可燃冰沉积物力学特性的离散元模拟分析

Discrete Element Simulation Analysis of Mechanical Behavior of the Gas Hydrate-Bearing Sediments

摘要: 孔隙填充型可燃冰沉积物可作为由砂粒与可燃冰颗粒组成的混合散体材料，其力学行为研究属于典型的非连续问题。针对该非连续问题，本文基于颗粒流软件PFC3D提出一种制备混合散体材料离散元试样的新方法。利用此方法制备了可燃冰沉积物DEM试样，对不同围压下的可燃冰沉积物试样，进行了一系列三轴压缩试验的数值模拟计算，分析了在不同围压和不同饱和度下可燃冰沉积物的力学特性。研究结果表明：本文提出的DEM模拟方法能够较好地反映可燃冰沉积物的力学特性。在相同饱和度下，可燃冰沉积物的初始弹性模量、峰值强度、峰值应变和残余强度均随着围压增大而增大，不同围压下的应力-应变曲线变化趋势基本相同；在同一饱和度下，可燃冰沉积物的峰值应变随着围压的增大而增大。在不同饱和度下，可燃冰沉积物的峰值应变基本都有随着围压增大而线性增长的趋势，围压的增加有助于改善可燃冰沉积物的受压变形能力。

Abstract: Pore-filling type of combustible ice-bearing sediment can be regarded as a class of mixed granular material forming with sand and hydrate particles, which is a typically discontinuous problem. In view of discontinuous problem, this paper proposed a new technique for generating pore-filling type of combustible ice-bearing sediment by the particle flow software PFC3D. A series of numerical simulations of triaxial compression simulation experiments are performed on gas hydrate bearing sediments to investigate the mechanical properties of combustible ice-bearing sediment under different confining pressure. The study shows that the DEM simulation for preparing sample is able to capture the mechanical characteristics of combustible ice-bearing sediment. The initial elastic modulus, peak stress peak strain and residual strength of combustible ice-bearing sediment increase upon the increased confining pressure. The trend of the change of stress-strain curves is similar. The peak strain of combustible ice-bearing sediment increases with the confining pressure increasing when the value of combustible ice saturation is same. The peak strain of combustible ice-bearing sediment increases linearly with the confining pressure increasing when the value of combustible ice saturation is different. The increase of confining pressure helps to improve the compressive deformation capacity of combustible ice-bearing sediment.