A METHOD FOR MEASUREMENT OF HORIZONTAL TO VERTICAL PRESSURE RATIOS OFWHEAT AND BARLEY IN A CIRCULAR BIN

A technique for the in-mass measurement of the horizontal to vertical pressure ratio and the details of the experimental apparatus are prese nted. A device was built for simultaneous measurements of three normal stresses within a granular medium. By recording the tilt of this devi ce it was possible to determine one vertical and two horizontal stress components, which provided two independent values of the pressure rat io. A series of tests was conducted on wheat and barley in a model bin under both virgin and repeated loading. The pressure ratio was monito red throughout the duration of the tests. Density changes and friction forces in the bin were measured by an Instron testing machine and a l oad cell placed below the false bottom. The results showed that the pr essure ratio remains constant with increasing overburden pressure for the initial loading; however, it increases with subsequent loading cyc les. There seems to be a correlation between the pressure ratio and th e stiffness of the granular material. Experimentally determined values of pressure ratio of 0.38 for barley and 0.48 for wheat were reasonab ly close to the value of 0.4 recommended for all grains by the Canadia n Farm Building Code. The deformation of the granular material was mos tly nonrecoverable upon unloading. The walls of the cylindrical test b in with a height to diameter ratio of 3 carried about 60% of the verti cal surcharge loading.