Strength and Deformation Characteristics of Sand in Plane Strain Compression at Extremely Low Pressures

Abstract

A series of drained plane strain compression tests was performed on saturated samples of fine angular to sub-angular sand at confining pressures from 0.05 kgf/cm 2 (4.9 kN/m 2 ) up to 4.0 kgf/cm 2 (392kN/m 2 ). Samples were prepared by the air-pluviation method with changing the angle δ of bedding plane to the σ 1 '-direction during plane strain compression tests from 0 to 90 degrees. It was found that in the plane strain compression tests the dependency of ϕ = arcsin {( σ 1 '- σ 3 ')/( σ 1 '+ σ 3 ')} max on σ 3 ' is very small when σ 3 ' is lower than around 0.5 kgf/cm 2 as well as in the triaxial compression tests. Strong strength anisotropy was observed; ϕ has its minimum at δ between 23° and 34°. It was also found that this minimum value of ϕ in plane strain compression is similar to ϕ at this value of δ in triaxial compression. The tendency of such strength anisotropy was found rather insensitive to stress levels employed ( σ 3 '=0.05 ~ 4.0 kgf/cm 2 ). The stress-dilatancy relation at the peak stress condition was found to be a strong function of 5 whereas this relation was insensitive to the change of σ 3 ' . The change of the deformation characteristics of sample with the change of σ 3 ' was found to be rather small when σ 3 ' is lower than around 0.5 kgf/cm 2 as well. It was found that the strength anisotropy and deformation anisotropy as a function of δ are somewhat different.