深海能源土边界面本构模型在FLAC3D中的植入与应用

Implementation and Application of Bounding Surface Plasticity Model for Methane Hydrate Bearing Sediments via FLAC3D

摘要:

笔者团队通过引入衰减的水合物胶结强度变量，建立了基于临界状态的深海能源土（含甲烷水合物的深海沉积物）边界面本构模型，其能够描述能源土在温?压?力?化耦合效应下的力学特性。在此基础上，通过有限差分程序FLAC^3D预留的UDM程序接口，利用C++语言编程将该边界面本构关系模型植入在FLAC^3D数值软件中，并通过单元数值试验验证了嵌入程序的正确性。进一步利用植入的本构模型，针对深海能源土井壁稳定性与地基承载力问题开展数值模拟研究。结果表明开采井最大径向位移随着水合物饱和度和温压化参数L_MH的减小而增大，随着地应力水平的增大而增大。而能源土地基的破坏形式在水合物饱和度为5 %时趋向于局部剪切破坏，在水合物饱和度为30 %时，趋向于整体剪切破坏。

Abstract:

This paper developed a bounding surface plasticity model for methane hydrate bearing sediments （MHBS） by incorporating a decaying bonding strength variable. Based on the critical state， this model captured the complex mechanical properties of MHBS while considering the coupling of thermo-hydro-mechanic-chemo (THMC) conditions. Additionally， it implemented the boundary surface plasticity constitutive model is implemented into the UDM interface in FLAC^3D using a C++ compiler， and validated the accuracy of the program through the element numerical test. Based on the numerical simulation， it simulated the wellbore stability and the bearing capacity of MHBS foundation .The results show that the maximum radial displacement of the wellbore increases with the decrease of hydrate saturation and the thermo-hydro-chemical parameters （L_MH）， and increases with the increase of in-situ stress. Moreover， when the hydrate saturation is 5 %， the failure mode of MHBS foundation belongs to the local shear failure. In contrast， the soil failure mode of MHBS foundation belongs to the integral shear failure with a hydrate saturation of 30 %.