a. The motion of pellets in the calcareous sand model was 

 larger than in the silica sand models. Since the silica sand showed 

 more driving resistance, perhaps the calcareous sand required more move- 

 ment to mobilize its strength. 



b. The total motion in the cemented sand models was smaller 

 than in noncemented models. This suggests that cement bonding, although 

 small, was tying grains together causing the mass to respond more as a 

 unit. 



c. The motion of the lead shot was greater in the low void 

 ratio (dense) then in the high void ratio sand models. This was expected 

 because high void ratio sand compacts in order to mobilize its shear 

 strength whereas low void ratio sand transfers the shear load further 

 into the sand medium enabling the medium to mobilize more strength. 



d. The downward vertical movement of the high void ratio cal- 

 careous sand exceeded that of the silica sand. In the low void ratio 

 sand models, the majority of vertical movement was in an upward direction 

 suggesting that more particles were involved with producing a greater 

 mobilized strength. Furthermore, the increased upward vertical movements 

 of the low void ratio silica sand model indicated that this sand responded 

 more effectively and with higher strength to resist loading. 



FRICTIONAL BEHAVIOR TESTS 



A study (Noorany, 1982a) investigated the internal friction and 

 soil-metal friction of two calcareous sands, and evaluated the influence 

 of particle crushing on these properties. 



The study did obtain a clearer view of the frictional behavior of 

 calcareous sands with particular emphasis on the effect of particle 

 crushing on the internal friction angle, <t>, and on the soil-metal fric- 

 tion angle, 6. 



Test Plan 



First, the friction angle of each sand was measured by triaxial 

 compression tests in loose as well as dense conditions. Next, each cal- 

 careous sand was crushed and tested again to determine the effect crushing 

 had on the soil friction angle, <j>, in loose and dense states. 



The soil-metal friction was measured for both calcareous sands in 

 loose as well as dense conditions. The effect of particle crushing on 

 soil-metal friction angle was also investigated. 



For comparison, a silica sand was also tested. The results of the 

 tests were analyzed to evaluate the influence of soil crushing on shear 

 behavior and frictional resistance of calcareous sands. 



Test Materials 



Two calcareous sands, from Guam and Florida, and a Ottawa sand, 

 were tested. The calcareous sand from Guam was uniformly graded coraline 

 material with a D n = 0.45 mm and a uniformity coefficient, 



12 



