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含填充型水合物的砂性能源土可视为特殊的散粒体材料(砂粒和水合物颗粒混合物),具有明显的非连续特征。在离散元中若采用团粒(胶结成团的颗粒组)模拟填充水合物颗粒则需合理确定团粒结构内颗粒间胶结模型参数。为此,基于前人的室内纯水合物三轴试验资料进行离散元建模与参数反演。结果表明,宜采用松散且颗粒间摩擦系数较小的试样模拟水合物块体,当颗粒间摩擦系数小于等于0.04时,可确保无胶结试样的内摩擦角小于室内试验获得的纯水合物内摩擦角。胶结刚度只需在较小范围变化即可反映相同温度不同围压条件下的弹性特性,且微观刚度参数与胶结强度参数的相互作用较小,可以假定二者相互独立。通过选取不同的微观胶结强度值进行不同围压下的三轴压缩试验,建立微观胶结强度参数与宏观参数(内摩擦角和黏聚力)之间的关系,从而确定与室内试验强度特性相符合的微观胶结强度值,实现甲烷水合物三轴试验离散元模拟;由体变规律可知,甲烷水合物在发生剪胀前均存在一个初始的体积收缩阶段,且剪胀特性随着围压的减小而呈现增强趋势。通过微观变量颗粒接触方向组构的分布图可知,随着轴向应变增大,颗粒间接触主方向朝竖直方向偏转,表现出明显的各向异性特性。随着轴向应变的增大,颗粒间胶结残余率变小,表明试样逐步破坏。
Sandy energy-containing soils containing filled hydrates can be considered as special particulate materials (mixtures of grit and hydrate particles) with distinct discontinuities. In the discrete element, if the agglomeration of particles (agglomerated agglomerates) is used to simulate the filling of hydrate particles, the parameters of intergranular cementing model within the agglomerate structure must be reasonably determined. For this reason, the discrete element modeling and parameter inversion are based on the previous triaxial test data of pure hydrate indoors. The results show that it is advisable to use a loose sample with small friction coefficient to simulate the hydrate block. When the friction coefficient between particles is 0.04 or less, the internal friction angle of the cementless sample can be ensured to be smaller than the pure hydration Internal friction angle. The cementation stiffness can reflect the elastic properties under different confining pressures at the same temperature with only a small change in range, and the interaction between the micro-rigidity parameters and the cementation strength parameters is small, so the two can be assumed to be independent of each other. By selecting different values of micro-cemented strength for triaxial compression tests under different confining pressures, the relationship between micro-cemented strength parameters and macroscopic parameters (internal friction angle and cohesion) was established to determine the strength characteristics in laboratory tests The results show that the methane hydrate has an initial volume shrinkage stage before dilatancy, and the dilatancy characteristic decreases with the decrease of confining pressure Small and showing an increasing trend. According to the distribution of microstructural contact orientation of micro-particles, it can be seen that as the axial strain increases, the main directions of the contact between the particles are deflected in the vertical direction, showing obvious anisotropy. As the axial strain increases, the residual rate of intergranular cementation becomes smaller, indicating that the specimen is gradually destroyed.