Abstract: Natural gas hydrate is a new type of clean energy that has broad application prospects. However, the change of temperature and pressure conditions in the process of hydrate mining will cause the dissociation of hydrate, which lead to the loss of cementation strength of hydrate-bearing sediments. Meanwhile, micro-cracks and defects in the sediments expand gradually, the hydrates between the soil particles are damaged and broken in the loading process. However, in the previous investigations of the multi-field coupling model on hydrate dissociation process, the damage evolution process of sediment structure and its influence on the coupling process are ignored. Therefore, the Weibull distribution of three parameters and residual strength correction coefficient are introduced into the damage statistical constitutive model in this paper based on the continuous damage theory, and the damage statistical constitutive model of hydrate-bearing sediment considering the influence of damage threshold and residual strength is established. And then, the constitutive model is embedded in the multi-field coupling model of the hydrate dissociation process, and the thermo-hydro- mechanical-chemical (THMC) multi-field coupled mathematical model considering damage of hydrate-bearing sediments is proposed. Finally, based on the model, the influence of sediment structural damage on the deformation, pressure and temperature of sediment reservoirs during hydrate dissociation are discussed. It can be shown from the computational results that the structural damage of hydrate-bearing sediments has a significant effect on the multi-field coupling process about the dissociation of hydrates, and its influence increases gradually with the increase of dissociation time.

Key words: hydrate-bearing sediments, damage statistical constitutive model, multi-field coupling