基于损伤演化的半均质砂岩本构模型研究

为了对受载岩体破坏过程的损伤演化规律进行探究,利用三轴试验仪对半均质砂岩进行三轴压缩试验,并布置声发射(AE)监测仪,对砂岩变形破坏全过程进行试验研究。分析了不同围压下砂岩三轴压缩各阶段的声发射特征,提出了基于AE事件点数的损伤变量,分别假设损伤演化方程服从韦伯分布和对数正态概率分布,建立了以AE事件点数为损伤变量的损伤演化模型,并引入修正系数对损伤变量D进行修正。结果表明围压越大,声发射活动越弱,围压能够抑制试样内部裂纹的产生和发展,增大试样强度,从而延缓其宏观破坏时间;砂岩的损伤发展主要经过4个阶段,即初始损伤阶段、损伤稳定发展、损伤加速阶段和破坏后损伤阶段。通过对韦伯分布和对数正态分布建立的声发射损伤模型进行比较,发现对数正态分布更适用于描述半均质砂岩的声发射现象。

Constitutive Models of Half-homogeneous Sandstone Based on Damage Evolution

In the aim of exploring the damage evolution of rock under load in the process of failure,the deformation and failure process of half-homogeneous sandstone are studied through triaxial compression test with acoustic emis-sion monitor.The acoustic emission characters of sandstone in different stages of triaxial compaction under different confining pressures are analyzed.As confining pressure increases,acoustic emission activity weakens,which indi-cates that confining pressure could inhibit the emergence and development of internal crack and improve the strength of sample,and consequently delay the time of macroscopic damage.Furthermore,a new damage variable and damage evolution model is proposed based on AE events by assuming that the damage evolution equation obeys Weibull distribution and lognormal distribution,and a correction coefficient is introduced to modify the damage var-iable.The damage development of sandstone is mainly divided into four stages:the stage of initial damage,the stage of steady development,the stage of accelerative development and the stage of damage after failure.By compa-ring the two acoustic emission damage models,we found that logarithmic normal distribution is more suitable for de-scribing acoustic emission phenomenon of half-homogeneous sandstone.