Monotonic undrained and drained compression response of CL-ML soil

The present study investigates the mechanical behaviour of silty clay (CL-ML), a relatively underexplored soil type, with a focused emphasis on the role of drainage boundary conditions on its shear strength characteristics. CL-ML soil presents a promising alternative for embankment construction, but its performance under realistic service conditions remains inadequately understood. The experimental program in this study was henceforth so designed to primarily understand the monotonic compression response of CL-ML soil under controlled drained and undrained boundary conditions. Additionally, the influence of initial compaction states of the soil on key geotechnical properties, including hydraulic conductivity, compressibility, unconfined compressive strength, and total shear strength, was assessed. Stress-strain characteristics, volumetric strain, and pore pressure responses were evaluated across a range of initial compaction states under both drainage conditions. The shear behaviour of the soil under different drainage modes was also assessed using the strain energy dissipation framework in this study. Results revealed the well-compacted soil specimens to exhibit higher undrained shear strength compared to drained strength, with the opposite trend observed in poorly compacted specimens. The phase transformation behaviour in the soil under undrained loading was also noted to be predominantly governed by the initial compaction state.