Hello dear Abdellah

Particle size distribution, morphology, shape size, all have contributions to internal friction angle of granular soils due to grain-to-grain force chains, and large surface exposure of the grains would provide enough contact layout that it will increase internal friction angle but at the same time as in case of granular soils, it drives in lower friction angles due to physical (breakage) or chemical (dissolution), in sub-granular materials such as sands anisotropy is also an inherent property with influence but in fine granular soils to fine soils the role of specific surface area leads to reduction of internal friction angle as the number of contact points changes its importance to chemical bonds which contributes to cohesion instead of friction, as usual, strength determination is the main characterization technique of internal friction angle analysis, and chemical tests like BET surface area analysis is used for evaluation of specific surface area, yet, you can determine number of contact points (not meaning to count them) by crystallography and image processing to atomic resolution by SEM.

Feel free to ask further questions

Thanks a lot for these kindly responses. Dear Babak Jamhiri. With my personal regards.

Dear Abdellah

I think that there is no significant relationships between friction angle and specific surface of granular materials.

First the specific surface is so small in granular materials due to large masses of particles compared to their surface areas.The most important factor is the contact between particles which contributes to interlocking between them and hence affects the angle of friction.

Thanks a lot for your kindly responses. Dear Mohammed Yousif Fattah . With my personal regards.