基于离散元法的水合物沉积物双轴压缩试验模拟分析

Simulation Analysis of Biaxial Compression of Hydrate-Bearing Sediments Based on Discrete Element Method

摘要: 水合物沉积物可看作砂粒和水合物颗粒组成的混合散体材料，其力学行为的研究属于典型的不连续问题，离散元法是求解该问题的有效途径。本文基于离散元数值模拟软件PFC2D制备了饱和度为15%、25%、35%、45%的水合物沉积物DEM试样，并对其进行了双轴压缩离散元模拟试验，研究了在不同水合物饱和度和有效围压情况下，水合物沉积物的强度和变形特性。试验结果表明：在较低饱和度条件下，水合物沉积物会表现出明显的应变软化现象，而随着饱和度的增大，其应力–应变曲线会由应变软化向应变硬化过渡；水合物沉积物的峰值应力、初始弹性模量会随着饱和度和有效围压的增大而增大；水合物饱和度对沉积物的内聚力和摩擦角都有影响，但沉积物的强度主要是由内聚力的变化影响的。

Abstract: Hydrate-bearing sediments can be regarded as a class of mixed granular material forming with sand and hydrate particles, which is a typically discontinuous problem. The discrete element method is an effective way to solve the problem. The DEM samples of hydrate-bearing sediments with saturation of 15%, 25%, 35% and 45% were prepared by discrete element numerical simulation software PFC2D, and the biaxial compression discrete element simulation experiments were carried out. The strength and deformation characteristics of saturation and effective confining pressure on the mechanical properties of hydrate-bearing sediments were studied. The experiments results show that there is strain softening phenomenon appearing under low saturation condition, and with the increase of the saturation, the stress-strain curve would transit from strain softening to strain hardening. The peak stress and initial elastic modulus of the hydrate-bearing sediments increase upon the increased saturation and effective confining pressure. The cohesion and friction angle of the sediments are affected by the hydrate saturation, but the strength of the sediments is mainly affected by cohesion.