Most other properties of littoral materials are more directly related to 

 concerns of soil mechanics rather than littoral processes (see Terzaghi and 

 Peck, 1967, Ch. 7, Sec. 7.7). 



Table 4-2. Density of littoral materials. 



Specific Gravity (dimensionless) 



Quartz 



Calcite 



Heavy Minerals 



2.65 

 2.72 

 >2.87 (commonly 2.87 to 3.33) 



Unit Weight^, kg/m^ (Ib/ft^) 



Uniform sand 



loose 



dense 

 Mixed sand 



loose 



dense 

 Clay 



stiff glacial 



soft, very organic 



Dry 



1442 

 1746 



1586 

 1858 



(90) 

 (109) 



(99) 

 (116) 



Saturated 



1890 

 2082 



1986 

 2163 



2066 

 1426 



(118) 

 (130) 



(124) 

 (135) 



(129) 

 (89) 



1 



From Terzaghi and Peck (1967). 



c. Fall Velocity . In considering the motion of littoral materials, a 

 particularly meaningful material characteristic is the particle fall 

 velocity, V^ . This is the terminal vertical velocity attained by an 

 isolated solid grain settling due to gravity in a still, unbounded, less dense 

 fluid. The fall velocity, usually for quartz in water, summarizes effects of 

 grain size, shape, and composition and of fluid composition and viscosity. 

 The ratio of fall velocity to characteristic fluid velocity has been widely 

 applied as a measure of sediment mobility or transport. 



For a sphere, the fall velocity 

 eral cur\ 

 the buoyancy index 



V 



fs 



can be expressed in the form of a 



to 



single general curve, for example, relating the Reynolds number (V^ d /v) 



where 



[(Y /c) -1] g d^ / 



S o 



7 = the specific gravity of the solid 



Y = the specific gravity of the fluid 

 g = the gravitational acceleration 



d = the sphere diameter 



s '^ 



V = the fluid kinematic viscosity 



(4-6) 



4-18 



