Suction Dredges Research Articles

Cutter Heads of Suction Dredges for Underwater Excavation

Results on development and adaptation of cutter heads with wear-resistant cutting edges for suction dredges are discussed. Original technical solutions for the cutting edges and replaceable teeth are described. The complete line of cutter heads for various types of soil is presented, including their geometrical, kinematic and power parameters

Kra Canal (Thailand) excavation by nuclear-powered dredges

Partial excavation of a Kra Canal in Thailand by nuclear-powered cutter-head suction dredges is examined. Such automated digging by a floating machine is deemed economically and geologically feasible. International and intranational commerce will be benefited greatly as will the residents of peninsular Thailand. The 26 December 2004 tsunami (particularly at Ko Phuket on the Andaman Sea coast) indicates that more offshore and seaboard geological investigations must be carried out to ensure safe operation of the Kra Canal. Dredge spoils, if selectively sorted, have an unknown economic value in terms of heavy mineral mining potential. After the construction of the Kra Canal, the nuclear-powered dredges may find permanent useful work in the Malacca Strait, Sunda Strait and in the Gulf of Thailand or be used elsewhere.

Development and implementation of domestic suction dredges with submersible pumps

One of the main directions in upgrading suction dredges is equipping them with submersible dredge pumps.

Disturbance of intertidal soft-sediment benthic communities by cockle hand raking

Recent awareness of the ecosystem effects of fishing activities on the marine environment means that there is a pressing need to evaluate the direct and indirect effects of those activities that may have negative effects on non-target species and habitats. The cockle, Cerastoderma edule (L.) is the target of a commercial and artisanal fishery that occurs in intertidal and estuarine habitats across Northern Europe. Cockles are harvested either mechanically using tractor dredges or suction dredges or by large numbers of individual fishers using hand rakes. This study examined the effects of hand raking on the non-target species and under-sized cockles associated with intertidal cockle beds and the effects of size of the patch of sediment disturbed on subsequent recolonisation. Hand raking led to an initial three-fold increase in the damage rate of under-sized cockles compared with control plots. The communities in both small and large raked plots showed community changes relative to control plots 14 days after the initial disturbance. The small raked plots had recovered 56 days after the initial disturbance whereas the large raked plots remained in an altered state. Samples collected over a year later indicated that small-scale variations in habitat heterogeneity had been altered and suggest that while effects of hand raking may be significant within a year, they are unlikely to persist beyond this time-scale unless there are larger long-lived species present within the community.

Improving the wear resistance of suction dredges

1. An industrial procedure for electrofacing by a powder wire of special composition has been developed to produce a wear-resistant coating up to 5 mm thick on the components of suction dredges. An increase of 4–6 times is achieved in the time to failure of the faced components, while the cost of these operations does not exceed the price of the initial article. 2. It is expedient to use the facing procedure to strengthen new components under plant conditions and to restore worn parts at the site where the suction dredges are operated. The Scientific-Production “Spetsstal'” can perform work on electrofacing with the required materials, equipment, and technical accompaniment, and organize the strengthening of components at the plant. 3. The installation of a three-channel suction dredge with effective water protection of components from abrasive wear while eliminating overflow of slurry into the pump and increasing the efficiency of the unit on the whole is proposed. The proposal is recommended for development and implementation.

Output of suction dredges with respect to solids

Quite brief operation of the suction dredge and its pipeline on clear water permits determining the minimum value of the head being developed by a given dredge, and all subsequent heads during its operation with mixtures permit, with consideration of other factors (as indicated), determining the amount of solids being transported by water through the pipeline at a given time and during any time period in tons or cubic meters.

Experience in tunnel burial with suction dredge

1. The method described here for later burial (after laying) of tunnels with suction dredges has proved to be quite effective. Despite the wide diversity of conditions affecting burial technology for underwater pipelines (resting on the bottom of waterways or inadequately buried), the technology in question can serve as the basis for pipeline burial with suction dredges under conditions different from those described here. 2. Burial of tunnels that are first laid on the bottom of waterways (before trenching) or that have been inadequately buried is particularly expedient in rivers with unstable channels (e.g., the Amudar'ya and others), where a great deal of time elapses between digging of the trench and lowering the underwater pipeline into it, since the excavation process is strongly dependent on conditions. 3. When a tunnel is buried in the bottom of a waterway by the technology under consideration, the trench volume excavated and hence the amount of material moved is less by a factor of several tens (about 40, judging from foreign experience) than that for a trench dug before the pipeline is laid. This is the main reason why working with suction dredges is comparatively inexpensive.

Effects of Suction-Dredge Gold Mining on Benthic Invertebrates in a Northern California Stream

Abstract The effects on benthic invertebrates of mining with two suction dredges were investigated in 1983 by using artificial-substrate samplers in Big East Fork Creek, a tributary to Canyon Creek in northern California. The samplers were placed in Big East Fork Creek above and below the dredge site and in Canyon Creek above and below the confluence of Big East Fork Creek. The effects of dredging on invertebrates varied with taxa and were site-specific at the level of dredging during the study. Total numbers of invertebrates that colonized samplers and their diversity indices did not differ significantly between Big East Fork and Canyon creeks or above and below dredges in either creek. Numbers of invertebrates peaked earlier in samplers below the dredges. In Big East Fork Creek, shredders were more abundant above than below dredges, whereas gatherers were more abundant below dredges. Filterers rapidly colonized samplers below dredges and were later displaced by siltation. Shredders were more abundant ab...

Effects of Suction Gold Dredging on Fish and Invertebrates in Two California Streams

I examined the impact of small suction dredges (hose diameter, <16 cm) on fish and invertebrates in two California streams (North Fork of the American River and Butte Creek) in a 2-year study. I studied both the effect of one dredge (1980) and the effects of an average of six dredges in a 2-km section of stream (1981). Ten replicate Surber samples per station were taken monthly to compare macroinvertebrate abundances at control and dredged stations before, during, and after dredging in both years. Dredging significantly affected some insect taxa when substrate was altered. A recolonization experiment showed that numerical recovery of insects at dredged sites was rapid. Mask-and-snorkel censuses and observations of tagged fish indicated that major changes in available habitat caused local decreases in fish density. Dredging affected riffle sculpins (Cottus gulosus) more severely than rainbow trout (Salmo gairdneri), probably because of differences in microhabitat requirements. Local turbidity increases below active dredging probably did not affect invertebrates and fish.

Classification of soils according to the difficulty of their excavation by suction dredges (discussion of construction specifications)

Classification of soils according to the difficulty of their excavation by suction dredges (discussion of construction specifications)

Suction dredge excavation of large canals with suspended sludge pipes used to place the earth in dumps

1. The technical parameters examined here for constructing, large canals by floating suction dredges with suspended sludge pipes in water-filled soils in areas difficult to traverse, taking into account a dry mass up to 10–15 m above, the water table, demonstrate that this canal driving method is promising. 2. The possibility of a deep echeloned arrangement on very long canals being excavated makes it possible to drive them quickly, using for this purpose the minimum number of erection bases. 3. The minimal excavation volumes in each driving stage in the canal substantially reduce the volumes of preparatory and attendant work. In particular, depending on the soil particle size, the work volumes for construction of the operation embankments amount to no less than 3–6% of basic work volume. 4. The construction—technical basis of suction dredges with suspended sludge pipes, which for all practical purposes eliminates the dependence on bank work, makes it possible to a considerable extent to increase the suction dredge efficiency because of a higher coefficient of utilization. 5. For reliable control of the general process of canal excavation and hydraulic-fill placement of the soils in the dump, it is necessary to maker provision for different lengths of the suspended sludge pipe, which can be achieved thanks to sectional construction.

Soil classification according to difficulty of excavation with floating suction dredges

Soil classification according to difficulty of excavation with floating suction dredges

管内濃度を自動調節しうる吸込装置を用いた厚層砂層の採取に関する模型実験

This paper propounds a new suction dredge. The points knowing this suction dredge from regular suction dredges are in a special suction-head attached to the forward end of a suction pipe joined to a sand pump, in a venturi-type detector of concentration in the suction pipe, and in the mechanism of automatic control for concentration.The structure of the special suction-head may be mentioned as follows. A body finding a shape in which circumferences of two circular cones (or convex surfaces) stick together mutually is fixed in the inside of a conical suction pipe, with keepingth e suitable space between the body and the conical suction pipe, and a mouth is at the center of the convex bottom surface of the body.In the suction-head, the convex bottom comes in contact with sand bed. When pressurized water is poured through the mouth into the sand bed, the sand bed of some thickness under the suction-head causes phenomenon of quick sand, and the suction-head may suck up sand of quick sand state. As a result, the suction-head goes down due to its own weight, and may suck up sand falling down about circumference of the suctionhead.When flow of the pressurized water stops in the suction, the suction-head also stops going down into the sand bed, and sucking up sand.The automatic control for concentration in pipe in pumping up sand-water mixture from the sand bed is done by on-off operation of the flow of the pressurized water, and upward and downward movements of the suction-head in a vertical line, which are controlled by signal of concentration in pipe being out-put of concentration meter.This paper discusses theory of operation, static characteristics, and dynamic characteristics of the dredging of loose and thick sand bed by means of the suction dredge.The tests of the laboratory model of the suction dredge built as a trial showed that automatic control for concentration in pipe is done successfully.

Determination of the magnitude of water hammer in pipes of suction dredges

Determination of the magnitude of water hammer in pipes of suction dredges

Damming without embankments of the Dnepr River at the site of the Kanevsk hydroelectric plant

1. The experience here described confirmed the possibility of damming large rivers, without constructing embankments, at hydraulic developments, by placing fine-grained sands by hydraulic dredges. This method of damming river channels is especially convenient if in the project region the rock and rubble material are obtained from quarries located at great distances. 2. The method of damming river channels without using embankments permits closing off a narrow passage, within a short period, by constructing a hydraulic-fill dam by means of suction dredges, without employing floating cranes, pontoon bridges, or other auxiliary equipment. 3. When damming a river channel without constructing embankments, a discharge channel with a small drop should be constructed and a sufficient volume of sand capable of being adequately handled by suction dredges should be supplied. 4. For the construction of river-channel earth dams with very wide bases (and gentle slopes on the downstream side), the method of damming the channel without constructing embankments by placing local soils can save large volumes of rock and rubble. 5. The damming of the Dnepr River at the site of the Kanevsk hydroelectric plant permitted saving 54,000 m3 of rock and 17,000 m3 of rubble; the total economy resulting from the damming of this river without constructing an embankment was 750,000 rubles.

Suction dredges

Suction dredges