CUBICAL TRIAXIAL TESTS ON COHESIONLESS SOIL

In this closure to the discussion, the authors observe that the shape of the phi-b relationship obtained for Ham River sand in the ISC apparatus corresponds well to that obtained from Monterey No. 0 sand in cubical triaxial apparatus. If the friction angles obtained for Moterey No. 0 sand were corrected to correspond to the same octahedral normal stress, the increase in friction angle from triaxial compression (b=0) to triaxial extension (b=1) would be slightly pronounced, but the general shapes of phi-b relationships would change very little. Comments are made on the question of possible frictional restraint between the specimen and the horizontal loading plates. They conclude that the effect of frictional restraint at the end plates was small as long as the specimens deformed uniformly. The procedure used for specimen preparation is detailed. To obtain stress-strain data after failure, the major deviator stress was strain controlled in accordance with the suggestions of Lundgren, Mitchell, and Wilson. The nature of triaxial compression tests (b=0) are discussed, as well as the method of application of deviator stresses and the result of the plane strain tests. The observation is made that any failure criterion for cohesionless soil which can be expressed in terms of stress variants can be plotted in the sin phi-b diagram.