Experiment Study On Friction And Compression Characteristics Of Grain In The Large Horziontal Warehouse

In this paper, the friction characteristics and compression characteristics ofpaddy, soybean and wheat in the large horziontal warehouse were researched.First, the angles of internal friction of paddy, soybean and wheat were measuredby direct shear apparatus. The result of direct shear test showed that the range of theangles of internal friction of paddy (13.55%,15.14%,17.00%and19.19%w.b),soybean(9.8%,12.3%,14.5%and16.8%w.b) and wheat(13.55%,15.28%,16.60%and17.90%w.b) are from29.39°to47.19°,36.99°to58.19°and21.21°to46.81°respectively when normal stress is from25kPa to200kPa. As the normal stressincreases the angles of internal friction of paddy, soybean and wheat decreases at thesame moisture content. The angle of internal friction of paddy has no significantrelevance of the moisture content at a certain normal stress. But as the moisturecontent increases the angles of internal friction of soybean and wheat decreases at thesame normal stress.Second, the coefficients of friction of paddy, soybean and wheat against differentsurface of material (stainless steel, concrete and board) were measured by direct shearapparatus. The result of direct shear test showed that the range of coefficients offriction of paddy against stainless steel, concrete and board are from0.207to0.233,0.5to0.563and0.498to0.587respectively, the range of coefficients of friction ofsoybean against stainless steel, concrete and board are from0.307to0.44,0.5to0.574and0.473to0.64respectively, and the range of coefficients of friction of wheatagainst stainless steel, concrete and board are from0.23to0.613,0.469to0.952and0.45to0.852respectively when normal stress is from25kPa to200kPa. As the normalstress increases the coefficients of friction of paddy, soybean and wheat decreases atthe same moisture content. As the moisture content increases the coefficients offriction of paddy, soybean and wheat decreases at the same normal stress.Third, the elastic modulus of paddy(13.55%,15.14%,17.00%and19.19%w.b)and soybean(9.8%,12.3%,14.5%and16.8%w.b) were measured by triaxial apparatus.The result of triaxial test showed that that the elastic modulus of paddy and soybeanrange from8.69Mpa to38.81Mpa and23.66Mpa to29.05Mpa respectively whenconfining pressure is from25kPa to200kPa. As confining pressure increase, theelastic modulus of paddy and soybean increase at the same moisture content. Theelastic modulus of paddy has no significant relevance of the moisture content in acertain confining pressure. But as the moisture content increase, the elastic modulusof paddy and soybean dscrease at the same confining pressure. Then, the bulk strainmodulus of of paddy and soybean were measured by triaxial apparatus.The volume ofpaddy and soybean dscreased with the increase of the confining pressured(5kPa~200kPa、8kPa~152kPa). The bulk strain modulus of paddy are557.91,543.46, 535.57and504.70kPa respectively when confining pressure is200kPa and as theconfining pressure increase, the bulk strain modulus decrease. The bulk strainmodulus of soybean is498.18,451.29,439.19and417.30kPa respectively whenconfining pressure is152kPa and as the confining pressure increase, the bulk strainmodulus decrease.Fourth, the relationship of density of wheat and the average vertical compressionstress in the large horziontal warehouse and the fitted equation were measured bymodulus of resilience meter. Then, we can get the differential equation about thedepth of wheat, the density of wheat and the average vertical compression stress onaccount of equilibrium principle.Fifth, we calculated the equation about the density of wheat and the averagevertical compression stress and the differential equation about depth of wheat, thedensity of wheat and the average vertical compression stress. The result showed thatas the depth of grain increase, the density of wheat increase, and the fitted equationsis y=-0.1305x2+3.5727x+799.68, x is the depth of grain and y is the density ofwheat(the length is44m, the width is21m, the depth of wheat is9m, the moisturecontent is12.5%, the angle of internal friction of wheat is25°, the coefficient offriction of wheat is0.4, the bulk density is800g/L). The compression stress increasedwith the increase of the depth of grain. The total weight of stored grain increased withthe increase of angle of internal friction, bulk density and moisture content anddecreased with the increase the coefficient of friction. We campared the cauculationresults from this paper and the actual values offered by Nanjing Tiexinqiao graindepots. The error is about2%.