is a closed and non-flow through system, as shown in Figure 6.7(a) (Sheng and 

 Lick, 1979; Fukuda, 1979; Sheng, 1981). A contained flow system is 

 necessary since mechanical parts such as a pump may disrupt the sediment floes 

 and change the particle size distribution. The flume has a rotating top plate 

 driven by a motor. The rotation causes a shear flow in the flume which in 

 turn yields an applied shear stress on the bottom sediments. Variation of 

 bottom shear stress with the rotational speed of the lid is shown in 

 Figure 6.7(b). Entrainment of cohesive sediments from fresh-water 

 environments (Table 6.1) and Mississippi Sound (Table 6.2) have been studied. 

 Effects of (1) bottom shear stress, (2) properties of bed, (3) salinity of 

 overlying water, and (4) sediment type on entrainment have been investigated. 

 The primary interest was on the rate of entrainment, rather than just the 

 critical shear stress at which initial entrainment occurs, as a function of 

 various parameters. 



Other Studies 



In addition to us, several other investigators have conducted laboratory 

 studies on the entrainment of cohesive sediments in the past. A few examples 

 will be given here. Partheniades (1962) and Krone (1962) studied the 

 entrainment and deposition of San Francisco Bay mud in a recirculating flume 

 of rectangular cross-section. Raudkivi and Hutchinson (1971) used a highly 

 compacted kaolinite clay at sea water salinity for their entrainment study. 

 Christensen and Das (1973) studied the entrainment of kaolinite and grundite 

 in a circular brass tube of 2.54 cm diameter. However, they and Partheniades 

 both primarily used a remolded bed in their respective studies. Ariathurai 

 and Arulanadon (1978) used a rotating annular cylinder, 10.2 cm in diameter 

 with 1.3 cm wide annular space, to study the entrainment of consolidated 

 sediments composed of 70% silica flour. Partheniades and associates have 

 carried out some illuminating experiments in a rotating annular flume similar 

 to the one used by us. Until very recently, they have primarily concentrated 

 on the depositional behavior of cohesive sediments. More recently, Mehta and 

 Parthaneides (1979) studied the erosional behavior of kaolinite in distilled 

 water. Several others have performed laboratory studies on entrainment and 

 deposition of various sediments in a wide variety of facilities with varying 

 measuring devices and techniques. These variations make the intercomparison 



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