Abstract For the safe exploration of natural gas hydrate, an understanding of the mechanical behaviors of methane hydrate-bearing sediments is essential. To date, the majority of the related research has focused on the mechanical properties of sandy sediments; research on fine sediments containing clay or silt is very limited, although more than 90% of gas hydrates are found in clay or silt. In this study, a novel discrete element method (DEM) model considering liquid bridge forces caused by the capillary water effect among particles is proposed and is used to simulate methane hydrate-bearing clayey silt sediments with pore-filling distribution. A series of DEM simulations of drained biaxial compression tests under different confining pressures is performed to investigate the mechanical behavior (i.e., the stress-strain relationship, the volumetric response, and strength properties such as friction angle and cohesion) of samples with different hydrate saturations. The numerical results reveal that methane hydrate-bearing clayey silt sediments are characterized by strain-hardening behavior with shear contraction. In addition, the liquid bridge forceincreases with methane hydrate saturation, which considerably enhances cohesion while making no significant contribution to the internal friction angles. The presence of methane hydrates in the pores can increase the failure strength of the sediments, while the initial stiffness is slightly affected by methane hydrate saturation when the latter ranges from 10% to 30%.

中文翻译：

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考虑液桥力的离散元模拟研究含甲烷水合物粘土质粉砂沉积物的力学行为

摘要 对于天然气水合物的安全勘探，了解含甲烷水合物沉积物的力学行为至关重要。迄今为止，大部分相关研究都集中在砂质沉积物的力学性质上；尽管 90% 以上的天然气水合物都存在于粘土或粉砂中，但对含有粘土或粉砂的细粒沉积物的研究非常有限。在这项研究中，提出了一种新的离散元法 (DEM) 模型，该模型考虑了颗粒间毛细管水效应引起的液桥力，并用于模拟具有孔隙填充分布的含甲烷水合物的粘土质粉砂沉积物。对不同围压下的排水双轴压缩试验进行了一系列 DEM 模拟，以研究力学行为（即应力-应变关系、具有不同水合物饱和度的样品的体积响应和强度特性（如摩擦角和内聚力）。数值结果表明，含甲烷水合物的粘土质粉砂沉积物具有应变硬化和剪切收缩的特征。此外，液桥力随着甲烷水合物饱和度的增加而增加，这大大增强了内聚力，而对内摩擦角没有显着贡献。孔隙中甲烷水合物的存在可以增加沉积物的破坏强度，而当甲烷水合物饱和度在10%～30%之间时，初始刚度受甲烷水合物饱和度的影响较小。数值结果表明，含甲烷水合物的粘土质粉砂沉积物具有应变硬化和剪切收缩的特征。此外，液桥力随着甲烷水合物饱和度的增加而增加，这大大增强了内聚力，而对内摩擦角没有显着贡献。孔隙中甲烷水合物的存在可以增加沉积物的破坏强度，而当甲烷水合物饱和度在10%～30%之间时，初始刚度受甲烷水合物饱和度的影响较小。数值结果表明，含甲烷水合物的粘土质粉砂沉积物具有应变硬化和剪切收缩的特征。此外，液桥力随着甲烷水合物饱和度的增加而增加，这大大增强了内聚力，而对内摩擦角没有显着贡献。孔隙中甲烷水合物的存在可以增加沉积物的破坏强度，而当甲烷水合物饱和度在10%～30%之间时，初始刚度受甲烷水合物饱和度的影响较小。