不同温压环境下深海能源土力学特性离散元分析

深海能源土宏观力学特性与所处温度与水压环境密切相关,明晰温压对能源土力学特性的影响对水合物的安全开采具有重要意义。首先,介绍深海能源土的温度-水压-力学微观胶结模型,用以描述能源土粒间的水合物胶结接触力学特性;其次,将该模型导入至离散元商业软件PFC2D中,开展不同温度与水压环境下的离散元双轴试验;最后,结合离散元双轴试验结果及同已有室内试验结果的对比分析,探讨温度与水压对深海能源土宏观力学特性的影响规律和微观作用机理。结果表明：引入胶结模型的离散元双轴试验可较好地描述深海能源土强度、变形等力学特性随温度与水压的变化关系;温度与水压影响深海能源土宏观力学特性的微观机理是颗粒间水合物胶结强度与刚度同温度与水压间的相关性;建议采用温压距离参数L（在无量纲化的温度-水压坐标平面内,水合物赋存温度与水压点至其相平衡线的最小距离）评价实际复杂温压场下的深海能源土宏观力学特性。

DEM investigation on mechanical properties of methane hydrate bearing soils under different temperatures and pore-water pressures

Mechanical properties of methane hydrate bearing soils (MHBS) are influenced by the surrounding temperature (T) and pore-water pressure (σ_w). Study on such influence is of great significance for the safe exploration of methane hydrate. Firstly, a thermal-hydro-mechanical bond contact model is introduced to capture the microscopic contact behavior of methane hydrate bonded granules. Secondly, the model is implemented into the distinct element method (DEM) to simulate DEM biaxial tests of MHBS for different T and σ_w. Finally, the influence of T and σ_w on the macro-mechanical properties of MHBS is discussed by analyzing the results from the DEM biaxial tests and the laboratory tests. The results show that the DEM biaxial tests incorporating the bond contact model can efficiently capture the influence of T and σ_w on macro-mechanical properties of MHBS. T and σ_w affect the mechanical properties of inter-particle methane hydrate and in turn influence the macroscopic mechanical behavior of MHBS. A dimensionless parameter L, which is calculated in the coordinates of ordinate and abscissa being dimensionless σ_w and T respectively as the minimum distance from a point of dimensionless σ_w and T to the phase equilibrium line, is advised to use for evaluating the macro-mechanical properties of MHBS with respect to different T and σ_w.