Construction preparation
① Meteorological collection
Collect the forecast of the next five days and the sea conditions of the construction area, and arrange the construction reasonably according to the weather and sea conditions.
② Measurement before dredging
Before dredging, the surveyor shall use the sounder to measure the original mud surface, and the drawing plane and sectional drawing shall be kept.
③Ship and aircraft preparation
Prepare grab dredgers, mud barges, tugs, and transport vessels.
④Handling the relevant approval documents of water and underwater construction operations.
2. Establish the dredging plane grid
During construction, dredging is positioned according to the established small grid of construction area. The position of each grab corresponds to each small grid, and the dredging is constructed in turn according to zoning and ship.
3. Rough positioning of dredger
The dredger will enter the water area of the construction site through the marking set by the anchorage. After seeing the dredger entering the planned construction area on the computer display screen in the dredger operation room, the dredger shall immediately cast the bow and stern eight-shaped anchor in accordance with the appropriate marking position that has been set.
4. Accurate positioning of dredger
After the completion of the dredger rough positioning, through the computer screen, commanded by the operator, accurate positioning of the dredger, the dredger accurate positioning in the construction area of the specific dredging site, and tighten each cable. On-site CPS(centimeter-level accuracy) is used for checking, and the dredging operation can be carried out only when the error is within the allowed range.
5. Mud barge mooring the dredger
The self-propelled mud barge should approach the side of the dredger slowly under the command of the commander.
6. Dredging method
The grab bucket dredging adopts the method of "horizontal digging wider, vertical digging longer".
7. Slope dredging
Slope. The excavation site of the slope should not be smaller than the design size, so it is impossible for the grab bucket to dig out the branch slope. Therefore, the layered step excavation should be carried out according to the principle of "the bottom is over and the top is under, and the balance is over and under", and finally the design edge 8 is formed. Dredging stratification and trough bottom elevation control
Longitudinal excavation according to the dredging sequence, transverse stratification excavation, if using a large grab, with a bucket of digging depth 2 as the layer, so as to avoid the soil field into the dug pit.
8. Mud barge loading, transporting, and throwing mud
(1) After dredging, the dredged mud is loaded onto the mud barge, and the mud barge is fully loaded after sailing to the mud throwing point for mud throwing.
(2) The stone material produced by reef blasting is transported to the upper material dock by landing craft, and the stone material is used to backfill the rear area, instead of discarding the mud point.
9. Dredge anchoring, lifting, and shifting
① Cast anchor and weigh anchor
Grab dredger anchoring and lifting anchor are commanded by special personnel. It is necessary to understand the current flow and speed of the anchor area and the situation of seabed anchor holding in advance. The anchoring should be the first cast toward the upstream direction of the anchor, and then lose the cable and then cast downstream direction of the anchor; On the contrary, hoist the downstream anchor first, take the tug, and anchor upstream again. Each anchoring position shall be determined by technicians in advance according to the length of dredging position and cable length and anchored under the command of the captain.
② Move the ship in a small range
The horizontal and vertical movement of dredger in the same dredger area is a small range of ship movement, grab dredger is mainly by wringing, putting anchor cable to complete; When stranding and releasing anchor cable cannot meet the requirement of moving ship, anchor boat should be used to move the anchor to dredger so that the dredger can be moved by stranding and releasing anchor cable in a new range.
③ Move anchor in a large range
For the grab dredger to move from one dredging area to another dredging area, it is a large-scale shift. For the large-scale shift, all the wrong cables should be packed up and dragged to the new dredging area with the tow wheel for re-casting. All casting locations are calculated and determined in advance to maximize efficiency and avoid repeated starting and anchoring.
After the end of anchor wringing and in the process of construction, the anchor cable should be inspected frequently. Measures should be taken in time if the anchor is loose and the ship's position should be redetermined to ensure the accurate positioning of the ship.
10. Construction records
Before dredging construction to establish a good and dredging construction area grid diagram of different sections dredging grid to dredging handlers, dredging un-experienced operator must always indicate the finish on the grid map the location of the area, such as dredging, completes the detailed construction records on the grid map, in order to prevent leakage in the process of each class job handover to dig and repeated construction.
11. Survey acceptance after dredging
After the harbor dredging is completed, the unit with grade A qualification of surveying and mapping (issued by the National Geographic Information Bureau of Surveying and Mapping Association) is commissioned to conduct a 1:1000 sea sweeping survey with a multi-beam sounder and submit a qualified water depth map. 13. Marine dynamic environmental monitoring
In the process of dredging and dredging construction, a qualified monitoring unit is entrusted to monitor the Marine dynamic environment at the dredging site and mud dumping site to ensure that the construction environmental protection meets the requirements.
