An Enhanced Bounding Surface Model for Modelling Various Cyclic Behaviour of Clay

Area of Science:

• Geotechnical Engineering
• Soil Mechanics
• Constitutive Modeling

Background:

• Cyclic triaxial experiments reveal complex long-term behaviors in porous media like clays under varying cyclic stress ratios (CSRs).
• Classifications include cyclic shakedown, cyclic stable, and cyclic failure, with limited existing models capturing deformation, pore pressure, hysteresis, and degradation.
• Accurate modeling of these phenomena is crucial for understanding soil response in cyclic loading scenarios.

Purpose of the Study:

• To develop an enhanced plasticity model capable of accurately describing and capturing the fundamental cyclic behaviors of clays.
• To incorporate novel elements for plastic modulus and damage into the model to distinguish between cyclic shakedown and failure.
• To reproduce closed hysteresis loops characteristic of clay behavior under cyclic loading.

Main Methods:

• Development of an enhanced plasticity model utilizing bounding surface and stress distance concepts.
• Introduction of a uniform interpolation function for the plastic modulus applicable across all loading stages.
• Incorporation of a new damage factor, linked to plastic shear strain and deformation type, into the plastic modulus.
• Implementation of a radial mapping rule with a moving projection center for simulating closed hysteresis loops.

Main Results:

• The proposed model successfully distinguishes between cyclic shakedown and cyclic failure.
• Degradation effects are effectively captured within the model's framework.
• Numerical results closely match experimental data, confirming the model's ability to reproduce key aspects of clay cyclic behavior.
• Closed hysteresis loops, characteristic of clays, are accurately reproduced.

Conclusions:

• The developed enhanced plasticity model provides a robust framework for simulating clay behavior under cyclic loading.
• The model's ability to capture critical aspects like shakedown, failure, degradation, and hysteresis validates its suitability for geotechnical applications.
• This approach advances the understanding and predictive capability of soil mechanics in cyclic stress conditions.