<p>In geotechnical engineering practice, soft clay foundations frequently experience an initial inclination of the principal stress axis before being subjected to either proportional or non-proportional loading. Such initial stress conditions can significantly influence the subsequent shear response and failure mechanisms, inducing both anisotropy and non-coaxiality. In this study, a series of undrained monotonic and cyclic hollow cylinder torsional shear tests were conducted on reconstituted soft clay specimens that underwent anisotropic consolidation with varying initial principal stress orientations. The results show that the undrained shear strength obtained from the monotonic loading tests is influenced by the inclination angle of the major principal stress relative to the vertical axis, denoted as <i>α</i>₀. Comparable strength anisotropy was observed in cyclic tests, with the most pronounced strain accumulation occurring at <i>α</i>₀ = 45°, under cyclic loading both with and without continuous principal stress rotation (PSR). Moreover, cyclic PSR markedly accelerates the accumulation of permanent deformation and induces more pronounced non-coaxial responses than orientational monotonic or cyclic shearing. Analysis of the non-coaxiality angle reveals prominent non-coaxial responses during orientational shearing at <i>α</i>₀ = 22.5° and 67.5°, while rotational cycling produces evident non-coaxial responses across all <i>α</i>₀ cases. Notably, the rotational non-coaxiality diminishes when the stress direction rotates and aligns near <i>α</i>₀ ± 10°. These findings provide comprehensive experimental evidence for the anisotropic and non-coaxial behavior of soft clay, offering valuable insights for geotechnical analysis and design in practice.</p>