A Novel Model for Evaluation of Dynamic Properties of Highly Plastic Clay through Cyclic Large Box Shear Test

Ensuring structural stability against shearing and sliding is crucial in civil engineering, necessitating a comprehensive analysis of shear strength characteristics. This study aims to explore the shear strength of highly plastic clay under varying conditions of strain rate and frequency, coupled with different combinations of normal and shear loads. Both static and dynamic loading experiments were conducted to evaluate the shear strengths. Static tests employed a strain-controlled loading setup with a maximum displacement of 25 mm, applying constant ramp rate alongside varied normal loads and varied ramp rates at constant normal load. Dynamic tests, under stress-controlled conditions, investigated: (i) varying normal stress levels while maintaining constant shear stress and frequency, (ii) different shear stress levels while keeping normal stress and frequency constant, (iii) different frequencies while holding normal and shear stresses constant. The findings indicate a significant correlation between higher shear modulus values and increased ramp rates and normal loads. Conversely, dynamic shear modulus decreases with escalating shear strain and loading cycles. Moreover, within a fixed number of loading cycles, dynamic shear modulus rises with augmented normal and shear loads but declines with higher frequencies, maintaining other parameters constant. These insights contribute to enhancing the understanding of soil behaviour under varying loading conditions, critical for designing resilient structures.