EP0339010A1 - Method for creating an artificial beach or for raising an existing beach - Google Patents

Abstract

The invention relates to a method for making an artificial beach by refilling with sand or for raising an existing beach in a river or by the sea, characterised in that there is formed on the river bottom, in this case an artificially dredged bottom, a submerged dyke (2) based on materials which are proof against slipping along the slope of the original bottom of the river or sea, and in that the sand necessary for forming said beach is introduced by refilling between this submerged dyke and the land to the desired height and at the desired slope. <IMAGE>

Description

This invention relates to a method of making an artificial beach by backfilling with sand or raising an existing beach in a river, a mouth of a river or the sea, the original inclination of the ground is too large to hold back the backfilled sand.

When an artificial beach is to be built along a river or a river mouth, problems arise, especially when the river or the mouth of the river is subject to tides, which are directly related to the flow from the base of the new or artificial beach in the river channel or in the sea.

Up to now, existing beaches have been raised almost exclusively by backfilling with fresh sand. The results are always disappointing in the relatively short term, since a large quantity of freshly backfilled sand inevitably disappears again in the sea or in the channel. Sand filling must therefore be repeated several times, which can pose an insurmountable problem financially.

When considering the construction of an artificial beach in a river, the backfilled fresh sand cannot in any case again flow towards the channel. This will happen all the more quickly as the inclination of the bottom along the edge of the river forms an angle where the backfilled sand will flow from this slope.

The invention now aims to provide a method which provides a new and original solution to the problems posed and by which artificial beaches having a small inclination can be built, both at sea and along an edge. of a river.

In order to allow this according to the invention, a submerged dike is built on the bottom of the river or the sea, this dike submerged from materials which are proof against sliding along the inclination of the original soil of the river or the sea and, for the formation of said beach, the necessary sand is applied between this submerged dam and the earth to the desired height and until the desired inclination is reached.

Still according to the invention and when the river or the sea is subject to tides, the top of said submerged dam is established practically at the height of the average low tide.

The fact is remarkable for the invention that the above-mentioned submerged dam is produced using geotextiles of which at least one layer is spread over the original background, that the part of these geotextiles arriving at the height of the dike submerged with mussels and that said geotextile is folded over this mass of mussels, in order to anchor it then in the sand to be backfilled.

The invention also relates to an artificial beach or a raised beach produced according to the method according to the invention.

Other details and advantages of the invention will become apparent from the following description of a process for producing an artificial beach by backfilling with sand or raising an existing beach and the beach thus obtained, according to the invention. 'invention.

This description is given by way of example only and does not limit the invention. References refer to the appended figure.

The appended figure is a cross section of a patch obtained according to the invention.

In the text below, the word river will always be used, although it is clear that it can also be a river mouth or a sea here.

The channel of the river is represented by a strongly inclined bottom 1. The angle of inclination represented here is obviously completely arbitrary.

The background of the original range can coincide with the line AB. Most of the time, this is purely theoretical. In reality, the background of the original track may coincide or substantially coincide with the dashed line CD. In such a case, the necessary sand is first dredged until a bottom is obtained which coincides with the straight line AB. Also the representation of the curved line CD is completely arbitrary.

In any case, where the submerged dam 2 must be established, a flat bottom B-D is first created by dredging.

When due to natural or local circumstances, the original background is already approaching the horizontality of the straight line B-D, it is not necessary to dredge.

The construction of the submerged dam 2 is done using geotextiles. By reference 3, this part of the geotextiles is highlighted which is first spread over either the original background or the newly created background. The geotextiles therefore extending for the most part on this soil, extend further beyond under the submerged dike 2. The submerged dike is constructed by the arrangement of molds 4, while the geotextiles 3 are folded around this first mass of molds to then again form a second layer of geotextile to a height which is actually arbitrary.

The submerged dam 2 can also be raised by one or more layers of molds 5, wrapped in geotextiles 6, the two bands directed towards the earth are placed above the first layer 3. Only then is the fresh sand 7 can be backfilled by dredging until the desired inclination is obtained.

The finishing of the dike submerged by molds or other common materials for this purpose does not belong to the essence of the invention. The layer of finishing materials is highlighted by reference 8.

Note in the figure that the internal reinforcement of the submerged dam 2 is formed in layers by the deployment of two or more layers of geotextiles.

The required anchoring length of these geotextiles is calculated according to the necessary internal stability of the dike submerged. Geotextiles therefore serve as an anchor along the original bottom or the newly dredged bottom. The friction between the sand and the geotextile is also an important anchoring factor.

In the structure according to the invention the friction which is caused by the vertical load P of the freshly backfilled sand over the anchoring length of the geotextiles is therefore W. The necessary anchoring length is determined as a function of the nominal tensile strength geotextiles themselves. This has the consequence that the more the inclination of the original bottom or the new bottom after dredging a quantity of sand is strong, the more important will be the anchoring length of the geotextiles under the freshly backfilled sand.

The geotextiles used for this purpose are exclusively high-quality tensile-resistant textiles of the type which is marketed by the company UCO under the references:
H5200 / 45 (44667) - UCO 20
52/60 (44615) - UCO 4.

The method according to the invention allows the use of dikes established for common hydraulic backfilling without having to anchor them using drilled anchors or sheet piles. This is why the process is especially, if not exclusively, indicated for the repair or rehabilitation of beaches using fresh sand to be backfilled, in all circumstances when the inclination of the original bottom is so steep that the backfilling of sand leads to great losses.

It goes without saying that the invention is not limited to the embodiment described above and numerous modifications could be made to it without departing from the scope of the patent application.

Claims (6)

1. Method of making an artificial beach by backfilling with sand or raising an existing beach in a river, a mouth of a river or the sea, the original slope of the soil is too large for retain the backfilled sand, characterized in that a submerged dike (2) is made on the bottom of the river, if necessary on an artificially dredged bottom, in that this submerged dike is constructed from materials which are the sliding test along the inclination of the original bottom of the river or the sea and in that we bring by backfilling the sand necessary, for the formation of said beach, between this submerged dike and the earth up to the desired height and the desired inclination. 2. Method according to claim 1, characterized in that the top of the above-mentioned submerged dam (2) is established substantially at the level of the average low tide, when the river or the sea is subject to tides. 3. Method according to one of claims 1, 2, characterized in that the above-mentioned submerged dam (2) is established at a distance from the ground allowing the realization of a gentle slope of the beach. 4. Method according to one of claims 1 to 3, characterized in that the above-mentioned submerged dam (2) is produced using geotextiles (3, 6) of which at least one layer is spread over the original bottom , if necessary on a dredged bottom for this purpose, in that the part of these geotextiles arriving at the level of the submerged dike is loaded with mussels and in that the said geotextiles are folded over the mass of mussels, these geotextiles then being anchored in the sand to be backfilled. 5. Method according to claim 4, characterized in that the anchoring of the aforementioned geotextiles takes place by spreading these geotextiles (3, 6) over a sufficient length over the original background, if necessary the bottom dredged for this purpose. 6. Artificial or raised beach produced by applying one of claims 1 to 4, characterized in that it is consisting, in a cross section, of a submerged dike (2) which is parallel or substantially parallel to the ground and in that it consists mainly of molds (4, 5) or a technically equivalent material, wrapped in geotextiles (3, 6) used, over a length under the freshly backfilled sand (7), to form or elevate the beach.

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