2 BULLETIN 789, U. S. DEPARTMENT OF AGRICULTURE. 



D = diameter of bin or diameter of inscribed circle in feet. 

 H"= height in feet of grain above point in question. 

 n' = coefficient of friction of grain on bin walls. 

 W= weight of grain in pounds per cubic foot. 

 F= vertical pressure of grain at depth H in pounds per square foot. 

 L = lateral pressure of grain at depth H in pounds per square foot. 



L 



Tc = -y-= ratio of lateral to vertical pressure. 



e = base of Naperian logarithms. 



Note. — Both V and L are assumed to be constant at all points on 

 a horizontal plane. 



y_RX Wf _1 X 



For round and for square bins or other bins of the form of a regular 



A D 



polygon, the hydraulic radius p is equal to -r- and the formula becomes 



y DX W 



(1 ^XfcXM'-g I 



en/ 



4:XJcXfJL'^ 



VALUES OF m' and fc. 



Numerous experiments have been made with various grains in bins 

 constructed of different materials to determine values for the factors 

 ix' and li. The results of several of these experiments are given in 

 the appendix. 



PRESSURE FACTORS FOR WHEAT IN ROUND OR OTHER REGULAR 



CONCRETE BINS. 



By taking /x' equal to 0.4167, an average value for wheat on con- 

 crete, and Tc equal to 0.6, an accepted value for wheat in concrete 

 bins, the product 4 X it X m' becomes equal to 1 .0, and with Tf equal 

 to 50 pounds, the formula simplifies to 



v=^qxd(i — \- 



or -^^ = 50 

 and ^ = 0.6^ 



^ eis/ 



