The Study On Compression Characteristics Of Wheat Piles And Maize Piles, The Stress On The Wall And The Total Weight Of The Grain Storage In Silos

In this paper, the elastic modulus, bulk strain modulus, density, verticalcompressive stress, lateral pressure on silo wall and the total storage weight of wheatpiles and maize piles in the silos were studied.1The elastic modulus of wheat and maize piles are measured by thestrain-controlled triaxial apparatus. The results show that when the range of confiningpressure is50~200kPa, the range of the elastic modulus of the wheat piles fromHenan province (the range of moisture content is10.77%~17.23%w.b), the wheatpiles produced in Canadian (the range of moisture content is11.88%~16.85%w.b)and the maize piles produced in Hebei (the range of moisture content is12.43%~17.50%w.b) are12.640~87.289MPa,13.294~87.379MPa and18.50~65.61MParespectively. Under the same confining pressure, as the moisture content increases,the elastic modulus decreases. Under the same moisture content, the elastic modulusincreases with the confining pressure.2The bulk strain modulus of wheat and maize piles are measured by thestrain-controlled triaxial apparatus. The results show that when the range of confiningpressure is2~200kPa, the range of the bulk strain modulus of the wheat piles fromHenan province (the range of moisture content is11.70%~18.18%w.b), the wheat pilesproduced in Canadian (the range of moisture content is11.88%~16.85%w.b) and themaize piles produced in Hebei (the range of moisture content is10.92%~17.13%w.b)are140.48~656.47kPa,152.274~671.769kPa and157.47~617.62kPa respectively.In the same moisture conditions, the bulk strain modulus increases with the confiningpressure increases. Under the same confining pressure, the higher of the moisturecontent and the smaller of bulk strain modulus. The equations about the relationshipof confining pressure and the elastic modulus are fitted. The equations of the wheatpile produced in Henan, Canadian and Hebei are y=-0.6082x4+34.515x~3-731.24x2+6849.9x-23271, y=-3.0611x~3+128.67x~2-1809.3x+9138.6and y=0.7473x~3-33.636x~2+485.39x-1655.9respectively, where y is the bulk strain modulus and x isthe moisture content of the samples.3The elastic modulus in conditions of limited lateral expansion of wheat pilesand maize piles are measured by the LHT-1-type resilient modulus measuringinstrument. The results show that when pre-pressure is in the range of0~200kPa, theranges of the elastic modulus of the wheat piles from Henan (13.10%~16.59%w.b)and the maize piles produced in Northeast (13.89%~18.74%w.b) are10.47~602.38MPa and11.69~565.38MPa respectively. The elastic modulus of maize pile increase with the increase of the pre-pressure in a certain moisture content. In thesame pre-pressure conditions, as the moisture content increases, the elastic modulu ofmaize piles produced in Northeast decreases.4The bulk strain modulus in conditions of limited lateral expansion of wheatpiles and maize piles are measured by the LHT-1-type resilient modulus measuringinstrument. The results show that when the average confining pressures are in therange of18.281~133.248kPa and18.074~110.442kPa, the ranges of the bulkstrain modulus of the wheat piles from Henan (11.70%~18.18%w.b) and the maizepiles produced in Northeast(12.56%~17.09%w.b) were299.149~2151.634kPa and432.060~2437.688kPa respectively. At the same top-stress, the bulk strain modulusdecease with the moisture content increase. In the same moisture content, a increase inaverage confining stresses yielded a increase in the bulk strain modulus of corn pile.5The relationship between the wheat and maize piles’ compressed density andcompressive stress is measured by LHT-1-type measuring instrument. The resultsshow that when the average vertical compressive stress is in the range of0.55~221.00kPa,0.531~209.557kPa, the compressed densities of the wheat piles fromHenan (11.70%~18.18%w.b) and maize piles produced in Northeast (12.56%~17.09%w.b) are815.49~949.88kg/m3and722.108~807.301kg/m3. Accordingto the relationship between density and the compression stress, the equation can befitted.6The differential equation of density, vertical compressive stress and depth ofwheat piles in silos have been derived on the basis of equilibrium theory.7Combined with the equation of relationship between bulk density of wheat pileand the average vertical compressive stress, we can do numerical calculation of thedifferential equation of density, vertical compressive stress and depth of wheat piles.Choose the following parameters: height of the silo is30m, radius of silo is9m,coefficient friction of wall is0.4, the angle of hopper wall and horizontal axis is45°, themoisture content of wheat is12.5%w.b, the angle of internal friction is25°, the bulkdensity of wheat is800g/L, the wheat pile surface is conical free scattered, the stepcalculated is0.1m, the numerical calculation results show that the range of density ofwheat pile in the part of cylinder silo is809.32~844.04kg/m3, the range of densityof wheat in the hopper is844.04~832.10kg/m3. The rate of change of density is5.51%. In the cylinder part of silo, the range of vertical compressive stress of wheatpile is11.72~154.22kPa and the range of the lateral stress on silo wall is4.76~62.59kPa. In the hopper, the range of vertical compressive stress of wheat pile is131.63~26.13kPa and the range of the lateral stress on silo wall is154.60~30.69 kPa. Four silos numbered as040,43-3,43-5and45-2are selected to verify the theoryof this paper. The results show that the errors of the result calculated by this paper’stheory and the actual number are respectively1.18%,0.92%,1.07%,1.46%. Theerrors of the result calculated by standard bulk density device method and the actualnumber are2.73%,3.86%,3.69%,2.32%respectively. Therefore, the total storageweight of calculated by the theory of this paper is closer to the actual number than theresult calculated by standard bulk density device method.