Earth retaining embankment wall building blocks are widely used for stacking upon and against an earth embankment to prevent shifting of soil and/or soil erosion, especially on steep slopes and particularly in built-up areas where there is a danger of soil or rock falling onto roads or pedestrian pavements. Known types of earth-retaining embankment wall building blocks are not designed to be both interlocking, so as to prevent horizontal shifting of the blocks away from the plane of the slope, and adaptable, to suit the slope angle. This is undesirable since, unless the blocks are locked by external means such as mortar, it may happen that, especially during heavy rainfall, the embankment protection structure shifts horizontally. This will cause the structure to be damaged, and even destroyed in extreme cases.

It is an object of the invention to provide an embankment wall building block that at least minimizes the disadvantages of the known types of blocks.

According to the invention, a building block includes front and rear end faces, as well as upper, lower and side faces, the arrangement being characterised in that the lower face includes a step formation for locating behind the rear end face of a lower block in use.

In most practical embodiments the step will be located towards the rear end face of the block. Furthermore, the building block is preferably hollow between the upper and lower faces thereof.

With this arrangement, an embankment retaining wall structure can be constructed by forming a first row of blocks according to the invention by placing the blocks side by side at the base of the earth embankment, and with their rear end faces abutting against it, forming a second row of blocks on top of the first row so that the step formation of the blocks of the second row locate and lock behind the rear end faces of the blocks of the first row and so that their rear end faces also abut against the earth embankment, and repeating the above procedure. This will prevent the rows of blocks from shifting horizontally away from the slope because the blocks of each row are anchored by their step formations on the blocks of the row upon which they are located.

It will be appreciated that, with the above block configuration, superimposed blocks will overlap rearwardly with the blocks beneath them, and the wall structure will be sloped step-wise, the slope angle being dependent on the amount of overlap which is governed by the length of the step from the rear of a block to the front of the step. It will also be appreciated that any required embankment slope angle can be catered for, simply by manufacturing the blocks with longer or shorter steps to obtain the predetermined slope angle. This is easily achieved by utilizing a mould for the blocks which is equipped with a removable filler piece which gives rise to the formation of the step. By using a filler piece of suitable dimensions the step is formed with appropriate dimensions to achieve the required overlap and slope.

The rear end face is preferably straight and, in use, is located hard up against the face of the earth embankment. Preferably also, the one side face is generally concavely shaped and the opposite side face generally convexly shaped complementally with the concave so as to fit snugly in the concave face of its neighbour.

The above configuration will allow contiguous blocks to mate in an inter-engaging fashion serving further to strengthen the structure. What is more, the inter-engaging concave and convex sides operate in the nature of a ball and socket joint permitting an embankment retaining wall built from the blocks of the invention to take up lateral undulations in the embankment itself.

The front and face may be curved and the curve is preferably defined by a series of facets that give the front face of an embankment retaining structure a distinctive appearance.

Alternative, the side walls and/or front end wall may be wave-like, the side wall of a block being shaped to inter-engage with the adjacent wall of its neighbour.

In use, the cavities defined in the hollow blocks of a finished retaining wall structure may be filled with soil and planted to enhance the appearance of the embankment retaining wall.

All of the above is already recorded in foreign patent no 91/8410 registered in the Republic of South Africa. However, it is the object of this invention to overcome the disadvantages and satisfy the needs expressed or implicit in the above general disclosure without losing anything.

The essence of the new invention is the v-shaped connecting wall that runs between the two sidewalls of the block. This divides the block effectively into two parts: approximately one third in the anterior of the block and two thirds in the posterior of the block. By making both the connecting wall, as well as the anterior parts of the block that don't carry any weight from the superimposed blocks, thinner, the actual weight of the block has been kept to that which can be handled by one individual. This has obvious cost savings.

The shape of this connecting v-shaped wall is designed to give maximum plantable space when the superimposed row of blocks is built in a staggered sequence. It is obvious that this invention caters for and, in fact, envisages any number of different shaped connecting walls.

The fact that this connecting wall exists, allows a hollow block to be moulded that is substantially wider in circumference without being subject to breakage when handled. A wider block allows for more retaining ability without a corresponding cost increase.

It is further an aspect of this invention that the anterior compartment of the block can be filled with topsoil or any other growing medium so that the finished wall can be fully planted and over grown. The posterior compartment can therefore be filled with a low cost filling material without the block losing either its retaining ability or its plantability.

It is a further object of this invention that the posterior compartment of this block can be filled"in situ"with a portable concrete mix, with or without steel reinforcing, binding several rows of blocks together. This will greatly enhance the structural strength of the wall being built, while at the same time allowing the anterior face of the wall to be planted. Thus greening what is essentially a solid concrete wall.

This invention also allows these blocks to protect riverbanks and canals from erosion and wash-out. The connecting wall effectively cuts off the posterior compartment from any contact with the water. It becomes easy and cost effective to seal off the anterior compartment from water damage using any number of methods, like sealing it with concrete or similar or even using rough stones in that compartment, whilst still using a cheap filler in the anterior compartment. This application will result in substantial cost savings over conventional methods of riverine and canal protection. It is an easy self-guiding system that requires semi-skilled labour and cost effective filling agents.

It is readily conceived that geo-fabric earth-strengthening materials be used to further enhance the stability or strength of walls built with these blocks. The nature of the step-back located on the side walls of this invention allows geo-fabric to be placed in an overlaying way so that the weight of the superimposed block, plus its infill, press down and create an indenture in the fabric which allows it to be locked into place.