深海能源土剪切带形成机理离散元分析

DEM analysis on formation of shear band of methane hydrate bearing soils

天然气水合物的分解开采过程将会劣化深海能源土的力学性能,从而引发一系列岩土工程问题。因此,要实现天然气水合物的安全开采,需要对能源土的强度和变形特性开展研究。结合深海能源土微观胶结模型,通过平面应变双轴试验的离散元模拟,研究了深海能源土剪切带形成机理以及剪切带内外的宏微观变量特征。结果表明:水合物胶结提升了深海能源土的强度,且使其呈现出明显的应变软化特性;剪切带在峰值应力后开始产生,伴随着胶结的大量破坏以及各宏微观变量的局部化;剪切带内外各宏微观变量差异明显,随着轴向应变的增加,土体微观结构也随之发生变化。

Methane hydrate(MH) decomposition and mining will worsen the mechanical behavior of methane hydrate bearing soil(MHBS) and cause a series of geotechnical problems.Therefore,in order to facilitate safe exploitation of MH,it is crucial to understand the strength and deformation characteristics of MHBS.Based on the bond model of MHBS,the distinct element method(DEM) is used in planar biaxial compression tests to analyze the formation of shear band as well as some micro and macro variables of MHBS within and outside the shear band.The results show that methane hydrate increases the strength of MHBS and leads to strain-softening behavior; the shear band is fully developed after the peak stress,accompanied by massive bond breakage and localization of other micro variables; the micro and macro variables within and outside the shear band differ.Besides,with the increase of axial strain,the micro structure of MHBS changes.