Energy dissipation response of unsaturated cohesive soil under dynamic loading conditions

Partially saturated soils are commonly encountered in various geotechnical engineering projects across the world. Existence of matric suction in the three-phase system of unsaturated soil governs its strength and volumetric response. Environmental changes cause alterations in the geometric arrangement of unsaturated soil due to seasonal variation in the matric suction of soil leading to change in mechanical response of unsaturated soils. Cyclic high/low amplitude loading on soils such as seismic loading, machine vibrations, wave loading, traffic loading, blast loading, etc., can instigate the loss in strength and stability of soils. Energy dissipation during cyclic loading can provide information regarding internal deformation characteristics of soils. Current study evaluates the influence of initial static loading, matric suction, dry density and water content on the energy dissipation characteristics of unsaturated cohesive soil. Series of strain-controlled cyclic triaxial tests were conducted on cohesive soil from Ahmedabad (India) under unsaturated conditions (as-compacted) at varying initial static axial strain (S), dry density and water content. In-contact filter paper method was used to evaluate matric suction of Ahmedabad soil. Application of different axial strain (S) significantly affected the cumulative energy dissipation (ΔW<inf>T</inf>) of unsaturated cohesive soil. Matric suction of soil exhibited significant impact on the energy dissipation characteristics of Ahmedabad cohesive soil. Dry density of unsaturated Ahmedabad cohesive soil was observed to play an important role in the energy dissipation characteristics. Substantial energy dissipation along with larger stiffness degradation indicated soil under unsaturated conditions to be metastable and prone to severe damages during dynamic loading conditions.