ABSTRACT
Some experimental works on rapid flow of granular materials have been performed with motivation to examine some results of kinetic theory of granular flow (e.g., Bagnold, 1954; Savage & Sayed, 1984). To do this, however, we must carefully take into account effect of interstitial viscous fluid and gravity since most of the theoretical works were discussed based on assumption that dry, uniform sized spheres flow under the gravity-free condition. Earth’s gravity, for example, produces a static pressure at bottom of a 1 cm soil column equal to dynamic normal stress produced by a shear strain rate at 5-10 (1/sec). In order to minimize effect of gravity, one can use interstitial fluid of same density as granular particles (Bagnold, 1954). In this case, however, influence of viscosity must be taken into consideration. Possible ranges of solid fraction and shear strain rate are commonly so limited in the previous experiments that it is not easy to figure out micro-mechanical behavior of entire range of granular flow. Moreover, it is difficult to observe directly micro-mechanical quantities such as individual particle velocity and local solid fraction in a flow domain. In order to clarify characteristic of granular flow from a micro-mechanical point of view, an apparatus was newly designed to generate two-dimensional flow (Iwashita et al. 2004). However, that apparatus didn’t have measurement ability of normal stress generated by granular flow. In order to measure normal
stress and shear stress at the same time, the apparatus was modified. Based on test results, we will discuss relation between stress ratio generated by flow and the solid fraction or shear strain rate.
