General Dredging
Bucket dredgers generally adopt vertical excavation (that is, along the channel direction) construction, which can be divided into downstream dredging, countercurrent dredging, strip dredging, segmental dredging, layered dredging and other methods according to different construction conditions. :
(1) Under normal circumstances, the bucket dredger should adopt downstream excavation, mainly to prevent the grab from colliding with the hull. Countercurrent construction is used in areas with low flow velocity or reciprocating currents;
(2) When the designed trench width is larger than the effective dredging width of the dredger, the strip dredging method is adopted. The principle of slitting is to slitting from the center to both sides, every adjacent two have overlapping to prevent missed digging, the maximum width of slitting shall not be greater than the effective working radius of the dredger;
(3) When the thickness of the mud layer is greater than the maximum dredging depth of the dredger grab, the layered dredging method is adopted. The layering principle is that the upper layer should be thicker and the lower layer should be thinner so as to improve the dredging effect and ensure the quality of dredging;
(4) Sectional construction shall be carried out when the length of the trench exceeds the excavation length that the dredger can excavate by throwing the main anchor at one time. The section length is easy to take 60-70m. [2]
Quincunx
For the situation where the soil is soft and the thickness of the mud layer is not large, in order to improve the work efficiency and ensure the quality of the project, the plum blossom-shaped dredging method is often used, that is, there is a certain interval between the buckets, so that the excavated mud surface is For plum-shaped pits, in the actual construction, according to the size of the water flow and the softness of the drawings, the distance between the buckets should be reasonably determined, and the excavation depth should be well controlled.
top beach dredging method
Both the upper and lower reaches of short excavated trenches in the shoal are limited by the construction draft, and the construction cannot be carried out along the shoreline, so the top beach dredging method must be used. Use the high tide level to excavate a trench forward in layers without stranded mud barges. When the tide falls, the dredger moves to the starting point for excavation. The bucket dredger and the mud barge shift gears to each other. When the high tide level is reached, the excavation continues in layers. , and wait until the tide ebbs again, if it does not affect the draught of the mud barge, you can continue to dig or dig the next layer. If the dredging continues, the draft of the barge will be affected until the dredger and the barge are shifted to each other, and the dredging is completed by this method.
Ridge dredging method
When the water depth permits, the dredging method is adopted to advance in order by jumping one level and retreating one level, which is called the dredging method of leaving ridges. That is, after digging the first level, enter the third level, after digging the third level, retreat to the second level, and after digging the second level, jump to the fifth level. This kind of digging method, when the first, third, and fifth levels are dug, the second and fourth levels left behind are soil ridges, which are easy to grasp and dig.
slope excavation
bucket dredgers cannot excavate relatively flat slopes through the driver's operation like cutter suction dredgers, so they can only adopt layered excavation methods, relying on water flow to affect natural collapse and finally form slopes. The excavation height of the steps should be 1.0-2.5m. The excavation of the slope should not only consider the ultra-wide value, but also consider the adaptability of the grab bucket to the dredged soil and rock, so the excavation depth becomes smaller as you go down, and the height of over-excavation should be greater than the height of under-excavation; for the convenience of excavation, the step division The layer is preferably approximately the same as the main dredging layer, and the specific data needs to be calculated.