Shear behavior of calcareous sands in three-dimensional stress

Geotechnical problem analyses often involve three-dimensional stress conditions. In this paper, a series of drained true triaxial tests were conducted under stress-controlled conditions to investigate the effect of the intermediate principal stress on the mechanical behavior of calcareous sands. All stress paths, characterized by different intermediate principal stress coefficients (\(b\)-values) and terminal stress ratios (\(\eta\)), were maintained on the same deviatoric plane. The experimental results indicate that the deformation behavior of calcareous sands in three-dimensional stress is highly influenced by the \(b\)-values, particularly in the intermediate and minor principal directions, leading to notable anisotropy. The deviatoric stress–strain curves show that the deviatoric strain effectively represents the three-dimensional strain behavior of calcareous sands. As the \(b\)-value increases from 0 to 1, a simultaneous decrease in the stiffness and volumetric contraction behaviors of calcareous sands has been observed.