c)
Figure 7. Plot of the key experimental output from the SRST. (a) FFc and σu, (b) σt and packing density, and (c) φ and τpre.

4.1.4 Relative contribution of tensile strength and friction on unconfined yield strength

Next, the relative contribution of the tensile and frictional components on the unconfined yield strength are explored. The stress contribution due to the frictional component \(\sigma_{f}\) is calculated by subtracting tensile strength from the unconfined yield strength:
\(\sigma_{f}=\sigma_{u}-\sigma_{t}\) (5)
It is important to note that this frictional component is different from the internal angle of friction and the shear stress. It is a fictitious contribution of friction to unconfined yield strength in the normal direction.
Figure 8 shows the relationship between the frictional and tensile contributions to the total unconfined yield strength. Both the friction and tensile strength contribute to the unconfined yield strength, and the contribution of friction is slightly higher than that of tensile strength. It is also noted that the frictional strength follows the trend of internal angle of friction and τpre as shown in Figure 7c.