孔隙填充型深海能源土的离散元成样

ThreeDimensional Distinct Element Novel SamplePreparing Method and Mechanical Behavior for PoreFilling Type of Methane HydrateBearing Soil

摘要:

针对孔隙填充型水合物的赋存形态，提出了一种新的制备孔隙填充型能源土试样的数值成样方法.孔隙填充型水合物的砂性能源土试样是由砂粒和水合物颗粒混合而成的特殊的散粒体材料，具有明显的非连续特征.在土骨架的孔隙中，将水合物块体视为由颗粒通过强胶结作用凝聚而成的团簇整体，随机填充生成不同水合物饱和度的沉积物试样，开展能源土宏观力学特性的离散元固结排水三轴压缩试验模拟，并从应力应变、体变、接触组构等方面进行分析.结果表明，水合物饱和度的增大对低饱和度的孔隙填充型能源土试样的初始弹性模量和强度影响较小.有效围压相同时，孔隙填充型能源土试样的体积剪缩量随着水合物饱和度的增大而减小；而水合物饱和度相同时，能源土试样强度及体积剪缩量随着有效围压的增大而增大.能源土试样的剪胀角随有效围压的增大而近似线性减少，随水合物饱和度的增大而趋于线性增大.颗粒间接触方向随着轴向应变的增大而朝竖直方向偏转.

Abstract:

In view of the morphology of porefilling type of methane hydratebearing sediment (MHBS), this paper proposed a new technique for generating porefilling type of MHBS. Marine sandy sediments containing porefilling type MH particles can be considered as a class of special granular materials that present apparent obvious discontinuity characteristics. To numerically simulate such materials, the distinct element method (DEM) can be used by modeling MH particles as agglomerates of spheres cemented together and filled into the pores of soil skeleton based on the specific MH saturation. The drained triaxial compression tests with different MH saturation and effective confining pressures were conducted to analyze the mechanics, deformation characteristics and contact fabric of the porefilling type of MHBS. The results show that the influence of MH saturations on the initial elastic modulus and deviator stress is relatively small. The volume shrinkage decreases with increasing MH saturations under the same effective confining pressure while the strength and the volume shrinkage increase with the effective confining pressure increasing under the same MH saturation. The shear dilatancy angle almost linearly decreases with the increase of effective confining pressure, and it linearly increases with MH saturations increasing. The grain contact direction deflects to the vertical direction with the increase of axial strain.