砂质泥岩卸荷流变力学特性研究
发布时间：2018-12-07 18:44
【摘要】：软岩具有比硬岩更加复杂的力学特性,其作为工程岩体时往往表现出应变软化、流变及非线性大变形等工程力学特性,是影响工程长期稳定性的关键因素,因此,深入开展软岩力学特性方面的研究具有重要意义。本文选取软岩隧洞砂质泥岩为研究对象,通过室内试验对其力学特性进行了研究,主要的研究内容如下： 1)采用RMT-150C岩石力学试验系统进行砂质泥岩三轴压缩及卸荷试验,研究了不同应力路径下岩石的强度、变形以及破坏特征,获得了压缩及卸荷应力路径下岩石的基本力学参数。 2)针对三轴压缩及卸荷试验中无法根据应力-应变曲线直接确定砂质泥岩试样峰值强度这一问题,将半对数法引入到试验数据分析中,利用1g(σ1-σ3)～ε,关系曲线和σ3～1gε1关系曲线较方便的确定了岩样的峰值强度值,并基于应力增量、应变增量与应力之间的关系曲线|△ε1/△(σ1-σ3)|～(σ1-σ3)对取值方法的合理性进行了验证。 3)采用RLW-2000微机控制岩石三轴蠕变试验机对砂质泥岩进行恒轴压卸围压和加轴压卸围压应力路径下的分级卸荷流变试验,对比分析了两种应力路径下砂质泥岩试样轴向及侧向变形随时间的变化规律;探讨了两种应力路径下加速流变阶段砂质泥岩试样流变变形特征和速率发展规律;利用等时曲线法确定了不同卸荷初始围压下砂质泥岩试样的长期强度,并引入强度比概念对比分析两种应力路径下长期强度与破坏应力间的比例关系;分析了不同应力路径下砂质泥岩试样的破坏特征及其随卸荷初始围压变化的发展规律。 4)基于卸荷流变试验全过程曲线,采用西原模型对应力水平小于σs(岩石流变破坏的前一级应力水平)条件下砂质泥岩的流变特征进行了描述,利用Levenb erg-Marquardt优化算法对模型中各流变参数进行了优化辨识。 5)以西原模型为基础,引入非线性黏塑性流变元件建立了一个新的非线性黏弹塑性流变模型,使其能够较好的描述破坏围压下砂质泥岩流变全过程曲线的非线性加速流变阶段,验证分析表明该模型计算的应力-应变曲线与试验曲线比较吻合,表明所建立的非线性黏弹塑性流变模型是合理的。 6)对新建立的非线性黏弹塑性流变本构模型在FLAC3D程序中予以数值实现并将其运用于某水电站引水隧洞的长期稳定性计算分析,研究成果可为隧洞围岩的长期稳定性研究和隧洞长期运行的安全性分析提供一定的参考价值。
[Abstract]:Soft rock has more complex mechanical properties than hard rock. As engineering rock mass, soft rock often shows such engineering mechanical properties as strain softening, rheology and nonlinear large deformation, which are the key factors that affect the long-term stability of engineering. It is of great significance to further study the mechanical properties of soft rock. In this paper, sand mudstone of soft rock tunnel is chosen as the research object, and its mechanical properties are studied through laboratory tests. The main research contents are as follows: 1) the RMT-150C rock mechanics test system is used to test the triaxial compression and unloading of sandy mudstone, and the strength, deformation and failure characteristics of the rock under different stress paths are studied. The basic mechanical parameters of rock under compression and unloading stress paths are obtained. 2) in order to solve the problem that the peak strength of sandy mudstone specimen can not be determined directly by stress-strain curve in triaxial compression and unloading test, the semi-logarithmic method is introduced into the analysis of test data, and 1g (蟽 1- 蟽 3) 蔚 is used. The peak strength of rock samples is easily determined by the relationship curve and 蟽 3 + 1g 蔚 1 curve, and based on the stress increment, The relationship between strain increment and stress is verified by the curve of 蔚 _ 1 / (蟽 _ 1- 蟽 _ 3) ~ (蟽 _ 1- 蟽 _ 3) ~ (蟽 _ 1- 蟽 _ 3). 3) RLW-2000 microcomputer controlled triaxial creep testing machine is used to test sand mudstone under constant axial pressure unloading confining pressure and axial compression unloading confining pressure path. The variation of axial and lateral deformation of sandy mudstone samples with time under two stress paths is comparatively analyzed. The rheological deformation characteristics and rate development of sandy mudstone samples at accelerated rheological stage under two stress paths are discussed. The long-term strength of sandy mudstone samples under different initial confining pressures is determined by isochronous curve method, and the relationship between long-term strength and failure stress under two stress paths is analyzed by introducing the concept of strength ratio. The failure characteristics of sandy mudstone samples under different stress paths and the development law of the change of initial confining pressure with unloading are analyzed. 4) based on the whole process curve of unloading rheological test, the rheological characteristics of sandy mudstone with stress level less than 蟽 s (the first stress level of rock rheological failure) are described by using the Xiyuan model. The rheological parameters of the model are identified by Levenb erg-Marquardt optimization algorithm. 5) based on the original model, a new nonlinear viscoelastic-plastic rheological model is established by introducing nonlinear viscoplastic rheological elements. It can describe the nonlinear accelerated rheological phase of the whole rheological process curve of sandy mudstone under the failure confining pressure. The verification and analysis show that the stress-strain curve calculated by this model is in good agreement with the experimental curve. It is shown that the nonlinear viscoelastic-plastic rheological model is reasonable. 6) the new nonlinear viscoelastic-plastic constitutive model is numerically realized in FLAC3D program and applied to the long-term stability analysis of the diversion tunnel of a hydropower station. The results can provide some reference value for the study of the long-term stability of the surrounding rock and the safety analysis of the tunnel in the long run.
【学位授予单位】：三峡大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU45
本文编号：2367654
[Abstract]:Soft rock has more complex mechanical properties than hard rock. As engineering rock mass, soft rock often shows such engineering mechanical properties as strain softening, rheology and nonlinear large deformation, which are the key factors that affect the long-term stability of engineering. It is of great significance to further study the mechanical properties of soft rock. In this paper, sand mudstone of soft rock tunnel is chosen as the research object, and its mechanical properties are studied through laboratory tests. The main research contents are as follows: 1) the RMT-150C rock mechanics test system is used to test the triaxial compression and unloading of sandy mudstone, and the strength, deformation and failure characteristics of the rock under different stress paths are studied. The basic mechanical parameters of rock under compression and unloading stress paths are obtained. 2) in order to solve the problem that the peak strength of sandy mudstone specimen can not be determined directly by stress-strain curve in triaxial compression and unloading test, the semi-logarithmic method is introduced into the analysis of test data, and 1g (蟽 1- 蟽 3) 蔚 is used. The peak strength of rock samples is easily determined by the relationship curve and 蟽 3 + 1g 蔚 1 curve, and based on the stress increment, The relationship between strain increment and stress is verified by the curve of 蔚 _ 1 / (蟽 _ 1- 蟽 _ 3) ~ (蟽 _ 1- 蟽 _ 3) ~ (蟽 _ 1- 蟽 _ 3). 3) RLW-2000 microcomputer controlled triaxial creep testing machine is used to test sand mudstone under constant axial pressure unloading confining pressure and axial compression unloading confining pressure path. The variation of axial and lateral deformation of sandy mudstone samples with time under two stress paths is comparatively analyzed. The rheological deformation characteristics and rate development of sandy mudstone samples at accelerated rheological stage under two stress paths are discussed. The long-term strength of sandy mudstone samples under different initial confining pressures is determined by isochronous curve method, and the relationship between long-term strength and failure stress under two stress paths is analyzed by introducing the concept of strength ratio. The failure characteristics of sandy mudstone samples under different stress paths and the development law of the change of initial confining pressure with unloading are analyzed. 4) based on the whole process curve of unloading rheological test, the rheological characteristics of sandy mudstone with stress level less than 蟽 s (the first stress level of rock rheological failure) are described by using the Xiyuan model. The rheological parameters of the model are identified by Levenb erg-Marquardt optimization algorithm. 5) based on the original model, a new nonlinear viscoelastic-plastic rheological model is established by introducing nonlinear viscoplastic rheological elements. It can describe the nonlinear accelerated rheological phase of the whole rheological process curve of sandy mudstone under the failure confining pressure. The verification and analysis show that the stress-strain curve calculated by this model is in good agreement with the experimental curve. It is shown that the nonlinear viscoelastic-plastic rheological model is reasonable. 6) the new nonlinear viscoelastic-plastic constitutive model is numerically realized in FLAC3D program and applied to the long-term stability analysis of the diversion tunnel of a hydropower station. The results can provide some reference value for the study of the long-term stability of the surrounding rock and the safety analysis of the tunnel in the long run.
【学位授予单位】：三峡大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU45
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