SILOS IN STONE AND BRICK 207 



Pressure Exerted by Ensilage on Walls of Silo. — The outward or 

 lateral pressure of cut mealie silage when settling increases propor- 

 tionately to the depth below the surface of the silage. Thus at 15 feet 

 from the surface it is about 165 lbs. on each square foot of wall surface, 

 while at a depth of 30 feet it is twice as much, or 330 lbs. on each square 

 foot. For this reason the walls of silos must be very strong. 



Form of Silo. — In the circular form, the materials are best disposed 

 to resist the above outward or bursting pressure, which in this case is 

 resisted by tensile stresses set up in the walls. This form also allows 

 of better packing or consolidation of the silage because of the absence 

 of corners. 



Stone and brick silos are frequently built of square shape (in plan) 

 on account of less skill being required than in the building of a round 

 silo. Square silos also fit in better with other buildings. The interior 

 corners of a square silo should be well rounded so as to impede settling 

 and consolidation of the mass as little as possible. 



Weight of Silage to be Stored. — In calculating the weight of silage 

 to be stored, the usual, basis is to allow 40 lbs. per cow per day, though 

 for a mixed herd, and when other food is available, the allowance per 

 head per day would be considerably less. Taking the figure 40 lbs., the 

 total weight to be stored in short tons will equal the number of animals 

 to be fed multiplied by the number of clays during which they have to 

 be fed, multiplied by 40 and divided by 2000. 



Cubic Capacity of Silo. — To find the capacity in cubic feet of a 

 rectangular pit silo, or of a square or rectangular tower silo, multiply 

 together the length, width, and height, each expressed in feet. This 

 neglects the slight loss of capacity due to rounding the interior corners. 



Thus the silo illustrated is 14 feet square by 30 feet high, its capacity 

 is therefore 14 x 14 x 30 = 5880 cubic feet. 



To find the capacity in cubic feet of a circular silo, multiply the 

 square of the diameter in feet by the height, also in feet, and the product 

 by 07854. 



Total Weight of Silage Stored in a Silo. — This is found by multi- 

 plying the capacity of the silo in cubic feet by the average density or 

 weight per cubic foot of the silage. 



According to King, the average density may be taken as 36*5 lbs. 

 per cubic foot for a silo 25 feet deep, and 39*6 lbs. per cubic foot for 

 a silo 30 feet deep. 



