Constitutive model for gas hydrate-bearing soils considering different types of hydrate morphology and prediction of strength-band
Constitutive model for gas hydrate-bearing soils considering different types of hydrate morphology and prediction of strength-band
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DOI：
10.1016/j.sandf.2021.101103
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发表时间：
2022-02
影响因子：
3.7
通讯作者：
Hiromasa Iwai;T. Kawasaki;Feng Zhang
中科院分区：
文献类型：
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作者：
Hiromasa Iwai;T. Kawasaki;Feng Zhang
本研究提出了一种新的弹塑性本构模型，考虑不同类型的水合物在孔隙空间。在过去的几十年里，对含甲烷水合物和含二氧化碳水合物的土壤进行了许多三轴压缩试验。研究表明，含甲烷水合物和含二氧化碳水合物的土壤，即使水合物含量相同，其强度和水化性质也不同。其原因可能是由于不同类型的水合物形态。因此，在这项研究中，水合物形态对含天然气水合物沉积物的力学响应的影响，通过模型分析，考虑到不同的硬化规则对应于每种类型的水合物形态。为了评估所提出的模型的能力，它是适用于过去的三轴压缩试验的结果，含甲烷水合物和二氧化碳水合物含砂试样。结果表明，该模型在不改变拟合参数的情况下，仅考虑不同形态分布，就能成功地再现不同的应力-应变关系和塑性行为。然后，该模型被用来预测一个可能的范围内的最大偏应力可以移动各种水合物形态比，该范围被定义为强度带。由本构模型得到的最大偏应力预测曲线与以往试验得到的经验公式相吻合。这支持了水合物形态比随总水合物饱和度变化的事实。这些发现将有助于更好地理解含天然气水合物沉积物的微观结构与宏观力学行为之间的关系。
The present study proposes a new elasto-plastic constitutive model that considers different types of hydrates in pore spaces. Many triaxial compression tests on both methane hydrate-bearing soils and carbon dioxide hydrate-bearing soils have been carried out over the last few decades. It has been revealed that methane hydrate-bearing soils and carbon dioxide hydrate-bearing soils have different strength and dilatancy properties even though they have the same hydrate contents. The reason for this might be due to the different types of hydrate morphology. In this study, therefore, the effect of the hydrate morphology on the mechanical response of gas-hydrate-bearing sediments is investigated through a model analysis by taking into account the different hardening rules corresponding to each type of hydrate morphology. In order to evaluate the capability of the proposed model, it is applied to the results of past triaxial compression tests on both methane hydrate-containing and carbon dioxide hydrate-containing sand specimens. The model is found to successfully reproduce the different stress–strain relations and dilatancy behaviors, by only giving consideration to the different morphology distributions and not changing the fitting parameters. The model is then used to predict a possible range in which the maximum deviator stress can move for various hydrate morphology ratios; the range is defined as the strength-band. The predicted curve of the maximum deviator stress obtained by the constitutive model matches the empirical equations obtained from past experiments. It supports the fact that the hydrate morphology ratio changes with the total hydrate saturation. These findings will contribute to a better understanding of the relation between the microscopic structures and macro-mechanical behaviors of gas-hydrate-bearing sediments.