水合物沉积物的力学本构模型及参数离散元计算

A Mechanical Constitutive Model for Hydrate-Bearing Sediments and Calculation of Material Parameters With the Discrete Element Method

为有效描述水合物沉积物在不同水合物饱和度与围压情况下的力学行为,该文基于广义Hooke(胡克)定律建立了水合物沉积物的应力-应变关系方程和弹性模量弱化方程;基于三轴压缩试验确定了水合物沉积物的软化系数和软化指数,基于颗粒流程序(PFC^(3D))开发了水合物沉积物初始弹性模量的离散元算法(DEM).利用建立的应力-应变关系方程、弹性模量弱化方程和初始弹性模量DEM,数值模拟了水合物沉积物在6种不同水合物饱和度与围压情况下的力学行为.数值模拟结果与三轴压缩试验结果的对比表明,建立的应力-应变关系方程、弹性模量弱化方程和初始弹性模量DEM,能有效预测水合物沉积物的力学行为,可为水合物井筒设计与安全开采提供理论基础和计算方法.

To soundly describe the mechanical behaviors of hydrate-bearing sediments in the cases of different saturation levels of hydrate and various confining pressures, the stress-strain relation equations and elastic modulus weak-form equations for hydrate-bearing sediments were developed based on the generalized Hooke’s law. The softening coefficient and softening exponent of the hydrate-bearing sediments were determined according to the triaxial compression test results. A discrete element method (DEM) to calculate the initial elastic moduli of hydrate-bearing sediments was proposed based on the 3D particle flow code (PFC3D). The mechanical behaviors of hydrate-bearing sediments under 6 various conditions related to saturation levels of hydrate and confining pressures, were numerically simulated with the stress-strain relation equations, elastic modulus softening equations and the DEM together. Numerical results show that, the proposed stress-strain relation equations, elastic modulus softening equations and the DEM can effectively predict the mechanical behaviors of hydrate-bearing sediments under various saturation levels of hydrate and confining pressures. The work gives a theoretical basis and a computational method for the investigations on the mechanical behaviors of hydrate boreholes and the safe exploitation of hydrate.