The invention relates to a water-barrier according to the preamble of Claim 1. The invention also relates to a method for the production of such a water-barrier.

A water-barrier of this type is generally known. The water-barrier may, for example, be a dune or a dyke. The water-barrier may be provided next to a body of water, such as for example the sea. The water-barrier may extend in a longitudinal direction of the water line. The water-barrier comprises a slope having a height such that the water- barrier protects the land situated behind it against high water, for example as a result of a flood or a storm.

It is a drawback of the known water-barrier that the cross-sectional profile of the water- barrier is subject to change. In particular, it is a drawback of the known water-barrier that the profile is subject to erosion. The profile of, for example, a dune can change due to erosion by wind and/or water. A dune can be subject to dune erosion. Dune erosion is the phenomenon whereby a significant part of a dune is eroded following a violent storm and high seas. Dune erosion is a natural process and after the erosion the sand will gradually bank up again. This leads to a certain amount of growth which is, however, smaller than the erosion. If the dunes form part of a seawall, dune erosion is a great risk and may result in flooding of the hinterland. Buildings which have been built close to the edge of the dunes can be undercut as a result of dune erosion and eventually subside. Such a process may also occur with other water-barriers.

It is known from GB 1403944 A to provide a mat of fibre material on an existing slope and to anchor it with pins.

WO 96/25560 describes a system for preventing erosion consisting of a number of posts driven into the ground, with a fence having large openings through which water and sand can move freely extending above the surface of the dunes or beach. It is assumed that the fence produced in this way causes sand to separate out of the water. US 2007/0280789 discloses a breakwater consisting of an elongate and approximately semicircular body behind which (viewed from the direction from which the water comes) a fencing is erected consisting of posts which have been anchored in the ground and to which a sheet of material has been attached.

It is therefore an object of the invention to provide a water-barrier, comprising a sandy soil with a slope, in which at least one drawback of the known water-barriers is alleviated or prevented. Furthermore, it is an object of the invention to provide a water- barrier by means of which the profile of the slope can be maintained and/or formed. It is also an object to provide a method for producing a water-barrier by means of which at least one drawback of the known water-barriers is alleviated or prevented.

Li order to achieve at least one of the objects, the invention provides a water-barrier having the properties of Claim 1. The geotextile screen is provided, by means of the positioning of the anchoring elements, with a curve, from a relatively high point on the slope, via a point on the slope which is lower, to another high point on the slope. The curve may be a V shape or a U shape. The geotextile screen may be installed in a zigzag manner in the slope. The geotextile screen is provided with a dip, as it were. The geotextile is permeable to water, but not to the sandy soil. The geotextile screen in the slope thus ensures that the sandy soil is held in place. The geotextile screen ensures that the slope is stabilized relatively well, as a result of which erosion and abrasion are prevented.

Apart from being used as a water-barrier, the present invention can also be used to prevent landslides, for example consisting of large amounts of muddy material. It is likewise possible to use the above-described structure to reclaim land from the sea.

In the desired final state, the geotextile screen, which is permeable to water and retains sand, is for the greater part and preferably substantially completely below the surface of the water-barrier. Preferably, the permeability of the geotextile is such that it does not affect the water-permeability of the sand, that is to say is at least equal to the water- permeability of the sand which is present. The expression non-permeability of the sand bridge bottom is understood to mean that the geotextile does not allow the mean screening fraction and coarser of the sandy soil to pass..

Before the desired final state is reached, the geotextile screen may protrude above the surface and be used for gathering sand and/or other material.

Due to the particular way in which the geotextile screen is arranged, a layer of sandy soil which is situated against the latter is constructed and/or maintained in an optimum manner.

It will be understood that the present invention can be used both on sea coasts and river dykes. In the case of river dykes, the composition of the soil will differ from that at the coast, but the mechanism of constructing and maintaining a water-barrier is the same in both cases.

Preferably, the water-barrier comprises an additional number of anchoring elements which are placed in the ground and which are brought into contact with the geotextile, the anchoring elements, in a longitudinal direction of the water-barrier, being provided alternately at a high and a low position in order to form a geotextile screen having a sawtooth-shaped cross section. The dimensions of the dipped parts, such as for example the V-shaped parts, may vary. The geotextile screen can be arranged in a zigzag manner, thus stabilizing the water-barrier over a certain length. This not only prevents the sandy water-barrier from sliding, but also counters erosion.

On the other hand, it is possible for the water-barrier to comprise an additional number of anchoring elements which are placed in the ground and which are brought into contact with the geotextile, wherein two anchoring elements, in a longitudinal direction of the water-barrier, being placed alternately in a high and a low position in order to form a geotextile screen having a dovetail shaped cross section. The water-barrier is stabilized along a certain length in this case as well. This embodiment also ensures a relatively good stabilization, and can for example be used as an alternative to sheet piling. In order to produce a desired profile of the water-barrier, it is possible for the top of the geotextile screen to protrude above the slope over a certain distance. This applies in particular to that section of the water-barrier which is far from the water line and where the coast and/or the water-barrier are to be increased in height. As a result thereof, sand particles of the sandy soil can collect at the tip of the V shape or U shape. The sandy soil will thus be able to accumulate between an upper part of the slope and the geotextile screen. In this way, the profile of the water-barrier can be shaped to form a desired safety profile. It has, for example, been found that the eroded sand from a dune is largely carried away by the current. This sand will drift and partly fly up onto the dune elsewhere, thus resulting in growth of the dune. The protruding geotextile screens are better at retaining the drifting sand, as a result of which the dune can be formed.

At least one anchoring element may be a substantially hollow anchoring element. The hollow anchoring element is relatively lightweight. However, the anchoring element does provide sufficient strength and, in addition, the anchoring element can be placed in a relatively simple manner.

In order to anchor the geotextile screen more securely, at least one anchoring element may be anchored in the ground by means of a binder. Obviously, it is also possible to anchor additional anchoring elements.

The binder may comprise a hardening mortar. The mortar can be applied relatively easily, following which the mortar will harden. The anchoring element will thus be securely anchored in the ground.

In one embodiment, the anchoring element comprises a bamboo post. Bamboo is a relatively inexpensive and environmentally friendly material. Bamboo is also a relatively lightweight and strong material. In addition, bamboo is relatively resilient. In this case, it is possible to provide the anchoring element or the bamboo post with apertures at the bottom so that, when the hardening mortar is pushed into the latter from above, this material runs out of the apertures at the bottom and thus forms a cloud or roots of such mortar extending beyond the anchoring element and providing further anchoring in the underlying ground. The diameter of the anchoring element may be approximately 20 cm. The part of the anchoring element which is situated in the ground may have a length which is between 3 and 6 m. This diameter and/or length of the anchoring element ensures that the anchoring element can be manipulated relatively easily. The depth to which the screen is introduced into the ground depends on its position. In the preferred embodiment, a depth of at least 1.5 and more particularly of 1.5-3 metres is now preferred. Further up the slope, the depth over which the geotextile with the anchoring element extends into the ground is greater. The anchoring element can also be fitted in the ground relatively easily. In particular when used in dykes, vibrations should be prevented from occurring during installation as much as possible. To this end, it is for example possible, when using a bamboo post, to provide the bottom thereof with teeth in order to enable displacement in the vertical direction by means of rotation. In the case of hard subsoil, it is likewise possible to use a steel tube to create an opening in the ground and to place an anchoring element, such as a bamboo post, in this steel tube. When the anchoring element is subsequently left behind, the steel tube is removed from the ground.

If necessary, the anchoring element can be embodied such that it can be extended. It is, for example, possible to use attachments, inserts and/or cleats in order to reach dimensions in excess of 3 to 6 metres.

In one embodiment, the water-barrier comprises at least one second geotextile screen which is placed lower or higher on the slope than the first geotextile screen. Use of several geotextile screens at different heights will contribute to the stability of the water-barrier.

Preferably, the second geotextile screen extends substantially parallel to the first geotextile screen. The at least two geotextile screens may, for example, be set up in a cascade arrangement in the water-barrier. In this manner, it is possible to maintain the profile of the water-barrier across its width.

According to an advantageous embodiment of the invention, there is, in addition to a part extending parallel to the water line, a part which extends at an angle or perpendicular thereto and which prevents lateral erosion. In the case of two or more screens, such a part of the screens which extends at an angle or perpendicular to the water line can extend across the entire distance between the screens or across a part of the distance therebetween. Preferably, the end part of one of the screens is used for this purpose. In addition, in the case of relatively great lengths comprising further screens, it is possible to install dividing partitions in order to achieve compartmentalization.

It is possible for the tops of the at least two geotextile screens to coincide with a desired level of the slope. In this way, it is possible to form the profile of the water-barrier to be a desired profile. The desired profile may be a safety profile. The safety profile may, for example, be based on a calculated high-water level.

Preferably, at least one geotextile screen is placed in the underwater shore of a coastline and at least one geotextile screen is placed in the dune base of a dune profile. The water-barrier in this case is a dune. The geotextile screens can be placed at locations where there is a relatively significant change in the incline of the profile of the dune. These locations are usually the underwater shore and the dune base. The geotextile screen in the underwater shore may be partly or completely submerged under water. This geotextile screen is embodied to protect the profile of the underwater shore. The underwater shore is continuously being eroded due to the cyclic motion of the sea. In addition, sea currents provide a continuous supply of sandy soil. This sandy soil can be collected by means of a geotextile screen in the underwater shore. As a result thereof, the profile of in particular that part close to the water line, such as the foreshore, can be protected. At the location of the underwater shore, the profile of the water-barrier can be maintained and/or formed. This increases the stability of the base of the water- barrier. In combination with a geotextile screen in the dune base of the dune, the entire water-barrier is stabilized.

In order to increase the stability of the complete water-barrier, preferably at least two geotextile screens are placed in the underwater shore, and at least two geotextile screens are placed in the dune base. According to one aspect of the invention, a method for reinforcing a water-barrier comprising a sandy soil with a slope is provided. The method comprises the step of: installing a geotextile in the ground; placing at least three anchoring elements in the ground, at least two anchoring elements being placed in a higher position on the slope with respect to at least one anchoring element; and bringing the geotextile into contact with the at least three anchoring elements, and thus forming a geotextile screen. In this manner, it is relatively simple to install a geotextile screen in sandy soil, and thus to reinforce the water-barrier, such as for example a dune.

The method may comprise the steps of placing at least one additional anchoring element in the ground, and bringing the geotextile into contact with the at least one additional anchoring element. In this way, it is possible to place a relatively long geotextile screen in the ground. The geotextile screen may, for example, extend in the longitudinal direction of the water-barrier, and thus reinforce a significant length of the water-barrier.

The geotextile can be brought into contact with the anchoring elements in an alternating fashion. The geotextile can thus be tensioned in a relatively simple manner.

It is possible for the method according to the invention to be repeated at least once. In this case, it is possible to obtain an elongated geotextile screen or to place an additional geotextile screen.

Repeating the method may comprise arranging an additional geotextile screen at a lower or higher position on the slope. In this manner, a system of geotextile screens is obtained, by means of which the slope can be maintained and/or formed across its width.

The method may comprise the additional step of creating a furrow in the ground and subsequently placing the geotextile therein. In this way, the geotextile can be placed relatively easily and quickly. Preferably, the furrow is created in the ground by means of a groove cutter. In this way, a furrow can be created in sandy soil relatively easily, safely, quickly and directly.

Preferably, installing the anchoring elements in the ground comprises screwing in the anchoring elements. The anchoring elements can thus be anchored firmly into the ground. In addition, screwing in of the anchoring element makes it possible to pull the geotextile taut. Fitting the anchoring elements by means of screwing in is relatively simple. If desired, screwing in can be carried out by hand or by means of a machine which is suitable for the purpose. The anchoring elements can also be provided with a pointed head, so that screwing into the ground is facilitated. The provision of a serrated edge can also facilitate screwing in.

The anchoring element may be hollow, and comprise at least one sheath opening which extends from the outer sheath to the inner sheath, and which is in open communication with a filling opening at the top of the anchoring element. The method may comprise the additional step of anchoring the anchoring elements. Anchoring can take place by means of pressurized injection of a binder via the filling opening, and connecting the binder to the ground via the sheath opening. The filling opening and the sheath opening of the anchoring element ensure that the anchoring element can be anchored more securely by means of a binder in a relatively simple way. The binder may, for example, comprise a hardening mortar.

According to a further aspect of the invention, a geotextile screen for use in a water- barrier according to the invention is provided, in which the geotextile screen comprises a geotextile and at least three anchoring elements.

The invention will be described in more detail below with reference to a description of a number of exemplary embodiments which are illustrated in the figures. However, the invention is not limited to these embodiments. Although the description of the invention refers to a number of advantages which are mentioned explicitly, the embodiments described also comprise a number of advantages which are not mentioned explicitly. It is possible to file a divisional patent application specifically for these explicit or implicit advantages. In the figures:

Fig. 1 shows a cross-sectional side view of a dune profile provided with a system comprising a number of geotextile screens for maintaining and/or forming the dune profile;

Figs. 2a and 2b show a top view and a perspective view of an embodiment of a geotextile screen;

Figs. 3a and 3b show top views of embodiments of the geotextile screen; Fig. 4 shows a side view of an embodiment of the geotextile screen; and Fig. 5 shows a top view of a further embodiment of the invention.

Fig. 1 shows a cross-sectional view of a sandy coast 1 with a dune 2 and sea 3. The dune comprises an underwater shore 11, a beach 12, a dune base 13 and a dune top 15. The dune comprises sandy soil with a slope. The sea 3 has a level which corresponds to the current level (for example N.A.P. - Normaal Amsterdams Peil or Amsterdam Ordnance Datum), and which is indicated by the line I. The calculated high-water mark, that is to say the expected storm tide level in the near future, taking the rising sea levels into account, is indicated by the line II. In addition, the expected level in a few centuries, for example the calculated high- water mark in 200 years, is indicated by the line III. The levels II, III in the near and distant future are higher than the current level I. The current profile of the dune top is indicated by the solid line A. The current dune profile has a dune top 15. The height of the existing dune profile, that is to say the height of the top 15, can in some cases be insufficient to be able to offer secure protection against rising water. In particular, the height of the top 15 may be insufficient to offer secure protection based on the calculated high- water mark II and is certainly insufficient for the future calculated high-water mark III, if no measures are taken on the foreshore of the water-barrier. It may therefore be desirable to raise the dune profile up to a desired profile. The desired or required profile of the dune 2 is indicated by the dashed line B. The dune, in its desired profile, has a dune top 14 which is situated at a higher level than the dune top 15 of the current profile A.

In the dune 2, a number of geotextile screens 21-25 have been installed in order to thus form and/or maintain the dune. The geotextile screen may comprise a number of anchoring elements as well as a geotextile which is brought into contact with the anchoring elements. In the illustrated embodiment, the anchoring elements and the geotextile are placed substantially vertically in the ground. Of course, a different arrangement, such as for example a slightly angled position, is possible. Each geotextile screen 21-25 preferably extends substantially in a longitudinal direction of the interface between land 2 and sea 3 (also referred to as the water line). The geotextile screens 21- 25 can extend substantially parallel to one another. However, it may be advantageous to place two geotextile screens at an angle to one another locally.

As will be explained below with reference to Figs. 2 and 3, the anchoring elements of one geotextile screen are placed at different heights in the slope. As a result thereof, V- shaped or U-shaped portions are created in the geotextile screen. The V-shaped or U- shaped portions can be formed in the geotextile in such a manner that the geotextile screen runs in a zigzag manner across the slope. The V-shaped or U-shaped portions are collecting portions. The open sides of these collecting portions are directed towards the top 15 of the slope. The open side forms a collecting tray for sandy soil, as it were, in order to prevent the sand moving from the dune to the sea.

The geotextile screen 21,22 can largely be situated below ground. This ensures that the sandy soil 2 is kept in place. The sand is retained, so that it cannot move to the sea (in the direction of a lower potential). The stability of the slope is thus enhanced.

In addition, it is possible for a part of the geotextile screen 23-25 to be situated above ground. This makes it possible to form the profile of the water-barrier. For example, due to influences from the wind, the sand will be moved in the direction of the top 15 of the slope. Gravity will then move the sand in the direction of the base of the slope and the sand will subsequently get caught by the geotextile screen. The sand is, as it were, deposited in the geotextile screen, thus raising the profile of the water-barrier.

It is possible to arrange a system 5,6 comprising a number of geotextile screens 21- 22,23-25 in the ground. The geotextile screens are placed at a distance from one another in a higher or lower position with respect to one another on the slope. The geotextile screens may run substantially parallel to one another. The tops 28 of the geotextile screens may protrude above ground 2. The tops 28 can be placed in such a manner that they coincide with a desired dune profile B.

The geotextile screens can be installed at various locations in the dune 2. In the illustrated embodiment, two geotextile screens 21,22 are placed at a distance from one another in the underwater shore 11. The geotextile screens in the underwater shore 11 form a system 5. The system 5 is situated below the water level. The system 5 prevents the underwater shore 11 from crumbling away and protects the base of die dune, as it were. By protecting the underwater shore 11 and maintaining a relatively shallow water depth at said location, the force of the waves will be able to be dissipated locally. The force of the waves reaching the beach 12 and the dune base 13 will thus be relatively small. In fact, this also protects the dune profile at the top 15. In order to form the dune profile at the underwater shore 11, it is also possible for the geotextile screens 21,22 to partly protrude from the ground. The geotextile is water-permeable, so that the water can move freely through the screen. However, the geotextile is impermeable to sand, which means that the sand which is carried along by the current is kept in place. The geotextiles are relatively strong, thus acting as a reinforcement layer in order to keep a part of the dune in place. This makes local deposition of sand possible, in turn resulting in the underwater shore becoming less deep.

In order to break the waves in case of high tides and storms, the system may, at the underwater shore, be provided with geotextile which is lowered towards the sea and the upper side of which is provided with self-inflating compartments which rise up at a certain water level and/or storm and thus will break the waves.

The dune base 13 comprises three geotextile screens 23-25 which are situated at a distance apart. These geotextile screens 23-25 also form a system 6, which system is placed such that the depositions of sand will lead to the formation of a dune having a desired dune profile B. The tops 28 can, for example, coincide with the desired profile, but can also be placed at a higher level. It is also possible to place additional geotextile screens by, for example, placing a geotextile screen near or on the top 15. It is likewise possible to place these additional geotextile screens after some time, when the dune profile has already been raised slightly. Figs. 2a and Fig.2b show a top view and a perspective view of (a part of) a geotextile screen 31, respectively. The geotextile screen comprises a geotextile 35 which is brought into contact with at least three anchoring elements 32-34. The anchoring elements 32-34 ensure that the geotextile 35 is tensioned. The geotextile can be arranged around the anchoring elements in an alternating manner, so that the geotextile can easily be tensioned. The anchoring elements 32-24 are placed in a zigzag manner with respect to one another. The anchoring elements 32-34 form a triangle. A base is formed by an imaginary line between the anchoring element 34 and the anchoring element 32. The geotextile extends between the anchoring element 34 and the anchoring element 33 at an angle α with respect to the base. Anchoring element 33 is at a distance δ at right angles with respect to the base. The geotextile screen thus forms a V-shaped cross section. It is possible to place two anchoring elements 32,34 at a higher position on the slope with respect to one another than one anchoring element 33.

Figs. 3a and 3b show embodiments of geotextile screens. Fig. 3a shows a geotextile screen 41 comprising a number of anchoring elements 42,43,46 which have been brought into contact with a geotextile 45. The geotextile may be connected to the anchoring elements by means of means suitable for the purpose, such as for example hook and loop fasteners. The anchoring elements are placed in such a manner that a dovetail-shaped geotextile screen 41 is formed. Thus, collecting portions 47,48 have been produced in the geotextile screen. Fig. 3b shows a geotextile screen 51 having a sawtooth-shaped cross section due to a corresponding positioning of the anchoring elements 52,56 and the geotextile 55. In this case, collecting portions 57,58 have been produced as well.

If various screens are placed one behind the other (viewed from the water line) as shown in Fig.l, according to an advantageous embodiment of the invention a lateral termination is provided, as is illustrated in Fig. 3a by reference numeral 45. This prevents a channel or trench being formed between two successive screens and/or rows of screens, as a result of which sand material could be washed away in the transverse direction (parallel to the water line). Fig.4 shows a side view of a part of a geotextile screen 60 according to an embodiment. The geotextile screen 60 has been placed in sandy soil 61. The geotextile screen 60 partially extends above the ground surface N. The geotextile screen comprises a geotextile 65 having a height h, which has been brought into contact with the anchoring element 62 having a height H. The anchoring element is situated at a deeper level in the ground 61 than the geotextile 65. The anchoring element may be a hollow anchoring element. At the top of the anchoring element, a filling opening 67 is provided. At the bottom of the anchoring element, sheath apertures 64 are provided. The sheath apertures 64 can be provided on all sides of the sheath. The sheath apertures 64 are embodied such that the anchoring element 62 can be anchored in a simple manner by injecting a suitable binder from the filling opening in a pressurized manner. This binder will then flow out 66 via the sheath apertures and come into contact with the sandy soil 61.

Fig. 5 shows a further variant of the present invention in top view. In this case, two geotextile screens 71 and 72 of considerable length have been installed at a distance from one another. Near the ends, side portions 73 and 75 are provided, creating a closed area into which sand and similar material can enter, but cannot readily be carried away, due to the properties of the geotextile screens. For the purposes of further compartmentalization, an auxiliary geotextile screen 74 is provided which extends between the geotextile screens 71 and 72.

It is possible to use various geotextiles. According to the production method, the geotextiles may, for example, be divided into woven, non- woven and knitted fabric. The materials which are generally used in the production of geotextiles are polypropylene and polyester, but other plastics, such as polyethylene, nylon and optical fibre can also be used. In some cases, jute, hemp or coconut are also used. These materials are particularly suitable in cases where the geotextile has to be biodegradable. In combination with an anchoring element made of bamboo, a completely biodegradable geotextile screen is produced. The water permeability of the various geotextiles may be different. A suitable water permeability of the geotextile may be chosen as desired. It will be clear to those skilled in the art that the geotextile screen according to the invention can be used in order to maintain and/or form a water-barrier. The use is not limited to use in a dune adjoining the sea. The geotextile screen can, for example, also be used for the reinforcement of other earth bodies. The geotextile screen can be used in a (sandy) dyke, as well as on construction sites. The geotextile screen can be used particularly advantageously on construction sites in order to prevent subsidence of the earth at or near the construction site.

Apart from that, the geotextile screen according to the invention can help to prevent various instabilities of water-barriers. These instabilities can, for example, be macro- instabilities (inwards and/or outwards), instabilities as a result of infiltration and erosion during transfer, piping, and/or heaving. These instabilities will be known to the person skilled in the art and he/she will be able to place the geotextile screens in such a manner that these instabilities are prevented.