CHAPTER X. 

 FOUNDATIONS. 



THE generic term, Foundations, comprehends both the 

 soil and the materials upon which a structure is designed to 

 rest; the line of demarcation or termination of the founda- 

 tions and commencement of the substructure is variable, but 

 in general the approximate ground-line is the limiting point. 

 More exactly, every foundation may be regarded as having 

 two components the bearing-soil, or subfoundation, and the 

 foundations proper, consisting of the materials intended to 

 form a solid base for the superstructure. 



The preparation of the natural soil for suitable sub- 

 foundations demands as wide a consideration and treatment 

 as the wide difference of geological conditions, but in practice 

 an intimate knowledge of the varying soil characteristics is 

 not possible or hardly necessary, and it is considered suffi- 

 cient to contrast the given soil with one or more of the more 

 common formations whose qualities are determined from long 

 experience. Such typical formations are rock, clay, gravel 

 and sand, and alluvial soils. 



Rock. Discussing these in the order named, the best 

 natural subfoundation is rock, in classification varying from 

 the crystalline types to soft-deposit specimens, easily water- 

 worn or subject to atmospheric disintegration, for experi- 

 ence has shown that any stone formation, well bedded, will 

 safely sustain any load that may be imposed upon it by any 

 masonry foundation, even for the largest structures. 



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