  The side-wall pressure distribution in static silos is an important and open
problem related to storage safety of granular materials. Referring to Lvin's
theory [Powder Technology 4, 280 (1971)] and Rodolfo's 2D numerical result
[Phys. Rev. E 97.1(2018)], a new theoretical model of side wall pressure is
established by assuming the friction coefficient as well as the ratio of
horizontal to vertical stress changing with depth position in silo.
Furthermore, the transition of stress state between hydrostatic-like and
Janssen-like is systematically investigated by our model and experiment, and
finally an empirical expression describing this transition is proposed.
