颗粒固体应力转向比的光弹法探测

利用压敏双折射光学特性材料,实验测量了在自然堆积和密堆积两种制样方式下颗粒仓轴向荷载在仓壁上随深度的分布.发现在填充颗粒总质量相同、容器不变的情况下,颗粒仓轴向荷载在仓壁上的分布不随颗粒深度单调变化,而是随深度呈单峰结构,数值模拟与实验观察定性符合,并且发现峰值依赖于荷载大小和样品的制备方式.另外,我们也测量了在不同填充高度下的颗粒底部平均应力随轴向荷载的变化,将其与边壁应力对比,得到颗粒体系不同深度处的转向比.

Janssen ratio in granular solid measured by photoelastic method

In this work Janssen ratio is measured in a dense granular pack. The pressure on the side walls as a function of the depth of the pack with top load under gravity is measured by photoelastic method. The samples are prepared by “point source” method with and without tapping. A non-monotonic distribution of the side pressure along the depth is found. Numerical simulation is performed and shows qualitative consistency with the experimental finding. The apparent weight of the sample is measured for different filling heights and for different top loads. Comparing with the normal stresses on the silo wall for different heights, we obtain the Janssen ratio J =σ_xx/σ_zz as a function of height. We find that although uJ = 0.11 is a constant as is expected, the Janssen Ratio is height dependent. It becomes height independent only when the top load is large enough.