【作者】 王勇；

【导师】 周小平；

【作者基本信息】 武汉大学 ， 岩土工程， 2021， 硕士

【摘要】 开展冻融-单轴加卸载耦合作用下含裂隙岩样中微裂纹的扩展、连接及贯通破坏过程的演化研究、岩样物理力学特性及本构模型研究,对含冻土层岩土工程的安全性与稳定性具有重要意义。本文对经过冻融循环处理后的含预制裂纹的岩样,进行了单轴压缩及循环加载试验,研究了不同冻融循环次数、不同裂纹布置及不同加载条件对岩样裂纹演化扩展规律及物理力学特性的影响,并且利用DIC分析系统对岩样的应变场及位移场进行分析,构建了考虑在冻融-单轴加卸载耦合作用下裂隙岩体疲劳本构一维和三维模型。主要的研究成果有以下几个方面:(1)开展了冻融循环后不同加载情况下岩样的物理力学特性研究。(1)对含预制裂纹的红砂岩岩样进行冻融循环试验,发现:随着冻融循环次数的增加,岩样的质量、纵波波速及冻融系数呈逐渐减小的趋势。(2)对经过冻融循环处理后的岩样进行单轴压缩及循环加卸载试验,并结合已有的研究资料,对岩石的冻融损伤劣化机理及其影响因素进行了分析,发现:单轴压缩下岩样应力-应变曲线整体的变形过程基本相似,且随着冻融次数的增加,岩样的峰值强度、弹性模量、变形模量及起裂应力等力学参数均呈现逐渐减小的趋势,而峰值应变则逐渐增大。而在单轴循环加卸载下,岩样的破坏时循环加卸载次数及起裂循环加卸载次数逐渐减小,上限轴向应变最大值逐渐增加。(2)开展了岩样的裂纹演化规律研究。利用高速摄影仪捕捉岩样整个破坏过程,分析其宏观破坏过程,发现:(1)起裂模式:在裂纹倾角为30°条件下,岩桥角30°和60°的岩样,最先起裂的是翼型裂纹或反翼型裂纹;在裂纹倾角为60°条件下,反翼型裂纹最先发育。在裂纹倾角30°及60度条件下,岩桥角90°和120°的岩样最先起裂的是翼型裂纹。(2)连接类型:总结归纳了九种不同的连接类型。分析发现在裂纹倾角为30°或60°条件下,岩桥角30°和60°的岩样,主要为倾斜裂纹和反翼型裂纹连接、反平面倾斜裂纹与翼型或反翼型裂纹连接,而岩桥角90°和120°的岩样主要为翼型裂纹连接或翼型裂纹与反翼型裂纹连接。(3)破坏模式:主要为张拉型破坏及张拉-剪切混合型破坏。相较单轴压缩作用,循环加卸载作用下岩样预制裂纹的尖端产生的次生裂纹更多,反映出循环加卸载作用的累积性损伤效应。(4)利用DIC数字散斑动态应变测量分析系统,分析了岩样的位移场和应变场变化云图,发现宏观上岩样的裂纹起裂、扩展及连接过程与细观的应变、位移场演化过程具有较好的一致性。(3)通过对传统西原模型进行改进,构建了冻融-单轴加卸载耦合作用下裂隙岩体疲劳变形规律的一维和三维模型,推导了其本构方程。并利用试验数据,验证了本构模型方程的合理性。更多还原

【Abstract】 It is of great significance for the safety and stability of geotechnical engineering construction and operation in cold areas to carry out the research on the evolution of microcrack initiation,connection and through failure process,physical and mechanical properties and constitutive model of rock samples under the coupling action of freezing-thawing and uniaxial loading and unloading.In this paper,after dealing with the freezing and thawing cycle of prefabricated crack in the rock,and cyclic loading tests of uniaxial compression tests have been carried out to study the different freeze-thaw cycles,different layout and different loading conditions on the rock crack evolution of crack extension rule and the influence of the physical and mechanical properties,and using DIC analysis system for the initial strain field and displacement field is analyzed,One-dimensional and three-dimensional fatigue constitutive models of fractured rock mass under the coupling of freeze-thaw and uniaxial loading and unloading were constructed.The main research results are as follows:(1)The physical and mechanical properties of rock samples under different loading conditions after freeze-thaw cycles have been studied.(1)The freeze-thaw cycle test was carried out on the red sandstone rock sample with prefabricated cracks,and it was found that with the increase of the number of freeze-thaw cycles,the quality of the rock sample,the longitudinal wave velocity and the freeze-thaw coefficient showed a gradually decreasing trend.(2)The uniaxial compression and cyclic loading and unloading tests were carried out on the rock sample after the freeze-thaw cycle treatment.And combined with the existing research data,the mechanism of freeze-thaw damage and deterioration and its influencing factors were analyzed.It was found that the overall deformation process of the stress-strain curve of the rock sample under uniaxial compression is basically similar,and with the increase of the number of freeze-thaw cycles,under different loading methods,the mechanical parameters such as peak strength,elastic modulus,deformation modulus and crack initiation stress of rock samples show a gradual decrease trend,while the peak strain gradually increases.(2)Research on the crack evolution law of rock samples has been carried out.The whole failure process of rock samples was filmed by high-speed camera,and the macro failure process was analyzed.It was found that:(1)Crack initiation mode: Under the condition of the crack inclination angle of 30°,the rock sample with 30° and 60° rock bridge angles,airfoil crack or anti-airfoil crack is the first crack initiation mode;when the crack Angle is 60°,the anti-airfoil crack develops first.Under the condition of crack Angle of 30°and 60 °,airfoil crack is the first crack in rock samples with bridge Angle of 90° and 120°.(2)Connection types: Nine different types of connection are summarized.It is found that under the condition of 30°and 60°crack angles,the rock samples at 30°and 60°bridge angles are mainly connected with inclined crack and anti-airfoil crack,and the anti-plane inclined crack is connected with airfoil or anti-airfoil crack,while the rock samples at 90°and120°bridge angles are mainly connected with airfoil crack or anti-airfoil crack.(3)Failure mode: mainly tensile failure and tensile shear failure.Compared with uniaxial compression,there are more secondary cracks at the tip of rock samples under cyclic loading and unloading,which reflects the cumulative damage effect of cyclic loading and unloading.(4)Using the DIC digital speckle dynamic strain measurement and analysis system,the displacement field and strain field change cloud map of the rock sample are analyzed,It is found that the macroscopic process of crack initiation,development and transfixion is in good agreement with the microscopic evolution process of strain and displacement field.(3)By improving the traditional Nishihara model,One-dimensional and three-dimensional fatigue deformation models of fractured rock mass under the coupling action of freeze-thaw and uniaxial loading and unloading were constructed,and the constitutive equation is derived.The rationality of the constitutive model is verified by the experimental data.更多还原