FO UNDA TIONS. 2 2 5 



Weight of hammer in Ibs. X fall in inches 



Safe load in lbs. = ; ; ri f 



8 X penetration at last blow 



Applying this rule to a pipe driven with a 224<>lb. hammer 

 and penetrating, under a 2O-ft. drop, i inch, the safe bearing 

 in tons is found to be 33.6. 



This value would probably be considered too high. 



A formula in very general use is one given by Trautwine, 

 and is used with a factor of safety varying from one-half to twelve, 

 depending upon local conditions. This rule is 



Extreme ) Cu rt of fall in f t>Xwt o f hammer in Ibs. X 0.02 ? 



load in > = Y : y^ -. : r 



, I Last sinking in inches -f i 



Taking the same constants as above, the extreme load is 1 28.9 

 tons. Using a factor of four, the result is about as given under 

 the Sanders formula. Usually from 18 to 20 tons is considered 

 a proper load for a 1 2-inch pile. 



In piles supported by the friction along their sides, the 

 ultimate value of that friction is estimated at from .2 to I 

 ton per square foot of bearing for each foot of length, depend- 

 ing upon the soil characteristics. In silt or wet river-mud, 

 when driven three feet apart, the possible value of friction 

 upon unbarked piles is .5 tons per foot length. In New 

 Orleans, where the soil is a saturated alluvial for 900 feet 

 depth, piling is used for all building foundations where much 

 weight is to be imposed. In some of the larger buildings, 

 even with this addition to the bearing-values, considerable 

 settlement has been observed. A foundation designed for a 

 stand-pipe, 13 X 100 ft., in that locality, consisted of 100 

 piles, driven an average of 60 ft. deep, and spaced 2 ft. in 

 both directions. The piles were of unbarked cypress, aver- 



