LAUSR

Frictional behaviour of wheat on corrugated steel walls, pressure distribution, and grain flow were investigated using a silo model with a square cross section. Corrugated steel sheets were attached to both side walls of the model silo, while clear polymethyl methacrylate was used for the front and rear walls to allow observation of the flow. In addition, a truncated steel pyramid was used for the hopper and a square outlet with sides varying from 0.02 m to 0.06 m. A test panel was placed at one of the side walls in the place of a cut off fragment of the wall to measure lateral and frictional wall forces. The tests were conducted using winter wheat, and two filling methods (central and distributed) were considered to analyse their possible influence on bulk density or shear behaviour during silo discharge. It was found for the distributed filling that the grain-wall friction coefficient during discharge was nearly 20% larger than that for the central filling. This coefficient was found to increase slightly with the increasing size of the outlet, a trend that was not observed for the central filling. The experimentally determined pressures and coefficient of wheat-wall friction were compared with the recommendations of Eurocode standard EN 1991-4. Differences between the experimental and theoretical results demonstrate that the formulae proposed by the Eurocode do not take into account some important issues associated with friction between the grain and the corrugated silo wall.