Results 



The results of the triaxial shear tests are presented in Table 5. 

 The results show that the friction angle of the calcareous sands was 

 about 10 degrees higher than that of the Ottawa sand. This was true for 

 both sands in loose and dense conditions. The range of variation of 

 friction angle of these calcareous sands from loose-to-dense condition 

 was narrow. The increase in friction angle from loose-to-dense condition 

 was only 3 to 4 degrees for both sands. The high friction angles of the 

 calcareous sands tested were not due to dilational behavior during 

 shearing. In the loose condition, both sands showed volume decrease, 

 yet had friction angles in the range of 44 to 46 degrees. 



Some particle crushing occurred during shearing of these calcareous 

 sands in the triaxial compression tests (Figure 20) . When additional 

 tests were made on the crushed sand, the amount of further crushing 

 during shear was substantially reduced. 



The friction angle of these calcareous sands decreased as the con- 

 fining pressure was increased. At a confining pressure of 8,000 lb/ft 2 

 the amount of reduction in <f> value for calcareous sands was 2 to 4 de- 

 grees. Even partially crushed sand showed some reduction in the <J> value 

 when tested under high confining pressures. 



Tests on the crushed and recompacted calcareous sands indicated 

 that the crushed sand was not weaker than the natural sand. When the 

 friction angle of natural sand at a given void ratio was compared with 

 the friction angle of partially crushed or ground calcareous sand at the 

 same void ratio, it was found that they were about the same value 

 (Table 5). 



The results of isotropic compression tests indicate that the calcar- 

 eous sands tested are more compressible than the Ottawa sand (Figure 21). 

 This could be due to the presence of intraparticle voids, and crushing 

 of the sharp edges and corners of highly irregular particles. 



The results of the soil-steel friction tests are presented in 

 Table 6. These data indicate that for the two calcareous sands, the 

 soil-steel friction angle appears independent of soil density, and in- 

 creased slightly after crushing. For the Ottawa sand the friction angle 

 is independent of soil density. No tests were done with crushed Ottawa 

 sand. 



CRUSHABILITY 



The behavior work performed by NCEL provided a clearer understanding 

 of the soil-pile interaction, and a better understanding of the crushing 

 phenomena. However, answers to questions such as the location and extent 

 of crushing relating to various cementation levels and void ratios, and 

 what effect crushing has on driving energy and pullout tension would 

 provide a better understanding of the overall soil-pile interaction and 

 the shear transfer mechanism operating in calcareous sands. To study 

 these questions, NCEL awarded a contract to ERTEC Western, Inc., Long 

 Beach, Calif. 



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