Numerical Investigation on the Reference Crushing Stress of Granular Materials in Triaxial Compression Test

Particle crushing dominates the deformation behaviour of granular materials under significantly high compressive and shear stress. A proposed constitutive model has been verified to predict crushing behaviour of granular materials with different crushability and adopted one kind of reference crushing stress. It is noted that no positive dilatancy of granular material in triaxial test occurs once the confining pressure exceeds a certain stress level. That stress is defined as the reference crushing stress. This study presents a parametric study on the reference crushing stress in the constitutive model and examines its variation for dierent distributed ranges of grain size gradation and relative densities. Predicted results demonstrate that the peak stress ratio increases and contractive behaviour becomes less obvious with a larger reference crushing stress. Reference crushing stress increases with a wider grain size gradation and larger relative density for the same granular material. A linear relationship between the reference crushing stress and single particle strength has been obtained from the numerical and experimental results. The reference crushing stress can be recognized as one eective index to evaluate the strength of granular material in triaxial tests

Experimental Investigation on Crushing of Granular Material in One-Dimensional Test

A series of one-dimensional compression tests have been carried out on three kinds of granular materials in a dense state to investigate their mechanical and crushing behaviours. A new testing apparatus that can simultaneously measure the axial and lateral stresses acted on the cylindrical specimen was also developed.Experimental results show that the break-point stress on e – log p curve is the largest for glass beads ballotini. A rise in compression index with the increasing axial load is observed for all three granular materials. The lateral earth pressure coefficient at rest Ko for the three granular materials slightly increases with the increasing axial load and attains a steady value between 0.25 and 0.3 at the initial loading stage. The value for Ko markedly increases as the axial load is removed during the unloading process. The axial strain of Masado is the largest at the same axial load level due to its mineral hardness. Experimental results demonstrate that the crushing degree of granular material is greatly influenced by the loading modes and conditions

Observation of sand particles in shear zone using digital image analysis

In this paper, a digital image analysis method is described to observe the deformations of granular particles insands. First, the movements of granular particles in sands were observed as the image data during the direct sheartest of Toyoura sand. And the strains in global scales were calculated continuously by the analysis of the relativemovements of adjacent individual particles.As the result, the shear zone can be determined clearly by the above strain distributions. Furthermore, the con-ducted dilatancy angle in this study was nearly closed to the value in the previous paper

構造物の不同沈下に関する解析的研究

広島大学(Hiroshima University)博士(工学)Engineeringdoctora

Analysis of the ultimate Earth Pressure on Underground Conduits

The ground movement caused by the consolidation of soil or surface loading changes the state of stress in the ground adjacent conduits. Under these circumstances the conduits may be subjected to very high ground forces which can lead to conduit failure. The purpose of this paper is to present a method of estimating the ultimate earth pressure on the conduits, which is based on the limit analysis and equilibrium equations. The analysis presented is similar in principle to that employed by Matsuo (1964), but it is also extended to conduit groups which are placed in parallel. The failure model of soil mass used in the present analysis is produced by analysing photographs to show movements of sand particles around the conduits during model tests. Furthermore, on the assumption that the Mohr-Coulomb's failure criterion is valid on shear sliding line, the failure model is shaped by a logarithmic spiral. In this paper, comparisons are also made between observations on the ultimate earth pressure acting on the model conduits set in the dry sand and a mass of aluminum rods and those predicted by the proposed theory, and it is found that the proposed theory can predict the test results fairly well