Application of an Elasto-viscoplatic Model to the Gas Hydrate-bearing Soil

Methane hydrates are ice-like materials composed of methane and water which naturally exist in the permafrost sediments and the deep seabed ground. They are presently viewed as a potential energy resource for the 21st century because an amount of methane gas is trapped in hydrate reservoirs around Nankai trough and Japan sea. Recently, the world’s first offshore production test from methane hydrates bearing sediments by the de-pressurization method have been conducted off the coasts of Atsumi and Shima peninsula in Japan. In the present study, an elasto-viscoplastic model for soil is applied to the triaxial test results of the hydrate-bearing sandy soils as well as the pure hydrate samples. In the model, softening due to structural degradation and hydrate bonding effect are taken into consideration. Simulation results show the applicability of the model to the hydrate-bearing soil as well as the pure methane hydrate.