Strength and Deformation, Characteristics of Sand in Torsional Simple Shear

Abstract

This paper describes the strength and deformation properties of a clean sand (Toyoura sand) in torsional simple shear under the drained condition. It was found that the dependency on pressure level of both the angle of internal friction ϕ = arcsin {( σ 1 '- σ 3 ')/( σ 1 '+ σ 3 ')} max and the relationship between the stress ratio σ 1 '/ σ 3 ', the shear strain γ max = ɛ 1 - ɛ 3 and the volumetric strain ɛ v = ɛ 1 + ɛ 3 at relatively large strains is very small when σ 3 ' is less than about 0. 5 kgf/cm 2 (49kN/m 2 ). These results are well in accordance with those previously obtained for the sand by the triaxial compression tests, the plane strain compression tests and the torsional shear tests on isotropically consolidated specimens. The results of the present tests show that the relationships between σ 1 '/ σ 3 ', γ max and ɛ v and the stress states in terms of b = ( σ 1 '- σ 3 ') / ( σ 1 '- σ 3 ') at relatively large strains in simple shear are very similar to those by the plane strain compression test in which the directions of principal stresses with respect to the fabric of the specimen are fixed to the values in the simple shear tests at relatively large strains. The angle of friction ϕ * in simple shear defined in the conventional way as arctan ( τ at /σ a ') max ( τ at /σ a 'is the stress ratio on the horizontal plane of shearing) was found less than ϕ by about 14%. It was found that ϕ in simple shear is well comparable with that in plane strain compression only when the directions of principal stresses with respect to the fabric of specimen are the same in the both testing methods.