Ch. 9] FOUNDATION STUDY TOOLS 173 



far steel piles would penetrate, or perhaps the feasibility of supporting 

 the load by means of friction piles. These answers might well have 

 been obtained by driving penetrometers at a few selected locations 

 throughout the structure site; the resistance offered to penetration 

 could have been observed, and, after appropriately spaced time inter- 

 vals, periodic pull tests designed to measure skin friction values could 

 have been conducted. Test pits in large numbers and to great depths 

 have been dug after the inability to penetrate a deposit of loose 

 boulders and gravel to bedrock depth by means of available drilling 

 equipment has been established. This discovery is usually made after 

 at least one of every type of drill bit available has been destroyed 

 in the attempt. Refraction seismic equipment or certain electrical 

 geophysical apparatus could have revealed the answer for a mere 

 fraction of the expended time, energy, and money. Although current 

 researches have not resulted in the ultimate with regard to applying 

 geophysical techniques to mantle exploration, much progress has been 

 made in recent years, and the future looks very hopeful (conference 

 with Dr. Thomas Poulter, January 1949) . 



In addition to equipment capable of solving the drilling, penetrating, 

 and sampling requirements of a foundation study program, it is equally 

 important that the field party conducting such studies have available 

 sufficient testing apparatus to permit on-the-job measurements of im- 

 portant physical characteristics of the sediment. 



Pumping tests should be conducted in drill holes or wells in cases 

 where footing foundations are to be situated below the water table or 

 where high permeability is likely to exert a major influence on the 

 builders' operation. Quick shear or unconfined compression tests or 

 both, when conducted in the field, often give results that may influence 

 or control the conduct of the entire study program. Percent voids, 

 unit weight, moisture content, the consistency limits, and grain-size 

 classification can, and should, be determined in the field. This pro- 

 cedure not only develops better-trained personnel but also places 

 sampling and testing directly on a job-requirement basis. It is not 

 suggested that all laboratory-type testing be done in the field. Tri- 

 axial shear, time consolidation, petrographic analysis, and most chemi- 

 cal tests require permanent laboratory facilities and can be properly 

 conducted in no other place. 



Since the advantages offered in the form of checks on both dynamic 

 measurements and the judgment of the engineering geologist far out- 

 weigh those of permanent laboratory facilities for certain measure- 

 ments, field testing is strongly recommended whenever feasible. 



