148 philbbick. FOUNDATION PROBLEMS [Ch. 8 



of sedimentary rocks these problems are framed and reduced to more 

 understandable terms. 



Foundation problems can be reduced from numerous individual 

 problems to two general problems the correct solution of which is 

 paramount to the successful completion of any undertaking involving 

 foundations. These may be phrased in many ways, but they boil 

 down to two questions of which the first is always present and the 

 second may be present: 



(1) Will the foundation rock support the load? 



(2) Will the foundation rock leak? 



The answers to these questions may be automatically affirmative in 

 rare cases, but in general the development of proved answers will re- 

 quire the expenditure of considerable money, effort, and thought. It 

 is toward the reduction of these expenditures that the following re- 

 marks are directed, inasmuch as the writer believes that foundation 

 problems can be classified rationally in relation to the type and mag- 

 nitude of the structure and its geologic environment. There is a pat- 

 tern in the foundation problems which he has met in the cyclic sedi- 

 ments of the Pennsylvanian of the Appalachian Basin, just as there 

 is another pattern in the calcareous sediments of the Tennessee Val- 

 ley, another pattern in the Permian sediments of the Mid-continent 

 area, and another in the Cretaceous and Tertiary sediments of the 

 upper Missouri Valley. 



These comments are restricted to the rocks as we find them, with- 

 out regard to the processes which developed their present characteris- 

 tics, unless such processes are continuing and will affect the rocks ap- 

 preciably during the lifetime of the proposed structure. This chapter 

 considers briefly the types of foundations, the problems of determin- 

 ing the physical character of the foundation rock, and the problems 

 arising from the geological character of the several types of sedi- 

 mentary rocks. 



FOUNDATIONS 



A satisfactory foundation must support the load imposed upon it. 

 The requirements of support may include resistance to compression, 

 shear, sliding, and maintenance of cohesion despite repeated freezing 

 and thawing and wetting and drying. Commonly adhesion to con- 

 crete is required. In addition to supporting properties, the founda- 

 tions for hydraulic structures, such as locks and dams, must be rela- 

 tively impermeable or be such that they can be feasibly and econom- 



