driving would meet these goals. By varying the soil media's consistency 

 (i.e., density and degree of induration), the different behaviors of the 

 calcareous sand during model pile embedment could be compared to a con- 

 trolled sand (silica sand) having similar consistencies. The behavior 

 difference and the influencing factors were more clearly defined. 



Program 



The model selection criteria used for this experiment required that 

 the model be manageable in the laboratory and be free of as many labora- 

 tory induced effects as possible yet provide the desired results. A 

 technique had to be developed that would allow a view of the change 

 occurring in a soil mass as a pile was driven into the soil without in- 

 fluencing its behavior. The solution to the problem was found by using 

 radiography. Radiography is expensive to use because of the equipment 

 and the special accommodations required to conduct the experiment and 

 provide against x-ray exposure. The method, therefore, is not commonly 

 used. Nevertheless, a GE 250, 5 Ma, 210 k.V power apparatus normally 

 used for nondestructive testing was available at the Aeronautical Me- 

 chanical Prototype Support Branch at the Pacific Missile Testing Center, 

 Point Mugu, Calif. 



Radiography provides an image of an object subjected to x-rays. An 

 exposed film, sensitive to x-rays, shows the internal structure of the 

 object and highlights areas of high density. High density material will 

 either absorb the x-ray or slow down their transmission time. Since the 

 film is exposed to an x-ray source for a predetermined length of time, 

 the high density areas projected onto the film is contrasted relative to 

 the surrounding material. After exposure no residue radiation is present 

 since lead shielded walls surrounding the objective area absorbs all 

 x-ray scatter instantly. 



Applying the radiography principal to the calcareous sediment model 

 study helped to select the laboratory components. They included a ply- 

 wood box (6 by 12 by 24 inches deep), lead shot pellets, and a steel 

 model pile (24 inches long by 1-1/2 inches diam) . Other ancilliary 

 equipment such as assorted driving weights, templates for lead shot 

 placement, and a pile guide for vertical penetration were provided (see 

 Figure 2) . 



Test Materials 



Two test materials were used for this study: (1) calcareous sand 

 and (2) silica sand. Calcareous sand is not abundant in the continental 

 United States and the most likely area to find the material is in Florida. 

 In the past, abundant supplies of the sand were available on beaches 

 located in the Florida Keys as well as southernly beaches on the mainland. 

 However, many of these beaches have been expanded with imported silica 

 sand, thereby, contaminating the source. Also, silica sand is used on 

 eroding beaches, which is another cause of contamination. Fortunately, 

 a clean source of calcareous sand was located at the Key West Naval Air 

 Station. An abandoned fort, located on the base, had rooms filled with 

 100% calcareous sand. Several cubic yards of the sand were shipped to 



