Study on the mechanical properties of hydrate-bearing silty clay

Abstract

The mechanical properties are important for the evaluation of stratum deformation and instability in hydrate exploitation. By using an integrated test apparatus for synthesis of hydrate sediment and tri-axial tests, a series of compression tests is conducted on the silty clay containing tetrahydrofuran hydrate (SCTH) similar to that of South China Sea. The stress–strain curves and Mohr circles are obtained at different degree of hydrate saturations and confining pressures. The silty clay containing tetrahydrofuran hydrate shows typical ductile behavior, the shear strength increases linearly with the increase of hydrate saturation and confining pressure. The secant modulus increases with the increase of hydrate saturation. The shear strength is analyzed based on the Drucker–Prager criterion, Mohr–Coulomb criterion, Lade–Duncan criterion, while the secant modulus is analyzed using the mixed law of composite materials. It is shown that the strength can be well described by the Drucker–Prager criterion and Mohr–Coulomb criterion, and the secant modulus is close to the harmonic average of the modulus of soil skeleton and hydrate in SCTH.