2次元モデルによる粒状体のせん断現象の微視的考察

Abstract

This is a report on a microscopic consideration of the shearing mechanism in granularmaterials such as sand and gravel. In order to investigate the mechanism throughobserving the interaction between particles microscopically, the direct shear test wascarried out by using a horizontal pile of alminium rods with various diameters as asimulation of two-dimensional granular mass. Another direct shear test was performedby using a similar horizontal pile of rods made of photcelastic material to measure theinterparticle force transmitted during shearing process.Besides these tests, a simulation of two-dimensional particle arrangement (structure)in an initial state before shearing was obtained analytically by applying Monte Carlomethods.In these investigations the interparticle force f, the frictional angle between particles6 and the slope angle of the particle surface at the individual contact point against thegeneral shearing plane θ were chosen as fundamental factors to control the shearingresistance of the materials. Among these the frequency distribution of θ (-90°<θ<90°):Nj(θj) (θj-Δθ/2<θj<θj+Δθ/2) was adopted as a factor to evaluate the particle arrange-ment on the shearing plane, and it was found that this factor dominated the stress-strain-dilatancy character of the materials. It was also found that Nj(θj) was related to the sumof the interparticle force in the same small range JO of 6: Fj(θj) as expressed by Eq. (4), which was obtained empirically from Fig. 7. From this relation tanΦm0(=τ/σN) can hecalculated by Eq. (5) if Nj(θj) is known. This calculated Φm0 agrees well with themeasured Φm0 as shown in Table 1. Furthermore some macroscopic mechanical propertiesobtained by repetiticoal loading test were explained from the similar microscopic pointof viev.