Disturbed State Concept-Based Model Incorporating Strain-Softening Behavior for Gas Hydrate Sediments

Abstract

Gas extraction from methane hydrate reservoirs results in significant changes to pore pressure, causing soil deformation and progressive failure. Current advanced constitutive models, which are capable of capturing this deformation process, are often complex, computationally expensive, and challenging to implement in numerical solvers. Hence, simpler models are generally preferred; however, these models fail to predict critical geomechanical aspects such as strain softening and dilation. To address this limitation, the present study proposes a unified constitutive model based on the disturb state concept (DSC), considering the state variables such as hydrate saturation, temperature, and effective confining pressure for gas hydrate sediments. The stress−strain relationship is derived by combining two distinct responses: a hyperbolic hardening response that extends the stress−strain behavior prior to the peak stress state and a DSC approach to capture the post-peak softening and dilation response. Furthermore, the model is rigorously validated by utilizing multiple sets of triaxial experimental data of gas hydrate sediments under different initial conditions. This comprehensive validation process ensured the robustness and reliability of the proposed model. Finally, the efficacy of the model is analyzed based on the energy absorption capacity and index of agreement approach.