There should be enough water to fill the voids, so the particles of sand rub against each other, dramatically increasing the apparent viscosity as the shear rate increases. Other materials that exhibit this type of behavior are concentrated (especially deflocculated) aqueous suspensions of china clay, titanium oxide, corn flour, and wet cement aggregates. Viscoplastic fluids are those that appear to show a "yield stress." That is, a certain amount of shear stress must be applied to the material before it can begin to flow, or deform. Whereas in fact it seems that if flow is measured over a wide enough range of shear rates, no yield stress really does exist,5 the concept of a yield stress remains very convenient, because a number of materials do closely approximate to this type of behavior.
If the material is being sheared but at less than the yield shear stress (Ryield), then the material will deform "elastically" and flow as a rigid body and not like a fluid. The classic example of this type of
If the material is being sheared but at less than the yield shear stress (Ryield), then the material will deform "elastically" and flow as a rigid body and not like a fluid. The classic example of this type of
