given in the following table;


The fractions are given in the accompanying table. The outcome of the Hudson's formula is the weight of the armour block. Volume can be arrived at by dividing the weight by the density of concrete. The expression for the volume in terms of the overall dimension C is also given in the table. Factors like layer coefficient and porosity have also been given. This is required for arriving at the packing density and the thickness of the layer. In effect, the armour block consists of two masses perpendicular to each other, connected together by a member.
Obvious alterations and modifications known to persons skilled in the art are not excluded from the scope and ambit of the above invention and the appended claims.

WE CLAIM:
1. An armour block for breakwater and coastal protection, comprising a
central member and two mutually perpendicular members on extremes of
said central member all said members being octagonal in cross section, each of
said perpendicular member being tapered towards their respective ends.
2. The armour block as claimed in claim 1, wherein said armour block is
made of concrete or the like water and pressure resistant material.
3. The armour block as claimed in claims 1 and 2, which interlocks with each other.
4. An armour block for breakwater and coastal protection substantially as herein described with reference to the accompanying drawings.