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<br />TGle 2:. Fluid Xatrix: Cbaxaoteristioll <br /> <br />Landslide <br /> <br />Solids <br />concentration <br />by Volume <br />C. <br />>64% <br /> <br />Solids' <br />Concentration <br />by Weigh~: <br />C. <br />>8a% <br /> <br />Type of Flow <br /> <br />Flow Characteristics <br /> <br />'Will not flow; failure by block <br />sliding or tumbling. Unsaturated <br />soil conditions. <br /> <br />Landslide <br /> <br />50'-64% <br /> <br />73\-88% <br /> <br />will nl)t flow; block sliding fail- <br />ure wi.th some internal deforma- <br />tion, slow creep prior to failure; <br />saturated. <br /> <br />Mudflow <br /> <br />45'-50' <br /> <br />69'-7n <br /> <br />Flow initiates; plastic deforma- <br />tion ...7ith slow sustained creep. <br />Begins spreading; moves subject to <br />repeated vibration. <br /> <br />Mudflow <br /> <br />40%-45\ <br /> <br />65%-69% <br /> <br />Mixes easily; shows some fluid <br />properties. Surface may be in- <br />clined at rest. Welves dissipate <br />rapidly. <br /> <br />Mud flood <br /> <br />35'-40' <br /> <br />59%-65\ <br /> <br />spreacls on horizontal surface; <br />marked particle set:tling, liquid <br />horizontal surface, two-phase <br />separation in quiescent conclition; <br />waves travel easily. <br /> <br />Mud flood <br /> <br />30'-35' <br /> <br />54%-59% <br /> <br />Sand and gravel set:tle; distinct <br />wave action. <br /> <br />Mud flood <br /> <br />20%-30% <br /> <br />41%-54% <br /> <br />Particles rest on bottom .in wave <br />motion. <br /> <br />Water flood <br /> <br /><20t <br /> <br /><41% <br /> <br />Water flood with bed and suspended <br />load. <br /> <br />(From O'Brien, 1986) <br /> <br />The viscosity of hyperconcen.trated sediment flows is a <br />function of the properties of the j'lui.d matrix including sediment <br />concentration, percent and type of silts and clays, and fluid <br />temperature. viscous mudflows have high sediment concentrations <br />and correspondingly high yield strElSSeS and may result in laminar <br />flow. Less viscous flows such as mud floods are always turbulent. <br />The relationship between viscosity, yield stress and sediment <br />concentration by volume has been determined by laboratory <br />experiment (Figs. 1 and 2 and TablE!1 3, O'Brien and Julien, 1988). <br /> <br />Noncohesive sediments in suspension, even in moderate amounts, <br />do not influence the flow behavior as long as they do not interlock <br />and strengthen the mass. Research has demonstrated that increasing <br />the noncohesive sediment concentrat.ion (up to an additional 20 <br />percent volume) has little effect on the fluid matrix properties <br />(O'Brien and Julien, 1988). Concent:rations greater than 20 percent <br />of noncohesive sediments can incur significant momentum transfer <br />from the flow core to the boundary through particle collision and <br />interference. <br /> <br />6 <br />