Measurements of pressure and frictional tractions along walls of a large-scale conical shallow hopper and comparison with Eurocode 1991-4:2006

摘要

A silo's hopper supports the majority loads induced by the stored paniculate solids. Such loads vary from filling to discharging provided the hopper is steep enough to secure a mass flow; when the hopper is too shallow to promote a mass flow, funnel flow usually prevails - where how loads develop along walls of a shallow hopper remains to be addressed. In the paper, normal pressure and frictional traction were measured with pressure transducers as imposed by testing material sand along the walls of a full-scale conical shallow hopper. The transducers were carefully mounted in the designated positions of hopper walls along a generator. To make the measurement results representative, a concentric filling was carried out to ensure the sand depositing into the hopper axi-symmetrically; the filling normal pressure and frictional traction as developed along the hopper walls were then measured. The normal pressure and frictional traction during discharging were also measured when the sand was discharged centrically in a free discharge mode. Results from measurements showed that the normal pressure at the commencement of discharge changed only slightly from that as developed at the end of filling. Both the filling and discharging normal pressure, as demonstrated in the paper, could be evaluated based on the mechanics of steep hopper filling pressures by adopting an effective friction coefficient as proposed in Eurocode 1-4:2006 for a shallow hopper. Measurement also showed that the frictional traction was not fully developed either in filling or during discharging; a friction coefficient was only partially mobilised as an effective friction coefficient, and might vary very significantly from one location to another along the wall.