Abstract: The existence and decomposition of hydrates have two-sided effects on the shear strength of marine energy soil. To investigate the effect of hydrate on the strength of marine energy soil, an expression of the cohesion of marine energy soil is proposed in consideration of the type and occurrence mode of hydrate. As the presence of hydrates increases the contact area between soil particles, the concept of cemented area ratio is introduced to revise the expression of effective stress on account of the influence of hydrate via theoretical derivation. Based on the Mohr-Coulomb criterion, the relation of shear strength varying with hydrate saturation is obtained. In addition, the expression of pore pressure after hydrate decomposition is deduced considering the dissolution of methane gas. The rationality of the proposed expression is verified through triaxial shear test of sediments and numerical simulation of hydrate decomposition. The results conclude that the present expression well reflects the impacts of hydrate content, hydrate occurrence state, and high water-pressure on the strength of marine energy soil; meanwhile, the corrected pore pressure model is helpful to better analyze the stability of submarine slope.

Key words: deep sea energy soil, hydrate, effective stress, cohesion, shear strength, excess pore pressure