196 



STBENGTH OF MATERIALS 



As an approximate working rule Trautwine recommends I'mm - 

 to 3 tons/ft. 2 as a safe load for compact gravel, sand, or loam, and 

 from 4 to 6 tons/ft. 2 if a few inches of settlement may be allowed.* 



The building laws of Greater New York may also be regarded as 

 competent authority, and specify the following values. 



As a supplement to the above, these laws also specify that when 

 foundations are carried down -through earth by piers of stone or 

 brick, or by concrete in caissons, the loads on same shall not exceed 

 15 tons/ft. 2 when carried down to rock, or 10 tons/ft. 2 when carried 

 down to firm gravel or hard clay. 



In order to obviate too large or expensive a foundation, it is often 

 desirable to increase the bearing power of the soil. This may be 

 accomplished in various ways. 



Since, in general, soils are more condensed at greater depths, 

 increasing the depth usually increases the bearing power of the soiL 



* Engineer's Pocket-Book, 1902, p. 683. 



