Critical state soil constitutive model for methane hydrate soil

TLDR

Methane hydrate‑bearing soil shows increased stiffness, strength, and dilatancy similar to dense or bonded soils, yet this resistance diminishes under excessive compression or bond failure during shearing. The study introduces the Methane Hydrate Critical State (MHCS) model to simulate the mechanical behavior of methane hydrate‑bearing soil. The MHCS model extends the conventional critical state framework by incorporating five additional parameters to capture hydrate‑soil interactions. Volumetric yielding was found to be crucial for accurately predicting ground settlement during depressurization, as changes in effective stress and hydrate saturation significantly affect methane hydrate‑bearing soils.

Abstract

This paper presents a new constitutive model that simulates the mechanical behavior of methane hydrate‐bearing soil based on the concept of critical state soil mechanics, referred to as the “Methane Hydrate Critical State (MHCS) model”. Methane hydrate‐bearing soil is, under certain geological conditions, known to exhibit greater stiffness, strength and dilatancy, which are often observed in dense soils and also in bonded soils such as cemented soil and unsaturated soil. Those soils tend to show greater resistance to compressive deformation but the tendency disappears when the soil is excessively compressed or the bonds are destroyed due to shearing. The proposed model represents these features by introducing five extra model parameters to the conventional critical state model. It is found that, for an accurate prediction of ground settlement, volumetric yielding plays an important role when hydrate soil undergoes a significant change in effective stresses and hydrate saturation, which are expected during depressurization for methane gas recovery.