Patent Publication Number: US-2022228342-A1

Title: System for the dradging of underwater sea-beds

Description:
The present invention relates to the systems for the dredging, and in particular relates to a system for the dredging of underwater sea-beds. 
     The water reserves in the world are often accumulated in artificial basins. 
     These basins are almost entirely made up of barriers (dams) of waterways that originally flowed freely in the riverbed, fed by the rainfall that affects the catchment area. 
     The erosion phenomena due to the flow of water to the ground throughout the catchment area cause a natural flow of sediment in the waterway. Man-made barriers allow to modulate the water flow for use, but often constitute a total barrier for sediment. 
     The sediments accumulated in the reservoirs create a series of problems:
         decrease the water volume that can be modulated in the basin;   if near the barrier, they create hydrostatic pressures higher than those of project;   if near mechanical operating devices (intake valves, gate valves) they can compromise their perfect functioning;   if near the main outlets of hydroelectric plants, they can enter and damage the wheels of the hydraulic turbines, causing serious damage.       

     The sediments management therefore has a not insignificant importance in the series of operations that affect the good management and maintenance of a water reserve. In particular, the second and third problems concern aspects related to safety, as can be easily understood. 
     In the years, various techniques have been refined that solve the age-old problem of sediment management, and the techniques developed so far can be classified as follows: 
     a) Sediment floating with water through the bottom discharge organs. This is feasible if the quantity of sediments is known and there is no risk of a “vortex that obstructs” the intake, a catastrophic event. So the probability of the event must be very low (−106). Such maneuver is feasible only if there are no limits to the protection of the fish fauna present downstream of the barrier. Such maneuver is not controllable, it is not possible to manage the dosage of sediments during floating. 
     b) Floating downstream of the barrier through a tube which sucks the sediment on the seabed and discharges it by gravity downstream. This is feasible only if there are no limits to the protection of the fish fauna present downstream of the barrier. Such maneuver is similar to dredging, operated with mechanical means similar to dredgers. 
     c) Removal of sediments with mechanical means with an empty basin. Very expensive operation because it interrupts the service of the basin and impacts with the problem of “where to place thousands of cubic meters of very wet material”. 
     d) Removal of sediments with dredge. Normally quite expensive operation that often requires special means, small dredgers that require trained companies, floating pipes, mobile selection plants that operate campaigns that are often do not solve the problem, but only operate in emergency situations. 
     On the sideline, engineering solutions can also be mentioned, that can be defined as preventive and very expensive, sometimes introduced years after the construction of the basin, such as the construction of tunnels that intercept the sediments upstream of the basin and convey them downstream, and the sanding canals construction upstream of the basin. 
     Purpose of the present invention is therefore a dredging system which is capable of operating in situations where the dimensions or drafts do not allow the use of known dredging devices, and which can operate with an extremely reduced use of personnel, offering against a high action efficacy, both with large sediments and with substantially sandy sediments. 
     Object of the present invention is therefore a system for dredging underwater sea-beds comprising:
         a platform provided with flotation means, a dredging tool being provided on the portion of said platform facing the surface of the water, provided with means suitable for lowering and lifting it, and being provided with at least three connection points associated with said platform, with the ends of respective warping cables, suitably anchored to the shore at the opposite ends, and provided with suitable tensioning means;   sediment collection means collected by the dredging tool,   means for detecting the absolute position of said platform;   means for detecting the position of said dredging tool;   means for detecting the seabed configuration;   means for detecting the quantity of sediment removed from the seabed;   remote command and control means of said means suitable for lowering and lifting said dredging tool, tensioning means of the warping cables, and detection means;   means for supplying the equipment on board the platform.       

     In one embodiment, the dredging tool is a bucket; this tool is used when the sediment has heterogeneous and in any case unpredictable dimensions; in this case the collection means comprise an underwater hopper which discharges the sediment to the ground, and the platform is moved from the sediment collection point to the unloading area where said hopper is located. The platform, in its portion facing the surface of the water, will be equipped with a screen wall that surrounds the clamshell; the means for detecting the amount of sediment removed in this case comprise a load cell coupled to the bucket lifting means, which comprise a winch mounted on the upper portion of the platform. 
     In an executive variant, the dredging tool is a dredging pump, and is used when the sediment is smaller than 40 mm in average diameter; the sediment collection means comprise a floating duct. In this case, the platform only moves in the sediment collection area. The pump is preferably an electric pump, powered by the supply means connected to the platform. Means for detecting the mass flow rate of the dredging pump are provided. 
     Means for tensioning the warping cables can be provided on board the platform, just as they can be positioned on the ground. These tensioning means comprise winches, which provide means for detecting the tension of the warping cables, typically of the load cells. 
     Advantageously, said winches are made with a pulling part, comprising two drums that wind the cable for a few turns and on a single layer, and an accumulating part, comprising a drum with a larger diameter than the first two, which wraps the cable at very low tension, a motorized pulley being provided upstream of the two traction drums which keeps the cable under constant tension. On each operating winch of the warping cables, means for detecting the cable tension are provided, in the form of suitably positioned load cells. 
     Command and control means comprise a suitable software loaded on a computer, which is interfaced with the tensioning means of the warping cables, with the means for detecting the load of sediments removed by the dredging tool, with the detection means the position of the dredging tool, with the means for detecting the position of the platform, which typically will include a GPS device. Optical detection means will also be provided, such as video cameras, both surface and submerged, and wind detection means, such as anemometers, and detection of the wave state of the water surface, such as accelerometers. 
     In particular, both the warping cables and the lifting and lowering winch of the dredging tool are numerical control machines. 
    
    
     
       Further advantages and characteristics of the system according to the present invention will become clear from the following description of some embodiments of the same yield, by way of non-limiting example, with reference to the attached drawings, in which: 
         FIG. 1  is a top plan view of a first embodiment of the platform system according to the present invention: 
         FIG. 2  is a side elevation view of the platform of  FIG. 1 ; 
         FIG. 3  is a top plan view of a second embodiment of the platform system according to the present invention; 
         FIG. 4  is a side elevation view of the platform of  FIG. 3 ; 
         FIG. 5  is a schematic diagram of a first embodiment of the system according to the present invention; and 
         FIG. 6  is a schematic diagram of a second embodiment of the system according to the present invention. 
     
    
    
       FIG. 1  shows a first embodiment of the platform system according to the present invention;  1  indicates the platform, with a triangular shape, which is connected to each of the corners to a float  201 , while in the center there is the carter  101  which houses the lifting and lowering means of the dredging tool, not visible in the figure. 
       FIG. 2  is a side elevation view of the platform of  FIG. 1 ; to the equal parts correspond to the same numbers. The figure shows the bucket  2 , surrounded by the screen  301  which is connected to the platform  1 ; the flaps  211  protruding from the floats  201  which allow their connection to the platform  1  are also visible, in addition to the flaps  221  which instead allow the connection of the platform  1  to the warping cables, not shown in the  figure. 20  indicates the surface of the water. 
       FIG. 3  shows a second embodiment of the platform system according to the present invention; the same parts correspond to the same numbers: in the figure, the platform  1  has winches  3  mounted at each of the corners for tensioning the warping cables, not shown in the figure. Said winches  3  comprise a tensioning pulley  103 , two cable pulling drums  203  and a cable storage drum  303 . 
       FIG. 4  shows the platform of  FIG. 3  in side elevation; to equal parts correspond to the same numbers. The figure shows that in this case the dredging tool is the dredging pump  4 , which is lowered to the bottom by means of a winch, not visible in the figure, housed in the carter  101 . The floats  201  are coupled together by means of the crossbar  231 . 
       FIG. 5  shows a first embodiment of the system according to the present invention. Platform  1  is positioned on the body of water  20  enclosed in the portion of shore 21, in correspondence with the sediment accumulation zone  22 . The warping cables  406  are connected to the three platform corners, in correspondence with the three floats, which at the opposite end are coupled to a respective winch  6 , of the type described with reference to  FIG. 3 . Platform  1 , which uses as a dredging tool the bucket  2 , is connected through the umbilical cable  81  to the generator  8 . On the platform there are also all the sensors necessary to control the system, namely the sensors for detecting the position of the platform, the sensors for detecting the load of the bucket, the sensors for detecting the wave motion of the body of water, the sensors for detecting the wind, the means of displaying the seabed. Instead, the cable tension sensors  406  are mounted on the winches. As shown in figure, the remote command and control unit  30  is connected to all the active elements of the system. Near the shore there is the hopper  7  for unloading the sediment collected from the clamshell. 
       FIG. 6  shows a second embodiment of the system according to the invention; to equal parts correspond to the same numbers. In the figure it can be seen that in this case the warping cables  403  are equipped with fixed anchors  10  on the bank  21 , while the end connected to the platform  1  cooperates with the winches  3  of the type described in  FIG. 3 . In this embodiment the dredging tool is the dredging pump  4 , which is equipped with the discharge conduit  91  which pours the sediment into the container  9 . In this case most of the active components of the system, as listed in the previously described embodiment, are placed on the platform, and are, in the same way as previously described, interfaced with the command and remote control unit  30 . 
     The functioning of dredging system according to the present invention will be evident from the following. Once the anchoring has been operated, whether by winches  6  of  FIG. 5  or by the static anchors  10  of  FIG. 6 , the platform is positioned on the body of water, and the position of the sediment  22  is detected by means of suitable displaying means. At this point, in both cases, the dredging tool is lowered, which takes the sediment. In the case of bucket  2 , the load cell placed on the lifting winch indicates the quantity of material removed from the bottom, and consequently the command can be given which allows the transfer of the platform from the pick-up station to the sediment collection hopper  7 . Once the unloading is complete, the platform will position itself in the most suitable position to carry out the subsequent removal of material, and so on until all the sediment present on the bottom is removed. 
     Instead, in the case illustrated in  FIG. 6 , the dredging pump, once lowered, sends the sediment, which in this case is of a finer nature and in any case less than 40 mm in diameter, to the floating discharge duct, which pours it into the container collection. The platform will gradually be moved to the area where sediment  22  is present until its complete removal, without needing to be brought ashore during operations. 
     Advantageously, the winches used on the ground or on the platform are manufactured with a pulling part and an accumulation part of the cable. This design strategy satisfies the need not to have cables pressed from the upper layers, ensuring a good durability of the same, avoiding dangerous tangles of the cables on the drum, lethal in the case of an unattended system like this. The pulling part consists of two drums that wrap the cable in well-sized grooves, for a few turns and only with a layer of cables. The cable that leaves the pulling part is accompanied, now with very low tension and under control, to the accumulating drum. The latter, with a larger diameter, wraps the cable at very low tension, avoiding crushing and therefore also tangling. Upstream of the pair of traction drums there is a motorized pulley which tensions the cable constantly, so that in case of abandonment of the load, no accidental overlaps of the same are created. 
     The dredging cycle, in both cases, can be programmed taking into account: the configuration with geodetic references of the basin and the sediments deposited; of the mechanical characteristics of the sediment such as to be able to choose the best dredging tool suitable for this purpose; operating characteristics of the dredging system, such as the translation speed, the flow rate of the dredging pump, the volume of the bucket. It will also be possible to program operating cycles such as to allow the automatic removal of the sediment by optimizing the paths and removal according to criteria of good practice. 
     The command and control unit, connected remotely, for example via radio, wifi, or similar systems, with the float and with any winches on the ground allows the system to operate. Positions, speeds and accelerations of the maneuvering and lifting winches can be controlled manually, semiautomatically, automatically, in a manner very similar to how the tools of machines commonly called numerical control are controlled.