库区边坡失稳可能对下游水库及大坝结构的安全带来严重威胁。引起边坡失稳破坏的原因可分为边坡内部结构性因素和外界环境诱发因素。当边坡下卧基岩中包含软弱结构面时，边坡更容易受外界环境因素的影响而沿结构面方向发生顺坡向变形乃至失稳破坏，这些外界环境因素包括库区水位的涨落，降雨入渗影响和区域地震等。随着计算机模拟技术的发展，构建边坡的数值仿真模型并分析不同的外界环境因子对其稳定性的影响已有较多研究结果见诸文献，但对于下卧基岩内包含近水平软弱夹层的坡体时效变形规律的研究仍较少。尤其对于库区边坡，其蠕滑变形幅值以及稳定阈值受库水位升降的影响规律值得深入分析。本论文以某典型库区边坡为例，关注其下卧岩层内的近水平软弱夹层的蠕滑变形规律及对场地稳定性的影响评价，开展了系列数值模拟研究，主要内容包括：1）构建岩土粘弹塑性材料模型。从一维西原粘弹塑性蠕变模型出发，构建一类简化型式的三维粘弹塑性材料力学模型基于ABAQUS程序的二次开发接口进行程序实现，并基于数值算例对多种应力路径下的计算结果进行分析和验证；分析该模型的数值计算稳定性条件，以保证计算结果的收敛性；讨论构建的粘弹塑性材料模型的局限性。2）构建某典型库区边坡准三维有限元计算模型。基于相关工程勘测资料，选取典型地质剖面，构建场地准三维有限元模型；通过试算分析库区蓄水过程边坡的蠕滑响应，分析不同试算工况下边坡内部力学状态的差异，对软弱夹层材料的相关粘弹塑性参数进行标定。3）对比分析场地稳定性影响因素以及工程措施。分析由于库水位涨落引起边坡浸润线的升降对场地蠕滑变形发展的影响规律；讨论两种工程处理措施，即削坡卸荷和坡脚堆载，对控制场地蠕滑变形发展的效果。本课题的仿真研究结果表明：应用构建的三维粘弹塑性模型可以表征边坡蠕滑变位模式，且模拟到的边坡变形发展趋势与实际监测结果趋势较为吻合，两类不同的工程处理措施在控制场地蠕滑变形效果上存在显著差异。在定量描述上，尚需考虑发展模型的应力非线性，并引入场地三维效应。研究结果可以为边坡处理措施的选取提供参考。
The instability of reservoir slope may pose a serious threat to the safety of downstream reservoirs and dam structures. The causes of slope failure can be divided into internal structural factors of slope and inducing factors of external environment. When there is soft structure surface in the lower bedrock, the slope is more vulnerable to the influence of the external environmental factors, and the slope deformation and even instability will occur along the direction of the structural surface. These external environmental factors include the fluctuation of the water level of the reservoir area, the influence of rainfall infiltration and the regional earthquake. With the development of computer simulation technology, the construction of the numerical simulation model of slope and the analysis of the influence of different environmental factors on its stability have been found in many literature, but the research on the law of aging deformation of the slope which contains the near horizontal weak interlayer in the lower bedrock is still less. Especially for the reservoir slope, the creep deformation amplitude and stability threshold are affected by the fluctuation of reservoir water level.This paper takes a typical reservoir slope as an example, pays attention to the creep deformation law of the near horizontal weak interlayer and the evaluation of the effect on the stability of the ground, and carry out a series of numerical simulation studies. The main contents are as follows:1） Construct the viscoelastoplastic material model of rock and soil. Based on the original one-dimensional NASHIHARA‘s model, a simplified type of three-dimensional viscoelastic material mechanical model is constructed using the user development interface of the ABAQUS. Based on the numerical model, the calculation results of various stress paths are analyzed and verified, and the numerical calculation stability of the model is analyzed, in order to ensure the convergence of the calculation results; The limitations of the viscoelastoplastic material model are discussed.2） Build a quasi-three-dimensional finite element model of slope in a typical reservoir area. Based on the related engineering survey data, selecting a typical geological profile, the quasi-three-dimensional finite element model of the site is constructed. Analyze the creep response of the slope in the reservoir area by trial calculation. Analyze differences in mechanical state of slopes under different trial conditions and the related viscoelastic and plastic parameters of the soft interlayer are calibrated.3） Comparative analysis of site stability factors and engineering measures. The influence of underground water level which is caused by the rise and fall of the reservoir water level to the creep deformation of the site is analyzed, and the effect of two kinds of engineering treatment measures, namely, the slope unloading and the heap of the slope foot, is discussed.The simulation results show that the three-dimensional viscoelastoplastic model can be used to characterize the slope creep deformation model, and the trend of the simulated slope deformation is in good agreement with the actual monitoring results. There are significant differences between the two kinds of engineering treatment measures on the influence to the ground creep deformation. However, development of stress nonlinearity of the model and the three-dimensional effect of the site should be introduced in the quantitative description. The results can provide reference for selection of slope treatment measures.
