Salinity effects on the mechanical behaviour of methane hydrate bearing sediments: A DEM investigation

Abstract The stability of methane hydrate depends on not only temperature and pressure but also the salinity of the environment where the methane hydrate exists. The variation in the stability of methane hydrate due to the change in salinity induces mechanical response in micro scale of the methane hydrate-bearing sediments (MHBS). However, it is really heard to quantitatively analyze this effect by controlling salinity of the MHBS in micro scale experiment. Therefore, our study applies Distinct Element Method to investigate the micro-scale mechanical response subject to the salinity variation. An existing contact model for cemented soils is extended to explicitly include the effects of salinity on bond strength and modulus, which are verified by experimental data. Using the proposed thermo-hydro-mechanical-chemical contact model, we conducted a series of case studies to investigate macroscopic and microscopic mechanical responses during three different stress paths, i.e. isotropic, triaxial and constant stress ratio tests. The results show that as the salinity increases, the shear strength and stiffness decrease while the deformation and bond breakage ratio accelerate. The results are valuable to develop constitutive models for MHBS and have safe exploitation of MH resources in the future.