Along the shores of lakes and reservoirs and especially along the banks of rivers different water protection structures are built to ensure flood control and to prevent floods. A group of such water protection structures is formed by dams which are built so that by collecting a large amount of clay soil and by compacting the soil suiting the soil's natural angle of incline, an earthwork of a large mass is made, and in a given case its side facing the mass of water intended to be controlled is covered with a material, e. g. stones, which resists the physical effect of the water better.

A process relating to the establishment of such water protection structures made of earth is described in patent No. HU 185.833, in which the basic body is compacted soil, and in order to increase its solidity its external surface is covered with a consolidating stabilising material.

Patent No. HU P 96 02852 describes a process that can be used to renovate flood-control dams, and according to this the worn and damaged external surface of the earthwork is replaced, and on the place of the removed layer a new, more stable external covering is made.

However, the disadvantage of the dams made or renewed with the known procedure is that clay soil becomes desiccated after a time, plants start to grow in it and their roots penetrate inside the water protection structure, animals dig holes in the earth forming the dam, and in this way, as. time passes, the water protection structure loses some of its protective ability. As a result of erosion and the flora and fauna, holes are created in the dam, and in the case of a greater water load these holes let water through towards the protected side, and due to this the dam cannot perform its function any more, in a more serious case it may even fall in which may result in a catastrophe.

A further disadvantage is that in the case of traditionally built or renovated dams the building and the reparations require significant labour, and the period of building is also limited as it largely depends on the weather.

Our aim with the procedure according to the invention is to overcome the deficiencies of the known solutions and to create a solution which makes it possible to build water protection structures in a simpler way, while the load capacity, reliability and lifetime of the finished structure is also increased as compared to dams built in the traditional way.

The procedure according to the invention is based on the recognition that if clay is mixed with an appropriate amount of powdered metal, when it meets water it goes through a specific chemical transformation in the course of which the clay mixed with powdered metal becomes cemented and it forms a hard layer which cannot be penetrated by liquids. If this mixture is put into the gaps between suitably selected stones, then the stones and the clay mixed with powdered metal change into one single continuous block which has more favourable characteristics both from the aspects of solidity and waterproofing than the material combinations used in the traditional procedures, and so the task can be solved.

In accordance with the set aim the procedure for building water protection structures according to the invention, in the course of which a basic body is formed from stones, and at least two sides of the basic body are provided with a covering layer, is based on the principle that a filling material is made from a mixture of clay and metal filings, where the mass proportion of clay and metal filings is set between 18: 1 and 22: 1, and in the course of making the basic body the filling material is put into the free gaps between the stones forming the basic body, and only after this is the basic body provided with a covering layer.

A further criterion of the procedure according to the invention may be that iron powder is used as powdered metal for making the filling material.

In the case of a favourable realisation of the procedure, in the course of making the basic body, the sides of the basic body are surrounded at least partly with wire gauze, preferably iron gauze free from surface protection.

In the case of another different version of the procedure, a polyvinyl derivative, as a space- filling and water-adsorbing additive, is put into the space surrounded by the basic body, unevenly distributed.

The advantage of the procedure according to the invention is that due to its application the building of water protection structures becomes simpler, and the finished dams have more favourable characteristics both from the aspects of waterproofing and other aspects of solidity as compared to the traditional solutions.

It must also be regarded as an advantage that due to the basic body construction different from the known constructions, the lifetime of the water protection structures is also extended, and their maintenance and renovation also requires less labour.

It is also favourable that in the case of using a basic body sunk to the appropriate depth, that is underneath the ground sill, filtration deriving from the water pressure occurring when the water level raises critically and from the soaking of the dam, and so the safety of water protection structures is also significantly increased.

The solution according to the invention is described in detail in connection with a drawing and a procedure example. In the drawing Figure 1 is the sectional picture of a version of the water protection structure.

Figure 1 shows a water protection structure situated along the bank 51 of a river 50. It can be seen that the basic body 10 starts underneath the ground sill 52 of the river 50, and it lasts all the way until the crest 14. The basic body 10 is formed by stones 11 and filling material 20 in the free gaps 12 between the stones 11. Here the filling material 20 is a mixture of clay and iron powder in a proportion of 20: 1. However, it must be pointed out that not only iron powder can be used as metal filings, and that the grain size of the filings can be between quite wide limits. In the case of this version of the invention the filling material is supplemented with a space-filling and water-adsorbing additive 21 made of a polyvinyl derivative, and its task is to adsorb the water remaining after the cementation of the filling material 20 of the basic body 10.

Figure 1 also shows that the sides 13 of the basic body 10 are surrounded with wire gauze 40 which, on the one part, increases the rigidity of the basic body 10 and helps to maintain its shape until the cementation of the basic body 10 takes place due to the filling material 20.

On the other part, the wire gauze, which in our case is iron gauze free from surface protection, also aids the cementation of the filling material 20. In the case of the present version the basic body 10 is covered with a covering layer 30 on the sides 13 and the crest 14, and this covering layer 30 is a soil layer compacted with the traditional procedure.

Below the procedure according to the invention is described in more detail in connection with examples.

Example 1: A water protection structure was built along a river 50 in a way that along the bank 51 of the river 50, starting from a depth underneath the ground sill 52, stones 11 were put down, and the free gaps 12 between them were filled layer after layer with a filling material consisting of clay and metal filings. The filling material 20 was made on the scene with a traditional concrete mixer.

When the basic body 10 was built up to the required crest 14 height, two sides 13 of the basic body 10 and the crest 14 were provided with a covering layer 30 of soil compacted with the traditional technology. After putting down the covering layer 30, as the water in the wet soil was moving, the water and the precipitation got in contact with the filling material 20, the iron powder was oxidised, and as a result of this the filing material 20 underwent a change in the course of which the stones were linked to each other, cementation took place, and due to this an impermeable layer was created in the free gaps 12 between the stones 11.

The cementation took place in 180 days, but the required time also depends on the size of the basic body 10 and the amount of liquid entering it.

Example 2: A procedure was used similar to the one above, but after the basic body 10 was built, its sides 13 were covered with wire gauze 40, and only after this was the covering layer 30 placed on the sides 13 and the crest 14 of the basic body 10.

In this case, too, a cemented layer formed on the sides 13 of the basic body 10, which improved the impermeability, mechanical solidity and stability of the water protection structure.

The procedure according to the invention can be used favourably both for building and renovating water protection structures for different purposes, such as flood-control dams.

List of references 10 basic body 11 stones 12 free gaps 13 side 14 crest 20 filling material 21 space-filling and water-adsorbing additive 30 covering layer 40 wire gauze 50 river 51 bank 52 ground sill