【作者】 王琛；

【导师】 刘浩吾；

【作者基本信息】 四川大学 ， 岩土工程， 2003， 博士

【摘要】 三峡水库蓄水势必严重影响库岸的地质环境，有可能导致一批滑坡体复活乃至失稳破坏，生成库水诱发型滑坡，对三峡工程本身以及库区移民的安全都会造成巨大的威胁。 高面板堆石坝中堆石体的流变变形直接关系到大坝安全，近年在国内外受到关注，天生桥工程中的相关现象凸显了这一问题的意义。 为此，本文围绕岩土材料的流变特性和滑坡的变形稳定分析，对滑动带土、堆石料的流变试验、流变机制、流变理论和长江三峡库区泄滩古滑坡的非线性有限元应力变形稳定分析进行了研究。 (1)本文基于对岩土流变学的发展及其研究现状的分析，指出了当前理论中存在的一些问题。提出了适合粘弹塑性流变模型的积分型流变方程，并将之对比于4种基本微分模型(即马克斯威尔模型M、宾哈姆模型B、开尔文模型K和村山模型C)的流变方程，结果证明该积分型流变模型不仅适用于粘弹性流变模型，且适用于粘弹塑性流变模型。根据四种基本流变模型的串联形式(K-C-M-B)，首次提出了积分型的普遍流变方程，当该积分型流变方程的蠕变核为负指数函数形式时，给出了相应的微分型流变方程，并指正了流变方程研究现有成果中的一些差误。从数学上证明了积分型和微分型流变方程在一定程度上可以互换和统一。这些成果推动了流变理论的新发展。 (2)将应变式三轴剪切仪改装成为应力式三轴流变剪切仪，用以完成了三峡库区泄滩滑坡滑动带土以及堆石料的流变试验。在将近一年时间的试验中，测 摘要试和数据采集稳定可靠，所采用的土流变试验仪器和测试方法在现阶段具有代表性。 (3)在土的流变机制和流变模型方面，根据试验数据给出了泄滩滑坡滑动带土的Singh一Mitchell流变模型和Mesri流变模型及相应参数。尽管该两模型与试验数据的变化趋势尚属接近，但它们在等速蠕变阶段应变速率明显比试验值偏大，表明该两模型对滑动带土流变规律的拟合能力欠佳。为此，本文提出了分段拟合的思想和修正Mesri应力一应变一时间关系。这一新模型从机理上反映了岩土流变过程表现为衰减蠕变、等速蠕变、稳定蠕变或急剧破坏三阶段型的基本定性规律，实现了对Mesri模型的拓广，原Mesri模型实质上是修正Mesri模型的一个特例。据此，通过对蠕变试验数据的分段拟合，给出了泄滩滑动带土的修正Mesri应力一应变一时间关系及其参数。由Mesri模型和新模型与试验数据的对比，表明新模型的模拟能力和可靠性得到明显提高。对参数的分析表明，该修正Mesri模型亦可模拟蠕变的加速蠕变阶段。 (4)基于三峡库区典型滑坡滑动带土试验的应力一应变一时间关系曲线的规律性，首次提出了考虑时间效应的邓肯一张双曲E一刀模型，给出了切线弹性模量和切线泊松比与时间的关系式。该模型含有12个基本参数，可由常规三轴排水试验和三轴排水蠕变试验得到，其中参数凡·肚G、D与时间有关，并给出了它们和时间的关系式。这样，将时间因素引入到了土的本构模型之中，将本构模型和材料自身的流变特性结合了起来。由于该模型所需试验简单，且其计算便于在常规邓肯一张E一刀模型程序上改进实现，故显得简单实用，优于弹粘塑性模型。 (5)经试验数据拟合分析，堆石的蠕变规律随时间呈双曲线型和指数型衰减变化，与衰减较快的指数型函数拟合更好。其瞬时变形与最终蠕应变都与所施加的应力大小有关，各蠕变参数与各应力变量基本呈良好的线性关系。 (6)对三峡库区的典型古滑坡(泄滩滑坡)的变形场与稳定性，采用邓肯-张双曲E一刀模型进行了三维非线性有限元数值模拟。进行了该滑坡滑动带土的常规土工测试和三轴剪切试验，得到了该滑动带土的基本性能指标和邓肯-张E一刀模型8参数。计算结果显示该滑坡在天然状况和初期蓄水情况下都处于稳定状态，当满库蓄水和水位骤降时，滑坡体内二级台地部位将出现局部失稳破坏。计算成果规律性良好，变形与应力分布趋势合理，量级可信，可供三 四川人学博{一学位沦文峡水库地质灾害防治工作参考应用。 (7)在上述滑坡数值模拟分析中，进行了计算工况(4种，含控制性工况)、渗透压力(包括库水骤降的渗透体积力)、单元配置(包括非线性单元以及滑动带双侧的接触元)、网格剖分诸方面较全面的分析研究。滑动带厚度的(0.7一2.7m)剖分层数尽管对应力场影响很小，但对位移场有相当影响，剖分不足会因蓄水产生的位移增量为计算一误差所掩盖而导致误判。对滑坡进行这样比较深入系统的空间非线性有限元数值模拟，罕有先例，丰富了滑坡预测预报的手段，有利于滑坡评估技术的发展。 综_匕本工作中试验研究、理论分析、数值模拟多种手段密切结合，研究与三峡库区地质灾害防治的需要密切结合。试验和计算工作量大。研究成果的新特点是，提出了积分型和微分型普遍流变方程表达式，据此指正了现有成果中的一些差误;提出了能体现流变发展过程阶段性的修正Mesri模型，其模拟能力显著提高;提出了考虑时间效应的邓肯一张更多还原

【Abstract】 Geological environment will be affected seriously by water impoundment of the Three Gorges reservoir. Some old landslides located on the bank of the reservoir may be revived and even losing stability, which is harmful to the Three Gorges engineering and people.As far as concrete face rockfill dam(CFRD) is concerned, its security is related with the rheological deformations of rockfill structure, which has been showed by correlative phenomenon of Tianshengqiao CFRD dam. This problem has attracted many workers in this field.So this paper is devoted to the rheological characters of geotechnical materials and numerical analysis of deformation and stability of landslide, including rheological tests, rehological mechanisms, and rheologic theory of sliding zone soils and rockfill as well as the analysis of deformation and stability of Xietan landslide in the Three Gorges with nonlinear finite element method(FEM).(1) Based on general review on the development of geotechnical rheology, especially integral model(IM) and differential model(DM), some questions of rheological model(RM) have been pointed out. An integral type of rheologicalIVequation(ITRE) for linear visco-elastoplastic RM is presented. Through comparing it with 4 kinds of basic DM such as Maxwell model, Bingham model, Kelvin model and Cunshan model, it is proved that such ITRE suits to not only viscoelastic RM but also visco-elastoplastical RM. According to the series type of 4 kinds of basic RM, a general ITRE is presented. When creep nucleus in the ITRE is a negative exponential function, corresponding general DM can be obtained and some mistakes in current paper have been pointed out. It has been proven that the IM and DM can be interchanged not only for the visco-elastic RM but also for the visco-elastic plastic RM. These results promote the new development of rheological theory.(2) A stress-control type of triaxial rheological compression apparatus has been refitted on a strain-control type of triaxial compression apparatus, and the creep tests of sliding zone soils and rockfill have been performed with it. The data acquisition of test apparatus is reliable.(3) For the rheologic mechanism and model of the sliding zone soils ate Xietan landslide, a Singh-Mitchell stress-strain-time model and a Mesri stress-strain-time model, as well as their parameters, are presented according to the test data. In spite of the fact that these models match the basic trend of the test data, the strain rate of the models in equal-speed creep phase is larger than that of test curves obviously, which shows that the abilities of simulation of rheological characters of sliding zone soils with Singh-Mitchell model and Mesri model are not very good. So idea of subsection simulation to creep process and a modified Mesri stress-strain-time model is present. New model can show the basic law of attenuation, equal-speed and stability phases of the creep. It is a generalized Mesri stress-strain-time behavior. A modified Mesri stress-strain-time model and its parameters of sliding zone soils in Xietan landslide have been given through subsection simulation of attenuation, equal-speed and stability phases of the creep curves. It has been shown that the simulation capability of the new model has been enhanced significantly. Furthermore, it can also simulate the accelerate creep phase.(4) Base on the triaxial creep tests a Duncan-Chang E ~μ/ model concerned with time effects is formulated to characterize the stress-strain-time behavior of slidingzone soils, whose equations of tangent elastic module and tangent Poisson’s ratio with time effects are given. 12 parameters are in the newly-developed model in which k, Rf, Gand D are the functions of time. All parameters can be obtainedthrough triaxial creep tests and normal triaxial compression tests. So the time factor is involved into constitutive model of soil material, which connects the constitutive model with rheological characters of the material. For the new model, its parameter tests are not diffic更多还原