... hoppers are fired on the chained plate for cycling dredging and digging. The digging depth can be regulated ... , the extracted materials could be sand, stone and mud, and the diameters are 1-3 cm, 2-4 ... , dredger vessels, dry land sand washing machine and iron dredging ship have the same working principle.Various ... in panning gold, getting salt, cleaning mud and mining hard riverbed(the depth can reach 5- ...