THE IRRIGATION AGE. 



pressure, but at an angle :!5, it should be multiplied by the 

 secant of 35. 



1,984,375X 1-22=2, 420,937 Ibs. 



This strain is met by two walls having a total cross-sec- 

 tion of 17.5 feet. Each foot will, according to Kidder (p. 227, 

 Architect's and Builder's Pocket Book), resist 440,000 Ibs., 

 without reinforcement. 



17.5 X 440,000 = 7,700,000. 

 The factor of safety, then, is 

 7,700,000 



- = 3 approx. 

 2,420,937 



Figuring the bottom 10 feet in the same manner, we find 

 a factor of I 1 /?. The average will be about 2J4. It is more 

 important to have the top of the dam supported by the arch- 

 ing effect than the bottom, because in this case the bottom is 

 short and so wedged in between cliffs that it is abundantly 

 secure. 



The factor of safety in the buttresses alone is 8. As the 

 dam could not yield in one way without yielding in the other, 

 it is proper to add these two factors of safety together, mak- 

 ing a total of 10, r -4, which will be increased about 12% by the 

 reinforcement (Total, 16) and an unknown amount by the 

 earth filling. 



U 



z 



o 



(J 



z 



o 



