ABSTRACT
The cohesive soils experience cyclic instability under dynamic loading conditions due to pore water pressure-induced softening and progressive strength degradation. The present study explores the cyclic response of soft cohesive soil through strain-controlled cyclic triaxial (CTX) tests conducted at varying cyclic strain amplitudes under 100 kPa confining pressure and a constant loading frequency of 0.5 Hz for 200 cycles. The dynamic properties of the soil, shear modulus (G) and damping ratio (D), were evaluated alongside the evolution of excess pore water pressure under different cyclic loading conditions. Stiffness degradation was quantified using the cyclic degradation index (δ) and degradation parameter (t). The results indicated that higher strain amplitudes led to greater stiffness deterioration and increased residual pore water pressure, attributed to increased plastic deformations at such high strain levels. This highlights a significant reduction in the strength and stiffness of soft cohesive soil under cyclic loading conditions.
