Abstract
Submarine slope instability may be triggered by earthquakes and tsunamis. Methane hydrate sediments (MHS) are commonly buried under submarine slopes. Submarine slides would probably be triggered once the MHS are damaged under cyclic loading conditions. For this reason, it is essential to research the mechanical response of MHSs under dynamic loading conditions. In this study, a series of drained cyclic biaxial compressive tests with constant stress amplitudes were numerically carried out with the distinct element method (DEM). The cyclic loading number decreased as the hydrate saturation (Sh) increased when the MHS were damaged. The failure mode of the MHS was shown to be dependent on the dynamic stress amplitude and hydrate saturation. The microstructure of MHS during the cyclic loading shear process was also analyzed. The results can help us to understand the mechanical behavior of MHS during the cyclic loading process and develop micromechanical-based constitutive models.
Highlights
Methane hydrate is ice-like solid energy, which is generally founded in the subpermafrost and deep seabed where the pressure is high and the temperature is low
The main purpose of the present work was to obtain a better understanding of the microstructural evolution of methane hydrate-bearing sediments (MHS) under cyclic loading conditions and to aid in the development of micromechanical-based constitutive models
The cyclic loading number decreased as the hydrate saturation increased, when the MHS were damaged
Summary
Methane hydrate is ice-like solid energy, which is generally founded in the subpermafrost and deep seabed where the pressure is high and the temperature is low. In order to extract methane gas from the methane hydrate sediment, the methane hydrate needs to be dissociated first. Methane hydrates are very sensitive to the occurrence environment and can be dissociated when the pressure decreases and/or the temperature increases. There are three main production techniques including thermal injection, chemical injection, and depressurization. Due to the environmental sensitivity of methane hydrates, the extraction of methane hydrates from seabed sediments may create a geohazard. In order to mine methane hydrates safely, the mechanical properties of methane hydrate-bearing sediments (MHS) should be studied
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