泥岩渗流-应力耦合蠕变损伤模型研究(Ⅰ)：理论模型

Study of hydro-mechanical-damage coupled creep constitutive model of mudstone,Part Ⅰ:Theoretical model

在室内和现场试验的基础上,根据泥岩的非线性蠕变变形特点,构造了基于摩尔-库仑准则的蠕变势,建立了泥岩非线性蠕变损伤本构模型及其损伤演化方程;对泥岩裂隙自愈合机制进行了探讨,得到围压、孔隙水和饱水时间是影响裂隙愈合的主要因素,通过引入愈合应力和水化学愈合因子的概念,建立了泥岩渗透性自愈合模型。研究结果表明,泥岩非线性蠕变是其内部结构损伤在蠕变过程中的综合表现,泥岩的蠕变速率不仅与应力水平、时间相关,而且还与累积蠕变变形密切相关,提出的模型能较真实反映泥岩蠕变变形过程、损伤演化、渗透性演化和裂隙自愈合,且材料常数较少,便于从实验数据中获得。文中涉及到的数值算法、程序实现、模型参数的确定以及工程应用将在本文的Ⅱ部分给出。

Based on the laboratory creep experiments and in-situ tests of mudstone,a nonlinear creep constitutive model with the Mohr-Coulomb creep potential considering hydro-mechanical coupling is put forward by analysis of creep deformation mechanisms of clay;and the damage evolution equation is set up by constructing the relation between creep damage and creep strain.A fully coupled hydro-mechanical model of mudstone is established to describe the evolution of porosity and permeability with strain and damage.The self-healing mechanism of mudstone fractures is investigated,which is effected mainly by the confining pressure,pore water,time for saturated state and so on.A permeability healing model is established by introducing the conceptions of healing stress and hydro-chemical factor.The results show that the creep strain rate of mudstone is not only related to time and stress,but also to the cumulative creep strain.The creep damage of mudstone is caused by the initiation and propagation of new fractures,which is the comprehensive expression of the coupling between deformation and time effect.The presented creep damage model can well describe the creep process of attenuation phase,stabilization phase and the speedup phase and the damage process with less material parameters.The numerical algorithm,numerical implementation and further application of the model are provided in Part Ⅱ of this paper series.