【作者】 魏松；

【导师】 朱俊高；

【作者基本信息】 河海大学 ， 岩土工程， 2006， 博士

【摘要】 土石坝粗粒料浸水湿化变形,是目前高土石坝设计理论中的关键问题之一,但没有很好解决。本文采用改进的仪器、通过试验和理论分析及数值模拟,对该问题进行了系统深入研究。 基于目前三轴湿化变形试验仪器存在的问题,本文改进了一套可以进行保持应力不变的三轴剪切试验设备。该套设备结合了电子万能试验机和GDS液体压力控制器,同时采用计算机软件进行控制,实现了三轴剪切试验的应力控制、数据自动采集和不同应力路径试验的目的。 利用该仪器对粗粒料湿化变形特性进行了系统的试验研究。通过试验,揭示了湿化变形的基本规律;发现了湿化轴变和湿化体变之间的关系;对湿化后再加载表现出先线性后非线性变形性状从弹塑性理论的角度进行了解释;分析了湿化对抗剪强度的影响,认为湿化后土体峰值抗剪强度指标不随湿化应力水平而变且与饱和态值相等;论述了单双线法的优缺点,建议了“改进的双线法”;提出了“最大湿化应力水平”的概念,利用该概念合理解释了“在较高湿化应力水平下低围压的湿化轴变大于高围压的”的特殊现象;建议了密实粗粒料的“单线法”湿化变形经验公式,并讨论了该公式的适用性。 对湿化变形试验中影响试验结果的时间、停机变形及变形稳定标准进行了深入研究。得到了停机变形、湿化变形随历时变化的基本规律,表明:当达到一定历时后,上述两种变形与历时对数间呈线性关系。同时,停机变形不可忽略,否则,测得的湿化变形可能偏大。结合以上规律提出了达到“稳定变形阶段”时刻作为变形稳定标准,讨论了其合理性,同时建议了三轴湿化试验中停机变形和湿化变形稳定的参照标准。 结合湿化试验进行了粗粒料湿化颗粒破碎试验研究。根据干湿态颗粒破碎试验,得到了颗粒破碎基本规律,建议了归一化的颗粒破碎经验公式;基于颗粒破碎的能量分析,发现了颗粒破碎率与外力塑性功、颗粒破碎能之间近似成幂函数关系,特别是颗粒破碎能占外力塑性功的比例几乎不随应力状态而变;通过湿化颗粒破碎试验,揭示了湿化颗粒破碎基本规律,发现了其与湿化变形间有较好的相关性,从能量的角度指出了外力塑性功为湿化颗粒破碎提供了能量,特别地从颗粒破碎角度剖析了湿化变形基本规律。 基于试验和椭圆—抛物双屈服面弹塑性模型,提出了湿化变形塑性模型。该模型依据经典塑性理论,能够明确指定复杂应力状态下湿化变形的各分量。进一步验证表明,其能够很好的反映密实粗粒料湿化变形特性。 通过对土石坝湿化变形有限元方法的分析,指出了该方法中存在的问题并进行了改进。结合糯扎渡土石坝工程实例,设计了考虑不同因素的计算方案,结果表明:文中指出存在的问题和所做改进是正确的;本文提出的湿化变形塑性模型能够很好的模拟土石坝蓄水湿化变形,符合工程实际情况,这进一步验证了本文湿化塑性模型的合理性。最更多还原

【Abstract】 The wetting deformation of coarse-grained material is a key problem in design of high earth rockfill dam, but it is not solved well so far. In this thesis the wetting deformation is studied systematically and intensively by wetting deformation test, analysis of test results and numerical simulation.A new apparatus for holding constant stress state is improved for triaxial wetting test. It includes electronic universal testing machine and GDS water pressure controller. It is controlled by a computer, and automatic recording data and different stress path test may be achieved.Using the new apparatus, a large number of tests on coarse-grained material are carried out, and the behaviour of wetting deformation is studied. The relationship between wetting axial strain and wetting volume strain is investigated. The deformation behaviour of wetted soil while loading may be explained on the basis of the elastic-plastic theory. The effect of wetting to the soil shear strength is investigated, and it is found that the shear strength of soil after wetting would not vary with different wetting stress level and they are equal to the shear strength of soil in saturated state. The advantages and limitations of single & double line methods are discussed, and an improved double-line method is suggested. The concept of the maximum wetting stress level is advanced, and using this concept the phenomenon that wetting axial strain under low cell pressure is larger than that under high pressure at high wetting stress level is explained reasonably. In the thesis, the empirical formulas for single-line method for dense coarse-grained material are presented, and its adaptability is discussed.The effect factors for wetting deformation in wetting test, such as time, pause-shear deformation and the deformation steady criterion, are investigated. The relationships of pause-shear deformation vs. time and wetting deformation vs. time are achieved. They demonstrate that the relationships are linear between the deformations above and the logarithm of time after a certain moment. The test results indicate that the pause-shear deformation should be not ignored. The wetting should starts until the pause-shear deformation ceases, otherwise the error for wetting deformation is high. It advances that the moment, at which the steady deformation phase reaches, may be regarded as the criterion for deformation. The rationality of this criterion is discussed later, and at the same time a reference criterion for pause-shear deformation and wetting deformation is suggested.The grain breakage due to wetting is studied by the wetting test. According to the grain breakage test of sample under dry and saturated state, the behavior of particle breakage is revealed. A normalized formula for grain breakage is proposed. Based on the energy analysis, it is found that the power-law function relations exist between grain breakage and external force plastic work against grain breakage energy, and the ratio of grain breakage energy to external force plastic work does not vary with the stress state. It is found that the wetting grain breakage has close correlation to the wetting deformation. It is pointed out that the plastic work of external force provides the energy for wetting grain breakage from the theory of energy. The behavior of wetting deformation is analysed from the point of view of the wetting grain breakage.Based on test results and couple yield surfaces constitutive model, a wetting plastic model is presented. It bases on the classical plastic theory, and the components of wetting deformation under complicated stress state may be determined clearly. It is validated that this model can reflect the wetting deformation behavior of dense coarse-grained material well.Based on analyses to FEM method of wetting deformation in earth rockfill dam, the problems are pointed out, and an improved method to simulate wetting deformation is proposed. With the numerical simulation for Nuo-Zhadu Earth Rochfill Dam, the wetting deformation is investigated. The results show that the problems pointed out in the thesis are exist, and the improved method is reasonable. The wetting deformation tendency from the wetting plastic model presented in the thesis agree well with that observed of the constructed earth dam during the water impounding. This verifies further that the presented wetting plastic model is reasonable. At the last part, the effects of wetting deformation to earth rockfill dam deformation and arch action in core are evaluated.更多还原