The analytical theoretical formula for calculating the unconfined yield shear strength (f(c)) of the powder/oil mixture obtained earlier in our previous paper [1] is modified, taking into account the work required not only to rupture the liquid bridge, but also to move particles relative to each other against the inter-particle friction force. This formula is valid for powder/oil mixtures with homogeneously distributed oil, as well as for dry powders. Experimental results obtained for dry narrowly sized silica particles in a Schulze cell agree with the developed formula, suggesting experimental value for the friction coefficient and accounting for the effect of the roughness on the adhesion and friction forces. (c) 2010 Elsevier B.V. All rights reserved.