粉砂质泥岩峰前、峰后应力松弛特性试验研究

发布时间：2018-01-16 00:03

本文关键词：粉砂质泥岩峰前、峰后应力松弛特性试验研究　出处：《岩石力学与工程学报》2016年S1期 　论文类型：期刊论文

【摘要】：采用分级加载方法,对三峡地区巴东组粉砂质泥岩开展峰前、峰后三轴压缩应力松弛试验。依据试验结果,分析峰前弹性段、屈服段,峰后应变软化段、残余强度段岩石应力松弛量、应力松弛度、松弛稳定时间以及应力松弛速率的变化规律,研究峰前、峰后不同阶段岩石应力松弛特征的差异。引入损伤变量对三参量广义Kelvin模型进行改进,建立岩石的非线性应力松弛损伤模型。应用Levenberg-Marquardt算法,辨识得出岩石的应力松弛损伤模型参数。基于辨识结果,分析峰后破裂对岩石应力松弛模型参数的影响作用,研究峰前、峰后不同阶段岩石应力松弛模型参数的变化规律。在试验研究成果的基础上,总结得出峰前、峰后岩石不同的应力松弛机制。研究结果表明:(1)峰前、峰后各阶段中,峰后应变软化段试样的应力松弛量大,应力损失程度高,松弛稳定时间长,应力松弛速率快,工程实践中应尽可能避免使岩石处于峰后应变软化段。(2)峰后各级应变水平试样的G1,G2,H1参数值为峰前0.20%应变水平相应参数值的1%~53%,峰后岩石的应力松弛模型参数值急剧降低。(3)峰后形成的宏观破裂对试样的黏弹性力学特性影响最大,黏性力学特性其次,而对试样的瞬时弹性力学特性影响最小。(4)峰后应变软化段试样的G1,H1模型参数值大幅降低,峰前屈服段试样的G2模型参数值大幅降低。(5)峰前岩石的应力松弛主要是由于岩石内部微裂隙的产生、扩展等原因而引起的,峰后岩石的应力松弛主要是由于岩石中宏观裂纹的产生、扩展以及贯通等原因而引起的。峰前、峰后岩石的应力松弛机制不同。
[Abstract]:The stress relaxation tests on the sandy mudstone of Badong formation in the three Gorges region were carried out before and after the peak under triaxial compression stress relaxation test. According to the test results, the elastic section, yield section and strain softening section after peak were analyzed. The variation of stress relaxation quantity, stress relaxation degree, relaxation stability time and stress relaxation rate in residual strength segment are studied. The difference of stress relaxation characteristics in different stages after the peak. The damage variable is introduced to improve the three-parameter generalized Kelvin model. The nonlinear stress relaxation damage model of rock is established. The parameters of stress relaxation damage model of rock are identified by using Levenberg-Marquardt algorithm. The influence of post-peak fracture on the parameters of rock stress relaxation model is analyzed, and the variation law of rock stress relaxation model parameters in different stages before and after peak is studied. Based on the experimental results, the pre-peak stress relaxation model parameters are summarized. The results show that the stress relaxation amount is large, the stress loss is high and the relaxation stability time is long in the post-peak strain softening stage before and after the peak. The stress relaxation rate is fast. In engineering practice, it is necessary to avoid making the rock in the post-peak strain softening section. The parameter value of H1 is 1% of the corresponding parameter value of 0.20% strain level before the peak. The stress relaxation model parameters of post-peak rock decreased sharply. The macroscopic fracture formed after the peak has the greatest influence on the viscoelastic properties of the specimen, followed by the viscosity mechanical properties. However, the G1H1 model parameters of the specimens at the post-peak strain softening stage have the least effect on the instantaneous elastic mechanical properties of the specimens. The stress relaxation of pre-peak rock is mainly caused by the formation and expansion of microcracks in the rock. The stress relaxation of rock after peak is mainly caused by the occurrence, propagation and penetration of macroscopic cracks in rock. The stress relaxation mechanism of pre-peak and post-peak rocks is different.
【作者单位】：华北水利水电大学资源与环境学院;
【基金】：“十三五”国家科技支撑计划项目(2015BAB07B08) 国家自然科学基金资助项目(51309100) 河南省科技创新人才计划(154100510006)~~
【分类号】：TV223
【正文快照】：

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