WO1995006782A1

WO1995006782A1 - Method and device for applying a layer of material

Info

Publication number: WO1995006782A1
Application number: PCT/NL1994/000210
Authority: WO
Inventors: Gérardus Louis Marie VAN DER SCHRIEK
Original assignee: Hollandsche Beton Groep NV
Current assignee: Hollandsche Beton Groep NV
Priority date: 1993-09-01
Filing date: 1994-09-01
Publication date: 1995-03-09
Anticipated expiration: 1996-03-01
Also published as: AU7864694A; NL9301513A

Abstract

Method and device for applying a layer of material in or on a bed (2) of a river, lake, sea or the like. To this end, a fluid which contains the material is injected into or onto said bed. When the fluid is injected into the material of the bed (2), said bed material swirls up and may form a mixture with the material and the fluid. In order to ensure that said layer stabilises and then settles on the bed, especially when said method is used on slopes, it is proposed to provide a guide (5) following the distribution device. In this way, during the initial period following injection of the fluid, the cloud thus formed is able to shift position only to a limited extent and can precipitate in a controlled manner.

Description

Method and device for applying a layer of material.

The present invention relates to a method for applying a layer of material in or on a body, such as the bed of, for example, a lake, sea or river. With this procedure it is essential that water is present above the bed. When applying a layer of material of this type, especially if said material is applied in dilute form, for example with water as the transport medium, the problem arises that the material lying on top of the bed swirls up, as a result of which a cloud is formed, which easily moves away. Another problem that is experienced in particular with sloping beds is that the material to be applied moves down the sloping bed to the lowest point.

The problem of the existing material of the bed swirling up arises in particular if the layer of material is applied by injecting into the bed. With this procedure, swirling up of this nature is a deliberate aim, the intention being that the mixture composed of the material applied and the original bed material then settles again.

All sorts of layers of material can be applied on beds. The same is true for the application of layers of material in beds.One example is the provision of a sealing layer on a bed. Sealing layers of this type are used, for example, in sludge dumps or other man-made constructions where it is important that a complete seal remains in place even in the longer term. To this end, for example, a lake or the like is, if appropriate, excavated further to increase the depth and a material is applied to the bed thereof, which material may or may not contain bed material or mix with the bed material, which preferably is granular. By, at a later stage, applying a further material which reacts with the first material, occlusion of the pores between the grains can be achieved. Said further material can either be applied separately or can already be present in the material to be dumped. It is also possible to apply such a seal on material which has already been dumped.

Should the sealing layer break open as a consequence of subse¬ quent subsidence, a new sealing layer will very rapidly be formed by diffu¬ sion of further material towards the material applied. Compared with con¬ structions using layers of sheeting, a technique of this type has the advantage that it provides a guaranteed seal over a very long period. After all, the thickness of the seal is only a fraction of the thickness of the layer of material which contains the relevant chemicals to produce a seal. With this technique it is, of course, very important that the bed is pro- vided with a uniform layer of material over its entire surface. In view of the phenomena described above, it is important that the material applied is stabilised together with the material of the bed.

The aim of the present invention is to provide a stabilisation of this type, so that a relatively small layer thickness can suffice.

This aim is achieved with a method for applying a layer of material to a body, such as the bed of a lake, in that said method com¬ prises injecting fluid, which contains said material, onto or into the bed in various positions located some distance apart on or in the bed, using a distribution device, and moving the distribution device over the bed when injecting the fluid thereon, the fluid being guided, after application, at an angle with respect to the direction of movement of the distribution device.

The invention is based on the insight that by providing a guide, following application of the material which is incorporated in the fluid, a shift in position both of said material and of the bed material which may swirl up is impossible or virtually impossible.

Preferably, guiding takes place in the same direction as the direction of movement of the distribution device, but after introduction of the fluid.

Guiding can take place either laterally or in the upwards direc¬ tion. Guiding in the lateral direction prevents movement of material to the lowest point from taking place, especially in the case of slopes. Guiding in the upwards direction prevents the formation of freely moving clouds as a result of material swirling up, which clouds can easily flow away. If injection into the material of the bed, as well as the mixing thereof, is important, it is preferred to carry out guiding using vertical plates, which plates are moved in the existing bed as the fluid is introduced.

The method described above can be used to introduce any sort of material onto or into the bed. The application of sand and other layers can be considered. If, however, the aim is to provide a sealing layer, the fluid preferably comprises at least one component of a bed-sealing layer.

The invention also relates to a device for carrying out the method described above. Said device comprises a distribution device to be moved over the body, which device comprises a number of discharge nozzles for fluid, which are some distance apart, guide means being arranged close to the discharge nozzles, which guide means extend backwards with respect to the direction of movement. These guide means preferably comprise vertical plates for lateral guiding. If horizontal guiding has to be pro¬ vided, it has been found advantageous to construct any horizontal delimita¬ tion such that it allows water to pass through. A cloth can be considered in this context. In order to loosen the bed before injection of the fluid, if mixing of the material to be applied with the material of the bed is desired, cutting means are preferably used which are arranged in front of the discharge nozzles in the direction of movement. It is also possible that cutting means are arranged in front of the vertical guide plates only. These cutting means can comprise, for example, an extension of the vertical plates in a special knife shape or can be arranged by fitting separate water jets, which act as water saws.

The nozzles can be directed, depending on the way in which the fluid is applied. If swirling up of the bed is desired, said nozzles can be arranged pointing downwards. It is also possible to arrange said nozzles such that they are to some extent opposed to the direction of movement of the device.

In order to be able to move over the bed surfaces of varying slope and in order to cover as large as possible a width of such a bed surface, the distribution device having the guide means according to the invention is articulated according to the invention. With this arrangement, the guide means are arranged so that they are movable with respect to one another. In order to stabilise the clouds that may be formed together with the mixture of bed material and applied material as rapidly as possible, it is proposed according to the invention to fit vibration means. The latter effect a separation of water from the materials concerned.

To prevent the device according to the invention from burrowing itself completely in the bed, the distribution device is, according to a preferred embodiment of the invention, provided with at least one carrier which extends transversely to the direction of movement. With the aid of the ski effect, the device is in this way kept above the level of the bed. Of course, various carriers of this type can be present. The invention will be explained in more detail below with the aid of an illustrative embodi¬ ment shown in the drawing. In the drawing:

Fig. 1 shows a perspective view of the device according to the invention positioned on a slope, and

Fig. 2 shows a side view of the device according to Fig. 1. The device according to the invention comprises a distribution device 1, to which vertical plates 2 are connected. These vertical plates are located some distance apart. A cloth 6, which allows water to pass through, is arranged over the vertical plates 5. With this arrangement, the pores of the cloth are such that the material of the bed of a lake, sea or other water-containing reservoir is not able to move through said cloth. Distribution device 1 comprises a horizontal carrier 9. which is hollow on the inside and to which a feed line 11 is connected, said line being pro¬ vided with a pump 10 for introducing a fluid, which comprises the relevant material to be injected, into the horizontal carrier 9- The carrier 9 s provided on its underside with a series of discharge nozzles 3« Cutting elements 7 are fitted in front of the carrier - At the free end, the vertical plates are held together by an auxiliary carrier 4. Carrier 9 is provided with a vibration device 8 which acts on the vertical plates 5« Hinge constructions 13 are present to make the carriers 4 and 9 hingeable. The device described above functions as follows: When the device is used on a somewhat sloping bed 2, said device is moved in the direction of the arrow 12. This can be effected by any means known from the prior art. Via line 11 and pump 10, water, for example, in which, for example, a material is present which together with another chemical provides a sealing layer, is supplied. The bed can con- sist, for example, of a granular material, such as sand. As the device moves over the bed, the cutting elements 7 will sink down into the bed, as can be seen in particular in Fig. 2. Irregularities are compensated for by means of the hinge constructions 13- Carrier 9 and an auxiliary carrier 4 prevent the cutting elements from sinking down deeply into the bed. The fluid, together with the material to be introduced, is injected, at the location of carrier 9. via nozzles 3» into the bed material swirled up by the cutting elements and/or the flowing fluid. During injection, a cloud forms. Said cloud is a mixture of the bed material, the material introduced and the water. It is important that said cloud settles as rapidly as poss- ible, because a cloud of this type can simply flow away, with the conse¬ quence that it is no longer guaranteed that the material concerned is applied in the correct manner. As a consequence of the presence of guide means in both the vertical and the horizontal direction and of the use of the vibration means, the cloud rapidly becomes unstable and the various material components will separate out from the water and settle.

When the device has passed by, the top layer of the body, such as the bed of a lake, sea or river, is stable again and there is therefore no further movement of said top layer thereafter. Example:

A device as described above was dragged over the bed. The length of the carrier 9 and auxiliary carrier 4 was about 10 metres, whilst the length of the vertical plates was 15 metres. The depth at which the cut- ting elements moved in the bed was between 30 and 50 cm. Said device was dragged over a sandy bed, which was composed of fine sand. During this operation a mixture of calcium hydroxide and gypsum (calcium sulphate dihydrate) was introduced with the fluid. By introducing said fluid using nozzles that faced obliquely to the rear with respect to the direction of movement, a mixture of calcium oxide and gypsum having a concentration of 20-40 % was formed in the sandy layer of the bed. A highly concentrated (100 %) layer of the components in question was produced on the layer of the bed. Preferably the constituents injected have a relatively large particle size. After all, if said constituents were to be present in the form of fine particles, there is a risk of sedimentary flow. However, the large particles have the disadvantage that they make up part of the grain skeleton of the sand grains, as a result of which there is an effect on the sandy layer if the calcium hydroxide dissolves. In order to achieve as little as possible swirling up and formation of clouds composed of water and bed material and the material introduced, and to achieve an effective penetration depth, injection with a small amount of water and under high pressure is proposed. In contrast to other methods known from the prior art, such as flushing methods for cleaning polluted beds, for which a pressure of about 1 bar is used, a pressure of between 16 and 20 bar is used in the present illustrative embodiment.

It has been found that, with the guiding used here, demixing of material and water takes place in good time, so that there is no longer a risk of the material introduced moving away.

Although the invention has been described with reference to the introduction of a chemical into a layer of a bed, it is, of course, poss¬ ible also to apply substrate material, such as coarse-grained sand, in the fluid. This is important in particular in the case of beds which do not contain sandy material of this type or which contain sandy material of incorrect composition. Of course, it is also possible to construct the device with detail modifications. That is to say, the introduction of the fluid does not necessarily have to take place via a central carrier 9- Moreover, said device can also comprise a number of devices positioned alongside one another, which devices are optionally offset with respect to one another in order to cover a relatively large bed surface with a single drag movement. All such modifications are considered to fall within the scope of the appended claims.

Claims

1. Method for applying a layer of material in or on a body, such as the bed of a lake, said method comprising injecting a fluid, which con¬ tains said material, onto or into the bed in various positions located some distance apart on or in the bed, using a distribution device (1), and mov¬ ing the distribution device over the bed when injecting the fluid thereon, the fluid being guided, after application, at an angle with respect to the direction of movement of the distribution device, characterised in that said angle is about 180° and in that the fluid is guided down to the bed.

2. Method according to Claim 1, wherein guiding takes place in the lateral direction with respect to the surface of the bed.

3. Method according to one of the preceding claims, wherein guiding takes place in the upwards direction with respect to the surface of the bed.

4. Method according to one of the preceding claims, wherein guiding is produced at least using essentially vertical plates (5) , which plates are moved in the existing bed as the fluid is introduced.

5. Method according to one of the preceding claims, wherein the fluid comprises at least one component of a bed-sealing layer.

6. Method according to one of Claims 1 to 4, wherein the fluid contains material having a particle size distribution such that, on mixing of the top layer of the body, after settling, the risk of sedimentary flow is less than that with the original material of the top layer.

7. Device for carrying out the method according to one of the preceding claims for applying a layer of material in or on a body, such as the bed of a lake, comprising a distribution device (1) to be moved over the bed, which device comprises a number of discharge nozzles (3) for fluid, which are some distance apart, guide means (5. 6) being arranged close to the discharge nozzles, which guide means extend in a direction counter to the direction of movement of the device, characterised in that the guide means extend at least down to the bed.

8. Device according to Claim 7 , wherein the guide means comprise vertical plates (5) •