Results 



The objective of the NCEL laboratory program was qualitative and 

 attempted to provide a visual representation of the soil-pile interac- 

 tion behavior. To that extent, the objective was met. The only param- 

 eter measured was the driving energy, which was correlated with the 

 parameters of void ratio, cementation, and carbonate content. 



Regarding the selected range of cementation levels, the findings 

 indicated that the calcareous sand practically reached an indurated state 

 where the bulk soil sample cracked and behaved as cemented chunks. The 

 influence of the state of induration on the material behavior was not, 

 therefore, outside the testing boundary of slight to medium cementation. 

 Any effects due to this parameter would be seen. For silica sand, this 

 stage was reached at the 2% cementation level, therefore, tests on the 

 4% and 8% cementation for silica sand were not conducted because of this 

 finding. 



Figures 6 through 13 show complete suites of x-rays for selected 

 soil models. All points in each x-ray were computer digitized to reduce 

 the data for comparing the various behaviors. Table 4 summarizes the 

 total driving energy for each soil model tested. Figures 14 through 16 

 show the variation between cementation, carbonation, and void ratio. 

 Based on the model study at NCEL the following observations were made: 



1. The amount of calcareous sand in a sample appeared to control 

 the amount of resistance the soil mobilizes during pile driving for dense 

 soil samples. Figure 14 shows that for the dense models containing 100% 

 silica sand, the slope of the input energy curve was larger than samples 

 containing 100% calcareous sand. The slope of input energy for similar 

 dense models containing 50% silica sand and 50% calcareous sand resembled 

 the 100% calcareous sand model slope. This became evident when the loose 

 density curves were analyzed in Figure 14. All the curves show that 

 input energy increased with cementation, however, each one shows a dif- 

 ferent slope. Closer examination shows that the total energy slopes of 

 the loose density mixtures appear linear and as the composition of the 

 model changed so did the rate of energy. That is, as opposed to dense 

 soil model, the amount of calcareous sand does not control the amount of 

 resistance the soil mobilizes during pile driving. 



2. The pullout resistance parameter was not measured in this test. 

 It was noted during the test that the calcareous sand's pullout resis- 

 tance did not appear to increase with increased driving energy, nor did 

 it increase with increased cementation. Contrarily, the pullout resis- 

 tance for silica sand increased substantially with increased cementation, 

 and at the higher cement contents the pile was very difficult to remove 

 from the sand model. This suggests that calcareous sand's driving energy 

 is independent of pullout tension. 



3. Figures 15 and 16 show the horizontal and vertical movement of 

 the lead shot pellets relative to their distance from the pile surface. 

 Several general observations can be made: 



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