Capacity of dredging pump is determined by its characteristics in case of sucking soil-water mixture, resulting dredging and transporting ability. Authers havbeen investigated the charcteristics of dimensionally similar pumps dealing with water and mixture through the practical and laboratory tests.
　In water test, characteristics at high suction vacum is deeply examined. Although a steep drop-point in head caused by cavitation was not recignized clearly on account of the capacity of the testing installation, suction specific speed could be estimated to be around 900, judging from a slight decreae in head at φ=0.0482 of head coefficient at 950 rpm.
　In mixture test, pump characteritics could be shown means of a rate of decrease or a rate of increase which is expresed on the basis of the term (ρm-1), or
KH=C1(ρm-1)n　　or　　KH=C1｛(ρm-ρws)/ρws｝n
KN=C2(ρm-1)n'　　or　　KN=C2｛(ρm-ρws)/ρws｝n'
Kη=1-(ρm-KH)/(1+KN)　　or　　Kη=1-(ρm/ρws)-KH/(1+KN)