Experimental research on the mechanical properties of methane hydrate-bearing sediments during hydrate dissociation

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• 作者：Yongchen Song ; Yiming Zhu ; Weiguo Liu ; Jiafei Zhao ; Yanghui Li ; Yunfei Chen ; Zhitao Shen ; Yan Lu ; Chongming Ji
• 关键词：Methane hydrate-bearing sediments ; Hydrate dissociation ; Mechanical properties ; Mohr&ndash ; Coulomb criterion
• 刊名：Marine and Petroleum Geology
• 出版年：March, 2014
• 年：2014
• 卷：51
• 期：Complete
• 页码：70-78
• 全文大小：1207 K

文摘

This paper describes studies of the effect of hydrate dissociation on the safety and stability of methane hydrate-bearing sediments. Methane hydrates within the sediments were dissociating under the conditions of a confining pressure of 0.5聽MPa, 1聽MPa, 2聽MPa and a temperature of 鈭?聽掳C. After 6聽h, 24聽h, or 48聽h, a series of triaxial compression tests on methane hydrate-bearing sediments were performed. The tests of ice-clay and sediments without hydrate dissociation were performed for comparison. Focusing on the mechanical properties of the sediments, the experimental results indicated that the shear strength of the ice-clay mixtures was lower than that of the methane hydrate-bearing sediments. The strength of the sediments was reduced by hydrate dissociation, and the strength tended to decrease further at the lower confining pressures. The secant modulus E_S of the sediments dropped by 42.6% in the case of the dissociation time of the hydrate of 48聽h at the confining pressure of 1聽MPa; however, the decline of the initial yield modulus E₀ was only 9.34%. The slower hydrate dissociation rate contributed to reducing the failure strength at a declining pace. Based on the Mohr-Coulomb strength theory, it was concluded that the decrease in strength was mainly affected by the cohesive reduction. Moreover, the mathematical expression of the M-C criterion related to the hydrate dissociation time was proposed. This research could be valuable for the safety and stability of hydrate deposits in a permafrost region.