Stress-strain response of hydrate-bearing sands: Numerical study using discrete element method simulations
Stress-strain response of hydrate-bearing sands: Numerical study using discrete element method simulations
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DOI：
10.1029/2011jb009040
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发表时间：
2012-04
影响因子：
--
通讯作者：
Jongwon Jung;J. Santamarina;K. Soga
中科院分区：
文献类型：
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作者：
Jongwon Jung;J. Santamarina;K. Soga
[1]天然气水合物是一种存在于海洋和冻土层下沉积物中的结晶固体。虽然水合物的存在可能对沉积物性质产生深远的影响，但由于实验室测试的固有局限性，对含水合物沉积物的应力-应变行为知之甚少。在这项研究中，我们使用数值模拟，以提高我们的理解的力学行为的水合物轴承砂。水合物质量被模拟为小的随机分布的结合颗粒或作为“成熟水合物”形成斑片状饱和度，从而具有100%孔隙填充水合物饱和度的沉积物簇分布在无水合物沉积物内。模拟结果表明，砂体孔隙率的降低和水合物饱和度的提高导致砂体刚度、强度和膨胀趋势的增加，临界州线向孔隙比和剪切强度方向移动。特别是斑块状饱和砂体的临界状态摩擦角增大，而水合物分布在孔隙中时对表观凝聚力的影响最大。片状水合物分布的沉积物表现出比随机分布的水合物沉积物略低的强度。最后，排水条件下的水合物分解导致体积收缩和/或应力松弛，和显着的剪切应变可以开发，如果水合物轴承砂在分解过程中受到偏载。
[1] Gas hydrate is a crystalline solid found within marine and subpermafrost sediments. While the presence of hydrates can have a profound effect on sediment properties, the stress-strain behavior of hydrate-bearing sediments is poorly understood due to inherent limitations in laboratory testing. In this study, we use numerical simulations to improve our understanding of the mechanical behavior of hydrate-bearing sands. The hydrate mass is simulated as either small randomly distributed bonded grains or as “ripened hydrate” forming patchy saturation, whereby sediment clusters with 100% pore-filled hydrate saturation are distributed within a hydrate-free sediment. Simulation results reveal that reduced sand porosity and higher hydrate saturation cause an increase in stiffness, strength, and dilative tendency, and the critical state line shifts toward higher void ratio and higher shear strength. In particular, the critical state friction angle increases in sands with patchy saturation, while the apparent cohesion is affected the most when the hydrate mass is distributed in pores. Sediments with patchy hydrate distribution exhibit a slightly lower strength than sediments with randomly distributed hydrate. Finally, hydrate dissociation under drained conditions leads to volume contraction and/or stress relaxation, and pronounced shear strains can develop if the hydrate-bearing sand is subjected to deviatoric loading during dissociation.