CHAPTER XI 



FOUNDATIONS AND RETAINING WALLS* 



158. Bearing power of soils. Since the character of a foundation 

 is dependent upon the nature of the soil on which it is to rest, it is 

 necessary in designing a foundation to know with a reasonable degree 

 of accuracy the maximum load which the soil can sustain per unit 

 of area without appreciable settlement; or, in other words, what is 

 known as the bearing power of the soiLf 



Ordinarily the results of previous experience are relied upon to 

 give an approximate value of the bearing power of any given soil, 

 and stability is assured by the adoption of a large factor of safety. 

 For structures of unusual importance, however, or when the nature 

 of the soil is uncertain, the results of previous experience are usually 

 insufficient to assure stability, and special tests are necessary for the 

 determination of the bearing power of the soil in question. Among 

 notable structures for which such special tests have been made may 

 be mentioned the State Capitol at Albany, N.Y. ; the Congressional 

 Library at Washington, D. C. ; the suspension bridges at Brooklyn, N. Y., 

 and at Cincinnati, Ohio; the Washington Monument; the Tower 

 Bridge, London, etc. 



By averaging the results of a large number of such tests, reliable 

 information is furnished as to the bearing power of soils in general. 

 The most commonly accepted of such average values are those given 

 by Professor I. O. Baker in his Treatise on Masonry Construction, and 

 are as shown in the table on the following page. Other values in 

 common use are also quoted for comparison, and may be accepted as 

 representative of modern practice. 



* For a more detailed treatment of foundations and retaining walls the following 

 special treatises may be consulted. Baker, Treatise on Masonry Construction; Howe, 

 Retaining Walls for Earth; Fowler, Ordinary Foundations; Merriman, Walls and 

 Daiw; Patton, Ordinary Foundations. 



t The bearing power of soils is analogous to what is called the crushing strength in 

 the case of more rigid materials, such as stone and brick. 



10.-, 



