【作者】 黄明；

【导师】 刘新荣；

【作者基本信息】 重庆大学 ， 土木工程， 2010， 博士

【摘要】 流变是岩石材料的重要力学特征,许多岩土工程问题都与岩石的流变特性有密切关系,岩石流变现象给实际工程带来的影响已引起国内外学者的广泛关注。目前,在描述和处理岩石的时间效应及其流变属性方面取得了较大的进展,但针对含水状态下岩石流变特性的研究成果并不多见,而实际中却存在许多长期受地下水影响的岩石工程问题,因此正确了解并掌握岩石(特别是软岩)在地下水环境中的流变特性具有重要的现实意义。本文在前人研究的基础上,采用试验研究、理论分析和数值模拟相结合的研究方法,对含水泥质粉砂岩蠕变特性及其在软岩隧道稳定性分析中的应用等进行了较为系统和深入的研究。论文的主要研究内容和成果如下:①从桃树垭隧道现场采集新鲜的T2b2泥质粉砂岩,进行了不同含水状态下的力学特性试验,获得了四种含水率情况下的应力—应变关系曲线。基于T2b2泥质粉砂岩单轴蠕变试验,获得了不同含水状态下五级荷载的单轴应变-时间曲线,分析得到了蠕变随不同应力水平及不同含水状态的变化规律。②基于岩石非线性流变力学基本理论,在T2b2泥质粉砂岩应力—应变关系相关研究的基础上,提出了一种修正的Kelvin模型,并建立了该模型一维情况下的流变本构方程,分析表明修正Kelvin体在描述岩石流变特性时具有更好的适应性。③针对T2b2泥质粉砂岩蠕变模型的辨识问题,首先提出了一种可用阶跃函数表示的开关元件,并将开关元件和牛顿体并联建立了修正牛顿体,然后将修正牛顿体、修正Kelvin体、Hoek体串联得到可描述岩石非线性蠕变特性的MBurgers模型。基于非线性最小二乘理论,结合T2b2泥质粉砂岩的单轴蠕变试验结果,对MBurgers模型参数进行了回归反演,将反演得到的参数代入模型进行计算,得到的理论曲线与试验曲线相比吻合较好,表明MBurgers模型能较好地描述T2b2泥质粉砂岩的单轴蠕变特性。④针对含水率变化对泥质粉砂岩蠕变特性的影响问题,定义了岩石的含水率损伤概念,引入瞬间弹性损伤D (w)、长期蠕变损伤D′( w)两个损伤变量且推导了损伤演化公式,建立了考虑含水损伤效应的MBurgers蠕变方程,并针对含水率恒定和含水率随时间变化两种情况进行了分析与计算。⑤通过对考虑含水损伤Mburgers模型进行退化假定分析,得到了几种常见的流变模型。对不考虑参数α影响退化得到的可考虑含水损伤KBurgers模型分别进行了常泊松比和常体积模量假定下的三维形式推广,并研究得到了不同建模思路下模型参数之间的换算关系。通过对常体积模量假定下模型参数随含水率变化的损伤演化规律进行了分析,获得了常体积模量假定下的瞬间弹性损伤和长期蠕变损伤演化方程。将Mohr-Coulomb元件与KBurgers模型串联,并假定粘弹和粘塑应变率分量变形协调,建立了能模拟粘弹塑性偏量特性和弹塑性体积行为的KBurgers-MC模型,新模型除具有瞬间弹性变形、衰减蠕变、等速蠕变和含水损伤的性质外,还可以描述塑性变化引起的不稳定蠕变特性。⑥基于有限差分理论,推导得到了KBurgers-MC模型的有限差分格式,并结合FLAC3D软件良好的二次开发环境进行了模型的程序二次开发研究,获得了KBurgers-MC模型的计算机应用程序,并在此基础上,结合桃树垭隧道工程,对施工过程中不同含水状态下的围岩稳定性和支护结构的变形及受力性状进行了模拟分析,探讨了不同含水状态下隧道二次衬砌最佳施作时机,并进一步分析阐明了桃树垭隧道大变形灾害的发生机理。更多还原

【Abstract】 Rheology is the most important mechanical characteristics of rock material, and many geotechnical-engineering problems closely relates to the rheological properties of rocks. As the phenomenon of rock rheology is widespread, people have begun to realize the impact of rheological behavior to the projects. Although people have made a great and important progress in describing and processing time effect and rheology of materials, however, there are still many problems need to solve. Additionally, water is a very important factor in affecting the rheological properties of tunnel surrounding rock. During the tunnel excavation, disturbance because of excavation will cause physical breakdown of original rock and increase the exposed area of rock. As a result, the seepage path of rock will increase and surrounding rock will become weaker because of the contacts with ground water. With the time increasing, the phenomenon that surrounding rock may become unstable, which may cause the occurrence of major engineering accident. Therefore, it has very important significance in practice to understand and master the rheology of rocks (especially the soft rock) in the groundwater environment.In view of this, researches carried out in this paper will use a combination method including testing research, theoretical analysis and numerical simulation. According to uniaxial creep tests of T2b2 siltite under different moisture conditions and the non-linear rheology theory and damage theory, the creep properties of siltite under different moisture conditions is analyzed, nonlinear creep model of siltite with considering water damage is present and also programmed in computer. Based on the theoretical study results, researches on the effectiveness of soft rock tunnel dynamic construction mechanics under different moisture conditions are carried out. The main contents and results of research in this paper are as follows:①According to the mechanics and deformation tests of the T2b2 siltite in different moisture conditions, which is collected freshly from the Tao Shu Ya tunnel site, the stress-strain curves under 4 kinds of moisture conditions are obtained. Based on the creep tests of T2b2 siltite under different moisture conditions, uniaxial strain-time curves in five load levels are obtained under different moisture conditions, and the variation law of creep curves with the change of stress and moisture content is analyzed.②According to the basic nonlinear rheology theory of rock and the relevant researches on stress-strain relationship of T2b2 siltite, a revised Kelvin model is put forward, and the rheological constructive equation of it is present. Through comparing the characteristics of the revised K model and common K model, it is indicated that the revised K model has many special characteristics and has a better adaptability in describing the rheological properties of rocks.③In response to the problems of creep model identification of T2b2 siltite, a swath model, which can be expressed as a pulse function, is put forward firstly, and by installing the swath model with N model in parallel, a revised N model is established too. Through connecting revised N model with revised K model and H model in the form of series, an MBurgers model, which can well describe the nonlinear creep property of rock, is established. According to the nonlinear least squares theory and uniaxial creep test results of T2b2 siltite, the parameters of MBurgers model are obtained by inversion caculation. By substituting the parameters obtained on behalf of the inversion into the model and calculating the theoretical results, it is shows that theoretical curve and test curve is well anastomotic, which indicates that MBurgers model can well describe the creep of T2b2 siltite.④In response to the problems of creep properties of siltite effected by the changes of moisture content, the concept water damage and two damage variable instantaneous elastic damage D (w), creep damage D′( w) are introduced. Through deriving damage evolution equation, MBurgers model with water damage effect is established, what’s more, the characteristics of it are analyzed in the case that moisture content is invariable or variable over time.⑤With analyzing the degradation of MBurgers with water damage effect in different assumptions, several other rheological models are established. In case of not considering the parameterαeffect but consider the water damage effect, a new creep model KBurgers model can be established, and it can also be extended to three-dimensional format in the assumptions of invariable Poisson’ration and invariable bulk modulus. In addition, the relationships among the model parameters under different modeling ideals are studies too. Through analyzing the damage evolution of model parameters with moisture content changing under the assumption of invariable bulk modulus, the damage evolution equations of instantaneous elastic damage and creep damage are obtained. By connecting the M-C model with KBurgers model in serial and assuming the strain rate components of viscoelastic and viscoplastic are compatible, a new model KBurgers-MC model which can describe the visco-elastic-plastic characteristics of deviator and elastic-plastic characteristics of bulk is established. Furthermore, the new model not only has the characteristics of instantaneous elastic, attenuation creep, steady creep and water damage, but also has the characteristics of plastic and unstable creep.⑥Based on the difference theory and good redevelopment platform of the software FLAC3D, the finite difference scheme of KBurgers-MC is present, and the computer program of it is obtained too. Combining the computer program and the actual construction process of Tao Shu Ya tunnel, deformation and stress of surrounding rock and supports are simulated by FLAC3D under different times and different moisture conditions. Finally, stability of surrounding rock under different times and different moisture conditions is judged, the best construction time for secondary lining under different moisture conditions is suggested, and the mechanism of larger deformation occurrence in Tao Shu Ya tunnel is also further expound.更多还原