平底筒仓Janssen公式中储料特征高度的测定及其变化规律

Determination of characteristic height with Janssen formula of storage material and its variation law in silo with flat bottom

筒仓储料的特征高度是Janssen公式中影响筒仓储料压力计算准确性的重要参数,为了进一步缩小筒仓储料压力的理论值与真实值之间的偏差,该研究对筒仓储料的特征高度进行试验研究。该研究利用筒仓储料压力综合试验装置,对小麦储料堆的底部竖向压力和仓壁总摩擦力进行测量,并根据储料堆的底部竖向压力和仓壁总摩擦力与特征高度之间的关系计算得到特征高度的值。研究了整个储料堆的特征高度与储料填充高度的关系,探讨了储料堆内部的特征高度与填充高度的关系以及储料堆内部的特征高度的分布规律。得到如下结论:1)筒仓储料堆的特征高度的试验值大于Janssen理论值。2)储料堆的底部竖向压力的测试值大于Janssen理论值,筒仓仓壁总摩擦力的测试值小于Janssen理论值。3)对于筒仓整个储料堆的特征高度λ,当高径比H/D<0.9时,随着储料填充高度的增加而逐渐减小;当高径比H/D≥0.9时,特征高度λ值几乎保持不变。4)对于储料堆中不同半径实心圆柱的特征高度,当高径比H/D<0.9时,均随着储料填充高度的增加而逐渐减小;当高径比H/D≥0.9时,随着储料填充高度的增加,半径最大的圆柱(即整个储料堆)的特征高度几乎保持不变,其余圆柱的特征高度以不同速率呈非线性逐渐减小并趋于相等。5)储料堆中不同半径实心圆柱的特征高度基本随着圆柱半径的增大而减小。该研究为Janssen公式中储料特征高度的确定提供一种试验方法,使Janssen公式能够用于筒仓储料压力的精确计算。

Because Janssen formula is derived under certain assumptions,there is a certain deviation between the theoretical value and the real value of the storage material pressure in silo.The characteristic height of storage material in silo is an important parameter in Janssen formula,which affects the accuracy of calculation.Therefore,the experimental study on the characteristic height of storage material in silo was carried out in this study.The vertical pressure at the bottom of the storage material pile and the total friction force on the silo wall were measured by using the comprehensive test device for measuring the storage material pressure in silo,when wheat was used as storage material.And the value of the characteristic height was calculated according to the relationship between the vertical pressure at the bottom of the storage material pile and the characteristic height and the relationship between the total friction force on the wall and the characteristic height.The relationship between the characteristic height of the whole storage material pile and the filling height was studied.The relationship between the characteristic height in the storage material pile and the filling height,and the distribution law of the characteristic height in the storage material pile were discussed.The conclusions are as follows:1)The test value of characteristic height of storage material pile in silo is greater than theoretical value of Janssen formula.2)The measured value of vertical pressure at the bottom of the storage pile is greater than theoretical value of Janssen formula,and the measured value of total friction force on the silo wall is less than theoretical value of Janssen formula.When the ratio of height to diameter H/D less than 1.5,the measured value of vertical pressure at the bottom of the storage pile and the total friction force on the silo wall are close to theoretical value of Janssen formula,and the relative difference(the absolute difference between the measured value and the theoretical value divided by the measured value)is within 6%.When the ratio of height to diameter was H/D greater than or equal to 1.5,the relative difference between the tested value and theoretical value of Janssen formula is more than 6%.3)For the characteristic heightλof the entire storage pile in silo(that is,the solid cylinder with the largest radius),when the ratio of height to diameter H/D less than 0.9,it gradually decreases as the filling height of the storage increases;When H/D greater than or equal to 0.9,the characteristic heightλremains nearly constant,and this stage is the stable stage of the characteristic height.4)For the characteristic height of solid cylinder with different radiuses in storage material pile,when the filling height less than 0.44 m,they all decrease with the increase of filling height of storage material;when the filling height greater than or equal to 0.44 m,with the increase of filling height of storage material,the value of the cylinder with the largest diameter(the whole storage material pile)remains almost unchanged,and the values of the remaining cylinders decrease nonlinearly at different rates and tend to be equal.5)The characteristic height of the solid cylinder with different radiuses in the storage material pile basically decrease with the increase of the cylinder radius.This study provides a method for the determination of the characteristic height of storage material in Janssen's formulas,which enables Janssen's formulas to be used for the accurate calculation of the pressure of storage material in silo.