This invention relates to an apparatus for removing of particles from the bottom of water reservoirs and other water ways, as shown in the introduction to patent claim 1. The invention may be applied upon the removal of sediments from sediment-carrying rivers, e.g. in order to influence bottom processes in the river, or in order to utilize these sediments for various purposes, in connection with farming, sand-and gravel-manufacturing, filling compound for land improvement projects, in searching for minerals, measuring of sediment transportation in rivers, etc. The invention is particularly intended for application involving reservoirs in water courses connected to installations such as power stations, irrigation works and ordinary water supply installations.

The job of the reservoir is to regulate the natural seepage of the river so that water is made available when the consumers need it. In rivers with a large amount of sediment flow, it is difficult to maintain a limited regulation volume for use in periods with a low water flow. The invention may be used in order to regenerate this regulation volume after it has been totally or partially filled up by the sediments transported by the river.

Existing systems for the removal of sedimented masses in reservoirs are based either on draining so that a "river" with adequate transportations capacity to erode in the sedimented masses is generated, or by sucking, scraping or digging up the bottom sediments with the help of various dredging techniques.

The largest and heaviest particles will settle only at the river's inlet to the reservoir. The largest particles must therefore be transported through the entire reservoir through draining or flushing. Draining or flushing must be carried out when there is an abundance of water, but not too much, since in that case one would not be able to lower the water level behind the dam, thereby generating an adequate velocity to erode in the bottom sediments.

The problem presented by removal of sedimented masses is solved to a large extent by an apparatus as shown in Norwegian Patent Application No. 165 851, from the same applicant. In No. 165 851 an apparatus is described where a flushing canal is placed under and connected to a precipitation basin, in its entire length, by a longitudinal crevice. The crevice may be successively opened and closed in the entire length of the precipitation basin, so that the entire flushing capacity of the flushing canal is transferred along the bottom of the precipitation basin, and it will be concentrated on the open portion of the flushing canal, likewise upstream the closed portion of the crevice. A bendable floating element, e.g. a flexible pipe, may be used to

open and close the crevice between the precipitation basin and the flushing canal. The floating element may be engaged and disengaged by filling and draining gas and/or liquid to and from it. One will thereby be able to transfer the point of suction along the bottom of the precipitation basin. The apparatus that is shown in No. 165 851 must be built into the bottom of the precipitation basin either through new installation or through draining and rebuilding. It involves a stationary apparatus, which may not be removed after use or before flood periods, and which requires draining and drying- out for maintenance purposes.

A main object of this present invention is therefore to obtain an apparatus which may be used in old as well as new installations, and which may effectively remove particles which have been precipitated or for some other reason are located at the bottom of the basin.

The object of this present invention is attained through an apparatus with features as indicated in the characterizing portion of Patent Claim 1. Further features will be evident through the accompanying dependent claims. In the following text the invention will be described in more detail with the help of examples of embodiments of the invention, and with reference to enclosed drawings, where fig. 1 shows a dam in a sediment-carrying river where there is drawn in a precipitation basin according to prior art, and an apparatus according to present invention, fig. 2 shows a longitudinal section of the basin in fig. 1, which gives a view of a first, principal embodiment of this present invention in longitude. fig. 3 shows a cross-section of one of the elements in figure 2 with floating elements drawn in, and fig. 4 shows a side-section of one of the elements in figure 3, and fig. 6 shows a cross-section of one of the elements in figure 4, with floating elements drawn in.

By first referring to figure 1, a water reservoir 1 is shown connected to a dam 2. In the water reservoir, sediments 3 which are transported by the river into the reservoir are separated and stored in the bottom of the river. After a while the sediments 3 will constitute a problem inasmuch as they reduce the water volume needed for regulation norm. A precipitation basin of prior art is indicated at reference no. 4, e.g. as shown in NO 165 851. From this point sand and flushing water travels back to the river downstream from the dam, whereas purified water goes to a power station, an irrigation installation, or for some other purpose.

In fig. 1 there is also drawn an illustration of the apparatus in accordance with the present invention, generally described 7. This is linked to the upstream passage through the dam 2 and

3 is therefore revolvable in the horizontal plane and may thereby cover large areas of the reservoir. This is shown by the reference number 7'. The apparatus may easily be moved and connected to several places along the dam so that it may cover the entire reservoir if so desired. By further referring to fig. 2 and 3, a principal embodiment of a flushing pipe 7 is seen, according to present invention. The flushing pipe 7 is constructed as a pipe comprising several elements 10. In principle the flushing pipe 7 comprises a pipe which is cut at regular intervals, but not entirely through, thereby providing the elements 10 as a piece of pipe with open ends and linked to the neighbouring elements at the portion of the pipe cross-section that is not cut. The link mechanism may be provided in several different ways. In the downstream end the flushing pipe 7 is connected to an outlet pipe 14. In the upstream end the flushing pipe is closed, however, a small opening is provided in order to discharge gases which have developed in the sediment and which are released during flushing. The elements 10 are connect to two or more floating/sinking elements 17 which are constructed as flexible tubes or pipes which may be filled with and drained of water and/or air through an operating pipe 26. The floating elements 17 run through a conduit 27 on each side of the flushing pipe element 10. The floating element 17 is fastened only to the end elements 28 and 29. The floating elements 17 are to a certain extent elastic in the longitudinal direction and are stretched somewhat so that the elements close in toward each other when not exposed to a side load in the vertical plane. The elements 10 are thereby articulated so that the point of linkage is above when the flushing pipe 7 is bent in the suction area 13 at the sediments and below when the flushing pipe 7 is bent in the surface position.

The elements may furthermore be equipped with socket pipes 30, e.g. of rubber, which seal and ensure that water and sediments only may be sucked in from below as illustrated by arrows and reference number 13 in figure 2.

In the upstream end, the floating elements 17 are fastened to a float 18 or something of similar effect so that air may flow in and out of them since the floating elements 17 respectively are drained and filled with water through the operation pipe 26.

When the floating elements are drained of water the flushing pipe 7 will bend because of the flotational force. This will effect openings between two neighbouring elements 10 as shown by the reference number 13. Since the outlet 14 of the flushing pipe 7 lies lower than the water surface 5, the upsream dam 2, or has a lower potential pressure provided through i.e. pumping, this will give an under pressure which allows the water and sediments 3 to be sucked in through the openings 13 and flushing out through the flushing pipe's outlet 14.

By operating the floating elements by slowly filling them with water, the openings 13 may be moved inward in the reservoir as the sediments 3 are flushed out. This suction area may thereby be transferred along the entire length of the flushing pipe 7.

The elements 10 are fastened to a float with the help of a rope 31 or the like, which locks the elements securely at a desired depth during the sinking of the flushing pipe 7.

By revolving the flushing pipe 7 in the horizontal plane around the point of connection in the dam 2, one will be able to cover the desired area of the reservoir as is indicated in figure 1 by 7'.

In figures 4, 5 and 6 are shown a preferred embodiment of this present invention. In principle, the apparatus 7 functions in the same way as one which is illustrated in fig. 2 and 3. An element 10 comprises a tubular body 11 which is open in both ends. A link 12 connects an element with neighbouring elements and seals off for the admission between elements. A downward pointed pipe connection 18 communicates with the pipe connection 11 and has a smaller cross-section surface than the latter. The pipe connection 18 is bent and forms an end portion 19 which in all essence forms a right angle to the longitudinal direction of the pipe connection 11, and which has an opening 20. In the opening 20, the cross-section is preferentially somewhat narrowed.

In the downstream end the element 10 has a plate or something to a similar effect 21 on each side of the pipe connection 11, which is supplied at its lower area with a sealing device 22. This may e.g. be a plate of rubber. The sealing device 22 seals the opening 20 on the pipe connection 18 of the downstream neighbouring element when the flushing pipe 7 and the subsequent one lie adjacent to each other or are bent in the surface position, but is open when it bent outward. A flexible rubber pipe sleeve 23 is connected to the link 12. Two neighbouring elements may swing mutually at an angle which corresponds to the sum of the two angles 24 and 25 at the one end, respectively the other of the element 10. These angles 24 and 25 are preferentially equal, and lie preferentially in the area of 5 to 10 o.

In fig. 5 tfce floating/sinking element is not drawn in. Fig. 6 illustrates a cross-section of element 10, with the floating/sinking elements 17 in one possible embodiment. The floating/sinking elements 17 are constructed as two flexible tubes 17, extending the entire length of the flushing pipe 7. Means of supply and discharge of air and water are not shown in the illustration, but this may be done in a manner corresponding to fig. 2.

This invention is described in the following, through a description of its functional principles and features. With the help of the flushing pipe 7 a suction area may be transferred in a basin so that the sedimented particles may be sucked into a flushing pipe through a

minimum of openings. Buoyancy is utilized in order to transfer the suction area. The apparatus is not stationary, and it does not require extensive building constructions within the reservoir. This entails its applicability also in previously built reservoirs.

Flushing of sediments is done without draining of the reservoir with resulting loss of water and production. The flushing process may be accomplished at times of the year when there is no lack of water, so that the water loss is minimal and the reservoir is intact when the flow of water is at a minimum (drought) and the value of the reservoir is at a peak. A high concentration of sediments may be achieved in the flushing water. The invention is operated solely by gravitational forces and a low amount of energy is required in order to carry out the flushing process. The installation is simple in operation and simple in monitoring. The flushing process may be reversed and repeated at any point of time during the process.

The concept represents a system for the removal of sedimented particles in reservoirs in rivers carrying a large amount of sediment. The extent of the sediment flow has long ago ensured that there are no natural regulating depots such as lakes in the water courses. Artificial reservoirs will have a short life span since they also in time will be filled up. Due to this, larger installations are not being preferred, since these do not fill up as quickly as smaller and gentler reservoirs. Using the present invention, one may maintain the regulating capacity in smaller and medium-sized reservoirs and prevent them from being filled up with sediments. River power stations are traditionally not built with any reservoirs worth mentioning in river carrying an extensive amount of sediment, since is becomes impossible to maintain the regulating volume over a certain amount of time. The larger the general sediment transport is within a supply network, however, the larger the value of a day-regulating depot, since it is impossible to store water. One is therefore at the mercy of the flow of water in the river at any given time. The consequence being the the power station is dimensioned for a minimum flow of water and having to co-ordinate with other energy sources. This results in the utilization of only a fraction of the river's energy potential, at the same time having to invest in supplementing energy supply systems if one is to maintain a high regularity in the energy supply. The alternative to this is extremely large reservoirs which εre not filled up with sediments during the financial life span of the project, but with accompanying expenses and consequences for the local population and environment.

There is a great need of rehabilitation of existing reservoirs at water power as well as irrigational installations, but as far as one knows there is no significant activity in this area and there are no good solutions. Today there are many so- called cascade power stations (several river power stations in a series along one river). Today there have been made efforts, to the

best of one's ability, to flush the reservoirs by draining the depot, but with the result that the sand which one manages to flush out ends up inside the next intake basin. With the help of the present invention one would be able to take care of the sediments in the upper depot, at the same time as one is able to utilize the masses as a resource. Furthermore, the other downstream depots are protected.

The invention may also be applied in connection with irrigational projects and water supply installations. The potential for farming purposes seems to be particularly large with regard to the lower regime in rivers carrying an extensive amount of sediments where it may contribute to stabilizing rivers, reduce danger of flooding, and secure old and excavate new farmland. Repeated use of irrigational installations will also be made possible, where the irrigation water is purified enough and the flushed masses are used to raise downstream areas along the river adequately above ground water level, so that farming may be carried out.