Strength and deformation behaviour of coarse-grained soil by true triaxial tests

Abstract

In order to investigate the influence of intermediate principal stress on the stress-strain and strength behaviour of a coarse-grained soil, a series of true triaxial tests were performed. The tests were conducted in a recently developed true triaxial apparatus with constant minor principal stress σ₃ and constant value of intermediate principal stress ratio b=(σ₂−σ₃)/(σ₁−σ₃) (σ₁ is the vertical stress, and σ₂ is the horizontal stress). It is found that the intermediate principal strain, ɛ₂, increases from negative to positive value with the increase of parameter b from zero to unity under a constant minor principal stress. The minor principal strain, ɛ₃, is always negative. This implies that the specimen exhibits an evident anisotropy. The relationship between b and friction angle obtained from the tests is different from that predicted by LADE-DUNCAN and MATSUOKA-NAKAI criteria. Based on the test results, an empirical equation of g(b) that is the shape function of the failure surface on π-plane was presented. The proposed equation is verified to be reasonable by comparing the predicted results using the equation with true triaxial test results of soils, such as coarse-grained soils in this study, sands and gravels in other studies.

Keywords

cohesionless soil / coarse-grained soil / true triaxial test / strength / deformation / failure criterion