The Effects of Hydrate on the Strength and Stiffness of Some Sands
The Effects of Hydrate on the Strength and Stiffness of Some Sands
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DOI：
10.1029/2018jb015880
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发表时间：
2019-01
期刊：
影响因子：
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通讯作者：
B. N. Madhusudhan;C. R. I. Clayton;J. Priest
中科院分区：
文献类型：
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作者：
B. N. Madhusudhan;C. R. I. Clayton;J. Priest
天然气水合物几乎可以与海底沉积物同时形成。它们对深海沉积物具有显著的硬化和强化作用。随后的原位温度升高或压力降低可能引发水合物解离，导致沉积物的强度和刚度大幅降低，并可能导致海底不稳定。气体水合物解离不仅可以去除固井。它还会释放淡水和大量被困气体，这取决于多种因素，如沉积物类型、可用孔隙空间、水合物形态和水合物饱和度。在已知的海底不稳定区域出现麻袋痕迹表明，水合物解离可能是在这些位置触发破坏的一个因素。在回顾了海底沉积物的强度和刚度在分离过程中可能发生变化的机制之后，本文报告了实验室测试的结果，以评估水合物水泥损失对强度和刚度的影响，使用实验室气体水合物三轴仪，对一系列具有不同粒径、比表面积和颗粒形状的砂级材料进行了测试。结果表明，水合物胶结颗粒材料的强度和刚度受水合物胶结比表面积的显著影响，并在一定程度上受颗粒形状的影响。较低比表面积的均匀粗颗粒沉积物在水合物解离过程中刚度和强度损失较大，由膨胀型变为收缩型。颗粒较细的沉积物受离解作用的影响较小。
Gas hydrates can form more or less at the same time as seafloor sediment. They can have the effect of significantly stiffening and strengthening deep‐ocean sediments. Subsequent increases in situ temperature or decreases in pressure may trigger hydrate dissociation, leading to large reductions in the strength and stiffness of the sediment and possible seafloor instability. Gas hydrate dissociation not only removes cementing. It also releases freshwater and significant amounts of trapped gas that are dependent on multiple factors such as type of sediment, available pore space, hydrate morphology, and hydrate saturation. The presence of pock marks in areas of known seabed instability suggests that hydrate dissociation may have been a factor in triggering failure at these locations. Having reviewed the mechanisms by which the strength and stiffness of seabed sediment may be changed during dissociation, this paper reports the results of laboratory testing to evaluate the effects of loss of hydrate cement on strength and stiffness, for a range of sand‐sized materials with differing particle size, specific surface area, and particle shape, using a laboratory gas hydrate triaxial apparatus. The results suggest that both the strength and the stiffness of hydrate‐cemented granular materials are affected significantly by the specific surface available for hydrate cementation and, to a certain extent, by the particle shape. Uniform coarse granular sediments of lower specific surface area can suffer significant loss of stiffness and strength upon hydrate dissociation, changing the sediment from dilative to contractive. Finer‐grained sediments appear less affected by dissociation.