TWI525236B - Dredging vessel and method for loading the dredging vessel with dredged material - Google Patents

Description

Dredger and method for loading dredger with excavated material

The present invention relates to a method for loading a dredger with excavated material. The invention likewise relates to a dredger which is particularly equipped for carrying out the method of the invention.

During excavation with a dredger such as a towed dredger, the excavation material and the mixture of water are sucked up in a known manner through a drag head that is connected to a suction duct and Moving over the bottom of the water, and the excavated material is carried through an inlet into the cabin (or mud chamber) of the dredger until it is completely filled. The maximum fill height of the hold is determined by the height position of an overflow that is present in the cabin of the dredger and forms an open connection with the water, for example through the underside of the dredger.

The heavier excavation material particles collected in the cabin will settle after a period of time, and thus a more or less densely packed precipitate of coarser particles will be formed in the cabin, which will proceed with the excavation And increase the height. A non-precipitating layer of substantially finer particles that float freely in the water is formed on top of the precipitated layer. In the known method, the overflow opening is placed in the highest position so that the cabin can be filled with the greatest possible possibility and to prevent non-precipitated particles from re-entering the water through the overflow opening. Non-precipitated particles must be avoided when they enter the water again through the overflow port, because the chance of water becoming turbid is increased too much. This has an adverse effect on the flora and fauna at this location.

The level of the excavated material/water mixture that is sucked up reaches the upper side of the overflow port, and the mixture returns to the water through the overflow port. However, during the overflow, the draught of the dredger may still increase due to an increase in the number of heavier particles while the mixture of finer particles and water disappears through the overflow. In this known method, the overflow port continues to remain in the highest position for a while until the dredger that towed the suction mud tank has reached its maximum allowable draft (also known as the excavation mark). From this moment on, the excavation mark remains fixed by selectively reducing the overflow. The excavation system ends when there is no further net precipitation of the material. The same amount of material then disappears through the overflow as it is added to the cabin. Depending on, for example, the flow of water, the excavated material/water mixture entering the water through the overflow can be re-precipitated (falling back to the bottom of the water), eroded (falling back onto the water and then carried away by the water stream) and/or transported (by the water stream) Carry away without precipitation). As described above, it must be ensured that the turbidity of the water is not allowed to increase too much.

Although the known methods are carried out with maximum excavation efficiency, in particular the quality of the excavated material that cannot be immediately controlled to be deposited in the cabin needs to be improved.

The present invention has been made in an effort to provide a method for loading a dredger with excavated material which does not have such and other disadvantages, or which has a lesser degree of disadvantage. Another project is to provide a dredger that is specifically equipped for this improved method.

This item is achieved according to the invention by providing a method of loading a dredger with excavated material in a cabin provided for this purpose and having a highly adjustable overflow port in which excavation The material/water mixture is carried into the cabin through an inlet, and because the precipitation of heavier excavation material particles forms a sediment layer therein, and the height position of the overflow port above the sediment layer is adjusted to The value of one of the control variables measured during the filling of the cabin. It has been found that by defining appropriate control variables, the quality of the excavated material deposited in the cabin can be advantageously influenced. This can be understood as follows. Contrary to known methods, in the method according to the invention, at the beginning of the excavation, the overflow opening will not be placed in the highest position but in a lower position. The excavation material mixture, and in particular the finer portion of the excavation material mixture (due to the heavier partial precipitation), will then overflow through the overflow at a relatively early stage after the excavation has begun. It has been found that by adjusting the height position of the overflow, the average particle size of the excavation material mixture overflowing through the overflow may be affected, and thus also affecting the excavated mixture remaining in the rear of the cabin. Average particle size. The precipitated material obtained in this way has a well-controlled particle size distribution, in particular a higher average particle size and/or a narrower particle size distribution than in the case of known methods. Such materials have improved quality. The method of the present invention has the additional advantage that the degree of contamination of the excavating material and/or overflowing excavated material in the cabin can be affected. The height position of the overflow port is preferably set at an instantaneous value of the control variable.

A preferred embodiment of the method is characterized in that the height position of the overflow opening above the sedimentation layer can be adjusted such that the measured value of the control variable continues to remain substantially constant. This embodiment allows for the acquisition of excavation material remaining behind the cabin with a predetermined desired average particle size.

A control variable for the use of a particularly suitable method in the method according to the invention comprises an average horizontal velocity of the excavating material/water mixture which is non-precipitated above the sediment layer between the inlet and the overflow. It has been found that this control variable is highly sensitive to the average particle size of the excavation material mixture overflowing through the overflow, and therefore the average particle size of the deposited excavation material remaining behind the cabin is also very high. Sensitivity. In the case where the overflow height above the sedimentation layer is fixed, it is found that, for example, at a higher average horizontal velocity, the higher average particle size of the excavation material mixture is washed away through the overflow. The typical average horizontal velocity of the non-precipitated excavating material/water mixture in the cabin is a total of 1 m/sec. However, the invention is not limited to such speed. The average horizontal velocity average horizontal velocity of the non-precipitated excavating material/water mixture in the cabin may preferably be in the range of 0.1 to 5 m/sec, preferably in the range of 0.3 to 3 m/sec, and most The ground is adjusted within the range of 0.5 to 1.5 m/sec.

The present invention is based on the insight that particles of excavated material carried into the cabin through the inlet will be partially deposited (precipitated) and form a sedimentary layer, and the intensity of the water stream generated above the sediment layer will be partially Erosion (falling back onto the sediment layer and then being transported away by the water stream) and/or will be carried away (carryed by the water stream leaving the overflow port without precipitation).

The horizontal velocity flow from the inlet to the overflow above the precipitation layer of the non-precipitating mixture can be measured in a simple manner by measuring the incoming flow rate of the adsorbed mixture and dividing it by the width of the mud chamber and the height of the non-precipitating mixture. Decide. This horizontal velocity is preferably compared to the average drop velocity of the solid particles in the mixture being sucked up. This drop speed can be easily determined experimentally, for example by precipitation. In principle, it is possible to determine in this way which particles will flow out through the overflow and which particles will settle at the set height (or the horizontal velocity of the mixture).

According to the invention, the average horizontal velocity < is preferably defined by the following formula:

Where Q is the flow rate of the excavated material/water mixture measured at the inlet location, B is the cabin width and h is the height position of the overflow above the sedimentation layer. The flow rate Q at the inlet location can be measured in a known manner by incorporating a flow meter in, for example, the inlet. The flow rate Q can be controlled by adjusting the dredging pump that draws the excavating material/water mixture from the bottom of the water.

A further preferred embodiment of the method according to the invention is characterized in that the height position h of the overflow opening above the sedimentation layer is adjusted to a substantially fixed value, and the flow rate Q is adjusted such that the average horizontal speed < can Get the value you want. The flow rate Q can be adjusted by providing feedback of the measured flow rate Q to the control device of the dredging pump that extracts the excavating material/water mixture from the bottom.

A preferred embodiment of the method according to the invention is characterized in that the flow rate Q is adjusted to a substantially fixed value (by pump control) and the height position h of the overflow above the sedimentation layer is adjusted The average horizontal speed is <take the desired value.

According to the invention, in the method according to the invention, the overflow opening is substantially not placed in the highest position when the dredging is started, but is placed at a lowest position of the overflow opening. The lowest position of the overflow corresponds to a low loading factor of the cabin, preferably 25%, more preferably 20%, still more preferably 15%, still more preferably 10% and optimally It is 5%. It will be appreciated that the lowest position of the overflow port will preferably not be lower than the level of the outside of the dredger, since otherwise the outside water may flow into the cabin.

Since the contaminants in the excavating material are substantially mainly bonded to the finer particles, for example, to particles having a size of <63 μm, and these contaminants are preferably discharged according to the present invention through the overflow port, the excavating material The precipitated layer contains less contaminants. Another advantage of the method of the present invention is that the smaller particles that are preferably discharged are generally more easily transported away with the water stream so that they do not precipitate, but instead are eroded and/or transported by It is transported away with the water stream. The method of the present invention provides the option of adjusting the size of the excavated material particles that are expelled through the overflow port such that such erosion and/or transport can occur in view of the intensity of the water flow at that location. In areas with strong water flow, it will generally be possible to discharge an average larger particle size through the overflow, which does not result in an unacceptable increase in turbidity. In areas where the water flow is weak, the overflow height will preferably be set such that the average smaller particle size of the excavated material is discharged through the overflow.

In a preferred embodiment of the method, the cabin is filled with water to the level of the overflow in the lowest position prior to the commencement of dredging. The excavating material/water mixture will therefore overflow almost through the overflow after the start of the dredging.

It is advantageous in the method according to the invention that the control variable is related to the height of the precipitation layer, and that the overflow port remains above the precipitation layer, and more preferably at a substantially fixed height above the precipitation layer. In such a variation, the overflow is displaced as if it were in conjunction with the height of the sediment layer, whereby the mixture having a controlled particle size distribution will continue to remain behind the cabin. The fixed height depends on the conditions at that location and can be determined experimentally if desired. It is also possible to reach an appropriate value for a fixed height based on theoretical considerations. The height of the precipitated layer can be measured in a number of ways. The easiest way is by measuring the dredger's draught and/or using a dipstick. However, it is also possible to apply other methods.

Still another preferred embodiment of the method has the feature that the control variable is related to the particle size distribution of the mixture of overflows near the overflow. The particle size distribution of the excavating material/water mixture can be determined in different ways. Suitable methods include concentration measurement by photography or photography, determination of particle distribution of samples taken by screening, and/or deposition scale, x-ray extinction measurement, light extinction measurement of one or more wavelengths, and/or by The role of sound waves.

The method according to the invention is preferably characterized in that the control variable is related to the density of the overflow mixture close to the overflow. This density can be measured in a manner known to those of ordinary skill in the art, for example by an extinction measurement. In such a measurement, a source is placed on one side of the mixture stream. One placed on the other side of the mixture flow (the detector measures the amount of radiation passing through the mixture. The detected (-radiation depends on the amount of solid particles between the source and the detection calculator) Devices for measuring density in such a manner are commercially available, for example from Berthold Technologies NV, Vilvoorde, Belgium.

In a particularly advantageous method, the turbidity of the overflow mixture close to the overflow is applied as a control variable. This turbidity can also be easily measured by the effect of the density measurement as briefly described above. Because the turbidity caused by the removal of sludge has a great ecological impact. Due to turbidity, less light can penetrate the bottom of the water. Flora and fauna that exist in the bottom of the water therefore have fewer opportunities for development. A very common requirement in dredging operations is that the turbidity during dredging cannot rise above 1000 mg per liter. The method according to the presently preferred variant provides the option of adjusting the height of the overflow such that the turbidity (increase) continues to remain below a predetermined desired value.

It will be appreciated that it is equally possible to apply the combination of control variables described above as control variables. The position of the overflow opening can thus be determined, for example, by a first approximation by the height of the sedimentation layer, wherein the correction for this first approximation is governed by the value of another control variable, for example, at the inlet and the overflow. The density of the mixture measured.

In order to even better control the particle size distribution of the overflow mixture, and thus also the particle size distribution of the precipitation mixture, the overflow port is preferably provided with a filter having a predetermined mesh width, preferably for effluent mixture The sampling purpose of the particle size distribution.

The invention likewise relates to a dredger suitable for carrying out the method according to the invention. Particularly provided is a dredger having a cabin having a height-adjustable overflow for loading with a digging material/water mixture, wherein the dredger is further provided for measuring a control variable The mechanism, and a control device that adjusts the height of the overflow port that is governed by the measured value of the control variable. The advantages of the dredger according to the invention have been explained in detail above with reference to the method of the invention and will therefore not be repeated here.

In a preferred variant of the dredger according to the invention, the measuring mechanism is selected from the group consisting of: a mechanism for measuring the height of the sediment layer, for measuring between the inlet and the overflow a mechanism for the average horizontal velocity of the non-precipitating mixture, a particle size distribution for measuring the particle size distribution of the sucked mixture near the inlet, and/or a particle size distribution of the overflow mixture close to the overflow port, for measuring proximity to the inlet a mechanism for the density of the mixture to be aspirated and/or the density of the overflow mixture close to the overflow, a means for measuring the overflow mixture close to the overflow and/or a turbidity in the water, or as described above A combination of measuring mechanisms.

With regard to a particularly advantageous preferred variant of the dredger, the measuring mechanism comprises a densitometer arranged at a position where the overflow mixture flows into the overflow opening.

The towed-type mud tank dredger according to the present invention comprises a ship 1 having a cabin 2 and a suction duct constructed from a loading pipe 3 entering and leaving the cabin 2; a pump 4; And a suction pipe 5 pivotable about a shaft 30 relative to the vessel 1 and having a trailing head 6 at its bottom end, the trailing head 6 being when the vessel 1 is sailing in the direction of arrow 9 It is pulled over the bottom 8 in the water 7, and the bottom material 16 of the sand, for example, is taken up with the water 7 as a suspension from the bottom via the suction pipe 5 and carried into the cabin 2. The trailing head 6 is provided with a cover panel 12 which is pivotable about a shaft 11 with respect to the trailing head 6 by the action of a hydraulic cylinder 13.

The cabin 2 is adapted to receive a mixture of subsea material and water that is drawn through the conduit 5 by the action of the pump 4. After a period of time, the mixture present in the cabin 2 will precipitate and form a precipitation layer 20 therein, the precipitation layer 20 having a height 40 relative to the bottom of the cabin 2. Present on the precipitation layer 20 is a layer 21 comprising an aqueous suspension non-precipitating bottom material. The height 41 of the layer 21 is determined by the height position of a height-adjustable overflow opening 10 having a conical upper outer end 14. The overflow opening 10 has an open lower outer end 15 in which the mixture overflowing in the direction of the arrow 31 along the lower outer end 15 can be dragged in the direction of arrow 32 via the bottom of the towed mud tank dredger The side is carried to the water 7.

The variant of the towed-type mud tank dredger according to the invention shown in Fig. 1 is further provided with means for measuring a control variable, the value of the height position of the overflow opening 10 being adjusted by the control variable. The measuring mechanism comprises a first densitometer 25 which is arranged near the inlet or the loading tube 3 and at which the density of the sucked mixture is measured. A flow meter 28 known per se is arranged at substantially the same position. This measures the flow rate of the sucked water, and the average horizontal velocity of the non-precipitated portion 21 can be determined from the flow rate. The densitometer contains a radioactive concentration meter available from Berthold Technologies N.V. of Vilvoorde, Belgium. A second densitometer 26 of the same type is disposed at the location of the overflow port 10 and measures the density of the overflow mixture. If desired, a third densitometer 27 can be placed in the water adjacent to the towed suction mud dredger to facilitate measurement of the turbidity of the overflow mixture or surrounding water. The signals from the measuring mechanisms mentioned above are stored in a central computer (not shown) which forms part of the control equipment for the towed suction mud dredger.

In a preferred method, the towed-type mud tank dredger described above is used to excavate materials present in the bottom of the water or on the bottom 8. In this method, the mixture of the underwater material and the water is sucked up via the tractor 6 connected to the suction pipe 5 and moved on the water bottom 8, and is carried into the cabin 2 via the inlet or the suction pipe 3. In the preferred method, the overflow port 10 is placed at the lowest position when the method is opened. This preferably corresponds to a cabin-based load factor is about 10% (m ³ can be obtained as a whole load) 2. In Figure 1, the lowest position of the overflow port 10 is schematically indicated by the top side 100 of the overflow port 10. At this position 100, a substantial amount of the sucked mixture will be carried through the overflow 10 in the direction of arrow 32 into the water 7 in the direction of arrow 31. This overflow is particularly finely formed by the mixture being sucked up because the thicker portion has moved below the level 100 under the influence of gravity and continues to remain behind the cabin 2 as the sediment layer 20. During the dredging, the height 40 of the precipitation layer 20 will gradually increase. In the variant shown, the height position of the overflow opening 10 is adjusted by the height 40 of the precipitation layer 20, which allows the overflow opening 10 to remain at a substantially fixed height above the precipitation layer 20. This means that the height 41 will have a fixed value during most dredging. The exact value depends on the conditions at this position and it totals for example 0.75 m. If the aspiration flow rate measured by the flow meter 28 remains fixed, the average horizontal velocity of the non-precipitated portion 21 will therefore also be substantially fixed.

Since the height 40 of the sediment layer 20 increases with time, the height of the overflow port 10 also rises until the overflow port 10 reaches the highest position 101. When the towed mud tank dredger has reached its maximum allowable draught or excavation mark, it reaches the highest position 101. This situation is shown in Figure 1.

The method of the invention is particularly suitable for excavating access passages for receiving water or other large extended water in urban areas, and/or for excavating sand, more preferably fine sand, and optimally containing sand. Fine silt. The sand has 65% by volume of particles larger than 63 μm and 50% by volume of particles smaller than 2. The fine sand has particles having a volume between 5 and 15% and a fine particle size of between 2 and 63 μm. Using the method of the present invention, more of the bottom material, and in particular its thinner portion, can flow back into the water with a low mud tank loading factor via the overflow port, as compared to the known methods. This so-called agitation procedure can be well controlled by the method of the present invention, which is a great advantage in terms of setting requirements for the turbidity of water. The thinner portion of the overflow can be carried, for example, into the sea by the flow of water entering the passage away from the location of the dredging operation. In addition to this, the material deposited in the cabin has a higher quality, so that it can be advantageously used for the supply of sand and the like, in the vicinity of the excavation position.

Figure 2 shows diagrammatically the particle size distribution (50) of the excavation material mixture obtained using the method of the invention and the dredger. The particle size distribution obtained is compared to the particle size distribution (51) of the excavation material mixture obtained using known methods. In the figures shown, the weight percentage (52) is plotted against the particle size (53). By overflowing a portion (54) of the particle size distribution (51) allowed to be supplied during excavation through the overflow port (10), the particle size distribution (50) obtainable not only has a narrow distribution but also has a ratio The size distribution of the supplied particles (56) is larger than the average particle size (55).

The present invention is not limited to the above-described exemplary embodiments, and they may be modified as long as they fall within the scope of the appended claims.

1‧‧‧ dredger

2‧‧‧ cabin

3‧‧‧Loading tube

4‧‧‧ pump

5‧‧‧Inhalation tube/catheter

6‧‧‧ drag head

7‧‧‧ water

8‧‧‧ bottom

9‧‧‧ arrow

10‧‧‧Overflow

11‧‧‧ shaft

12‧‧‧ hood

13‧‧‧Hydraulic cylinder

14‧‧‧ upper outer end

15‧‧‧ below the outer end

16‧‧‧Bottom material

20‧‧‧ Precipitate

21‧‧‧ layer/non-precipitated part

25‧‧‧First Density Meter

26‧‧‧Second Densitometer

27‧‧‧ Third Density Meter

28‧‧‧ Flowmeter

30‧‧‧ Spindle

31‧‧‧ arrow

32‧‧‧ arrow

40‧‧‧ Height

41‧‧‧ Height

50‧‧‧Particle size distribution of excavated material mixtures obtained by the method of the invention and by dredger

51‧‧‧Particle size distribution of excavated material mixtures obtained by known methods

52‧‧‧% by weight

53‧‧‧Particle size

54‧‧‧ Part of the supply particle size distribution 51

55‧‧‧Average particle size

56‧‧‧Supply particle size distribution

100‧‧‧ level on the top side of the overflow

101‧‧‧ highest position

The invention will now be further elucidated on the basis of the following drawings and description of the preferred examples, and the invention is not limited to the drawings and examples. In the schema:

Figure 1 shows a schematic side view of a dredger according to the present invention;

Figure 2 shows diagrammatically the particle size distribution of the excavation material mixture obtainable by the method of the invention and the dredger, as compared to the particle size distribution of the excavation material mixture obtained by known methods.

1‧‧‧ dredger

2‧‧‧ cabin

3‧‧‧Loading tube

4‧‧‧ pump

5‧‧‧Inhalation tube/catheter

6‧‧‧ drag head

7‧‧‧ water

8‧‧‧ bottom

9‧‧‧ arrow

10‧‧‧Overflow

11‧‧‧ shaft

12‧‧‧ hood

13‧‧‧Hydraulic cylinder

14‧‧‧ upper outer end

15‧‧‧ below the outer end

16‧‧‧Bottom material

20‧‧‧ Precipitate

21‧‧‧ layer/non-precipitated part

25‧‧‧First Density Meter

26‧‧‧Second Densitometer

27‧‧‧ Third Density Meter

28‧‧‧ Flowmeter

30‧‧‧ Spindle

31‧‧‧ arrow

32‧‧‧ arrow

40‧‧‧ Height

41‧‧‧ Height

Claims (12)

A method for loading a dredger (1) with excavated material in a cabin (2), the cabin (2) being provided for this purpose and having a height-adjustable overflow (10), one of which The excavating material/water mixture is carried into the cabin (2) via an inlet (3) and a precipitation layer (20) is formed therein due to precipitation of heavier excavation material particles, and wherein the sediment layer 20) The height position of the upper overflow port (10) is adjusted by a control variable value measured during the filling of the cabin (2), the control variable is interposed between the inlet (3) and the overflow The average horizontal velocity of the non-precipitating excavating material/water mixture above the sediment layer (20) between the ports (10) is related. The method of claim 1, characterized in that the height position of the overflow opening (10) above the precipitation layer (20) is adjusted such that the measured control variable values continue to remain substantially fixed. The method of claim 1, wherein the average horizontal velocity < is defined by the following formula: Where Q is the flow rate of the excavated material/water mixture measured at the inlet (3) position, B is the width of the cabin (2) and h is the height position of the overflow (10) above the sedimentation layer (20). The method of claim 3, characterized in that the height position of the overflow opening (10) above the precipitation layer (20) is adjusted to a substantially fixed value, and in that the flow rate Q system is adjusted so that The average horizontal speed < obtains the desired value. The method of claim 3, wherein the flow rate Q is adjusted to a substantially fixed value and the height position of the overflow port (10) above the precipitation layer (20) is adjusted such that The average horizontal speed < obtains the desired value. The method of any one of claims 1 to 5, wherein the control variable is further related to a particle size distribution of the overflow mixture adjacent to the overflow port (10). The method of any one of claims 1 to 5, characterized in that the control variable is further related to the density of the overflow mixture adjacent to the overflow port (10). The method of any one of claims 1 to 5, characterized in that the control variable is further related to an overflow mixture close to the overflow port (10) or a turbidity in the water (7). The method of any one of claims 1 to 5, characterized in that the control variable is a combination of the control variables described. A dredger provided with a cabin (2) having a height-adjustable overflow (10) for loading with a digging material/water mixture, wherein the dredger is further provided for A mechanism (25, 26, 27, 28) for measuring the control variable, the non-precipitating material/water above the sediment layer (20) between the inlet (3) and the overflow port (10) The average horizontal speed of the mixture is related, and a control device for adjusting the height position of the overflow port (10) with a value of the measured control variable is provided. Such as the dredger of claim 10, characterized in that the measurement The mechanism is selected from the group consisting of: a mechanism for measuring the height of the precipitation layer, a mechanism for measuring the average horizontal velocity of the non-precipitating mixture between the inlet and the overflow, and a means for measuring the proximity to the inlet. Mechanism for particle size distribution of the aspirated mixture and/or particle size distribution of the overflow mixture adjacent to the overflow port, for measuring the density of the sucked mixture near the inlet and/or the overflow mixture close to the overflow port The density of the mechanism, the mechanism for measuring the overflow mixture near the overflow and/or the turbidity in the water, or a combination of the measurement mechanisms described above. A dredger according to claim 11 is characterized in that the measuring mechanism comprises a densitometer arranged at a position where the overflow mixture flows into the overflow port (10).