The methane hydrate is considered as an encouraging new energy resource because of its huge amount of reserves. Especially, it would be available under the ocean floors in the Pacific Ocean around Japan Islands. However, the reckless mining development might cause serious disasters such as sliding or mass movement of seabed. To prevent such disasters due to the methane hydrate mining development, it is necessary to understand its mechanical properties from the geotechnical viewpoint. In this paper, the relationship between compressive strength and density of methane hydrate is discussed. Based on the triaxial compression test results under low temperature and high pressure, static shear behaviors of methane hydrate and ice are compared. Compressive strength of methane hydrate increases as decreasing temperature or increasing pressure and it also increases as increasing density of methane hydrate specimen. Compressive strength of ice also increases as decreasing temperature or increasing pressure at low density, however, it rarely increases at high density. Through the above discussion, the void condition of methane hydrate is supposed to be different from that of ice at the same density.
Methane hydrate is a crystal of ice and methane molecules are taken in a cage encaged in a called cluster structure that water molecules construct under low temperature and high pressure. In recent years, it is being considered as an encouraging new energy resource to replace oil and natural gas, because of such the huge amounts of reserves as are estimated that it is to be sufficient to last over 100 years based on present levels of natural gas consumption. Especially, it would be found at the edge of the tectonic plates around Japanese Islands under the ocean floors in the Pacific Ocean (Matsumoto et al., 1993). Methane hydrate is stable under low temperature and high pressure.
