Ch. 8] INSOLUBLE SEDIMENTARY ROCKS 159 



economics of the project were not materially affected. Such could 

 not be permitted in a foundation containing gypsum or salt. As a 

 matter of good practice the intent of all grouting and waterproofing 

 treatment of foundations is to reduce leakage to the absolute minimum 

 feasible under the circumstances. The problems involved in control- 

 ling leakage require the determination of the location, extent, and size 

 and interconnection of actual and potential channels of leakage, and 

 the means of cleaning and closing off or filling these channels. The 

 solution of these problems requires the application of many geologic 

 techniques including detailed investigation of the sedimentary features 

 of the rock (Moneymaker, 1941). 



CLASSIFICATION OF SEDIMENTARY ROCKS 



The sedimentary rocks may be separated into innumerable types, 

 depending upon their chemical composition, geologic history, mode of 

 deposition, grain size, primary structure, texture, and mineralogical 

 composition. However, in relationship to foundations they may be 

 grouped into two broad classes: soluble rocks and insoluble rocks. The 

 insoluble rocks include rocks composed of essentially insoluble minerals 

 bonded with generally insoluble cement in which naturally cavernous 

 conditions do not occur. Examples of this type of rock are sandstone, 

 siltstones, shales, indurated clays, mudstones, claystones, coal and 

 other carbonaceous rocks. Soluble rocks include limestones, dolomites, 

 and evaporites in which cavernous conditions have occurred or may 

 occur. Soluble and insoluble rocks may be closely associated as in an 

 interbedded sequence. The determination of appropriate classifica- 

 tion depends on the extent of past or potential solution and its in- 

 fluence on the type of foundation problem. The typical association of 

 insoluble and soluble rocks is the interbedding of shales and limestones. 

 Another condition, less recognized from the standpoint of foundations, 

 is the cyclic deposition found in the Carboniferous rocks of the Ap- 

 palachian and Interior coal basins of the United States where non- 

 marine and marine sediments contain limestones as well as insoluble 

 members. 



Insoluble Rocks 



Insoluble rocks can be separated into rock types based primarily 

 on their grain size, mineralogical composition, cement, and frequency 

 of bedding. The foundation problems of these rocks depend almost en- 

 tirely on the physical properties of the rock which are closely related to 

 the foregoing geologic characteristics. Except for the siltstones of the 



