Ch. 9] FOUNDATION STUDY TOOLS 171 



lies in the scientific study and interpretation of nature as applied to 

 civil engineering. It is not important whether these men call them- 

 selves engineers or geologists. The real requirement is that they be 

 both. 



FOUNDATION STUDY TOOLS 



The foundation study for any highway structure should consist 

 fundamentally in determining the proper methods of applying loads 

 to earth materials in amounts that will not result in excessive settle- 

 ment or failure. If the structure is to span a stream, additional con- 

 sideration must be given to insure against structural failure due to 

 scour in the channel or erosion of the banks. 



It is of prime importance that field parties charged with the deter- 

 mination of foundation requirements be equipped with the modern 

 tools of their trade. 



Hole-boring tools capable of penetrating and sampling all types of 

 earth material to any required depth are an essential part of foundation 

 study equipment. In most cases it is desirable that boring tools be 

 power-operated and at the same time sufficiently light and portable 

 as to insure access to sites located in areas of troublesome relief. The 

 boring equipment should be capable of drilling rotary wash boreholes 

 up to 3 inches in diameter and to depths of about 200 feet. Contrary 

 to the general opinion among engineers, wash boring is by no means 

 a worthless technique in so far as its applications to foundation studies 

 are concerned. It is the writer's experienced opinion that borings of 

 this type furnish valuable information at the lowest possible cost per 

 lineal foot when properly conducted under the close observation of 

 adequately trained personnel. This technique, when used in conjunc- 

 tion with spot sampling of the significant horizons, may in some cases 

 fulfill all the requirements of an adequate study. This is particularly 

 true in areas where the geology is well understood or where an ex- 

 perience has been gained by observing the performance of existing 

 structures within a geologic provenance. The drilling machine should 

 in addition be equipped with bits, core barrels, and samplers capable 

 of the efficient penetration and sampling of earth materials regardless 

 of type or depth. 



A small drop hammer or other suitable device is required for the pur- 

 pose of driving casing, penetrometers, and sediment samplers. Al- 

 though light drop hammers are in general use for this purpose, it has 

 been demonstrated that small-diameter undisturbed samples show less 

 disturbance when samplers are forced into the sediment by means of a 

 steadily applied hydraulic or screw-activated push or by a rapid, ex- 



