Implementation of a Nonlinear State–Dilatancy Law in the NorSand Model

Abstract

The original NorSand (ONS) state-dilatancy law (ONS-SDL) presents challenges when trying to make changes in the formulation of the critical state line or stress–dilatancy rule and the associated yield surface. Additionally, using this law in its current form limits the model's applicability to a specific range of initial state parameters. Due to these limitations, using a higher state–dilatancy parameter for loose samples to improve the undrained response is often not possible. This paper provides a review of the ONS-SDL, and the requirements of a state–dilatancy law in Cambridge-type models in a more explicit way. A comprehensive analysis is then conducted to examine the effects of the chosen law on the model's formulation, its range of applicability, and its effectiveness in simulating undrained responses of loose samples. To address the limitations, a new nonlinear state–dilatancy law is introduced, offering improved responses and enhanced flexibility. This not only improves the model's performance but also allows for the utilization of different stress–dilatancy rules in future models, providing greater flexibility and adaptability. The improvements made by the new formulation have been highlighted by demonstrating the modified version's capabilities in simulating the mechanical behavior of two different sands.