This experimental study investigates the geomechanical stability of methane hydrate-bearing sediments (MHBS) during hydrate dissociation. Two MHBS specimens were prepared using sand and 5 wt% clay mixtures, and both with a targeted hydrate saturation of $\sim$40%. The two specimens were initially subjected to two different deviator stresses, i.e., one below the strength of host sediment (stable) and the other above that but below the strength of the hydrate-bearing sediment (metastable). After the initial shearing, a sequential process of depressurization, re-pressurization (pore pressure recovery), and re-shearing was conducted. During the tests, stress, strain, and hydrate saturation were continuously measured, together with P- and S-wave velocities at each critical step of the tests. Experimental results showed that during hydrate dissociation via depressurization, the specimens underwent volumetric contractions. During the re-pressurization, however, the specimen under a higher initial deviator stress (i.e., under metastable state) failed, whereas the other specimen under a lower initial deviator stress (i.e., under stable state) remained stable. The specimen under the stable state, seemingly having a small amount of reformed hydrates after the re-pressurization, was able to sustain the re-shearing up to a shear stress that is comparable to the shear strength of its host sediment.

这项实验研究调查了水合物分解过程中含甲烷水合物沉积物（MHBS）的地质力学稳定性。使用沙子和5 wt％的粘土混合物制备了两个MHBS标本，目标水合物饱和度均为$〜$40％。最初，这两个标本受到两种不同的偏应力，即一个低于主体沉积物的强度（稳定），另一个高于但不含水合物的沉积物的强度（可置换）。初始剪切后，进行降压，重新加压（恢复孔压）和重新剪切的顺序过程。在测试过程中，在测试的每个关键步骤均连续测量应力，应变和水合物饱和度以及P波和S波速度。实验结果表明，在通过减压进行水合物分解过程中，标本经历了体积收缩。但是，在重新加压过程中，样品在较高的初始偏斜应力下（即在亚稳态下）会失效，另一个样品在较低的初始偏斜应力下（即在稳定状态下）保持稳定。样品在稳定状态下，似乎在重新加压后具有少量的重整水合物，能够承受重新剪切直至达到与其宿主沉积物的剪切强度相当的剪切应力。