一个深海能源土的温度–水压–力学二维微观胶结模型

A two-dimensional thermal-hydro-mechanical bond contact model for methane hydrate bearing soils

天然气水合物以胶结形式赋存时,对深海能源土的强度和变形特性影响显著,且其影响程度与所处温度、水压与力学环境密切相关。旨在建立可考虑温(温度)–压(水压)–力(力–位移与胶结破坏准则)耦合影响的深海能源土微观胶结模型。首先,依据能源土中水合物胶结可发生于两种接触形式(直接接触与有间距)的土颗粒间,提出适用于两种胶结模式的力–位移准则和胶结破坏准则。其次,提出温压距离参数L(表示在无量纲化处理后的温度–水压坐标平面,土体所处温度与水压点到水合物相平衡线的最小距离),并依据文献资料分析,建立水合物胶结强度、刚度与参数L间的关系。最后,建立由水合物饱和度确定的粒间水合物胶结尺寸计算方法,并据此进一步建立了胶结强度与刚度同水合物饱和度间的关系。该模型可以方便地植入离散元程序,从而用于深海能源土的宏微观力学分析。

The strength and deformation of methane hydrate bearing soils are influenced by their inter-particle cemented hydrate, the extent of which depends on the surrounding temperature, pore-water pressure and mechanical environment. It is aimed to establish a thermal-hydro-mechanical bond contact model for methane hydrate bearing soils. Firstly, contact force-displacement laws and bond failure criteria are presented according to two types of bond modes that methane hydrate may present. Secondly, the strength and stiffness of inter-particle cemented hydrate are studied with respect to the parameter L which identifies the minimum distance from a point to the phase equilibrium line in the coordinate system with ordinate being dimensionless pore-water pressure and abscissa being dimensionless temperature. Finally, the size of cemented hydrate is calculated corresponding to the methane hydrate saturation. The proposed bond contact model can be easily implemented into the distinct element method(DEM), providing an efficient tool for investigating the macro- and micro-mechanical behaviors of methane hydrate bearing soils.