应力未饱和粮仓系统中器壁与颗粒的摩擦阻力

对于仓壁不固定的粮仓系统，其底部压力会随颗粒高度线性增加.由于没有Janssen应力饱和现象，其力学状态与通常粮仓系统显然不同.通过上拉和下压这种应力未饱和粮仓系统的仓壁，实验研究了不同顶部负载时颗粒介质与仓壁的最大静摩擦阻力.结果显示阻力随颗粒质量的增加在上拉时呈线性增长关系，但在下压时呈指数增长关系，下压阻力强度比上拉时大一个量级以上.此外阻力与顶部负载呈线性变化关系.这些测量很好地符合了基于应力转向比为常数的假设（即Janssen假设）下给出的连续力学理论计算，表明该假设对于此应力未饱和粮仓系统依然适用. 关键词： 颗粒物质 粮仓 静摩擦 应力转向比

Friction force between wall and granular matter for a silo with unsaturated stress

For a silo with unfixed wall, the pressure on its bottom will increase linearly with the height of granular material filled in it. Because no Janssen stress saturation occurs, its mechanic states differ from that of usual silo. By vertically pulling and pushing the wall of the silo, we measured the maximum static friction force of the wall, as functions of the load applied on the silo top and the mass filled in the silo. It is observed that the force increases with the mass, linearly for the pulling case, while exponentially for the pushing case, of which value for the latter may be one order of magnitude larger than that for the former. The force also increases with the load, linearly for both cases. The measurements can be well fitted with the theoretical results of continuous mechanics, assuming that ratio between horizontal and vertical stresses keeps the same everywhere inside the silo. The results support that the assumption made by Janssen for usual silo also suitable for the silo which has no stress saturation.