DK141256B - Method of preventing coastal erosion. - Google Patents

Description

161256

The invention relates to a method of preventing coastal erosion using bodies of water-permeable material enclosing a filler material consisting of sand and / or rock.

5 In order to protect coastal stretches, shorelines, rivers, hips, dikes and similar areas from erosion, various methods and means have been proposed.

These proposals can be systematically divided into four groups in the main sections.

10 The first group comprises the building of courtiers. These can be constructed in various ways, e.g. by laying concrete blocks of suitable sizes and in conjunction or by laying stones between suspended piles. The disadvantage of hips of the above kind is that, as they go above the water, they switch off and deflect the current. This creates very powerful eddy currents, which undermine and break down the hip, partly by cutting power at the outermost end of the hip and partly by cutting back the connection of the hip ashore. In addition, a single hip at the deflection it provides the current will create erosion for some distance from the hip. In addition, these hips are extremely expensive to construct and, according to the above, have a relatively limited service life, even when a part is sacrificed for maintenance.

The second group concerns the efforts to maintain the seabed, which e.g. involves laying foil on the seabed or laying underwater machines. The disadvantage of these is their very short lifespan. It has among other things proved to be very difficult to retain foils on the seabed.

The third group includes the efforts made for 50 by leveling, paving and more. of dunes to reduce erosion. These works are very costly and do not hinder erosion, but only delay it.

1A1256 2

The fourth option is the laying of artificial seaweed. This solution seems effective but has not yet been adequately tested on the open coast.

In emergencies, sandbags are used, especially when securing fish. However, these bags are heavy to carry and will still easily be moved by the lake or undermined and buried at the bottom.

It is an object of the invention to provide a method which does not overcome the above-mentioned disadvantages and which can be quickly accomplished by readily obtainable materials, and which effectively protects coastal stretches and similar areas.

The process according to the invention is characterized by the characterizing part of the claim. The hose may be of any suitable plastic material, provided that the condition of perforation is fulfilled.

Perforated plastic tubing of extruded plastic can be used, and also plastic film tubing supplied in webs and welded at the point of use. In addition, tubes made of woven or knotted materials can be used, including products of plastic threads, plastic filaments and other materials used for textiles.

If a length of such a hose filled with sand or stone is laid on the seabed, it will adapt itself to its surface. Since the hose is made without cross joints or constrictions and is also flexible, the contact with the seabed will be uniform and make Tinder mining difficult. If undermining should nevertheless appear to a limited extent under extreme conditions, the hose will not break, 3q but will adapt to the new conditions.

The hose can be laid out as a single length in full, but can also be laid out in two lengths side by side or in several lengths, some of the lengths resting on the underlying lengths.

For certain tasks, the hose may be formed with particular cross-sections, e.g. like a triangle, especially an equilateral triangle.

The shape and size of the hose cross-section can be selected as suitable for the conditions. If desired, the hose can be designed with pendent tabs to catch the movement of the sand on the seabed. Also, on the outside of the hose, 10 artificial forceps may be attached, affecting the flow whose effect causes the erosion.

The hose used can be deployed across the coastline, along it and, as a result of the hose's flexibility, also if necessary in any curved form.

15 The hose can be laid out in a short time, for low cost and in almost all weather conditions.

As the hose wall is perforated, the water can pass out through the perforations. Some sand can be carried out with the water through the perforations; however, this is of minor importance, since sand is cheap material and readily available on the coast.

In addition, it has been found that a large proportion of sand particles with smaller particle size than corresponding to the hole size of the perforations are retained in the perforated tube, even when lying on the seabed for months.

This has also been found if the sand material used has been a mixture of sand and clay particles; only during the pumping itself will clay particles be discharged through the perforations, but when the pipe is filled and placed on the seabed, the clay particles will not be washed away.

The method according to the invention can not only be used to protect coastal stretches, but can also advantageously be used for the protection of dikes, the construction of dikes, harbor construction, lemols, containment and watercourse changes, etc.

The invention will now be described in more detail with reference to the accompanying drawings which illustrate some embodiments of the invention. In the drawing, FIG. 1 is a cross-section of a pipe; FIG. 2 is a longitudinal section through the pipe of FIG. 1, FIG. 3 is a vertical section perpendicular to a coastline, illustrating the principle of laying out; FIG. 4 is a plan view of the embodiment of FIG. 3; FIG. 5 in the same way as in FIG. 3 the pipe after finishing the laying.

According to FIG. 1 is a cross-sectional view of the tube prior to laying down. The selected profile is just one example that will change according to conditions. 1 is the pipe wall. 2 is an example of a holder for the hose 3 to be used to pump the filler into the tube. 4 is the water surface. 5 are the buoyancy means holding the tube up, being connected 20 to the tube with a line 6 and secured with slip sticks.

In FIG. 3, the layout is shown schematically, with a vertical section perpendicular to the coastline. Beachfront 7 crosses. in the seabed 8. At the far end you see the anchorage 9. The filling has begun and is done in the example shown from 25 countries. The filling occurs in the vertical transition from the liquid to the submerged portion labeled a.

Pig. 4 is a plan view of FIG. 3 · The inner end of the pipe is anchored to land 10. In fig. 3 and 4, 11 illustrates a pump assembly.

30 Pig. 5 shows the tube closed. In this example, the entire tube is submerged, but in the case that the tube, e.g. by