168 



POWER-HOUSE DESIGN 



Foundation. The most important part of the building is the 

 foundation, and careful soundings must be made to ascertain the 

 underlying strata. If bedrock is found within moderate depth, 

 the foundation should be carried down to the same. For all soils 

 there is a certain safe bearing load, and if this is exceeded the 

 structure supported thereby is apt to settle. The safe loads 

 usually allowed in this country are given in the following Table 

 XXXVI. 



TABLE XXXVI 



SAFE BEARING POWER OF SOILS 1 



1 From " Treatise on Masonry Construction," by Baker. 



For the machinery foundations it is considered good practice 

 to use somewhat lower values. About one-half is a good working 

 basis for such work, thus allowing a maximum load of about 1000 

 pounds per square foot for ordinary alluvial soils. Clean, sharp 

 sand is considered to be a good bearing soil, and may only be 

 necessary to cover it with a concrete mat, which requires a mini- 

 mum of concrete. For soft or alluvial soils piling is almost always 

 required. The piles may be of wood, although in the last few 

 years much use has been made of concrete piles, both plain and 

 reinforced. Such piles are less apt to decay and their bearing 



NOTE. A complete bibliography on the subject of- " Bearing Value of 

 Soils " is contained in the Proceedings of the American Society of Civil Engi- 

 neers for August, 1917. 



