Mechanical instability of monocrystalline and polycrystalline methane hydrates

Mechanical instability of monocrystalline and polycrystalline methane hydrates

Wu, J.
Ning, F.
Trinh, T.T.
Kjelstrup, S.
Vlugt, T.J.H.
He, J.
Skallerud, B.H.
Zhang, Z.

Mechanical, Maritime and Materials Engineering

Process and Energy

2015-11-02

Despite observations of massive methane release and geohazards associated with gas hydrate instability in nature, as well as ductile flow accompanying hydrate dissociation in artificial polycrystalline methane hydrates in the laboratory, the destabilising mechanisms of gas hydrates under deformation and their grain-boundary structures have not yet been elucidated at the molecular level. Here we report direct molecular dynamics simulations of the material instability of monocrystalline and polycrystalline methane hydrates under mechanical loading. The results show dislocation-free brittle failure in monocrystalline hydrates and an unexpected crossover from strengthening to weakening in polycrystals. Upon uniaxial depressurisation, strain-induced hydrate dissociation accompanied by grain-boundary decohesion and sliding destabilises the polycrystals. In contrast, upon compression, appreciable solid-state structural transformation dominates the response. These findings provide molecular insight not only into the metastable structures of grain boundaries, but also into unusual ductile flow with hydrate dissociation as observed during macroscopic compression experiments.

earth sciences
materials science
geology and geophysics

http://resolver.tudelft.nl/uuid:031cb33e-fe98-4e57-ba90-8a7bc3e3262b

Nature Publishing Group

2041-1723

http:dx.doi.org/10.1038/ncomms9743

Nature Communications, 6, 2015

Institutional Repository

journal article

(c) 2015 This work is licensed under a Creative Commons Attribution 4.0 International License