粮仓内颗粒压力的测量:Janssen行为及其偏差

Measurements of granular pressure in silo: Janssen behaviour and deviation

基于侧壁分为上下两部分的装置,测量了圆柱对称颗粒系统(竖直粮仓)的压力随高度的变化,并讨论了测得的仓内压力与Janssen理论模型的偏离情况.实验结果显示无论是否对粮仓进行Vanel等建议的让"侧壁摩擦力充分动员"的底座缓慢下沉操作处理,测得的仓内压力都有不同程度的偏离Janssen现象.另外如果没有沉降处理,在填充颗粒的荷载下上侧壁会发生微弱下沉,从而显著增大压力偏离的程度,但沉降处理可将其消除.这些结果表明,粮仓的颗粒重量在仓底和沿侧壁边界上的分配情况受制备方式和装置变形的影响明显,具体分布情况复杂多样.因此颗粒物质的静应力弹性理论分析应该取应力边界条件.

Variations of pressure along the vertical direction in a cylindrical silo are measured, of which the side wall is comprised of two separated up and down parts. The deviation of the measured results from the so-called Janssen model of silo stress is discussed. The measurements show that certain deviations from the model are always observed, no matter whether the slowly downward motion of silo bottom by ＂fully mobilized friction＂ as suggested by Vanel et al is carried on. Moreover without mobilizing the friction, the deviation may increase considerably if a tiny sink of the upper side-wall caused by weight of filled grains is present. The effect can be however eliminated by the friction mobilized. These indicate that distributions of grain weight at the bottom and lateral wall are complex and variant, and dependent on preparation manner and deformation of experiment setup. So stress boundary conditions need to be taken into account in the nonlinear elastic theory for analyzing static stress distribution of granular matter.