450 rhoades. CONCRETE AGGREGATE [Ch. 24 



conditions. A more striking series of alluvial cones and fans, typical 

 of arid regions, is illustrated in Fig. 3. 



Alluvial fans similar to those shown in Fig. 3 occur along the 

 Boulder-Kingman (Arizona) highway, and they were investigated in 

 connection with postconstruction activities at Hoover Dam. These 

 fans disclosed the following characteristics: (a) Individual particles 



Fig 3. Alluvial cones and fans formed under arid conditions near Muddy River, 



Nevada. 



are angular, having been transported quickly and only a short distance 

 from the source material, (b) The deposit is composed of a limited 

 number of rock types — those rock types that occur on the ridge at the 

 head of the dry washes, (c) All sizes, including the sands, are es- 

 sentially of the same composition, there having been no selective con- 

 centration of the more durable types. (The softer materials occur in 

 proportion approaching their original proportion in the parent rock.) 

 (d) The deposit is heterogeneous as to grading within layers and from 

 layer to layer. 



It was determined that this material would be suitable as concrete 

 aggregate if locations and levels were chosen to avoid extremely coarse 



